Convert attachment download events to reactive

app/Desktop/Desktop.csproj

@@ -21,6 +21,7 @@
     <PackageReference Include="Avalonia.Desktop" Version="11.0.6" />
     <PackageReference Include="Avalonia.Diagnostics" Version="11.0.6" Condition=" '$(Configuration)' == 'Debug' " />
     <PackageReference Include="Avalonia.Fonts.Inter" Version="11.0.6" />
+    <PackageReference Include="Avalonia.ReactiveUI" Version="11.0.6" />
     <PackageReference Include="Avalonia.Themes.Fluent" Version="11.0.6" />
   </ItemGroup>
   

app/Desktop/Main/Controls/ServerConfigurationPanelModel.cs

@@ -1,14 +1,19 @@
 using System;
+using System.Threading.Tasks;
 using Avalonia.Controls;
+using Avalonia.Threading;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Server;
 using DHT.Server;
 using DHT.Server.Service;
+using DHT.Utils.Logging;
 using DHT.Utils.Models;
 
 namespace DHT.Desktop.Main.Controls;
 
 sealed class ServerConfigurationPanelModel : BaseModel, IDisposable {
+	private static readonly Log Log = Log.ForType<ServerConfigurationPanelModel>();
+	
 	private string inputPort;
 
 	public string InputPort {
@@ -29,7 +34,7 @@ sealed class ServerConfigurationPanelModel : BaseModel, IDisposable {
 		}
 	}
 
-	public bool HasMadeChanges => ServerManager.Port.ToString() != InputPort || ServerManager.Token != InputToken;
+	public bool HasMadeChanges => ServerConfiguration.Port.ToString() != InputPort || ServerConfiguration.Token != InputToken;
 
 	private bool isToggleServerButtonEnabled = true;
 
@@ -38,59 +43,69 @@ sealed class ServerConfigurationPanelModel : BaseModel, IDisposable {
 		set => Change(ref isToggleServerButtonEnabled, value);
 	}
 
-	public string ToggleServerButtonText => serverManager.IsRunning ? "Stop Server" : "Start Server";
-
-	public event EventHandler<StatusBarModel.Status>? ServerStatusChanged;
+	public string ToggleServerButtonText => server.IsRunning ? "Stop Server" : "Start Server";
 
 	private readonly Window window;
-	private readonly ServerManager serverManager;
+	private readonly ServerManager server;
 
 	[Obsolete("Designer")]
-	public ServerConfigurationPanelModel() : this(null!, new ServerManager(State.Dummy)) {}
+	public ServerConfigurationPanelModel() : this(null!, State.Dummy) {}
 
-	public ServerConfigurationPanelModel(Window window, ServerManager serverManager) {
+	public ServerConfigurationPanelModel(Window window, State state) {
 		this.window = window;
-		this.serverManager = serverManager;
-		this.inputPort = ServerManager.Port.ToString();
-		this.inputToken = ServerManager.Token;
-	}
+		this.server = state.Server;
+		this.inputPort = ServerConfiguration.Port.ToString();
+		this.inputToken = ServerConfiguration.Token;
 		
-	public void Initialize() {
-		ServerLauncher.ServerStatusChanged += ServerLauncherOnServerStatusChanged;
+		server.StatusChanged += OnServerStatusChanged;
 	}
 
 	public void Dispose() {
-		ServerLauncher.ServerStatusChanged -= ServerLauncherOnServerStatusChanged;
+		server.StatusChanged -= OnServerStatusChanged;
 	}
 
-	private void ServerLauncherOnServerStatusChanged(object? sender, EventArgs e) {
-		ServerStatusChanged?.Invoke(this, serverManager.IsRunning ? StatusBarModel.Status.Ready : StatusBarModel.Status.Stopped);
+	private void OnServerStatusChanged(object? sender, ServerManager.Status e) {
+		Dispatcher.UIThread.InvokeAsync(UpdateServerStatus);
+	}
+
+	private void UpdateServerStatus() {
 		OnPropertyChanged(nameof(ToggleServerButtonText));
+	}
+
+	private async Task StartServer() {
+		IsToggleServerButtonEnabled = false;
+		
+		try {
+			await server.Start(ServerConfiguration.Port, ServerConfiguration.Token);
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, "Internal Server Error", e.Message);
+		}
+		
+		UpdateServerStatus();
 		IsToggleServerButtonEnabled = true;
 	}
 
