Release v41.2

Closes #256

app/.idea/.idea.DiscordHistoryTracker/.idea/avalonia.xml

@@ -9,15 +9,15 @@
         <entry key="Desktop/Dialogs/Progress/ProgressDialog.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Dialogs/TextBox/TextBoxDialog.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/AboutWindow.axaml" value="Desktop/Desktop.csproj" />
-        <entry key="Desktop/Main/Controls/AttachmentFilterPanel.axaml" value="Desktop/Desktop.csproj" />
+        <entry key="Desktop/Main/Controls/DownloadItemFilterPanel.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Controls/MessageFilterPanel.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Controls/ServerConfigurationPanel.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Controls/StatusBar.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/MainWindow.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Pages/AdvancedPage.axaml" value="Desktop/Desktop.csproj" />
-        <entry key="Desktop/Main/Pages/AttachmentsPage.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Pages/DatabasePage.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Pages/DebugPage.axaml" value="Desktop/Desktop.csproj" />
+        <entry key="Desktop/Main/Pages/DownloadsPage.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Pages/TrackingPage.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Pages/ViewerPage.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Screens/MainContentScreen.axaml" value="Desktop/Desktop.csproj" />
@@ -25,4 +25,4 @@
       </map>
     </option>
   </component>
-</project>
+</project>

app/Desktop/Arguments.cs

@@ -15,6 +15,7 @@ sealed class Arguments {
 	public string? DatabaseFile { get; }
 	public ushort? ServerPort { get; }
 	public string? ServerToken { get; }
+	public byte? ConcurrentDownloads { get; }
 
 	public Arguments(IReadOnlyList<string> args) {
 		for (int i = FirstArgument; i < args.Count; i++) {
@@ -50,11 +51,11 @@ sealed class Arguments {
 					continue;
 
 				case "-port": {
-					if (ushort.TryParse(value, out var port)) {
-						ServerPort = port;
+					if (!ushort.TryParse(value, out var port)) {
+						Log.Warn("Invalid port number: " + value);
 					}
 					else {
-						Log.Warn("Invalid port number: " + value);
+						ServerPort = port;
 					}
 
 					continue;
@@ -63,6 +64,20 @@ sealed class Arguments {
 				case "-token":
 					ServerToken = value;
 					continue;
+				
+				case "-concurrentdownloads":
+					if (!ulong.TryParse(value, out var concurrentDownloads) || concurrentDownloads == 0) {
+						Log.Warn("Invalid concurrent downloads count: " + value);
+					}
+					else if (concurrentDownloads > 10) {
+						Log.Warn("Limiting concurrent downloads to 10");
+						ConcurrentDownloads = 10;
+					}
+					else {
+						ConcurrentDownloads = (byte) concurrentDownloads;
+					}
+					
+					continue;
 
 				default:
 					Log.Warn("Unknown command line argument: " + key);

app/Desktop/Common/BytesValueConverter.cs

@@ -29,7 +29,7 @@ sealed class BytesValueConverter : IValueConverter {
 
 	private const int Scale = 1000;
 
-	private static string Convert(ulong size) {
+	public static string Convert(ulong size) {
 		int power = size == 0L ? 0 : (int) Math.Log(size, Scale);
 		int unit = power >= Units.Length ? Units.Length - 1 : power;
 		return Units[unit].Format(unit == 0 ? size : size / Math.Pow(Scale, unit));

app/Desktop/Common/DatabaseGui.cs

@@ -9,7 +9,7 @@ using DHT.Desktop.Dialogs.Message;
 using DHT.Server.Database;
 using DHT.Server.Database.Exceptions;
 using DHT.Server.Database.Sqlite;
-using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Database.Sqlite.Schema;
 using DHT.Utils.Logging;
 
 namespace DHT.Desktop.Common;

app/Desktop/Desktop.csproj

@@ -32,10 +32,6 @@
   
   <ItemGroup>
     <Compile Include="..\Version.cs" Link="Version.cs" />
-    <Compile Update="Dialogs\TextBox\TextBoxDialog.axaml.cs">
-      <DependentUpon>CheckBoxDialog.axaml</DependentUpon>
-      <SubType>Code</SubType>
-    </Compile>
   </ItemGroup>
   
   <ItemGroup>

app/Desktop/Main/Controls/DownloadItemFilterPanel.axaml

@@ -4,11 +4,11 @@
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
              xmlns:controls="clr-namespace:DHT.Desktop.Main.Controls"
              mc:Ignorable="d"
-             x:Class="DHT.Desktop.Main.Controls.AttachmentFilterPanel"
-             x:DataType="controls:AttachmentFilterPanelModel">
+             x:Class="DHT.Desktop.Main.Controls.DownloadItemFilterPanel"
+             x:DataType="controls:DownloadItemFilterPanelModel">
 
     <Design.DataContext>
-        <controls:AttachmentFilterPanelModel />
+        <controls:DownloadItemFilterPanelModel />
     </Design.DataContext>
 
     <UserControl.Styles>

app/Desktop/Main/Controls/DownloadItemFilterPanel.axaml.cs

@@ -4,8 +4,8 @@ using Avalonia.Controls;
 namespace DHT.Desktop.Main.Controls;
 
 [SuppressMessage("ReSharper", "MemberCanBeInternal")]
-public sealed partial class AttachmentFilterPanel : UserControl {
-	public AttachmentFilterPanel() {
+public sealed partial class DownloadItemFilterPanel : UserControl {
+	public DownloadItemFilterPanel() {
 		InitializeComponent();
 	}
 }

app/Desktop/Main/Controls/DownloadItemFilterPanelModel.cs

@@ -12,7 +12,7 @@ using DHT.Utils.Tasks;
 
 namespace DHT.Desktop.Main.Controls;
 
-sealed partial class AttachmentFilterPanelModel : ObservableObject, IDisposable {
+sealed partial class DownloadItemFilterPanelModel : ObservableObject, IDisposable {
 	public sealed record Unit(string Name, uint Scale);
 
 	private static readonly Unit[] AllUnits = [
@@ -43,21 +43,21 @@ sealed partial class AttachmentFilterPanelModel : ObservableObject, IDisposable
 	private readonly State state;
 	private readonly string verb;
 
-	private readonly RestartableTask<long> matchingAttachmentCountTask;
-	private long? matchingAttachmentCount;
+	private readonly RestartableTask<long> downloadItemCountTask;
+	private long? matchingItemCount;
 	
-	private readonly IDisposable attachmentCountSubscription;
-	private long? totalAttachmentCount;
+	private readonly IDisposable downloadItemCountSubscription;
+	private long? totalItemCount;
 
 	[Obsolete("Designer")]
-	public AttachmentFilterPanelModel() : this(State.Dummy) {}
+	public DownloadItemFilterPanelModel() : this(State.Dummy) {}
 
-	public AttachmentFilterPanelModel(State state, string verb = "Matches") {
+	public DownloadItemFilterPanelModel(State state, string verb = "Matches") {
 		this.state = state;
 		this.verb = verb;
 
-		this.matchingAttachmentCountTask = new RestartableTask<long>(SetAttachmentCounts, TaskScheduler.FromCurrentSynchronizationContext());
-		this.attachmentCountSubscription = state.Db.Attachments.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnAttachmentCountChanged);
+		this.downloadItemCountTask = new RestartableTask<long>(SetMatchingCount, TaskScheduler.FromCurrentSynchronizationContext());
+		this.downloadItemCountSubscription = state.Db.Downloads.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnDownloadItemCountChanged);
 
 		UpdateFilterStatistics();
 
@@ -65,7 +65,8 @@ sealed partial class AttachmentFilterPanelModel : ObservableObject, IDisposable
 	}
 
 	public void Dispose() {
-		attachmentCountSubscription.Dispose();
+		downloadItemCountTask.Cancel();
+		downloadItemCountSubscription.Dispose();
 	}
 
 	private void OnPropertyChanged(object? sender, PropertyChangedEventArgs e) {
@@ -74,8 +75,8 @@ sealed partial class AttachmentFilterPanelModel : ObservableObject, IDisposable
 		}
 	}
 	
-	private void OnAttachmentCountChanged(long newAttachmentCount) {
-		totalAttachmentCount = newAttachmentCount;
+	private void OnDownloadItemCountChanged(long newItemCount) {
+		totalItemCount = newItemCount;
 		UpdateFilterStatistics();
 	}
 	
@@ -83,32 +84,32 @@ sealed partial class AttachmentFilterPanelModel : ObservableObject, IDisposable
 	private void UpdateFilterStatistics() {
 		var filter = CreateFilter();
 		if (filter.IsEmpty) {
-			matchingAttachmentCountTask.Cancel();
-			matchingAttachmentCount = totalAttachmentCount;
+			downloadItemCountTask.Cancel();
+			matchingItemCount = totalItemCount;
 			UpdateFilterStatisticsText();
 		}
 		else {
-			matchingAttachmentCount = null;
+			matchingItemCount = null;
 			UpdateFilterStatisticsText();
-			matchingAttachmentCountTask.Restart(cancellationToken => state.Db.Attachments.Count(filter, cancellationToken));
+			downloadItemCountTask.Restart(cancellationToken => state.Db.Downloads.Count(filter, cancellationToken));
 		}
 	}
 
-	private void SetAttachmentCounts(long matchingAttachmentCount) {
-		this.matchingAttachmentCount = matchingAttachmentCount;
+	private void SetMatchingCount(long matchingAttachmentCount) {
+		this.matchingItemCount = matchingAttachmentCount;
 		UpdateFilterStatisticsText();
 	}
 
 	private void UpdateFilterStatisticsText() {
-		var matchingAttachmentCountStr = matchingAttachmentCount?.Format() ?? "(...)";
-		var totalAttachmentCountStr = totalAttachmentCount?.Format() ?? "(...)";
+		var matchingItemCountStr = matchingItemCount?.Format() ?? "(...)";
+		var totalItemCountStr = totalItemCount?.Format() ?? "(...)";
 
-		FilterStatisticsText = verb + " " + matchingAttachmentCountStr + " out of " + totalAttachmentCountStr + " attachment" + (totalAttachmentCount is null or 1 ? "." : "s.");
+		FilterStatisticsText = verb + " " + matchingItemCountStr + " out of " + totalItemCountStr + " file" + (totalItemCount is null or 1 ? "." : "s.");
 		OnPropertyChanged(nameof(FilterStatisticsText));
 	}
 
-	public AttachmentFilter CreateFilter() {
-		AttachmentFilter filter = new ();
+	public DownloadItemFilter CreateFilter() {
+		DownloadItemFilter filter = new ();
 
 		if (LimitSize) {
 			try {

app/Desktop/Main/MainWindowModel.cs

@@ -30,6 +30,7 @@ sealed partial class MainWindowModel : ObservableObject, IAsyncDisposable {
 	private MainContentScreenModel? mainContentScreenModel;
 
 	private readonly Window window;
+	private readonly int? concurrentDownloads;
 
 	private State? state;
 
@@ -73,6 +74,8 @@ sealed partial class MainWindowModel : ObservableObject, IAsyncDisposable {
 		if (args.ServerToken != null) {
 			ServerConfiguration.Token = args.ServerToken;
 		}
+		
+		concurrentDownloads = args.ConcurrentDownloads;
 	}
 
 	private async void OnDatabaseSelected(object? sender, IDatabaseFile db) {
@@ -80,7 +83,7 @@ sealed partial class MainWindowModel : ObservableObject, IAsyncDisposable {
 		
 		await DisposeState();
 		
-		state = new State(db);
+		state = new State(db, concurrentDownloads);
 
 		try {
 			await state.Server.Start(ServerConfiguration.Port, ServerConfiguration.Token);

app/Desktop/Main/Pages/AttachmentsPageModel.cs

@@ -1,244 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.ReactiveUI;
-using CommunityToolkit.Mvvm.ComponentModel;
-using DHT.Desktop.Common;
-using DHT.Desktop.Main.Controls;
-using DHT.Server;
-using DHT.Server.Data;
-using DHT.Server.Data.Aggregations;
-using DHT.Server.Data.Filters;
-using DHT.Utils.Logging;
-using DHT.Utils.Tasks;
-
-namespace DHT.Desktop.Main.Pages;
-
-sealed partial class AttachmentsPageModel : ObservableObject, IDisposable {
-	private static readonly Log Log = Log.ForType<AttachmentsPageModel>();
-
-	private static readonly DownloadItemFilter EnqueuedItemFilter = new () {
-		IncludeStatuses = new HashSet<DownloadStatus> {
-			DownloadStatus.Enqueued,
-			DownloadStatus.Downloading
-		}
-	};
-
-	[ObservableProperty(Setter = Access.Private)]
-	private bool isToggleDownloadButtonEnabled = true;
-
-	public string ToggleDownloadButtonText => IsDownloading ? "Stop Downloading" : "Start Downloading";
-
-	[ObservableProperty(Setter = Access.Private)]
-	[NotifyPropertyChangedFor(nameof(IsRetryFailedOnDownloadsButtonEnabled))]
-	private bool isRetryingFailedDownloads = false;
-
-	[ObservableProperty(Setter = Access.Private)]
-	[NotifyPropertyChangedFor(nameof(IsRetryFailedOnDownloadsButtonEnabled))]
-	private bool hasFailedDownloads;
-
-	public bool IsRetryFailedOnDownloadsButtonEnabled => !IsRetryingFailedDownloads && hasFailedDownloads;
-
-	[ObservableProperty(Setter = Access.Private)]
-	private string downloadMessage = "";
-
-	public double DownloadProgress => totalItemsToDownloadCount is null or 0 ? 0.0 : 100.0 * doneItemsCount / totalItemsToDownloadCount.Value;
-
-	public AttachmentFilterPanelModel FilterModel { get; }
-
-	private readonly StatisticsRow statisticsEnqueued = new ("Enqueued");
-	private readonly StatisticsRow statisticsDownloaded = new ("Downloaded");
-	private readonly StatisticsRow statisticsFailed = new ("Failed");
-	private readonly StatisticsRow statisticsSkipped = new ("Skipped");
-
-	public ObservableCollection<StatisticsRow> StatisticsRows { get; }
-
-	public bool IsDownloading => state.Downloader.IsDownloading;
-
-	private readonly State state;
-	private readonly ThrottledTask<int> enqueueDownloadItemsTask;
-	private readonly ThrottledTask<DownloadStatusStatistics> downloadStatisticsTask;
-
-	private readonly IDisposable attachmentCountSubscription;
-	private readonly IDisposable downloadCountSubscription;
-
-	private IDisposable? finishedItemsSubscription;
-	private int doneItemsCount;
-	private int totalEnqueuedItemCount;
-	private int? totalItemsToDownloadCount;
-
-	public AttachmentsPageModel() : this(State.Dummy) {}
-
-	public AttachmentsPageModel(State state) {
-		this.state = state;
-
-		FilterModel = new AttachmentFilterPanelModel(state);
-		
-		StatisticsRows = [
-			statisticsEnqueued,
-			statisticsDownloaded,
-			statisticsFailed,
-			statisticsSkipped
-		];
-
-		enqueueDownloadItemsTask = new ThrottledTask<int>(OnItemsEnqueued, TaskScheduler.FromCurrentSynchronizationContext());
-		downloadStatisticsTask = new ThrottledTask<DownloadStatusStatistics>(UpdateStatistics, TaskScheduler.FromCurrentSynchronizationContext());
-
-		attachmentCountSubscription = state.Db.Attachments.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnAttachmentCountChanged);
-		downloadCountSubscription = state.Db.Downloads.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnDownloadCountChanged);
-
-		RecomputeDownloadStatistics();
-	}
-
-	public void Dispose() {
-		attachmentCountSubscription.Dispose();
-		downloadCountSubscription.Dispose();
-		finishedItemsSubscription?.Dispose();
-
-		enqueueDownloadItemsTask.Dispose();
-		downloadStatisticsTask.Dispose();
-
-		FilterModel.Dispose();
-	}
-
-	private void OnAttachmentCountChanged(long newAttachmentCount) {
-		if (IsDownloading) {
-			EnqueueDownloadItemsLater();
-		}
-		else {
-			RecomputeDownloadStatistics();
-		}
-	}
-
-	private void OnDownloadCountChanged(long newDownloadCount) {
-		RecomputeDownloadStatistics();
-	}
-
-	private async Task EnqueueDownloadItems() {
-		OnItemsEnqueued(await state.Db.Downloads.EnqueueDownloadItems(CreateAttachmentFilter()));
-	}
-
-	private void EnqueueDownloadItemsLater() {
-		var filter = CreateAttachmentFilter();
-		enqueueDownloadItemsTask.Post(cancellationToken => state.Db.Downloads.EnqueueDownloadItems(filter, cancellationToken));
-	}
-
-	private void OnItemsEnqueued(int itemCount) {
-		totalEnqueuedItemCount += itemCount;
-		totalItemsToDownloadCount = totalEnqueuedItemCount;
-		UpdateDownloadMessage();
-		RecomputeDownloadStatistics();
-	}
-
-	private AttachmentFilter CreateAttachmentFilter() {
-		var filter = FilterModel.CreateFilter();
-		filter.DownloadItemRule = AttachmentFilter.DownloadItemRules.OnlyNotPresent;
-		return filter;
-	}
-
-	public async Task OnClickToggleDownload() {
-		IsToggleDownloadButtonEnabled = false;
-
-		if (IsDownloading) {
-			await state.Downloader.Stop();
-
-			finishedItemsSubscription?.Dispose();
-			finishedItemsSubscription = null;
-
-			RecomputeDownloadStatistics();
-
-			await state.Db.Downloads.RemoveDownloadItems(EnqueuedItemFilter, FilterRemovalMode.RemoveMatching);
-
-			doneItemsCount = 0;
-			totalEnqueuedItemCount = 0;
-			totalItemsToDownloadCount = null;
-			UpdateDownloadMessage();
-		}
-		else {
-			var finishedItems = await state.Downloader.Start();
-
-			finishedItemsSubscription = finishedItems.Select(static _ => true)
-			                                         .Buffer(TimeSpan.FromMilliseconds(100))
-			                                         .Select(static items => items.Count)
-			                                         .Where(static items => items > 0)
-			                                         .ObserveOn(AvaloniaScheduler.Instance)
-			                                         .Subscribe(OnItemsFinished);
-
-			await EnqueueDownloadItems();
-		}
-
-		OnPropertyChanged(nameof(ToggleDownloadButtonText));
-		OnPropertyChanged(nameof(IsDownloading));
-		IsToggleDownloadButtonEnabled = true;
-	}
-
-	private void OnItemsFinished(int finishedItemCount) {
-		doneItemsCount += finishedItemCount;
-		UpdateDownloadMessage();
-	}
-
-	public async Task OnClickRetryFailedDownloads() {
-		IsRetryingFailedDownloads = true;
-
-		try {
-			var allExceptFailedFilter = new DownloadItemFilter {
-				IncludeStatuses = new HashSet<DownloadStatus> {
-					DownloadStatus.Enqueued,
-					DownloadStatus.Downloading,
-					DownloadStatus.Success
-				}
-			};
-
-			await state.Db.Downloads.RemoveDownloadItems(allExceptFailedFilter, FilterRemovalMode.KeepMatching);
-
-			if (IsDownloading) {
-				await EnqueueDownloadItems();
-			}
-		} catch (Exception e) {
-			Log.Error(e);
-		} finally {
-			IsRetryingFailedDownloads = false;
-		}
-	}
-
-	private void RecomputeDownloadStatistics() {
-		downloadStatisticsTask.Post(state.Db.Downloads.GetStatistics);
-	}
-
-	private void UpdateStatistics(DownloadStatusStatistics statusStatistics) {
-		statisticsEnqueued.Items = statusStatistics.EnqueuedCount;
-		statisticsEnqueued.Size = statusStatistics.EnqueuedSize;
-
-		statisticsDownloaded.Items = statusStatistics.SuccessfulCount;
-		statisticsDownloaded.Size = statusStatistics.SuccessfulSize;
-
-		statisticsFailed.Items = statusStatistics.FailedCount;
-		statisticsFailed.Size = statusStatistics.FailedSize;
-
-		statisticsSkipped.Items = statusStatistics.SkippedCount;
-		statisticsSkipped.Size = statusStatistics.SkippedSize;
-
-		hasFailedDownloads = statusStatistics.FailedCount > 0;
-
-		UpdateDownloadMessage();
-	}
-
-	private void UpdateDownloadMessage() {
-		DownloadMessage = IsDownloading ? doneItemsCount.Format() + " / " + (totalItemsToDownloadCount?.Format() ?? "?") : "";
-
-		OnPropertyChanged(nameof(DownloadProgress));
-	}
-
-	[ObservableObject]
-	public sealed partial class StatisticsRow(string state) {
-		public string State { get; } = state;
-
-		[ObservableProperty]
-		private int items;
-
-		[ObservableProperty]
-		private ulong? size;
-	}
-}

app/Desktop/Main/Pages/DatabasePageModel.cs

@@ -18,7 +18,7 @@ using DHT.Server;
 using DHT.Server.Data;
 using DHT.Server.Database;
 using DHT.Server.Database.Import;
-using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Database.Sqlite.Schema;
 using DHT.Utils.Logging;
 
 namespace DHT.Desktop.Main.Pages;

app/Desktop/Main/Pages/DebugPageModel.cs

@@ -10,164 +10,164 @@ using DHT.Server;
 using DHT.Server.Data;
 using DHT.Server.Service;
 
-namespace DHT.Desktop.Main.Pages {
-	sealed class DebugPageModel {
-		public string GenerateChannels { get; set; } = "0";
-		public string GenerateUsers { get; set; } = "0";
-		public string GenerateMessages { get; set; } = "0";
+namespace DHT.Desktop.Main.Pages;
 
-		private readonly Window window;
-		private readonly State state;
+sealed class DebugPageModel {
+	public string GenerateChannels { get; set; } = "0";
+	public string GenerateUsers { get; set; } = "0";
+	public string GenerateMessages { get; set; } = "0";
 
-		[Obsolete("Designer")]
-		public DebugPageModel() : this(null!, State.Dummy) {}
+	private readonly Window window;
+	private readonly State state;
 
-		public DebugPageModel(Window window, State state) {
-			this.window = window;
-			this.state = state;
+	[Obsolete("Designer")]
+	public DebugPageModel() : this(null!, State.Dummy) {}
+
+	public DebugPageModel(Window window, State state) {
+		this.window = window;
+		this.state = state;
+	}
+
+	public async void OnClickAddRandomDataToDatabase() {
+		if (!int.TryParse(GenerateChannels, out int channels) || channels < 1) {
+			await Dialog.ShowOk(window, "Generate Random Data", "Amount of channels must be at least 1!");
+			return;
 		}
 
-		public async void OnClickAddRandomDataToDatabase() {
-			if (!int.TryParse(GenerateChannels, out int channels) || channels < 1) {
-				await Dialog.ShowOk(window, "Generate Random Data", "Amount of channels must be at least 1!");
-				return;
-			}
-
-			if (!int.TryParse(GenerateUsers, out int users) || users < 1) {
-				await Dialog.ShowOk(window, "Generate Random Data", "Amount of users must be at least 1!");
-				return;
-			}
-
-			if (!int.TryParse(GenerateMessages, out int messages) || messages < 1) {
-				await Dialog.ShowOk(window, "Generate Random Data", "Amount of messages must be at least 1!");
-				return;
-			}
-
-			await ProgressDialog.Show(window, "Generating Random Data", async (_, callback) => await GenerateRandomData(channels, users, messages, callback));
+		if (!int.TryParse(GenerateUsers, out int users) || users < 1) {
+			await Dialog.ShowOk(window, "Generate Random Data", "Amount of users must be at least 1!");
+			return;
 		}
 
-		private const int BatchSize = 500;
+		if (!int.TryParse(GenerateMessages, out int messages) || messages < 1) {
+			await Dialog.ShowOk(window, "Generate Random Data", "Amount of messages must be at least 1!");
+			return;
+		}
 
-		private async Task GenerateRandomData(int channelCount, int userCount, int messageCount, IProgressCallback callback) {
-			int batchCount = (messageCount + BatchSize - 1) / BatchSize;
-			await callback.Update("Adding messages in batches of " + BatchSize, 0, batchCount);
+		await ProgressDialog.Show(window, "Generating Random Data", async (_, callback) => await GenerateRandomData(channels, users, messages, callback));
+	}
 
-			var rand = new Random();
-			var server = new DHT.Server.Data.Server {
-				Id = RandomId(rand),
-				Name = RandomName("s"),
-				Type = ServerType.Server,
-			};
+	private const int BatchSize = 500;
 
