Fix wrong attachment download progress information after re-enqueueing items

app/Desktop/Common/DatabaseGui.cs

@@ -11,6 +11,7 @@ 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.Utils.Logging;
 
 namespace DHT.Desktop.Common;
@@ -20,9 +21,9 @@ static class DatabaseGui {
 
 	private const string DatabaseFileInitialName = "archive.dht";
 
-	private static readonly IReadOnlyList<FilePickerFileType> DatabaseFileDialogFilter = new List<FilePickerFileType> {
+	private static readonly IReadOnlyList<FilePickerFileType> DatabaseFileDialogFilter = [
-		FileDialogs.CreateFilter("Discord History Tracker Database", new [] { "dht" })
+		FileDialogs.CreateFilter("Discord History Tracker Database", ["dht"])
-	};
+	];
 
 	public static async Task<string[]> NewOpenDatabaseFilesDialog(Window window, string? suggestedDirectory) {
 		return await window.StorageProvider.OpenFiles(new FilePickerOpenOptions {

app/Desktop/Dialogs/Progress/IProgressCallback.cs

@@ -4,5 +4,6 @@ namespace DHT.Desktop.Dialogs.Progress;
 
 interface IProgressCallback {
 	Task Update(string message, int finishedItems, int totalItems);
+	Task UpdateIndeterminate(string message);
 	Task Hide();
 }

app/Desktop/Dialogs/Progress/ProgressDialog.axaml

@@ -40,7 +40,7 @@
                         <TextBlock DockPanel.Dock="Right" Text="{Binding Items}" Classes="items" />
                         <TextBlock DockPanel.Dock="Left" Text="{Binding Message}" />
                     </DockPanel>
-                    <ProgressBar Value="{Binding Progress}" />
+                    <ProgressBar IsIndeterminate="{Binding IsIndeterminate}" Value="{Binding Progress}" />
                 </StackPanel>
             </DataTemplate>
         </ItemsRepeater.ItemTemplate>

app/Desktop/Dialogs/Progress/ProgressDialog.axaml.cs

@@ -7,6 +7,58 @@ namespace DHT.Desktop.Dialogs.Progress;
 
 [SuppressMessage("ReSharper", "MemberCanBeInternal")]
 public sealed partial class ProgressDialog : Window {
+	internal static async Task Show(Window owner, string title, Func<ProgressDialog, IProgressCallback, Task> action) {
+		var taskCompletionSource = new TaskCompletionSource();
+		var dialog = new ProgressDialog();
+		
+		dialog.DataContext = new ProgressDialogModel(title, async callbacks => {
+			try {
+				await action(dialog, callbacks[0]);
+				taskCompletionSource.SetResult();
+			} catch (Exception e) {
+				taskCompletionSource.SetException(e);
+			}
+		});
+		
+		await dialog.ShowProgressDialog(owner);
+		await taskCompletionSource.Task;
+	}
+	
+	internal static async Task ShowIndeterminate(Window owner, string title, string message, Func<ProgressDialog, Task> action) {
+		var taskCompletionSource = new TaskCompletionSource();
+		var dialog = new ProgressDialog();
+		
+		dialog.DataContext = new ProgressDialogModel(title, async callbacks => {
+			await callbacks[0].UpdateIndeterminate(message);
+			try {
+				await action(dialog);
+				taskCompletionSource.SetResult();
+			} catch (Exception e) {
+				taskCompletionSource.SetException(e);
+			}
+		});
+		
+		await dialog.ShowProgressDialog(owner);
+		await taskCompletionSource.Task;
+	}
+	
+	internal static async Task<T> ShowIndeterminate<T>(Window owner, string title, string message, Func<ProgressDialog, Task<T>> action) {
+		var taskCompletionSource = new TaskCompletionSource<T>();
+		var dialog = new ProgressDialog();
+
+		dialog.DataContext = new ProgressDialogModel(title, async callbacks => {
+			await callbacks[0].UpdateIndeterminate(message);
+			try {
+				taskCompletionSource.SetResult(await action(dialog));
+			} catch (Exception e) {
+				taskCompletionSource.SetException(e);
+			}
+		});
+		
+		await dialog.ShowProgressDialog(owner);
+		return await taskCompletionSource.Task;
+	}
+
 	private bool isFinished = false;
 	private Task progressTask = Task.CompletedTask;
 

app/Desktop/Dialogs/Progress/ProgressDialogModel.cs

@@ -18,9 +18,10 @@ sealed class ProgressDialogModel : BaseModel {
 	[Obsolete("Designer")]
 	public ProgressDialogModel() {}
 
-	public ProgressDialogModel(TaskRunner task, int progressItems = 1) {
+	public ProgressDialogModel(string title, TaskRunner task, int progressItems = 1) {
-		this.Items = Enumerable.Range(0, progressItems).Select(static _ => new ProgressItem()).ToArray();
+		this.Title = title;
 		this.task = task;
+		this.Items = Enumerable.Range(0, progressItems).Select(static _ => new ProgressItem()).ToArray();
 	}
 
 	internal async Task StartTask() {
@@ -43,6 +44,16 @@ sealed class ProgressDialogModel : BaseModel {
 				item.Message = message;
 				item.Items = totalItems == 0 ? string.Empty : finishedItems.Format() + " / " + totalItems.Format();
 				item.Progress = totalItems == 0 ? 0 : 100 * finishedItems / totalItems;
+				item.IsIndeterminate = false;
+			});
+		}
+
+		public async Task UpdateIndeterminate(string message) {
+			await Dispatcher.UIThread.InvokeAsync(() => {
+				item.Message = message;
+				item.Items = string.Empty;
+				item.Progress = 0;
+				item.IsIndeterminate = true;
 			});
 		}
 

app/Desktop/Dialogs/Progress/ProgressItem.cs

@@ -38,4 +38,11 @@ sealed class ProgressItem : BaseModel {
 		get => progress;
 		set => Change(ref progress, value);
 	}
+	
+	private bool isIndeterminate;
+
+	public bool IsIndeterminate {
+		get => isIndeterminate;
+		set => Change(ref isIndeterminate, value);
+	}
 }

app/Desktop/Discord/DiscordAppSettings.cs

@@ -39,7 +39,8 @@ static class DiscordAppSettings {
 
 	public static async Task<bool?> AreDevToolsEnabled() {
 		try {
-			return AreDevToolsEnabled(await ReadSettingsJson());
+			var settingsJson = await ReadSettingsJson().ConfigureAwait(false);
+			return AreDevToolsEnabled(settingsJson);
 		} catch (Exception e) {
 			Log.Error("Cannot read settings file.");
 			Log.Error(e);

app/Desktop/Main/Controls/AttachmentFilterPanelModel.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Threading.Tasks;
 using DHT.Desktop.Common;
 using DHT.Server;
 using DHT.Server.Data.Filters;
@@ -13,17 +14,17 @@ namespace DHT.Desktop.Main.Controls;
 sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 	public sealed record Unit(string Name, uint Scale);
 
-	private static readonly Unit[] AllUnits = {
+	private static readonly Unit[] AllUnits = [
-		new ("B", 1),
+		new Unit("B", 1),
-		new ("kB", 1024),
+		new Unit("kB", 1024),
-		new ("MB", 1024 * 1024)
+		new Unit("MB", 1024 * 1024)
-	};
+	];
 
-	private static readonly HashSet<string> FilterProperties = new () {
+	private static readonly HashSet<string> FilterProperties = [
 		nameof(LimitSize),
 		nameof(MaximumSize),
 		nameof(MaximumSizeUnit)
-	};
+	];
 
 	public string FilterStatisticsText { get; private set; } = "";
 
@@ -51,7 +52,7 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 	private readonly State state;
 	private readonly string verb;
 
-	private readonly AsyncValueComputer<long> matchingAttachmentCountComputer;
+	private readonly RestartableTask<long> matchingAttachmentCountTask;
 	private long? matchingAttachmentCount;
 	private long? totalAttachmentCount;
 
@@ -62,7 +63,7 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 		this.state = state;
 		this.verb = verb;
 
-		this.matchingAttachmentCountComputer = AsyncValueComputer<long>.WithResultProcessor(SetAttachmentCounts).Build();
+		this.matchingAttachmentCountTask = new RestartableTask<long>(SetAttachmentCounts, TaskScheduler.FromCurrentSynchronizationContext());
 
 		UpdateFilterStatistics();
 
@@ -90,14 +91,14 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 	private void UpdateFilterStatistics() {
 		var filter = CreateFilter();
 		if (filter.IsEmpty) {
-			matchingAttachmentCountComputer.Cancel();
+			matchingAttachmentCountTask.Cancel();
 			matchingAttachmentCount = totalAttachmentCount;
 			UpdateFilterStatisticsText();
 		}
 		else {
 			matchingAttachmentCount = null;
 			UpdateFilterStatisticsText();
-			matchingAttachmentCountComputer.Compute(() => state.Db.CountAttachments(filter));
+			matchingAttachmentCountTask.Restart(cancellationToken => state.Db.Downloads.CountAttachments(filter, cancellationToken));
 		}
 	}
 

app/Desktop/Main/Controls/MessageFilterPanelModel.cs

@@ -8,6 +8,7 @@ using Avalonia.Controls;
 using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.CheckBox;
 using DHT.Desktop.Dialogs.Message;
+using DHT.Desktop.Dialogs.Progress;
 using DHT.Server;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
@@ -18,7 +19,7 @@ using DHT.Utils.Tasks;
 namespace DHT.Desktop.Main.Controls;
 
 sealed class MessageFilterPanelModel : BaseModel, IDisposable {
-	private static readonly HashSet<string> FilterProperties = new () {
+	private static readonly HashSet<string> FilterProperties = [
 		nameof(FilterByDate),
 		nameof(StartDate),
 		nameof(EndDate),
@@ -26,7 +27,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		nameof(IncludedChannels),
 		nameof(FilterByUser),
 		nameof(IncludedUsers)
-	};
+	];
 
 	public string FilterStatisticsText { get; private set; } = "";
 
@@ -62,8 +63,8 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		set => Change(ref filterByChannel, value);
 	}
 
-	public HashSet<ulong> IncludedChannels {
+	public HashSet<ulong>? IncludedChannels {
-		get => includedChannels ?? state.Db.GetAllChannels().Select(static channel => channel.Id).ToHashSet();
+		get => includedChannels;
 		set => Change(ref includedChannels, value);
 	}
 
@@ -72,8 +73,8 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		set => Change(ref filterByUser, value);
 	}
 
-	public HashSet<ulong> IncludedUsers {
+	public HashSet<ulong>? IncludedUsers {
-		get => includedUsers ?? state.Db.GetAllUsers().Select(static user => user.Id).ToHashSet();
+		get => includedUsers;
 		set => Change(ref includedUsers, value);
 	}
 
@@ -95,7 +96,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	private readonly State state;
 	private readonly string verb;
 
-	private readonly AsyncValueComputer<long> exportedMessageCountComputer;
+	private readonly RestartableTask<long> exportedMessageCountTask;
 	private long? exportedMessageCount;
 	private long? totalMessageCount;
 
@@ -107,7 +108,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		this.state = state;
 		this.verb = verb;
 
-		this.exportedMessageCountComputer = AsyncValueComputer<long>.WithResultProcessor(SetExportedMessageCount).Build();
+		this.exportedMessageCountTask = new RestartableTask<long>(SetExportedMessageCount, TaskScheduler.FromCurrentSynchronizationContext());
 
 		UpdateFilterStatistics();
 		UpdateChannelFilterLabel();
@@ -118,6 +119,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	}
 
 	public void Dispose() {
+		exportedMessageCountTask.Cancel();
 		state.Db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
 	}
 
@@ -148,17 +150,29 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		}
 	}
 
+	private void UpdateChannelFilterLabel() {
+		long total = state.Db.Statistics.TotalChannels;
+		long included = FilterByChannel && IncludedChannels != null ? IncludedChannels.Count : total;
+		ChannelFilterLabel = "Selected " + included.Format() + " / " + total.Pluralize("channel") + ".";
+	}
+
+	private void UpdateUserFilterLabel() {
+		long total = state.Db.Statistics.TotalUsers;
+		long included = FilterByUser && IncludedUsers != null ? IncludedUsers.Count : total;
+		UserFilterLabel = "Selected " + included.Format() + " / " + total.Pluralize("user") + ".";
+	}
+
 	private void UpdateFilterStatistics() {
 		var filter = CreateFilter();
 		if (filter.IsEmpty) {
-			exportedMessageCountComputer.Cancel();
+			exportedMessageCountTask.Cancel();
 			exportedMessageCount = totalMessageCount;
 			UpdateFilterStatisticsText();
 		}
 		else {
 			exportedMessageCount = null;
 			UpdateFilterStatisticsText();
-			exportedMessageCountComputer.Compute(() => state.Db.CountMessages(filter));
+			exportedMessageCountTask.Restart(cancellationToken => state.Db.Messages.Count(filter, cancellationToken));
 		}
 	}
 
@@ -175,12 +189,12 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		OnPropertyChanged(nameof(FilterStatisticsText));
 	}
 
-	public async void OpenChannelFilterDialog() {
+	public async Task OpenChannelFilterDialog() {
-		var servers = state.Db.GetAllServers().ToDictionary(static server => server.Id);
+		async Task<List<CheckBoxItem<ulong>>> PrepareChannelItems(ProgressDialog dialog) {
 			var items = new List<CheckBoxItem<ulong>>();
-		var included = IncludedChannels;
+			var servers = await state.Db.Servers.Get().ToDictionaryAsync(static server => server.Id);
 
-		foreach (var channel in state.Db.GetAllChannels()) {
+			await foreach (var channel in state.Db.Channels.Get()) {
 				var channelId = channel.Id;
 				var channelName = channel.Name;
 
@@ -210,68 +224,63 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 
 				items.Add(new CheckBoxItem<ulong>(channelId) {
 					Title = title,
-				Checked = included.Contains(channelId)
+					Checked = IncludedChannels == null || IncludedChannels.Contains(channelId)
 				});
 			}
 
-		var result = await OpenIdFilterDialog(window, "Included Channels", items);
+			return items;
+		}
+		
+		const string Title = "Included Channels";
+
+		List<CheckBoxItem<ulong>> items;
+		try {
+			items = await ProgressDialog.ShowIndeterminate(window, Title, "Loading channels...", PrepareChannelItems);
+		} catch (Exception e) {
+			await Dialog.ShowOk(window, Title, "Error loading channels: " + e.Message);
+			return;
+		}
+
+		var result = await OpenIdFilterDialog(Title, items);
 		if (result != null) {
 			IncludedChannels = result;
 		}
 	}
 
-	public async void OpenUserFilterDialog() {
+	public async Task OpenUserFilterDialog() {
-		var items = new List<CheckBoxItem<ulong>>();
+		async Task<List<CheckBoxItem<ulong>>> PrepareUserItems(ProgressDialog dialog) {
-		var included = IncludedUsers;
+			var checkBoxItems = new List<CheckBoxItem<ulong>>();
 
-		foreach (var user in state.Db.GetAllUsers()) {
+			await foreach (var user in state.Db.Users.Get()) {
 				var name = user.Name;
 				var discriminator = user.Discriminator;
 
-			items.Add(new CheckBoxItem<ulong>(user.Id) {
+				checkBoxItems.Add(new CheckBoxItem<ulong>(user.Id) {
 					Title = discriminator == null ? name : name + " #" + discriminator,
-				Checked = included.Contains(user.Id)
+					Checked = IncludedUsers == null || IncludedUsers.Contains(user.Id)
 				});
 			}
 
-		var result = await OpenIdFilterDialog(window, "Included Users", items);
+			return checkBoxItems;
+		}
+
+		const string Title = "Included Users";
+		
+		List<CheckBoxItem<ulong>> items;
+		try {
+			items = await ProgressDialog.ShowIndeterminate(window, Title, "Loading users...", PrepareUserItems);
+		} catch (Exception e) {
+			await Dialog.ShowOk(window, Title, "Error loading users: " + e.Message);
+			return;
+		}
+
+		var result = await OpenIdFilterDialog(Title, items);
 		if (result != null) {
 			IncludedUsers = result;
 		}
 	}
 
-	private void UpdateChannelFilterLabel() {
+	private async Task<HashSet<ulong>?> OpenIdFilterDialog(string title, List<CheckBoxItem<ulong>> items) {
-		long total = state.Db.Statistics.TotalChannels;
-		long included = FilterByChannel ? IncludedChannels.Count : total;
-		ChannelFilterLabel = "Selected " + included.Format() + " / " + total.Pluralize("channel") + ".";
-	}
-
-	private void UpdateUserFilterLabel() {
-		long total = state.Db.Statistics.TotalUsers;
-		long included = FilterByUser ? IncludedUsers.Count : total;
-		UserFilterLabel = "Selected " + included.Format() + " / " + total.Pluralize("user") + ".";
-	}
-
-	public MessageFilter CreateFilter() {
-		MessageFilter filter = new();
-
-		if (FilterByDate) {
-			filter.StartDate = StartDate;
-			filter.EndDate = EndDate?.AddDays(1).AddMilliseconds(-1);
-		}
-
-		if (FilterByChannel) {
-			filter.ChannelIds = new HashSet<ulong>(IncludedChannels);
-		}
-
-		if (FilterByUser) {
-			filter.UserIds = new HashSet<ulong>(IncludedUsers);
-		}
-
-		return filter;
-	}
-
-	private static async Task<HashSet<ulong>?> OpenIdFilterDialog(Window window, string title, List<CheckBoxItem<ulong>> items) {
 		items.Sort(static (item1, item2) => item1.Title.CompareTo(item2.Title));
 
 		var model = new CheckBoxDialogModel<ulong>(items) {
@@ -283,4 +292,23 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 
 		return result == DialogResult.OkCancel.Ok ? model.SelectedItems.Select(static item => item.Item).ToHashSet() : null;
 	}
+
+	public MessageFilter CreateFilter() {
+		MessageFilter filter = new ();
+
+		if (FilterByDate) {
+			filter.StartDate = StartDate;
+			filter.EndDate = EndDate?.AddDays(1).AddMilliseconds(-1);
+		}
+
+		if (FilterByChannel && IncludedChannels != null) {
+			filter.ChannelIds = new HashSet<ulong>(IncludedChannels);
+		}
+
+		if (FilterByUser && IncludedUsers != null) {
+			filter.UserIds = new HashSet<ulong>(IncludedUsers);
+		}
+
+		return filter;
+	}
 }

app/Desktop/Main/Controls/ServerConfigurationPanelModel.cs

@@ -121,9 +121,10 @@ sealed class ServerConfigurationPanelModel : BaseModel, IDisposable {
 
 		ServerConfiguration.Port = port;
 		ServerConfiguration.Token = inputToken;
-		await StartServer();
 		