-	private void BeforeServerStart() {
+	private async Task StopServer() {
 		IsToggleServerButtonEnabled = false;
-		ServerStatusChanged?.Invoke(this, StatusBarModel.Status.Starting);
+		
+		try {
+			await server.Stop();
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, "Internal Server Error", e.Message);
 		}
 		
-	private void StartServer() {
-		BeforeServerStart();
-		serverManager.Launch();
+		UpdateServerStatus();
+		IsToggleServerButtonEnabled = true;
 	}
 
-	private void StopServer() {
-		IsToggleServerButtonEnabled = false;
-		ServerStatusChanged?.Invoke(this, StatusBarModel.Status.Stopping);
-		serverManager.Stop();
-	}
-
-	public void OnClickToggleServerButton() {
-		if (serverManager.IsRunning) {
-			StopServer();
+	public async Task OnClickToggleServerButton() {
+		if (server.IsRunning) {
+			await StopServer();
 		}
 		else {
-			StartServer();
+			await StartServer();
 		}
 	}
 
@@ -98,19 +113,21 @@ sealed class ServerConfigurationPanelModel : BaseModel, IDisposable {
 		InputToken = ServerUtils.GenerateRandomToken(20);
 	}
 
-	public async void OnClickApplyChanges() {
+	public async Task OnClickApplyChanges() {
 		if (!ushort.TryParse(InputPort, out ushort port)) {
 			await Dialog.ShowOk(window, "Invalid Port", "Port must be a number between 0 and 65535.");
 			return;
 		}
 
-		BeforeServerStart();
-		serverManager.Relaunch(port, InputToken);
+		ServerConfiguration.Port = port;
+		ServerConfiguration.Token = inputToken;
+		await StartServer();
+		
 		OnPropertyChanged(nameof(HasMadeChanges));
 	}
 
 	public void OnClickCancelChanges() {
-		InputPort = ServerManager.Port.ToString();
-		InputToken = ServerManager.Token;
+		InputPort = ServerConfiguration.Port.ToString();
+		InputToken = ServerConfiguration.Token;
 	}
 }

app/Desktop/Main/Controls/StatusBar.axaml

@@ -40,7 +40,7 @@
     <StackPanel Orientation="Horizontal" Margin="6 3">
         <StackPanel Orientation="Vertical" Width="65">
             <TextBlock Classes="label">Status</TextBlock>
-            <TextBlock FontSize="12" Margin="0 3 0 0" Text="{Binding StatusText}" />
+            <TextBlock FontSize="12" Margin="0 3 0 0" Text="{Binding ServerStatusText}" />
         </StackPanel>
         <Rectangle />
         <StackPanel Orientation="Vertical">

app/Desktop/Main/Controls/StatusBarModel.cs

@@ -1,45 +1,46 @@
 using System;
+using Avalonia.Threading;
+using DHT.Server;
 using DHT.Server.Database;
+using DHT.Server.Service;
 using DHT.Utils.Models;
 
 namespace DHT.Desktop.Main.Controls;
 
-sealed class StatusBarModel : BaseModel {
+sealed class StatusBarModel : BaseModel, IDisposable {
 	public DatabaseStatistics DatabaseStatistics { get; }
 
-	private Status status = Status.Stopped;
+	private ServerManager.Status serverStatus;
 
-	public Status CurrentStatus {
-		get => status;
-		set {
-			status = value;
-			OnPropertyChanged(nameof(StatusText));
-		}
-	}
-
-	public string StatusText {
-		get {
-			return CurrentStatus switch {
-				Status.Starting => "STARTING",
-				Status.Ready    => "READY",
-				Status.Stopping => "STOPPING",
-				Status.Stopped  => "STOPPED",
+	public string ServerStatusText => serverStatus switch {
+		ServerManager.Status.Starting => "STARTING",
+		ServerManager.Status.Started  => "READY",
+		ServerManager.Status.Stopping => "STOPPING",
+		ServerManager.Status.Stopped  => "STOPPED",
 		_                             => ""
 	};
-		}
-	}
+
+	private readonly State state;
 