-			var channels = Enumerable.Range(0, channelCount).Select(i => new Channel {
-				Id = RandomId(rand),
-				Server = server.Id,
-				Name = RandomName("c"),
-				ParentId = null,
-				Position = i,
-				Topic = RandomText(rand, 10),
-				Nsfw = rand.Next(4) == 0,
+	private async Task GenerateRandomData(int channelCount, int userCount, int messageCount, IProgressCallback callback) {
+		int batchCount = (messageCount + BatchSize - 1) / BatchSize;
+		await callback.Update("Adding messages in batches of " + BatchSize, 0, batchCount);
+
+		var rand = new Random();
+		var server = new DHT.Server.Data.Server {
+			Id = RandomId(rand),
+			Name = RandomName("s"),
+			Type = ServerType.Server,
+		};
+
+		var channels = Enumerable.Range(0, channelCount).Select(i => new Channel {
+			Id = RandomId(rand),
+			Server = server.Id,
+			Name = RandomName("c"),
+			ParentId = null,
+			Position = i,
+			Topic = RandomText(rand, 10),
+			Nsfw = rand.Next(4) == 0,
+		}).ToArray();
+
+		var users = Enumerable.Range(0, userCount).Select(_ => new User {
+			Id = RandomId(rand),
+			Name = RandomName("u"),
+			AvatarUrl = null,
+			Discriminator = rand.Next(0, 9999).ToString(),
+		}).ToArray();
+
+		await state.Db.Users.Add(users);
+		await state.Db.Servers.Add([server]);
+		await state.Db.Channels.Add(channels);
+
+		var now = DateTimeOffset.Now;
+		int batchIndex = 0;
+
+		while (messageCount > 0) {
+			int hourOffset = batchIndex;
+
+			var messages = Enumerable.Range(0, Math.Min(messageCount, BatchSize)).Select(i => {
+				DateTimeOffset time = now.AddHours(hourOffset).AddMinutes(i * 60.0 / BatchSize);
+				DateTimeOffset? edit = rand.Next(100) == 0 ? time.AddSeconds(rand.Next(1, 60)) : null;
+
+				var timeMillis = time.ToUnixTimeMilliseconds();
+				var editMillis = edit?.ToUnixTimeMilliseconds();
+
+				return new Message {
+					Id = (ulong) timeMillis,
+					Sender = RandomBiasedIndex(rand, users).Id,
+					Channel = RandomBiasedIndex(rand, channels).Id,
+					Text = RandomText(rand, 100),
+					Timestamp = timeMillis,
+					EditTimestamp = editMillis,
+					RepliedToId = null,
+					Attachments = ImmutableList<Attachment>.Empty,
+					Embeds = ImmutableList<Embed>.Empty,
+					Reactions = ImmutableList<Reaction>.Empty,
+				};
 			}).ToArray();
 
-			var users = Enumerable.Range(0, userCount).Select(_ => new User {
-				Id = RandomId(rand),
-				Name = RandomName("u"),
-				AvatarUrl = null,
-				Discriminator = rand.Next(0, 9999).ToString(),
-			}).ToArray();
+			await state.Db.Messages.Add(messages);
 
-			await state.Db.Users.Add(users);
-			await state.Db.Servers.Add([server]);
-			await state.Db.Channels.Add(channels);
-
-			var now = DateTimeOffset.Now;
-			int batchIndex = 0;
-
-			while (messageCount > 0) {
-				int hourOffset = batchIndex;
-
-				var messages = Enumerable.Range(0, Math.Min(messageCount, BatchSize)).Select(i => {
-					DateTimeOffset time = now.AddHours(hourOffset).AddMinutes(i * 60.0 / BatchSize);
-					DateTimeOffset? edit = rand.Next(100) == 0 ? time.AddSeconds(rand.Next(1, 60)) : null;
-
-					var timeMillis = time.ToUnixTimeMilliseconds();
-					var editMillis = edit?.ToUnixTimeMilliseconds();
-
-					return new Message {
-						Id = (ulong) timeMillis,
-						Sender = RandomBiasedIndex(rand, users).Id,
-						Channel = RandomBiasedIndex(rand, channels).Id,
-						Text = RandomText(rand, 100),
-						Timestamp = timeMillis,
-						EditTimestamp = editMillis,
-						RepliedToId = null,
-						Attachments = ImmutableList<Attachment>.Empty,
-						Embeds = ImmutableList<Embed>.Empty,
-						Reactions = ImmutableList<Reaction>.Empty,
-					};
-				}).ToArray();
-
-				await state.Db.Messages.Add(messages);
-
-				messageCount -= BatchSize;
-				await callback.Update("Adding messages in batches of " + BatchSize, ++batchIndex, batchCount);
-			}
+			messageCount -= BatchSize;
+			await callback.Update("Adding messages in batches of " + BatchSize, ++batchIndex, batchCount);
 		}
+	}
 
-		private static ulong RandomId(Random rand) {
-			ulong h = unchecked((ulong) rand.Next());
-			ulong l = unchecked((ulong) rand.Next());
-			return (h << 32) | l;
-		}
+	private static ulong RandomId(Random rand) {
+		ulong h = unchecked((ulong) rand.Next());
+		ulong l = unchecked((ulong) rand.Next());
+		return (h << 32) | l;
+	}
 
-		private static string RandomName(string prefix) {
-			return prefix + "-" + ServerUtils.GenerateRandomToken(5);
-		}
+	private static string RandomName(string prefix) {
+		return prefix + "-" + ServerUtils.GenerateRandomToken(5);
+	}
 
-		private static T RandomBiasedIndex<T>(Random rand, T[] options) {
-			return options[(int) Math.Floor(options.Length * rand.NextDouble() * rand.NextDouble())];
-		}
+	private static T RandomBiasedIndex<T>(Random rand, T[] options) {
+		return options[(int) Math.Floor(options.Length * rand.NextDouble() * rand.NextDouble())];
+	}
 
-		private static readonly string[] RandomWords = [
-			"apple", "apricot", "artichoke", "arugula", "asparagus", "avocado",
-			"banana", "bean", "beechnut", "beet", "blackberry", "blackcurrant", "blueberry", "boysenberry", "bramble", "broccoli",
-			"cabbage", "cacao", "cantaloupe", "caper", "carambola", "carrot", "cauliflower", "celery", "chard", "cherry", "chokeberry", "citron", "clementine", "coconut", "corn", "crabapple", "cranberry", "cucumber", "currant",
-			"daikon", "date", "dewberry", "durian",
-			"edamame", "eggplant", "elderberry", "endive",
-			"fig",
-			"garlic", "ginger", "gooseberry", "grape", "grapefruit", "guava",
-			"honeysuckle", "horseradish", "huckleberry",
-			"jackfruit", "jicama",
-			"kale", "kiwi", "kohlrabi", "kumquat",
-			"leek", "lemon", "lentil", "lettuce", "lime",
-			"mandarin", "mango", "mushroom", "myrtle",
-			"nectarine", "nut",
-			"olive", "okra", "onion", "orange",
-			"papaya", "parsnip", "pawpaw", "peach", "pear", "pea", "pepper", "persimmon", "pineapple", "plum", "plantain", "pomegranate", "pomelo", "potato", "prune", "pumpkin",
-			"quandong", "quinoa",
-			"radicchio", "radish", "raisin", "raspberry", "redcurrant", "rhubarb", "rutabaga",
-			"spinach", "strawberry", "squash",
-			"tamarind", "tangerine", "tomatillo", "tomato", "turnip",
-			"vanilla",
-			"watercress", "watermelon",
-			"yam",
-			"zucchini"
-		];
+	private static readonly string[] RandomWords = [
+		"apple", "apricot", "artichoke", "arugula", "asparagus", "avocado",
+		"banana", "bean", "beechnut", "beet", "blackberry", "blackcurrant", "blueberry", "boysenberry", "bramble", "broccoli",
+		"cabbage", "cacao", "cantaloupe", "caper", "carambola", "carrot", "cauliflower", "celery", "chard", "cherry", "chokeberry", "citron", "clementine", "coconut", "corn", "crabapple", "cranberry", "cucumber", "currant",
+		"daikon", "date", "dewberry", "durian",
+		"edamame", "eggplant", "elderberry", "endive",
+		"fig",
+		"garlic", "ginger", "gooseberry", "grape", "grapefruit", "guava",
+		"honeysuckle", "horseradish", "huckleberry",
+		"jackfruit", "jicama",
+		"kale", "kiwi", "kohlrabi", "kumquat",
+		"leek", "lemon", "lentil", "lettuce", "lime",
+		"mandarin", "mango", "mushroom", "myrtle",
+		"nectarine", "nut",
+		"olive", "okra", "onion", "orange",
+		"papaya", "parsnip", "pawpaw", "peach", "pear", "pea", "pepper", "persimmon", "pineapple", "plum", "plantain", "pomegranate", "pomelo", "potato", "prune", "pumpkin",
+		"quandong", "quinoa",
+		"radicchio", "radish", "raisin", "raspberry", "redcurrant", "rhubarb", "rutabaga",
+		"spinach", "strawberry", "squash",
+		"tamarind", "tangerine", "tomatillo", "tomato", "turnip",
+		"vanilla",
+		"watercress", "watermelon",
+		"yam",
+		"zucchini"
+	];
 
-		private static string RandomText(Random rand, int maxWords) {
-			int wordCount = 1 + (int) Math.Floor(maxWords * Math.Pow(rand.NextDouble(), 3));
-			return string.Join(' ', Enumerable.Range(0, wordCount).Select(_ => RandomWords[rand.Next(RandomWords.Length)]));
-		}
+	private static string RandomText(Random rand, int maxWords) {
+		int wordCount = 1 + (int) Math.Floor(maxWords * Math.Pow(rand.NextDouble(), 3));
+		return string.Join(' ', Enumerable.Range(0, wordCount).Select(_ => RandomWords[rand.Next(RandomWords.Length)]));
 	}
 }
 #else
-namespace DHT.Desktop.Main.Pages {
-	sealed class DebugPageModel {
-		public string GenerateChannels { get; set; } = "0";
-		public string GenerateUsers { get; set; } = "0";
-		public string GenerateMessages { get; set; } = "0";
+namespace DHT.Desktop.Main.Pages;
 
-		public void OnClickAddRandomDataToDatabase() {}
-	}
+sealed class DebugPageModel {
+	public string GenerateChannels { get; set; } = "0";
+	public string GenerateUsers { get; set; } = "0";
+	public string GenerateMessages { get; set; } = "0";
+
+	public void OnClickAddRandomDataToDatabase() {}
 }
 #endif

app/Desktop/Main/Pages/DownloadsPage.axaml

@@ -5,11 +5,11 @@
              xmlns:pages="clr-namespace:DHT.Desktop.Main.Pages"
              xmlns:controls="clr-namespace:DHT.Desktop.Main.Controls"
              mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
-             x:Class="DHT.Desktop.Main.Pages.AttachmentsPage"
-             x:DataType="pages:AttachmentsPageModel">
+             x:Class="DHT.Desktop.Main.Pages.DownloadsPage"
+             x:DataType="pages:DownloadsPageModel">
 
     <Design.DataContext>
-        <pages:AttachmentsPageModel />
+        <pages:DownloadsPageModel />
     </Design.DataContext>
 
     <UserControl.Styles>
@@ -31,19 +31,15 @@
     </UserControl.Styles>
 
     <StackPanel Orientation="Vertical" Spacing="20">
-        <DockPanel>
-            <Button Command="{Binding OnClickToggleDownload}" Content="{Binding ToggleDownloadButtonText}" IsEnabled="{Binding IsToggleDownloadButtonEnabled}" DockPanel.Dock="Left" />
-            <TextBlock Text="{Binding DownloadMessage}" MinWidth="100" Margin="10 0 0 0" VerticalAlignment="Center" TextAlignment="Right" DockPanel.Dock="Left" />
-            <ProgressBar Value="{Binding DownloadProgress}" IsVisible="{Binding IsDownloading}" Margin="15 0" VerticalAlignment="Center" DockPanel.Dock="Right" />
-        </DockPanel>
-        <controls:AttachmentFilterPanel DataContext="{Binding FilterModel}" IsEnabled="{Binding !IsDownloading, RelativeSource={RelativeSource AncestorType=pages:AttachmentsPageModel}}" />
+        <Button Command="{Binding OnClickToggleDownload}" Content="{Binding ToggleDownloadButtonText}" IsEnabled="{Binding IsToggleDownloadButtonEnabled}" />
+        <controls:DownloadItemFilterPanel DataContext="{Binding FilterModel}" IsEnabled="{Binding !$parent[UserControl].((pages:DownloadsPageModel)DataContext).IsDownloading}" />
         <StackPanel Orientation="Vertical" Spacing="12">
             <Expander Header="Download Status" IsExpanded="True">
                 <DataGrid ItemsSource="{Binding StatisticsRows}" AutoGenerateColumns="False" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserSortColumns="False" IsReadOnly="True">
                     <DataGrid.Columns>
-                        <DataGridTextColumn Header="State" Binding="{Binding State}" Width="*" />
-                        <DataGridTextColumn Header="Attachments" Binding="{Binding Items, Mode=OneWay, Converter={StaticResource NumberValueConverter}}" Width="*" CellStyleClasses="right" />
-                        <DataGridTextColumn Header="Size" Binding="{Binding Size, Mode=OneWay, Converter={StaticResource BytesValueConverter}}" Width="*" CellStyleClasses="right" />
+                        <DataGridTextColumn Header="State" Binding="{Binding State, Mode=OneWay}" Width="*" />
+                        <DataGridTextColumn Header="Files" Binding="{Binding Items, Mode=OneWay, Converter={StaticResource NumberValueConverter}}" Width="*" CellStyleClasses="right" />
+                        <DataGridTextColumn Header="Size" Binding="{Binding SizeText, Mode=OneWay}" Width="*" CellStyleClasses="right" />
                     </DataGrid.Columns>
                 </DataGrid>
             </Expander>

app/Desktop/Main/Pages/DownloadsPage.axaml.cs

@@ -4,8 +4,8 @@ using Avalonia.Controls;
 namespace DHT.Desktop.Main.Pages;
 
 [SuppressMessage("ReSharper", "MemberCanBeInternal")]
-public sealed partial class AttachmentsPage : UserControl {
-	public AttachmentsPage() {
+public sealed partial class DownloadsPage : UserControl {
+	public DownloadsPage() {
 		InitializeComponent();
 	}
 }

app/Desktop/Main/Pages/DownloadsPageModel.cs

@@ -0,0 +1,186 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Reactive.Linq;
+using System.Threading.Tasks;
+using Avalonia.ReactiveUI;
+using CommunityToolkit.Mvvm.ComponentModel;
+using DHT.Desktop.Common;
+using DHT.Desktop.Main.Controls;
+using DHT.Server;
+using DHT.Server.Data.Aggregations;
+using DHT.Server.Data.Filters;
+using DHT.Server.Download;
+using DHT.Utils.Logging;
+using DHT.Utils.Tasks;
+
+namespace DHT.Desktop.Main.Pages;
+
+sealed partial class DownloadsPageModel : ObservableObject, IDisposable {
+	private static readonly Log Log = Log.ForType<DownloadsPageModel>();
+
+	[ObservableProperty(Setter = Access.Private)]
+	private bool isToggleDownloadButtonEnabled = true;
+
+	public string ToggleDownloadButtonText => IsDownloading ? "Stop Downloading" : "Start Downloading";
+
+	[ObservableProperty(Setter = Access.Private)]
+	[NotifyPropertyChangedFor(nameof(IsRetryFailedOnDownloadsButtonEnabled))]
+	private bool isRetryingFailedDownloads = false;
+
+	[ObservableProperty(Setter = Access.Private)]
+	[NotifyPropertyChangedFor(nameof(IsRetryFailedOnDownloadsButtonEnabled))]
+	private bool hasFailedDownloads;
+
+	public bool IsRetryFailedOnDownloadsButtonEnabled => !IsRetryingFailedDownloads && HasFailedDownloads;
+
+	[ObservableProperty(Setter = Access.Private)]
+	private string downloadMessage = "";
+
+	public DownloadItemFilterPanelModel FilterModel { get; }
+
+	private readonly StatisticsRow statisticsPending = new ("Pending");
+	private readonly StatisticsRow statisticsDownloaded = new ("Downloaded");
+	private readonly StatisticsRow statisticsFailed = new ("Failed");
+	private readonly StatisticsRow statisticsSkipped = new ("Skipped");
+
+	public ObservableCollection<StatisticsRow> StatisticsRows { get; }
+
+	public bool IsDownloading => state.Downloader.IsDownloading;
+
+	private readonly State state;
+	private readonly ThrottledTask<DownloadStatusStatistics> downloadStatisticsTask;
+	private readonly IDisposable downloadItemCountSubscription;
+	
+	private IDisposable? finishedItemsSubscription;
+	private DownloadItemFilter? currentDownloadFilter;
+
+	public DownloadsPageModel() : this(State.Dummy) {}
+
+	public DownloadsPageModel(State state) {
+		this.state = state;
+
+		FilterModel = new DownloadItemFilterPanelModel(state);
+		
+		StatisticsRows = [
+			statisticsPending,
+			statisticsDownloaded,
+			statisticsFailed,
+			statisticsSkipped
+		];
+
+		downloadStatisticsTask = new ThrottledTask<DownloadStatusStatistics>(Log, UpdateStatistics, TaskScheduler.FromCurrentSynchronizationContext());
+		downloadItemCountSubscription = state.Db.Downloads.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnDownloadCountChanged);
+
+		RecomputeDownloadStatistics();
+	}
+
+	public void Dispose() {
+		finishedItemsSubscription?.Dispose();
+		
+		downloadItemCountSubscription.Dispose();
+		downloadStatisticsTask.Dispose();
+
+		FilterModel.Dispose();
+	}
+
+	private void OnDownloadCountChanged(long newDownloadCount) {
+		RecomputeDownloadStatistics();
+	}
+
+	public async Task OnClickToggleDownload() {
+		IsToggleDownloadButtonEnabled = false;
+
+		if (IsDownloading) {
+			await state.Downloader.Stop();
+			await state.Db.Downloads.MoveDownloadingItemsBackToQueue();
+
+			finishedItemsSubscription?.Dispose();
+			finishedItemsSubscription = null;
+			
+			currentDownloadFilter = null;
+		}
+		else {
+			await state.Db.Downloads.MoveDownloadingItemsBackToQueue();
+			
+			var finishedItems = await state.Downloader.Start(currentDownloadFilter = FilterModel.CreateFilter());
+			finishedItemsSubscription = finishedItems.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnItemFinished);
+		}
+
+		RecomputeDownloadStatistics();
+
+		OnPropertyChanged(nameof(ToggleDownloadButtonText));
+		OnPropertyChanged(nameof(IsDownloading));
+		IsToggleDownloadButtonEnabled = true;
+	}
+
+	private void OnItemFinished(DownloadItem item) {
+		RecomputeDownloadStatistics();
+	}
+
+	public async Task OnClickRetryFailedDownloads() {
+		IsRetryingFailedDownloads = true;
+
+		try {
+			await state.Db.Downloads.RetryFailed();
+			RecomputeDownloadStatistics();
+		} catch (Exception e) {
+			Log.Error(e);
+		} finally {
+			IsRetryingFailedDownloads = false;
+		}
+	}
+
+	private void RecomputeDownloadStatistics() {
+		downloadStatisticsTask.Post(cancellationToken => state.Db.Downloads.GetStatistics(currentDownloadFilter ?? new DownloadItemFilter(), cancellationToken));
+	}
+
+	private void UpdateStatistics(DownloadStatusStatistics statusStatistics) {
+		statisticsPending.Items = statusStatistics.PendingCount;
+		statisticsPending.Size = statusStatistics.PendingTotalSize;
+		statisticsPending.HasFilesWithUnknownSize = statusStatistics.PendingWithUnknownSizeCount > 0;
+
+		statisticsDownloaded.Items = statusStatistics.SuccessfulCount;
+		statisticsDownloaded.Size = statusStatistics.SuccessfulTotalSize;
+		statisticsDownloaded.HasFilesWithUnknownSize = statusStatistics.SuccessfulWithUnknownSizeCount > 0;
+
+		statisticsFailed.Items = statusStatistics.FailedCount;
+		statisticsFailed.Size = statusStatistics.FailedTotalSize;
+		statisticsFailed.HasFilesWithUnknownSize = statusStatistics.FailedWithUnknownSizeCount > 0;
+		
+		statisticsSkipped.Items = statusStatistics.SkippedCount;
+		statisticsSkipped.Size = statusStatistics.SkippedTotalSize;
+		statisticsSkipped.HasFilesWithUnknownSize = statusStatistics.SkippedWithUnknownSizeCount > 0;
+
+		HasFailedDownloads = statusStatistics.FailedCount > 0;
+	}
+
+	[ObservableObject]
+	public sealed partial class StatisticsRow(string state) {
+		public string State { get; } = state;
+
+		[ObservableProperty]
+		private int items;
+
+		[ObservableProperty]
+		[NotifyPropertyChangedFor(nameof(SizeText))]
+		private ulong? size;
+		
+		[ObservableProperty]
+		[NotifyPropertyChangedFor(nameof(SizeText))]
+		private bool hasFilesWithUnknownSize;
+
+		public string SizeText {
+			get {
+				if (size == null) {
+					return "-";
+				}
+				else if (hasFilesWithUnknownSize) {
+					return "\u2265 " + BytesValueConverter.Convert(size.Value);
+				}
+				else {
+					return BytesValueConverter.Convert(size.Value);
+				}
+			}
+		}
+	}
+}

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -18,7 +18,6 @@ using DHT.Desktop.Server;
 using DHT.Server;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database.Export;
-using DHT.Server.Database.Export.Strategy;
 using static DHT.Desktop.Program;
 
 namespace DHT.Desktop.Main.Pages;
@@ -63,9 +62,13 @@ sealed partial class ViewerPageModel : ObservableObject, IDisposable {
 	public async void OnClickOpenViewer() {
 		try {
 			var fullPath = await PrepareTemporaryViewerFile();
-			var strategy = new LiveViewerExportStrategy(ServerConfiguration.Port, ServerConfiguration.Token);
+			
+			string jsConstants = $"""
+			                      window.DHT_SERVER_URL = "{HttpUtility.JavaScriptStringEncode("http://127.0.0.1:" + ServerConfiguration.Port)}";
+			                      window.DHT_SERVER_TOKEN = "{HttpUtility.JavaScriptStringEncode(ServerConfiguration.Token)}";
+			                      """;
 
-			await ProgressDialog.ShowIndeterminate(window, "Open Viewer", "Creating viewer...", _ => Task.Run(() => WriteViewerFile(fullPath, strategy)));
+			await ProgressDialog.ShowIndeterminate(window, "Open Viewer", "Creating viewer...", _ => Task.Run(() => WriteViewerFile(fullPath, jsConstants)));
 			
 			Process.Start(new ProcessStartInfo(fullPath) {
 				UseShellExecute = true
@@ -109,17 +112,18 @@ sealed partial class ViewerPageModel : ObservableObject, IDisposable {
 		}
 
 		try {
-			await ProgressDialog.ShowIndeterminate(window, "Save Viewer", "Creating viewer...", _ => Task.Run(() => WriteViewerFile(path, StandaloneViewerExportStrategy.Instance)));
+			await ProgressDialog.ShowIndeterminate(window, "Save Viewer", "Creating viewer...", _ => Task.Run(() => WriteViewerFile(path, string.Empty)));
 		} catch (Exception e) {
 			await Dialog.ShowOk(window, "Save Viewer", "Could not create or save viewer: " + e.Message);
 		}
 	}
 