 		OnPropertyChanged(nameof(HasMadeChanges));
+		
+		await StartServer();
 	}
 
 	public void OnClickCancelChanges() {

app/Desktop/Main/Controls/StatusBarModel.cs

@@ -34,7 +34,7 @@ sealed class StatusBarModel : BaseModel, IDisposable {
 	}
 
 	public void Dispose() {
-		state.Server.StatusChanged += OnServerStatusChanged;
+		state.Server.StatusChanged -= OnServerStatusChanged;
 	}
 
 	private void OnServerStatusChanged(object? sender, ServerManager.Status e) {

app/Desktop/Main/MainWindowModel.cs

@@ -1,5 +1,4 @@
 using System;
-using System.ComponentModel;
 using System.IO;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
@@ -8,6 +7,7 @@ using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Screens;
 using DHT.Desktop.Server;
 using DHT.Server;
+using DHT.Server.Database;
 using DHT.Utils.Logging;
 using DHT.Utils.Models;
 
@@ -25,7 +25,6 @@ sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 	private readonly WelcomeScreen welcomeScreen;
 	private readonly WelcomeScreenModel welcomeScreenModel;
 
-	private MainContentScreen? mainContentScreen;
 	private MainContentScreenModel? mainContentScreenModel;
 
 	private readonly Window window;
@@ -39,11 +38,11 @@ sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 		this.window = window;
 
 		welcomeScreenModel = new WelcomeScreenModel(window);
+		welcomeScreenModel.DatabaseSelected += OnDatabaseSelected;
+
 		welcomeScreen = new WelcomeScreen { DataContext = welcomeScreenModel };
 		CurrentScreen = welcomeScreen;
 
-		welcomeScreenModel.PropertyChanged += WelcomeScreenModelOnPropertyChanged;
-
 		var dbFile = args.DatabaseFile;
 		if (!string.IsNullOrWhiteSpace(dbFile)) {
 			async void OnWindowOpened(object? o, EventArgs eventArgs) {
@@ -74,26 +73,12 @@ sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 		}
 	}
 
-	private async void WelcomeScreenModelOnPropertyChanged(object? sender, PropertyChangedEventArgs e) {
+	private async void OnDatabaseSelected(object? sender, IDatabaseFile db) {
-		if (e.PropertyName == nameof(welcomeScreenModel.Db)) {
+		welcomeScreenModel.DatabaseSelected -= OnDatabaseSelected;
-			if (mainContentScreenModel != null) {
-				mainContentScreenModel.DatabaseClosed -= MainContentScreenModelOnDatabaseClosed;
-				mainContentScreenModel.Dispose();
-			}
 		
-			if (state != null) {
+		await DisposeState();
-				await state.DisposeAsync();
-			}
 		
-			if (welcomeScreenModel.Db == null) {
+		state = new State(db);
-				state = null;
-				Title = DefaultTitle;
-				mainContentScreenModel = null;
-				mainContentScreen = null;
-				CurrentScreen = welcomeScreen;
-			}
-			else {
-				state = new State(welcomeScreenModel.Db);
 
 		try {
 			await state.Server.Start(ServerConfiguration.Port, ServerConfiguration.Token);
@@ -102,33 +87,45 @@ sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 			await Dialog.ShowOk(window, "Internal Server Error", ex.Message);
 		}
 
-				Title = Path.GetFileName(state.Db.Path) + " - " + DefaultTitle;
 		mainContentScreenModel = new MainContentScreenModel(window, state);
-				await mainContentScreenModel.Initialize();
 		mainContentScreenModel.DatabaseClosed += MainContentScreenModelOnDatabaseClosed;
-				mainContentScreen = new MainContentScreen { DataContext = mainContentScreenModel };
-				CurrentScreen = mainContentScreen;
-			}
 		
-			OnPropertyChanged(nameof(CurrentScreen));
+		Title = Path.GetFileName(state.Db.Path) + " - " + DefaultTitle;
+		CurrentScreen = new MainContentScreen { DataContext = mainContentScreenModel };
+
 		OnPropertyChanged(nameof(Title));
+		OnPropertyChanged(nameof(CurrentScreen));
 
 		window.Focus();
 	}
+
+	private async void MainContentScreenModelOnDatabaseClosed(object? sender, EventArgs e) {
+		if (mainContentScreenModel != null) {
+			mainContentScreenModel.DatabaseClosed -= MainContentScreenModelOnDatabaseClosed;
+			mainContentScreenModel.Dispose();
+			mainContentScreenModel = null;
 		}
 
-	private void MainContentScreenModelOnDatabaseClosed(object? sender, EventArgs e) {
+		await DisposeState();
-		welcomeScreenModel.CloseDatabase();
+
+		Title = DefaultTitle;
+		CurrentScreen = welcomeScreen;
+
+		welcomeScreenModel.DatabaseSelected += OnDatabaseSelected;
+		
+		OnPropertyChanged(nameof(Title));
+		OnPropertyChanged(nameof(CurrentScreen));
 	}
 
-	public async ValueTask DisposeAsync() {
+	private async Task DisposeState() {
-		mainContentScreenModel?.Dispose();
-
 		if (state != null) {
 			await state.DisposeAsync();
 			state = null;
 		}
+	}
 
-		welcomeScreenModel.Dispose();
+	public async ValueTask DisposeAsync() {
+		mainContentScreenModel?.Dispose();
+		await DisposeState();
 	}
 }

app/Desktop/Main/Pages/AdvancedPageModel.cs

@@ -1,6 +1,8 @@
 using System;
+using System.Threading.Tasks;
 using Avalonia.Controls;
 using DHT.Desktop.Dialogs.Message;
+using DHT.Desktop.Dialogs.Progress;
 using DHT.Desktop.Main.Controls;
 using DHT.Server;
 using DHT.Utils.Models;
@@ -27,8 +29,9 @@ sealed class AdvancedPageModel : BaseModel, IDisposable {
 		ServerConfigurationModel.Dispose();
 	}
 
-	public async void VacuumDatabase() {
+	public async Task VacuumDatabase() {
-		state.Db.Vacuum();
+		const string Title = "Vacuum Database";
-		await Dialog.ShowOk(window, "Vacuum Database", "Done.");
+		await ProgressDialog.ShowIndeterminate(window, Title, "Vacuuming database...", _ => state.Db.Vacuum());
+		await Dialog.ShowOk(window, Title, "Done.");
 	}
 }

app/Desktop/Main/Pages/AttachmentsPage.axaml

@@ -48,7 +48,7 @@
                 </DataGrid>
             </Expander>
             <StackPanel Orientation="Horizontal" Spacing="10">
-                <Button Command="{Binding OnClickRetryFailedDownloads}" IsEnabled="{Binding HasFailedDownloads}">Retry Failed Downloads</Button>
+                <Button Command="{Binding OnClickRetryFailedDownloads}" IsEnabled="{Binding IsRetryFailedOnDownloadsButtonEnabled}">Retry Failed Downloads</Button>
             </StackPanel>
         </StackPanel>
     </StackPanel>

app/Desktop/Main/Pages/AttachmentsPageModel.cs

@@ -11,12 +11,15 @@ using DHT.Server.Data;
 using DHT.Server.Data.Aggregations;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
+using DHT.Utils.Logging;
 using DHT.Utils.Models;
 using DHT.Utils.Tasks;
 
 namespace DHT.Desktop.Main.Pages;
 
 sealed class AttachmentsPageModel : BaseModel, IDisposable {
+	private static readonly Log Log = Log.ForType<AttachmentsPageModel>();
+
 	private static readonly DownloadItemFilter EnqueuedItemFilter = new () {
 		IncludeStatuses = new HashSet<DownloadStatus> {
 			DownloadStatus.Enqueued,
@@ -24,14 +27,26 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 		}
 	};
 
-	private bool isThreadDownloadButtonEnabled = true;
+	private bool isToggleDownloadButtonEnabled = true;
+
+	public bool IsToggleDownloadButtonEnabled {
+		get => isToggleDownloadButtonEnabled;
+		set => Change(ref isToggleDownloadButtonEnabled, value);
+	}
 
 	public string ToggleDownloadButtonText => IsDownloading ? "Stop Downloading" : "Start Downloading";
 
-	public bool IsToggleDownloadButtonEnabled {
+	private bool isRetryingFailedDownloads = false;
-		get => isThreadDownloadButtonEnabled;
+
-		set => Change(ref isThreadDownloadButtonEnabled, value);
+	public bool IsRetryingFailedDownloads {
+		get => isRetryingFailedDownloads;
+		set {
+			isRetryingFailedDownloads = value;
+			OnPropertyChanged(nameof(IsRetryFailedOnDownloadsButtonEnabled));
 		}
+	}
+
+	public bool IsRetryFailedOnDownloadsButtonEnabled => !IsRetryingFailedDownloads && HasFailedDownloads;
 
 	public string DownloadMessage { get; set; } = "";
 	public double DownloadProgress => totalItemsToDownloadCount is null or 0 ? 0.0 : 100.0 * doneItemsCount / totalItemsToDownloadCount.Value;
@@ -43,26 +58,23 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 	private readonly StatisticsRow statisticsFailed = new ("Failed");
 	private readonly StatisticsRow statisticsSkipped = new ("Skipped");
 
-	public List<StatisticsRow> StatisticsRows {
+	public List<StatisticsRow> StatisticsRows => [
-		get {
-			return new List<StatisticsRow> {
 		statisticsEnqueued,
 		statisticsDownloaded,
 		statisticsFailed,
 		statisticsSkipped
-			};
+	];
-		}
-	}
 
 	public bool IsDownloading => state.Downloader.IsDownloading;
 	public bool HasFailedDownloads => statisticsFailed.Items > 0;
 
 	private readonly State state;
-	private readonly AsyncValueComputer<DownloadStatusStatistics>.Single downloadStatisticsComputer;
+	private readonly ThrottledTask<int> enqueueDownloadItemsTask;
+	private readonly ThrottledTask<DownloadStatusStatistics> downloadStatisticsTask;
 
 	private IDisposable? finishedItemsSubscription;
 	private int doneItemsCount;
-	private int initialFinishedCount;
+	private int totalEnqueuedItemCount;
 	private int? totalItemsToDownloadCount;
 
 	public AttachmentsPageModel() : this(State.Dummy) {}
@@ -72,14 +84,17 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 
 		FilterModel = new AttachmentFilterPanelModel(state);
 
-		downloadStatisticsComputer = AsyncValueComputer<DownloadStatusStatistics>.WithResultProcessor(UpdateStatistics).WithOutdatedResults().BuildWithComputer(state.Db.GetDownloadStatusStatistics);
+		enqueueDownloadItemsTask = new ThrottledTask<int>(OnItemsEnqueued, TaskScheduler.FromCurrentSynchronizationContext());
-		downloadStatisticsComputer.Recompute();
+		downloadStatisticsTask = new ThrottledTask<DownloadStatusStatistics>(UpdateStatistics, TaskScheduler.FromCurrentSynchronizationContext());
+		RecomputeDownloadStatistics();
 
 		state.Db.Statistics.PropertyChanged += OnDbStatisticsChanged;
 	}
 
 	public void Dispose() {
 		state.Db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
+		enqueueDownloadItemsTask.Dispose();
+		downloadStatisticsTask.Dispose();
 		finishedItemsSubscription?.Dispose();
 		FilterModel.Dispose();
 	}
@@ -87,23 +102,107 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 	private void OnDbStatisticsChanged(object? sender, PropertyChangedEventArgs e) {
 		if (e.PropertyName == nameof(DatabaseStatistics.TotalAttachments)) {
 			if (IsDownloading) {
-				EnqueueDownloadItems();
+				EnqueueDownloadItemsLater();
 			}
 			else {
-				downloadStatisticsComputer.Recompute();
+				RecomputeDownloadStatistics();
 			}
 		}
 		else if (e.PropertyName == nameof(DatabaseStatistics.TotalDownloads)) {
-			downloadStatisticsComputer.Recompute();
+			RecomputeDownloadStatistics();
 		}
 	}
 
-	private void EnqueueDownloadItems() {
+	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;
-		state.Db.EnqueueDownloadItems(filter);
+		return filter;
+	}
 
-		downloadStatisticsComputer.Recompute();
+	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();
+		RecomputeDownloadStatistics();
+	}
+
+	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) {
@@ -125,9 +224,9 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 
 		if (hadFailedDownloads != HasFailedDownloads) {
 			OnPropertyChanged(nameof(HasFailedDownloads));
+			OnPropertyChanged(nameof(IsRetryFailedOnDownloadsButtonEnabled));
 		}
 
-		totalItemsToDownloadCount = statisticsEnqueued.Items + statisticsDownloaded.Items + statisticsFailed.Items - initialFinishedCount;
 		UpdateDownloadMessage();
 	}
 
@@ -138,65 +237,6 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 		OnPropertyChanged(nameof(DownloadProgress));
 	}
 
-	private void OnItemsFinished(int finishedItemCount) {
-		doneItemsCount += finishedItemCount;
-		UpdateDownloadMessage();
-		downloadStatisticsComputer.Recompute();
-	}
-
-	public async Task OnClickToggleDownload() {
-		IsToggleDownloadButtonEnabled = false;
-		
-		if (IsDownloading) {
-			await state.Downloader.Stop();
-			
-			finishedItemsSubscription?.Dispose();
-			finishedItemsSubscription = null;
-			
-			downloadStatisticsComputer.Recompute();
-
-			state.Db.RemoveDownloadItems(EnqueuedItemFilter, FilterRemovalMode.RemoveMatching);
-
-			doneItemsCount = 0;
-			initialFinishedCount = 0;
-			totalItemsToDownloadCount = null;
-			UpdateDownloadMessage();
-		}
-		else {
-			var finishedItems = await state.Downloader.Start();
-
-			initialFinishedCount = statisticsDownloaded.Items + statisticsFailed.Items;
-			finishedItemsSubscription = finishedItems.Select(static _ => true)
-			                                         .Buffer(TimeSpan.FromMilliseconds(100))
-			                                         .Select(static items => items.Count)
-			                                         .Where(static items => items > 0)
-			                                         .ObserveOn(AvaloniaScheduler.Instance)
-			                                         .Subscribe(OnItemsFinished);
-			
-			EnqueueDownloadItems();
-		}
-
-		OnPropertyChanged(nameof(ToggleDownloadButtonText));
-		OnPropertyChanged(nameof(IsDownloading));
-		IsToggleDownloadButtonEnabled = true;
-	}
-
-	public void OnClickRetryFailedDownloads() {
-		var allExceptFailedFilter = new DownloadItemFilter {
-			IncludeStatuses = new HashSet<DownloadStatus> {
-				DownloadStatus.Enqueued,
-				DownloadStatus.Downloading,
-				DownloadStatus.Success
-			}
-		};
-
-		state.Db.RemoveDownloadItems(allExceptFailedFilter, FilterRemovalMode.KeepMatching);
-
-		if (IsDownloading) {
-			EnqueueDownloadItems();
-		}
-	}
-
 	public sealed class StatisticsRow {
 		public string State { get; }
 		public int Items { get; set; }

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;
+using DHT.Server.Database.Sqlite.Utils;
 using DHT.Utils.Logging;
 using DHT.Utils.Models;
 
@@ -41,7 +41,7 @@ sealed class DatabasePageModel : BaseModel {
 		this.Db = state.Db;
 	}
 
-	public async void OpenDatabaseFolder() {
+	public async Task OpenDatabaseFolder() {
 		string file = Db.Path;
 		string? folder = Path.GetDirectoryName(file);
 
@@ -72,18 +72,11 @@ sealed class DatabasePageModel : BaseModel {
 		DatabaseClosed?.Invoke(this, EventArgs.Empty);
 	}
 
-	public async void MergeWithDatabase() {
+	public async Task MergeWithDatabase() {
 		var paths = await DatabaseGui.NewOpenDatabaseFilesDialog(window, Path.GetDirectoryName(Db.Path));
-		if (paths.Length == 0) {
+		if (paths.Length > 0) {
-			return;
+			await ProgressDialog.Show(window, "Database Merge", async (dialog, callback) => await MergeWithDatabaseFromPaths(Db, paths, dialog, callback));
 		}
-
-		ProgressDialog progressDialog = new ProgressDialog();
-		progressDialog.DataContext = new ProgressDialogModel(async callbacks => await MergeWithDatabaseFromPaths(Db, paths, progressDialog, callbacks[0])) {
-			Title = "Database Merge"
-		};
-
-		await progressDialog.ShowProgressDialog(window);
 	}
 
 	private static async Task MergeWithDatabaseFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
@@ -97,7 +90,7 @@ sealed class DatabasePageModel : BaseModel {
 			}
 
 			try {
-				target.AddFrom(db);
+				await target.AddFrom(db);
 				return true;
 			} finally {
 				db.Dispose();
@@ -140,23 +133,16 @@ sealed class DatabasePageModel : BaseModel {
 		}
 	}
 
-	public async void ImportLegacyArchive() {
+	public async Task ImportLegacyArchive() {
 		var paths = await window.StorageProvider.OpenFiles(new FilePickerOpenOptions {
 			Title = "Open Legacy DHT Archive",
 			SuggestedStartLocation = await FileDialogs.GetSuggestedStartLocation(window, Path.GetDirectoryName(Db.Path)),
 			AllowMultiple = true
 		});
 
-		if (paths.Length == 0) {
+		if (paths.Length > 0) {
-			return;
+			await ProgressDialog.Show(window, "Legacy Archive Import", async (dialog, callback) => await ImportLegacyArchiveFromPaths(Db, paths, dialog, callback));
 		}
-
-		ProgressDialog progressDialog = new ProgressDialog();
-		progressDialog.DataContext = new ProgressDialogModel(async callbacks => await ImportLegacyArchiveFromPaths(Db, paths, progressDialog, callbacks[0])) {
-			Title = "Legacy Archive Import"
-		};
-
-		await progressDialog.ShowProgressDialog(window);
 	}
 
 	private static async Task ImportLegacyArchiveFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
@@ -208,7 +194,7 @@ sealed class DatabasePageModel : BaseModel {
 
 	private static async Task PerformImport(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback, string neutralDialogTitle, string errorDialogTitle, string itemName, Func<string, Task<bool>> performImport) {
 		int total = paths.Length;
-		var oldStatistics = target.SnapshotStatistics();
+		var oldStatistics = await target.SnapshotStatistics();
 
 		int successful = 0;
 		int finished = 0;
@@ -239,7 +225,8 @@ sealed class DatabasePageModel : BaseModel {
 			return;
 		}
 
-		await Dialog.ShowOk(dialog, neutralDialogTitle, GetImportDialogMessage(oldStatistics, target.SnapshotStatistics(), successful, total, itemName));
+		var newStatistics = await target.SnapshotStatistics();
+		await Dialog.ShowOk(dialog, neutralDialogTitle, GetImportDialogMessage(oldStatistics, newStatistics, successful, total, itemName));
 	}
 
 	private static string GetImportDialogMessage(DatabaseStatisticsSnapshot oldStatistics, DatabaseStatisticsSnapshot newStatistics, int successfulItems, int totalItems, string itemName) {

app/Desktop/Main/Pages/DebugPageModel.cs

@@ -44,13 +44,7 @@ namespace DHT.Desktop.Main.Pages {
 				return;
 			}
 
-			ProgressDialog progressDialog = new ProgressDialog {
+			await ProgressDialog.Show(window, "Generating Random Data", async (_, callback) => await GenerateRandomData(channels, users, messages, callback));
-				DataContext = new ProgressDialogModel(async callbacks => await GenerateRandomData(channels, users, messages, callbacks[0])) {
-					Title = "Generating Random Data"
-				}
-			};
-
-			await progressDialog.ShowProgressDialog(window);
 		}
 
 		private const int BatchSize = 500;
@@ -83,12 +77,9 @@ namespace DHT.Desktop.Main.Pages {
 				Discriminator = rand.Next(0, 9999).ToString(),
 			}).ToArray();
 