 	[Obsolete("Designer")]
-	public StatusBarModel() : this(new DatabaseStatistics()) {}
+	public StatusBarModel() : this(State.Dummy) {}
 
-	public StatusBarModel(DatabaseStatistics databaseStatistics) {
-		this.DatabaseStatistics = databaseStatistics;
+	public StatusBarModel(State state) {
+		this.state = state;
+		this.DatabaseStatistics = state.Db.Statistics;
+
+		state.Server.StatusChanged += OnServerStatusChanged;
+		serverStatus = state.Server.IsRunning ? ServerManager.Status.Started : ServerManager.Status.Stopped;
 	}
 
-	public enum Status {
-		Starting,
-		Ready,
-		Stopping,
-		Stopped
+	public void Dispose() {
+		state.Server.StatusChanged += OnServerStatusChanged;
+	}
+
+	private void OnServerStatusChanged(object? sender, ServerManager.Status e) {
+		Dispatcher.UIThread.InvokeAsync(() => {
+			serverStatus = e;
+			OnPropertyChanged(nameof(ServerStatusText));
+		});
 	}
 }

app/Desktop/Main/MainWindowModel.cs

@@ -8,6 +8,7 @@ using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Screens;
 using DHT.Desktop.Server;
 using DHT.Server;
+using DHT.Utils.Logging;
 using DHT.Utils.Models;
 
 namespace DHT.Desktop.Main;
@@ -15,6 +16,8 @@ namespace DHT.Desktop.Main;
 sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 	private const string DefaultTitle = "Discord History Tracker";
 	
+	private static readonly Log Log = Log.ForType<MainWindowModel>();
+
 	public string Title { get; private set; } = DefaultTitle;
 
 	public UserControl CurrentScreen { get; private set; }
@@ -63,11 +66,11 @@ sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 		}
 
 		if (args.ServerPort != null) {
-			ServerManager.Port = args.ServerPort.Value;
+			ServerConfiguration.Port = args.ServerPort.Value;
 		}
 
 		if (args.ServerToken != null) {
-			ServerManager.Token = args.ServerToken;
+			ServerConfiguration.Token = args.ServerToken;
 		}
 	}
 
@@ -82,15 +85,23 @@ sealed class MainWindowModel : BaseModel, IAsyncDisposable {
 				await state.DisposeAsync();
 			}
 			
-			state = welcomeScreenModel.Db == null ? null : new State(welcomeScreenModel.Db);
-
-			if (state == null) {
+			if (welcomeScreenModel.Db == null) {
+				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);
+				} catch (Exception ex) {
+					Log.Error(ex);
+					await Dialog.ShowOk(window, "Internal Server Error", ex.Message);
+				}
+				
 				Title = Path.GetFileName(state.Db.Path) + " - " + DefaultTitle;
 				mainContentScreenModel = new MainContentScreenModel(window, state);
 				await mainContentScreenModel.Initialize();

app/Desktop/Main/Pages/AdvancedPageModel.cs

@@ -2,7 +2,6 @@ using System;
 using Avalonia.Controls;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Controls;
-using DHT.Desktop.Server;
 using DHT.Server;
 using DHT.Utils.Models;
 
@@ -15,17 +14,13 @@ sealed class AdvancedPageModel : BaseModel, IDisposable {
 	private readonly State state;
 
 	[Obsolete("Designer")]
-	public AdvancedPageModel() : this(null!, State.Dummy, new ServerManager(State.Dummy)) {}
+	public AdvancedPageModel() : this(null!, State.Dummy) {}
 
-	public AdvancedPageModel(Window window, State state, ServerManager serverManager) {
+	public AdvancedPageModel(Window window, State state) {
 		this.window = window;
 		this.state = state;
 
