Fix trailing spaces Rider generates in code

app/Desktop/Main/Controls/AttachmentFilterPanelModel.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using DHT.Desktop.Common;
+using DHT.Server;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
 using DHT.Utils.Models;
@@ -47,7 +48,7 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 
 	public IEnumerable<Unit> Units => AllUnits;
 
-	private readonly IDatabaseFile db;
+	private readonly State state;
 	private readonly string verb;
 
 	private readonly AsyncValueComputer<long> matchingAttachmentCountComputer;
@@ -55,10 +56,10 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 	private long? totalAttachmentCount;
 
 	[Obsolete("Designer")]
-	public AttachmentFilterPanelModel() : this(DummyDatabaseFile.Instance) {}
+	public AttachmentFilterPanelModel() : this(State.Dummy) {}
 
-	public AttachmentFilterPanelModel(IDatabaseFile db, string verb = "Matches") {
+	public AttachmentFilterPanelModel(State state, string verb = "Matches") {
-		this.db = db;
+		this.state = state;
 		this.verb = verb;
 
 		this.matchingAttachmentCountComputer = AsyncValueComputer<long>.WithResultProcessor(SetAttachmentCounts).Build();
@@ -66,11 +67,11 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 		UpdateFilterStatistics();
 
 		PropertyChanged += OnPropertyChanged;
-		db.Statistics.PropertyChanged += OnDbStatisticsChanged;
+		state.Db.Statistics.PropertyChanged += OnDbStatisticsChanged;
 	}
 
 	public void Dispose() {
-		db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
+		state.Db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
 	}
 
 	private void OnPropertyChanged(object? sender, PropertyChangedEventArgs e) {
@@ -81,7 +82,7 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 
 	private void OnDbStatisticsChanged(object? sender, PropertyChangedEventArgs e) {
 		if (e.PropertyName == nameof(DatabaseStatistics.TotalAttachments)) {
-			totalAttachmentCount = db.Statistics.TotalAttachments;
+			totalAttachmentCount = state.Db.Statistics.TotalAttachments;
 			UpdateFilterStatistics();
 		}
 	}
@@ -96,7 +97,7 @@ sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
 		else {
 			matchingAttachmentCount = null;
 			UpdateFilterStatisticsText();
-			matchingAttachmentCountComputer.Compute(() => db.CountAttachments(filter));
+			matchingAttachmentCountComputer.Compute(() => state.Db.CountAttachments(filter));
 		}
 	}
 

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.Server;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
@@ -62,7 +63,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	}
 
 	public HashSet<ulong> IncludedChannels {
-		get => includedChannels ?? db.GetAllChannels().Select(static channel => channel.Id).ToHashSet();
+		get => includedChannels ?? state.Db.GetAllChannels().Select(static channel => channel.Id).ToHashSet();
 		set => Change(ref includedChannels, value);
 	}
 
@@ -72,7 +73,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	}
 
 	public HashSet<ulong> IncludedUsers {
-		get => includedUsers ?? db.GetAllUsers().Select(static user => user.Id).ToHashSet();
+		get => includedUsers ?? state.Db.GetAllUsers().Select(static user => user.Id).ToHashSet();
 		set => Change(ref includedUsers, value);
 	}
 
@@ -91,7 +92,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	}
 
 	private readonly Window window;
-	private readonly IDatabaseFile db;
+	private readonly State state;
 	private readonly string verb;
 
 	private readonly AsyncValueComputer<long> exportedMessageCountComputer;
@@ -99,11 +100,11 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	private long? totalMessageCount;
 
 	[Obsolete("Designer")]
-	public MessageFilterPanelModel() : this(null!, DummyDatabaseFile.Instance) {}
+	public MessageFilterPanelModel() : this(null!, State.Dummy) {}
 
-	public MessageFilterPanelModel(Window window, IDatabaseFile db, string verb = "Matches") {
+	public MessageFilterPanelModel(Window window, State state, string verb = "Matches") {
 		this.window = window;
-		this.db = db;
+		this.state = state;
 		this.verb = verb;
 
 		this.exportedMessageCountComputer = AsyncValueComputer<long>.WithResultProcessor(SetExportedMessageCount).Build();
@@ -113,11 +114,11 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		UpdateUserFilterLabel();
 
 		PropertyChanged += OnPropertyChanged;
-		db.Statistics.PropertyChanged += OnDbStatisticsChanged;
+		state.Db.Statistics.PropertyChanged += OnDbStatisticsChanged;
 	}
 
 	public void Dispose() {
-		db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
+		state.Db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
 	}
 
 	private void OnPropertyChanged(object? sender, PropertyChangedEventArgs e) {
@@ -136,7 +137,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 
 	private void OnDbStatisticsChanged(object? sender, PropertyChangedEventArgs e) {
 		if (e.PropertyName == nameof(DatabaseStatistics.TotalMessages)) {
-			totalMessageCount = db.Statistics.TotalMessages;
+			totalMessageCount = state.Db.Statistics.TotalMessages;
 			UpdateFilterStatistics();
 		}
 		else if (e.PropertyName == nameof(DatabaseStatistics.TotalChannels)) {
@@ -157,7 +158,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		else {
 			exportedMessageCount = null;
 			UpdateFilterStatisticsText();
-			exportedMessageCountComputer.Compute(() => db.CountMessages(filter));
+			exportedMessageCountComputer.Compute(() => state.Db.CountMessages(filter));
 		}
 	}
 
@@ -175,11 +176,11 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	}
 
 	public async void OpenChannelFilterDialog() {
-		var servers = db.GetAllServers().ToDictionary(static server => server.Id);
+		var servers = state.Db.GetAllServers().ToDictionary(static server => server.Id);
 		var items = new List<CheckBoxItem<ulong>>();
 		var included = IncludedChannels;
 
-		foreach (var channel in db.GetAllChannels()) {
+		foreach (var channel in state.Db.GetAllChannels()) {
 			var channelId = channel.Id;
 			var channelName = channel.Name;
 
@@ -223,7 +224,7 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 		var items = new List<CheckBoxItem<ulong>>();
 		var included = IncludedUsers;
 
-		foreach (var user in db.GetAllUsers()) {
+		foreach (var user in state.Db.GetAllUsers()) {
 			var name = user.Name;
 			var discriminator = user.Discriminator;
 