-	private async Task WriteViewerFile(string path, IViewerExportStrategy strategy) {
+	private async Task WriteViewerFile(string path, string jsConstants) {
 		const string ArchiveTag = "/*[ARCHIVE]*/";
 
 		string indexFile = await Resources.ReadTextAsync("Viewer/index.html");
-		string viewerTemplate = indexFile.Replace("/*[JS]*/", await Resources.ReadJoinedAsync("Viewer/scripts/", '\n'))
+		string viewerTemplate = indexFile.Replace("/*[CONSTANTS]*/", jsConstants)
+		                                 .Replace("/*[JS]*/", await Resources.ReadJoinedAsync("Viewer/scripts/", '\n'))
 		                                 .Replace("/*[CSS]*/", await Resources.ReadJoinedAsync("Viewer/styles/", '\n'));
 
 		int viewerArchiveTagStart = viewerTemplate.IndexOf(ArchiveTag);
@@ -128,7 +132,7 @@ sealed partial class ViewerPageModel : ObservableObject, IDisposable {
 		string jsonTempFile = path + ".tmp";
 
 		await using (var jsonStream = new FileStream(jsonTempFile, FileMode.Create, FileAccess.ReadWrite, FileShare.Read)) {
-			await ViewerJsonExport.Generate(jsonStream, strategy, state.Db, FilterModel.CreateFilter());
+			await ViewerJsonExport.Generate(jsonStream, state.Db, FilterModel.CreateFilter());
 
 			char[] jsonBuffer = new char[Math.Min(32768, jsonStream.Position)];
 			jsonStream.Position = 0;

app/Desktop/Main/Screens/MainContentScreen.axaml

@@ -74,7 +74,7 @@
     <DockPanel>
         <Border Classes="statusBar" DockPanel.Dock="Bottom">
             <DockPanel>
-                <TextBlock Classes="invisibleTabItem" DockPanel.Dock="Left">Attachments</TextBlock>
+                <TextBlock Classes="invisibleTabItem" DockPanel.Dock="Left">Downloads</TextBlock>
                 <controls:StatusBar DataContext="{Binding StatusBarModel}" DockPanel.Dock="Right" />
             </DockPanel>
         </Border>
@@ -94,9 +94,9 @@
                     <ContentPresenter Content="{Binding TrackingPage}" Classes="page" />
                 </ScrollViewer>
             </TabItem>
-            <TabItem x:Name="TabAttachments" Header="Attachments" Grid.Row="2">
+            <TabItem x:Name="TabDownloads" Header="Downloads" Grid.Row="2">
                 <ScrollViewer>
-                    <ContentPresenter Content="{Binding AttachmentsPage}" Classes="page" />
+                    <ContentPresenter Content="{Binding DownloadsPage}" Classes="page" />
                 </ScrollViewer>
             </TabItem>
             <TabItem x:Name="TabViewer" Header="Viewer" Grid.Row="3">

app/Desktop/Main/Screens/MainContentScreenModel.cs

@@ -13,8 +13,8 @@ sealed class MainContentScreenModel : IDisposable {
 	public TrackingPage TrackingPage { get; }
 	private TrackingPageModel TrackingPageModel { get; }
 
-	public AttachmentsPage AttachmentsPage { get; }
-	private AttachmentsPageModel AttachmentsPageModel { get; }
+	public DownloadsPage DownloadsPage { get; }
+	private DownloadsPageModel DownloadsPageModel { get; }
 
 	public ViewerPage ViewerPage { get; }
 	private ViewerPageModel ViewerPageModel { get; }
@@ -52,8 +52,8 @@ sealed class MainContentScreenModel : IDisposable {
 		TrackingPageModel = new TrackingPageModel(window);
 		TrackingPage = new TrackingPage { DataContext = TrackingPageModel };
 
-		AttachmentsPageModel = new AttachmentsPageModel(state);
-		AttachmentsPage = new AttachmentsPage { DataContext = AttachmentsPageModel };
+		DownloadsPageModel = new DownloadsPageModel(state);
+		DownloadsPage = new DownloadsPage { DataContext = DownloadsPageModel };
 
 		ViewerPageModel = new ViewerPageModel(window, state);
 		ViewerPage = new ViewerPage { DataContext = ViewerPageModel };
@@ -72,7 +72,7 @@ sealed class MainContentScreenModel : IDisposable {
 	}
 
 	public void Dispose() {
-		AttachmentsPageModel.Dispose();
+		DownloadsPageModel.Dispose();
 		ViewerPageModel.Dispose();
 		AdvancedPageModel.Dispose();
 		StatusBarModel.Dispose();

app/Desktop/Main/Screens/WelcomeScreenModel.cs

@@ -8,7 +8,7 @@ using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Dialogs.Progress;
 using DHT.Server.Database;
-using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Database.Sqlite.Schema;
 
 namespace DHT.Desktop.Main.Screens;
 

app/Resources/Tracker/scripts/state.js

@@ -48,6 +48,16 @@ const STATE = (function() {
 		});
 	};
 	
+	const getDate = function(date) {
+		if (date instanceof Date) {
+			return date;
+		}
+		else {
+			// noinspection JSUnresolvedReference
+			return date.toDate();
+		}
+	};
+	
 	const trackingStateChangedListeners = [];
 	let isTracking = false;
 	
@@ -69,8 +79,8 @@ const STATE = (function() {
 	 * @property {String} channel_id
 	 * @property {DiscordUser} author
 	 * @property {String} content
-	 * @property {Timestamp} timestamp
-	 * @property {Timestamp|null} editedTimestamp
+	 * @property {Date} timestamp
+	 * @property {Date|null} editedTimestamp
 	 * @property {DiscordAttachment[]} attachments
 	 * @property {Object[]} embeds
 	 * @property {DiscordMessageReaction[]} [reactions]
@@ -106,11 +116,6 @@ const STATE = (function() {
 	 * @property {Boolean} animated
 	 */
 	
-	/**
-	 * @name Timestamp
-	 * @property {Function} toDate
-	 */
-	
 	return {
 		setup(port, token) {
 			serverPort = port;
@@ -223,12 +228,12 @@ const STATE = (function() {
 					sender: msg.author.id,
 					channel: msg.channel_id,
 					text: msg.content,
-					timestamp: msg.timestamp.toDate().getTime()
+					timestamp: getDate(msg.timestamp).getTime()
 				};
 				
 				if (msg.editedTimestamp !== null) {
 					// noinspection JSUnusedGlobalSymbols
-					obj.editTimestamp = msg.editedTimestamp.toDate().getTime();
+					obj.editTimestamp = getDate(msg.editedTimestamp).getTime();
 				}
 				
 				if (msg.messageReference !== null) {

app/Resources/Viewer/index.html

@@ -6,6 +6,7 @@
     
     <script type="text/javascript">
 		window.DHT_EMBEDDED = "/*[ARCHIVE]*/";
+		/*[CONSTANTS]*/
 		/*[JS]*/
     </script>
     <style>

app/Resources/Viewer/scripts/discord.js

@@ -35,6 +35,23 @@ const DISCORD = (function() {
 	let templateReaction;
 	let templateReactionCustom;
 	
+	const fileUrlProcessor = function(serverUrl, serverToken) {
+		if (typeof serverUrl === "string" && typeof serverToken === "string") {
+			return url => serverUrl + "/get-downloaded-file/" + encodeURIComponent(url) + "?token=" + encodeURIComponent(serverToken);
+		}
+		else {
+			return url => url;
+		}
+	}(
+		window["DHT_SERVER_URL"],
+		window["DHT_SERVER_TOKEN"]
+	);
+	
+	const getEmoji = function(name, id, extension) {
+		const tag = ":" + name + ":";
+		return "<img src='" + fileUrlProcessor("https://cdn.discordapp.com/emojis/" + id + "." + extension) + "' alt='" + tag + "' title='" + tag + "' class='emoji'>";
+	};
+	
 	const processMessageContents = function(contents) {
 		let processed = DOM.escapeHTML(contents.replace(regex.formatUrlNoEmbed, "$1"));
 		
@@ -54,29 +71,33 @@ const DISCORD = (function() {
 				.replace(regex.formatStrike, "<s>$1</s>");
 		}
 		
-		const animatedEmojiExtension = SETTINGS.enableAnimatedEmoji ? "gif" : "png";
+		const animatedEmojiExtension = SETTINGS.enableAnimatedEmoji ? "gif" : "webp";
 		
 		// noinspection HtmlUnknownTarget
 		processed = processed
 			.replace(regex.formatUrl, "<a href='$1' target='_blank' rel='noreferrer'>$1</a>")
 			.replace(regex.mentionChannel, (full, match) => "<span class='link mention-chat'>#" + STATE.getChannelName(match) + "</span>")
 			.replace(regex.mentionUser, (full, match) => "<span class='link mention-user' title='#" + (STATE.getUserTag(match) || "????") + "'>@" + STATE.getUserName(match) + "</span>")
-			.replace(regex.customEmojiStatic, "<img src='https://cdn.discordapp.com/emojis/$2.png' alt=':$1:' title=':$1:' class='emoji'>")
-			.replace(regex.customEmojiAnimated, "<img src='https://cdn.discordapp.com/emojis/$2." + animatedEmojiExtension + "' alt=':$1:' title=':$1:' class='emoji'>");
+			.replace(regex.customEmojiStatic, (full, m1, m2) => getEmoji(m1, m2, "webp"))
+			.replace(regex.customEmojiAnimated, (full, m1, m2) => getEmoji(m1, m2, animatedEmojiExtension));
 		
 		return "<p>" + processed + "</p>";
 	};
 	
+	const getAvatarUrlObject = function(avatar) {
+		return { url: fileUrlProcessor("https://cdn.discordapp.com/avatars/" + avatar.id + "/" + avatar.path + ".webp") };
+	};
+	
 	const getImageEmbed = function(url, image) {
 		if (!SETTINGS.enableImagePreviews) {
 			return "";
 		}
 		
 		if (image.width && image.height) {
-			return templateEmbedImageWithSize.apply({ url, src: image.url, width: image.width, height: image.height });
+			return templateEmbedImageWithSize.apply({ url: fileUrlProcessor(url), src: fileUrlProcessor(image.url), width: image.width, height: image.height });
 		}
 		else {
-			return templateEmbedImage.apply({ url, src: image.url });
+			return templateEmbedImage.apply({ url: fileUrlProcessor(url), src: fileUrlProcessor(image.url) });
 		}
 	};
 	
@@ -125,8 +146,9 @@ const DISCORD = (function() {
 				"</div>"
 			].join(""));
 			
+			// noinspection HtmlUnknownTarget
 			templateUserAvatar = new TEMPLATE([
-				"<img src='https://cdn.discordapp.com/avatars/{id}/{path}.webp?size=128' alt=''>"
+				"<img src='{url}' alt=''>"
 			].join(""));
 			
 			// noinspection HtmlUnknownTarget
@@ -167,8 +189,9 @@ const DISCORD = (function() {
 				"<span class='reaction-wrapper'><span class='reaction-emoji'>{n}</span><span class='count'>{c}</span></span>"
 			].join(""));
 			
+			// noinspection HtmlUnknownTarget
 			templateReactionCustom = new TEMPLATE([
-				"<span class='reaction-wrapper'><img src='https://cdn.discordapp.com/emojis/{id}.{ext}' alt=':{n}:' title=':{n}:' class='reaction-emoji-custom'><span class='count'>{c}</span></span>"
+				"<span class='reaction-wrapper'><img src='{url}' alt=':{n}:' title=':{n}:' class='reaction-emoji-custom'><span class='count'>{c}</span></span>"
 			].join(""));
 		},
 		
@@ -199,7 +222,7 @@ const DISCORD = (function() {
 		getMessageHTML(message) { // noinspection FunctionWithInconsistentReturnsJS
 			return (SETTINGS.enableUserAvatars ? templateMessageWithAvatar : templateMessageNoAvatar).apply(message, (property, value) => {
 				if (property === "avatar") {
-					return value ? templateUserAvatar.apply(value) : "";
+					return value ? templateUserAvatar.apply(getAvatarUrlObject(value)) : "";
 				}
 				else if (property === "user.tag") {
 					return value ? value : "????";
@@ -220,10 +243,10 @@ const DISCORD = (function() {
 							return templateEmbedUnsupported.apply(embed);
 						}
 						else if ("image" in embed && embed.image.url) {
-							return getImageEmbed(embed.url, embed.image);
+							return getImageEmbed(fileUrlProcessor(embed.url), embed.image);
 						}
 						else if ("thumbnail" in embed && embed.thumbnail.url) {
-							return getImageEmbed(embed.url, embed.thumbnail);
+							return getImageEmbed(fileUrlProcessor(embed.url), embed.thumbnail);
 						}
 						else if ("title" in embed && "description" in embed) {
 							return templateEmbedRich.apply(embed);
@@ -242,14 +265,16 @@ const DISCORD = (function() {
 					}
 					
 					return value.map(attachment => {
+						const url = fileUrlProcessor(attachment.url);
+						
 						if (!DISCORD.isImageAttachment(attachment) || !SETTINGS.enableImagePreviews) {
-							return templateAttachmentDownload.apply(attachment);
+							return templateAttachmentDownload.apply({ url, name: attachment.name });
 						}
 						else if ("width" in attachment && "height" in attachment) {
-							return templateEmbedImageWithSize.apply({ url: attachment.url, src: attachment.url, width: attachment.width, height: attachment.height });
+							return templateEmbedImageWithSize.apply({ url, src: url, width: attachment.width, height: attachment.height });
 						}
 						else {
-							return templateEmbedImage.apply({ url: attachment.url, src: attachment.url });
+							return templateEmbedImage.apply({ url, src: url });
 						}
 					}).join("");
 				}
@@ -265,7 +290,7 @@ const DISCORD = (function() {
 					}
 					
 					const user = "<span class='reply-username' title='#" + (value.user.tag ? value.user.tag : "????") + "'>" + value.user.name + "</span>";
-					const avatar = SETTINGS.enableUserAvatars && value.avatar ? "<span class='reply-avatar'>" + templateUserAvatar.apply(value.avatar) + "</span>" : "";
+					const avatar = SETTINGS.enableUserAvatars && value.avatar ? "<span class='reply-avatar'>" + templateUserAvatar.apply(getAvatarUrlObject(value.avatar)) + "</span>" : "";
 					const contents = value.contents ? "<span class='reply-contents'>" + processMessageContents(value.contents) + "</span>" : "";
 					
 					return "<span class='jump' data-jump='" + value.id + "'>Jump to reply</span><span class='user'>" + avatar + user + "</span>" + contents;
@@ -277,9 +302,10 @@ const DISCORD = (function() {
 					
 					return "<div class='reactions'>" + value.map(reaction => {
 						if ("id" in reaction){
-							// noinspection JSUnusedGlobalSymbols, JSUnresolvedVariable
-							reaction.ext = reaction.a && SETTINGS.enableAnimatedEmoji ? "gif" : "png";
-							return templateReactionCustom.apply(reaction);
+							const ext = reaction.a && SETTINGS.enableAnimatedEmoji ? "gif" : "webp";
+							const url = fileUrlProcessor("https://cdn.discordapp.com/emojis/" + reaction.id + "." + ext);
+							// noinspection JSUnusedGlobalSymbols
+							return templateReactionCustom.apply({ url, n: reaction.n, c: reaction.c });
 						}
 						else {
 							return templateReaction.apply(reaction);

app/Server/Data/Aggregations/DownloadStatusStatistics.cs

@@ -1,15 +1,19 @@
 namespace DHT.Server.Data.Aggregations;
 
 public sealed class DownloadStatusStatistics {
-	public int EnqueuedCount { get; internal set; }
-	public ulong EnqueuedSize { get; internal set; }
+	public int PendingCount { get; internal init; }
+	public ulong PendingTotalSize { get; internal init; }
+	public int PendingWithUnknownSizeCount { get; internal init; }
 
-	public int SuccessfulCount { get; internal set; }
-	public ulong SuccessfulSize { get; internal set; }
+	public int SuccessfulCount { get; internal init; }
+	public ulong SuccessfulTotalSize { get; internal init; }
+	public int SuccessfulWithUnknownSizeCount { get; internal init; }
 
-	public int FailedCount { get; internal set; }
-	public ulong FailedSize { get; internal set; }
-
-	public int SkippedCount { get; internal set; }
-	public ulong SkippedSize { get; internal set; }
+	public int FailedCount { get; internal init; }
+	public ulong FailedTotalSize { get; internal init; }
+	public int FailedWithUnknownSizeCount { get; internal init; }
+	
+	public int SkippedCount { get; internal init; }
+	public ulong SkippedTotalSize { get; internal init; }
+	public int SkippedWithUnknownSizeCount { get; internal init; }
 }

app/Server/Data/Download.cs

@@ -1,33 +1,17 @@
-using System;
-using System.Net;
-using DHT.Server.Download;
-
 namespace DHT.Server.Data;
 
-public readonly struct Download {
-	internal static Download NewSuccess(DownloadItem item, byte[] data) {
-		return new Download(item.NormalizedUrl, item.DownloadUrl, DownloadStatus.Success, (ulong) Math.Max(data.LongLength, 0), data);
-	}
-
-	internal static Download NewFailure(DownloadItem item, HttpStatusCode? statusCode, ulong size) {
-		return new Download(item.NormalizedUrl, item.DownloadUrl, statusCode.HasValue ? (DownloadStatus) (int) statusCode : DownloadStatus.GenericError, size);
-	}
-
+public sealed class Download {
 	public string NormalizedUrl { get; }
 	public string DownloadUrl { get; }
 	public DownloadStatus Status { get; }
-	public ulong Size { get; }
-	public byte[]? Data { get; }
+	public string? Type { get; }
+	public ulong? Size { get; }
 
-	internal Download(string normalizedUrl, string downloadUrl, DownloadStatus status, ulong size, byte[]? data = null) {
+	internal Download(string normalizedUrl, string downloadUrl, DownloadStatus status, string? type, ulong? size) {
 		NormalizedUrl = normalizedUrl;
 		DownloadUrl = downloadUrl;
 		Status = status;
+		Type = type;
 		Size = size;
-		Data = data;
-	}
-
-	internal Download WithData(byte[] data) {
-		return new Download(NormalizedUrl, DownloadUrl, Status, Size, data);
 	}
 }

app/Server/Data/DownloadStatus.cs

@@ -6,8 +6,9 @@ namespace DHT.Server.Data;
 /// Extends <see cref="HttpStatusCode"/> with custom status codes in the range 0-99.
 /// </summary>
 public enum DownloadStatus {
-	Enqueued = 0,
+	Pending = 0,
 	GenericError = 1,
 	Downloading = 2,
+	LastCustomCode = 99,
 	Success = HttpStatusCode.OK
 }

app/Server/Data/DownloadedAttachment.cs

@@ -1,6 +0,0 @@
-namespace DHT.Server.Data;
-
-public readonly struct DownloadedAttachment {
-	public string? Type { get; internal init; }
-	public byte[] Data { get; internal init; }
-}

app/Server/Data/Embeds/DiscordEmbedJson.cs

@@ -0,0 +1,17 @@
+namespace DHT.Server.Data.Embeds;
+
+sealed class DiscordEmbedJson {
+	public string? Type { get; set; }
+	public string? Url { get; set; }
+	
+	public JsonImage? Image { get; set; }
+	public JsonImage? Thumbnail { get; set; }
+	public JsonImage? Video { get; set; }
+
+	public sealed class JsonImage {
+		public string? Url { get; set; }
+		public string? ProxyUrl { get; set; }
+		public int? Width { get; set; }
+		public int? Height { get; set; }
+	}
+}

app/Server/Data/Embeds/DiscordEmbedJsonContext.cs

@@ -0,0 +1,7 @@
+using System.Text.Json.Serialization;
+
+namespace DHT.Server.Data.Embeds;
+
+[JsonSourceGenerationOptions(PropertyNamingPolicy = JsonKnownNamingPolicy.SnakeCaseLower, GenerationMode = JsonSourceGenerationMode.Default)]
+[JsonSerializable(typeof(DiscordEmbedJson))]
+sealed partial class DiscordEmbedJsonContext : JsonSerializerContext;

app/Server/Data/Filters/AttachmentFilter.cs

@@ -1,15 +0,0 @@
-namespace DHT.Server.Data.Filters;
-
-public sealed class AttachmentFilter {
-	public ulong? MaxBytes { get; set; } = null;
-
-	public DownloadItemRules? DownloadItemRule { get; set; } = null;
-
-	public bool IsEmpty => MaxBytes == null &&
-	                       DownloadItemRule == null;
-
-	public enum DownloadItemRules {
-		OnlyNotPresent,
-		OnlyPresent
-	}
-}

app/Server/Data/Filters/DownloadItemFilter.cs

@@ -3,8 +3,10 @@ using System.Collections.Generic;
 namespace DHT.Server.Data.Filters;
 
 public sealed class DownloadItemFilter {
-	public HashSet<DownloadStatus>? IncludeStatuses { get; init; } = null;
-	public HashSet<DownloadStatus>? ExcludeStatuses { get; init; } = null;
+	public HashSet<DownloadStatus>? IncludeStatuses { get; set; } = null;
+	public HashSet<DownloadStatus>? ExcludeStatuses { get; set; } = null;
+	
+	public ulong? MaxBytes { get; set; } = null;
 
-	public bool IsEmpty => IncludeStatuses == null && ExcludeStatuses == null;
+	public bool IsEmpty => IncludeStatuses == null && ExcludeStatuses == null && MaxBytes == null;
 }

app/Server/Database/DatabaseExtensions.cs

@@ -25,8 +25,10 @@ public static class DatabaseExtensions {
 		
 		await target.Messages.Add(batchedMessages);
 
-		await foreach (var download in source.Downloads.GetWithoutData()) {
-			await target.Downloads.AddDownload(download.Status == DownloadStatus.Success ? await source.Downloads.HydrateWithData(download) : download);
+		await foreach (var download in source.Downloads.Get()) {
+			if (download.Status != DownloadStatus.Success || !await source.Downloads.GetDownloadData(download.NormalizedUrl, stream => target.Downloads.AddDownload(download, stream))) {
+				await target.Downloads.AddDownload(download, stream: null);
+			}
 		}
 	}
 }

app/Server/Database/DummyDatabaseFile.cs

@@ -14,7 +14,6 @@ sealed class DummyDatabaseFile : IDatabaseFile {
 	public IServerRepository Servers { get; } = new IServerRepository.Dummy();
 	public IChannelRepository Channels { get; } = new IChannelRepository.Dummy();
 	public IMessageRepository Messages { get; } = new IMessageRepository.Dummy();
-	public IAttachmentRepository Attachments { get; } = new IAttachmentRepository.Dummy();
 	public IDownloadRepository Downloads { get; } = new IDownloadRepository.Dummy();
 	
 	private DummyDatabaseFile() {}

app/Server/Database/Exceptions/DatabaseTooNewException.cs

@@ -5,9 +5,9 @@ namespace DHT.Server.Database.Exceptions;
 
 public sealed class DatabaseTooNewException : Exception {
 	public int DatabaseVersion { get; }
-	public int CurrentVersion => Schema.Version;
+	public int CurrentVersion => SqliteSchema.Version;
 
-	internal DatabaseTooNewException(int databaseVersion) : base("Database is too new: " + databaseVersion + " > " + Schema.Version) {
+	internal DatabaseTooNewException(int databaseVersion) : base("Database is too new: " + databaseVersion + " > " + SqliteSchema.Version) {
 		this.DatabaseVersion = databaseVersion;
 	}
 }

app/Server/Database/Export/Strategy/IViewerExportStrategy.cs

@@ -1,7 +0,0 @@
-using DHT.Server.Data;
-
-namespace DHT.Server.Database.Export.Strategy;
-
-public interface IViewerExportStrategy {
-	string GetAttachmentUrl(Attachment attachment);
-}

app/Server/Database/Export/Strategy/LiveViewerExportStrategy.cs

@@ -1,18 +0,0 @@
-using System.Net;
-using DHT.Server.Data;
-
-namespace DHT.Server.Database.Export.Strategy;
-
-public sealed class LiveViewerExportStrategy : IViewerExportStrategy {
-	private readonly string safePort;
-	private readonly string safeToken;
-
-	public LiveViewerExportStrategy(ushort port, string token) {
-		this.safePort = port.ToString();
-		this.safeToken = WebUtility.UrlEncode(token);
-	}
-
-	public string GetAttachmentUrl(Attachment attachment) {
-		return "http://127.0.0.1:" + safePort + "/get-attachment/" + WebUtility.UrlEncode(attachment.NormalizedUrl) + "?token=" + safeToken;
-	}
-}

app/Server/Database/Export/Strategy/StandaloneViewerExportStrategy.cs

@@ -1,18 +0,0 @@
-using DHT.Server.Data;
-
-namespace DHT.Server.Database.Export.Strategy;
-
-public sealed class StandaloneViewerExportStrategy : IViewerExportStrategy {
-	public static StandaloneViewerExportStrategy Instance { get; } = new ();
-
-	private StandaloneViewerExportStrategy() {}
-
-	public string GetAttachmentUrl(Attachment attachment) {
-		// The normalized URL will not load files from Discord CDN once the time limit is enforced.
-		
-		// The downloaded URL would work, but only for a limited time, so it is better for the links to not work
-		// rather than give users a false sense of security.
-		
-		return attachment.NormalizedUrl;
-	}
-}

app/Server/Database/Export/ViewerJsonExport.cs

@@ -6,7 +6,6 @@ using System.Text.Json;
 using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
-using DHT.Server.Database.Export.Strategy;
 using DHT.Utils.Logging;
 
 namespace DHT.Server.Database.Export;
@@ -14,7 +13,7 @@ namespace DHT.Server.Database.Export;
 public static class ViewerJsonExport {
 	private static readonly Log Log = Log.ForType(typeof(ViewerJsonExport));
 