-		ServerConfigurationModel = new ServerConfigurationPanelModel(window, serverManager);
-	}
-
-	public void Initialize() {
-		ServerConfigurationModel.Initialize();
+		ServerConfigurationModel = new ServerConfigurationPanelModel(window, state);
 	}
 
 	public void Dispose() {

app/Desktop/Main/Pages/AttachmentsPageModel.cs

@@ -1,9 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
-using System.Threading;
+using System.Reactive.Linq;
 using System.Threading.Tasks;
-using Avalonia.Threading;
+using Avalonia.ReactiveUI;
 using DHT.Desktop.Common;
 using DHT.Desktop.Main.Controls;
 using DHT.Server;
@@ -11,7 +11,6 @@ using DHT.Server.Data;
 using DHT.Server.Data.Aggregations;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
-using DHT.Server.Download;
 using DHT.Utils.Models;
 using DHT.Utils.Tasks;
 
@@ -61,6 +60,7 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 	private readonly State state;
 	private readonly AsyncValueComputer<DownloadStatusStatistics>.Single downloadStatisticsComputer;
 	
+	private IDisposable? finishedItemsSubscription;
 	private int doneItemsCount;
 	private int initialFinishedCount;
 	private int? totalItemsToDownloadCount;
@@ -76,12 +76,11 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 		downloadStatisticsComputer.Recompute();
 
 		state.Db.Statistics.PropertyChanged += OnDbStatisticsChanged;
-		state.Downloader.OnItemFinished += DownloaderOnOnItemFinished;
 	}
 
 	public void Dispose() {
 		state.Db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
-		state.Downloader.OnItemFinished -= DownloaderOnOnItemFinished;
+		finishedItemsSubscription?.Dispose();
 		FilterModel.Dispose();
 	}
 
@@ -139,19 +138,22 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 		OnPropertyChanged(nameof(DownloadProgress));
 	}
 
-	private void DownloaderOnOnItemFinished(object? sender, DownloadItem e) {
-		Interlocked.Increment(ref doneItemsCount);
-		
-		Dispatcher.UIThread.Invoke(UpdateDownloadMessage);
+	private void OnItemsFinished(int finishedItemCount) {
+		doneItemsCount += finishedItemCount;
+		UpdateDownloadMessage();
 		downloadStatisticsComputer.Recompute();
 	}
 
 	public async Task OnClickToggleDownload() {
-		if (IsDownloading) {
 		IsToggleDownloadButtonEnabled = false;
+		
+		if (IsDownloading) {
 			await state.Downloader.Stop();
+			
+			finishedItemsSubscription?.Dispose();
+			finishedItemsSubscription = null;
+			
 			downloadStatisticsComputer.Recompute();
-			IsToggleDownloadButtonEnabled = true;
 
 			state.Db.RemoveDownloadItems(EnqueuedItemFilter, FilterRemovalMode.RemoveMatching);
 
@@ -161,13 +163,22 @@ sealed class AttachmentsPageModel : BaseModel, IDisposable {
 			UpdateDownloadMessage();
 		}
 		else {
+			var finishedItems = await state.Downloader.Start();
+
 			initialFinishedCount = statisticsDownloaded.Items + statisticsFailed.Items;
-			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);
+			
 			EnqueueDownloadItems();
 		}
 
 		OnPropertyChanged(nameof(ToggleDownloadButtonText));
 		OnPropertyChanged(nameof(IsDownloading));
+		IsToggleDownloadButtonEnabled = true;
 	}
 
 	public void OnClickRetryFailedDownloads() {

app/Desktop/Main/Pages/TrackingPageModel.cs

@@ -54,7 +54,7 @@ sealed class TrackingPageModel : BaseModel {
 	}
 	
 	public async Task<bool> OnClickCopyTrackingScript() {
-		string url = $"http://127.0.0.1:{ServerManager.Port}/get-tracking-script?token={HttpUtility.UrlEncode(ServerManager.Token)}";
+		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);
 
 		var clipboard = window.Clipboard;

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -110,7 +110,7 @@ sealed class ViewerPageModel : BaseModel, IDisposable {
 		TemporaryFiles.Add(fullPath);
 
 		Directory.CreateDirectory(rootPath);
-		await WriteViewerFile(fullPath, new LiveViewerExportStrategy(ServerManager.Port, ServerManager.Token));
+		await WriteViewerFile(fullPath, new LiveViewerExportStrategy(ServerConfiguration.Port, ServerConfiguration.Token));
 
