Release v47.2

Closes #295

app/Desktop/Common/AvaloniaObsevableValueExtensions.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using DHT.Utils.Observables;
+
+namespace DHT.Desktop.Common;
+
+static class AvaloniaObsevableValueExtensions {
+	public static IDisposable SubscribeLastOnUI<T>(this ObservableValue<T> observable, Action<T> action, TimeSpan delayBetweenRuns) {
+		Task Action(T value, CancellationToken cancellationToken) {
+			action(value);
+			return Task.Delay(delayBetweenRuns, cancellationToken);
+		}
+		
+		return observable.SubscribeLast(Action, TaskScheduler.FromCurrentSynchronizationContext());
+	}
+}

app/Desktop/Main/Controls/DownloadItemFilterPanelModel.cs

@@ -2,9 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading.Tasks;
-using Avalonia.ReactiveUI;
 using DHT.Desktop.Common;
 using DHT.Server;
 using DHT.Server.Data.Filters;
@@ -49,7 +47,7 @@ sealed partial class DownloadItemFilterPanelModel : IAsyncDisposable {
 	private readonly State state;
 	private readonly string verb;
 	
-	private readonly DelayedThrottledTask<FilterSettings> saveFilterSettingsTask;
+	private readonly ThrottledTask<FilterSettings> saveFilterSettingsTask;
 	private bool isLoadingFilterSettings;
 	
 	private readonly RestartableTask<long> downloadItemCountTask;
@@ -65,10 +63,10 @@ sealed partial class DownloadItemFilterPanelModel : IAsyncDisposable {
 		this.state = state;
 		this.verb = verb;
 		
-		this.saveFilterSettingsTask = new DelayedThrottledTask<FilterSettings>(Log, TimeSpan.FromSeconds(5), SaveFilterSettings);
+		this.saveFilterSettingsTask = new ThrottledTask<FilterSettings>(Log, SaveFilterSettings, TimeSpan.FromSeconds(5), TaskScheduler.Default);
 		
 		this.downloadItemCountTask = new RestartableTask<long>(SetMatchingCount, TaskScheduler.FromCurrentSynchronizationContext());
-		this.downloadItemCountSubscription = state.Db.Downloads.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnDownloadItemCountChanged);
+		this.downloadItemCountSubscription = state.Db.Downloads.TotalCount.SubscribeLastOnUI(OnDownloadItemCountChanged, TimeSpan.FromMilliseconds(15));
 		
 		UpdateFilterStatistics();
 		

app/Desktop/Main/Controls/MessageFilterPanelModel.cs

@@ -4,10 +4,8 @@ using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
-using Avalonia.ReactiveUI;
 using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.CheckBox;
 using DHT.Desktop.Dialogs.Message;
@@ -91,9 +89,9 @@ sealed partial class MessageFilterPanelModel : IDisposable {
 		
 		this.exportedMessageCountTask = new RestartableTask<long>(SetExportedMessageCount, TaskScheduler.FromCurrentSynchronizationContext());
 		
-		this.messageCountSubscription = state.Db.Messages.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnMessageCountChanged);
-		this.channelCountSubscription = state.Db.Channels.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnChannelCountChanged);
-		this.userCountSubscription = state.Db.Users.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnUserCountChanged);
+		this.messageCountSubscription = state.Db.Messages.TotalCount.SubscribeLastOnUI(OnMessageCountChanged, TimeSpan.FromMilliseconds(15));
+		this.channelCountSubscription = state.Db.Channels.TotalCount.SubscribeLastOnUI(OnChannelCountChanged, TimeSpan.FromMilliseconds(15));
+		this.userCountSubscription = state.Db.Users.TotalCount.SubscribeLastOnUI(OnUserCountChanged, TimeSpan.FromMilliseconds(15));
 		
 		UpdateFilterStatistics();
 		UpdateChannelFilterLabel();

app/Desktop/Main/Controls/StatusBarModel.cs

@@ -1,7 +1,6 @@
 using System;
-using System.Reactive.Linq;
-using Avalonia.ReactiveUI;
 using Avalonia.Threading;
+using DHT.Desktop.Common;
 using DHT.Server;
 using DHT.Server.Service;
 using PropertyChanged.SourceGenerator;
@@ -41,9 +40,9 @@ sealed partial class StatusBarModel : IDisposable {
 	public StatusBarModel(State state) {
 		this.state = state;
 		