-	public static async Task Generate(Stream stream, IViewerExportStrategy strategy, IDatabaseFile db, MessageFilter? filter = null) {
+	public static async Task Generate(Stream stream, IDatabaseFile db, MessageFilter? filter = null) {
 		var perf = Log.Start();
 
 		var includedUserIds = new HashSet<ulong>();
@@ -49,7 +48,7 @@ public static class ViewerJsonExport {
 				Servers = servers,
 				Channels = channels
 			},
-			Data = GenerateMessageList(includedMessages, userIndices, strategy)
+			Data = GenerateMessageList(includedMessages, userIndices)
 		};
 
 		perf.Step("Generate value object");
@@ -125,7 +124,7 @@ public static class ViewerJsonExport {
 		return channels;
 	}
 
-	private static Dictionary<Snowflake, Dictionary<Snowflake, ViewerJson.JsonMessage>> GenerateMessageList(List<Message> includedMessages, Dictionary<ulong, int> userIndices, IViewerExportStrategy strategy) {
+	private static Dictionary<Snowflake, Dictionary<Snowflake, ViewerJson.JsonMessage>> GenerateMessageList(List<Message> includedMessages, Dictionary<ulong, int> userIndices) {
 		var data = new Dictionary<Snowflake, Dictionary<Snowflake, ViewerJson.JsonMessage>>();
 
 		foreach (var grouping in includedMessages.GroupBy(static message => message.Channel)) {
@@ -142,9 +141,9 @@ public static class ViewerJsonExport {
 					Te = message.EditTimestamp,
 					R = message.RepliedToId?.ToString(),
 					
-					A = message.Attachments.IsEmpty ? null : message.Attachments.Select(attachment => {
+					A = message.Attachments.IsEmpty ? null : message.Attachments.Select(static attachment => {
 						var a = new ViewerJson.JsonMessageAttachment {
-							Url = strategy.GetAttachmentUrl(attachment),
+							Url = attachment.DownloadUrl,
 							Name = Uri.TryCreate(attachment.NormalizedUrl, UriKind.Absolute, out var uri) ? Path.GetFileName(uri.LocalPath) : attachment.NormalizedUrl
 						};
 

app/Server/Database/IDatabaseFile.cs

@@ -11,7 +11,6 @@ public interface IDatabaseFile : IAsyncDisposable {
 	IServerRepository Servers { get; }
 	IChannelRepository Channels { get; }
 	IMessageRepository Messages { get; }
-	IAttachmentRepository Attachments { get; }
 	IDownloadRepository Downloads { get; }
 
 	Task Vacuum();

app/Server/Database/Import/LegacyArchiveImport.cs

@@ -161,7 +161,7 @@ public static class LegacyArchiveImport {
 
 		var messagesObj = data.HasKey(channelIdStr) ? data.RequireObject(channelIdStr, DataPath) : (JsonElement?) null;
 		if (messagesObj == null) {
-			return Array.Empty<Message>();
+			return [];
 		}
 
 		return messagesObj.Value.EnumerateObject().Select(item => {

app/Server/Database/Repositories/IAttachmentRepository.cs

@@ -1,21 +0,0 @@
-using System;
-using System.Reactive.Linq;
-using System.Threading;
-using System.Threading.Tasks;
-using DHT.Server.Data.Filters;
-
-namespace DHT.Server.Database.Repositories;
-
-public interface IAttachmentRepository {
-	IObservable<long> TotalCount { get; }
-
-	Task<long> Count(AttachmentFilter? filter = null, CancellationToken cancellationToken = default);
-
-	internal sealed class Dummy : IAttachmentRepository {
-		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
-		
-		public Task<long> Count(AttachmentFilter? filter = null, CancellationToken cancellationToken = default) {
-			return Task.FromResult(0L);
-		}
-	}
-}

app/Server/Database/Repositories/IDownloadRepository.cs

@@ -1,10 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
-using DHT.Server.Data;
 using DHT.Server.Data.Aggregations;
 using DHT.Server.Data.Filters;
 using DHT.Server.Download;
@@ -14,55 +14,61 @@ namespace DHT.Server.Database.Repositories;
 public interface IDownloadRepository {
 	IObservable<long> TotalCount { get; }
 
-	Task AddDownload(Data.Download download);
+	Task AddDownload(Data.Download item, Stream? stream);
 
-	Task<DownloadStatusStatistics> GetStatistics(CancellationToken cancellationToken = default);
+	Task<long> Count(DownloadItemFilter filter, CancellationToken cancellationToken = default);
 	
-	IAsyncEnumerable<Data.Download> GetWithoutData();
+	Task<DownloadStatusStatistics> GetStatistics(DownloadItemFilter nonSkippedFilter, CancellationToken cancellationToken = default);
+	
+	IAsyncEnumerable<Data.Download> Get();
 
-	Task<Data.Download> HydrateWithData(Data.Download download);
+	Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor);
+	
+	Task<bool> GetSuccessfulDownloadWithData(string normalizedUrl, Func<Data.Download, Stream, Task> dataProcessor);
 
-	Task<DownloadedAttachment?> GetDownloadedAttachment(string normalizedUrl);
-
-	Task<int> EnqueueDownloadItems(AttachmentFilter? filter = null, CancellationToken cancellationToken = default);
-
-	IAsyncEnumerable<DownloadItem> PullEnqueuedDownloadItems(int count, CancellationToken cancellationToken = default);
-
-	Task RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode);
+	IAsyncEnumerable<DownloadItem> PullPendingDownloadItems(int count, DownloadItemFilter filter, CancellationToken cancellationToken = default);
+	
+	Task MoveDownloadingItemsBackToQueue(CancellationToken cancellationToken = default);
+	
+	Task<int> RetryFailed(CancellationToken cancellationToken = default);
 
 	internal sealed class Dummy : IDownloadRepository {
 		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
 
-		public Task AddDownload(Data.Download download) {
+		public Task AddDownload(Data.Download item, Stream? stream) {
 			return Task.CompletedTask;
 		}
 
-		public Task<DownloadStatusStatistics> GetStatistics(CancellationToken cancellationToken) {
+		public Task<long> Count(DownloadItemFilter filter, CancellationToken cancellationToken) {
+			return Task.FromResult(0L);
+		}
+
+		public Task<DownloadStatusStatistics> GetStatistics(DownloadItemFilter nonSkippedFilter, CancellationToken cancellationToken) {
 			return Task.FromResult(new DownloadStatusStatistics());
 		}
 
-		public IAsyncEnumerable<Data.Download> GetWithoutData() {
+		public IAsyncEnumerable<Data.Download> Get() {
 			return AsyncEnumerable.Empty<Data.Download>();
 		}
 
-		public Task<Data.Download> HydrateWithData(Data.Download download) {
-			return Task.FromResult(download);
+		public Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor) {
+			return Task.FromResult(false);
 		}
 
-		public Task<DownloadedAttachment?> GetDownloadedAttachment(string normalizedUrl) {
-			return Task.FromResult<DownloadedAttachment?>(null);
+		public Task<bool> GetSuccessfulDownloadWithData(string normalizedUrl, Func<Data.Download, Stream, Task> dataProcessor) {
+			return Task.FromResult(false);
 		}
 
-		public Task<int> EnqueueDownloadItems(AttachmentFilter? filter, CancellationToken cancellationToken) {
-			return Task.FromResult(0);
-		}
-
-		public IAsyncEnumerable<DownloadItem> PullEnqueuedDownloadItems(int count, CancellationToken cancellationToken) {
+		public IAsyncEnumerable<DownloadItem> PullPendingDownloadItems(int count, DownloadItemFilter filter, CancellationToken cancellationToken) {
 			return AsyncEnumerable.Empty<DownloadItem>();
 		}
 
-		public Task RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {
+		public Task MoveDownloadingItemsBackToQueue(CancellationToken cancellationToken) {
 			return Task.CompletedTask;
 		}
+
+		public Task<int> RetryFailed(CancellationToken cancellationToken) {
+			return Task.FromResult(0);
+		}
 	}
 }

app/Server/Database/Sqlite/Repositories/BaseSqliteRepository.cs

@@ -1,16 +1,20 @@
 using System;
+using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using DHT.Utils.Logging;
 using DHT.Utils.Tasks;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
 abstract class BaseSqliteRepository : IDisposable {
-	private readonly ObservableThrottledTask<long> totalCountTask = new (TaskScheduler.Default);
-	
-	public IObservable<long> TotalCount => totalCountTask;
+	private readonly ObservableThrottledTask<long> totalCountTask;
 
-	protected BaseSqliteRepository() {
+	public IObservable<long> TotalCount { get; }
+
+	protected BaseSqliteRepository(Log log) {
+		totalCountTask = new ObservableThrottledTask<long>(log, TaskScheduler.Default);
+		TotalCount = totalCountTask.DistinctUntilChanged();
 		UpdateTotalCount();
 	}
 
@@ -21,6 +25,6 @@ abstract class BaseSqliteRepository : IDisposable {
 	protected void UpdateTotalCount() {
 		totalCountTask.Post(Count);
 	}
-	
+
 	public abstract Task<long> Count(CancellationToken cancellationToken);
 }

app/Server/Database/Sqlite/Repositories/SqliteAttachmentRepository.cs

@@ -1,28 +0,0 @@
-using System.Threading;
-using System.Threading.Tasks;
-using DHT.Server.Data.Filters;
-using DHT.Server.Database.Repositories;
-using DHT.Server.Database.Sqlite.Utils;
-
-namespace DHT.Server.Database.Sqlite.Repositories;
-
-sealed class SqliteAttachmentRepository : BaseSqliteRepository, IAttachmentRepository {
-	private readonly SqliteConnectionPool pool;
-
-	public SqliteAttachmentRepository(SqliteConnectionPool pool) {
-		this.pool = pool;
-	}
-
-	internal new void UpdateTotalCount() {
-		base.UpdateTotalCount();
-	}
-	
-	public override Task<long> Count(CancellationToken cancellationToken) {
-		return Count(filter: null, cancellationToken);
-	}
-
-	public async Task<long> Count(AttachmentFilter? filter, CancellationToken cancellationToken) {
-		await using var conn = await pool.Take();
-		return await conn.ExecuteReaderAsync("SELECT COUNT(DISTINCT normalized_url) FROM attachments a" + filter.GenerateWhereClause("a"), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
-	}
-}

app/Server/Database/Sqlite/Repositories/SqliteChannelRepository.cs

@@ -4,21 +4,24 @@ using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Database.Repositories;
 using DHT.Server.Database.Sqlite.Utils;
+using DHT.Utils.Logging;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
 sealed class SqliteChannelRepository : BaseSqliteRepository, IChannelRepository {
+	private static readonly Log Log = Log.ForType<SqliteChannelRepository>();
+	
 	private readonly SqliteConnectionPool pool;
 
-	public SqliteChannelRepository(SqliteConnectionPool pool) {
+	public SqliteChannelRepository(SqliteConnectionPool pool) : base(Log) {
 		this.pool = pool;
 	}
 
 	public async Task Add(IReadOnlyList<Channel> channels) {
-		await using var conn = await pool.Take();
-
-		await using (var tx = await conn.BeginTransactionAsync()) {
+		await using (var conn = await pool.Take()) {
+			await conn.BeginTransactionAsync();
+			
 			await using var cmd = conn.Upsert("channels", [
 				("id", SqliteType.Integer),
 				("server", SqliteType.Integer),
@@ -40,7 +43,7 @@ sealed class SqliteChannelRepository : BaseSqliteRepository, IChannelRepository
 				await cmd.ExecuteNonQueryAsync();
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 		}
 
 		UpdateTotalCount();
@@ -57,7 +60,7 @@ sealed class SqliteChannelRepository : BaseSqliteRepository, IChannelRepository
 		await using var cmd = conn.Command("SELECT id, server, name, parent_id, position, topic, nsfw FROM channels");
 		await using var reader = await cmd.ExecuteReaderAsync();
 
-		while (reader.Read()) {
+		while (await reader.ReadAsync()) {
 			yield return new Channel {
 				Id = reader.GetUint64(0),
 				Server = reader.GetUint64(1),

app/Server/Database/Sqlite/Repositories/SqliteDownloadRepository.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -9,198 +10,274 @@ using DHT.Server.Data.Filters;
 using DHT.Server.Database.Repositories;
 using DHT.Server.Database.Sqlite.Utils;
 using DHT.Server.Download;
+using DHT.Utils.Logging;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
-sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepository {
-	private readonly SqliteConnectionPool pool;
+sealed class SqliteDownloadRepository(SqliteConnectionPool pool) : BaseSqliteRepository(Log), IDownloadRepository {
+	private static readonly Log Log = Log.ForType<SqliteDownloadRepository>();
 
-	public SqliteDownloadRepository(SqliteConnectionPool pool) {
-		this.pool = pool;
+	internal sealed class NewDownloadCollector : IAsyncDisposable {
+		private readonly SqliteDownloadRepository repository;
+		private bool hasAdded = false;
+
+		private readonly SqliteCommand metadataCmd;
+
+		public NewDownloadCollector(SqliteDownloadRepository repository, ISqliteConnection conn) {
+			this.repository = repository;
+
+			metadataCmd = conn.Command(
+				"""
+				INSERT INTO download_metadata (normalized_url, download_url, status, type, size)
+				VALUES (:normalized_url, :download_url, :status, :type, :size)
+				ON CONFLICT DO NOTHING
+				"""
+			);
+			metadataCmd.Add(":normalized_url", SqliteType.Text);
+			metadataCmd.Add(":download_url", SqliteType.Text);
+			metadataCmd.Add(":status", SqliteType.Integer);
+			metadataCmd.Add(":type", SqliteType.Text);
+			metadataCmd.Add(":size", SqliteType.Integer);
+		}
+
+		public async Task Add(Data.Download download) {
+			metadataCmd.Set(":normalized_url", download.NormalizedUrl);
+			metadataCmd.Set(":download_url", download.DownloadUrl);
+			metadataCmd.Set(":status", (int) download.Status);
+			metadataCmd.Set(":type", download.Type);
+			metadataCmd.Set(":size", download.Size);
+			hasAdded |= await metadataCmd.ExecuteNonQueryAsync() > 0;
+		}
+
+		public void OnCommitted() {
+			if (hasAdded) {
+				repository.UpdateTotalCount();
+			}
+		}
+
+		public async ValueTask DisposeAsync() {
+			await metadataCmd.DisposeAsync();
+		}
 	}
 
-	public async Task AddDownload(Data.Download download) {
+	public async Task AddDownload(Data.Download item, Stream? stream) {
 		await using (var conn = await pool.Take()) {
-			await using var cmd = conn.Upsert("downloads", [
+			await conn.BeginTransactionAsync();
+			
+			await using var metadataCmd = conn.Upsert("download_metadata", [
 				("normalized_url", SqliteType.Text),
 				("download_url", SqliteType.Text),
 				("status", SqliteType.Integer),
+				("type", SqliteType.Text),
 				("size", SqliteType.Integer),
-				("blob", SqliteType.Blob)
 			]);
 
-			cmd.Set(":normalized_url", download.NormalizedUrl);
-			cmd.Set(":download_url", download.DownloadUrl);
-			cmd.Set(":status", (int) download.Status);
-			cmd.Set(":size", download.Size);
-			cmd.Set(":blob", download.Data);
-			await cmd.ExecuteNonQueryAsync();
+			metadataCmd.Set(":normalized_url", item.NormalizedUrl);
+			metadataCmd.Set(":download_url", item.DownloadUrl);
+			metadataCmd.Set(":status", (int) item.Status);
+			metadataCmd.Set(":type", item.Type);
+			metadataCmd.Set(":size", item.Size);
+			await metadataCmd.ExecuteNonQueryAsync();
+
+			if (stream == null) {
+				await using var deleteBlobCmd = conn.Command("DELETE FROM download_blobs WHERE normalized_url = :normalized_url");
+				deleteBlobCmd.AddAndSet(":normalized_url", SqliteType.Text, item.NormalizedUrl);
+				await deleteBlobCmd.ExecuteNonQueryAsync();
+			}
+			else {
+				await using var upsertBlobCmd = conn.Command(
+					"""
+					INSERT INTO download_blobs (normalized_url, blob)
+					VALUES (:normalized_url, ZEROBLOB(:blob_length))
+					ON CONFLICT (normalized_url) DO UPDATE SET blob = excluded.blob
+					RETURNING rowid
+					"""
+				);
+				
+				upsertBlobCmd.AddAndSet(":normalized_url", SqliteType.Text, item.NormalizedUrl);
+				upsertBlobCmd.AddAndSet(":blob_length", SqliteType.Integer, item.Size);
+				long rowid = await upsertBlobCmd.ExecuteLongScalarAsync();
+
+				await using var blob = new SqliteBlob(conn.InnerConnection, "download_blobs", "blob", rowid);
+				await stream.CopyToAsync(blob);
+			}
+
+			await conn.CommitTransactionAsync();
 		}
 
 		UpdateTotalCount();
 	}
 
-	public override async Task<long> Count(CancellationToken cancellationToken) {
-		await using var conn = await pool.Take();
-		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM downloads", static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
+	public override Task<long> Count(CancellationToken cancellationToken) {
+		return Count(filter: null, cancellationToken);
 	}
 
-	public async Task<DownloadStatusStatistics> GetStatistics(CancellationToken cancellationToken) {
-		static async Task LoadUndownloadedStatistics(ISqliteConnection conn, DownloadStatusStatistics result, CancellationToken cancellationToken) {
-			await using var cmd = conn.Command(
-				"""
-				SELECT IFNULL(COUNT(size), 0), IFNULL(SUM(size), 0)
-				FROM (SELECT MAX(a.size) size
-				      FROM attachments a
-				      WHERE a.normalized_url NOT IN (SELECT d.normalized_url FROM downloads d)
-				      GROUP BY a.normalized_url)
-				""");
-
-			await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
-
-			if (reader.Read()) {
-				result.SkippedCount = reader.GetInt32(0);
-				result.SkippedSize = reader.GetUint64(1);
-			}
-		}
-
-		static async Task LoadSuccessStatistics(ISqliteConnection conn, DownloadStatusStatistics result, CancellationToken cancellationToken) {
-			await using var cmd = conn.Command(
-				"""
-				SELECT
-				IFNULL(SUM(CASE WHEN status IN (:enqueued, :downloading) THEN 1 ELSE 0 END), 0),
-				IFNULL(SUM(CASE WHEN status IN (:enqueued, :downloading) THEN size ELSE 0 END), 0),
-				IFNULL(SUM(CASE WHEN status = :success THEN 1 ELSE 0 END), 0),
-				IFNULL(SUM(CASE WHEN status = :success THEN size ELSE 0 END), 0),
-				IFNULL(SUM(CASE WHEN status NOT IN (:enqueued, :downloading) AND status != :success THEN 1 ELSE 0 END), 0),
-				IFNULL(SUM(CASE WHEN status NOT IN (:enqueued, :downloading) AND status != :success THEN size ELSE 0 END), 0)
-				FROM downloads
-				"""
-			);
-
-			cmd.AddAndSet(":enqueued", SqliteType.Integer, (int) DownloadStatus.Enqueued);
-			cmd.AddAndSet(":downloading", SqliteType.Integer, (int) DownloadStatus.Downloading);
-			cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
-
-			await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
-
-			if (reader.Read()) {
-				result.EnqueuedCount = reader.GetInt32(0);
-				result.EnqueuedSize = reader.GetUint64(1);
-				result.SuccessfulCount = reader.GetInt32(2);
-				result.SuccessfulSize = reader.GetUint64(3);
-				result.FailedCount = reader.GetInt32(4);
-				result.FailedSize = reader.GetUint64(5);
-			}
-		}
-
-		var result = new DownloadStatusStatistics();
-
+	public async Task<long> Count(DownloadItemFilter? filter, CancellationToken cancellationToken) {
 		await using var conn = await pool.Take();
-		await LoadUndownloadedStatistics(conn, result, cancellationToken);
-		await LoadSuccessStatistics(conn, result, cancellationToken);
-		return result;
+		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM download_metadata" + filter.GenerateConditions().BuildWhereClause(), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
 	}
 
-	public async IAsyncEnumerable<Data.Download> GetWithoutData() {
+	public async Task<DownloadStatusStatistics> GetStatistics(DownloadItemFilter nonSkippedFilter, CancellationToken cancellationToken) {
+		nonSkippedFilter.IncludeStatuses = null;
+		nonSkippedFilter.ExcludeStatuses = null;
+		string nonSkippedFilterConditions = nonSkippedFilter.GenerateConditions().Build();
+
 		await using var conn = await pool.Take();
 
-		await using var cmd = conn.Command("SELECT normalized_url, download_url, status, size FROM downloads");
+		await using var cmd = conn.Command(
+			$"""
+			 SELECT
+			 IFNULL(SUM(CASE WHEN (status = :downloading) OR (status = :pending AND {nonSkippedFilterConditions}) THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN (status = :downloading) OR (status = :pending AND {nonSkippedFilterConditions}) THEN IFNULL(size, 0) ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN ((status = :downloading) OR (status = :pending AND {nonSkippedFilterConditions})) AND size IS NULL THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status = :success THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status = :success THEN IFNULL(size, 0) ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status = :success AND size IS NULL THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status NOT IN (:pending, :downloading, :success) THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status NOT IN (:pending, :downloading, :success) THEN IFNULL(size, 0) ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status NOT IN (:pending, :downloading, :success) AND size IS NULL THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status = :pending AND NOT ({nonSkippedFilterConditions}) THEN 1 ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status = :pending AND NOT ({nonSkippedFilterConditions}) THEN IFNULL(size, 0) ELSE 0 END), 0),
+			 IFNULL(SUM(CASE WHEN status = :pending AND NOT ({nonSkippedFilterConditions}) AND size IS NULL THEN 1 ELSE 0 END), 0)
+			 FROM download_metadata
+			 """
+		);
+
+		cmd.AddAndSet(":pending", SqliteType.Integer, (int) DownloadStatus.Pending);
+		cmd.AddAndSet(":downloading", SqliteType.Integer, (int) DownloadStatus.Downloading);
+		cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
+
+		await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
+
+		if (!await reader.ReadAsync(cancellationToken)) {
+			return new DownloadStatusStatistics();
+		}
+
+		return new DownloadStatusStatistics {
+			PendingCount = reader.GetInt32(0),
+			PendingTotalSize = reader.GetUint64(1),
+			PendingWithUnknownSizeCount = reader.GetInt32(2),
+			SuccessfulCount = reader.GetInt32(3),
+			SuccessfulTotalSize = reader.GetUint64(4),
+			SuccessfulWithUnknownSizeCount = reader.GetInt32(5),
+			FailedCount = reader.GetInt32(6),
+			FailedTotalSize = reader.GetUint64(7),
+			FailedWithUnknownSizeCount = reader.GetInt32(8),
+			SkippedCount = reader.GetInt32(9),
+			SkippedTotalSize = reader.GetUint64(10),
+			SkippedWithUnknownSizeCount = reader.GetInt32(11)
+		};
+	}
+
+	public async IAsyncEnumerable<Data.Download> Get() {
+		await using var conn = await pool.Take();
+
+		await using var cmd = conn.Command("SELECT normalized_url, download_url, status, type, size FROM download_metadata");
 		await using var reader = await cmd.ExecuteReaderAsync();
 
-		while (reader.Read()) {
+		while (await reader.ReadAsync()) {
 			string normalizedUrl = reader.GetString(0);
 			string downloadUrl = reader.GetString(1);
 			var status = (DownloadStatus) reader.GetInt32(2);
-			ulong size = reader.GetUint64(3);
+			string? type = reader.IsDBNull(3) ? null : reader.GetString(3);
+			ulong? size = reader.IsDBNull(4) ? null : reader.GetUint64(4);
 
-			yield return new Data.Download(normalizedUrl, downloadUrl, status, size);
+			yield return new Data.Download(normalizedUrl, downloadUrl, status, type, size);
 		}
 	}
 
-	public async Task<Data.Download> HydrateWithData(Data.Download download) {
+	public async Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor) {
 		await using var conn = await pool.Take();
 