 		Process.Start(new ProcessStartInfo(fullPath) { UseShellExecute = true });
 	}

app/Desktop/Main/Screens/MainContentScreenModel.cs

@@ -1,12 +1,9 @@
 using System;
 using System.Threading.Tasks;
 using Avalonia.Controls;
-using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Controls;
 using DHT.Desktop.Main.Pages;
-using DHT.Desktop.Server;
 using DHT.Server;
-using DHT.Server.Service;
 using DHT.Utils.Logging;
 
 namespace DHT.Desktop.Main.Screens;
@@ -49,18 +46,10 @@ sealed class MainContentScreenModel : IDisposable {
 		}
 	}
 
-	private readonly Window window;
-	private readonly ServerManager serverManager;
-
 	[Obsolete("Designer")]
 	public MainContentScreenModel() : this(null!, State.Dummy) {}
 
 	public MainContentScreenModel(Window window, State state) {
-		this.window = window;
-		this.serverManager = new ServerManager(state);
-
-		ServerLauncher.ServerManagementExceptionCaught += ServerLauncherOnServerManagementExceptionCaught;
-
 		DatabasePageModel = new DatabasePageModel(window, state);
 		DatabasePage = new DatabasePage { DataContext = DatabasePageModel };
 
@@ -73,7 +62,7 @@ sealed class MainContentScreenModel : IDisposable {
 		ViewerPageModel = new ViewerPageModel(window, state);
 		ViewerPage = new ViewerPage { DataContext = ViewerPageModel };
 
-		AdvancedPageModel = new AdvancedPageModel(window, state, serverManager);
+		AdvancedPageModel = new AdvancedPageModel(window, state);
 		AdvancedPage = new AdvancedPage { DataContext = AdvancedPageModel };
 
 		#if DEBUG
@@ -83,37 +72,17 @@ sealed class MainContentScreenModel : IDisposable {
 		DebugPage = null;
 		#endif
 
-		StatusBarModel = new StatusBarModel(state.Db.Statistics);
-
-		AdvancedPageModel.ServerConfigurationModel.ServerStatusChanged += OnServerStatusChanged;
-		DatabaseClosed += OnDatabaseClosed;
-
-		StatusBarModel.CurrentStatus = serverManager.IsRunning ? StatusBarModel.Status.Ready : StatusBarModel.Status.Stopped;
+		StatusBarModel = new StatusBarModel(state);
 	}
 
 	public async Task Initialize() {
 		await TrackingPageModel.Initialize();
-		AdvancedPageModel.Initialize();
-		serverManager.Launch();
 	}
 
 	public void Dispose() {
-		ServerLauncher.ServerManagementExceptionCaught -= ServerLauncherOnServerManagementExceptionCaught;
 		AttachmentsPageModel.Dispose();
 		ViewerPageModel.Dispose();
-		serverManager.Dispose();
-	}
-
-	private void OnServerStatusChanged(object? sender, StatusBarModel.Status e) {
-		StatusBarModel.CurrentStatus = e;
-	}
-
-	private void OnDatabaseClosed(object? sender, EventArgs e) {
-		serverManager.Stop();
-	}
-
-	private async void ServerLauncherOnServerManagementExceptionCaught(object? sender, Exception ex) {
-		Log.Error(ex);
-		await Dialog.ShowOk(window, "Internal Server Error", ex.Message);
+		AdvancedPageModel.Dispose();
+		StatusBarModel.Dispose();
 	}
 }

app/Desktop/Server/ServerConfiguration.cs

@@ -0,0 +1,8 @@
+using DHT.Server.Service;
+
+namespace DHT.Desktop.Server;
+
+static class ServerConfiguration {
+	public static ushort Port { get; set; } = ServerUtils.FindAvailablePort(50000, 60000);
+	public static string Token { get; set; } = ServerUtils.GenerateRandomToken(20);
+}