-		serverCountSubscription = state.Db.Servers.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(newServerCount => ServerCount = newServerCount);
-		channelCountSubscription = state.Db.Channels.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(newChannelCount => ChannelCount = newChannelCount);
-		messageCountSubscription = state.Db.Messages.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(newMessageCount => MessageCount = newMessageCount);
+		serverCountSubscription = state.Db.Servers.TotalCount.SubscribeLastOnUI(newServerCount => ServerCount = newServerCount, TimeSpan.FromMilliseconds(15));
+		channelCountSubscription = state.Db.Channels.TotalCount.SubscribeLastOnUI(newChannelCount => ChannelCount = newChannelCount, TimeSpan.FromMilliseconds(15));
+		messageCountSubscription = state.Db.Messages.TotalCount.SubscribeLastOnUI(newMessageCount => MessageCount = newMessageCount, TimeSpan.FromMilliseconds(15));
 		
 		state.Server.StatusChanged += OnStateServerStatusChanged;
 		serverStatus = state.Server.IsRunning ? ServerManager.Status.Started : ServerManager.Status.Stopped;

app/Desktop/Main/Pages/DatabasePageModel.cs

@@ -55,11 +55,11 @@ sealed class DatabasePageModel {
 				break;
 			
 			case PlatformID.Unix:
-				Process.Start("xdg-open", [ folder ]);
+				Process.Start("xdg-open", [folder]);
 				break;
 			
 			case PlatformID.MacOSX:
-				Process.Start("open", [ folder ]);
+				Process.Start("open", [folder]);
 				break;
 			
 			default:
@@ -80,22 +80,25 @@ sealed class DatabasePageModel {
 		
 		const string Title = "Database Merge";
 		
-		ImportResult? result;
+		var result = new TaskCompletionSource<ImportResult?>();
 		try {
-			result = await ProgressDialog.Show(window, Title, async (dialog, callback) => await MergeWithDatabaseFromPaths(Db, paths, dialog, callback));
+			var dialog = new ProgressDialog();
+			dialog.DataContext = new ProgressDialogModel(Title, async callbacks => result.SetResult(await MergeWithDatabaseFromPaths(Db, paths, dialog, callbacks)), progressItems: 2);
+			await dialog.ShowProgressDialog(window);
 		} catch (Exception e) {
 			Log.Error("Could not merge databases.", e);
 			await Dialog.ShowOk(window, Title, "Could not merge databases: " + e.Message);
 			return;
 		}
 		
-		await Dialog.ShowOk(window, Title, GetImportDialogMessage(result, "database file"));
+		await Dialog.ShowOk(window, Title, GetImportDialogMessage(result.Task.Result, "database file"));
 	}
 	
-	private static async Task<ImportResult?> MergeWithDatabaseFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
-		var schemaUpgradeCallbacks = new SchemaUpgradeCallbacks(dialog, paths.Length);
+	private static async Task<ImportResult?> MergeWithDatabaseFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IReadOnlyList<IProgressCallback> callbacks) {
+		var schemaUpgradeCallbacks = new SchemaUpgradeCallbacks(dialog, callbacks[1], paths.Length);
+		var databaseMergeProgressCallback = new DatabaseMergeProgressCallback(callbacks[1]);
 		
-		return await PerformImport(target, paths, dialog, callback, "Database Merge", async path => {
+		return await PerformImport(target, paths, dialog, callbacks[0], "Database Merge", async path => {
 			IDatabaseFile? db = await DatabaseGui.TryOpenOrCreateDatabaseFromPath(path, dialog, schemaUpgradeCallbacks);
 			
 			if (db == null) {
@@ -103,7 +106,7 @@ sealed class DatabasePageModel {
 			}
 			
 			try {
-				await target.AddFrom(db);
+				await target.Merge(db, databaseMergeProgressCallback);
 				return true;
 			} finally {
 				await db.DisposeAsync();
@@ -111,7 +114,7 @@ sealed class DatabasePageModel {
 		});
 	}
 	
-	private sealed class SchemaUpgradeCallbacks(ProgressDialog dialog, int total) : ISchemaUpgradeCallbacks {
+	private sealed class SchemaUpgradeCallbacks(ProgressDialog dialog, IProgressCallback callback, int total) : ISchemaUpgradeCallbacks {
 		private bool? decision;
 		
 		public Task<InitialDatabaseSettings?> GetInitialDatabaseSettings() {
@@ -125,6 +128,7 @@ sealed class DatabasePageModel {
 		}
 		
 		public Task Start(int versionSteps, Func<ISchemaUpgradeCallbacks.IProgressReporter, Task> doUpgrade) {
+			callback.UpdateIndeterminate("Upgrading database...");
 			return doUpgrade(new NullReporter());
 		}
 		