-		await using var cmd = conn.Command("SELECT blob FROM downloads WHERE normalized_url = :url");
-		cmd.AddAndSet(":url", SqliteType.Text, download.NormalizedUrl);
+		await using var cmd = conn.Command("SELECT rowid FROM download_blobs WHERE normalized_url = :normalized_url");
+		cmd.AddAndSet(":normalized_url", SqliteType.Text, normalizedUrl);
+		
+		long rowid;
+		
+		await using (var reader = await cmd.ExecuteReaderAsync()) {
+			if (!await reader.ReadAsync()) {
+				return false;
+			}
 
-		await using var reader = await cmd.ExecuteReaderAsync();
+			rowid = reader.GetInt64(0);
+		}
+		
+		await using (var blob = new SqliteBlob(conn.InnerConnection, "download_blobs", "blob", rowid, readOnly: true)) {
+			await dataProcessor(blob);
+		}
 
-		if (reader.Read() && !reader.IsDBNull(0)) {
-			return download.WithData((byte[]) reader["blob"]);
-		}
-		else {
-			return download;
-		}
+		return true;
 	}
 
-	public async Task<DownloadedAttachment?> GetDownloadedAttachment(string normalizedUrl) {
+	public async Task<bool> GetSuccessfulDownloadWithData(string normalizedUrl, Func<Data.Download, Stream, Task> dataProcessor) {
 		await using var conn = await pool.Take();
 
 		await using var cmd = conn.Command(
 			"""
-			SELECT a.type, d.blob FROM downloads d
-			LEFT JOIN attachments a ON d.normalized_url = a.normalized_url
-			WHERE d.normalized_url = :normalized_url AND d.status = :success AND d.blob IS NOT NULL
+			SELECT dm.download_url, dm.type, db.rowid FROM download_metadata dm
+			JOIN download_blobs db ON dm.normalized_url = db.normalized_url
+			WHERE dm.normalized_url = :normalized_url AND dm.status = :success IS NOT NULL
 			"""
 		);
 
 		cmd.AddAndSet(":normalized_url", SqliteType.Text, normalizedUrl);
 		cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
 
-		await using var reader = await cmd.ExecuteReaderAsync();
+		string downloadUrl;
+		string? type;
+		long rowid;
+		
+		await using (var reader = await cmd.ExecuteReaderAsync()) {
+			if (!await reader.ReadAsync()) {
+				return false;
+			}
 
-		if (!reader.Read()) {
-			return null;
+			downloadUrl = reader.GetString(0);
+			type = reader.IsDBNull(1) ? null : reader.GetString(1);
+			rowid = reader.GetInt64(2);
+		}
+		
+		await using (var blob = new SqliteBlob(conn.InnerConnection, "download_blobs", "blob", rowid, readOnly: true)) {
+			await dataProcessor(new Data.Download(normalizedUrl, downloadUrl, DownloadStatus.Success, type, (ulong) blob.Length), blob);
 		}
 
-		return new DownloadedAttachment {
-			Type = reader.IsDBNull(0) ? null : reader.GetString(0),
-			Data = (byte[]) reader["blob"],
-		};
+		return true;
 	}
 
-	public async Task<int> EnqueueDownloadItems(AttachmentFilter? filter, CancellationToken cancellationToken) {
-		await using var conn = await pool.Take();
+	public async IAsyncEnumerable<DownloadItem> PullPendingDownloadItems(int count, DownloadItemFilter filter, [EnumeratorCancellation] CancellationToken cancellationToken) {
+		filter.IncludeStatuses = [DownloadStatus.Pending];
+		filter.ExcludeStatuses = null;
 
-		await using var cmd = conn.Command(
-			$"""
-			 INSERT INTO downloads (normalized_url, download_url, status, size)
-			 SELECT a.normalized_url, a.download_url, :enqueued, MAX(a.size)
-			 FROM attachments a
-			 {filter.GenerateWhereClause("a")}
-			 GROUP BY a.normalized_url
-			 """
-		);
-
-		cmd.AddAndSet(":enqueued", SqliteType.Integer, (int) DownloadStatus.Enqueued);
-		return await cmd.ExecuteNonQueryAsync(cancellationToken);
-	}
-
-	public async IAsyncEnumerable<DownloadItem> PullEnqueuedDownloadItems(int count, [EnumeratorCancellation] CancellationToken cancellationToken) {
 		var found = new List<DownloadItem>();
 
 		await using var conn = await pool.Take();
 
-		await using (var cmd = conn.Command("SELECT normalized_url, download_url, size FROM downloads WHERE status = :enqueued LIMIT :limit")) {
-			cmd.AddAndSet(":enqueued", SqliteType.Integer, (int) DownloadStatus.Enqueued);
+		var sql = $"""
+		           SELECT normalized_url, download_url, type, size
+		           FROM download_metadata
+		           {filter.GenerateConditions().BuildWhereClause()}
+		           LIMIT :limit
+		           """;
+
+		await using (var cmd = conn.Command(sql)) {
 			cmd.AddAndSet(":limit", SqliteType.Integer, Math.Max(0, count));
 
 			await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
 
-			while (reader.Read()) {
+			while (await reader.ReadAsync(cancellationToken)) {
 				found.Add(new DownloadItem {
 					NormalizedUrl = reader.GetString(0),
 					DownloadUrl = reader.GetString(1),
-					Size = reader.GetUint64(2),
+					Type = reader.IsDBNull(2) ? null : reader.GetString(2),
+					Size = reader.IsDBNull(3) ? null : reader.GetUint64(3)
 				});
 			}
 		}
 
 		if (found.Count != 0) {
-			await using var cmd = conn.Command("UPDATE downloads SET status = :downloading WHERE normalized_url = :normalized_url AND status = :enqueued");
-			cmd.AddAndSet(":enqueued", SqliteType.Integer, (int) DownloadStatus.Enqueued);
+			await using var cmd = conn.Command("UPDATE download_metadata SET status = :downloading WHERE normalized_url = :normalized_url AND status = :pending");
+			cmd.AddAndSet(":pending", SqliteType.Integer, (int) DownloadStatus.Pending);
 			cmd.AddAndSet(":downloading", SqliteType.Integer, (int) DownloadStatus.Downloading);
 			cmd.Add(":normalized_url", SqliteType.Text);
 
@@ -214,17 +291,23 @@ sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepositor
 		}
 	}
 
-	public async Task RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {
-		await using (var conn = await pool.Take()) {
-			await conn.ExecuteAsync(
-				$"""
-				 -- noinspection SqlWithoutWhere
-				 DELETE FROM downloads
-				 {filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching)}
-				 """
-			);
-		}
+	public async Task MoveDownloadingItemsBackToQueue(CancellationToken cancellationToken) {
+		await using var conn = await pool.Take();
 
-		UpdateTotalCount();
+		await using var cmd = conn.Command("UPDATE download_metadata SET status = :pending WHERE status = :downloading");
+		cmd.AddAndSet(":pending", SqliteType.Integer, (int) DownloadStatus.Pending);
+		cmd.AddAndSet(":downloading", SqliteType.Integer, (int) DownloadStatus.Downloading);
+		await cmd.ExecuteNonQueryAsync(cancellationToken);
+	}
+
+	public async Task<int> RetryFailed(CancellationToken cancellationToken) {
+		await using var conn = await pool.Take();
+
+		await using var cmd = conn.Command("UPDATE download_metadata SET status = :pending WHERE status = :generic_error OR (status > :last_custom_code AND status != :success)");
+		cmd.AddAndSet(":pending", SqliteType.Integer, (int) DownloadStatus.Pending);
+		cmd.AddAndSet(":generic_error", SqliteType.Integer, (int) DownloadStatus.GenericError);
+		cmd.AddAndSet(":last_custom_code", SqliteType.Integer, (int) DownloadStatus.LastCustomCode);
+		cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
+		return await cmd.ExecuteNonQueryAsync(cancellationToken);
 	}
 }

app/Server/Database/Sqlite/Repositories/SqliteMessageRepository.cs

@@ -7,17 +7,21 @@ using DHT.Server.Data;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database.Repositories;
 using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Download;
+using DHT.Utils.Logging;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
 sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository {
+	private static readonly Log Log = Log.ForType<SqliteMessageRepository>();
+	
 	private readonly SqliteConnectionPool pool;
-	private readonly SqliteAttachmentRepository attachments;
+	private readonly SqliteDownloadRepository downloads;
 
-	public SqliteMessageRepository(SqliteConnectionPool pool, SqliteAttachmentRepository attachments) {
+	public SqliteMessageRepository(SqliteConnectionPool pool, SqliteDownloadRepository downloads) : base(Log) {
 		this.pool = pool;
-		this.attachments = attachments;
+		this.downloads = downloads;
 	}
 
 	public async Task Add(IReadOnlyList<Message> messages) {
@@ -34,10 +38,8 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			await cmd.ExecuteNonQueryAsync();
 		}
 
-		bool addedAttachments = false;
-
 		await using (var conn = await pool.Take()) {
-			await using var tx = await conn.BeginTransactionAsync();
+			await conn.BeginTransactionAsync();
 
 			await using var messageCmd = conn.Upsert("messages", [
 				("message_id", SqliteType.Integer),
@@ -88,6 +90,8 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 				("emoji_flags", SqliteType.Integer),
 				("count", SqliteType.Integer)
 			]);
+			
+			await using var downloadCollector = new SqliteDownloadRepository.NewDownloadCollector(downloads, conn);
 
 			foreach (var message in messages) {
 				object messageId = message.Id;
@@ -119,8 +123,6 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 				}
 
 				if (!message.Attachments.IsEmpty) {
-					addedAttachments = true;
-
 					foreach (var attachment in message.Attachments) {
 						attachmentCmd.Set(":message_id", messageId);
 						attachmentCmd.Set(":attachment_id", attachment.Id);
@@ -132,6 +134,8 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 						attachmentCmd.Set(":width", attachment.Width);
 						attachmentCmd.Set(":height", attachment.Height);
 						await attachmentCmd.ExecuteNonQueryAsync();
+						
+						await downloadCollector.Add(DownloadLinkExtractor.FromAttachment(attachment));
 					}
 				}
 
@@ -140,6 +144,10 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 						embedCmd.Set(":message_id", messageId);
 						embedCmd.Set(":json", embed.Json);
 						await embedCmd.ExecuteNonQueryAsync();
+
+						if (DownloadLinkExtractor.TryFromEmbedJson(embed.Json) is {} download) {
+							await downloadCollector.Add(download);
+						}
 					}
 				}
 
@@ -151,18 +159,19 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 						reactionCmd.Set(":emoji_flags", (int) reaction.EmojiFlags);
 						reactionCmd.Set(":count", reaction.Count);
 						await reactionCmd.ExecuteNonQueryAsync();
+
+						if (reaction.EmojiId is {} emojiId) {
+							await downloadCollector.Add(DownloadLinkExtractor.FromEmoji(emojiId, reaction.EmojiFlags));
+						}
 					}
 				}
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
+			downloadCollector.OnCommitted();
 		}
 
 		UpdateTotalCount();
-
-		if (addedAttachments) {
-			attachments.UpdateTotalCount();
-		}
 	}
 
 	public override Task<long> Count(CancellationToken cancellationToken) {
@@ -171,14 +180,14 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 	
 	public async Task<long> Count(MessageFilter? filter, CancellationToken cancellationToken) {
 		await using var conn = await pool.Take();
-		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM messages" + filter.GenerateWhereClause(), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
+		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM messages" + filter.GenerateConditions().BuildWhereClause(), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
 	}
 
-	private sealed class MesageToManyCommand<T> : IAsyncDisposable {
+	private sealed class MessageToManyCommand<T> : IAsyncDisposable {
 		private readonly SqliteCommand cmd;
 		private readonly Func<SqliteDataReader, T> readItem;
 
-		public MesageToManyCommand(ISqliteConnection conn, string sql, Func<SqliteDataReader, T> readItem) {
+		public MessageToManyCommand(ISqliteConnection conn, string sql, Func<SqliteDataReader, T> readItem) {
 			this.cmd = conn.Command(sql);
 			this.cmd.Add(":message_id", SqliteType.Integer);
 
@@ -214,7 +223,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			WHERE message_id = :message_id
 			""";
 
-		await using var attachmentCmd = new MesageToManyCommand<Attachment>(conn, AttachmentSql, static reader => new Attachment {
+		await using var attachmentCmd = new MessageToManyCommand<Attachment>(conn, AttachmentSql, static reader => new Attachment {
 			Id = reader.GetUint64(0),
 			Name = reader.GetString(1),
 			Type = reader.IsDBNull(2) ? null : reader.GetString(2),
@@ -232,7 +241,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			WHERE message_id = :message_id
 			""";
 
-		await using var embedCmd = new MesageToManyCommand<Embed>(conn, EmbedSql, static reader => new Embed {
+		await using var embedCmd = new MessageToManyCommand<Embed>(conn, EmbedSql, static reader => new Embed {
 			Json = reader.GetString(0)
 		});
 
@@ -243,7 +252,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			WHERE message_id = :message_id
 			""";
 
-		await using var reactionsCmd = new MesageToManyCommand<Reaction>(conn, ReactionSql, static reader => new Reaction {
+		await using var reactionsCmd = new MessageToManyCommand<Reaction>(conn, ReactionSql, static reader => new Reaction {
 			EmojiId = reader.IsDBNull(0) ? null : reader.GetUint64(0),
 			EmojiName = reader.IsDBNull(1) ? null : reader.GetString(1),
 			EmojiFlags = (EmojiFlags) reader.GetInt16(2),
@@ -256,7 +265,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			 FROM messages m
 			 LEFT JOIN edit_timestamps et ON m.message_id = et.message_id
 			 LEFT JOIN replied_to rt ON m.message_id = rt.message_id
-			 {filter.GenerateWhereClause("m")}
+			 {filter.GenerateConditions("m").BuildWhereClause()}
 			 """
 		);
 
@@ -283,7 +292,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 	public async IAsyncEnumerable<ulong> GetIds(MessageFilter? filter) {
 		await using var conn = await pool.Take();
 		
-		await using var cmd = conn.Command("SELECT message_id FROM messages" + filter.GenerateWhereClause());
+		await using var cmd = conn.Command("SELECT message_id FROM messages" + filter.GenerateConditions().BuildWhereClause());
 		await using var reader = await cmd.ExecuteReaderAsync();
 
 		while (await reader.ReadAsync()) {
@@ -297,7 +306,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 				$"""
 				 -- noinspection SqlWithoutWhere
 				 DELETE FROM messages
-				 {filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching)}
+				 {filter.GenerateConditions(invert: mode == FilterRemovalMode.KeepMatching).BuildWhereClause()}
 				 """
 			);
 		}

app/Server/Database/Sqlite/Repositories/SqliteServerRepository.cs

@@ -4,21 +4,24 @@ using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Database.Repositories;
 using DHT.Server.Database.Sqlite.Utils;
+using DHT.Utils.Logging;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
 sealed class SqliteServerRepository : BaseSqliteRepository, IServerRepository {
+	private static readonly Log Log = Log.ForType<SqliteServerRepository>();
+	
 	private readonly SqliteConnectionPool pool;
 
-	public SqliteServerRepository(SqliteConnectionPool pool) {
+	public SqliteServerRepository(SqliteConnectionPool pool) : base(Log) {
 		this.pool = pool;
 	}
 
 	public async Task Add(IReadOnlyList<Data.Server> servers) {
-		await using var conn = await pool.Take();
-
-		await using (var tx = await conn.BeginTransactionAsync()) {
+		await using (var conn = await pool.Take()) {
+			await conn.BeginTransactionAsync();
+			
 			await using var cmd = conn.Upsert("servers", [
 				("id", SqliteType.Integer),
 				("name", SqliteType.Text),
@@ -32,7 +35,7 @@ sealed class SqliteServerRepository : BaseSqliteRepository, IServerRepository {
 				await cmd.ExecuteNonQueryAsync();
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 		}
 
 		UpdateTotalCount();
@@ -49,7 +52,7 @@ sealed class SqliteServerRepository : BaseSqliteRepository, IServerRepository {
 		await using var cmd = conn.Command("SELECT id, name, type FROM servers");
 		await using var reader = await cmd.ExecuteReaderAsync();
 
-		while (reader.Read()) {
+		while (await reader.ReadAsync()) {
 			yield return new Data.Server {
 				Id = reader.GetUint64(0),
 				Name = reader.GetString(1),

app/Server/Database/Sqlite/Repositories/SqliteUserRepository.cs

@@ -4,21 +4,27 @@ using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Database.Repositories;
 using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Download;
+using DHT.Utils.Logging;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
 sealed class SqliteUserRepository : BaseSqliteRepository, IUserRepository {
+	private static readonly Log Log = Log.ForType<SqliteUserRepository>();
+	
 	private readonly SqliteConnectionPool pool;
-	
-	public SqliteUserRepository(SqliteConnectionPool pool) {
+	private readonly SqliteDownloadRepository downloads;
+
+	public SqliteUserRepository(SqliteConnectionPool pool, SqliteDownloadRepository downloads) : base(Log) {
 		this.pool = pool;
+		this.downloads = downloads;
 	}
-	
+
 	public async Task Add(IReadOnlyList<User> users) {
 		await using (var conn = await pool.Take()) {
-			await using var tx = await conn.BeginTransactionAsync();
-			
+			await conn.BeginTransactionAsync();
+
 			await using var cmd = conn.Upsert("users", [
 				("id", SqliteType.Integer),
 				("name", SqliteType.Text),
@@ -26,15 +32,22 @@ sealed class SqliteUserRepository : BaseSqliteRepository, IUserRepository {
 				("discriminator", SqliteType.Text)
 			]);
 
+			await using var downloadCollector = new SqliteDownloadRepository.NewDownloadCollector(downloads, conn);
+			
 			foreach (var user in users) {
 				cmd.Set(":id", user.Id);
 				cmd.Set(":name", user.Name);
 				cmd.Set(":avatar_url", user.AvatarUrl);
 				cmd.Set(":discriminator", user.Discriminator);
 				await cmd.ExecuteNonQueryAsync();
+
+				if (user.AvatarUrl is {} avatarUrl) {
+					await downloadCollector.Add(DownloadLinkExtractor.FromUserAvatar(user.Id, avatarUrl));
+				}
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
+			downloadCollector.OnCommitted();
 		}
 
 		UpdateTotalCount();
@@ -47,11 +60,11 @@ sealed class SqliteUserRepository : BaseSqliteRepository, IUserRepository {
 
 	public async IAsyncEnumerable<User> Get() {
 		await using var conn = await pool.Take();
-		
+
 		await using var cmd = conn.Command("SELECT id, name, avatar_url, discriminator FROM users");
 		await using var reader = await cmd.ExecuteReaderAsync();
 
-		while (reader.Read()) {
+		while (await reader.ReadAsync()) {
 			yield return new User {
 				Id = reader.GetUint64(0),
 				Name = reader.GetString(1),