app/Desktop/Server/ServerManager.cs

@@ -1,50 +0,0 @@
-using System;
-using DHT.Server;
-using DHT.Server.Service;
-
-namespace DHT.Desktop.Server;
-
-sealed class ServerManager : IDisposable {
-	public static ushort Port { get; set; } = ServerUtils.FindAvailablePort(50000, 60000);
-	public static string Token { get; set; } = ServerUtils.GenerateRandomToken(20);
-
-	private static ServerManager? instance;
-
-	public bool IsRunning => ServerLauncher.IsRunning;
-
-	private readonly State state;
-
-	public ServerManager(State state) {
-		if (state != State.Dummy) {
-			if (instance != null) {
-				throw new InvalidOperationException("Only one instance of ServerManager can exist at the same time!");
-			}
-
-			instance = this;
-		}
-
-		this.state = state;
-	}
-
-	public void Launch() {
-		ServerLauncher.Relaunch(Port, Token, state.Db);
-	}
-
-	public void Relaunch(ushort port, string token) {
-		Port = port;
-		Token = token;
-		Launch();
-	}
-
-	public void Stop() {
-		ServerLauncher.Stop();
-	}
-
-	public void Dispose() {
-		Stop();
-
-		if (instance == this) {
-			instance = null;
-		}
-	}
-}

app/Server/Download/Downloader.cs

@@ -9,8 +9,6 @@ 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);
 	
@@ -18,13 +16,11 @@ public sealed class Downloader {
 		this.db = db;
 	}
 
-	public async Task Start() {
+	public async Task<IObservable<DownloadItem>> Start() {
 		await semaphore.WaitAsync();
 		try {
-			if (current == null) {
-				current = new DownloaderTask(db);
-				current.OnItemFinished += DelegateOnItemFinished;
-			}
+			current ??= new DownloaderTask(db);
+			return current.FinishedItems;
 		} finally {
 			semaphore.Release();
 		}
@@ -34,16 +30,11 @@ public sealed class Downloader {
 		await semaphore.WaitAsync();
 		try {
 			if (current != null) {
-				await current.Stop();
-				current.OnItemFinished -= DelegateOnItemFinished;
+				await current.DisposeAsync();
 				current = null;
 			}
 		} finally {
 			semaphore.Release();
 		}
 	}
-
-	private void DelegateOnItemFinished(object? sender, DownloadItem e) {
-		OnItemFinished?.Invoke(this, e);
-	}
 }

app/Server/Download/DownloaderTask.cs

@@ -1,25 +1,23 @@
 using System;
 using System.Linq;
 using System.Net.Http;
+using System.Reactive.Subjects;
 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 {
+sealed class DownloaderTask : IAsyncDisposable {
 	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,
@@ -31,12 +29,16 @@ sealed class DownloaderTask : BaseModel {
 	private readonly CancellationToken cancellationToken;
 
 	private readonly IDatabaseFile db;
+	private readonly Subject<DownloadItem> finishedItemPublisher = new ();
+	
 	private readonly Task queueWriterTask;
 	private readonly Task[] downloadTasks;
 	
+	public IObservable<DownloadItem> FinishedItems => finishedItemPublisher;
+
 	internal DownloaderTask(IDatabaseFile db) {
-		this.cancellationToken = cancellationTokenSource.Token;
 		this.db = db;
+		this.cancellationToken = cancellationTokenSource.Token;
 		this.queueWriterTask = Task.Run(RunQueueWriterTask);
 		this.downloadTasks = Enumerable.Range(1, DownloadTasks).Select(taskIndex => Task.Run(() => RunDownloadTask(taskIndex))).ToArray();
 	}
@@ -79,7 +81,7 @@ sealed class DownloaderTask : BaseModel {
 				log.Error(e);
 			} finally {
 				try {
-					OnItemFinished?.Invoke(this, item);
+					finishedItemPublisher.OnNext(item);
 				} catch (Exception e) {
 					log.Error("Caught exception in event handler: " + e);
 				}
@@ -87,7 +89,7 @@ sealed class DownloaderTask : BaseModel {
 		}
 	}
 