@@ -240,13 +241,13 @@ sealed class MessageFilterPanelModel : BaseModel, IDisposable {
 	}
 
 	private void UpdateChannelFilterLabel() {
-		long total = db.Statistics.TotalChannels;
+		long total = state.Db.Statistics.TotalChannels;
 		long included = FilterByChannel ? IncludedChannels.Count : total;
 		ChannelFilterLabel = "Selected " + included.Format() + " / " + total.Pluralize("channel") + ".";
 	}
 
 	private void UpdateUserFilterLabel() {
-		long total = db.Statistics.TotalUsers;
+		long total = state.Db.Statistics.TotalUsers;
 		long included = FilterByUser ? IncludedUsers.Count : total;
 		UserFilterLabel = "Selected " + included.Format() + " / " + total.Pluralize("user") + ".";
 	}

app/Desktop/Main/Controls/ServerConfigurationPanelModel.cs

@@ -2,7 +2,7 @@ using System;
 using Avalonia.Controls;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Server;
-using DHT.Server.Database;
+using DHT.Server;
 using DHT.Server.Service;
 using DHT.Utils.Models;
 
@@ -46,7 +46,7 @@ sealed class ServerConfigurationPanelModel : BaseModel, IDisposable {
 	private readonly ServerManager serverManager;
 
 	[Obsolete("Designer")]
-	public ServerConfigurationPanelModel() : this(null!, new ServerManager(DummyDatabaseFile.Instance)) {}
+	public ServerConfigurationPanelModel() : this(null!, new ServerManager(State.Dummy)) {}
 
 	public ServerConfigurationPanelModel(Window window, ServerManager serverManager) {
 		this.window = window;

app/Desktop/Main/Controls/StatusBar.axaml

@@ -45,17 +45,17 @@
         <Rectangle />
         <StackPanel Orientation="Vertical">
             <TextBlock Classes="label">Servers</TextBlock>
-            <TextBlock Classes="value" Text="{Binding DatabaseStatistics.TotalServers, Converter={StaticResource NumberValueConverter}}" />
+            <TextBlock Classes="value" Text="{Binding DatabaseStatistics.TotalServers, Mode=OneWay, Converter={StaticResource NumberValueConverter}}" />
         </StackPanel>
         <Rectangle />
         <StackPanel Orientation="Vertical">
             <TextBlock Classes="label">Channels</TextBlock>
-            <TextBlock Classes="value" Text="{Binding DatabaseStatistics.TotalChannels, Converter={StaticResource NumberValueConverter}}" />
+            <TextBlock Classes="value" Text="{Binding DatabaseStatistics.TotalChannels, Mode=OneWay, Converter={StaticResource NumberValueConverter}}" />
         </StackPanel>
         <Rectangle />
         <StackPanel Orientation="Vertical">
             <TextBlock Classes="label">Messages</TextBlock>
-            <TextBlock Classes="value" Text="{Binding DatabaseStatistics.TotalMessages, Converter={StaticResource NumberValueConverter}}" />
+            <TextBlock Classes="value" Text="{Binding DatabaseStatistics.TotalMessages, Mode=OneWay, Converter={StaticResource NumberValueConverter}}" />
         </StackPanel>
     </StackPanel>
 

app/Desktop/Main/MainWindow.axaml

@@ -11,7 +11,7 @@
         Width="800" Height="500"
         MinWidth="520" MinHeight="300"
         WindowStartupLocation="CenterScreen"
-        Closed="OnClosed">
+        Closing="OnClosing">
 
     <Design.DataContext>
         <main:MainWindowModel />

app/Desktop/Main/MainWindow.axaml.cs

@@ -1,14 +1,18 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
+using System.Threading.Tasks;
 using Avalonia.Controls;
 using DHT.Desktop.Main.Pages;
+using DHT.Utils.Logging;
 using JetBrains.Annotations;
 
 namespace DHT.Desktop.Main;
 
 [SuppressMessage("ReSharper", "MemberCanBeInternal")]
 public sealed partial class MainWindow : Window {
+	private static readonly Log Log = Log.ForType<MainWindow>();
+	
 	[UsedImplicitly]
 	public MainWindow() {
 		InitializeComponent();
@@ -20,9 +24,24 @@ public sealed partial class MainWindow : Window {
 		DataContext = new MainWindowModel(this, args);
 	}
 
-	public void OnClosed(object? sender, EventArgs e) {
+	public async void OnClosing(object? sender, WindowClosingEventArgs e) {
-		if (DataContext is IDisposable disposable) {
+		e.Cancel = true;
-			disposable.Dispose();
+		Closing -= OnClosing;
+
+		try {
+			await Dispose();
+		} finally {
+			Close();
+		}
+	}
+
+	private async Task Dispose() {
+		if (DataContext is MainWindowModel model) {
+			try {
+				await model.DisposeAsync();
+			} catch (Exception ex) {
+				Log.Error("Caught exception while disposing window: " + ex);
+			}
 		}
 
 		foreach (var temporaryFile in ViewerPageModel.TemporaryFiles) {

app/Desktop/Main/MainWindowModel.cs

@@ -7,12 +7,12 @@ using Avalonia.Controls;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Screens;
 using DHT.Desktop.Server;
-using DHT.Server.Database;
+using DHT.Server;
 using DHT.Utils.Models;
 
 namespace DHT.Desktop.Main;
 
-sealed class MainWindowModel : BaseModel, IDisposable {
+sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 	private const string DefaultTitle = "Discord History Tracker";
 
 	public string Title { get; private set; } = DefaultTitle;
@@ -27,7 +27,7 @@ sealed class MainWindowModel : BaseModel, IDisposable {
 
 	private readonly Window window;
 
-	private IDatabaseFile? db;
+	private State? state;
 
 	[Obsolete("Designer")]
 	public MainWindowModel() : this(null!, Arguments.Empty) {}
@@ -78,18 +78,21 @@ sealed class MainWindowModel : BaseModel, IDisposable {
 				mainContentScreenModel.Dispose();
 			}
 
-			db?.Dispose();
+			if (state != null) {
-			db = welcomeScreenModel.Db;
+				await state.DisposeAsync();
+			}
 			
-			if (db == null) {
+			state = welcomeScreenModel.Db == null ? null : new State(welcomeScreenModel.Db);
+
+			if (state == null) {
 				Title = DefaultTitle;
 				mainContentScreenModel = null;
 				mainContentScreen = null;
 				CurrentScreen = welcomeScreen;
 			}
 			else {
-				Title = Path.GetFileName(db.Path) + " - " + DefaultTitle;
+				Title = Path.GetFileName(state.Db.Path) + " - " + DefaultTitle;
-				mainContentScreenModel = new MainContentScreenModel(window, db);
+				mainContentScreenModel = new MainContentScreenModel(window, state);
 				await mainContentScreenModel.Initialize();
 				mainContentScreenModel.DatabaseClosed += MainContentScreenModelOnDatabaseClosed;
 				mainContentScreen = new MainContentScreen { DataContext = mainContentScreenModel };
@@ -107,10 +110,14 @@ sealed class MainWindowModel : BaseModel, IDisposable {
 		welcomeScreenModel.CloseDatabase();
 	}
 