@@ -143,6 +147,20 @@ sealed class DatabasePageModel {
 		}
 	}
 	
+	private sealed class DatabaseMergeProgressCallback(IProgressCallback callback) : DatabaseMerging.IProgressCallback {
+		public void OnImportingMetadata() {
+			callback.UpdateIndeterminate("Importing metadata...");
+		}
+		
+		public void OnMessagesImported(long finished, long total) {
+			callback.Update("Importing messages...", finished, total);
+		}
+		
+		public void OnDownloadsImported(long finished, long total) {
+			callback.Update("Importing downloaded files...", finished, total);
+		}
+	}
+	
 	public async Task ImportLegacyArchive() {
 		string[] paths = await window.StorageProvider.OpenFiles(new FilePickerOpenOptions {
 			Title = "Open Legacy DHT Archive",
@@ -223,7 +241,7 @@ sealed class DatabasePageModel {
 		int finished = 0;
 		
 		foreach (string path in paths) {
-			await callback.Update(Path.GetFileName(path), finished, total);
+			await callback.Update("File: " + Path.GetFileName(path), finished, total);
 			++finished;
 			
 			if (!File.Exists(path)) {

app/Desktop/Main/Pages/DownloadsPageModel.cs

@@ -2,11 +2,9 @@ using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
-using System.Reactive.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Platform.Storage;
-using Avalonia.ReactiveUI;
 using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.File;
 using DHT.Desktop.Dialogs.Message;
@@ -19,6 +17,7 @@ using DHT.Server.Data.Filters;
 using DHT.Server.Data.Settings;
 using DHT.Server.Download;
 using DHT.Utils.Logging;
+using DHT.Utils.Observables;
 using DHT.Utils.Tasks;
 using PropertyChanged.SourceGenerator;
 
@@ -82,8 +81,8 @@ sealed partial class DownloadsPageModel : IAsyncDisposable {
 			statisticsSkipped,
 		];
 		
-		downloadStatisticsTask = new ThrottledTask<DownloadStatusStatistics>(Log, UpdateStatistics, TaskScheduler.FromCurrentSynchronizationContext());
-		downloadItemCountSubscription = state.Db.Downloads.TotalCount.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnDownloadCountChanged);
+		downloadStatisticsTask = new ThrottledTask<DownloadStatusStatistics>(Log, UpdateStatistics, TimeSpan.FromMilliseconds(100), TaskScheduler.FromCurrentSynchronizationContext());
+		downloadItemCountSubscription = state.Db.Downloads.TotalCount.SubscribeLastOnUI(OnDownloadCountChanged, TimeSpan.FromMilliseconds(15));
 		
 		RecomputeDownloadStatistics();
 	}
@@ -145,8 +144,8 @@ sealed partial class DownloadsPageModel : IAsyncDisposable {
 		
 		try {
 			currentDownloadFilter = FilterModel.CreateFilter();
-			IObservable<DownloadItem> finishedItems = await state.Downloader.Start(currentDownloadFilter);
-			finishedItemsSubscription = finishedItems.ObserveOn(AvaloniaScheduler.Instance).Subscribe(OnItemFinished);
+			ObservableValue<DownloadItem> finishedItems = await state.Downloader.Start(currentDownloadFilter);
+			finishedItemsSubscription = finishedItems.SubscribeLastOnUI(OnItemFinished, TimeSpan.FromMilliseconds(15));
 		} catch (Exception) {
 			finishedItemsSubscription?.Dispose();
 			finishedItemsSubscription = null;
@@ -285,7 +284,7 @@ sealed partial class DownloadsPageModel : IAsyncDisposable {
 		}
 	}
 	
-	private void UpdateStatistics(DownloadStatusStatistics statusStatistics) {
+	private Task UpdateStatistics(DownloadStatusStatistics statusStatistics) {
 		statisticsPending.Items = statusStatistics.PendingCount;
 		statisticsPending.Size = statusStatistics.PendingTotalSize;
 		statisticsPending.HasFilesWithUnknownSize = statusStatistics.PendingWithUnknownSizeCount > 0;
@@ -304,6 +303,8 @@ sealed partial class DownloadsPageModel : IAsyncDisposable {
 		