app/Server/Database/Sqlite/Schema.cs

@@ -1,358 +0,0 @@
-using System.Collections.Generic;
-using System.Data.Common;
-using System.Threading.Tasks;
-using DHT.Server.Database.Exceptions;
-using DHT.Server.Database.Sqlite.Utils;
-using DHT.Server.Download;
-using DHT.Utils.Logging;
-using Microsoft.Data.Sqlite;
-
-namespace DHT.Server.Database.Sqlite;
-
-sealed class Schema {
-	internal const int Version = 6;
-
-	private static readonly Log Log = Log.ForType<Schema>();
-
-	private readonly ISqliteConnection conn;
-
-	public Schema(ISqliteConnection conn) {
-		this.conn = conn;
-	}
-
-	public async Task<bool> Setup(ISchemaUpgradeCallbacks callbacks) {
-		await conn.ExecuteAsync("CREATE TABLE IF NOT EXISTS metadata (key TEXT PRIMARY KEY, value TEXT)");
-
-		var dbVersionStr = await conn.ExecuteReaderAsync("SELECT value FROM metadata WHERE key = 'version'", static reader => reader?.GetString(0));
-		if (dbVersionStr == null) {
-			await InitializeSchemas();
-		}
-		else if (!int.TryParse(dbVersionStr, out int dbVersion) || dbVersion < 1) {
-			throw new InvalidDatabaseVersionException(dbVersionStr);
-		}
-		else if (dbVersion > Version) {
-			throw new DatabaseTooNewException(dbVersion);
-		}
-		else if (dbVersion < Version) {
-			var proceed = await callbacks.CanUpgrade();
-			if (!proceed) {
-				return false;
-			}
-
-			await callbacks.Start(Version - dbVersion, async reporter => await UpgradeSchemas(dbVersion, reporter));
-		}
-
-		return true;
-	}
-
-	private async Task InitializeSchemas() {
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE users (
-		                        	id            INTEGER PRIMARY KEY NOT NULL,
-		                        	name          TEXT NOT NULL,
-		                        	avatar_url    TEXT,
-		                        	discriminator TEXT
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE servers (
-		                        	id   INTEGER PRIMARY KEY NOT NULL,
-		                        	name TEXT NOT NULL,
-		                        	type TEXT NOT NULL
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE channels (
-		                        	id        INTEGER PRIMARY KEY NOT NULL,
-		                        	server    INTEGER NOT NULL,
-		                        	name      TEXT NOT NULL,
-		                        	parent_id INTEGER,
-		                        	position  INTEGER,
-		                        	topic     TEXT,
-		                        	nsfw      INTEGER
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE messages (
-		                        	message_id INTEGER PRIMARY KEY NOT NULL,
-		                        	sender_id  INTEGER NOT NULL,
-		                        	channel_id INTEGER NOT NULL,
-		                        	text       TEXT NOT NULL,
-		                        	timestamp  INTEGER NOT NULL
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE attachments (
-		                        	message_id     INTEGER NOT NULL,
-		                        	attachment_id  INTEGER NOT NULL PRIMARY KEY NOT NULL,
-		                        	name           TEXT NOT NULL,
-		                        	type           TEXT,
-		                        	normalized_url TEXT NOT NULL,
-		                        	download_url   TEXT,
-		                        	size           INTEGER NOT NULL,
-		                        	width          INTEGER,
-		                        	height         INTEGER
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE embeds (
-		                        	message_id INTEGER NOT NULL,
-		                        	json       TEXT NOT NULL
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE downloads (
-		                        	normalized_url TEXT NOT NULL PRIMARY KEY,
-		                        	download_url   TEXT,
-		                        	status         INTEGER NOT NULL,
-		                        	size           INTEGER NOT NULL,
-		                        	blob           BLOB
-		                        )
-		                        """);
-
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE reactions (
-		                        	message_id  INTEGER NOT NULL,
-		                        	emoji_id    INTEGER,
-		                        	emoji_name  TEXT,
-		                        	emoji_flags INTEGER NOT NULL,
-		                        	count       INTEGER NOT NULL
-		                        )
-		                        """);
-
-		await CreateMessageEditTimestampTable();
-		await CreateMessageRepliedToTable();
-
-		await conn.ExecuteAsync("CREATE INDEX attachments_message_ix ON attachments(message_id)");
-		await conn.ExecuteAsync("CREATE INDEX embeds_message_ix ON embeds(message_id)");
-		await conn.ExecuteAsync("CREATE INDEX reactions_message_ix ON reactions(message_id)");
-
-		await conn.ExecuteAsync("INSERT INTO metadata (key, value) VALUES ('version', " + Version + ")");
-	}
-
-	private async Task CreateMessageEditTimestampTable() {
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE edit_timestamps (
-		                        	message_id     INTEGER PRIMARY KEY NOT NULL,
-		                        	edit_timestamp INTEGER NOT NULL
-		                        )
-		                        """);
-	}
-
-	private async Task CreateMessageRepliedToTable() {
-		await conn.ExecuteAsync("""
-		                        CREATE TABLE replied_to (
-		                        	message_id    INTEGER PRIMARY KEY NOT NULL,
-		                        	replied_to_id INTEGER NOT NULL
-		                        )
-		                        """);
-	}
-
-	private async Task NormalizeAttachmentUrls(ISchemaUpgradeCallbacks.IProgressReporter reporter) {
-		await reporter.SubWork("Preparing attachments...", 0, 0);
-
-		var normalizedUrls = new Dictionary<long, string>();
-
-		await using (var selectCmd = conn.Command("SELECT attachment_id, url FROM attachments")) {
-			await using var reader = await selectCmd.ExecuteReaderAsync();
-
-			while (reader.Read()) {
-				var attachmentId = reader.GetInt64(0);
-				var originalUrl = reader.GetString(1);
-				normalizedUrls[attachmentId] = DiscordCdn.NormalizeUrl(originalUrl);
-			}
-		}
-
-		await using var tx = await conn.BeginTransactionAsync();
-
-		int totalUrls = normalizedUrls.Count;
-		int processedUrls = -1;
-
-		await using (var updateCmd = conn.Command("UPDATE attachments SET download_url = url, url = :normalized_url WHERE attachment_id = :attachment_id")) {
-			updateCmd.Add(":attachment_id", SqliteType.Integer);
-			updateCmd.Add(":normalized_url", SqliteType.Text);
-
-			foreach (var (attachmentId, normalizedUrl) in normalizedUrls) {
-				if (++processedUrls % 1000 == 0) {
-					await reporter.SubWork("Updating URLs...", processedUrls, totalUrls);
-				}
-
-				updateCmd.Set(":attachment_id", attachmentId);
-				updateCmd.Set(":normalized_url", normalizedUrl);
-				updateCmd.ExecuteNonQuery();
-			}
-		}
-
-		await reporter.SubWork("Updating URLs...", totalUrls, totalUrls);
-
-		await tx.CommitAsync();
-	}
-
-	private async Task NormalizeDownloadUrls(ISchemaUpgradeCallbacks.IProgressReporter reporter) {
-		await reporter.SubWork("Preparing downloads...", 0, 0);
-
-		var normalizedUrlsToOriginalUrls = new Dictionary<string, string>();
-		var duplicateUrlsToDelete = new HashSet<string>();
-
-		await using (var selectCmd = conn.Command("SELECT url FROM downloads ORDER BY CASE WHEN status = 200 THEN 0 ELSE 1 END")) {
-			await using var reader = await selectCmd.ExecuteReaderAsync();
-
-			while (reader.Read()) {
-				var originalUrl = reader.GetString(0);
-				var normalizedUrl = DiscordCdn.NormalizeUrl(originalUrl);
-
-				if (!normalizedUrlsToOriginalUrls.TryAdd(normalizedUrl, originalUrl)) {
-					duplicateUrlsToDelete.Add(originalUrl);
-				}
-			}
-		}
-
-		await conn.ExecuteAsync("PRAGMA cache_size = -20000");
-
-		DbTransaction tx;
-
-		await using (tx = await conn.BeginTransactionAsync()) {
-			await reporter.SubWork("Deleting duplicates...", 0, 0);
-
-			await using (var deleteCmd = conn.Delete("downloads", ("url", SqliteType.Text))) {
-				foreach (var duplicateUrl in duplicateUrlsToDelete) {
-					deleteCmd.Set(":url", duplicateUrl);
-					deleteCmd.ExecuteNonQuery();
-				}
-			}
-
-			await tx.CommitAsync();
-		}
-
-		int totalUrls = normalizedUrlsToOriginalUrls.Count;
-		int processedUrls = -1;
-
-		tx = await conn.BeginTransactionAsync();
-
-		await using (var updateCmd = conn.Command("UPDATE downloads SET download_url = :download_url, url = :normalized_url WHERE url = :download_url")) {
-			updateCmd.Add(":normalized_url", SqliteType.Text);
-			updateCmd.Add(":download_url", SqliteType.Text);
-
-			foreach (var (normalizedUrl, downloadUrl) in normalizedUrlsToOriginalUrls) {
-				if (++processedUrls % 100 == 0) {
-					await reporter.SubWork("Updating URLs...", processedUrls, totalUrls);
-
-					// Not proper way of dealing with transactions, but it avoids a long commit at the end.
-					// Schema upgrades are already non-atomic anyways, so this doesn't make it worse.
-					await tx.CommitAsync();
-					await tx.DisposeAsync();
-
-					tx = await conn.BeginTransactionAsync();
-					updateCmd.Transaction = (SqliteTransaction) tx;
-				}
-
-				updateCmd.Set(":normalized_url", normalizedUrl);
-				updateCmd.Set(":download_url", downloadUrl);
-				updateCmd.ExecuteNonQuery();
-			}
-		}
-
-		await reporter.SubWork("Updating URLs...", totalUrls, totalUrls);
-
-		await tx.CommitAsync();
-		await tx.DisposeAsync();
-
-		await conn.ExecuteAsync("PRAGMA cache_size = -2000");
-	}
-
-	private async Task UpgradeSchemas(int dbVersion, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
-		var perf = Log.Start("from version " + dbVersion);
-
-		await conn.ExecuteAsync("UPDATE metadata SET value = " + Version + " WHERE key = 'version'");
-
-		if (dbVersion <= 1) {
-			await reporter.MainWork("Applying schema changes...", 0, 1);
-			await conn.ExecuteAsync("ALTER TABLE channels ADD parent_id INTEGER");
-
-			perf.Step("Upgrade to version 2");
-			await reporter.NextVersion();
-		}
-
-		if (dbVersion <= 2) {
-			await reporter.MainWork("Applying schema changes...", 0, 1);
-
-			await CreateMessageEditTimestampTable();
-			await CreateMessageRepliedToTable();
-
-			await conn.ExecuteAsync("""
-			                        INSERT INTO edit_timestamps (message_id, edit_timestamp)
-			                        SELECT message_id, edit_timestamp
-			                        FROM messages
-			                        WHERE edit_timestamp IS NOT NULL
-			                        """);
-
-			await conn.ExecuteAsync("""
-			                        INSERT INTO replied_to (message_id, replied_to_id)
-			                        SELECT message_id, replied_to_id
-			                        FROM messages
-			                        WHERE replied_to_id IS NOT NULL
-			                        """);
-
-			await conn.ExecuteAsync("ALTER TABLE messages DROP COLUMN replied_to_id");
-			await conn.ExecuteAsync("ALTER TABLE messages DROP COLUMN edit_timestamp");
-
-			perf.Step("Upgrade to version 3");
-
-			await reporter.MainWork("Vacuuming the database...", 1, 1);
-			await conn.ExecuteAsync("VACUUM");
-			perf.Step("Vacuum");
-
-			await reporter.NextVersion();
-		}
-
-		if (dbVersion <= 3) {
-			await conn.ExecuteAsync("""
-			                        CREATE TABLE downloads (
-			                        	url    TEXT NOT NULL PRIMARY KEY,
-			                        	status INTEGER NOT NULL,
-			                        	size   INTEGER NOT NULL,
-			                        	blob   BLOB
-			                        )
-			                        """);
-
-			perf.Step("Upgrade to version 4");
-			await reporter.NextVersion();
-		}
-
-		if (dbVersion <= 4) {
-			await reporter.MainWork("Applying schema changes...", 0, 1);
-			await conn.ExecuteAsync("ALTER TABLE attachments ADD width INTEGER");
-			await conn.ExecuteAsync("ALTER TABLE attachments ADD height INTEGER");
-
-			perf.Step("Upgrade to version 5");
-			await reporter.NextVersion();
-		}
-
-		if (dbVersion <= 5) {
-			await reporter.MainWork("Applying schema changes...", 0, 3);
-			await conn.ExecuteAsync("ALTER TABLE attachments ADD download_url TEXT");
-			await conn.ExecuteAsync("ALTER TABLE downloads ADD download_url TEXT");
-
-			await reporter.MainWork("Updating attachments...", 1, 3);
-			await NormalizeAttachmentUrls(reporter);
-
-			await reporter.MainWork("Updating downloads...", 2, 3);
-			await NormalizeDownloadUrls(reporter);
-
-			await reporter.MainWork("Applying schema changes...", 3, 3);
-			await conn.ExecuteAsync("ALTER TABLE attachments RENAME COLUMN url TO normalized_url");
-			await conn.ExecuteAsync("ALTER TABLE downloads RENAME COLUMN url TO normalized_url");
-
-			perf.Step("Upgrade to version 6");
-			await reporter.NextVersion();
-		}
-
-		perf.End();
-	}
-}

app/Server/Database/Sqlite/Schema/ISchemaUpgrade.cs

@@ -0,0 +1,8 @@
+using System.Threading.Tasks;
+using DHT.Server.Database.Sqlite.Utils;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+interface ISchemaUpgrade {
+	Task Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter);
+}

app/Server/Database/Sqlite/Schema/ISchemaUpgradeCallbacks.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Threading.Tasks;
 
-namespace DHT.Server.Database.Sqlite.Utils;
+namespace DHT.Server.Database.Sqlite.Schema;
 
 public interface ISchemaUpgradeCallbacks {
 	Task<bool> CanUpgrade();

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo2.cs

@@ -0,0 +1,11 @@
+using System.Threading.Tasks;
+using DHT.Server.Database.Sqlite.Utils;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+sealed class SqliteSchemaUpgradeTo2 : ISchemaUpgrade {
+	async Task ISchemaUpgrade.Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.MainWork("Applying schema changes...", 0, 1);
+		await conn.ExecuteAsync("ALTER TABLE channels ADD parent_id INTEGER");
+	}
+}

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo3.cs

@@ -0,0 +1,33 @@
+using System.Threading.Tasks;
+using DHT.Server.Database.Sqlite.Utils;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+sealed class SqliteSchemaUpgradeTo3 : ISchemaUpgrade {
+	async Task ISchemaUpgrade.Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.MainWork("Applying schema changes...", 0, 1);
+
+		await SqliteSchema.CreateMessageEditTimestampTable(conn);
+		await SqliteSchema.CreateMessageRepliedToTable(conn);
+
+		await conn.ExecuteAsync("""
+		                        INSERT INTO edit_timestamps (message_id, edit_timestamp)
+		                        SELECT message_id, edit_timestamp
+		                        FROM messages
+		                        WHERE edit_timestamp IS NOT NULL
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        INSERT INTO replied_to (message_id, replied_to_id)
+		                        SELECT message_id, replied_to_id
+		                        FROM messages
+		                        WHERE replied_to_id IS NOT NULL
+		                        """);
+
+		await conn.ExecuteAsync("ALTER TABLE messages DROP COLUMN replied_to_id");
+		await conn.ExecuteAsync("ALTER TABLE messages DROP COLUMN edit_timestamp");
+
+		await reporter.MainWork("Vacuuming the database...", 1, 1);
+		await conn.ExecuteAsync("VACUUM");
+	}
+}

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo4.cs

@@ -0,0 +1,19 @@
+using System.Threading.Tasks;
+using DHT.Server.Database.Sqlite.Utils;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+sealed class SqliteSchemaUpgradeTo4 : ISchemaUpgrade {
+	async Task ISchemaUpgrade.Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.MainWork("Applying schema changes...", 0, 1);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE downloads (
+		                        	url    TEXT NOT NULL PRIMARY KEY,
+		                        	status INTEGER NOT NULL,
+		                        	size   INTEGER NOT NULL,
+		                        	blob   BLOB
+		                        )
+		                        """);
+	}
+}

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo5.cs

@@ -0,0 +1,12 @@
+using System.Threading.Tasks;
+using DHT.Server.Database.Sqlite.Utils;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+sealed class SqliteSchemaUpgradeTo5 : ISchemaUpgrade {
+	async Task ISchemaUpgrade.Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.MainWork("Applying schema changes...", 0, 1);
+		await conn.ExecuteAsync("ALTER TABLE attachments ADD width INTEGER");
+		await conn.ExecuteAsync("ALTER TABLE attachments ADD height INTEGER");
+	}
+}

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo6.cs

@@ -0,0 +1,132 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Download;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
+	async Task ISchemaUpgrade.Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.MainWork("Applying schema changes...", 0, 3);
+		await conn.ExecuteAsync("ALTER TABLE attachments ADD download_url TEXT");
+		await conn.ExecuteAsync("ALTER TABLE downloads ADD download_url TEXT");
+
+		await reporter.MainWork("Updating attachments...", 1, 3);
+		await NormalizeAttachmentUrls(conn, reporter);
+
+		await reporter.MainWork("Updating downloads...", 2, 3);
+		await NormalizeDownloadUrls(conn, reporter);
+
+		await reporter.MainWork("Applying schema changes...", 3, 3);
+		await conn.ExecuteAsync("ALTER TABLE attachments RENAME COLUMN url TO normalized_url");
+		await conn.ExecuteAsync("ALTER TABLE downloads RENAME COLUMN url TO normalized_url");
+	}
+
+	private async Task NormalizeAttachmentUrls(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.SubWork("Preparing attachments...", 0, 0);
+
+		var normalizedUrls = new Dictionary<long, string>();
+
+		await using (var selectCmd = conn.Command("SELECT attachment_id, url FROM attachments")) {
+			await using var reader = await selectCmd.ExecuteReaderAsync();
+
+			while (await reader.ReadAsync()) {
+				var attachmentId = reader.GetInt64(0);
+				var originalUrl = reader.GetString(1);
+				normalizedUrls[attachmentId] = DiscordCdn.NormalizeUrl(originalUrl);
+			}
+		}
+
+		await conn.BeginTransactionAsync();
+
+		int totalUrls = normalizedUrls.Count;
+		int processedUrls = -1;
+
+		await using (var updateCmd = conn.Command("UPDATE attachments SET download_url = url, url = :normalized_url WHERE attachment_id = :attachment_id")) {
+			updateCmd.Add(":attachment_id", SqliteType.Integer);
+			updateCmd.Add(":normalized_url", SqliteType.Text);
+
+			foreach (var (attachmentId, normalizedUrl) in normalizedUrls) {
+				if (++processedUrls % 1000 == 0) {
+					await reporter.SubWork("Updating URLs...", processedUrls, totalUrls);
+				}
+
+				updateCmd.Set(":attachment_id", attachmentId);
+				updateCmd.Set(":normalized_url", normalizedUrl);
+				await updateCmd.ExecuteNonQueryAsync();
+			}
+		}
+
+		await reporter.SubWork("Updating URLs...", totalUrls, totalUrls);
+
+		await conn.CommitTransactionAsync();
+	}
+
+	private async Task NormalizeDownloadUrls(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.SubWork("Preparing downloads...", 0, 0);
+
+		var normalizedUrlsToOriginalUrls = new Dictionary<string, string>();
+		var duplicateUrlsToDelete = new HashSet<string>();
+
+		await using (var selectCmd = conn.Command("SELECT url FROM downloads ORDER BY CASE WHEN status = 200 THEN 0 ELSE 1 END")) {
+			await using var reader = await selectCmd.ExecuteReaderAsync();
+
+			while (await reader.ReadAsync()) {
+				var originalUrl = reader.GetString(0);
+				var normalizedUrl = DiscordCdn.NormalizeUrl(originalUrl);
+
+				if (!normalizedUrlsToOriginalUrls.TryAdd(normalizedUrl, originalUrl)) {
+					duplicateUrlsToDelete.Add(originalUrl);
+				}
+			}
+		}
+
+		await conn.ExecuteAsync("PRAGMA cache_size = -20000");
+		await conn.BeginTransactionAsync();
+		
+		await reporter.SubWork("Deleting duplicates...", 0, 0);
+
+		await using (var deleteCmd = conn.Delete("downloads", ("url", SqliteType.Text))) {
+			foreach (var duplicateUrl in duplicateUrlsToDelete) {
+				deleteCmd.Set(":url", duplicateUrl);
+				await deleteCmd.ExecuteNonQueryAsync();
+			}
+		}
+
+		await conn.CommitTransactionAsync();
+
+		int totalUrls = normalizedUrlsToOriginalUrls.Count;
+		int processedUrls = -1;
+
+		await conn.BeginTransactionAsync();
+
+		await using (var updateCmd = conn.Command("UPDATE downloads SET download_url = :download_url, url = :normalized_url WHERE url = :download_url")) {
+			updateCmd.Add(":normalized_url", SqliteType.Text);
+			updateCmd.Add(":download_url", SqliteType.Text);
+
+			foreach (var (normalizedUrl, downloadUrl) in normalizedUrlsToOriginalUrls) {
+				if (++processedUrls % 100 == 0) {
+					await reporter.SubWork("Updating URLs...", processedUrls, totalUrls);
+
+					// Not proper way of dealing with transactions, but it avoids a long commit at the end.
+					// Schema upgrades are already non-atomic anyways, so this doesn't make it worse.
+					await conn.CommitTransactionAsync();
+
+					await conn.BeginTransactionAsync();
+					conn.AssignActiveTransaction(updateCmd);
+				}
+
+				updateCmd.Set(":normalized_url", normalizedUrl);
+				updateCmd.Set(":download_url", downloadUrl);
+				await updateCmd.ExecuteNonQueryAsync();
+			}
+		}
+
+		await reporter.SubWork("Updating URLs...", totalUrls, totalUrls);
+
+		await conn.CommitTransactionAsync();
+
+		await conn.ExecuteAsync("PRAGMA cache_size = -2000");
+	}
+}

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo7.cs

@@ -0,0 +1,153 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Download;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Schema;
+
+sealed class SqliteSchemaUpgradeTo7 : ISchemaUpgrade {
+	async Task ISchemaUpgrade.Run(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.MainWork("Applying schema changes...", 0, 6);
+		await SqliteSchema.CreateDownloadTables(conn);
+
+		await reporter.MainWork("Migrating download metadata...", 1, 6);
+		await conn.ExecuteAsync("INSERT INTO download_metadata (normalized_url, download_url, status, size) SELECT normalized_url, download_url, status, size FROM downloads");
+
+		await reporter.MainWork("Merging attachment metadata...", 2, 6);
+		await conn.ExecuteAsync("UPDATE download_metadata SET type = (SELECT type FROM attachments WHERE download_metadata.normalized_url = attachments.normalized_url)");
+
+		await reporter.MainWork("Migrating downloaded files...", 3, 6);
+		await MigrateDownloadBlobsToNewTable(conn, reporter);
+
+		await reporter.MainWork("Applying schema changes...", 4, 6);
+		await conn.ExecuteAsync("DROP TABLE downloads");
+
+		await reporter.MainWork("Discovering downloadable links...", 5, 6);
+		await DiscoverDownloadableLinks(conn, reporter);
+	}
+
+	private async Task MigrateDownloadBlobsToNewTable(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.SubWork("Listing downloaded files...", 0, 0);
+
+		var urlsToMigrate = await GetDownloadedFileUrls(conn);
+		int totalFiles = urlsToMigrate.Count;
+		int processedFiles = -1;
+
+		await reporter.SubWork("Processing downloaded files...", 0, totalFiles);
+
+		await conn.BeginTransactionAsync();
+
+		await using (var insertCmd = conn.Command("INSERT INTO download_blobs (normalized_url, blob) SELECT normalized_url, blob FROM downloads WHERE normalized_url = :normalized_url"))
+		await using (var deleteCmd = conn.Command("DELETE FROM downloads WHERE normalized_url = :normalized_url")) {
+			insertCmd.Add(":normalized_url", SqliteType.Text);
+			deleteCmd.Add(":normalized_url", SqliteType.Text);
+
+			foreach (var url in urlsToMigrate) {
+				if (++processedFiles % 10 == 0) {
+					await reporter.SubWork("Processing downloaded files...", processedFiles, totalFiles);
+
+					// Not proper way of dealing with transactions, but it avoids a long commit at the end.
+					// Schema upgrades are already non-atomic anyways, so this doesn't make it worse.
+					await conn.CommitTransactionAsync();
+					
+					await conn.BeginTransactionAsync();
+					conn.AssignActiveTransaction(insertCmd);
+					conn.AssignActiveTransaction(deleteCmd);
+				}
+
+				insertCmd.Set(":normalized_url", url);
+				await insertCmd.ExecuteNonQueryAsync();
+
+				deleteCmd.Set(":normalized_url", url);
+				await deleteCmd.ExecuteNonQueryAsync();
+			}
+		}
+
+		await reporter.SubWork("Processing downloaded files...", totalFiles, totalFiles);
+
+		await conn.CommitTransactionAsync();
+	}
+
+	private async Task<List<string>> GetDownloadedFileUrls(ISqliteConnection conn) {
+		var urls = new List<string>();
+
+		await using var selectCmd = conn.Command("SELECT normalized_url FROM downloads WHERE blob IS NOT NULL");
+		await using var reader = await selectCmd.ExecuteReaderAsync();
+
+		while (await reader.ReadAsync()) {
+			urls.Add(reader.GetString(0));
+		}
+
+		return urls;
+	}
+
+	private async Task DiscoverDownloadableLinks(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		await reporter.SubWork("Processing attachments...", 0, 4);
+
+		await using (var cmd = conn.Command("""
+		                                    INSERT OR IGNORE INTO download_metadata (normalized_url, download_url, status, type, size)
+		                                    SELECT a.normalized_url, a.download_url, :pending, a.type, MAX(a.size)
+		                                    FROM attachments a
+		                                    GROUP BY a.normalized_url
+		                                    """)) {
+			cmd.AddAndSet(":pending", SqliteType.Integer, (int) DownloadStatus.Pending);
+			await cmd.ExecuteNonQueryAsync();
+		}
+
+		static async Task InsertDownload(SqliteCommand insertCmd, Data.Download? download) {
+			if (download == null) {
+				return;
+			}
+
+			insertCmd.Set(":normalized_url", download.NormalizedUrl);
+			insertCmd.Set(":download_url", download.DownloadUrl);
+			insertCmd.Set(":status", (int) download.Status);
+			insertCmd.Set(":type", download.Type);
+			insertCmd.Set(":size", download.Size);
+			await insertCmd.ExecuteNonQueryAsync();
+		}
+
+		await conn.BeginTransactionAsync();
+
+		await using var insertCmd = conn.Command("INSERT OR IGNORE INTO download_metadata (normalized_url, download_url, status, type, size) VALUES (:normalized_url, :download_url, :status, :type, :size)");
+		insertCmd.Add(":normalized_url", SqliteType.Text);
+		insertCmd.Add(":download_url", SqliteType.Text);
+		insertCmd.Add(":status", SqliteType.Integer);
+		insertCmd.Add(":type", SqliteType.Text);
+		insertCmd.Add(":size", SqliteType.Integer);
+
+		await reporter.SubWork("Processing embeds...", 1, 4);
+
+		await using (var embedCmd = conn.Command("SELECT json FROM embeds")) {
+			await using var reader = await embedCmd.ExecuteReaderAsync();
+
+			while (await reader.ReadAsync()) {
+				await InsertDownload(insertCmd, await DownloadLinkExtractor.TryFromEmbedJson(reader.GetStream(0)));
+			}
+		}
+
+		await reporter.SubWork("Processing users...", 2, 4);
+
+		await using (var avatarCmd = conn.Command("SELECT id, avatar_url FROM users WHERE avatar_url IS NOT NULL")) {
+			await using var reader = await avatarCmd.ExecuteReaderAsync();
+
+			while (await reader.ReadAsync()) {
+				await InsertDownload(insertCmd, DownloadLinkExtractor.FromUserAvatar(reader.GetUint64(0), reader.GetString(1)));
+			}
+		}
+
+		await reporter.SubWork("Processing reactions...", 3, 4);
+
+		await using (var avatarCmd = conn.Command("SELECT DISTINCT emoji_id, emoji_flags FROM reactions WHERE emoji_id IS NOT NULL")) {
+			await using var reader = await avatarCmd.ExecuteReaderAsync();
+
+			while (await reader.ReadAsync()) {
+				await InsertDownload(insertCmd, DownloadLinkExtractor.FromEmoji(reader.GetUint64(0), (EmojiFlags) reader.GetInt16(1)));
+			}
+		}
+
+		await conn.CommitTransactionAsync();
+	}
+}

app/Server/Database/Sqlite/SqliteDatabaseFile.cs

@@ -2,6 +2,7 @@ using System;
 using System.Threading.Tasks;
 using DHT.Server.Database.Repositories;
 using DHT.Server.Database.Sqlite.Repositories;
+using DHT.Server.Database.Sqlite.Schema;
 using DHT.Server.Database.Sqlite.Utils;
 using Microsoft.Data.Sqlite;
 
@@ -21,7 +22,7 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 
 		try {
 			await using var conn = await pool.Take();
-			wasOpened = await new Schema(conn).Setup(schemaUpgradeCallbacks);
+			wasOpened = await new SqliteSchema(conn).Setup(schemaUpgradeCallbacks);
 		} catch (Exception) {
 			await pool.DisposeAsync();
 			throw;
@@ -42,7 +43,6 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 	public IServerRepository Servers => servers;
 	public IChannelRepository Channels => channels;
 	public IMessageRepository Messages => messages;
-	public IAttachmentRepository Attachments => attachments;
 	public IDownloadRepository Downloads => downloads;
 	
 	private readonly SqliteConnectionPool pool;
@@ -51,18 +51,17 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 	private readonly SqliteServerRepository servers;
 	private readonly SqliteChannelRepository channels;
 	private readonly SqliteMessageRepository messages;
-	private readonly SqliteAttachmentRepository attachments;
 	private readonly SqliteDownloadRepository downloads;
 	
 	private SqliteDatabaseFile(string path, SqliteConnectionPool pool) {
 		this.Path = path;
 		this.pool = pool;
 