-	public void Dispose() {
+	public async ValueTask DisposeAsync() {
-		welcomeScreenModel.Dispose();
 		mainContentScreenModel?.Dispose();
-		db?.Dispose();
+
-		db = null;
+		if (state != null) {
+			await state.DisposeAsync();
+			state = null;
+		}
+		
+		welcomeScreenModel.Dispose();
 	}
 }

app/Desktop/Main/Pages/AdvancedPageModel.cs

@@ -3,7 +3,7 @@ using Avalonia.Controls;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Controls;
 using DHT.Desktop.Server;
-using DHT.Server.Database;
+using DHT.Server;
 using DHT.Utils.Models;
 
 namespace DHT.Desktop.Main.Pages;
@@ -12,14 +12,14 @@ sealed class AdvancedPageModel : BaseModel, IDisposable {
 	public ServerConfigurationPanelModel ServerConfigurationModel { get; }
 
 	private readonly Window window;
-	private readonly IDatabaseFile db;
+	private readonly State state;
 
 	[Obsolete("Designer")]
-	public AdvancedPageModel() : this(null!, DummyDatabaseFile.Instance, new ServerManager(DummyDatabaseFile.Instance)) {}
+	public AdvancedPageModel() : this(null!, State.Dummy, new ServerManager(State.Dummy)) {}
 
-	public AdvancedPageModel(Window window, IDatabaseFile db, ServerManager serverManager) {
+	public AdvancedPageModel(Window window, State state, ServerManager serverManager) {
 		this.window = window;
-		this.db = db;
+		this.state = state;
 
 		ServerConfigurationModel = new ServerConfigurationPanelModel(window, serverManager);
 	}
@@ -33,7 +33,7 @@ sealed class AdvancedPageModel : BaseModel, IDisposable {
 	}
 
 	public async void VacuumDatabase() {
-		db.Vacuum();
+		state.Db.Vacuum();
 		await Dialog.ShowOk(window, "Vacuum Database", "Done.");
 	}
 }

app/Desktop/Main/Pages/AttachmentsPage.axaml

@@ -33,7 +33,7 @@
     <StackPanel Orientation="Vertical" Spacing="20">
         <DockPanel>
             <Button Command="{Binding OnClickToggleDownload}" Content="{Binding ToggleDownloadButtonText}" IsEnabled="{Binding IsToggleDownloadButtonEnabled}" DockPanel.Dock="Left" />
-            <TextBlock Text="{Binding DownloadMessage}" Margin="10 0 0 0" VerticalAlignment="Center" DockPanel.Dock="Left" />
+            <TextBlock Text="{Binding DownloadMessage}" MinWidth="100" Margin="10 0 0 0" VerticalAlignment="Center" TextAlignment="Right" DockPanel.Dock="Left" />
             <ProgressBar Value="{Binding DownloadProgress}" IsVisible="{Binding IsDownloading}" Margin="15 0" VerticalAlignment="Center" DockPanel.Dock="Right" />
         </DockPanel>
         <controls:AttachmentFilterPanel DataContext="{Binding FilterModel}" IsEnabled="{Binding !IsDownloading, RelativeSource={RelativeSource AncestorType=pages:AttachmentsPageModel}}" />
@@ -42,8 +42,8 @@
                 <DataGrid ItemsSource="{Binding StatisticsRows}" AutoGenerateColumns="False" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserSortColumns="False" IsReadOnly="True">
                     <DataGrid.Columns>
                         <DataGridTextColumn Header="State" Binding="{Binding State}" Width="*" />
-                        <DataGridTextColumn Header="Attachments" Binding="{Binding Items, Converter={StaticResource NumberValueConverter}}" Width="*" CellStyleClasses="right" />
+                        <DataGridTextColumn Header="Attachments" Binding="{Binding Items, Mode=OneWay, Converter={StaticResource NumberValueConverter}}" Width="*" CellStyleClasses="right" />
-                        <DataGridTextColumn Header="Size" Binding="{Binding Size, Converter={StaticResource BytesValueConverter}}" Width="*" CellStyleClasses="right" />
+                        <DataGridTextColumn Header="Size" Binding="{Binding Size, Mode=OneWay, Converter={StaticResource BytesValueConverter}}" Width="*" CellStyleClasses="right" />
                     </DataGrid.Columns>
                 </DataGrid>
             </Expander>

app/Desktop/Main/Pages/AttachmentsPageModel.cs

@@ -2,9 +2,11 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Threading;
+using System.Threading.Tasks;
 using Avalonia.Threading;
 using DHT.Desktop.Common;
 using DHT.Desktop.Main.Controls;
+using DHT.Server;
 using DHT.Server.Data;
 using DHT.Server.Data.Aggregations;
 using DHT.Server.Data.Filters;
@@ -18,13 +20,14 @@ namespace DHT.Desktop.Main.Pages;
 sealed class AttachmentsPageModel : BaseModel, IDisposable {
 	private static readonly DownloadItemFilter EnqueuedItemFilter = new () {
 		IncludeStatuses = new HashSet<DownloadStatus> {
-			DownloadStatus.Enqueued
+			DownloadStatus.Enqueued,
+			DownloadStatus.Downloading
 		}
 	};
 
 	private bool isThreadDownloadButtonEnabled = true;
 
-	public string ToggleDownloadButtonText => downloadThread == null ? "Start Downloading" : "Stop Downloading";
+	public string ToggleDownloadButtonText => IsDownloading ? "Stop Downloading" : "Start Downloading";
 
 	public bool IsToggleDownloadButtonEnabled {
 		get => isThreadDownloadButtonEnabled;
@@ -32,7 +35,7 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 	}
 
 	public string DownloadMessage { get; set; } = "";
-	public double DownloadProgress => allItemsCount is null or 0 ? 0.0 : 100.0 * doneItemsCount / allItemsCount.Value;
+	public double DownloadProgress => totalItemsToDownloadCount is null or 0 ? 0.0 : 100.0 * doneItemsCount / totalItemsToDownloadCount.Value;
 
 	public AttachmentFilterPanelModel FilterModel { get; }
 
@@ -52,33 +55,34 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 		}
 	}
 
-	public bool IsDownloading => downloadThread != null;
+	public bool IsDownloading => state.Downloader.IsDownloading;
 	public bool HasFailedDownloads => statisticsFailed.Items > 0;
 