 		HasSuccessfulDownloads = statusStatistics.SuccessfulCount > 0;
 		HasFailedDownloads = statusStatistics.FailedCount > 0;
+		
+		return Task.CompletedTask;
 	}
 	
 	public sealed partial class StatisticsRow(string state) {

app/Resources/Viewer/scripts/discord.mjs

@@ -107,7 +107,7 @@ export default (function() {
 	const isImageUrl = function(url) {
 		const dot = url.pathname.lastIndexOf(".");
 		const ext = dot === -1 ? "" : url.pathname.substring(dot).toLowerCase();
-		return ext === ".png" || ext === ".gif" || ext === ".jpg" || ext === ".jpeg";
+		return ext === ".png" || ext === ".gif" || ext === ".jpg" || ext === ".jpeg" || ext === ".webp" || ext === ".avif";
 	};
 	
 	return {

app/Server/Database/DatabaseExtensions.cs

@@ -1,34 +0,0 @@
-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 async Task AddFrom(this IDatabaseFile target, IDatabaseFile source) {
-		await target.Users.Add(await source.Users.Get().ToListAsync());
-		await target.Servers.Add(await source.Servers.Get().ToListAsync());
-		await target.Channels.Add(await source.Channels.Get().ToListAsync());
-		
-		const int MessageBatchSize = 100;
-		List<Message> batchedMessages = new (MessageBatchSize);
-		
-		await foreach (Message message in source.Messages.Get()) {
-			batchedMessages.Add(message);
-			
-			if (batchedMessages.Count >= MessageBatchSize) {
-				await target.Messages.Add(batchedMessages);
-				batchedMessages.Clear();
-			}
-		}
-		
-		await target.Messages.Add(batchedMessages);
-		
-		await foreach (Data.Download download in source.Downloads.Get()) {
-			if (download.Status != DownloadStatus.Success || !await source.Downloads.GetDownloadData(download.NormalizedUrl, stream => target.Downloads.AddDownload(download, stream))) {
-				await target.Downloads.AddDownload(download, stream: null);
-			}
-		}
-	}
-}

app/Server/Database/Import/DatabaseMerging.cs

@@ -0,0 +1,77 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+
+namespace DHT.Server.Database.Import;
+
+public static class DatabaseMerging {
+	public static async Task Merge(this IDatabaseFile target, IDatabaseFile source, IProgressCallback callback) {
+		// Import downloads first, otherwise automatic downloads would try to re-download files from other imported data.
+		await MergeDownloads(target, source, callback);
+		
+		callback.OnImportingMetadata();
+		await target.Users.Add(await source.Users.Get().ToListAsync());
+		await target.Servers.Add(await source.Servers.Get().ToListAsync());
+		await target.Channels.Add(await source.Channels.Get().ToListAsync());
+		
+		await MergeMessages(target, source, callback);
+	}
+	
+	private static async Task MergeDownloads(IDatabaseFile target, IDatabaseFile source, IProgressCallback callback) {
+		const int ReportBatchSize = 100;
+		
+		long totalDownloads = await source.Downloads.Count();
+		long importedDownloads = 0;
+		
+		callback.OnDownloadsImported(importedDownloads, totalDownloads);
+		
+		await foreach (Data.Download download in source.Downloads.Get()) {
+			if (download.Status != DownloadStatus.Success || !await source.Downloads.GetDownloadData(download.NormalizedUrl, stream => target.Downloads.AddDownload(download, stream))) {
+				await target.Downloads.AddDownload(download, stream: null);
+			}
+			
+			if (++importedDownloads % ReportBatchSize == 0) {
+				callback.OnDownloadsImported(importedDownloads, totalDownloads);
+			}
+		}
+		
+		callback.OnDownloadsImported(totalDownloads, totalDownloads);
+	}
+	
+	private static async Task MergeMessages(IDatabaseFile target, IDatabaseFile source, IProgressCallback callback) {
+		const int MessageBatchSize = 100;
+		const int ReportEveryBatches = 10;
+		List<Message> batchedMessages = new (MessageBatchSize);
+		
+		long totalMessages = await source.Messages.Count();
+		long importedMessages = 0;
+		
+		callback.OnMessagesImported(importedMessages, totalMessages);
+		
+		await foreach (Message message in source.Messages.Get()) {
+			batchedMessages.Add(message);
+			
+			if (batchedMessages.Count >= MessageBatchSize) {
+				await target.Messages.Add(batchedMessages);
+				
+				importedMessages += batchedMessages.Count;
+				
+				if (importedMessages % (MessageBatchSize * ReportEveryBatches) == 0) {
+					callback.OnMessagesImported(importedMessages, totalMessages);
+				}
+				
+				batchedMessages.Clear();
+			}
+		}
+		
+		await target.Messages.Add(batchedMessages);
+		callback.OnMessagesImported(totalMessages, totalMessages);
+	}
+	
+	public interface IProgressCallback {
+		void OnImportingMetadata();
+		void OnMessagesImported(long finished, long total);
+		void OnDownloadsImported(long finished, long total);
+	}
+}

app/Server/Database/Repositories/IChannelRepository.cs

@@ -1,15 +1,14 @@
-using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Server.Data;
+using DHT.Utils.Observables;
 
 namespace DHT.Server.Database.Repositories;
 
 public interface IChannelRepository {
-	IObservable<long> TotalCount { get; }
+	ObservableValue<long> TotalCount { get; }
 	