-		users = new SqliteUserRepository(pool);
+		downloads = new SqliteDownloadRepository(pool);
+		users = new SqliteUserRepository(pool, downloads);
 		servers = new SqliteServerRepository(pool);
 		channels = new SqliteChannelRepository(pool);
-		messages = new SqliteMessageRepository(pool, attachments = new SqliteAttachmentRepository(pool));
-		downloads = new SqliteDownloadRepository(pool);
+		messages = new SqliteMessageRepository(pool, downloads);
 	}
 
 	public async ValueTask DisposeAsync() {
@@ -70,7 +69,6 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 		servers.Dispose();
 		channels.Dispose();
 		messages.Dispose();
-		attachments.Dispose();
 		downloads.Dispose();
 		await pool.DisposeAsync();
 	}

app/Server/Database/Sqlite/SqliteFilters.cs

@@ -8,77 +8,53 @@ using DHT.Server.Database.Sqlite.Utils;
 namespace DHT.Server.Database.Sqlite;
 
 static class SqliteFilters {
-	private static string WhereAll(bool invert) {
-		return invert ? "WHERE FALSE" : "";
+	public static SqliteConditionBuilder GenerateConditions(this MessageFilter? filter, string? tableAlias = null, bool invert = false) {
+		var builder = new SqliteConditionBuilder(tableAlias, invert);
+
+		if (filter != null) {
+			if (filter.StartDate != null) {
+				builder.AddCondition("timestamp >= " + new DateTimeOffset(filter.StartDate.Value).ToUnixTimeMilliseconds());
+			}
+
+			if (filter.EndDate != null) {
+				builder.AddCondition("timestamp <= " + new DateTimeOffset(filter.EndDate.Value).ToUnixTimeMilliseconds());
+			}
+
+			if (filter.ChannelIds != null) {
+				builder.AddCondition("channel_id IN (" + string.Join(",", filter.ChannelIds) + ")");
+			}
+
+			if (filter.UserIds != null) {
+				builder.AddCondition("sender_id IN (" + string.Join(",", filter.UserIds) + ")");
+			}
+
+			if (filter.MessageIds != null) {
+				builder.AddCondition("message_id IN (" + string.Join(",", filter.MessageIds) + ")");
+			}
+		}
+
+		return builder;
 	}
 
-	public static string GenerateWhereClause(this MessageFilter? filter, string? tableAlias = null, bool invert = false) {
-		if (filter == null || filter.IsEmpty) {
-			return WhereAll(invert);
+	public static SqliteConditionBuilder GenerateConditions(this DownloadItemFilter? filter, string? tableAlias = null, bool invert = false) {
+		var builder = new SqliteConditionBuilder(tableAlias, invert);
+
+		if (filter != null) {
+			if (filter.IncludeStatuses != null) {
+				builder.AddCondition("status IN (" + filter.IncludeStatuses.In() + ")");
+			}
+
+			if (filter.ExcludeStatuses != null) {
+				builder.AddCondition("status NOT IN (" + filter.ExcludeStatuses.In() + ")");
+			}
+
+			if (filter.MaxBytes != null) {
+				builder.AddCondition("size IS NOT NULL");
+				builder.AddCondition("size <= " + filter.MaxBytes);
+			}
 		}
 
-		var where = new SqliteWhereGenerator(tableAlias, invert);
-
-		if (filter.StartDate != null) {
-			where.AddCondition("timestamp >= " + new DateTimeOffset(filter.StartDate.Value).ToUnixTimeMilliseconds());
-		}
-
-		if (filter.EndDate != null) {
-			where.AddCondition("timestamp <= " + new DateTimeOffset(filter.EndDate.Value).ToUnixTimeMilliseconds());
-		}
-
-		if (filter.ChannelIds != null) {
-			where.AddCondition("channel_id IN (" + string.Join(",", filter.ChannelIds) + ")");
-		}
-
-		if (filter.UserIds != null) {
-			where.AddCondition("sender_id IN (" + string.Join(",", filter.UserIds) + ")");
-		}
-
-		if (filter.MessageIds != null) {
-			where.AddCondition("message_id IN (" + string.Join(",", filter.MessageIds) + ")");
-		}
-
-		return where.Generate();
-	}
-
-	public static string GenerateWhereClause(this AttachmentFilter? filter, string? tableAlias = null, bool invert = false) {
-		if (filter == null || filter.IsEmpty) {
-			return WhereAll(invert);
-		}
-
-		var where = new SqliteWhereGenerator(tableAlias, invert);
-
-		if (filter.MaxBytes != null) {
-			where.AddCondition("size <= " + filter.MaxBytes);
-		}
-
-		if (filter.DownloadItemRule == AttachmentFilter.DownloadItemRules.OnlyNotPresent) {
-			where.AddCondition("normalized_url NOT IN (SELECT normalized_url FROM downloads)");
-		}
-		else if (filter.DownloadItemRule == AttachmentFilter.DownloadItemRules.OnlyPresent) {
-			where.AddCondition("normalized_url IN (SELECT normalized_url FROM downloads)");
-		}
-
-		return where.Generate();
-	}
-
-	public static string GenerateWhereClause(this DownloadItemFilter? filter, string? tableAlias = null, bool invert = false) {
-		if (filter == null || filter.IsEmpty) {
-			return WhereAll(invert);
-		}
-
-		var where = new SqliteWhereGenerator(tableAlias, invert);
-
-		if (filter.IncludeStatuses != null) {
-			where.AddCondition("status IN (" + filter.IncludeStatuses.In() + ")");
-		}
-
-		if (filter.ExcludeStatuses != null) {
-			where.AddCondition("status NOT IN (" + filter.ExcludeStatuses.In() + ")");
-		}
-
-		return where.Generate();
+		return builder;
 	}
 
 	private static string In(this ISet<DownloadStatus> statuses) {

app/Server/Database/Sqlite/SqliteSchema.cs

@@ -0,0 +1,193 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using DHT.Server.Database.Exceptions;
+using DHT.Server.Database.Sqlite.Schema;
+using DHT.Server.Database.Sqlite.Utils;
+using DHT.Utils.Logging;
+
+namespace DHT.Server.Database.Sqlite;
+
+sealed class SqliteSchema {
+	internal const int Version = 7;
+
+	private static readonly Log Log = Log.ForType<SqliteSchema>();
+
+	private readonly ISqliteConnection conn;
+
+	public SqliteSchema(ISqliteConnection conn) {
+		this.conn = conn;
+	}
+
+	public async Task<bool> Setup(ISchemaUpgradeCallbacks callbacks) {
+		await conn.ExecuteAsync("CREATE TABLE IF NOT EXISTS metadata (key TEXT PRIMARY KEY, value TEXT)");
+
+		var dbVersionStr = await conn.ExecuteReaderAsync("SELECT value FROM metadata WHERE key = 'version'", static reader => reader?.GetString(0));
+		if (dbVersionStr == null) {
+			await InitializeSchemas();
+		}
+		else if (!int.TryParse(dbVersionStr, out int dbVersion) || dbVersion < 1) {
+			throw new InvalidDatabaseVersionException(dbVersionStr);
+		}
+		else if (dbVersion > Version) {
+			throw new DatabaseTooNewException(dbVersion);
+		}
+		else if (dbVersion < Version) {
+			var proceed = await callbacks.CanUpgrade();
+			if (!proceed) {
+				return false;
+			}
+
+			await callbacks.Start(Version - dbVersion, async reporter => await UpgradeSchemas(dbVersion, reporter));
+		}
+
+		return true;
+	}
+
+	private async Task InitializeSchemas() {
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE users (
+		                        	id            INTEGER PRIMARY KEY NOT NULL,
+		                        	name          TEXT NOT NULL,
+		                        	avatar_url    TEXT,
+		                        	discriminator TEXT
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE servers (
+		                        	id   INTEGER PRIMARY KEY NOT NULL,
+		                        	name TEXT NOT NULL,
+		                        	type TEXT NOT NULL
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE channels (
+		                        	id        INTEGER PRIMARY KEY NOT NULL,
+		                        	server    INTEGER NOT NULL,
+		                        	name      TEXT NOT NULL,
+		                        	parent_id INTEGER,
+		                        	position  INTEGER,
+		                        	topic     TEXT,
+		                        	nsfw      INTEGER
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE messages (
+		                        	message_id INTEGER PRIMARY KEY NOT NULL,
+		                        	sender_id  INTEGER NOT NULL,
+		                        	channel_id INTEGER NOT NULL,
+		                        	text       TEXT NOT NULL,
+		                        	timestamp  INTEGER NOT NULL
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE attachments (
+		                        	message_id     INTEGER NOT NULL,
+		                        	attachment_id  INTEGER NOT NULL PRIMARY KEY NOT NULL,
+		                        	name           TEXT NOT NULL,
+		                        	type           TEXT,
+		                        	normalized_url TEXT NOT NULL,
+		                        	download_url   TEXT,
+		                        	size           INTEGER NOT NULL,
+		                        	width          INTEGER,
+		                        	height         INTEGER
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE embeds (
+		                        	message_id INTEGER NOT NULL,
+		                        	json       TEXT NOT NULL
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE reactions (
+		                        	message_id  INTEGER NOT NULL,
+		                        	emoji_id    INTEGER,
+		                        	emoji_name  TEXT,
+		                        	emoji_flags INTEGER NOT NULL,
+		                        	count       INTEGER NOT NULL
+		                        )
+		                        """);
+
+		await CreateMessageEditTimestampTable(conn);
+		await CreateMessageRepliedToTable(conn);
+		await CreateDownloadTables(conn);
+
+		await conn.ExecuteAsync("CREATE INDEX attachments_message_ix ON attachments(message_id)");
+		await conn.ExecuteAsync("CREATE INDEX embeds_message_ix ON embeds(message_id)");
+		await conn.ExecuteAsync("CREATE INDEX reactions_message_ix ON reactions(message_id)");
+
+		await conn.ExecuteAsync("INSERT INTO metadata (key, value) VALUES ('version', " + Version + ")");
+	}
+
+	internal static async Task CreateMessageEditTimestampTable(ISqliteConnection conn) {
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE edit_timestamps (
+		                        	message_id     INTEGER PRIMARY KEY NOT NULL,
+		                        	edit_timestamp INTEGER NOT NULL
+		                        )
+		                        """);
+	}
+
+	internal static async Task CreateMessageRepliedToTable(ISqliteConnection conn) {
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE replied_to (
+		                        	message_id    INTEGER PRIMARY KEY NOT NULL,
+		                        	replied_to_id INTEGER NOT NULL
+		                        )
+		                        """);
+	}
+
+	internal static async Task CreateDownloadTables(ISqliteConnection conn) {
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE download_metadata (
+		                        	normalized_url TEXT NOT NULL PRIMARY KEY,
+		                        	download_url   TEXT NOT NULL,
+		                        	status         INTEGER NOT NULL,
+		                        	type           TEXT,
+		                        	size           INTEGER
+		                        )
+		                        """);
+
+		await conn.ExecuteAsync("""
+		                        CREATE TABLE download_blobs (
+		                        	normalized_url TEXT NOT NULL PRIMARY KEY,
+		                        	blob           BLOB NOT NULL,
+		                        	FOREIGN KEY (normalized_url) REFERENCES download_metadata (normalized_url) ON UPDATE CASCADE ON DELETE CASCADE
+		                        )
+		                        """);
+	}
+
+	private async Task UpgradeSchemas(int dbVersion, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
+		var upgrades = new Dictionary<int, ISchemaUpgrade> {
+			{ 1, new SqliteSchemaUpgradeTo2() },
+			{ 2, new SqliteSchemaUpgradeTo3() },
+			{ 3, new SqliteSchemaUpgradeTo4() },
+			{ 4, new SqliteSchemaUpgradeTo5() },
+			{ 5, new SqliteSchemaUpgradeTo6() },
+			{ 6, new SqliteSchemaUpgradeTo7() },
+		};
+
+		var perf = Log.Start("from version " + dbVersion);
+
+		for (int fromVersion = dbVersion; fromVersion < Version; fromVersion++) {
+			var toVersion = fromVersion + 1;
+			
+			if (upgrades.TryGetValue(fromVersion, out var upgrade)) {
+				await upgrade.Run(conn, reporter);
+			}
+
+			await conn.ExecuteAsync("UPDATE metadata SET value = " + toVersion + " WHERE key = 'version'");
+
+			perf.Step("Upgrade to version " + toVersion);
+			await reporter.NextVersion();
+		}
+
+		perf.End();
+	}
+}

app/Server/Database/Sqlite/Utils/ISqliteConnection.cs

@@ -1,8 +1,15 @@
 using System;
+using System.Threading.Tasks;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Utils;
 
 interface ISqliteConnection : IAsyncDisposable {
 	SqliteConnection InnerConnection { get; }
+	
+	Task BeginTransactionAsync();
+	Task CommitTransactionAsync();
+	Task RollbackTransactionAsync();
+	
+	void AssignActiveTransaction(SqliteCommand command);
 }

app/Server/Database/Sqlite/Utils/SqliteConditionBuilder.cs

@@ -2,12 +2,12 @@ using System.Collections.Generic;
 
 namespace DHT.Server.Database.Sqlite.Utils;
 
-sealed class SqliteWhereGenerator {
+sealed class SqliteConditionBuilder {
 	private readonly string? tableAlias;
 	private readonly bool invert;
 	private readonly List<string> conditions = [];
 
-	public SqliteWhereGenerator(string? tableAlias, bool invert) {
+	public SqliteConditionBuilder(string? tableAlias, bool invert) {
 		this.tableAlias = tableAlias;
 		this.invert = invert;
 	}
@@ -16,16 +16,20 @@ sealed class SqliteWhereGenerator {
 		conditions.Add(tableAlias == null ? condition : tableAlias + '.' + condition);
 	}
 
-	public string Generate() {
+	public string Build() {
 		if (conditions.Count == 0) {
-			return "";
+			return invert ? "FALSE" : "TRUE";
 		}
 
 		if (invert) {
-			return " WHERE NOT (" + string.Join(" AND ", conditions) + ")";
+			return "NOT (" + string.Join(" AND ", conditions) + ")";
 		}
 		else {
-			return " WHERE " + string.Join(" AND ", conditions);
+			return string.Join(" AND ", conditions);
 		}
 	}
+	
+	public string BuildWhereClause() {
+		return " WHERE " + Build();
+	}
 }

app/Server/Database/Sqlite/Utils/SqliteConnectionPool.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Data.Common;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Utils.Collections;
@@ -42,9 +43,8 @@ sealed class SqliteConnectionPool : IAsyncDisposable {
 
 			var pooledConnection = new PooledConnection(this, conn);
 
-			await using (var cmd = pooledConnection.Command("PRAGMA journal_mode=WAL")) {
-				await cmd.ExecuteNonQueryAsync(disposalToken);
-			}
+			await pooledConnection.ExecuteAsync("PRAGMA journal_mode=WAL", disposalToken);
+			await pooledConnection.ExecuteAsync("PRAGMA foreign_keys=ON", disposalToken);
 
 			all.Add(pooledConnection);
 			await free.Push(pooledConnection, disposalToken);
@@ -74,17 +74,48 @@ sealed class SqliteConnectionPool : IAsyncDisposable {
 		disposalTokenSource.Dispose();
 	}
 
-	private sealed class PooledConnection : ISqliteConnection {
-		public SqliteConnection InnerConnection { get; }
+	private sealed class PooledConnection(SqliteConnectionPool pool, SqliteConnection conn) : ISqliteConnection {
+		public SqliteConnection InnerConnection { get; } = conn;
 
-		private readonly SqliteConnectionPool pool;
+		private DbTransaction? activeTransaction;
 
-		public PooledConnection(SqliteConnectionPool pool, SqliteConnection conn) {
-			this.pool = pool;
-			this.InnerConnection = conn;
+		public async Task BeginTransactionAsync() {
+			if (activeTransaction != null) {
+				throw new InvalidOperationException("A transaction is already active.");
+			}
+			
+			activeTransaction = await InnerConnection.BeginTransactionAsync();
+		}
+
+		public async Task CommitTransactionAsync() {
+			if (activeTransaction == null) {
+				throw new InvalidOperationException("No active transaction to commit.");
+			}
+
+			await activeTransaction.CommitAsync();
+			await activeTransaction.DisposeAsync();
+			activeTransaction = null;
+		}
+
+		public async Task RollbackTransactionAsync() {
+			if (activeTransaction == null) {
+				throw new InvalidOperationException("No active transaction to rollback.");
+			}
+			
+			await activeTransaction.RollbackAsync();
+			await activeTransaction.DisposeAsync();
+			activeTransaction = null;
+		}
+
+		public void AssignActiveTransaction(SqliteCommand command) {
+			command.Transaction = (SqliteTransaction?) activeTransaction;
 		}
 
 		public async ValueTask DisposeAsync() {
+			if (activeTransaction != null) {
+				await RollbackTransactionAsync();
+			}
+			
 			await pool.Return(this);
 		}
 	}

app/Server/Database/Sqlite/Utils/SqliteExtensions.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Data.Common;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -9,11 +8,7 @@ using Microsoft.Data.Sqlite;
 namespace DHT.Server.Database.Sqlite.Utils;
 
 static class SqliteExtensions {
-	public static ValueTask<DbTransaction> BeginTransactionAsync(this ISqliteConnection conn) {
-		return conn.InnerConnection.BeginTransactionAsync();
-	}
-
-	public static SqliteCommand Command(this ISqliteConnection conn, string sql) {
+	public static SqliteCommand Command(this ISqliteConnection conn, [LanguageInjection("sql")] string sql) {
 		var cmd = conn.InnerConnection.CreateCommand();
 		cmd.CommandText = sql;
 		return cmd;
@@ -28,7 +23,11 @@ static class SqliteExtensions {
 		await using var cmd = conn.Command(sql);
 		await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
 
-		return reader.Read() ? readFunction(reader) : readFunction(null);
+		return await reader.ReadAsync(cancellationToken) ? readFunction(reader) : readFunction(null);
+	}
+	
+	public static async Task<long> ExecuteLongScalarAsync(this SqliteCommand command) {
+		return (long) (await command.ExecuteScalarAsync())!;
 	}
 
 	public static SqliteCommand Insert(this ISqliteConnection conn, string tableName, (string Name, SqliteType Type)[] columns) {

app/Server/Download/DiscordCdn.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Frozen;
+using System.Diagnostics.CodeAnalysis;
+using System.Web;
 
 namespace DHT.Server.Download;
 
@@ -7,9 +9,35 @@ static class DiscordCdn {
 	private static FrozenSet<string> CdnHosts { get; } = new[] {
 		"cdn.discordapp.com",
 		"cdn.discord.com",
+		"media.discordapp.net"
 	}.ToFrozenSet();
 
+	private static bool IsCdnUrl(string originalUrl, [NotNullWhen(true)] out Uri? uri) {
+		return Uri.TryCreate(originalUrl, UriKind.Absolute, out uri) && CdnHosts.Contains(uri.Host);
+	}
+
 	public static string NormalizeUrl(string originalUrl) {
-		return Uri.TryCreate(originalUrl, UriKind.Absolute, out var uri) && CdnHosts.Contains(uri.Host) ? uri.GetLeftPart(UriPartial.Path) : originalUrl;
+		return IsCdnUrl(originalUrl, out var uri) ? DoNormalize(uri) : originalUrl;
+	}
+
+	public static bool NormalizeUrlAndReturnIfCdn(string originalUrl, out string normalizedUrl) {
+		if (IsCdnUrl(originalUrl, out var uri)) {
+			normalizedUrl = DoNormalize(uri);
+			return true;
+		}
+		else {
+			normalizedUrl = originalUrl;
+			return false;
+		}
+	}
+
+	private static string DoNormalize(Uri uri) {
+		var query = HttpUtility.ParseQueryString(uri.Query);
+		
+		query.Remove("ex");
+		query.Remove("is");
+		query.Remove("hm");
+
+		return new UriBuilder(uri) { Query = query.ToString() }.Uri.ToString();
 	}
 }

app/Server/Download/DownloadItem.cs

@@ -1,7 +1,21 @@
+using System;
+using System.Net;
+using DHT.Server.Data;
+
 namespace DHT.Server.Download;
 
 public readonly struct DownloadItem {
 	public string NormalizedUrl { get; init; }
 	public string DownloadUrl { get; init; }
-	public ulong Size { get; init; }
+	public string? Type { get; init; }
+	public ulong? Size { get; init; }
+	
+	internal Data.Download ToSuccess(long size) {
+		return new Data.Download(NormalizedUrl, DownloadUrl, DownloadStatus.Success, Type, (ulong) Math.Max(size, 0));
+	}
+	
+	internal Data.Download ToFailure(HttpStatusCode? statusCode = null) {
+		var status = statusCode.HasValue ? (DownloadStatus) (int) statusCode : DownloadStatus.GenericError;
+		return new Data.Download(NormalizedUrl, DownloadUrl, status, Type, Size);
+	}
 }

app/Server/Download/DownloadLinkExtractor.cs

@@ -0,0 +1,122 @@
+using System;
+using System.IO;
+using System.Net.Mime;
+using System.Text.Json;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Data.Embeds;
+using DHT.Utils.Logging;
+
+namespace DHT.Server.Download;
+
+static class DownloadLinkExtractor {
+	private static readonly Log Log = Log.ForType(typeof(DownloadLinkExtractor));
+
+	public static Data.Download FromUserAvatar(ulong userId, string avatarPath) {
+		string url = $"https://cdn.discordapp.com/avatars/{userId}/{avatarPath}.webp";
+		return new Data.Download(url, url, DownloadStatus.Pending, MediaTypeNames.Image.Webp, size: null);
+	}
+
+	public static Data.Download FromEmoji(ulong emojiId, EmojiFlags flags) {
+		var isAnimated = flags.HasFlag(EmojiFlags.Animated);
+		
+		string ext = isAnimated ? "gif" : "webp";
+		string type = isAnimated ? MediaTypeNames.Image.Gif : MediaTypeNames.Image.Webp;
+		
+		string url = $"https://cdn.discordapp.com/emojis/{emojiId}.{ext}";
+		return new Data.Download(url, url, DownloadStatus.Pending, type, size: null);
+	}
+
+	public static Data.Download FromAttachment(Attachment attachment) {
+		return new Data.Download(attachment.NormalizedUrl, attachment.DownloadUrl, DownloadStatus.Pending, attachment.Type, attachment.Size);
+	}
+
+	public static async Task<Data.Download?> TryFromEmbedJson(Stream jsonStream) {
+		try {
+			return FromEmbed(await JsonSerializer.DeserializeAsync(jsonStream, DiscordEmbedJsonContext.Default.DiscordEmbedJson));
+		} catch (Exception e) {
+			Log.Error("Could not parse embed json: " + e);
+			return null;
+		}
+	}
+
+	public static Data.Download? TryFromEmbedJson(string json) {
+		try {
+			return FromEmbed(JsonSerializer.Deserialize(json, DiscordEmbedJsonContext.Default.DiscordEmbedJson));
+		} catch (Exception e) {
+			Log.Error("Could not parse embed json: " + e);
+			return null;
+		}
+	}
+	
+	private static Data.Download? FromEmbed(DiscordEmbedJson? embed) {
+		if (embed is { Type: "image", Image.Url: {} imageUrl }) {
+			return FromEmbedImage(imageUrl);
+		}
+		else if (embed is { Type: "video", Video.Url: {} videoUrl }) {
+			return FromEmbedVideo(videoUrl);
+		}
+		else {
+			return null;
+		}
+	}
+
+	private static Data.Download? FromEmbedImage(string url) {
+		if (DiscordCdn.NormalizeUrlAndReturnIfCdn(url, out var normalizedUrl)) {
+			return new Data.Download(normalizedUrl, url, DownloadStatus.Pending, GuessImageType(normalizedUrl), size: null);
+		}
+		else {
+			Log.Debug("Skipping non-CDN image url: " + url);
+			return null;
+		}
+	}
+
+	private static Data.Download? FromEmbedVideo(string url) {
+		if (DiscordCdn.NormalizeUrlAndReturnIfCdn(url, out var normalizedUrl)) {
+			return new Data.Download(normalizedUrl, url, DownloadStatus.Pending, GuessVideoType(normalizedUrl), size: null);
+		}
+		else {
+			Log.Debug("Skipping non-CDN video url: " + url);
+			return null;
+		}
+	}
+
+	private static string? GuessImageType(string url) {
+		if (!Uri.TryCreate(url, UriKind.Absolute, out var uri)) {
+			return null;
+		}
+
+		ReadOnlySpan<char> extension = Path.GetExtension(uri.AbsolutePath).ToLowerInvariant();
+		
+		// Remove Twitter quality suffix.
+		int colonIndex = extension.IndexOf(':');
+		if (colonIndex != -1) {
+			extension = extension[..colonIndex];
+		}
+
+		return extension switch {
+			".jpg"  => MediaTypeNames.Image.Jpeg,
+			".jpeg" => MediaTypeNames.Image.Jpeg,
+			".png"  => MediaTypeNames.Image.Png,
+			".gif"  => MediaTypeNames.Image.Gif,
+			".webp" => MediaTypeNames.Image.Webp,
+			".bmp"  => MediaTypeNames.Image.Bmp,
+			_       => null
+		};
+	}
+
+	private static string? GuessVideoType(string url) {
+		if (!Uri.TryCreate(url, UriKind.Absolute, out var uri)) {
+			return null;
+		}
+
+		string extension = Path.GetExtension(uri.AbsolutePath).ToLowerInvariant();
+		return extension switch {
+			".mp4"  => "video/mp4",
+			".mpeg" => "video/mpeg",
+			".webm" => "video/webm",
+			".mov"  => "video/quicktime",
+			_       => null
+		};
+	}
+}

app/Server/Download/Downloader.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Threading;
 using System.Threading.Tasks;
+using DHT.Server.Data.Filters;
 using DHT.Server.Database;
 
 namespace DHT.Server.Download;
@@ -10,16 +11,18 @@ public sealed class Downloader {
 	public bool IsDownloading => current != null;
 	
 	private readonly IDatabaseFile db;
+	private readonly int? concurrentDownloads;
 	private readonly SemaphoreSlim semaphore = new (1, 1);
 	