-	private readonly IDatabaseFile db;
+	private readonly State state;
 	private readonly AsyncValueComputer<DownloadStatusStatistics>.Single downloadStatisticsComputer;
-	private BackgroundDownloadThread? downloadThread;
 
 	private int doneItemsCount;
-	private int? allItemsCount;
+	private int initialFinishedCount;
+	private int? totalItemsToDownloadCount;
 
-	public AttachmentsPageModel() : this(DummyDatabaseFile.Instance) {}
+	public AttachmentsPageModel() : this(State.Dummy) {}
 
-	public AttachmentsPageModel(IDatabaseFile db) {
+	public AttachmentsPageModel(State state) {
-		this.db = db;
+		this.state = state;
-		this.FilterModel = new AttachmentFilterPanelModel(db);
 		
-		this.downloadStatisticsComputer = AsyncValueComputer<DownloadStatusStatistics>.WithResultProcessor(UpdateStatistics).WithOutdatedResults().BuildWithComputer(db.GetDownloadStatusStatistics);
+		FilterModel = new AttachmentFilterPanelModel(state);
-		this.downloadStatisticsComputer.Recompute();
 
-		db.Statistics.PropertyChanged += OnDbStatisticsChanged;
+		downloadStatisticsComputer = AsyncValueComputer<DownloadStatusStatistics>.WithResultProcessor(UpdateStatistics).WithOutdatedResults().BuildWithComputer(state.Db.GetDownloadStatusStatistics);
+		downloadStatisticsComputer.Recompute();
+
+		state.Db.Statistics.PropertyChanged += OnDbStatisticsChanged;
+		state.Downloader.OnItemFinished += DownloaderOnOnItemFinished;
 	}
 
 	public void Dispose() {
-		db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
+		state.Db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
-
+		state.Downloader.OnItemFinished -= DownloaderOnOnItemFinished;
 		FilterModel.Dispose();
-		DisposeDownloadThread();
 	}
 
 	private void OnDbStatisticsChanged(object? sender, PropertyChangedEventArgs e) {
@@ -98,7 +102,7 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 	private void EnqueueDownloadItems() {
 		var filter = FilterModel.CreateFilter();
 		filter.DownloadItemRule = AttachmentFilter.DownloadItemRules.OnlyNotPresent;
-		db.EnqueueDownloadItems(filter);
+		state.Db.EnqueueDownloadItems(filter);
 
 		downloadStatisticsComputer.Recompute();
 	}
@@ -124,46 +128,43 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 			OnPropertyChanged(nameof(HasFailedDownloads));
 		}
 
-		allItemsCount = doneItemsCount + statisticsEnqueued.Items;
+		totalItemsToDownloadCount = statisticsEnqueued.Items + statisticsDownloaded.Items + statisticsFailed.Items - initialFinishedCount;
 		UpdateDownloadMessage();
 	}
 
 	private void UpdateDownloadMessage() {
-		DownloadMessage = IsDownloading ? doneItemsCount.Format() + " / " + (allItemsCount?.Format() ?? "?") : "";
+		DownloadMessage = IsDownloading ? doneItemsCount.Format() + " / " + (totalItemsToDownloadCount?.Format() ?? "?") : "";
 
 		OnPropertyChanged(nameof(DownloadMessage));
 		OnPropertyChanged(nameof(DownloadProgress));
 	}
 
-	private void DownloadThreadOnOnItemFinished(object? sender, DownloadItem e) {
+	private void DownloaderOnOnItemFinished(object? sender, DownloadItem e) {
 		Interlocked.Increment(ref doneItemsCount);
 		
 		Dispatcher.UIThread.Invoke(UpdateDownloadMessage);
 		downloadStatisticsComputer.Recompute();
 	}
 
-	private void DownloadThreadOnOnServerStopped(object? sender, EventArgs e) {
+	public async Task OnClickToggleDownload() {
+		if (IsDownloading) {
+			IsToggleDownloadButtonEnabled = false;
+			await state.Downloader.Stop();
 			downloadStatisticsComputer.Recompute();
 			IsToggleDownloadButtonEnabled = true;
-	}
 
-	public void OnClickToggleDownload() {
+			state.Db.RemoveDownloadItems(EnqueuedItemFilter, FilterRemovalMode.RemoveMatching);
-		if (downloadThread == null) {
-			EnqueueDownloadItems();
-			downloadThread = new BackgroundDownloadThread(db);
-			downloadThread.OnItemFinished += DownloadThreadOnOnItemFinished;
-			downloadThread.OnServerStopped += DownloadThreadOnOnServerStopped;
-		}
-		else {
-			IsToggleDownloadButtonEnabled = false;
-			DisposeDownloadThread();
-
-			db.RemoveDownloadItems(EnqueuedItemFilter, FilterRemovalMode.RemoveMatching);
 
 			doneItemsCount = 0;
-			allItemsCount = null;
+			initialFinishedCount = 0;
+			totalItemsToDownloadCount = null;
 			UpdateDownloadMessage();
 		}
+		else {
+			initialFinishedCount = statisticsDownloaded.Items + statisticsFailed.Items;
+			await state.Downloader.Start();
+			EnqueueDownloadItems();
+		}
 
 		OnPropertyChanged(nameof(ToggleDownloadButtonText));
 		OnPropertyChanged(nameof(IsDownloading));
@@ -173,26 +174,18 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 		var allExceptFailedFilter = new DownloadItemFilter {
 			IncludeStatuses = new HashSet<DownloadStatus> {
 				DownloadStatus.Enqueued,
+				DownloadStatus.Downloading,
 				DownloadStatus.Success
 			}
 		};
 
-		db.RemoveDownloadItems(allExceptFailedFilter, FilterRemovalMode.KeepMatching);
+		state.Db.RemoveDownloadItems(allExceptFailedFilter, FilterRemovalMode.KeepMatching);
 
 		if (IsDownloading) {
 			EnqueueDownloadItems();
 		}
 	}
 
-	private void DisposeDownloadThread() {
-		if (downloadThread != null) {
-			downloadThread.OnItemFinished -= DownloadThreadOnOnItemFinished;
-			downloadThread.StopThread();
-		}
-
-		downloadThread = null;
-	}
-
 	public sealed class StatisticsRow {
 		public string State { get; }
 		public int Items { get; set; }

app/Desktop/Main/Pages/DatabasePageModel.cs

@@ -14,6 +14,7 @@ using DHT.Desktop.Dialogs.File;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Dialogs.Progress;
 using DHT.Desktop.Dialogs.TextBox;
+using DHT.Server;
 using DHT.Server.Data;
 using DHT.Server.Database;
 using DHT.Server.Database.Import;
@@ -33,11 +34,11 @@ sealed class DatabasePageModel : BaseModel {
 	private readonly Window window;
 