 	Task Add(IReadOnlyList<Channel> channels);
 	
@@ -20,7 +19,7 @@ public interface IChannelRepository {
 	Task<int> RemoveUnreachable();
 	
 	internal sealed class Dummy : IChannelRepository {
-		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
+		public ObservableValue<long> TotalCount { get; } = new (0L);
 		
 		public Task Add(IReadOnlyList<Channel> channels) {
 			return Task.CompletedTask;

app/Server/Database/Repositories/IDownloadRepository.cs

@@ -2,22 +2,22 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Data.Aggregations;
 using DHT.Server.Data.Filters;
 using DHT.Server.Download;
+using DHT.Utils.Observables;
 
 namespace DHT.Server.Database.Repositories;
 
 public interface IDownloadRepository {
-	IObservable<long> TotalCount { get; }
+	ObservableValue<long> TotalCount { get; }
 	
 	Task AddDownload(Data.Download item, Stream? stream);
 	
-	Task<long> Count(DownloadItemFilter filter, CancellationToken cancellationToken = default);
+	Task<long> Count(DownloadItemFilter? filter = null, CancellationToken cancellationToken = default);
 	
 	Task<DownloadStatusStatistics> GetStatistics(DownloadItemFilter nonSkippedFilter, CancellationToken cancellationToken = default);
 	
@@ -38,13 +38,13 @@ public interface IDownloadRepository {
 	IAsyncEnumerable<FileUrl> FindReachableFiles(CancellationToken cancellationToken = default);
 	
 	internal sealed class Dummy : IDownloadRepository {
-		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
+		public ObservableValue<long> TotalCount { get; } = new (0L);
 		
 		public Task AddDownload(Data.Download item, Stream? stream) {
 			return Task.CompletedTask;
 		}
 		
-		public Task<long> Count(DownloadItemFilter filter, CancellationToken cancellationToken) {
+		public Task<long> Count(DownloadItemFilter? filter, CancellationToken cancellationToken) {
 			return Task.FromResult(0L);
 		}
 		

app/Server/Database/Repositories/IMessageRepository.cs

@@ -1,16 +1,15 @@
-using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
+using DHT.Utils.Observables;
 
 namespace DHT.Server.Database.Repositories;
 
 public interface IMessageRepository {
-	IObservable<long> TotalCount { get; }
+	ObservableValue<long> TotalCount { get; }
 	
 	Task Add(IReadOnlyList<Message> messages);
 	
@@ -25,7 +24,7 @@ public interface IMessageRepository {
 	Task<int> RemoveUnreachableAttachments();
 	
 	internal sealed class Dummy : IMessageRepository {
-		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
+		public ObservableValue<long> TotalCount { get; } = new (0L);
 		
 		public Task Add(IReadOnlyList<Message> messages) {
 			return Task.CompletedTask;

app/Server/Database/Repositories/IServerRepository.cs

@@ -1,14 +1,13 @@
-using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using DHT.Utils.Observables;
 
 namespace DHT.Server.Database.Repositories;
 
 public interface IServerRepository {
-	IObservable<long> TotalCount { get; }
+	ObservableValue<long> TotalCount { get; }
 	
 	Task Add(IReadOnlyList<Data.Server> servers);
 	
@@ -19,7 +18,7 @@ public interface IServerRepository {
 	Task<int> RemoveUnreachable();
 	
 	internal sealed class Dummy : IServerRepository {
-		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
+		public ObservableValue<long> TotalCount { get; } = new (0L);
 		
 		public Task Add(IReadOnlyList<Data.Server> servers) {
 			return Task.CompletedTask;

app/Server/Database/Repositories/IUserRepository.cs

@@ -1,15 +1,14 @@
-using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Server.Data;
+using DHT.Utils.Observables;
 
 namespace DHT.Server.Database.Repositories;
 
 public interface IUserRepository {
-	IObservable<long> TotalCount { get; }
+	ObservableValue<long> TotalCount { get; }
 	
 	Task Add(IReadOnlyList<User> users);
 	