-			state.Db.AddServer(server);
+			await state.Db.Users.Add(users);
-			state.Db.AddUsers(users);
+			await state.Db.Servers.Add([server]);
-
+			await state.Db.Channels.Add(channels);
-			foreach (var channel in channels) {
-				state.Db.AddChannel(channel);
-			}
 
 			var now = DateTimeOffset.Now;
 			int batchIndex = 0;
@@ -111,13 +102,13 @@ namespace DHT.Desktop.Main.Pages {
 						Timestamp = timeMillis,
 						EditTimestamp = editMillis,
 						RepliedToId = null,
-						Attachments = ImmutableArray<Attachment>.Empty,
+						Attachments = ImmutableList<Attachment>.Empty,
-						Embeds = ImmutableArray<Embed>.Empty,
+						Embeds = ImmutableList<Embed>.Empty,
-						Reactions = ImmutableArray<Reaction>.Empty,
+						Reactions = ImmutableList<Reaction>.Empty,
 					};
 				}).ToArray();
 
-				state.Db.AddMessages(messages);
+				await state.Db.Messages.Add(messages);
 
 				messageCount -= BatchSize;
 				await callback.Update("Adding messages in batches of " + BatchSize, ++batchIndex, batchCount);

app/Desktop/Main/Pages/TrackingPage.axaml

@@ -16,7 +16,7 @@
             To start tracking messages, copy the tracking script and paste it into the console of either the Discord app, or your browser. The console is usually opened by pressing Ctrl+Shift+I.
         </TextBlock>
         <StackPanel DockPanel.Dock="Left" Orientation="Horizontal" Spacing="10">
-            <Button x:Name="CopyTrackingScript" Click="CopyTrackingScriptButton_OnClick">Copy Tracking Script</Button>
+            <Button x:Name="CopyTrackingScript" Click="CopyTrackingScriptButton_OnClick" IsEnabled="{Binding IsCopyTrackingScriptButtonEnabled}">Copy Tracking Script</Button>
         </StackPanel>
         <TextBlock TextWrapping="Wrap" Margin="0 5 0 0">
             By default, the Discord app does not allow opening the console. The button below will change a hidden setting in the Discord app that controls whether the Ctrl+Shift+I shortcut is enabled.

app/Desktop/Main/Pages/TrackingPageModel.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 using System.Web;
 using Avalonia.Controls;
@@ -11,9 +12,16 @@ using static DHT.Desktop.Program;
 namespace DHT.Desktop.Main.Pages;
 
 sealed class TrackingPageModel : BaseModel {
-	private bool areDevToolsEnabled;
+	private bool isCopyTrackingScriptButtonEnabled = true;
 
-	private bool AreDevToolsEnabled {
+	public bool IsCopyTrackingScriptButtonEnabled {
+		get => isCopyTrackingScriptButtonEnabled;
+		set => Change(ref isCopyTrackingScriptButtonEnabled, value);
+	}
+
+	private bool? areDevToolsEnabled;
+
+	private bool? AreDevToolsEnabled {
 		get => areDevToolsEnabled;
 		set {
 			Change(ref areDevToolsEnabled, value);
@@ -21,15 +29,19 @@ sealed class TrackingPageModel : BaseModel {
 		}
 	}
 
-	public bool IsToggleAppDevToolsButtonEnabled { get; private set; } = true;
+	public bool IsToggleAppDevToolsButtonEnabled { get; private set; } = false;
 
 	public string ToggleAppDevToolsButtonText {
 		get {
+			if (!AreDevToolsEnabled.HasValue) {
+				return "Loading...";
+			}
+
 			if (!IsToggleAppDevToolsButtonEnabled) {
 				return "Unavailable";
 			}
 
-			return AreDevToolsEnabled ? "Disable Ctrl+Shift+I" : "Enable Ctrl+Shift+I";
+			return AreDevToolsEnabled.Value ? "Disable Ctrl+Shift+I" : "Enable Ctrl+Shift+I";
 		}
 	}
 
@@ -40,20 +52,21 @@ sealed class TrackingPageModel : BaseModel {
 
 	public TrackingPageModel(Window window) {
 		this.window = window;
-	}
 
-	public async Task Initialize() {
+		Task.Factory.StartNew(InitializeDevToolsToggle, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.FromCurrentSynchronizationContext());
-		bool? devToolsEnabled = await DiscordAppSettings.AreDevToolsEnabled();
-		if (devToolsEnabled.HasValue) {
-			AreDevToolsEnabled = devToolsEnabled.Value;
-		}
-		else {
-			IsToggleAppDevToolsButtonEnabled = false;
-			OnPropertyChanged(nameof(IsToggleAppDevToolsButtonEnabled));
-		}
 	}
 
 	public async Task<bool> OnClickCopyTrackingScript() {
+		IsCopyTrackingScriptButtonEnabled = false;
+
+		try {
+			return await CopyTrackingScript();
+		} finally {
+			IsCopyTrackingScriptButtonEnabled = true;
+		}
+	}
+
+	private async Task<bool> CopyTrackingScript() {
 		string url = $"http://127.0.0.1:{ServerConfiguration.Port}/get-tracking-script?token={HttpUtility.UrlEncode(ServerConfiguration.Token)}";
 		string script = (await Resources.ReadTextAsync("tracker-loader.js")).Trim().Replace("{url}", url);
 
@@ -72,10 +85,28 @@ sealed class TrackingPageModel : BaseModel {
 		}
 	}
 
-	public async void OnClickToggleAppDevTools() {
+	private async Task InitializeDevToolsToggle() {
+		bool? devToolsEnabled = await DiscordAppSettings.AreDevToolsEnabled();
+
+		if (devToolsEnabled.HasValue) {
+			IsToggleAppDevToolsButtonEnabled = true;
+			AreDevToolsEnabled = devToolsEnabled.Value;
+		}
+		else {
+			IsToggleAppDevToolsButtonEnabled = false;
+		}
+
+		OnPropertyChanged(nameof(IsToggleAppDevToolsButtonEnabled));
+	}
+
+	public async Task OnClickToggleAppDevTools() {
 		const string DialogTitle = "Discord App Settings File";
 
-		bool oldState = AreDevToolsEnabled;
+		if (!AreDevToolsEnabled.HasValue) {
+			return;
+		}
+
+		bool oldState = AreDevToolsEnabled.Value;
 		bool newState = !oldState;
 
 		switch (await DiscordAppSettings.ConfigureDevTools(newState)) {

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -11,6 +11,7 @@ using Avalonia.Platform.Storage;
 using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.File;
 using DHT.Desktop.Dialogs.Message;
+using DHT.Desktop.Dialogs.Progress;
 using DHT.Desktop.Main.Controls;
 using DHT.Desktop.Server;
 using DHT.Server;
@@ -23,7 +24,11 @@ using static DHT.Desktop.Program;
 namespace DHT.Desktop.Main.Pages;
 
 sealed class ViewerPageModel : BaseModel, IDisposable {
-	public static readonly ConcurrentBag<string> TemporaryFiles = new ();
+	public static readonly ConcurrentBag<string> TemporaryFiles = [];
+
+	private static readonly FilePickerFileType[] ViewerFileTypes = [
+		FileDialogs.CreateFilter("Discord History Viewer", ["html"])
+	];
 
 	public bool DatabaseToolFilterModeKeep { get; set; } = true;
 	public bool DatabaseToolFilterModeRemove { get; set; } = false;
@@ -59,6 +64,58 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 		HasFilters = FilterModel.HasAnyFilters;
 	}
 
+	public async void OnClickOpenViewer() {
+		try {
+			var fullPath = await PrepareTemporaryViewerFile();
+			var strategy = new LiveViewerExportStrategy(ServerConfiguration.Port, ServerConfiguration.Token);
+
+			await WriteViewerFile(fullPath, strategy);
+			Process.Start(new ProcessStartInfo(fullPath) { UseShellExecute = true });
+		} catch (Exception e) {
+			await Dialog.ShowOk(window, "Open Viewer", "Could not save viewer: " + e.Message);
+		}
+	}
+
+	private async Task<string> PrepareTemporaryViewerFile() {
+		return await Task.Run(() => {
+			string rootPath = Path.Combine(Path.GetTempPath(), "DiscordHistoryTracker");
+			string filenameBase = Path.GetFileNameWithoutExtension(state.Db.Path) + "-" + DateTime.Now.ToString("yyyy-MM-dd");
+			string fullPath = Path.Combine(rootPath, filenameBase + ".html");
+			
+			int counter = 0;
+
+			while (File.Exists(fullPath)) {
+				++counter;
+				fullPath = Path.Combine(rootPath, filenameBase + "-" + counter + ".html");
+			}
+
+			TemporaryFiles.Add(fullPath);
+
+			Directory.CreateDirectory(rootPath);
+
+			return fullPath;
+		});
+	}
+
+	public async void OnClickSaveViewer() {
+		string? path = await window.StorageProvider.SaveFile(new FilePickerSaveOptions {
+			Title = "Save Viewer",
+			FileTypeChoices = ViewerFileTypes,
+			SuggestedFileName = Path.GetFileNameWithoutExtension(state.Db.Path) + ".html",
+			SuggestedStartLocation = await FileDialogs.GetSuggestedStartLocation(window, Path.GetDirectoryName(state.Db.Path)),
+		});
+
+		if (path == null) {
+			return;
+		}
+
+		try {
+			await WriteViewerFile(path, StandaloneViewerExportStrategy.Instance);
+		} catch (Exception e) {
+			await Dialog.ShowOk(window, "Save Viewer", "Could not save viewer: " + e.Message);
+		}
+	}
+
 	private async Task WriteViewerFile(string path, IViewerExportStrategy strategy) {
 		const string ArchiveTag = "/*[ARCHIVE]*/";
 
@@ -96,54 +153,23 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 		File.Delete(jsonTempFile);
 	}
 
-	public async void OnClickOpenViewer() {
+	public async Task OnClickApplyFiltersToDatabase() {
-		string rootPath = Path.Combine(Path.GetTempPath(), "DiscordHistoryTracker");
-		string filenameBase = Path.GetFileNameWithoutExtension(state.Db.Path) + "-" + DateTime.Now.ToString("yyyy-MM-dd");
-		string fullPath = Path.Combine(rootPath, filenameBase + ".html");
-		int counter = 0;
-
-		while (File.Exists(fullPath)) {
-			++counter;
-			fullPath = Path.Combine(rootPath, filenameBase + "-" + counter + ".html");
-		}
-
-		TemporaryFiles.Add(fullPath);
-
-		Directory.CreateDirectory(rootPath);
-		await WriteViewerFile(fullPath, new LiveViewerExportStrategy(ServerConfiguration.Port, ServerConfiguration.Token));
-
-		Process.Start(new ProcessStartInfo(fullPath) { UseShellExecute = true });
-	}
-
-	private static readonly FilePickerFileType[] ViewerFileTypes = {
-		FileDialogs.CreateFilter("Discord History Viewer", new string[] { "html" }),
-	};
-	
-	public async void OnClickSaveViewer() {
-		string? path = await window.StorageProvider.SaveFile(new FilePickerSaveOptions {
-			Title = "Save Viewer",
-			FileTypeChoices = ViewerFileTypes,
-			SuggestedFileName = Path.GetFileNameWithoutExtension(state.Db.Path) + ".html",
-			SuggestedStartLocation = await FileDialogs.GetSuggestedStartLocation(window, Path.GetDirectoryName(state.Db.Path)),
-		});
-
-		if (path != null) {
-			await WriteViewerFile(path, StandaloneViewerExportStrategy.Instance);
-		}
-	}
-
-	public async void OnClickApplyFiltersToDatabase() {
 		var filter = FilterModel.CreateFilter();
+		var messageCount = await ProgressDialog.ShowIndeterminate(window, "Apply Filters", "Counting matching messages...", _ => state.Db.Messages.Count(filter));
 
 		if (DatabaseToolFilterModeKeep) {
-			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Keep Matching Messages in This Database", state.Db.CountMessages(filter).Pluralize("message") + " will be kept, and the rest will be removed from this database. This action cannot be undone. Proceed?")) {
+			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Keep Matching Messages in This Database", messageCount.Pluralize("message") + " will be kept, and the rest will be removed from this database. This action cannot be undone. Proceed?")) {
-				state.Db.RemoveMessages(filter, FilterRemovalMode.KeepMatching);
+				await ApplyFilterToDatabase(filter, FilterRemovalMode.KeepMatching);
 			}
 		}
 		else if (DatabaseToolFilterModeRemove) {
-			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Remove Matching Messages in This Database", state.Db.CountMessages(filter).Pluralize("message") + " will be removed from this database. This action cannot be undone. Proceed?")) {
+			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Remove Matching Messages in This Database", messageCount.Pluralize("message") + " will be removed from this database. This action cannot be undone. Proceed?")) {
-				state.Db.RemoveMessages(filter, FilterRemovalMode.RemoveMatching);
+				await ApplyFilterToDatabase(filter, FilterRemovalMode.RemoveMatching);
 			}
 		}
 	}
+
+	private async Task ApplyFilterToDatabase(MessageFilter filter, FilterRemovalMode removalMode) {
+		await ProgressDialog.ShowIndeterminate(window, "Apply Filters", "Removing messages...", _ => state.Db.Messages.Remove(filter, removalMode));
+	}
 }

app/Desktop/Main/Screens/MainContentScreenModel.cs

@@ -1,16 +1,12 @@
 using System;
-using System.Threading.Tasks;
 using Avalonia.Controls;
 using DHT.Desktop.Main.Controls;
 using DHT.Desktop.Main.Pages;
 using DHT.Server;
-using DHT.Utils.Logging;
 
 namespace DHT.Desktop.Main.Screens;
 
 sealed class MainContentScreenModel : IDisposable {
-	private static readonly Log Log = Log.ForType<MainContentScreenModel>();
-
 	public DatabasePage DatabasePage { get; }
 	private DatabasePageModel DatabasePageModel { get; }
 
@@ -75,10 +71,6 @@ sealed class MainContentScreenModel : IDisposable {
 		StatusBarModel = new StatusBarModel(state);
 	}
 
-	public async Task Initialize() {
-		await TrackingPageModel.Initialize();
-	}
-
 	public void Dispose() {
 		AttachmentsPageModel.Dispose();
 		ViewerPageModel.Dispose();

app/Desktop/Main/Screens/WelcomeScreen.axaml

@@ -32,7 +32,7 @@
             <TextBlock Text="{Binding Version, StringFormat=Discord History Tracker v{0}}" FontSize="25" Margin="0 0 0 30" HorizontalAlignment="Center" />
 
             <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
-                <Button Command="{Binding OpenOrCreateDatabase}">Open or Create Database</Button>
+                <Button Command="{Binding OpenOrCreateDatabase}" IsEnabled="{Binding IsOpenOrCreateDatabaseButtonEnabled}">Open or Create Database</Button>
                 <Button Command="{Binding ShowAboutDialog}">About</Button>
                 <Button Command="{Binding Exit}">Exit</Button>
             </StackPanel>

app/Desktop/Main/Screens/WelcomeScreenModel.cs

@@ -7,16 +7,22 @@ using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Dialogs.Progress;
 using DHT.Server.Database;
-using DHT.Server.Database.Sqlite;
+using DHT.Server.Database.Sqlite.Utils;
 using DHT.Utils.Models;
 
 namespace DHT.Desktop.Main.Screens;
 
-sealed class WelcomeScreenModel : BaseModel, IDisposable {
+sealed class WelcomeScreenModel : BaseModel {
 	public string Version => Program.Version;
 	
-	public IDatabaseFile? Db { get; private set; }
+	private bool isOpenOrCreateDatabaseButtonEnabled = true;
-	public bool HasDatabase => Db != null;
+	
+	public bool IsOpenOrCreateDatabaseButtonEnabled {
+		get => isOpenOrCreateDatabaseButtonEnabled;
+		set => Change(ref isOpenOrCreateDatabaseButtonEnabled, value);
+	}
+	
+	public event EventHandler<IDatabaseFile>? DatabaseSelected; 
 	
 	private readonly Window window;
 
@@ -29,23 +35,25 @@ sealed class WelcomeScreenModel : BaseModel, IDisposable {
 		this.window = window;
 	}
 
-	public async void OpenOrCreateDatabase() {
+	public async Task OpenOrCreateDatabase() {
+		IsOpenOrCreateDatabaseButtonEnabled = false;
+		try {
 			var path = await DatabaseGui.NewOpenOrCreateDatabaseFileDialog(window, Path.GetDirectoryName(dbFilePath));
 			if (path != null) {
 				await OpenOrCreateDatabaseFromPath(path);
 			}
+		} finally {
+			IsOpenOrCreateDatabaseButtonEnabled = true;
+		}
 	}
 
 	public async Task OpenOrCreateDatabaseFromPath(string path) {
-		if (Db != null) {
-			Db = null;
-		}
-
 		dbFilePath = path;
-		Db = await DatabaseGui.TryOpenOrCreateDatabaseFromPath(path, window, new SchemaUpgradeCallbacks(window));
 		
-		OnPropertyChanged(nameof(Db));
+		var db = await DatabaseGui.TryOpenOrCreateDatabaseFromPath(path, window, new SchemaUpgradeCallbacks(window));
-		OnPropertyChanged(nameof(HasDatabase));
+		if (db != null) {
+			DatabaseSelected?.Invoke(this, db);
+		}
 	}
 
 	private sealed class SchemaUpgradeCallbacks : ISchemaUpgradeCallbacks {
@@ -68,11 +76,7 @@ sealed class WelcomeScreenModel : BaseModel, IDisposable {
 				await Task.Delay(TimeSpan.FromMilliseconds(600));
 			}
 			
-			await new ProgressDialog {
+			await new ProgressDialog { DataContext = new ProgressDialogModel("Upgrading Database", StartUpgrade, progressItems: 3) }.ShowProgressDialog(window);
-				DataContext = new ProgressDialogModel(StartUpgrade, progressItems: 3) {
-					Title = "Upgrading Database"
-				}
-			}.ShowProgressDialog(window);
 		}
 
 		private sealed class ProgressReporter : ISchemaUpgradeCallbacks.IProgressReporter {
@@ -109,22 +113,11 @@ sealed class WelcomeScreenModel : BaseModel, IDisposable {
 		}
 	}
 