 	[Obsolete("Designer")]
-	public DatabasePageModel() : this(null!, DummyDatabaseFile.Instance) {}
+	public DatabasePageModel() : this(null!, State.Dummy) {}
 
-	public DatabasePageModel(Window window, IDatabaseFile db) {
+	public DatabasePageModel(Window window, State state) {
 		this.window = window;
-		this.Db = db;
+		this.Db = state.Db;
 	}
 
 	public async void OpenDatabaseFolder() {

app/Desktop/Main/Pages/DebugPageModel.cs

@@ -6,8 +6,8 @@ using System.Threading.Tasks;
 using Avalonia.Controls;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Dialogs.Progress;
+using DHT.Server;
 using DHT.Server.Data;
-using DHT.Server.Database;
 using DHT.Server.Service;
 using DHT.Utils.Models;
 
@@ -18,14 +18,14 @@ namespace DHT.Desktop.Main.Pages {
 		public string GenerateMessages { get; set; } = "0";
 
 		private readonly Window window;
-		private readonly IDatabaseFile db;
+		private readonly State state;
 
 		[Obsolete("Designer")]
-		public DebugPageModel() : this(null!, DummyDatabaseFile.Instance) {}
+		public DebugPageModel() : this(null!, State.Dummy) {}
 
-		public DebugPageModel(Window window, IDatabaseFile db) {
+		public DebugPageModel(Window window, State state) {
 			this.window = window;
-			this.db = db;
+			this.state = state;
 		}
 
 		public async void OnClickAddRandomDataToDatabase() {
@@ -83,11 +83,11 @@ namespace DHT.Desktop.Main.Pages {
 				Discriminator = rand.Next(0, 9999).ToString(),
 			}).ToArray();
 
-			db.AddServer(server);
+			state.Db.AddServer(server);
-			db.AddUsers(users);
+			state.Db.AddUsers(users);
 
 			foreach (var channel in channels) {
-				db.AddChannel(channel);
+				state.Db.AddChannel(channel);
 			}
 
 			var now = DateTimeOffset.Now;
@@ -117,7 +117,7 @@ namespace DHT.Desktop.Main.Pages {
 					};
 				}).ToArray();
 
-				db.AddMessages(messages);
+				state.Db.AddMessages(messages);
 
 				messageCount -= BatchSize;
 				await callback.Update("Adding messages in batches of " + BatchSize, ++batchIndex, batchCount);

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -13,8 +13,8 @@ using DHT.Desktop.Dialogs.File;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Controls;
 using DHT.Desktop.Server;
+using DHT.Server;
 using DHT.Server.Data.Filters;
-using DHT.Server.Database;
 using DHT.Server.Database.Export;
 using DHT.Server.Database.Export.Strategy;
 using DHT.Utils.Models;
@@ -38,16 +38,16 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 	public MessageFilterPanelModel FilterModel { get; }
 
 	private readonly Window window;
-	private readonly IDatabaseFile db;
+	private readonly State state;
 
 	[Obsolete("Designer")]
-	public ViewerPageModel() : this(null!, DummyDatabaseFile.Instance) {}
+	public ViewerPageModel() : this(null!, State.Dummy) {}
 
-	public ViewerPageModel(Window window, IDatabaseFile db) {
+	public ViewerPageModel(Window window, State state) {
 		this.window = window;
-		this.db = db;
+		this.state = state;
 
-		FilterModel = new MessageFilterPanelModel(window, db, "Will export");
+		FilterModel = new MessageFilterPanelModel(window, state, "Will export");
 		FilterModel.FilterPropertyChanged += OnFilterPropertyChanged;
 	}
 
@@ -72,7 +72,7 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 		string jsonTempFile = path + ".tmp";
 
 		await using (var jsonStream = new FileStream(jsonTempFile, FileMode.Create, FileAccess.ReadWrite, FileShare.Read)) {
-			await ViewerJsonExport.Generate(jsonStream, strategy, db, FilterModel.CreateFilter());
+			await ViewerJsonExport.Generate(jsonStream, strategy, state.Db, FilterModel.CreateFilter());
 
 			char[] jsonBuffer = new char[Math.Min(32768, jsonStream.Position)];
 			jsonStream.Position = 0;
@@ -98,7 +98,7 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 
 	public async void OnClickOpenViewer() {
 		string rootPath = Path.Combine(Path.GetTempPath(), "DiscordHistoryTracker");
-		string filenameBase = Path.GetFileNameWithoutExtension(db.Path) + "-" + DateTime.Now.ToString("yyyy-MM-dd");
+		string filenameBase = Path.GetFileNameWithoutExtension(state.Db.Path) + "-" + DateTime.Now.ToString("yyyy-MM-dd");
 		string fullPath = Path.Combine(rootPath, filenameBase + ".html");
 		int counter = 0;
 
@@ -123,8 +123,8 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 		string? path = await window.StorageProvider.SaveFile(new FilePickerSaveOptions {
 			Title = "Save Viewer",
 			FileTypeChoices = ViewerFileTypes,
-			SuggestedFileName = Path.GetFileNameWithoutExtension(db.Path) + ".html",
+			SuggestedFileName = Path.GetFileNameWithoutExtension(state.Db.Path) + ".html",
-			SuggestedStartLocation = await FileDialogs.GetSuggestedStartLocation(window, Path.GetDirectoryName(db.Path)),
+			SuggestedStartLocation = await FileDialogs.GetSuggestedStartLocation(window, Path.GetDirectoryName(state.Db.Path)),
 		});
 
 		if (path != null) {
@@ -136,13 +136,13 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 		var filter = FilterModel.CreateFilter();
 
 		if (DatabaseToolFilterModeKeep) {
-			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Keep Matching Messages in This Database", 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", state.Db.CountMessages(filter).Pluralize("message") + " will be kept, and the rest will be removed from this database. This action cannot be undone. Proceed?")) {
-				db.RemoveMessages(filter, FilterRemovalMode.KeepMatching);
+				state.Db.RemoveMessages(filter, FilterRemovalMode.KeepMatching);
 			}
 		}
 		else if (DatabaseToolFilterModeRemove) {
-			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Remove Matching Messages in This Database", 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", state.Db.CountMessages(filter).Pluralize("message") + " will be removed from this database. This action cannot be undone. Proceed?")) {
-				db.RemoveMessages(filter, FilterRemovalMode.RemoveMatching);
+				state.Db.RemoveMessages(filter, FilterRemovalMode.RemoveMatching);
 			}
 		}
 	}

app/Desktop/Main/Screens/MainContentScreenModel.cs

@@ -5,7 +5,7 @@ using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Controls;
 using DHT.Desktop.Main.Pages;
 using DHT.Desktop.Server;
-using DHT.Server.Database;
+using DHT.Server;
 using DHT.Server.Service;
 using DHT.Utils.Logging;
 