-	internal async Task Stop() {
+	public async ValueTask DisposeAsync() {
 		try {
 			await cancellationTokenSource.CancelAsync();
 		} catch (Exception) {
@@ -102,6 +104,7 @@ sealed class DownloaderTask : BaseModel {
 			await Task.WhenAll(downloadTasks).WaitIgnoringCancellation();
 		} finally {
 			cancellationTokenSource.Dispose();
+			finishedItemPublisher.OnCompleted();
 		}
 	}
 }

app/Server/Server.csproj

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

app/Server/Service/ServerLauncher.cs

@@ -1,126 +0,0 @@
-using System;
-using System.Collections.Concurrent;
-using System.Diagnostics.CodeAnalysis;
-using System.Threading;
-using DHT.Server.Database;
-using DHT.Utils.Logging;
-using Microsoft.AspNetCore.Hosting;
-using Microsoft.AspNetCore.Server.Kestrel.Core;
-using Microsoft.Extensions.DependencyInjection;
-
-namespace DHT.Server.Service;
-
-public static class ServerLauncher {
-	private static readonly Log Log = Log.ForType(typeof(ServerLauncher));
-
-	private static IWebHost? Server { get; set; } = null;
-
-	public static bool IsRunning { get; private set; }
-	public static event EventHandler? ServerStatusChanged;
-	public static event EventHandler<Exception>? ServerManagementExceptionCaught;
-
-	private static Thread? ManagementThread { get; set; } = null;
-	private static readonly Mutex ManagementThreadLock = new();
-	private static readonly BlockingCollection<IMessage> Messages = new(new ConcurrentQueue<IMessage>());
-
-	private static void EnqueueMessage(IMessage message) {
-		ManagementThreadLock.WaitOne();
-
-		try {
-			if (ManagementThread == null) {
-				ManagementThread = new Thread(RunManagementThread) {
-					Name = "DHT server management thread",
-					IsBackground = true
-				};
-				ManagementThread.Start();
-			}
-
-			Messages.Add(message);
-		} finally {
-			ManagementThreadLock.ReleaseMutex();
-		}
-	}
-
-	[SuppressMessage("ReSharper", "FunctionNeverReturns")]
-	private static void RunManagementThread() {
-		foreach (IMessage message in Messages.GetConsumingEnumerable()) {
-			try {
-				switch (message) {
-					case IMessage.StartServer start:
-						StopServerFromManagementThread();
-						StartServerFromManagementThread(start.Port, start.Token, start.Db);
-						break;
-					case IMessage.StopServer:
-						StopServerFromManagementThread();
-						break;
-				}
-			} catch (Exception e) {
-				ServerManagementExceptionCaught?.Invoke(null, e);
-			}
-		}
-	}
-
-	private static void StartServerFromManagementThread(ushort port, string token, IDatabaseFile db) {
-		Log.Info("Starting server on port " + port + "...");
-
-		void AddServices(IServiceCollection services) {
-			services.AddSingleton(typeof(IDatabaseFile), db);
-			services.AddSingleton(typeof(ServerParameters), new ServerParameters(port, token));
-		}
-
-		void SetKestrelOptions(KestrelServerOptions options) {
-			options.Limits.MaxRequestBodySize = null;
-			options.Limits.MinResponseDataRate = null;
-			options.ListenLocalhost(port, static listenOptions => listenOptions.Protocols = HttpProtocols.Http1);
-		}
-
-		Server = new WebHostBuilder()
-		         .ConfigureServices(AddServices)
-		         .UseKestrel(SetKestrelOptions)
-		         .UseStartup<Startup>()
-		         .Build();
-
-		Server.Start();
-
-		Log.Info("Server started");
-		IsRunning = true;
-		ServerStatusChanged?.Invoke(null, EventArgs.Empty);
-	}
-
-	private static void StopServerFromManagementThread() {
-		if (Server != null) {
-			Log.Info("Stopping server...");
-			Server.StopAsync().Wait();
-			Server.Dispose();
-			Server = null;
-
-			Log.Info("Server stopped");
-			IsRunning = false;
-			ServerStatusChanged?.Invoke(null, EventArgs.Empty);
-		}
-	}
-
-	public static void Relaunch(ushort port, string token, IDatabaseFile db) {
-		EnqueueMessage(new IMessage.StartServer(port, token, db));
-	}
-
-	public static void Stop() {
-		EnqueueMessage(new IMessage.StopServer());
-	}
-
-	private interface IMessage {
-		public sealed class StartServer : IMessage {
-			public ushort Port { get; }
-			public string Token { get; }
-			public IDatabaseFile Db { get; }
-
-			public StartServer(ushort port, string token, IDatabaseFile db) {
-				this.Port = port;
-				this.Token = token;
-				this.Db = db;
-			}
-		}
-
-		public sealed class StopServer : IMessage {}
-	}
-}