-	public void CloseDatabase() {
+	public async Task ShowAboutDialog() {
-		Dispose();
+		await new AboutWindow { DataContext = new AboutWindowModel() }.ShowDialog(window);
-		OnPropertyChanged(nameof(Db));
-		OnPropertyChanged(nameof(HasDatabase));
-	}
-
-	public async void ShowAboutDialog() {
-		await new AboutWindow { DataContext = new AboutWindowModel() }.ShowDialog(this.window);
 	}
 
 	public void Exit() {
 		window.Close();
 	}
-
-	public void Dispose() {
-		Db?.Dispose();
-		Db = null;
-	}
 }

app/Server/Data/Message.cs

@@ -10,7 +10,7 @@ public readonly struct Message {
 	public long Timestamp { get; init; }
 	public long? EditTimestamp { get; init; }
 	public ulong? RepliedToId { get; init; }
-	public ImmutableArray<Attachment> Attachments { get; init; }
+	public ImmutableList<Attachment> Attachments { get; init; }
-	public ImmutableArray<Embed> Embeds { get; init; }
+	public ImmutableList<Embed> Embeds { get; init; }
-	public ImmutableArray<Reaction> Reactions { get; init; }
+	public ImmutableList<Reaction> Reactions { get; init; }
 }

app/Server/Database/DatabaseExtensions.cs

@@ -1,29 +1,32 @@
 using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
 using DHT.Server.Data;
 
 namespace DHT.Server.Database;
 
 public static class DatabaseExtensions {
-	public static void AddFrom(this IDatabaseFile target, IDatabaseFile source) {
+	public static async Task AddFrom(this IDatabaseFile target, IDatabaseFile source) {
-		target.AddServers(source.GetAllServers());
+		await target.Users.Add(await source.Users.Get().ToListAsync());
-		target.AddChannels(source.GetAllChannels());
+		await target.Servers.Add(await source.Servers.Get().ToListAsync());
-		target.AddUsers(source.GetAllUsers().ToArray());
+		await target.Channels.Add(await source.Channels.Get().ToListAsync());
-		target.AddMessages(source.GetMessages().ToArray());
 
-		foreach (var download in source.GetDownloadsWithoutData()) {
+		const int MessageBatchSize = 100;
-			target.AddDownload(download.Status == DownloadStatus.Success ? source.GetDownloadWithData(download) : download);
+		List<Message> batchedMessages = new (MessageBatchSize);
+		
+		await foreach (var message in source.Messages.Get()) {
+			batchedMessages.Add(message);
+
+			if (batchedMessages.Count >= MessageBatchSize) {
+				await target.Messages.Add(batchedMessages);
+				batchedMessages.Clear();
 			}
 		}
 		
-	internal static void AddServers(this IDatabaseFile target, IEnumerable<Data.Server> servers) {
+		await target.Messages.Add(batchedMessages);
-		foreach (var server in servers) {
-			target.AddServer(server);
-		}
-	}
 
-	internal static void AddChannels(this IDatabaseFile target, IEnumerable<Channel> channels) {
+		await foreach (var download in source.Downloads.GetWithoutData()) {
-		foreach (var channel in channels) {
+			await target.Downloads.AddDownload(download.Status == DownloadStatus.Success ? await source.Downloads.HydrateWithData(download) : download);
-			target.AddChannel(channel);
 		}
 	}
 }

app/Server/Database/DummyDatabaseFile.cs

@@ -1,90 +1,31 @@
-using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using DHT.Server.Data;
+using System.Threading.Tasks;
-using DHT.Server.Data.Aggregations;
+using DHT.Server.Database.Repositories;
-using DHT.Server.Data.Filters;
-using DHT.Server.Download;
 
 namespace DHT.Server.Database;
 
 [SuppressMessage("ReSharper", "ArrangeObjectCreationWhenTypeNotEvident")]
-public sealed class DummyDatabaseFile : IDatabaseFile {
+sealed class DummyDatabaseFile : IDatabaseFile {
 	public static DummyDatabaseFile Instance { get; } = new ();
 
 	public string Path => "";
 	public DatabaseStatistics Statistics { get; } = new ();
 	
+	public IUserRepository Users { get; } = new IUserRepository.Dummy();
+	public IServerRepository Servers { get; } = new IServerRepository.Dummy();
+	public IChannelRepository Channels { get; } = new IChannelRepository.Dummy();
+	public IMessageRepository Messages { get; } = new IMessageRepository.Dummy();
+	public IDownloadRepository Downloads { get; } = new IDownloadRepository.Dummy();
+	
 	private DummyDatabaseFile() {}
 
-	public DatabaseStatisticsSnapshot SnapshotStatistics() {
+	public Task<DatabaseStatisticsSnapshot> SnapshotStatistics() {
-		return new();
+		return Task.FromResult(new DatabaseStatisticsSnapshot());
 	}
 
-	public void AddServer(Data.Server server) {}
+	public Task Vacuum() {
-
+		return Task.CompletedTask;
-	public List<Data.Server> GetAllServers() {
-		return new();
 	}
 
-	public void AddChannel(Channel channel) {}
-
-	public List<Channel> GetAllChannels() {
-		return new();
-	}
-
-	public void AddUsers(User[] users) {}
-
-	public List<User> GetAllUsers() {
-		return new();
-	}
-
-	public void AddMessages(Message[] messages) {}
-
-	public int CountMessages(MessageFilter? filter = null) {
-		return 0;
-	}
-
-	public List<Message> GetMessages(MessageFilter? filter = null) {
-		return new();
-	}
-
-	public HashSet<ulong> GetMessageIds(MessageFilter? filter = null) {
-		return new();
-	}
-
-	public void RemoveMessages(MessageFilter filter, FilterRemovalMode mode) {}
-
-	public int CountAttachments(AttachmentFilter? filter = null) {
-		return new();
-	}
-
-	public List<Data.Download> GetDownloadsWithoutData() {
-		return new();
-	}
-
-	public Data.Download GetDownloadWithData(Data.Download download) {
-		return download;
-	}
-
-	public DownloadedAttachment? GetDownloadedAttachment(string url) {
-		return null;
-	}
-
-	public void AddDownload(Data.Download download) {}
-
-	public void EnqueueDownloadItems(AttachmentFilter? filter = null) {}
-
-	public List<DownloadItem> PullEnqueuedDownloadItems(int count) {
-		return new();
-	}
-
-	public void RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {}
-
-	public DownloadStatusStatistics GetDownloadStatusStatistics() {
-		return new();
-	}
-
-	public void Vacuum() {}
-
 	public void Dispose() {}
 }

app/Server/Database/Export/ViewerJsonExport.cs

@@ -21,7 +21,7 @@ public static class ViewerJsonExport {
 		var includedChannelIds = new HashSet<ulong>();
 		var includedServerIds = new HashSet<ulong>();
 
-		var includedMessages = db.GetMessages(filter);
+		var includedMessages = await db.Messages.Get(filter).ToListAsync();
 		var includedChannels = new List<Channel>();
 
 		foreach (var message in includedMessages) {
@@ -29,23 +29,23 @@ public static class ViewerJsonExport {
 			includedChannelIds.Add(message.Channel);
 		}
 
-		foreach (var channel in db.GetAllChannels()) {
+		await foreach (var channel in db.Channels.Get()) {
 			if (includedChannelIds.Contains(channel.Id)) {
 				includedChannels.Add(channel);
 				includedServerIds.Add(channel.Server);
 			}
 		}
 
-		var users = GenerateUserList(db, includedUserIds, out var userindex, out var userIndices);
+		var (users, userIndex, userIndices) = await GenerateUserList(db, includedUserIds);
-		var servers = GenerateServerList(db, includedServerIds, out var serverindex);
+		var (servers, serverIndices) = await GenerateServerList(db, includedServerIds);
-		var channels = GenerateChannelList(includedChannels, serverindex);
+		var channels = GenerateChannelList(includedChannels, serverIndices);
 
 		perf.Step("Collect database data");
 
 		var value = new ViewerJson {
 			Meta = new ViewerJson.JsonMeta {
 				Users = users,
-				Userindex = userindex,
+				Userindex = userIndex,
 				Servers = servers,
 				Channels = channels
 			},
@@ -60,12 +60,12 @@ public static class ViewerJsonExport {
 		perf.End();
 	}
 
-	private static Dictionary<Snowflake, ViewerJson.JsonUser> GenerateUserList(IDatabaseFile db, HashSet<ulong> userIds, out List<Snowflake> userindex, out Dictionary<ulong, int> userIndices) {
+	private static async Task<(Dictionary<Snowflake, ViewerJson.JsonUser> Users, List<Snowflake> UserIndex, Dictionary<ulong, int> UserIndices)> GenerateUserList(IDatabaseFile db, HashSet<ulong> userIds) {
 		var users = new Dictionary<Snowflake, ViewerJson.JsonUser>();
-		userindex = new List<Snowflake>();
+		var userIndex = new List<Snowflake>();
-		userIndices = new Dictionary<ulong, int>();
+		var userIndices = new Dictionary<ulong, int>();
 
-		foreach (var user in db.GetAllUsers()) {
+		await foreach (var user in db.Users.Get()) {
 			var id = user.Id;
 			if (!userIds.Contains(id)) {
 				continue;
@@ -73,7 +73,7 @@ public static class ViewerJsonExport {
 
 			var idSnowflake = new Snowflake(id);
 			userIndices[id] = users.Count;
-			userindex.Add(idSnowflake);
+			userIndex.Add(idSnowflake);
 			
 			users[idSnowflake] = new ViewerJson.JsonUser {
 				Name = user.Name,
@@ -82,14 +82,14 @@ public static class ViewerJsonExport {
 			};
 		}
 
-		return users;
+		return (users, userIndex, userIndices);
 	}
 
-	private static List<ViewerJson.JsonServer> GenerateServerList(IDatabaseFile db, HashSet<ulong> serverIds, out Dictionary<ulong, int> serverIndices) {
+	private static async Task<(List<ViewerJson.JsonServer> Servers, Dictionary<ulong, int> ServerIndices)> GenerateServerList(IDatabaseFile db, HashSet<ulong> serverIds) {
 		var servers = new List<ViewerJson.JsonServer>();
-		serverIndices = new Dictionary<ulong, int>();
+		var serverIndices = new Dictionary<ulong, int>();
 
-		foreach (var server in db.GetAllServers()) {
+		await foreach (var server in db.Servers.Get()) {
 			var id = server.Id;
 			if (!serverIds.Contains(id)) {
 				continue;
@@ -103,7 +103,7 @@ public static class ViewerJsonExport {
 			});
 		}
 
-		return servers;
+		return (servers, serverIndices);
 	}
 
 	private static Dictionary<Snowflake, ViewerJson.JsonChannel> GenerateChannelList(List<Channel> includedChannels, Dictionary<ulong, int> serverIndices) {

app/Server/Database/IDatabaseFile.cs

@@ -1,43 +1,19 @@
 using System;
-using System.Collections.Generic;
+using System.Threading.Tasks;
-using DHT.Server.Data;
+using DHT.Server.Database.Repositories;
-using DHT.Server.Data.Aggregations;
-using DHT.Server.Data.Filters;
-using DHT.Server.Download;
 
 namespace DHT.Server.Database;
 
 public interface IDatabaseFile : IDisposable {
 	string Path { get; }
 	DatabaseStatistics Statistics { get; }
-	DatabaseStatisticsSnapshot SnapshotStatistics();
+	Task<DatabaseStatisticsSnapshot> SnapshotStatistics();
 
-	void AddServer(Data.Server server);
+	IUserRepository Users { get; }
-	List<Data.Server> GetAllServers();
+	IServerRepository Servers { get; }
+	IChannelRepository Channels { get; }
+	IMessageRepository Messages { get; }
+	IDownloadRepository Downloads { get; }
 
-	void AddChannel(Channel channel);
+	Task Vacuum();
-	List<Channel> GetAllChannels();
-
-	void AddUsers(User[] users);
-	List<User> GetAllUsers();
-
-	void AddMessages(Message[] messages);
-	int CountMessages(MessageFilter? filter = null);
-	List<Message> GetMessages(MessageFilter? filter = null);
-	HashSet<ulong> GetMessageIds(MessageFilter? filter = null);
-	void RemoveMessages(MessageFilter filter, FilterRemovalMode mode);
-
-	int CountAttachments(AttachmentFilter? filter = null);
-
-	void AddDownload(Data.Download download);
-	List<Data.Download> GetDownloadsWithoutData();
-	Data.Download GetDownloadWithData(Data.Download download);
-	DownloadedAttachment? GetDownloadedAttachment(string url);
-
-	void EnqueueDownloadItems(AttachmentFilter? filter = null);
-	List<DownloadItem> PullEnqueuedDownloadItems(int count);
-	void RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode);
-	DownloadStatusStatistics GetDownloadStatusStatistics();
-
-	void Vacuum();
 }

app/Server/Database/Import/LegacyArchiveImport.cs

@@ -33,10 +33,8 @@ public static class LegacyArchiveImport {
 			var servers = ReadServerList(meta, fakeSnowflake);
 
 			var newServersOnly = new HashSet<Data.Server>(servers);
-			var oldServersById = db.GetAllServers().ToDictionary(static server => server.Id, static server => server);
+			var oldServersById = await db.Servers.Get().ToDictionaryAsync(static server => server.Id, static server => server);
-
+			var oldChannelsById = await db.Channels.Get().ToDictionaryAsync(static channel => channel.Id, static channel => channel);
-			var oldChannels = db.GetAllChannels();
-			var oldChannelsById = oldChannels.ToDictionary(static channel => channel.Id, static channel => channel);
 
 			foreach (var (channelId, serverIndex) in ReadChannelToServerIndexMapping(meta, servers)) {
 				if (oldChannelsById.TryGetValue(channelId, out var oldChannel) && oldServersById.TryGetValue(oldChannel.Server, out var oldServer) && newServersOnly.Remove(servers[serverIndex])) {
@@ -66,17 +64,17 @@ public static class LegacyArchiveImport {
 
 			perf.Step("Read channel list");
 
-			var oldMessageIds = db.GetMessageIds();
+			var oldMessageIds = await db.Messages.GetIds().ToHashSetAsync();
 			var newMessages = channels.SelectMany(channel => ReadMessages(data, channel, users, fakeSnowflake))
 			                          .Where(message => !oldMessageIds.Contains(message.Id))
 			                          .ToArray();
 
 			perf.Step("Read messages");
 
-			db.AddUsers(users);
+			await db.Users.Add(users);
-			db.AddServers(servers);
+			await db.Servers.Add(servers);
-			db.AddChannels(channels);
+			await db.Channels.Add(channels);
-			db.AddMessages(newMessages);
+			await db.Messages.Add(newMessages);
 
 			perf.Step("Import into database");
 		} catch (HttpException e) {
@@ -179,9 +177,9 @@ public static class LegacyArchiveImport {
 				Timestamp = messageObj.RequireLong("t", path),
 				EditTimestamp = messageObj.HasKey("te") ? messageObj.RequireLong("te", path) : null,
 				RepliedToId = messageObj.HasKey("r") ? messageObj.RequireSnowflake("r", path) : null,
-				Attachments = messageObj.HasKey("a") ? ReadMessageAttachments(messageObj.RequireArray("a", path), fakeSnowflake, path + ".a[]").ToImmutableArray() : ImmutableArray<Attachment>.Empty,
+				Attachments = messageObj.HasKey("a") ? ReadMessageAttachments(messageObj.RequireArray("a", path), fakeSnowflake, path + ".a[]").ToImmutableList() : ImmutableList<Attachment>.Empty,
-				Embeds = messageObj.HasKey("e") ? ReadMessageEmbeds(messageObj.RequireArray("e", path), path + ".e[]").ToImmutableArray() : ImmutableArray<Embed>.Empty,
+				Embeds = messageObj.HasKey("e") ? ReadMessageEmbeds(messageObj.RequireArray("e", path), path + ".e[]").ToImmutableList() : ImmutableList<Embed>.Empty,
-				Reactions = messageObj.HasKey("re") ? ReadMessageReactions(messageObj.RequireArray("re", path), path + ".re[]").ToImmutableArray() : ImmutableArray<Reaction>.Empty,
+				Reactions = messageObj.HasKey("re") ? ReadMessageReactions(messageObj.RequireArray("re", path), path + ".re[]").ToImmutableList() : ImmutableList<Reaction>.Empty,
 			};
 		}).ToArray();
 	}

app/Server/Database/Repositories/IChannelRepository.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+
+namespace DHT.Server.Database.Repositories;
+
+public interface IChannelRepository {
+	Task Add(IReadOnlyList<Channel> channels);
+	
+	IAsyncEnumerable<Channel> Get();
+
+	internal sealed class Dummy : IChannelRepository {
+		public Task Add(IReadOnlyList<Channel> channels) {
+			return Task.CompletedTask;
+		}
+
+		public IAsyncEnumerable<Channel> Get() {
+			return AsyncEnumerable.Empty<Channel>();
+		}
+	}
+}

app/Server/Database/Repositories/IDownloadRepository.cs

@@ -0,0 +1,68 @@
+using System.Collections.Generic;
+using System.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;
+
+namespace DHT.Server.Database.Repositories;
+
+public interface IDownloadRepository {
+	Task<long> CountAttachments(AttachmentFilter? filter = null, CancellationToken cancellationToken = default);
+
+	Task AddDownload(Data.Download download);
+
+	Task<DownloadStatusStatistics> GetStatistics(CancellationToken cancellationToken = default);
+	
+	IAsyncEnumerable<Data.Download> GetWithoutData();
+
+	Task<Data.Download> HydrateWithData(Data.Download download);
+
+	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);
+
+	internal sealed class Dummy : IDownloadRepository {
+		public Task<long> CountAttachments(AttachmentFilter? filter, CancellationToken cancellationToken) {
+			return Task.FromResult(0L);
+		}
+
+		public Task AddDownload(Data.Download download) {
+			return Task.CompletedTask;
+		}
+
+		public Task<DownloadStatusStatistics> GetStatistics(CancellationToken cancellationToken) {
+			return Task.FromResult(new DownloadStatusStatistics());
+		}
+
+		public IAsyncEnumerable<Data.Download> GetWithoutData() {
+			return AsyncEnumerable.Empty<Data.Download>();
+		}
+
+		public Task<Data.Download> HydrateWithData(Data.Download download) {
+			return Task.FromResult(download);
+		}
+
+		public Task<DownloadedAttachment?> GetDownloadedAttachment(string normalizedUrl) {
+			return Task.FromResult<DownloadedAttachment?>(null);
+		}
+
+		public Task<int> EnqueueDownloadItems(AttachmentFilter? filter, CancellationToken cancellationToken) {
+			return Task.FromResult(0);
+		}
+
+		public IAsyncEnumerable<DownloadItem> PullEnqueuedDownloadItems(int count, CancellationToken cancellationToken) {
+			return AsyncEnumerable.Empty<DownloadItem>();
+		}
+
+		public Task RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {
+			return Task.CompletedTask;
+		}
+	}
+}

app/Server/Database/Repositories/IMessageRepository.cs

@@ -0,0 +1,42 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Data.Filters;
+
+namespace DHT.Server.Database.Repositories;
+
+public interface IMessageRepository {
+	Task Add(IReadOnlyList<Message> messages);
+	
+	Task<long> Count(MessageFilter? filter = null, CancellationToken cancellationToken = default);
+	
+	IAsyncEnumerable<Message> Get(MessageFilter? filter = null);
+	
+	IAsyncEnumerable<ulong> GetIds(MessageFilter? filter = null);
+	
+	Task Remove(MessageFilter filter, FilterRemovalMode mode);
+
+	internal sealed class Dummy : IMessageRepository {
+		public Task Add(IReadOnlyList<Message> messages) {
+			return Task.CompletedTask;
+		}
+
+		public Task<long> Count(MessageFilter? filter, CancellationToken cancellationToken) {
+			return Task.FromResult(0L);
+		}
+
+		public IAsyncEnumerable<Message> Get(MessageFilter? filter) {
+			return AsyncEnumerable.Empty<Message>();
+		}
+
+		public IAsyncEnumerable<ulong> GetIds(MessageFilter? filter) {
+			return AsyncEnumerable.Empty<ulong>();
+		}
+
+		public Task Remove(MessageFilter filter, FilterRemovalMode mode) {
+			return Task.CompletedTask;
+		}
+	}
+}

app/Server/Database/Repositories/IServerRepository.cs

@@ -0,0 +1,21 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace DHT.Server.Database.Repositories;
+
+public interface IServerRepository {
+	Task Add(IReadOnlyList<Data.Server> servers);
+	
+	IAsyncEnumerable<Data.Server> Get();
+
+	internal sealed class Dummy : IServerRepository {
+		public Task Add(IReadOnlyList<Data.Server> servers) {
+			return Task.CompletedTask;
+		}
+
+		public IAsyncEnumerable<Data.Server> Get() {
+			return AsyncEnumerable.Empty<Data.Server>();
+		}
+	}
+}

app/Server/Database/Repositories/IUserRepository.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+
+namespace DHT.Server.Database.Repositories;
+
+public interface IUserRepository {
+	Task Add(IReadOnlyList<User> users);
+	
+	IAsyncEnumerable<User> Get();
+
+	internal sealed class Dummy : IUserRepository {
+		public Task Add(IReadOnlyList<User> users) {
+			return Task.CompletedTask;
+		}
+
+		public IAsyncEnumerable<User> Get() {
+			return AsyncEnumerable.Empty<User>();
+		}
+	}
+}