@@ -53,37 +53,37 @@ sealed class MainContentScreenModel : IDisposable {
 	private readonly ServerManager serverManager;
 
 	[Obsolete("Designer")]
-	public MainContentScreenModel() : this(null!, DummyDatabaseFile.Instance) {}
+	public MainContentScreenModel() : this(null!, State.Dummy) {}
 
-	public MainContentScreenModel(Window window, IDatabaseFile db) {
+	public MainContentScreenModel(Window window, State state) {
 		this.window = window;
-		this.serverManager = new ServerManager(db);
+		this.serverManager = new ServerManager(state);
 
 		ServerLauncher.ServerManagementExceptionCaught += ServerLauncherOnServerManagementExceptionCaught;
 
-		DatabasePageModel = new DatabasePageModel(window, db);
+		DatabasePageModel = new DatabasePageModel(window, state);
 		DatabasePage = new DatabasePage { DataContext = DatabasePageModel };
 
 		TrackingPageModel = new TrackingPageModel(window);
 		TrackingPage = new TrackingPage { DataContext = TrackingPageModel };
 
-		AttachmentsPageModel = new AttachmentsPageModel(db);
+		AttachmentsPageModel = new AttachmentsPageModel(state);
 		AttachmentsPage = new AttachmentsPage { DataContext = AttachmentsPageModel };
 
-		ViewerPageModel = new ViewerPageModel(window, db);
+		ViewerPageModel = new ViewerPageModel(window, state);
 		ViewerPage = new ViewerPage { DataContext = ViewerPageModel };
 
-		AdvancedPageModel = new AdvancedPageModel(window, db, serverManager);
+		AdvancedPageModel = new AdvancedPageModel(window, state, serverManager);
 		AdvancedPage = new AdvancedPage { DataContext = AdvancedPageModel };
 
 		#if DEBUG
-		DebugPageModel = new DebugPageModel(window, db);
+		DebugPageModel = new DebugPageModel(window, state);
 		DebugPage = new DebugPage { DataContext = DebugPageModel };
 		#else
 		DebugPage = null;
 		#endif
 
-		StatusBarModel = new StatusBarModel(db.Statistics);
+		StatusBarModel = new StatusBarModel(state.Db.Statistics);
 
 		AdvancedPageModel.ServerConfigurationModel.ServerStatusChanged += OnServerStatusChanged;
 		DatabaseClosed += OnDatabaseClosed;

app/Desktop/Server/ServerManager.cs

@@ -1,5 +1,5 @@
 using System;
-using DHT.Server.Database;
+using DHT.Server;
 using DHT.Server.Service;
 
 namespace DHT.Desktop.Server;
@@ -12,10 +12,10 @@ sealed class ServerManager : IDisposable {
 
 	public bool IsRunning => ServerLauncher.IsRunning;
 
-	private readonly IDatabaseFile db;
+	private readonly State state;
 
-	public ServerManager(IDatabaseFile db) {
+	public ServerManager(State state) {
-		if (db != DummyDatabaseFile.Instance) {
+		if (state != State.Dummy) {
 			if (instance != null) {
 				throw new InvalidOperationException("Only one instance of ServerManager can exist at the same time!");
 			}
@@ -23,11 +23,11 @@ sealed class ServerManager : IDisposable {
 			instance = this;
 		}
 
-		this.db = db;
+		this.state = state;
 	}
 
 	public void Launch() {
-		ServerLauncher.Relaunch(Port, Token, db);
+		ServerLauncher.Relaunch(Port, Token, state.Db);
 	}
 
 	public void Relaunch(ushort port, string token) {

app/Server/Data/DownloadStatus.cs

@@ -8,5 +8,6 @@ namespace DHT.Server.Data;
 public enum DownloadStatus {
 	Enqueued = 0,
 	GenericError = 1,
+	Downloading = 2,
 	Success = HttpStatusCode.OK
 }

app/Server/Database/DummyDatabaseFile.cs

@@ -74,7 +74,7 @@ public sealed class DummyDatabaseFile : IDatabaseFile {
 
 	public void EnqueueDownloadItems(AttachmentFilter? filter = null) {}
 
-	public List<DownloadItem> GetEnqueuedDownloadItems(int count) {
+	public List<DownloadItem> PullEnqueuedDownloadItems(int count) {
 		return new();
 	}
 

app/Server/Database/IDatabaseFile.cs

@@ -35,7 +35,7 @@ public interface IDatabaseFile : IDisposable {
 	DownloadedAttachment? GetDownloadedAttachment(string url);
 
 	void EnqueueDownloadItems(AttachmentFilter? filter = null);
-	List<DownloadItem> GetEnqueuedDownloadItems(int count);
+	List<DownloadItem> PullEnqueuedDownloadItems(int count);
 	void RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode);
 	DownloadStatusStatistics GetDownloadStatusStatistics();
 

app/Server/Database/Sqlite/Schema.cs

@@ -174,8 +174,8 @@ sealed class Schema {
 		int processedUrls = -1;
 
 		await using (var updateCmd = conn.Command("UPDATE attachments SET download_url = url, url = :normalized_url WHERE attachment_id = :attachment_id")) {
-			updateCmd.Parameters.Add(":attachment_id", SqliteType.Integer);
+			updateCmd.Add(":attachment_id", SqliteType.Integer);
-			updateCmd.Parameters.Add(":normalized_url", SqliteType.Text);
+			updateCmd.Add(":normalized_url", SqliteType.Text);
 				
 			foreach (var (attachmentId, normalizedUrl) in normalizedUrls) {
 				if (++processedUrls % 1000 == 0) {
@@ -235,8 +235,8 @@ sealed class Schema {
 		tx = conn.BeginTransaction();
 		
 		await using (var updateCmd = conn.Command("UPDATE downloads SET download_url = :download_url, url = :normalized_url WHERE url = :download_url")) {
-			updateCmd.Parameters.Add(":normalized_url", SqliteType.Text);
+			updateCmd.Add(":normalized_url", SqliteType.Text);
-			updateCmd.Parameters.Add(":download_url", SqliteType.Text);
+			updateCmd.Add(":download_url", SqliteType.Text);
 			
 			foreach (var (normalizedUrl, downloadUrl) in normalizedUrlsToOriginalUrls) {
 				if (++processedUrls % 100 == 0) {

app/Server/Database/Sqlite/SqliteDatabaseFile.cs

@@ -522,25 +522,42 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 		cmd.ExecuteNonQuery();
 	}
 