app/Server/Service/ServerManager.cs

@@ -0,0 +1,107 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using DHT.Server.Database;
+using DHT.Utils.Logging;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Server.Kestrel.Core;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace DHT.Server.Service;
+
+public sealed class ServerManager {
+	private static readonly Log Log = Log.ForType(typeof(ServerManager));
+
+	private IWebHost? server;
+	public bool IsRunning => server != null;
+	
+	public event EventHandler<Status>? StatusChanged;
+
+	public enum Status {
+		Starting,
+		Started,
+		Stopping,
+		Stopped
+	}
+
+	private readonly IDatabaseFile db;
+	private readonly SemaphoreSlim semaphore = new (1, 1);
+
+	internal ServerManager(IDatabaseFile db) {
+		this.db = db;
+	}
+
+	public async Task Start(ushort port, string token) {
+		await semaphore.WaitAsync();
+		try {
+			await StartInternal(port, token);
+		} finally {
+			semaphore.Release();
+		}
+	}
+
+	public async Task Stop() {
+		await semaphore.WaitAsync();
+		try {
+			await StopInternal();
+		} finally {
+			semaphore.Release();
+		}
+	}
+
+	private async Task StartInternal(ushort port, string token) {
+		await StopInternal();
+		
+		StatusChanged?.Invoke(this, Status.Starting);
+
+		void AddServices(IServiceCollection services) {
+			services.AddSingleton(typeof(IDatabaseFile), db);
+			services.AddSingleton(typeof(ServerParameters), new ServerParameters(port, token));
+		}
+
+		void SetKestrelOptions(KestrelServerOptions options) {
+			options.Limits.MaxRequestBodySize = null;
+			options.Limits.MinResponseDataRate = null;
+			options.ListenLocalhost(port, static listenOptions => listenOptions.Protocols = HttpProtocols.Http1);
+		}
+
+		var newServer = new WebHostBuilder()
+		                .ConfigureServices(AddServices)
+		                .UseKestrel(SetKestrelOptions)
+		                .UseStartup<Startup>()
+		                .Build();
+
+		Log.Info("Starting server on port " + port + "...");
+		
+		try {
+			await newServer.StartAsync();
+		} catch (Exception) {
+			Log.Error("Server could not start");
+			StatusChanged?.Invoke(this, Status.Stopped);
+			throw;
+		}
+
+		Log.Info("Server started");
+
+		server = newServer;
+		
+		StatusChanged?.Invoke(this, Status.Started);
+	}
+
+	private async Task StopInternal() {
+		if (server == null) {
+			return;
+		}
+
+		StatusChanged?.Invoke(this, Status.Stopping);
+		
+		Log.Info("Stopping server...");
+		await server.StopAsync();
+		Log.Info("Server stopped");
+
+		server.Dispose();
+		server = null;
+		
+		StatusChanged?.Invoke(this, Status.Stopped);
+	}
+}

app/Server/State.cs

@@ -2,6 +2,7 @@ using System;
 using System.Threading.Tasks;
 using DHT.Server.Database;
 using DHT.Server.Download;
+using DHT.Server.Service;
 
 namespace DHT.Server;
 
@@ -10,14 +11,17 @@ public sealed class State : IAsyncDisposable {
 	
 	public IDatabaseFile Db { get; }
 	public Downloader Downloader { get; }
+	public ServerManager Server { get; }
 
 	public State(IDatabaseFile db) {
 		Db = db;
 		Downloader = new Downloader(db);
+		Server = new ServerManager(db);
 	}
 
 	public async ValueTask DisposeAsync() {
 		await Downloader.Stop();
+		await Server.Stop();
 		Db.Dispose();
 	}
 }