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

@@ -0,0 +1,77 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Database.Repositories;
+using DHT.Server.Database.Sqlite.Utils;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Repositories;
+
+sealed class SqliteChannelRepository : IChannelRepository {
+	private readonly SqliteConnectionPool pool;
+	private readonly DatabaseStatistics statistics;
+
+	public SqliteChannelRepository(SqliteConnectionPool pool, DatabaseStatistics statistics) {
+		this.pool = pool;
+		this.statistics = statistics;
+	}
+
+	internal async Task Initialize() {
+		using var conn = pool.Take();
+		await UpdateChannelStatistics(conn);
+	}
+
+	private async Task UpdateChannelStatistics(ISqliteConnection conn) {
+		statistics.TotalChannels = await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM channels", static reader => reader?.GetInt64(0) ?? 0L);
+	}
+
+	public async Task Add(IReadOnlyList<Channel> channels) {
+		using var conn = pool.Take();
+
+		await using (var tx = await conn.BeginTransactionAsync()) {
+			await using var cmd = conn.Upsert("channels", [
+				("id", SqliteType.Integer),
+				("server", SqliteType.Integer),
+				("name", SqliteType.Text),
+				("parent_id", SqliteType.Integer),
+				("position", SqliteType.Integer),
+				("topic", SqliteType.Text),
+				("nsfw", SqliteType.Integer)
+			]);
+
+			foreach (var channel in channels) {
+				cmd.Set(":id", channel.Id);
+				cmd.Set(":server", channel.Server);
+				cmd.Set(":name", channel.Name);
+				cmd.Set(":parent_id", channel.ParentId);
+				cmd.Set(":position", channel.Position);
+				cmd.Set(":topic", channel.Topic);
+				cmd.Set(":nsfw", channel.Nsfw);
+				await cmd.ExecuteNonQueryAsync();
+			}
+
+			await tx.CommitAsync();
+		}
+
+		await UpdateChannelStatistics(conn);
+	}
+
+	public async IAsyncEnumerable<Channel> Get() {
+		using var conn = pool.Take();
+
+		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()) {
+			yield return new Channel {
+				Id = reader.GetUint64(0),
+				Server = reader.GetUint64(1),
+				Name = reader.GetString(2),
+				ParentId = reader.IsDBNull(3) ? null : reader.GetUint64(3),
+				Position = reader.IsDBNull(4) ? null : reader.GetInt32(4),
+				Topic = reader.IsDBNull(5) ? null : reader.GetString(5),
+				Nsfw = reader.IsDBNull(6) ? null : reader.GetBoolean(6),
+			};
+		}
+	}
+}

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

@@ -0,0 +1,233 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Data.Aggregations;
+using DHT.Server.Data.Filters;
+using DHT.Server.Database.Repositories;
+using DHT.Server.Database.Sqlite.Utils;
+using DHT.Server.Download;
+using DHT.Utils.Tasks;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Repositories;
+
+sealed class SqliteDownloadRepository : IDownloadRepository {
+	private readonly SqliteConnectionPool pool;
+	private readonly AsyncValueComputer<long>.Single totalDownloadsComputer;
+
+	public SqliteDownloadRepository(SqliteConnectionPool pool, AsyncValueComputer<long>.Single totalDownloadsComputer) {
+		this.pool = pool;
+		this.totalDownloadsComputer = totalDownloadsComputer;
+	}
+
+	public async Task<long> CountAttachments(AttachmentFilter? filter, CancellationToken cancellationToken) {
+		using var conn = pool.Take();
+		return await conn.ExecuteReaderAsync("SELECT COUNT(DISTINCT normalized_url) FROM attachments a" + filter.GenerateWhereClause("a"), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
+	}
+
+	public async Task AddDownload(Data.Download download) {
+		using (var conn = pool.Take()) {
+			await using var cmd = conn.Upsert("downloads", [
+				("normalized_url", SqliteType.Text),
+				("download_url", SqliteType.Text),
+				("status", SqliteType.Integer),
+				("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();
+		}
+
+		totalDownloadsComputer.Recompute();
+	}
+
+	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();
+
+		using var conn = pool.Take();
+		await LoadUndownloadedStatistics(conn, result, cancellationToken);
+		await LoadSuccessStatistics(conn, result, cancellationToken);
+		return result;
+	}
+
+	public async IAsyncEnumerable<Data.Download> GetWithoutData() {
+		using var conn = pool.Take();
+
+		await using var cmd = conn.Command("SELECT normalized_url, download_url, status, size FROM downloads");
+		await using var reader = await cmd.ExecuteReaderAsync();
+
+		while (reader.Read()) {
+			string normalizedUrl = reader.GetString(0);
+			string downloadUrl = reader.GetString(1);
+			var status = (DownloadStatus) reader.GetInt32(2);
+			ulong size = reader.GetUint64(3);
+
+			yield return new Data.Download(normalizedUrl, downloadUrl, status, size);
+		}
+	}
+
+	public async Task<Data.Download> HydrateWithData(Data.Download download) {
+		using var conn = 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 reader = await cmd.ExecuteReaderAsync();
+
+		if (reader.Read() && !reader.IsDBNull(0)) {
+			return download.WithData((byte[]) reader["blob"]);
+		}
+		else {
+			return download;
+		}
+	}
+
+	public async Task<DownloadedAttachment?> GetDownloadedAttachment(string normalizedUrl) {
+		using var conn = 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
+			"""
+		);
+
+		cmd.AddAndSet(":normalized_url", SqliteType.Text, normalizedUrl);
+		cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
+
+		await using var reader = await cmd.ExecuteReaderAsync();
+
+		if (!reader.Read()) {
+			return null;
+		}
+
+		return new DownloadedAttachment {
+			Type = reader.IsDBNull(0) ? null : reader.GetString(0),
+			Data = (byte[]) reader["blob"],
+		};
+	}
+
+	public async Task<int> EnqueueDownloadItems(AttachmentFilter? filter, CancellationToken cancellationToken) {
+		using var conn = pool.Take();
+
+		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>();
+
+		using var conn = 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);
+			cmd.AddAndSet(":limit", SqliteType.Integer, Math.Max(0, count));
+
+			await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
+
+			while (reader.Read()) {
+				found.Add(new DownloadItem {
+					NormalizedUrl = reader.GetString(0),
+					DownloadUrl = reader.GetString(1),
+					Size = reader.GetUint64(2),
+				});
+			}
+		}
+
+		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);
+			cmd.AddAndSet(":downloading", SqliteType.Integer, (int) DownloadStatus.Downloading);
+			cmd.Add(":normalized_url", SqliteType.Text);
+
+			foreach (var item in found) {
+				cmd.Set(":normalized_url", item.NormalizedUrl);
+
+				if (await cmd.ExecuteNonQueryAsync(cancellationToken) == 1) {
+					yield return item;
+				}
+			}
+		}
+	}
+
+	public async Task RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {
+		using (var conn = pool.Take()) {
+			await conn.ExecuteAsync(
+				$"""
+				 -- noinspection SqlWithoutWhere
+				 DELETE FROM downloads
+				 {filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching)}
+				 """
+			);
+		}
+
+		totalDownloadsComputer.Recompute();
+	}
+}

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

@@ -0,0 +1,306 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Threading;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Data.Filters;
+using DHT.Server.Database.Repositories;
+using DHT.Server.Database.Sqlite.Utils;
+using DHT.Utils.Tasks;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Repositories;
+
+sealed class SqliteMessageRepository : IMessageRepository {
+	private readonly SqliteConnectionPool pool;
+	private readonly AsyncValueComputer<long>.Single totalMessagesComputer;
+	private readonly AsyncValueComputer<long>.Single totalAttachmentsComputer;
+
+	public SqliteMessageRepository(SqliteConnectionPool pool, AsyncValueComputer<long>.Single totalMessagesComputer, AsyncValueComputer<long>.Single totalAttachmentsComputer) {
+		this.pool = pool;
+		this.totalMessagesComputer = totalMessagesComputer;
+		this.totalAttachmentsComputer = totalAttachmentsComputer;
+	}
+
+	public async Task Add(IReadOnlyList<Message> messages) {
+		if (messages.Count == 0) {
+			return;
+		}
+
+		static SqliteCommand DeleteByMessageId(ISqliteConnection conn, string tableName) {
+			return conn.Delete(tableName, ("message_id", SqliteType.Integer));
+		}
+
+		static async Task ExecuteDeleteByMessageId(SqliteCommand cmd, object id) {
+			cmd.Set(":message_id", id);
+			await cmd.ExecuteNonQueryAsync();
+		}
+
+		bool addedAttachments = false;
+
+		using (var conn = pool.Take()) {
+			await using var tx = await conn.BeginTransactionAsync();
+
+			await using var messageCmd = conn.Upsert("messages", [
+				("message_id", SqliteType.Integer),
+				("sender_id", SqliteType.Integer),
+				("channel_id", SqliteType.Integer),
+				("text", SqliteType.Text),
+				("timestamp", SqliteType.Integer)
+			]);
+
+			await using var deleteEditTimestampCmd = DeleteByMessageId(conn, "edit_timestamps");
+			await using var deleteRepliedToCmd = DeleteByMessageId(conn, "replied_to");
+
+			await using var deleteAttachmentsCmd = DeleteByMessageId(conn, "attachments");
+			await using var deleteEmbedsCmd = DeleteByMessageId(conn, "embeds");
+			await using var deleteReactionsCmd = DeleteByMessageId(conn, "reactions");
+
+			await using var editTimestampCmd = conn.Insert("edit_timestamps", [
+				("message_id", SqliteType.Integer),
+				("edit_timestamp", SqliteType.Integer)
+			]);
+
+			await using var repliedToCmd = conn.Insert("replied_to", [
+				("message_id", SqliteType.Integer),
+				("replied_to_id", SqliteType.Integer)
+			]);
+
+			await using var attachmentCmd = conn.Insert("attachments", [
+				("message_id", SqliteType.Integer),
+				("attachment_id", SqliteType.Integer),
+				("name", SqliteType.Text),
+				("type", SqliteType.Text),
+				("normalized_url", SqliteType.Text),
+				("download_url", SqliteType.Text),
+				("size", SqliteType.Integer),
+				("width", SqliteType.Integer),
+				("height", SqliteType.Integer)
+			]);
+
+			await using var embedCmd = conn.Insert("embeds", [
+				("message_id", SqliteType.Integer),
+				("json", SqliteType.Text)
+			]);
+
+			await using var reactionCmd = conn.Insert("reactions", [
+				("message_id", SqliteType.Integer),
+				("emoji_id", SqliteType.Integer),
+				("emoji_name", SqliteType.Text),
+				("emoji_flags", SqliteType.Integer),
+				("count", SqliteType.Integer)
+			]);
+
+			foreach (var message in messages) {
+				object messageId = message.Id;
+
+				messageCmd.Set(":message_id", messageId);
+				messageCmd.Set(":sender_id", message.Sender);
+				messageCmd.Set(":channel_id", message.Channel);
+				messageCmd.Set(":text", message.Text);
+				messageCmd.Set(":timestamp", message.Timestamp);
+				await messageCmd.ExecuteNonQueryAsync();
+
+				await ExecuteDeleteByMessageId(deleteEditTimestampCmd, messageId);
+				await ExecuteDeleteByMessageId(deleteRepliedToCmd, messageId);
+
+				await ExecuteDeleteByMessageId(deleteAttachmentsCmd, messageId);
+				await ExecuteDeleteByMessageId(deleteEmbedsCmd, messageId);
+				await ExecuteDeleteByMessageId(deleteReactionsCmd, messageId);
+
+				if (message.EditTimestamp is {} timestamp) {
+					editTimestampCmd.Set(":message_id", messageId);
+					editTimestampCmd.Set(":edit_timestamp", timestamp);
+					await editTimestampCmd.ExecuteNonQueryAsync();
+				}
+
+				if (message.RepliedToId is {} repliedToId) {
+					repliedToCmd.Set(":message_id", messageId);
+					repliedToCmd.Set(":replied_to_id", repliedToId);
+					await repliedToCmd.ExecuteNonQueryAsync();
+				}
+
+				if (!message.Attachments.IsEmpty) {
+					addedAttachments = true;
+
+					foreach (var attachment in message.Attachments) {
+						attachmentCmd.Set(":message_id", messageId);
+						attachmentCmd.Set(":attachment_id", attachment.Id);
+						attachmentCmd.Set(":name", attachment.Name);
+						attachmentCmd.Set(":type", attachment.Type);
+						attachmentCmd.Set(":normalized_url", attachment.NormalizedUrl);
+						attachmentCmd.Set(":download_url", attachment.DownloadUrl);
+						attachmentCmd.Set(":size", attachment.Size);
+						attachmentCmd.Set(":width", attachment.Width);
+						attachmentCmd.Set(":height", attachment.Height);
+						await attachmentCmd.ExecuteNonQueryAsync();
+					}
+				}
+
+				if (!message.Embeds.IsEmpty) {
+					foreach (var embed in message.Embeds) {
+						embedCmd.Set(":message_id", messageId);
+						embedCmd.Set(":json", embed.Json);
+						await embedCmd.ExecuteNonQueryAsync();
+					}
+				}
+
+				if (!message.Reactions.IsEmpty) {
+					foreach (var reaction in message.Reactions) {
+						reactionCmd.Set(":message_id", messageId);
+						reactionCmd.Set(":emoji_id", reaction.EmojiId);
+						reactionCmd.Set(":emoji_name", reaction.EmojiName);
+						reactionCmd.Set(":emoji_flags", (int) reaction.EmojiFlags);
+						reactionCmd.Set(":count", reaction.Count);
+						await reactionCmd.ExecuteNonQueryAsync();
+					}
+				}
+			}
+
+			await tx.CommitAsync();
+		}
+
+		totalMessagesComputer.Recompute();
+
+		if (addedAttachments) {
+			totalAttachmentsComputer.Recompute();
+		}
+	}
+
+	public async Task<long> Count(MessageFilter? filter, CancellationToken cancellationToken) {
+		using var conn = pool.Take();
+		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM messages" + filter.GenerateWhereClause(), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
+	}
+
+	private sealed class MesageToManyCommand<T> : IAsyncDisposable {
+		private readonly SqliteCommand cmd;
+		private readonly Func<SqliteDataReader, T> readItem;
+
+		public MesageToManyCommand(ISqliteConnection conn, string sql, Func<SqliteDataReader, T> readItem) {
+			this.cmd = conn.Command(sql);
+			this.cmd.Add(":message_id", SqliteType.Integer);
+
+			this.readItem = readItem;
+		}
+
+		public async Task<ImmutableList<T>> GetItems(ulong messageId) {
+			cmd.Set(":message_id", messageId);
+
+			var items = ImmutableList<T>.Empty;
+
+			await using var reader = await cmd.ExecuteReaderAsync();
+
+			while (await reader.ReadAsync()) {
+				items = items.Add(readItem(reader));
+			}
+
+			return items;
+		}
+
+		public async ValueTask DisposeAsync() {
+			await cmd.DisposeAsync();
+		}
+	}
+
+	public async IAsyncEnumerable<Message> Get(MessageFilter? filter) {
+		using var conn = pool.Take();
+
+		const string AttachmentSql =
+			"""
+			SELECT attachment_id, name, type, normalized_url, download_url, size, width, height
+			FROM attachments
+			WHERE message_id = :message_id
+			""";
+
+		await using var attachmentCmd = new MesageToManyCommand<Attachment>(conn, AttachmentSql, static reader => new Attachment {
+			Id = reader.GetUint64(0),
+			Name = reader.GetString(1),
+			Type = reader.IsDBNull(2) ? null : reader.GetString(2),
+			NormalizedUrl = reader.GetString(3),
+			DownloadUrl = reader.GetString(4),
+			Size = reader.GetUint64(5),
+			Width = reader.IsDBNull(6) ? null : reader.GetInt32(6),
+			Height = reader.IsDBNull(7) ? null : reader.GetInt32(7),
+		});
+
+		const string EmbedSql =
+			"""
+			SELECT json
+			FROM embeds
+			WHERE message_id = :message_id
+			""";
+
+		await using var embedCmd = new MesageToManyCommand<Embed>(conn, EmbedSql, static reader => new Embed {
+			Json = reader.GetString(0)
+		});
+
+		const string ReactionSql =
+			"""
+			SELECT emoji_id, emoji_name, emoji_flags, count
+			FROM reactions
+			WHERE message_id = :message_id
+			""";
+
+		await using var reactionsCmd = new MesageToManyCommand<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),
+			Count = reader.GetInt32(3),
+		});
+
+		await using var messageCmd = conn.Command(
+			$"""
+			 SELECT m.message_id, m.sender_id, m.channel_id, m.text, m.timestamp, et.edit_timestamp, rt.replied_to_id
+			 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")}
+			 """
+		);
+
+		await using var reader = await messageCmd.ExecuteReaderAsync();
+
+		while (await reader.ReadAsync()) {
+			ulong messageId = reader.GetUint64(0);
+
+			yield return new Message {
+				Id = messageId,
+				Sender = reader.GetUint64(1),
+				Channel = reader.GetUint64(2),
+				Text = reader.GetString(3),
+				Timestamp = reader.GetInt64(4),
+				EditTimestamp = reader.IsDBNull(5) ? null : reader.GetInt64(5),
+				RepliedToId = reader.IsDBNull(6) ? null : reader.GetUint64(6),
+				Attachments = await attachmentCmd.GetItems(messageId),
+				Embeds = await embedCmd.GetItems(messageId),
+				Reactions = await reactionsCmd.GetItems(messageId)
+			};
+		}
+	}
+
+	public async IAsyncEnumerable<ulong> GetIds(MessageFilter? filter) {
+		using var conn = pool.Take();
+		
+		await using var cmd = conn.Command("SELECT message_id FROM messages" + filter.GenerateWhereClause());
+		await using var reader = await cmd.ExecuteReaderAsync();
+
+		while (await reader.ReadAsync()) {
+			yield return reader.GetUint64(0);
+		}
+	}
+
+	public async Task Remove(MessageFilter filter, FilterRemovalMode mode) {
+		using (var conn = pool.Take()) {
+			await conn.ExecuteAsync(
+				$"""
+				 -- noinspection SqlWithoutWhere
+				 DELETE FROM messages
+				 {filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching)}
+				 """
+			);
+		}
+
+		totalMessagesComputer.Recompute();
+	}
+}