-	public List<DownloadItem> GetEnqueuedDownloadItems(int count) {
+	public List<DownloadItem> PullEnqueuedDownloadItems(int count) {
-		var list = new List<DownloadItem>();
+		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");
+		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()) {
-			list.Add(new DownloadItem {
+				found.Add(new DownloadItem {
 					NormalizedUrl = reader.GetString(0),
 					DownloadUrl = reader.GetString(1),
 					Size = reader.GetUint64(2),
 				});
 			}
+		}
 
-		return list;
+		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) {
@@ -562,15 +579,16 @@ public sealed class SqliteDatabaseFile : IDatabaseFile {
 		static void LoadSuccessStatistics(ISqliteConnection conn, DownloadStatusStatistics result) {
 			using var cmd = conn.Command("""
 			                             SELECT
-			                             IFNULL(SUM(CASE WHEN status = :enqueued THEN 1 ELSE 0 END), 0),
+			                             IFNULL(SUM(CASE WHEN status IN (:enqueued, :downloading) THEN 1 ELSE 0 END), 0),
-			                             IFNULL(SUM(CASE WHEN status = :enqueued THEN size 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 != :enqueued AND status != :success THEN 1 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 != :enqueued AND status != :success THEN size 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();

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

@@ -62,6 +62,10 @@ static class SqliteExtensions {
 		}
 	}
 
+	public static void Add(this SqliteCommand cmd, string key, SqliteType type) {
+		cmd.Parameters.Add(key, type);
+	}
+
 	public static void AddAndSet(this SqliteCommand cmd, string key, SqliteType type, object? value) {
 		cmd.Parameters.Add(key, type).Value = value ?? DBNull.Value;
 	}

app/Server/Download/BackgroundDownloadThread.cs

@@ -1,130 +0,0 @@
-using System;
-using System.Collections.Concurrent;
-using System.Net.Http;
-using System.Threading;
-using DHT.Server.Database;
-using DHT.Utils.Logging;
-using DHT.Utils.Models;
-
-namespace DHT.Server.Download;
-
-public sealed class BackgroundDownloadThread : BaseModel {
-	private static readonly Log Log = Log.ForType<BackgroundDownloadThread>();
-
-	public event EventHandler<DownloadItem>? OnItemFinished {
-		add => parameters.OnItemFinished += value;
-		remove => parameters.OnItemFinished -= value;
-	}
-
-	public event EventHandler? OnServerStopped {
-		add => parameters.OnServerStopped += value;
-		remove => parameters.OnServerStopped -= value;
-	}
-
-	private readonly CancellationTokenSource cancellationTokenSource;
-	private readonly ThreadInstance.Parameters parameters;
-
-	public BackgroundDownloadThread(IDatabaseFile db) {
-		this.cancellationTokenSource = new CancellationTokenSource();
-		this.parameters = new ThreadInstance.Parameters(db, cancellationTokenSource);
-
-		var thread = new Thread(new ThreadInstance().Work) {
-			Name = "DHT download thread"
-		};
-
-		thread.Start(parameters);
-	}
-
-	public void StopThread() {
-		try {
-			cancellationTokenSource.Cancel();
-		} catch (ObjectDisposedException) {
-			Log.Warn("Attempted to stop background download thread after the cancellation token has been disposed.");
-		}
-	}
-
-	private sealed class ThreadInstance {
-		private const int QueueSize = 32;
-
-		public sealed class Parameters {
-			public event EventHandler<DownloadItem>? OnItemFinished;
-			public event EventHandler? OnServerStopped;
-
-			public IDatabaseFile Db { get; }
-			public CancellationTokenSource CancellationTokenSource { get; }
-
-			public Parameters(IDatabaseFile db, CancellationTokenSource cancellationTokenSource) {
-				Db = db;
-				CancellationTokenSource = cancellationTokenSource;
-			}
-
-			public void FireOnItemFinished(DownloadItem item) {
-				OnItemFinished?.Invoke(null, item);
-			}
-
-			public void FireOnServerStopped() {
-				OnServerStopped?.Invoke(null, EventArgs.Empty);
-			}
-		}
-
-		private readonly HttpClient client = new ();
-
-		public ThreadInstance() {
-			client.DefaultRequestHeaders.UserAgent.ParseAdd("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.51 Safari/537.36");
-		}
-
-		public async void Work(object? obj) {
-			var parameters = (Parameters) obj!;
-
-			var cancellationTokenSource = parameters.CancellationTokenSource;
-			var cancellationToken = cancellationTokenSource.Token;
-
-			var db = parameters.Db;
-			var queue = new ConcurrentQueue<DownloadItem>();
-
-			try {
-				while (!cancellationToken.IsCancellationRequested) {
-					FillQueue(db, queue, cancellationToken);
-
-					while (!cancellationToken.IsCancellationRequested && queue.TryDequeue(out var item)) {
-						var downloadUrl = item.DownloadUrl;
-						Log.Debug("Downloading " + downloadUrl + "...");
-
-						try {
-							db.AddDownload(Data.Download.NewSuccess(item, await client.GetByteArrayAsync(downloadUrl, cancellationToken)));
-						} catch (HttpRequestException e) {
-							db.AddDownload(Data.Download.NewFailure(item, e.StatusCode, item.Size));
-							Log.Error(e);
-						} catch (Exception e) {
-							db.AddDownload(Data.Download.NewFailure(item, null, item.Size));
-							Log.Error(e);
-						} finally {
-							parameters.FireOnItemFinished(item);
-						}
-					}
-				}
-			} catch (OperationCanceledException) {
-				//
-			} catch (ObjectDisposedException) {
-				//
-			} finally {
-				cancellationTokenSource.Dispose();
-				parameters.FireOnServerStopped();
-			}
-		}
-
-		private static void FillQueue(IDatabaseFile db, ConcurrentQueue<DownloadItem> queue, CancellationToken cancellationToken) {
-			while (!cancellationToken.IsCancellationRequested && queue.IsEmpty) {
-				var newItems = db.GetEnqueuedDownloadItems(QueueSize);
-				if (newItems.Count == 0) {
-					Thread.Sleep(TimeSpan.FromMilliseconds(50));
-				}
-				else {
-					foreach (var item in newItems) {
-						queue.Enqueue(item);
-					}
-				}
-			}
-		}
-	}
-}