@@ -20,7 +19,7 @@ public interface IUserRepository {
 	Task<int> RemoveUnreachable();
 	
 	internal sealed class Dummy : IUserRepository {
-		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
+		public ObservableValue<long> TotalCount { get; } = new (0L);
 		
 		public Task Add(IReadOnlyList<User> users) {
 			return Task.CompletedTask;

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

@@ -1,23 +1,27 @@
 using System;
-using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Utils.Logging;
+using DHT.Utils.Observables;
 using DHT.Utils.Tasks;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
 abstract class BaseSqliteRepository : IDisposable {
-	private readonly ObservableThrottledTask<long> totalCountTask;
+	private readonly ThrottledTask<long> totalCountTask;
 	
-	public IObservable<long> TotalCount { get; }
+	public ObservableValue<long> TotalCount { get; } = new (0L);
 	
 	protected BaseSqliteRepository(Log log) {
-		totalCountTask = new ObservableThrottledTask<long>(log, TaskScheduler.Default);
-		TotalCount = totalCountTask.DistinctUntilChanged();
+		totalCountTask = new ThrottledTask<long>(log, SetTotalCount, TimeSpan.Zero, TaskScheduler.Default);
 		UpdateTotalCount();
 	}
 	
+	private Task SetTotalCount(long newCount) {
+		TotalCount.Set(newCount);
+		return Task.CompletedTask;
+	}
+	
 	public void Dispose() {
 		totalCountTask.Dispose();
 	}

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

@@ -306,12 +306,14 @@ sealed class SqliteDownloadRepository(SqliteConnectionPool pool) : BaseSqliteRep
 			await using var reader = await cmd.ExecuteReaderAsync(cancellationToken);
 			
 			while (await reader.ReadAsync(cancellationToken)) {
-				found.Add(new DownloadItem {
-					NormalizedUrl = reader.GetString(0),
-					DownloadUrl = reader.GetString(1),
-					Type = reader.IsDBNull(2) ? null : reader.GetString(2),
-					Size = reader.IsDBNull(3) ? null : reader.GetUint64(3),
-				});
+				var item = new DownloadItem(
+					NormalizedUrl: reader.GetString(0),
+					DownloadUrl: reader.GetString(1),
+					Type: reader.IsDBNull(2) ? null : reader.GetString(2),
+					Size: reader.IsDBNull(3) ? null : reader.GetUint64(3)
+				);
+				
+				found.Add(item);
 			}
 		}
 		

app/Server/Download/DownloadItem.cs

@@ -4,12 +4,7 @@ using DHT.Server.Data;
 
 namespace DHT.Server.Download;
 
-public readonly struct DownloadItem {
-	public string NormalizedUrl { get; init; }
-	public string DownloadUrl { get; init; }
-	public string? Type { get; init; }
-	public ulong? Size { get; init; }
-	
+public sealed record DownloadItem(string NormalizedUrl, string DownloadUrl, string? Type, ulong? Size) {
 	internal Data.Download ToSuccess(long size) {
 		return new Data.Download(NormalizedUrl, DownloadUrl, DownloadStatus.Success, Type, (ulong) Math.Max(size, val2: 0));
 	}

app/Server/Download/Downloader.cs

@@ -1,8 +1,8 @@
-using System;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
+using DHT.Utils.Observables;
 
 namespace DHT.Server.Download;
 
@@ -19,11 +19,11 @@ public sealed class Downloader {
 		this.concurrentDownloads = concurrentDownloads;
 	}
 	
-	public async Task<IObservable<DownloadItem>> Start(DownloadItemFilter filter) {
+	public async Task<ObservableValue<DownloadItem>> Start(DownloadItemFilter filter) {
 		await semaphore.WaitAsync();
 		try {
 			current ??= new DownloaderTask(db, filter, concurrentDownloads);
-			return current.FinishedItems;
+			return current.LastFinishedItem;
 		} finally {
 			semaphore.Release();
 		}

app/Server/Download/DownloaderTask.cs

@@ -4,13 +4,13 @@ using System.IO;
 using System.Linq;
 using System.Net;
 using System.Net.Http;
-using System.Reactive.Subjects;
 using System.Threading;
 using System.Threading.Channels;
 using System.Threading.Tasks;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
 using DHT.Utils.Logging;
+using DHT.Utils.Observables;
 using DHT.Utils.Tasks;
 
 namespace DHT.Server.Download;
@@ -38,12 +38,11 @@ sealed class DownloaderTask : IAsyncDisposable {
 	
 	private readonly IDatabaseFile db;
 	private readonly DownloadItemFilter filter;
-	private readonly ISubject<DownloadItem> finishedItemPublisher = Subject.Synchronize(new Subject<DownloadItem>());
 	
 	private readonly Task queueWriterTask;
 	private readonly Task[] downloadTasks;
 	