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

@@ -0,0 +1,65 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Database.Repositories;
+using DHT.Server.Database.Sqlite.Utils;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Repositories;
+
+sealed class SqliteServerRepository : IServerRepository {
+	private readonly SqliteConnectionPool pool;
+	private readonly DatabaseStatistics statistics;
+
+	public SqliteServerRepository(SqliteConnectionPool pool, DatabaseStatistics statistics) {
+		this.pool = pool;
+		this.statistics = statistics;
+	}
+
+	internal async Task Initialize() {
+		using var conn = pool.Take();
+		await UpdateServerStatistics(conn);
+	}
+
+	private async Task UpdateServerStatistics(ISqliteConnection conn) {
+		statistics.TotalServers = await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM servers", static reader => reader?.GetInt64(0) ?? 0L);
+	}
+
+	public async Task Add(IReadOnlyList<Data.Server> servers) {
+		using var conn = pool.Take();
+
+		await using (var tx = await conn.BeginTransactionAsync()) {
+			await using var cmd = conn.Upsert("servers", [
+				("id", SqliteType.Integer),
+				("name", SqliteType.Text),
+				("type", SqliteType.Text)
+			]);
+
+			foreach (var server in servers) {
+				cmd.Set(":id", server.Id);
+				cmd.Set(":name", server.Name);
+				cmd.Set(":type", ServerTypes.ToString(server.Type));
+				await cmd.ExecuteNonQueryAsync();
+			}
+
+			await tx.CommitAsync();
+		}
+
+		await UpdateServerStatistics(conn);
+	}
+
+	public async IAsyncEnumerable<Data.Server> Get() {
+		using var conn = pool.Take();
+
+		await using var cmd = conn.Command("SELECT id, name, type FROM servers");
+		await using var reader = await cmd.ExecuteReaderAsync();
+
+		while (reader.Read()) {
+			yield return new Data.Server {
+				Id = reader.GetUint64(0),
+				Name = reader.GetString(1),
+				Type = ServerTypes.FromString(reader.GetString(2)),
+			};
+		}
+	}
+}

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

@@ -0,0 +1,68 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Database.Repositories;
+using DHT.Server.Database.Sqlite.Utils;
+using Microsoft.Data.Sqlite;
+
+namespace DHT.Server.Database.Sqlite.Repositories;
+
+sealed class SqliteUserRepository : IUserRepository {
+	private readonly SqliteConnectionPool pool;
+	private readonly DatabaseStatistics statistics;
+	
+	public SqliteUserRepository(SqliteConnectionPool pool, DatabaseStatistics statistics) {
+		this.pool = pool;
+		this.statistics = statistics;
+	}
+
+	internal async Task Initialize() {
+		using var conn = pool.Take();
+		await UpdateUserStatistics(conn);
+	}
+	
+	private async Task UpdateUserStatistics(ISqliteConnection conn) {
+		statistics.TotalUsers = await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM users", static reader => reader?.GetInt64(0) ?? 0L);
+	}
+
+	public async Task Add(IReadOnlyList<User> users) {
+		using var conn = pool.Take();
+
+		await using (var tx = await conn.BeginTransactionAsync()) {
+			await using var cmd = conn.Upsert("users", [
+				("id", SqliteType.Integer),
+				("name", SqliteType.Text),
+				("avatar_url", SqliteType.Text),
+				("discriminator", SqliteType.Text)
+			]);
+
+			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();
+			}
+
+			await tx.CommitAsync();
+		}
+		
+		await UpdateUserStatistics(conn);
+	}
+
+	public async IAsyncEnumerable<User> Get() {
+		using var conn = 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()) {
+			yield return new User {
+				Id = reader.GetUint64(0),
+				Name = reader.GetString(1),
+				AvatarUrl = reader.IsDBNull(2) ? null : reader.GetString(2),
+				Discriminator = reader.IsDBNull(3) ? null : reader.GetString(3),
+			};
+		}
+	}
+}

app/Server/Database/Sqlite/Schema.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Data.Common;
 using System.Threading.Tasks;
 using DHT.Server.Database.Exceptions;
 using DHT.Server.Database.Sqlite.Utils;
@@ -20,14 +21,14 @@ sealed class Schema {
 	}
 
 	public async Task<bool> Setup(ISchemaUpgradeCallbacks callbacks) {
-		conn.Execute(@"CREATE TABLE IF NOT EXISTS metadata (key TEXT PRIMARY KEY, value TEXT)");
+		await conn.ExecuteAsync("CREATE TABLE IF NOT EXISTS metadata (key TEXT PRIMARY KEY, value TEXT)");
 
-		var dbVersionStr = conn.SelectScalar("SELECT value FROM metadata WHERE key = 'version'");
+		var dbVersionStr = await conn.ExecuteReaderAsync("SELECT value FROM metadata WHERE key = 'version'", static reader => reader?.GetString(0));
 		if (dbVersionStr == null) {
-			InitializeSchemas();
+			await InitializeSchemas();
 		}
-		else if (!int.TryParse(dbVersionStr.ToString(), out int dbVersion) || dbVersion < 1) {
+		else if (!int.TryParse(dbVersionStr, out int dbVersion) || dbVersion < 1) {
-			throw new InvalidDatabaseVersionException(dbVersionStr.ToString() ?? "<null>");
+			throw new InvalidDatabaseVersionException(dbVersionStr);
 		}
 		else if (dbVersion > Version) {
 			throw new DatabaseTooNewException(dbVersion);
@@ -44,8 +45,8 @@ sealed class Schema {
 		return true;
 	}
 
-	private void InitializeSchemas() {
+	private async Task InitializeSchemas() {
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE users (
 		                        	id            INTEGER PRIMARY KEY NOT NULL,
 		                        	name          TEXT NOT NULL,
@@ -54,7 +55,7 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE servers (
 		                        	id   INTEGER PRIMARY KEY NOT NULL,
 		                        	name TEXT NOT NULL,
@@ -62,7 +63,7 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE channels (
 		                        	id        INTEGER PRIMARY KEY NOT NULL,
 		                        	server    INTEGER NOT NULL,
@@ -74,7 +75,7 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE messages (
 		                        	message_id INTEGER PRIMARY KEY NOT NULL,
 		                        	sender_id  INTEGER NOT NULL,
@@ -84,7 +85,7 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE attachments (
 		                        	message_id     INTEGER NOT NULL,
 		                        	attachment_id  INTEGER NOT NULL PRIMARY KEY NOT NULL,
@@ -98,14 +99,14 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE embeds (
 		                        	message_id INTEGER NOT NULL,
 		                        	json       TEXT NOT NULL
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE downloads (
 		                        	normalized_url TEXT NOT NULL PRIMARY KEY,
 		                        	download_url   TEXT,
@@ -115,7 +116,7 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE reactions (
 		                        	message_id  INTEGER NOT NULL,
 		                        	emoji_id    INTEGER,
@@ -125,18 +126,18 @@ sealed class Schema {
 		                        )
 		                        """);
 
-		CreateMessageEditTimestampTable();
+		await CreateMessageEditTimestampTable();
-		CreateMessageRepliedToTable();
+		await CreateMessageRepliedToTable();
 
-		conn.Execute("CREATE INDEX attachments_message_ix ON attachments(message_id)");
+		await conn.ExecuteAsync("CREATE INDEX attachments_message_ix ON attachments(message_id)");
-		conn.Execute("CREATE INDEX embeds_message_ix ON embeds(message_id)");
+		await conn.ExecuteAsync("CREATE INDEX embeds_message_ix ON embeds(message_id)");
-		conn.Execute("CREATE INDEX reactions_message_ix ON reactions(message_id)");
+		await conn.ExecuteAsync("CREATE INDEX reactions_message_ix ON reactions(message_id)");
 
-		conn.Execute("INSERT INTO metadata (key, value) VALUES ('version', " + Version + ")");
+		await conn.ExecuteAsync("INSERT INTO metadata (key, value) VALUES ('version', " + Version + ")");
 	}
 
-	private void CreateMessageEditTimestampTable() {
+	private async Task CreateMessageEditTimestampTable() {
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE edit_timestamps (
 		                        	message_id     INTEGER PRIMARY KEY NOT NULL,
 		                        	edit_timestamp INTEGER NOT NULL
@@ -144,8 +145,8 @@ sealed class Schema {
 		                        """);
 	}
 
-	private void CreateMessageRepliedToTable() {
+	private async Task CreateMessageRepliedToTable() {
-		conn.Execute("""
+		await conn.ExecuteAsync("""
 		                        CREATE TABLE replied_to (
 		                        	message_id    INTEGER PRIMARY KEY NOT NULL,
 		                        	replied_to_id INTEGER NOT NULL
@@ -168,7 +169,7 @@ sealed class Schema {
 			}
 		}
 
-		await using var tx = conn.BeginTransaction();
+		await using var tx = await conn.BeginTransactionAsync();
 
 		int totalUrls = normalizedUrls.Count;
 		int processedUrls = -1;
@@ -212,11 +213,11 @@ sealed class Schema {
 			}
 		}
 
-		conn.Execute("PRAGMA cache_size = -20000");
+		await conn.ExecuteAsync("PRAGMA cache_size = -20000");
 
-		SqliteTransaction tx;
+		DbTransaction tx;
 
-		await using (tx = conn.BeginTransaction()) {
+		await using (tx = await conn.BeginTransactionAsync()) {
 			await reporter.SubWork("Deleting duplicates...", 0, 0);
 
 			await using (var deleteCmd = conn.Delete("downloads", ("url", SqliteType.Text))) {
@@ -232,7 +233,7 @@ sealed class Schema {
 		int totalUrls = normalizedUrlsToOriginalUrls.Count;
 		int processedUrls = -1;
 
-		tx = conn.BeginTransaction();
+		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);
@@ -247,8 +248,8 @@ sealed class Schema {
 					await tx.CommitAsync();
 					await tx.DisposeAsync();
 
-					tx = conn.BeginTransaction();
+					tx = await conn.BeginTransactionAsync();
-					updateCmd.Transaction = tx;
+					updateCmd.Transaction = (SqliteTransaction) tx;
 				}
 
 				updateCmd.Set(":normalized_url", normalizedUrl);
@@ -262,17 +263,17 @@ sealed class Schema {
 		await tx.CommitAsync();
 		await tx.DisposeAsync();
 
-		conn.Execute("PRAGMA cache_size = -2000");
+		await conn.ExecuteAsync("PRAGMA cache_size = -2000");
 	}
 
 	private async Task UpgradeSchemas(int dbVersion, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
 		var perf = Log.Start("from version " + dbVersion);
 
-		conn.Execute("UPDATE metadata SET value = " + Version + " WHERE key = 'version'");
+		await conn.ExecuteAsync("UPDATE metadata SET value = " + Version + " WHERE key = 'version'");
 
 		if (dbVersion <= 1) {
 			await reporter.MainWork("Applying schema changes...", 0, 1);
-			conn.Execute("ALTER TABLE channels ADD parent_id INTEGER");
+			await conn.ExecuteAsync("ALTER TABLE channels ADD parent_id INTEGER");
 
 			perf.Step("Upgrade to version 2");
 			await reporter.NextVersion();
@@ -281,37 +282,37 @@ sealed class Schema {
 		if (dbVersion <= 2) {
 			await reporter.MainWork("Applying schema changes...", 0, 1);
 
-			CreateMessageEditTimestampTable();
+			await CreateMessageEditTimestampTable();
-			CreateMessageRepliedToTable();
+			await CreateMessageRepliedToTable();
 
-			conn.Execute("""
+			await conn.ExecuteAsync("""
 			                        INSERT INTO edit_timestamps (message_id, edit_timestamp)
 			                        SELECT message_id, edit_timestamp
 			                        FROM messages
 			                        WHERE edit_timestamp IS NOT NULL
 			                        """);
 
-			conn.Execute("""
+			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
 			                        """);
 
-			conn.Execute("ALTER TABLE messages DROP COLUMN replied_to_id");
+			await conn.ExecuteAsync("ALTER TABLE messages DROP COLUMN replied_to_id");
-			conn.Execute("ALTER TABLE messages DROP COLUMN edit_timestamp");
+			await conn.ExecuteAsync("ALTER TABLE messages DROP COLUMN edit_timestamp");
 
 			perf.Step("Upgrade to version 3");
 
 			await reporter.MainWork("Vacuuming the database...", 1, 1);
-			conn.Execute("VACUUM");
+			await conn.ExecuteAsync("VACUUM");
 			perf.Step("Vacuum");
 
 			await reporter.NextVersion();
 		}
 
 		if (dbVersion <= 3) {
-			conn.Execute("""
+			await conn.ExecuteAsync("""
 			                        CREATE TABLE downloads (
 			                        	url    TEXT NOT NULL PRIMARY KEY,
 			                        	status INTEGER NOT NULL,
@@ -326,8 +327,8 @@ sealed class Schema {
 
 		if (dbVersion <= 4) {
 			await reporter.MainWork("Applying schema changes...", 0, 1);
-			conn.Execute("ALTER TABLE attachments ADD width INTEGER");
+			await conn.ExecuteAsync("ALTER TABLE attachments ADD width INTEGER");
-			conn.Execute("ALTER TABLE attachments ADD height INTEGER");
+			await conn.ExecuteAsync("ALTER TABLE attachments ADD height INTEGER");
 
 			perf.Step("Upgrade to version 5");
 			await reporter.NextVersion();
@@ -335,8 +336,8 @@ sealed class Schema {
 
 		if (dbVersion <= 5) {
 			await reporter.MainWork("Applying schema changes...", 0, 3);
-			conn.Execute("ALTER TABLE attachments ADD download_url TEXT");
+			await conn.ExecuteAsync("ALTER TABLE attachments ADD download_url TEXT");
-			conn.Execute("ALTER TABLE downloads ADD download_url TEXT");
+			await conn.ExecuteAsync("ALTER TABLE downloads ADD download_url TEXT");
 
 			await reporter.MainWork("Updating attachments...", 1, 3);
 			await NormalizeAttachmentUrls(reporter);
@@ -345,8 +346,8 @@ sealed class Schema {
 			await NormalizeDownloadUrls(reporter);
 
 			await reporter.MainWork("Applying schema changes...", 3, 3);
-			conn.Execute("ALTER TABLE attachments RENAME COLUMN url TO normalized_url");
+			await conn.ExecuteAsync("ALTER TABLE attachments RENAME COLUMN url TO normalized_url");
-			conn.Execute("ALTER TABLE downloads 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();

app/Server/Database/Sqlite/SqliteDatabaseFile.cs

@@ -1,15 +1,8 @@
 using System;
-using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Text;
 using System.Threading.Tasks;
-using DHT.Server.Data;
+using DHT.Server.Database.Repositories;
-using DHT.Server.Data.Aggregations;
+using DHT.Server.Database.Sqlite.Repositories;
-using DHT.Server.Data.Filters;
 using DHT.Server.Database.Sqlite.Utils;
-using DHT.Server.Download;
-using DHT.Utils.Collections;
-using DHT.Utils.Logging;
 using DHT.Utils.Tasks;
 using Microsoft.Data.Sqlite;
 
@@ -36,7 +29,9 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 		}
 
 		if (wasOpened) {
-			return new SqliteDatabaseFile(path, pool, computeTaskResultScheduler);
+			var db = new SqliteDatabaseFile(path, pool, computeTaskResultScheduler);
+			await db.Initialize();
+			return db;
 		}
 		else {
 			pool.Dispose();
@@ -47,14 +42,25 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 	public string Path { get; }
 	public DatabaseStatistics Statistics { get; }
 	
-	private readonly Log log;
+	public IUserRepository Users => users;
+	public IServerRepository Servers => servers;
+	public IChannelRepository Channels => channels;
+	public IMessageRepository Messages => messages;
+	public IDownloadRepository Downloads => downloads;
+	
 	private readonly SqliteConnectionPool pool;
+	
+	private readonly SqliteUserRepository users;
+	private readonly SqliteServerRepository servers;
+	private readonly SqliteChannelRepository channels;
+	private readonly SqliteMessageRepository messages;
+	private readonly SqliteDownloadRepository downloads;
+	
 	private readonly AsyncValueComputer<long>.Single totalMessagesComputer;
 	private readonly AsyncValueComputer<long>.Single totalAttachmentsComputer;
 	private readonly AsyncValueComputer<long>.Single totalDownloadsComputer;
 
 	private SqliteDatabaseFile(string path, SqliteConnectionPool pool, TaskScheduler computeTaskResultScheduler) {
-		this.log = Log.ForType(typeof(SqliteDatabaseFile), System.IO.Path.GetFileName(path));
 		this.pool = pool;
 
 		this.totalMessagesComputer = AsyncValueComputer<long>.WithResultProcessor(UpdateMessageStatistics, computeTaskResultScheduler).WithOutdatedResults().BuildWithComputer(ComputeMessageStatistics);
@@ -64,669 +70,65 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 		this.Path = path;
 		this.Statistics = new DatabaseStatistics();
 
-		using (var conn = pool.Take()) {
+		this.users = new SqliteUserRepository(pool, Statistics);
-			UpdateServerStatistics(conn);
+		this.servers = new SqliteServerRepository(pool, Statistics);
-			UpdateChannelStatistics(conn);
+		this.channels = new SqliteChannelRepository(pool, Statistics);
-			UpdateUserStatistics(conn);
+		this.messages = new SqliteMessageRepository(pool, totalMessagesComputer, totalAttachmentsComputer);
-		}
+		this.downloads = new SqliteDownloadRepository(pool, totalDownloadsComputer);
 
 		totalMessagesComputer.Recompute();
 		totalAttachmentsComputer.Recompute();
 		totalDownloadsComputer.Recompute();
 	}
 