app/Server/Download/Downloader.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using DHT.Server.Database;
+
+namespace DHT.Server.Download;
+
+public sealed class Downloader {
+	private DownloaderTask? current;
+	public bool IsDownloading => current != null;
+	
+	public event EventHandler<DownloadItem>? OnItemFinished;
+	
+	private readonly IDatabaseFile db;
+	private readonly SemaphoreSlim semaphore = new (1, 1);
+	
+	internal Downloader(IDatabaseFile db) {
+		this.db = db;
+	}
+
+	public async Task Start() {
+		await semaphore.WaitAsync();
+		try {
+			if (current == null) {
+				current = new DownloaderTask(db);
+				current.OnItemFinished += DelegateOnItemFinished;
+			}
+		} finally {
+			semaphore.Release();
+		}
+	}
+
+	public async Task Stop() {
+		await semaphore.WaitAsync();
+		try {
+			if (current != null) {
+				await current.Stop();
+				current.OnItemFinished -= DelegateOnItemFinished;
+				current = null;
+			}
+		} finally {
+			semaphore.Release();
+		}
+	}
+
+	private void DelegateOnItemFinished(object? sender, DownloadItem e) {
+		OnItemFinished?.Invoke(this, e);
+	}
+}

app/Server/Download/DownloaderTask.cs

@@ -0,0 +1,107 @@
+using System;
+using System.Linq;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+using DHT.Server.Database;
+using DHT.Utils.Logging;
+using DHT.Utils.Models;
+using DHT.Utils.Tasks;
+
+namespace DHT.Server.Download;
+
+sealed class DownloaderTask : BaseModel {
+	private static readonly Log Log = Log.ForType<DownloaderTask>();
+
+	private const int DownloadTasks = 4;
+	private const int QueueSize = 25;
+	private const string UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36";
+
+	internal event EventHandler<DownloadItem>? OnItemFinished;
+
+	private readonly Channel<DownloadItem> downloadQueue = Channel.CreateBounded<DownloadItem>(new BoundedChannelOptions(QueueSize) {
+		SingleReader = false,
+		SingleWriter = true,
+		AllowSynchronousContinuations = false,
+		FullMode = BoundedChannelFullMode.Wait
+	});
+
+	private readonly CancellationTokenSource cancellationTokenSource = new ();
+	private readonly CancellationToken cancellationToken;
+
+	private readonly IDatabaseFile db;
+	private readonly Task queueWriterTask;
+	private readonly Task[] downloadTasks;
+
+	internal DownloaderTask(IDatabaseFile db) {
+		this.cancellationToken = cancellationTokenSource.Token;
+		this.db = db;
+		this.queueWriterTask = Task.Run(RunQueueWriterTask);
+		this.downloadTasks = Enumerable.Range(1, DownloadTasks).Select(taskIndex => Task.Run(() => RunDownloadTask(taskIndex))).ToArray();
+	}
+
+	private async Task RunQueueWriterTask() {
+		while (await downloadQueue.Writer.WaitToWriteAsync(cancellationToken)) {
+			var newItems = db.PullEnqueuedDownloadItems(QueueSize);
+			if (newItems.Count == 0) {
+				await Task.Delay(TimeSpan.FromMilliseconds(50), cancellationToken);
+				continue;
+			}
+
+			foreach (var newItem in newItems) {
+				await downloadQueue.Writer.WriteAsync(newItem, cancellationToken);
+			}
+		}
+	}
+
+	private async Task RunDownloadTask(int taskIndex) {
+		var log = Log.ForType<DownloaderTask>("Task " + taskIndex);
+
+		var client = new HttpClient();
+		client.DefaultRequestHeaders.UserAgent.ParseAdd(UserAgent);
+		client.Timeout = TimeSpan.FromSeconds(30);
+
+		while (!cancellationToken.IsCancellationRequested) {
+			var item = await downloadQueue.Reader.ReadAsync(cancellationToken);
+			log.Debug("Downloading " + item.DownloadUrl + "...");
+
+			try {
+				var downloadedBytes = await client.GetByteArrayAsync(item.DownloadUrl, cancellationToken);
+				db.AddDownload(Data.Download.NewSuccess(item, downloadedBytes));
+			} catch (OperationCanceledException) {
+				// Ignore.
+			} catch (HttpRequestException e) {
+				db.AddDownload(Data.Download.NewFailure(item, e.StatusCode, item.Size));
+				log.Error(e);
+			} catch (Exception e) {
+				db.AddDownload(Data.Download.NewFailure(item, null, item.Size));
+				log.Error(e);
+			} finally {
+				try {
+					OnItemFinished?.Invoke(this, item);
+				} catch (Exception e) {
+					log.Error("Caught exception in event handler: " + e);
+				}
+			}
+		}
+	}
+
+	internal async Task Stop() {
+		try {
+			await cancellationTokenSource.CancelAsync();
+		} catch (Exception) {
+			Log.Warn("Attempted to stop background download twice.");
+			return;
+		}
+
+		downloadQueue.Writer.Complete();
+
+		try {
+			await queueWriterTask.WaitIgnoringCancellation();
+			await Task.WhenAll(downloadTasks).WaitIgnoringCancellation();
+		} finally {
+			cancellationTokenSource.Dispose();
+		}
+	}
+}

app/Server/State.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Threading.Tasks;
+using DHT.Server.Database;
+using DHT.Server.Download;
+
+namespace DHT.Server;
+
+public sealed class State : IAsyncDisposable {
+	public static State Dummy { get; } = new (DummyDatabaseFile.Instance);
+	
+	public IDatabaseFile Db { get; }
+	public Downloader Downloader { get; }
+
+	public State(IDatabaseFile db) {
+		Db = db;
+		Downloader = new Downloader(db);
+	}
+
+	public async ValueTask DisposeAsync() {
+		await Downloader.Stop();
+		Db.Dispose();
+	}
+}

app/Utils/Tasks/TaskExtensions.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Tasks;
+
+public static class TaskExtensions {
+	public static async Task WaitIgnoringCancellation(this Task task) {
+		try {
+			await task;
+		} catch (OperationCanceledException) {}
+	}
+}