-	public IObservable<DownloadItem> FinishedItems => finishedItemPublisher;
+	public ObservableValue<DownloadItem> LastFinishedItem { get; } = new (null);
 	
 	internal DownloaderTask(IDatabaseFile db, DownloadItemFilter filter, int? concurrentDownloads) {
 		this.db = db;
@@ -101,7 +100,7 @@ sealed class DownloaderTask : IAsyncDisposable {
 				log.Error("Could not download file: " + item.DownloadUrl, e);
 			} finally {
 				try {
-					finishedItemPublisher.OnNext(item);
+					LastFinishedItem.Set(item);
 				} catch (Exception e) {
 					log.Error("Caught exception in event handler: " + e);
 				}
@@ -145,7 +144,6 @@ sealed class DownloaderTask : IAsyncDisposable {
 			await Task.WhenAll(downloadTasks).WaitIgnoringCancellation();
 		} finally {
 			cancellationTokenSource.Dispose();
-			finishedItemPublisher.OnCompleted();
 		}
 	}
 }

app/Utils/Observables/LastValueObserver.cs

@@ -0,0 +1,63 @@
+using System;
+using System.Threading;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Observables;
+
+sealed class LastValueObserver<T> : IDisposable {
+	private readonly ObservableValue<T> observable;
+	private readonly Func<T, CancellationToken, Task> action;
+	private readonly TaskScheduler scheduler;
+	
+	private readonly Channel<T> channel = Channel.CreateBounded<T>(new BoundedChannelOptions(capacity: 1) {
+		AllowSynchronousContinuations = false,
+		FullMode = BoundedChannelFullMode.DropOldest,
+		SingleReader = true,
+		SingleWriter = false,
+	});
+	
+	private readonly CancellationTokenSource cancellationTokenSource = new ();
+	
+	public LastValueObserver(ObservableValue<T> observable, Func<T, CancellationToken, Task> action, TaskScheduler scheduler) {
+		this.observable = observable;
+		this.action = action;
+		this.scheduler = scheduler;
+		
+		_ = ReadNextValue();
+	}
+	
+	private async Task ReadNextValue() {
+		CancellationToken cancellationToken = cancellationTokenSource.Token;
+		
+		try {
+			await foreach (T value in channel.Reader.ReadAllAsync(cancellationToken)) {
+				try {
+					await Task.Factory.StartNew(UseValue, value, CancellationToken.None, TaskCreationOptions.None, scheduler).WaitAsync(cancellationToken);
+				} catch (Exception) {
+					// Ignore.
+				}
+			}
+		} finally {
+			cancellationTokenSource.Dispose();
+		}
+	}
+	
+	private Task UseValue(object? value) {
+		return action((T) value!, cancellationTokenSource.Token);
+	}
+	
+	public void Notify(T value) {
+		channel.Writer.TryWrite(value);
+	}
+	
+	public void Dispose() {
+		observable.Unsubscribe(this);
+		
+		try {
+			cancellationTokenSource.Cancel();
+		} catch (ObjectDisposedException) {}
+		
+		channel.Writer.TryComplete();
+	}
+}

app/Utils/Observables/ObservableValue.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Observables;
+
+public sealed class ObservableValue<T>(T? value) {
+	private readonly List<LastValueObserver<T>> observers = [];
+	private T? value = value;
+	
+	public void Set(T value) {
+		lock (this) {
+			if (EqualityComparer<T>.Default.Equals(value, this.value)) {
+				return;
+			}
+			
+			this.value = value;
+			
+			foreach (var observer in observers) {
+				observer.Notify(value);
+			}
+		}
+	}
+	
+	public IDisposable SubscribeLast(Func<T, CancellationToken, Task> action, TaskScheduler scheduler) {
+		var observer = new LastValueObserver<T>(this, action, scheduler);
+		
+		lock (this) {
+			observers.Add(observer);
+			
+			if (value is not null) {
+				observer.Notify(value);
+			}
+		}
+		
+		return observer;
+	}
+	
+	internal void Unsubscribe(LastValueObserver<T> observer) {
+		lock (this) {
+			observers.Remove(observer);
+		}
+	}
+}