-	internal Downloader(IDatabaseFile db) {
+	internal Downloader(IDatabaseFile db, int? concurrentDownloads) {
 		this.db = db;
+		this.concurrentDownloads = concurrentDownloads;
 	}
 
-	public async Task<IObservable<DownloadItem>> Start() {
+	public async Task<IObservable<DownloadItem>> Start(DownloadItemFilter filter) {
 		await semaphore.WaitAsync();
 		try {
-			current ??= new DownloaderTask(db);
+			current ??= new DownloaderTask(db, filter, concurrentDownloads);
 			return current.FinishedItems;
 		} finally {
 			semaphore.Release();

app/Server/Download/DownloaderTask.cs

@@ -5,6 +5,7 @@ using System.Reactive.Subjects;
 using System.Threading;
 using System.Threading.Channels;
 using System.Threading.Tasks;
+using DHT.Server.Data.Filters;
 using DHT.Server.Database;
 using DHT.Utils.Logging;
 using DHT.Utils.Tasks;
@@ -14,10 +15,14 @@ namespace DHT.Server.Download;
 sealed class DownloaderTask : IAsyncDisposable {
 	private static readonly Log Log = Log.ForType<DownloaderTask>();
 
-	private const int DownloadTasks = 4;
+	private const int DefaultConcurrentDownloads = 4;
 	private const int QueueSize = 25;
 	private const string UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36";
 
+	private static int GetDownloadTaskCount(int? concurrentDownloads) {
+		return Math.Max(1, concurrentDownloads ?? DefaultConcurrentDownloads);
+	}
+
 	private readonly Channel<DownloadItem> downloadQueue = Channel.CreateBounded<DownloadItem>(new BoundedChannelOptions(QueueSize) {
 		SingleReader = false,
 		SingleWriter = true,
@@ -29,6 +34,7 @@ sealed class DownloaderTask : IAsyncDisposable {
 	private readonly CancellationToken cancellationToken;
 
 	private readonly IDatabaseFile db;
+	private readonly DownloadItemFilter filter;
 	private readonly ISubject<DownloadItem> finishedItemPublisher = Subject.Synchronize(new Subject<DownloadItem>());
 
 	private readonly Task queueWriterTask;
@@ -36,16 +42,17 @@ sealed class DownloaderTask : IAsyncDisposable {
 
 	public IObservable<DownloadItem> FinishedItems => finishedItemPublisher;
 
-	internal DownloaderTask(IDatabaseFile db) {
+	internal DownloaderTask(IDatabaseFile db, DownloadItemFilter filter, int? concurrentDownloads) {
 		this.db = db;
+		this.filter = filter;
 		this.cancellationToken = cancellationTokenSource.Token;
 		this.queueWriterTask = Task.Run(RunQueueWriterTask);
-		this.downloadTasks = Enumerable.Range(1, DownloadTasks).Select(taskIndex => Task.Run(() => RunDownloadTask(taskIndex))).ToArray();
+		this.downloadTasks = Enumerable.Range(1, GetDownloadTaskCount(concurrentDownloads)).Select(taskIndex => Task.Run(() => RunDownloadTask(taskIndex))).ToArray();
 	}
 
 	private async Task RunQueueWriterTask() {
 		while (await downloadQueue.Writer.WaitToWriteAsync(cancellationToken)) {
-			var newItems = await db.Downloads.PullEnqueuedDownloadItems(QueueSize, cancellationToken).ToListAsync(cancellationToken);
+			var newItems = await db.Downloads.PullPendingDownloadItems(QueueSize, filter, cancellationToken).ToListAsync(cancellationToken);
 			if (newItems.Count == 0) {
 				await Task.Delay(TimeSpan.FromMilliseconds(50), cancellationToken);
 				continue;
@@ -60,24 +67,39 @@ sealed class DownloaderTask : IAsyncDisposable {
 	private async Task RunDownloadTask(int taskIndex) {
 		var log = Log.ForType<DownloaderTask>("Task " + taskIndex);
 
-		var client = new HttpClient();
+		var client = new HttpClient(new SocketsHttpHandler {
+			ConnectTimeout = TimeSpan.FromSeconds(30)
+		});
+		
+		client.Timeout = Timeout.InfiniteTimeSpan;
 		client.DefaultRequestHeaders.UserAgent.ParseAdd(UserAgent);
-		client.Timeout = TimeSpan.FromSeconds(30);
 
 		while (!cancellationToken.IsCancellationRequested) {
 			var item = await downloadQueue.Reader.ReadAsync(cancellationToken);
 			log.Debug("Downloading " + item.DownloadUrl + "...");
 
 			try {
-				var downloadedBytes = await client.GetByteArrayAsync(item.DownloadUrl, cancellationToken);
-				await db.Downloads.AddDownload(Data.Download.NewSuccess(item, downloadedBytes));
-			} catch (OperationCanceledException) {
+				var response = await client.SendAsync(new HttpRequestMessage(HttpMethod.Get, item.DownloadUrl), HttpCompletionOption.ResponseHeadersRead, cancellationToken);
+				response.EnsureSuccessStatusCode();
+
+				if (response.Content.Headers.ContentLength is {} contentLength) {
+					await using var stream = await response.Content.ReadAsStreamAsync(cancellationToken);
+					await db.Downloads.AddDownload(item.ToSuccess(contentLength), stream);
+				}
+				else {
+					await db.Downloads.AddDownload(item.ToFailure(), stream: null);
+					log.Error("Download response has no content length: " + item.DownloadUrl);
+				}
+			} catch (OperationCanceledException e) when (e.CancellationToken == cancellationToken) {
 				// Ignore.
+			} catch (TaskCanceledException e) when (e.InnerException is TimeoutException) {
+				await db.Downloads.AddDownload(item.ToFailure(), stream: null);
+				log.Error("Download timed out: " + item.DownloadUrl);
 			} catch (HttpRequestException e) {
-				await db.Downloads.AddDownload(Data.Download.NewFailure(item, e.StatusCode, item.Size));
+				await db.Downloads.AddDownload(item.ToFailure(e.StatusCode), stream: null);
 				log.Error(e);
 			} catch (Exception e) {
-				await db.Downloads.AddDownload(Data.Download.NewFailure(item, null, item.Size));
+				await db.Downloads.AddDownload(item.ToFailure(), stream: null);
 				log.Error(e);
 			} finally {
 				try {

app/Server/Endpoints/BaseEndpoint.cs

@@ -9,37 +9,37 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-abstract class BaseEndpoint {
+abstract class BaseEndpoint(IDatabaseFile db) {
 	private static readonly Log Log = Log.ForType<BaseEndpoint>();
 
-	protected IDatabaseFile Db { get; }
-
-	protected BaseEndpoint(IDatabaseFile db) {
-		this.Db = db;
-	}
+	protected IDatabaseFile Db { get; } = db;
 
 	public async Task Handle(HttpContext ctx) {
 		var response = ctx.Response;
 
 		try {
 			response.StatusCode = (int) HttpStatusCode.OK;
-			var output = await Respond(ctx);
-			await output.WriteTo(response);
+			await Respond(ctx.Request, response);
 		} catch (HttpException e) {
 			Log.Error(e);
 			response.StatusCode = (int) e.StatusCode;
-			await response.WriteAsync(e.Message);
+			if (response.HasStarted) {
+				Log.Warn("Response has already started, cannot write status message: " + e.Message);
+			}
+			else {
+				await response.WriteAsync(e.Message);
+			}
 		} catch (Exception e) {
 			Log.Error(e);
 			response.StatusCode = (int) HttpStatusCode.InternalServerError;
 		}
 	}
 
-	protected abstract Task<IHttpOutput> Respond(HttpContext ctx);
+	protected abstract Task Respond(HttpRequest request, HttpResponse response);
 
-	protected static async Task<JsonElement> ReadJson(HttpContext ctx) {
+	protected static async Task<JsonElement> ReadJson(HttpRequest request) {
 		try {
-			return await ctx.Request.ReadFromJsonAsync(JsonElementContext.Default.JsonElement);
+			return await request.ReadFromJsonAsync(JsonElementContext.Default.JsonElement);
 		} catch (JsonException) {
 			throw new HttpException(HttpStatusCode.UnsupportedMediaType, "This endpoint only accepts JSON.");
 		}

app/Server/Endpoints/GetAttachmentEndpoint.cs

@@ -1,24 +0,0 @@
-using System.Net;
-using System.Threading.Tasks;
-using DHT.Server.Data;
-using DHT.Server.Database;
-using DHT.Utils.Http;
-using Microsoft.AspNetCore.Http;
-
-namespace DHT.Server.Endpoints;
-
-sealed class GetAttachmentEndpoint : BaseEndpoint {
-	public GetAttachmentEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		string attachmentUrl = WebUtility.UrlDecode((string) ctx.Request.RouteValues["url"]!);
-		DownloadedAttachment? maybeDownloadedAttachment = await Db.Downloads.GetDownloadedAttachment(attachmentUrl);
-
-		if (maybeDownloadedAttachment is {} downloadedAttachment) {
-			return new HttpOutput.File(downloadedAttachment.Type, downloadedAttachment.Data);
-		}
-		else {
-			return new HttpOutput.Redirect(attachmentUrl, permanent: false);
-		}
-	}
-}

app/Server/Endpoints/GetDownloadedFileEndpoint.cs

@@ -0,0 +1,19 @@
+using System.Net;
+using System.Threading.Tasks;
+using DHT.Server.Database;
+using DHT.Server.Download;
+using DHT.Utils.Http;
+using Microsoft.AspNetCore.Http;
+
+namespace DHT.Server.Endpoints;
+
+sealed class GetDownloadedFileEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		string url = WebUtility.UrlDecode((string) request.RouteValues["url"]!);
+		string normalizedUrl = DiscordCdn.NormalizeUrl(url);
+		
+		if (!await Db.Downloads.GetSuccessfulDownloadWithData(normalizedUrl, (download, stream) => response.WriteStreamAsync(download.Type, download.Size, stream))) {
+			response.Redirect(url, permanent: false);
+		}
+	}
+}

app/Server/Endpoints/GetTrackingScriptEndpoint.cs

@@ -1,5 +1,5 @@
+using System.Net.Mime;
 using System.Reflection;
-using System.Text;
 using System.Threading.Tasks;
 using System.Web;
 using DHT.Server.Database;
@@ -10,25 +10,19 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class GetTrackingScriptEndpoint : BaseEndpoint {
+sealed class GetTrackingScriptEndpoint(IDatabaseFile db, ServerParameters parameters) : BaseEndpoint(db) {
 	private static ResourceLoader Resources { get; } = new (Assembly.GetExecutingAssembly());
-	
-	private readonly ServerParameters serverParameters;
-	
-	public GetTrackingScriptEndpoint(IDatabaseFile db, ServerParameters parameters) : base(db) {
-		serverParameters = parameters;
-	}
 
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
 		string bootstrap = await Resources.ReadTextAsync("Tracker/bootstrap.js");
-		string script = bootstrap.Replace("= 0; /*[PORT]*/", "= " + serverParameters.Port + ";")
-		                         .Replace("/*[TOKEN]*/", HttpUtility.JavaScriptStringEncode(serverParameters.Token))
+		string script = bootstrap.Replace("= 0; /*[PORT]*/", "= " + parameters.Port + ";")
+		                         .Replace("/*[TOKEN]*/", HttpUtility.JavaScriptStringEncode(parameters.Token))
 		                         .Replace("/*[IMPORTS]*/", await Resources.ReadJoinedAsync("Tracker/scripts/", '\n'))
 		                         .Replace("/*[CSS-CONTROLLER]*/", await Resources.ReadTextAsync("Tracker/styles/controller.css"))
 		                         .Replace("/*[CSS-SETTINGS]*/", await Resources.ReadTextAsync("Tracker/styles/settings.css"))
-		                         .Replace("/*[DEBUGGER]*/", ctx.Request.Query.ContainsKey("debug") ? "debugger;" : "");
+		                         .Replace("/*[DEBUGGER]*/", request.Query.ContainsKey("debug") ? "debugger;" : "");
 		
-		ctx.Response.Headers.Append("X-DHT", "1");
-		return new HttpOutput.File("text/javascript", Encoding.UTF8.GetBytes(script));
+		response.Headers.Append("X-DHT", "1");
+		await response.WriteTextAsync(MediaTypeNames.Text.JavaScript, script);
 	}
 }

app/Server/Endpoints/TrackChannelEndpoint.cs

@@ -8,18 +8,14 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class TrackChannelEndpoint : BaseEndpoint {
-	public TrackChannelEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		var root = await ReadJson(ctx);
+sealed class TrackChannelEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		var root = await ReadJson(request);
 		var server = ReadServer(root.RequireObject("server"), "server");
 		var channel = ReadChannel(root.RequireObject("channel"), "channel", server.Id);
 
 		await Db.Servers.Add([server]);
 		await Db.Channels.Add([channel]);
-
-		return HttpOutput.None;
 	}
 
 	private static Data.Server ReadServer(JsonElement json, string path) => new () {

app/Server/Endpoints/TrackMessagesEndpoint.cs

@@ -15,14 +15,12 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class TrackMessagesEndpoint : BaseEndpoint {
+sealed class TrackMessagesEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
 	private const string HasNewMessages = "1";
 	private const string NoNewMessages = "0";
 
-	public TrackMessagesEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		var root = await ReadJson(ctx);
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		var root = await ReadJson(request);
 
 		if (root.ValueKind != JsonValueKind.Array) {
 			throw new HttpException(HttpStatusCode.BadRequest, "Expected root element to be an array.");
@@ -43,7 +41,7 @@ sealed class TrackMessagesEndpoint : BaseEndpoint {
 
 		await Db.Messages.Add(messages);
 
-		return new HttpOutput.Text(anyNewMessages ? HasNewMessages : NoNewMessages);
+		await response.WriteTextAsync(anyNewMessages ? HasNewMessages : NoNewMessages);
 	}
 
 	private static Message ReadMessage(JsonElement json, string path) => new () {

app/Server/Endpoints/TrackUsersEndpoint.cs

@@ -8,11 +8,9 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class TrackUsersEndpoint : BaseEndpoint {
-	public TrackUsersEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		var root = await ReadJson(ctx);
+sealed class TrackUsersEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		var root = await ReadJson(request);
 
 		if (root.ValueKind != JsonValueKind.Array) {
 			throw new HttpException(HttpStatusCode.BadRequest, "Expected root element to be an array.");
@@ -26,8 +24,6 @@ sealed class TrackUsersEndpoint : BaseEndpoint {
 		}
 
 		await Db.Users.Add(users);
-
-		return HttpOutput.None;
 	}
 
 	private static User ReadUser(JsonElement json, string path) => new () {

app/Server/Service/ServerStartup.cs

@@ -41,7 +41,7 @@ sealed class Startup {
 		
 		app.UseEndpoints(endpoints => {
 			endpoints.MapGet("/get-tracking-script", new GetTrackingScriptEndpoint(db, parameters).Handle);
-			endpoints.MapGet("/get-attachment/{url}", new GetAttachmentEndpoint(db).Handle);
+			endpoints.MapGet("/get-downloaded-file/{url}", new GetDownloadedFileEndpoint(db).Handle);
 			endpoints.MapPost("/track-channel", new TrackChannelEndpoint(db).Handle);
 			endpoints.MapPost("/track-users", new TrackUsersEndpoint(db).Handle);
 			endpoints.MapPost("/track-messages", new TrackMessagesEndpoint(db).Handle);

app/Server/State.cs

@@ -6,18 +6,12 @@ using DHT.Server.Service;
 
 namespace DHT.Server;
 
-public sealed class State : IAsyncDisposable {
-	public static State Dummy { get; } = new (DummyDatabaseFile.Instance);
+public sealed class State(IDatabaseFile db, int? concurrentDownloads) : IAsyncDisposable {
+	public static State Dummy { get; } = new (DummyDatabaseFile.Instance, null);
 	
-	public IDatabaseFile Db { get; }
-	public Downloader Downloader { get; }
-	public ServerManager Server { get; }
-
-	public State(IDatabaseFile db) {
-		Db = db;
-		Downloader = new Downloader(db);
-		Server = new ServerManager(db);
-	}
+	public IDatabaseFile Db { get; } = db;
+	public Downloader Downloader { get; } = new (db, concurrentDownloads);
+	public ServerManager Server { get; } = new (db);
 
 	public async ValueTask DisposeAsync() {
 		await Downloader.Stop();

app/Utils/Collections/LinqExtensions.cs

@@ -8,7 +8,7 @@ public static class LinqExtensions {
 		HashSet<TKey>? seenKeys = null;
 
 		foreach (var item in collection) {
-			seenKeys ??= new HashSet<TKey>();
+			seenKeys ??= [];
 
 			if (seenKeys.Add(getKeyFromItem(item))) {
 				yield return item;

app/Utils/Http/HttpExtensions.cs

@@ -0,0 +1,33 @@
+using System.IO;
+using System.Net.Mime;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+
+namespace DHT.Utils.Http; 
+
+public static class HttpExtensions {
+	public static Task WriteTextAsync(this HttpResponse response, string text) {
+		return WriteTextAsync(response, MediaTypeNames.Text.Plain, text);
+	}
+	
+	public static async Task WriteTextAsync(this HttpResponse response, string contentType, string text) {
+		response.ContentType = contentType;
+		await response.StartAsync();
+		await response.WriteAsync(text, Encoding.UTF8);
+	}
+	
+	public static async Task WriteFileAsync(this HttpResponse response, string? contentType, byte[] bytes) {
+		response.ContentType = contentType ?? string.Empty;
+		response.ContentLength = bytes.Length;
+		await response.StartAsync();
+		await response.Body.WriteAsync(bytes);
+	}
+	
+	public static async Task WriteStreamAsync(this HttpResponse response, string? contentType, ulong? contentLength, Stream source) {
+		response.ContentType = contentType ?? string.Empty;
+		response.ContentLength = (long?) contentLength;
+		await response.StartAsync();
+		await source.CopyToAsync(response.Body);
+	}
+}

app/Utils/Http/HttpOutput.cs

@@ -1,35 +0,0 @@
-using System.Text;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Http;
-
-namespace DHT.Utils.Http;
-
-public static class HttpOutput {
-	public static IHttpOutput None { get; } = new NoneImpl();
-
-	private sealed class NoneImpl : IHttpOutput {
-		public Task WriteTo(HttpResponse response) {
-			return Task.CompletedTask;
-		}
-	}
-
-	public sealed class Text(string text) : IHttpOutput {
-		public Task WriteTo(HttpResponse response) {
-			return response.WriteAsync(text, Encoding.UTF8);
-		}
-	}
-
-	public sealed class File(string? contentType, byte[] bytes) : IHttpOutput {
-		public async Task WriteTo(HttpResponse response) {
-			response.ContentType = contentType ?? string.Empty;
-			await response.Body.WriteAsync(bytes);
-		}
-	}
-
-	public sealed class Redirect(string url, bool permanent) : IHttpOutput {
-		public Task WriteTo(HttpResponse response) {
-			response.Redirect(url, permanent);
-			return Task.CompletedTask;
-		}
-	}
-}

app/Utils/Http/IHttpOutput.cs

@@ -1,8 +0,0 @@
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Http;
-
-namespace DHT.Utils.Http;
-
-public interface IHttpOutput {
-	Task WriteTo(HttpResponse response);
-}

app/Utils/Tasks/ObservableThrottledTask.cs

@@ -2,6 +2,7 @@ using System;
 using System.Reactive.Subjects;
 using System.Threading;
 using System.Threading.Tasks;
+using DHT.Utils.Logging;
 
 namespace DHT.Utils.Tasks;
 
@@ -9,9 +10,9 @@ public sealed class ObservableThrottledTask<T> : IObservable<T>, IDisposable {
 	private readonly ReplaySubject<T> subject;
 	private readonly ThrottledTask<T> task;
 
-	public ObservableThrottledTask(TaskScheduler resultScheduler) {
+	public ObservableThrottledTask(Log log, TaskScheduler resultScheduler) {
 		this.subject = new ReplaySubject<T>(bufferSize: 1);
-		this.task = new ThrottledTask<T>(subject.OnNext, resultScheduler);
+		this.task = new ThrottledTask<T>(log, subject.OnNext, resultScheduler);
 	}
 
 	public void Post(Func<CancellationToken, Task<T>> resultComputer) {

app/Utils/Tasks/ThrottledTask.cs

@@ -2,6 +2,7 @@ using System;
 using System.Threading;
 using System.Threading.Channels;
 using System.Threading.Tasks;
+using DHT.Utils.Logging;
 
 namespace DHT.Utils.Tasks;
 
@@ -14,8 +15,11 @@ public abstract class ThrottledTaskBase<T> : IDisposable {
 	});
 	
 	private readonly CancellationTokenSource cancellationTokenSource = new ();
+	private readonly Log log;
 	
-	internal ThrottledTaskBase() {}
+	internal ThrottledTaskBase(Log log) {
+		this.log = log;
+	}
 
 	protected async Task ReaderTask() {
 		var cancellationToken = cancellationTokenSource.Token;
@@ -26,8 +30,8 @@ public abstract class ThrottledTaskBase<T> : IDisposable {
 					await Run(item, cancellationToken);
 				} catch (OperationCanceledException) {
 					throw;
-				} catch (Exception) {
-					// Ignore.
+				} catch (Exception e) {
+					log.Error("Caught exception in task: " + e);
 				}
 			}
 		} catch (OperationCanceledException) {
@@ -53,7 +57,7 @@ public sealed class ThrottledTask : ThrottledTaskBase<Task> {
 	private readonly Action resultProcessor;
 	private readonly TaskScheduler resultScheduler;
 
-	public ThrottledTask(Action resultProcessor, TaskScheduler resultScheduler) {
+	public ThrottledTask(Log log, Action resultProcessor, TaskScheduler resultScheduler) : base(log) {
 		this.resultProcessor = resultProcessor;
 		this.resultScheduler = resultScheduler;
 
@@ -70,7 +74,7 @@ public sealed class ThrottledTask<T> : ThrottledTaskBase<Task<T>> {
 	private readonly Action<T> resultProcessor;
 	private readonly TaskScheduler resultScheduler;
 
-	public ThrottledTask(Action<T> resultProcessor, TaskScheduler resultScheduler) {
+	public ThrottledTask(Log log, Action<T> resultProcessor, TaskScheduler resultScheduler) : base(log) {
 		this.resultProcessor = resultProcessor;
 		this.resultScheduler = resultScheduler;
 

app/Version.cs

@@ -8,5 +8,5 @@ using DHT.Utils;
 namespace DHT.Utils;
 
 static class Version {
-	public const string Tag = "40.0.0.0";
+	public const string Tag = "41.2.0.0";
 }