+	private async Task Initialize() {
+		await users.Initialize();
+		await servers.Initialize();
+		await channels.Initialize();
+	}
+
 	public void Dispose() {
+		totalMessagesComputer.Cancel();
+		totalAttachmentsComputer.Cancel();
+		totalDownloadsComputer.Cancel();
 		pool.Dispose();
 	}
 
-	public DatabaseStatisticsSnapshot SnapshotStatistics() {
+	public async Task<DatabaseStatisticsSnapshot> SnapshotStatistics() {
 		return new DatabaseStatisticsSnapshot {
 			TotalServers = Statistics.TotalServers,
 			TotalChannels = Statistics.TotalChannels,
 			TotalUsers = Statistics.TotalUsers,
-			TotalMessages = ComputeMessageStatistics(),
+			TotalMessages = await ComputeMessageStatistics(),
 		};
 	}
 
-	public void AddServer(Data.Server server) {
+	public async Task Vacuum() {
 		using var conn = pool.Take();
-		using var cmd = conn.Upsert("servers", new[] {
+		await conn.ExecuteAsync("VACUUM");
-			("id", SqliteType.Integer),
-			("name", SqliteType.Text),
-			("type", SqliteType.Text),
-		});
-
-		cmd.Set(":id", server.Id);
-		cmd.Set(":name", server.Name);
-		cmd.Set(":type", ServerTypes.ToString(server.Type));
-		cmd.ExecuteNonQuery();
-		UpdateServerStatistics(conn);
 	}
 
-	public List<Data.Server> GetAllServers() {
+	private async Task<long> ComputeMessageStatistics() {
-		var perf = log.Start();
-		var list = new List<Data.Server>();
-
 		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT id, name, type FROM servers");
+		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM messages", static reader => reader?.GetInt64(0) ?? 0L);
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			list.Add(new Data.Server {
-				Id = reader.GetUint64(0),
-				Name = reader.GetString(1),
-				Type = ServerTypes.FromString(reader.GetString(2)),
-			});
-		}
-
-		perf.End();
-		return list;
-	}
-
-	public void AddChannel(Channel channel) {
-		using var conn = pool.Take();
-		using var cmd = conn.Upsert("channels", new[] {
-			("id", SqliteType.Integer),
-			("server", SqliteType.Integer),
-			("name", SqliteType.Text),
-			("parent_id", SqliteType.Integer),
-			("position", SqliteType.Integer),
-			("topic", SqliteType.Text),
-			("nsfw", SqliteType.Integer),
-		});
-
-		cmd.Set(":id", channel.Id);
-		cmd.Set(":server", channel.Server);
-		cmd.Set(":name", channel.Name);
-		cmd.Set(":parent_id", channel.ParentId);
-		cmd.Set(":position", channel.Position);
-		cmd.Set(":topic", channel.Topic);
-		cmd.Set(":nsfw", channel.Nsfw);
-		cmd.ExecuteNonQuery();
-		UpdateChannelStatistics(conn);
-	}
-
-	public List<Channel> GetAllChannels() {
-		var list = new List<Channel>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT id, server, name, parent_id, position, topic, nsfw FROM channels");
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			list.Add(new Channel {
-				Id = reader.GetUint64(0),
-				Server = reader.GetUint64(1),
-				Name = reader.GetString(2),
-				ParentId = reader.IsDBNull(3) ? null : reader.GetUint64(3),
-				Position = reader.IsDBNull(4) ? null : reader.GetInt32(4),
-				Topic = reader.IsDBNull(5) ? null : reader.GetString(5),
-				Nsfw = reader.IsDBNull(6) ? null : reader.GetBoolean(6),
-			});
-		}
-
-		return list;
-	}
-
-	public void AddUsers(User[] users) {
-		using var conn = pool.Take();
-		using var tx = conn.BeginTransaction();
-		using var cmd = conn.Upsert("users", new[] {
-			("id", SqliteType.Integer),
-			("name", SqliteType.Text),
-			("avatar_url", SqliteType.Text),
-			("discriminator", SqliteType.Text),
-		});
-
-		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);
-			cmd.ExecuteNonQuery();
-		}
-
-		tx.Commit();
-		UpdateUserStatistics(conn);
-	}
-
-	public List<User> GetAllUsers() {
-		var perf = log.Start();
-		var list = new List<User>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT id, name, avatar_url, discriminator FROM users");
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			list.Add(new User {
-				Id = reader.GetUint64(0),
-				Name = reader.GetString(1),
-				AvatarUrl = reader.IsDBNull(2) ? null : reader.GetString(2),
-				Discriminator = reader.IsDBNull(3) ? null : reader.GetString(3),
-			});
-		}
-
-		perf.End();
-		return list;
-	}
-
-	public void AddMessages(Message[] messages) {
-		static SqliteCommand DeleteByMessageId(ISqliteConnection conn, string tableName) {
-			return conn.Delete(tableName, ("message_id", SqliteType.Integer));
-		}
-
-		static void ExecuteDeleteByMessageId(SqliteCommand cmd, object id) {
-			cmd.Set(":message_id", id);
-			cmd.ExecuteNonQuery();
-		}
-
-		bool addedAttachments = false;
-
-		using (var conn = pool.Take()) {
-			using var tx = conn.BeginTransaction();
-
-			using var messageCmd = conn.Upsert("messages", new[] {
-				("message_id", SqliteType.Integer),
-				("sender_id", SqliteType.Integer),
-				("channel_id", SqliteType.Integer),
-				("text", SqliteType.Text),
-				("timestamp", SqliteType.Integer),
-			});
-
-			using var deleteEditTimestampCmd = DeleteByMessageId(conn, "edit_timestamps");
-			using var deleteRepliedToCmd = DeleteByMessageId(conn, "replied_to");
-
-			using var deleteAttachmentsCmd = DeleteByMessageId(conn, "attachments");
-			using var deleteEmbedsCmd = DeleteByMessageId(conn, "embeds");
-			using var deleteReactionsCmd = DeleteByMessageId(conn, "reactions");
-
-			using var editTimestampCmd = conn.Insert("edit_timestamps", new [] {
-				("message_id", SqliteType.Integer),
-				("edit_timestamp", SqliteType.Integer),
-			});
-
-			using var repliedToCmd = conn.Insert("replied_to", new [] {
-				("message_id", SqliteType.Integer),
-				("replied_to_id", SqliteType.Integer),
-			});
-
-			using var attachmentCmd = conn.Insert("attachments", new[] {
-				("message_id", SqliteType.Integer),
-				("attachment_id", SqliteType.Integer),
-				("name", SqliteType.Text),
-				("type", SqliteType.Text),
-				("normalized_url", SqliteType.Text),
-				("download_url", SqliteType.Text),
-				("size", SqliteType.Integer),
-				("width", SqliteType.Integer),
-				("height", SqliteType.Integer),
-			});
-
-			using var embedCmd = conn.Insert("embeds", new[] {
-				("message_id", SqliteType.Integer),
-				("json", SqliteType.Text),
-			});
-
-			using var reactionCmd = conn.Insert("reactions", new[] {
-				("message_id", SqliteType.Integer),
-				("emoji_id", SqliteType.Integer),
-				("emoji_name", SqliteType.Text),
-				("emoji_flags", SqliteType.Integer),
-				("count", SqliteType.Integer),
-			});
-
-			foreach (var message in messages) {
-				object messageId = message.Id;
-
-				messageCmd.Set(":message_id", messageId);
-				messageCmd.Set(":sender_id", message.Sender);
-				messageCmd.Set(":channel_id", message.Channel);
-				messageCmd.Set(":text", message.Text);
-				messageCmd.Set(":timestamp", message.Timestamp);
-				messageCmd.ExecuteNonQuery();
-
-				ExecuteDeleteByMessageId(deleteEditTimestampCmd, messageId);
-				ExecuteDeleteByMessageId(deleteRepliedToCmd, messageId);
-
-				ExecuteDeleteByMessageId(deleteAttachmentsCmd, messageId);
-				ExecuteDeleteByMessageId(deleteEmbedsCmd, messageId);
-				ExecuteDeleteByMessageId(deleteReactionsCmd, messageId);
-
-				if (message.EditTimestamp is {} timestamp) {
-					editTimestampCmd.Set(":message_id", messageId);
-					editTimestampCmd.Set(":edit_timestamp", timestamp);
-					editTimestampCmd.ExecuteNonQuery();
-				}
-
-				if (message.RepliedToId is {} repliedToId) {
-					repliedToCmd.Set(":message_id", messageId);
-					repliedToCmd.Set(":replied_to_id", repliedToId);
-					repliedToCmd.ExecuteNonQuery();
-				}
-
-				if (!message.Attachments.IsEmpty) {
-					addedAttachments = true;
-
-					foreach (var attachment in message.Attachments) {
-						attachmentCmd.Set(":message_id", messageId);
-						attachmentCmd.Set(":attachment_id", attachment.Id);
-						attachmentCmd.Set(":name", attachment.Name);
-						attachmentCmd.Set(":type", attachment.Type);
-						attachmentCmd.Set(":normalized_url", attachment.NormalizedUrl);
-						attachmentCmd.Set(":download_url", attachment.DownloadUrl);
-						attachmentCmd.Set(":size", attachment.Size);
-						attachmentCmd.Set(":width", attachment.Width);
-						attachmentCmd.Set(":height", attachment.Height);
-						attachmentCmd.ExecuteNonQuery();
-					}
-				}
-
-				if (!message.Embeds.IsEmpty) {
-					foreach (var embed in message.Embeds) {
-						embedCmd.Set(":message_id", messageId);
-						embedCmd.Set(":json", embed.Json);
-						embedCmd.ExecuteNonQuery();
-					}
-				}
-
-				if (!message.Reactions.IsEmpty) {
-					foreach (var reaction in message.Reactions) {
-						reactionCmd.Set(":message_id", messageId);
-						reactionCmd.Set(":emoji_id", reaction.EmojiId);
-						reactionCmd.Set(":emoji_name", reaction.EmojiName);
-						reactionCmd.Set(":emoji_flags", (int) reaction.EmojiFlags);
-						reactionCmd.Set(":count", reaction.Count);
-						reactionCmd.ExecuteNonQuery();
-					}
-				}
-			}
-
-			tx.Commit();
-		}
-
-		totalMessagesComputer.Recompute();
-
-		if (addedAttachments) {
-			totalAttachmentsComputer.Recompute();
-		}
-	}
-
-	public int CountMessages(MessageFilter? filter = null) {
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT COUNT(*) FROM messages" + filter.GenerateWhereClause());
-		using var reader = cmd.ExecuteReader();
-
-		return reader.Read() ? reader.GetInt32(0) : 0;
-	}
-
-	public List<Message> GetMessages(MessageFilter? filter = null) {
-		var perf = log.Start();
-		var list = new List<Message>();
-
-		var attachments = GetAllAttachments();
-		var embeds = GetAllEmbeds();
-		var reactions = GetAllReactions();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command($"""
-		                              SELECT m.message_id, m.sender_id, m.channel_id, m.text, m.timestamp, et.edit_timestamp, rt.replied_to_id
-		                              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")}
-		                              """);
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			ulong id = reader.GetUint64(0);
-
-			list.Add(new Message {
-				Id = id,
-				Sender = reader.GetUint64(1),
-				Channel = reader.GetUint64(2),
-				Text = reader.GetString(3),
-				Timestamp = reader.GetInt64(4),
-				EditTimestamp = reader.IsDBNull(5) ? null : reader.GetInt64(5),
-				RepliedToId = reader.IsDBNull(6) ? null : reader.GetUint64(6),
-				Attachments = attachments.GetListOrNull(id)?.ToImmutableArray() ?? ImmutableArray<Attachment>.Empty,
-				Embeds = embeds.GetListOrNull(id)?.ToImmutableArray() ?? ImmutableArray<Embed>.Empty,
-				Reactions = reactions.GetListOrNull(id)?.ToImmutableArray() ?? ImmutableArray<Reaction>.Empty,
-			});
-		}
-
-		perf.End();
-		return list;
-	}
-
-	public HashSet<ulong> GetMessageIds(MessageFilter? filter = null) {
-		var perf = log.Start();
-		var ids = new HashSet<ulong>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT message_id FROM messages" + filter.GenerateWhereClause());
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			ids.Add(reader.GetUint64(0));
-		}
-
-		perf.End();
-		return ids;
-	}
-
-	public void RemoveMessages(MessageFilter filter, FilterRemovalMode mode) {
-		var perf = log.Start();
-
-		DeleteFromTable("messages", filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching));
-		totalMessagesComputer.Recompute();
-
-		perf.End();
-	}
-
-	public int CountAttachments(AttachmentFilter? filter = null) {
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT COUNT(DISTINCT normalized_url) FROM attachments a" + filter.GenerateWhereClause("a"));
-		using var reader = cmd.ExecuteReader();
-
-		return reader.Read() ? reader.GetInt32(0) : 0;
-	}
-
-	public void AddDownload(Data.Download download) {
-		using var conn = pool.Take();
-		using var cmd = conn.Upsert("downloads", new[] {
-			("normalized_url", SqliteType.Text),
-			("download_url", SqliteType.Text),
-			("status", SqliteType.Integer),
-			("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);
-		cmd.ExecuteNonQuery();
-
-		totalDownloadsComputer.Recompute();
-	}
-
-	public List<Data.Download> GetDownloadsWithoutData() {
-		var list = new List<Data.Download>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT normalized_url, download_url, status, size FROM downloads");
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			string normalizedUrl = reader.GetString(0);
-			string downloadUrl = reader.GetString(1);
-			var status = (DownloadStatus) reader.GetInt32(2);
-			ulong size = reader.GetUint64(3);
-
-			list.Add(new Data.Download(normalizedUrl, downloadUrl, status, size));
-		}
-
-		return list;
-	}
-
-	public Data.Download GetDownloadWithData(Data.Download download) {
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT blob FROM downloads WHERE normalized_url = :url");
-		cmd.AddAndSet(":url", SqliteType.Text, download.NormalizedUrl);
-
-		using var reader = cmd.ExecuteReader();
-
-		if (reader.Read() && !reader.IsDBNull(0)) {
-			return download.WithData((byte[]) reader["blob"]);
-		}
-		else {
-			return download;
-		}
-	}
-
-	public DownloadedAttachment? GetDownloadedAttachment(string normalizedUrl) {
-		using var conn = pool.Take();
-		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
-		                             """);
-
-		cmd.AddAndSet(":normalized_url", SqliteType.Text, normalizedUrl);
-		cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
-
-		using var reader = cmd.ExecuteReader();
-
-		if (!reader.Read()) {
-			return null;
-		}
-
-		return new DownloadedAttachment {
-			Type = reader.IsDBNull(0) ? null : reader.GetString(0),
-			Data = (byte[]) reader["blob"],
-		};
-	}
-
-	public void EnqueueDownloadItems(AttachmentFilter? filter = null) {
-		using var conn = pool.Take();
-		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);
-		cmd.ExecuteNonQuery();
-	}
-
-	public List<DownloadItem> PullEnqueuedDownloadItems(int count) {
-		var found = new List<DownloadItem>();
-		var pulled = new List<DownloadItem>();
-
-		using var conn = pool.Take();
-		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);
-			cmd.AddAndSet(":limit", SqliteType.Integer, Math.Max(0, count));
-
-			using var reader = cmd.ExecuteReader();
-
-			while (reader.Read()) {
-				found.Add(new DownloadItem {
-					NormalizedUrl = reader.GetString(0),
-					DownloadUrl = reader.GetString(1),
-					Size = reader.GetUint64(2),
-				});
-			}
-		}
-
-		if (found.Count != 0) {
-			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);
-			cmd.AddAndSet(":downloading", SqliteType.Integer, (int) DownloadStatus.Downloading);
-			cmd.Add(":normalized_url", SqliteType.Text);
-
-			foreach (var item in found) {
-				cmd.Set(":normalized_url", item.NormalizedUrl);
-
-				if (cmd.ExecuteNonQuery() == 1) {
-					pulled.Add(item);
-				}
-			}
-		}
-
-		return pulled;
-	}
-
-	public void RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {
-		DeleteFromTable("downloads", filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching));
-		totalDownloadsComputer.Recompute();
-	}
-
-	public DownloadStatusStatistics GetDownloadStatusStatistics() {
-		static void LoadUndownloadedStatistics(ISqliteConnection conn, DownloadStatusStatistics result) {
-			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)");
-			using var reader = cmd.ExecuteReader();
-
-			if (reader.Read()) {
-				result.SkippedCount = reader.GetInt32(0);
-				result.SkippedSize = reader.GetUint64(1);
-			}
-		}
-
-		static void LoadSuccessStatistics(ISqliteConnection conn, DownloadStatusStatistics result) {
-			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);
-
-			using var reader = cmd.ExecuteReader();
-
-			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();
-
-		using var conn = pool.Take();
-		LoadUndownloadedStatistics(conn, result);
-		LoadSuccessStatistics(conn, result);
-		return result;
-	}
-
-	private MultiDictionary<ulong, Attachment> GetAllAttachments() {
-		var dict = new MultiDictionary<ulong, Attachment>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT message_id, attachment_id, name, type, normalized_url, download_url, size, width, height FROM attachments");
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			ulong messageId = reader.GetUint64(0);
-
-			dict.Add(messageId, new Attachment {
-				Id = reader.GetUint64(1),
-				Name = reader.GetString(2),
-				Type = reader.IsDBNull(3) ? null : reader.GetString(3),
-				NormalizedUrl = reader.GetString(4),
-				DownloadUrl = reader.GetString(5),
-				Size = reader.GetUint64(6),
-				Width = reader.IsDBNull(7) ? null : reader.GetInt32(7),
-				Height = reader.IsDBNull(8) ? null : reader.GetInt32(8),
-			});
-		}
-
-		return dict;
-	}
-
-	private MultiDictionary<ulong, Embed> GetAllEmbeds() {
-		var dict = new MultiDictionary<ulong, Embed>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT message_id, json FROM embeds");
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			ulong messageId = reader.GetUint64(0);
-
-			dict.Add(messageId, new Embed {
-				Json = reader.GetString(1),
-			});
-		}
-
-		return dict;
-	}
-
-	private MultiDictionary<ulong, Reaction> GetAllReactions() {
-		var dict = new MultiDictionary<ulong, Reaction>();
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command("SELECT message_id, emoji_id, emoji_name, emoji_flags, count FROM reactions");
-		using var reader = cmd.ExecuteReader();
-
-		while (reader.Read()) {
-			ulong messageId = reader.GetUint64(0);
-
-			dict.Add(messageId, new Reaction {
-				EmojiId = reader.IsDBNull(1) ? null : reader.GetUint64(1),
-				EmojiName = reader.IsDBNull(2) ? null : reader.GetString(2),
-				EmojiFlags = (EmojiFlags) reader.GetInt16(3),
-				Count = reader.GetInt32(4),
-			});
-		}
-
-		return dict;
-	}
-
-	private void DeleteFromTable(string table, string whereClause) {
-		// Rider is being stupid...
-		StringBuilder build = new StringBuilder()
-		                      .Append("DELETE ")
-		                      .Append("FROM ")
-		                      .Append(table)
-		                      .Append(whereClause);
-
-		using var conn = pool.Take();
-		using var cmd = conn.Command(build.ToString());
-		cmd.ExecuteNonQuery();
-	}
-
-	public void Vacuum() {
-		using var conn = pool.Take();
-		using var cmd = conn.Command("VACUUM");
-		cmd.ExecuteNonQuery();
-	}
-
-	private void UpdateServerStatistics(ISqliteConnection conn) {
-		Statistics.TotalServers = conn.SelectScalar("SELECT COUNT(*) FROM servers") as long? ?? 0;
-	}
-
-	private void UpdateChannelStatistics(ISqliteConnection conn) {
-		Statistics.TotalChannels = conn.SelectScalar("SELECT COUNT(*) FROM channels") as long? ?? 0;
-	}
-
-	private void UpdateUserStatistics(ISqliteConnection conn) {
-		Statistics.TotalUsers = conn.SelectScalar("SELECT COUNT(*) FROM users") as long? ?? 0;
-	}
-
-	private long ComputeMessageStatistics() {
-		using var conn = pool.Take();
-		return conn.SelectScalar("SELECT COUNT(*) FROM messages") as long? ?? 0L;
 	}
 
 	private void UpdateMessageStatistics(long totalMessages) {
 		Statistics.TotalMessages = totalMessages;
 	}
 
-	private long ComputeAttachmentStatistics() {
+	private async Task<long> ComputeAttachmentStatistics() {
 		using var conn = pool.Take();
-		return conn.SelectScalar("SELECT COUNT(DISTINCT normalized_url) FROM attachments") as long? ?? 0L;
+		return await conn.ExecuteReaderAsync("SELECT COUNT(DISTINCT normalized_url) FROM attachments", static reader => reader?.GetInt64(0) ?? 0L);
 	}
 
 	private void UpdateAttachmentStatistics(long totalAttachments) {
 		Statistics.TotalAttachments = totalAttachments;
 	}
 
-	private long ComputeDownloadStatistics() {
+	private async Task<long> ComputeDownloadStatistics() {
 		using var conn = pool.Take();
-		return conn.SelectScalar("SELECT COUNT(*) FROM downloads") as long? ?? 0L;
+		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM downloads", static reader => reader?.GetInt64(0) ?? 0L);
 	}
 
 	private void UpdateDownloadStatistics(long totalDownloads) {

app/Server/Database/Sqlite/SqliteFilters.cs

@@ -8,9 +8,13 @@ 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 string GenerateWhereClause(this MessageFilter? filter, string? tableAlias = null, bool invert = false) {
-		if (filter == null) {
+		if (filter == null || filter.IsEmpty) {
-			return "";
+			return WhereAll(invert);
 		}
 
 		var where = new SqliteWhereGenerator(tableAlias, invert);
@@ -39,8 +43,8 @@ static class SqliteFilters {
 	}
 
 	public static string GenerateWhereClause(this AttachmentFilter? filter, string? tableAlias = null, bool invert = false) {
-		if (filter == null) {
+		if (filter == null || filter.IsEmpty) {
-			return "";
+			return WhereAll(invert);
 		}
 
 		var where = new SqliteWhereGenerator(tableAlias, invert);
@@ -60,8 +64,8 @@ static class SqliteFilters {
 	}
 
 	public static string GenerateWhereClause(this DownloadItemFilter? filter, string? tableAlias = null, bool invert = false) {
-		if (filter == null) {
+		if (filter == null || filter.IsEmpty) {
-			return "";
+			return WhereAll(invert);
 		}
 
 		var where = new SqliteWhereGenerator(tableAlias, invert);

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

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

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

@@ -1,12 +1,16 @@
 using System;
+using System.Data.Common;
 using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using JetBrains.Annotations;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Utils;
 
 static class SqliteExtensions {
-	public static SqliteTransaction BeginTransaction(this ISqliteConnection conn) {
+	public static ValueTask<DbTransaction> BeginTransactionAsync(this ISqliteConnection conn) {
-		return conn.InnerConnection.BeginTransaction();
+		return conn.InnerConnection.BeginTransactionAsync();
 	}
 
 	public static SqliteCommand Command(this ISqliteConnection conn, string sql) {
@@ -15,14 +19,16 @@ static class SqliteExtensions {
 		return cmd;
 	}
 
-	public static void Execute(this ISqliteConnection conn, string sql) {
+	public static async Task<int> ExecuteAsync(this ISqliteConnection conn, [LanguageInjection("sql")] string sql, CancellationToken cancellationToken = default) {
-		using var cmd = conn.Command(sql);
+		await using var cmd = conn.Command(sql);
-		cmd.ExecuteNonQuery();
+		return await cmd.ExecuteNonQueryAsync(cancellationToken);
 	}
 	
-	public static object? SelectScalar(this ISqliteConnection conn, string sql) {
+	public static async Task<T> ExecuteReaderAsync<T>(this ISqliteConnection conn, string sql, Func<SqliteDataReader?, T> readFunction, CancellationToken cancellationToken = default) {
-		using var cmd = conn.Command(sql);
+		await using var cmd = conn.Command(sql);
-		return cmd.ExecuteScalar();
+		await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
+
+		return reader.Read() ? readFunction(reader) : readFunction(null);
 	}
 
 	public static SqliteCommand Insert(this ISqliteConnection conn, string tableName, (string Name, SqliteType Type)[] columns) {

app/Server/Download/DownloaderTask.cs

@@ -45,7 +45,7 @@ sealed class DownloaderTask : IAsyncDisposable {
 
 	private async Task RunQueueWriterTask() {
 		while (await downloadQueue.Writer.WaitToWriteAsync(cancellationToken)) {
-			var newItems = db.PullEnqueuedDownloadItems(QueueSize);
+			var newItems = await db.Downloads.PullEnqueuedDownloadItems(QueueSize, cancellationToken).ToListAsync(cancellationToken);
 			if (newItems.Count == 0) {
 				await Task.Delay(TimeSpan.FromMilliseconds(50), cancellationToken);
 				continue;
@@ -70,14 +70,14 @@ sealed class DownloaderTask : IAsyncDisposable {
 
 			try {
 				var downloadedBytes = await client.GetByteArrayAsync(item.DownloadUrl, cancellationToken);
-				db.AddDownload(Data.Download.NewSuccess(item, downloadedBytes));
+				await db.Downloads.AddDownload(Data.Download.NewSuccess(item, downloadedBytes));
 			} catch (OperationCanceledException) {
 				// Ignore.
 			} catch (HttpRequestException e) {
-				db.AddDownload(Data.Download.NewFailure(item, e.StatusCode, item.Size));
+				await db.Downloads.AddDownload(Data.Download.NewFailure(item, e.StatusCode, item.Size));
 				log.Error(e);
 			} catch (Exception e) {
-				db.AddDownload(Data.Download.NewFailure(item, null, item.Size));
+				await db.Downloads.AddDownload(Data.Download.NewFailure(item, null, item.Size));
 				log.Error(e);
 			} finally {
 				try {

app/Server/Endpoints/GetAttachmentEndpoint.cs

@@ -10,15 +10,15 @@ namespace DHT.Server.Endpoints;
 sealed class GetAttachmentEndpoint : BaseEndpoint {
 	public GetAttachmentEndpoint(IDatabaseFile db) : base(db) {}
 
-	protected override Task<IHttpOutput> Respond(HttpContext ctx) {
+	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
 		string attachmentUrl = WebUtility.UrlDecode((string) ctx.Request.RouteValues["url"]!);
-		DownloadedAttachment? maybeDownloadedAttachment = Db.GetDownloadedAttachment(attachmentUrl);
+		DownloadedAttachment? maybeDownloadedAttachment = await Db.Downloads.GetDownloadedAttachment(attachmentUrl);
 
 		if (maybeDownloadedAttachment is {} downloadedAttachment) {
-			return Task.FromResult<IHttpOutput>(new HttpOutput.File(downloadedAttachment.Type, downloadedAttachment.Data));
+			return new HttpOutput.File(downloadedAttachment.Type, downloadedAttachment.Data);
 		}
 		else {
-			return Task.FromResult<IHttpOutput>(new HttpOutput.Redirect(attachmentUrl, permanent: false));
+			return new HttpOutput.Redirect(attachmentUrl, permanent: false);
 		}
 	}
 }

app/Server/Endpoints/TrackChannelEndpoint.cs

@@ -16,8 +16,8 @@ sealed class TrackChannelEndpoint : BaseEndpoint {
 		var server = ReadServer(root.RequireObject("server"), "server");
 		var channel = ReadChannel(root.RequireObject("channel"), "channel", server.Id);
 
-		Db.AddServer(server);
+		await Db.Servers.Add([server]);
-		Db.AddChannel(channel);
+		await Db.Channels.Add([channel]);
 
 		return HttpOutput.None;
 	}

app/Server/Endpoints/TrackMessagesEndpoint.cs

@@ -39,9 +39,9 @@ sealed class TrackMessagesEndpoint : BaseEndpoint {
 		}
 
 		var addedMessageFilter = new MessageFilter { MessageIds = addedMessageIds };
-		bool anyNewMessages = Db.CountMessages(addedMessageFilter) < messages.Length;
+		bool anyNewMessages = await Db.Messages.Count(addedMessageFilter) < addedMessageIds.Count;
 
-		Db.AddMessages(messages);
+		await Db.Messages.Add(messages);
 
 		return new HttpOutput.Text(anyNewMessages ? HasNewMessages : NoNewMessages);
 	}
@@ -54,9 +54,9 @@ sealed class TrackMessagesEndpoint : BaseEndpoint {
 		Timestamp = json.RequireLong("timestamp", path),
 		EditTimestamp = json.HasKey("editTimestamp") ? json.RequireLong("editTimestamp", path) : null,
 		RepliedToId = json.HasKey("repliedToId") ? json.RequireSnowflake("repliedToId", path) : null,
-		Attachments = json.HasKey("attachments") ? ReadAttachments(json.RequireArray("attachments", path + ".attachments"), path + ".attachments[]").ToImmutableArray() : ImmutableArray<Attachment>.Empty,
+		Attachments = json.HasKey("attachments") ? ReadAttachments(json.RequireArray("attachments", path + ".attachments"), path + ".attachments[]").ToImmutableList() : ImmutableList<Attachment>.Empty,
-		Embeds = json.HasKey("embeds") ? ReadEmbeds(json.RequireArray("embeds", path + ".embeds"), path + ".embeds[]").ToImmutableArray() : ImmutableArray<Embed>.Empty,
+		Embeds = json.HasKey("embeds") ? ReadEmbeds(json.RequireArray("embeds", path + ".embeds"), path + ".embeds[]").ToImmutableList() : ImmutableList<Embed>.Empty,
-		Reactions = json.HasKey("reactions") ? ReadReactions(json.RequireArray("reactions", path + ".reactions"), path + ".reactions[]").ToImmutableArray() : ImmutableArray<Reaction>.Empty,
+		Reactions = json.HasKey("reactions") ? ReadReactions(json.RequireArray("reactions", path + ".reactions"), path + ".reactions[]").ToImmutableList() : ImmutableList<Reaction>.Empty,
 	};
 
 	[SuppressMessage("ReSharper", "ConvertToLambdaExpression")]

app/Server/Endpoints/TrackUsersEndpoint.cs

@@ -25,7 +25,7 @@ sealed class TrackUsersEndpoint : BaseEndpoint {
 			users[i++] = ReadUser(user, "user");
 		}
 
-		Db.AddUsers(users);
+		await Db.Users.Add(users);
 
 		return HttpOutput.None;
 	}

app/Server/Server.csproj

@@ -12,6 +12,7 @@
   
   <ItemGroup>
     <PackageReference Include="Microsoft.Data.Sqlite" Version="8.0.0" />
+    <PackageReference Include="System.Linq.Async" Version="6.0.1" />
     <PackageReference Include="System.Reactive" Version="6.0.0" />
   </ItemGroup>
   

app/Utils/Tasks/AsyncValueComputer.cs

@@ -15,7 +15,7 @@ public sealed class AsyncValueComputer<TValue> {
 	private SoftHardCancellationToken? currentCancellationTokenSource;
 	private bool wasHardCancelled = false;
 
-	private Func<TValue>? currentComputeFunction;
+	private Func<Task<TValue>>? currentComputeFunction;
 	private bool hasComputeFunctionChanged = false;
 
 	private AsyncValueComputer(Action<TValue> resultProcessor, TaskScheduler resultTaskScheduler, bool processOutdatedResults) {
@@ -31,7 +31,7 @@ public sealed class AsyncValueComputer<TValue> {
 		}
 	}
 
-	public void Compute(Func<TValue> func) {
+	public void Compute(Func<Task<TValue>> func) {
 		lock (stateLock) {
 			wasHardCancelled = false;
 
@@ -47,7 +47,7 @@ public sealed class AsyncValueComputer<TValue> {
 	}
 
 	[SuppressMessage("ReSharper", "MethodSupportsCancellation")]
-	private void EnqueueComputation(Func<TValue> func) {
+	private void EnqueueComputation(Func<Task<TValue>> func) {
 		var cancellationTokenSource = new SoftHardCancellationToken();
 
 		currentCancellationTokenSource?.RequestSoftCancellation();
@@ -84,9 +84,9 @@ public sealed class AsyncValueComputer<TValue> {
 
 	public sealed class Single {
 		private readonly AsyncValueComputer<TValue> baseComputer;
-		private readonly Func<TValue> resultComputer;
+		private readonly Func<Task<TValue>> resultComputer;
 
-		internal Single(AsyncValueComputer<TValue> baseComputer, Func<TValue> resultComputer) {
+		internal Single(AsyncValueComputer<TValue> baseComputer, Func<Task<TValue>> resultComputer) {
 			this.baseComputer = baseComputer;
 			this.resultComputer = resultComputer;
 		}
@@ -94,6 +94,10 @@ public sealed class AsyncValueComputer<TValue> {
 		public void Recompute() {
 			baseComputer.Compute(resultComputer);
 		}
+
+		public void Cancel() {
+			baseComputer.Cancel();
+		}
 	}
 
 	public static Builder WithResultProcessor(Action<TValue> resultProcessor, TaskScheduler? scheduler = null) {
@@ -119,7 +123,7 @@ public sealed class AsyncValueComputer<TValue> {
 			return new AsyncValueComputer<TValue>(resultProcessor, resultTaskScheduler, processOutdatedResults);
 		}
 
-		public Single BuildWithComputer(Func<TValue> resultComputer) {
+		public Single BuildWithComputer(Func<Task<TValue>> resultComputer) {
 			return new Single(Build(), resultComputer);
 		}
 	}

app/Utils/Tasks/RestartableTask.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Tasks;
+
+public sealed class RestartableTask<T>(Action<T> resultProcessor, TaskScheduler resultScheduler) {
+	private readonly object monitor = new ();
+
+	private CancellationTokenSource? cancellationTokenSource;
+
+	public void Restart(Func<CancellationToken, Task<T>> resultComputer) {
+		lock (monitor) {
+			Cancel();
+
+			cancellationTokenSource = new CancellationTokenSource();
+			
+			var taskCancellationTokenSource = cancellationTokenSource;
+			var taskCancellationToken = taskCancellationTokenSource.Token;
+
+			Task.Run(() => resultComputer(taskCancellationToken), taskCancellationToken)
+			    .ContinueWith(task => resultProcessor(task.Result), taskCancellationToken, TaskContinuationOptions.OnlyOnRanToCompletion, resultScheduler)
+			    .ContinueWith(_ => OnTaskFinished(taskCancellationTokenSource), CancellationToken.None);
+		}
+	}
+
+	public void Cancel() {
+		lock (monitor) {
+			if (cancellationTokenSource != null) {
+				cancellationTokenSource.Cancel();
+				cancellationTokenSource = null;
+			}
+		}
+	}
+
+	private void OnTaskFinished(CancellationTokenSource taskCancellationTokenSource) {
+		lock (monitor) {
+			taskCancellationTokenSource.Dispose();
+
+			if (cancellationTokenSource == taskCancellationTokenSource) {
+				cancellationTokenSource = null;
+			}
+		}
+	}
+}

app/Utils/Tasks/ThrottledTask.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Threading;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Tasks;
+
+public abstract class ThrottledTaskBase<T> : IDisposable {
+	private readonly Channel<Func<CancellationToken, T>> taskChannel = Channel.CreateBounded<Func<CancellationToken, T>>(new BoundedChannelOptions(capacity: 1) {
+		SingleReader = true,
+		SingleWriter = false,
+		AllowSynchronousContinuations = false,
+		FullMode = BoundedChannelFullMode.DropOldest
+	});
+	
+	private readonly CancellationTokenSource cancellationTokenSource = new ();
+	
+	internal ThrottledTaskBase() {}
+
+	protected async Task ReaderTask() {
+		var cancellationToken = cancellationTokenSource.Token;
+
+		try {
+			await foreach (var item in taskChannel.Reader.ReadAllAsync(cancellationToken)) {
+				try {
+					await Run(item, cancellationToken);
+				} catch (OperationCanceledException) {
+					throw;
+				} catch (Exception) {
+					// Ignore.
+				}
+			}
+		} catch (OperationCanceledException) {
+			// Ignore.
+		} finally {
+			cancellationTokenSource.Dispose();
+		}
+	}
+	
+	protected abstract Task Run(Func<CancellationToken, T> func, CancellationToken cancellationToken);
+
+	public void Post(Func<CancellationToken, T> resultComputer) {
+		taskChannel.Writer.TryWrite(resultComputer);
+	}
+
+	public void Dispose() {
+		taskChannel.Writer.Complete();
+		cancellationTokenSource.Cancel();
+	}
+}
+
+public sealed class ThrottledTask : ThrottledTaskBase<Task> {
+	private readonly Action resultProcessor;
+	private readonly TaskScheduler resultScheduler;
+
+	public ThrottledTask(Action resultProcessor, TaskScheduler resultScheduler) {
+		this.resultProcessor = resultProcessor;
+		this.resultScheduler = resultScheduler;
+
+		Task.Run(ReaderTask);
+	}
+
+	protected override async Task Run(Func<CancellationToken, Task> func, CancellationToken cancellationToken) {
+		await func(cancellationToken);
+		await Task.Factory.StartNew(resultProcessor, cancellationToken, TaskCreationOptions.None, resultScheduler);
+	}
+}
+
+public sealed class ThrottledTask<T> : ThrottledTaskBase<Task<T>> {
+	private readonly Action<T> resultProcessor;
+	private readonly TaskScheduler resultScheduler;
+
+	public ThrottledTask(Action<T> resultProcessor, TaskScheduler resultScheduler) {
+		this.resultProcessor = resultProcessor;
+		this.resultScheduler = resultScheduler;
+
+		Task.Run(ReaderTask);
+	}
+
+	protected override async Task Run(Func<CancellationToken, Task<T>> func, CancellationToken cancellationToken) {
+		T result = await func(cancellationToken);
+		await Task.Factory.StartNew(() => resultProcessor(result), cancellationToken, TaskCreationOptions.None, resultScheduler);
+	}
+}