app/Utils/Tasks/DelayedThrottledTask.cs

@@ -1,64 +0,0 @@
-using System;
-using System.Threading;
-using System.Threading.Channels;
-using System.Threading.Tasks;
-using DHT.Utils.Logging;
-
-namespace DHT.Utils.Tasks;
-
-public sealed class DelayedThrottledTask<T> : IDisposable {
-	private readonly Channel<T> taskChannel = Channel.CreateBounded<T>(new BoundedChannelOptions(capacity: 1) {
-		SingleReader = true,
-		SingleWriter = false,
-		AllowSynchronousContinuations = false,
-		FullMode = BoundedChannelFullMode.DropOldest,
-	});
-	
-	private readonly CancellationTokenSource cancellationTokenSource = new ();
-	private readonly Log log;
-	private readonly TimeSpan delay;
-	private readonly Func<T, Task> inputProcessor;
-	
-	public DelayedThrottledTask(Log log, TimeSpan delay, Func<T, Task> inputProcessor) {
-		this.log = log;
-		this.delay = delay;
-		this.inputProcessor = inputProcessor;
-		
-		Task.Run(ReaderTask);
-	}
-	
-	private async Task ReaderTask() {
-		CancellationToken cancellationToken = cancellationTokenSource.Token;
-		
-		try {
-			while (await taskChannel.Reader.WaitToReadAsync(cancellationToken)) {
-				await Task.Delay(delay, cancellationToken);
-				
-				T input = await taskChannel.Reader.ReadAsync(cancellationToken);
-				try {
-					await inputProcessor(input);
-				} catch (OperationCanceledException) {
-					throw;
-				} catch (Exception e) {
-					log.Error("Caught exception in task: " + e);
-				}
-			}
-		} catch (OperationCanceledException) {
-			// Ignore.
-		} finally {
-			cancellationTokenSource.Dispose();
-		}
-	}
-	
-	public void Post(T input) {
-		taskChannel.Writer.TryWrite(input);
-	}
-	
-	public void Dispose() {
-		try {
-			cancellationTokenSource.Cancel();
-		} catch (ObjectDisposedException) {}
-		
-		taskChannel.Writer.Complete();
-	}
-}

app/Utils/Tasks/ObservableThrottledTask.cs

@@ -1,32 +0,0 @@
-using System;
-using System.Reactive.Subjects;
-using System.Threading;
-using System.Threading.Tasks;
-using DHT.Utils.Logging;
-
-namespace DHT.Utils.Tasks;
-
-public sealed class ObservableThrottledTask<T> : IObservable<T>, IDisposable {
-	private readonly ReplaySubject<T> subject;
-	private readonly ThrottledTask<T> task;
-	
-	public ObservableThrottledTask(Log log, TaskScheduler resultScheduler) {
-		this.subject = new ReplaySubject<T>(bufferSize: 1);
-		this.task = new ThrottledTask<T>(log, subject.OnNext, resultScheduler);
-	}
-	
-	public void Post(Func<CancellationToken, Task<T>> resultComputer) {
-		task.Post(resultComputer);
-	}
-	
-	public IDisposable Subscribe(IObserver<T> observer) {
-		return subject.Subscribe(observer);
-	}
-	
-	public void Dispose() {
-		task.Dispose();
-		
-		subject.OnCompleted();
-		subject.Dispose();
-	}
-}

app/Utils/Tasks/ThrottledTask.cs

@@ -14,11 +14,13 @@ public abstract class ThrottledTaskBase<T> : IDisposable {
 		FullMode = BoundedChannelFullMode.DropOldest,
 	});
 	
-	private readonly CancellationTokenSource cancellationTokenSource = new ();
 	private readonly Log log;
+	private readonly TimeSpan delayBetweenRuns;
+	private readonly CancellationTokenSource cancellationTokenSource = new ();
 	
-	internal ThrottledTaskBase(Log log) {
+	internal ThrottledTaskBase(Log log, TimeSpan delayBetweenRuns) {
 		this.log = log;
+		this.delayBetweenRuns = delayBetweenRuns;
 	}
 	
 	protected async Task ReaderTask() {
@@ -33,9 +35,9 @@ public abstract class ThrottledTaskBase<T> : IDisposable {
 				} catch (Exception e) {
 					log.Error("Caught exception in task: " + e);
 				}
+				
+				await Task.Delay(delayBetweenRuns, cancellationToken);
 			}
-		} catch (OperationCanceledException) {
-			// Ignore.
 		} finally {
 			cancellationTokenSource.Dispose();
 		}
@@ -48,20 +50,20 @@ public abstract class ThrottledTaskBase<T> : IDisposable {
 	}
 	
 	public void Dispose() {
-		taskChannel.Writer.Complete();
 		cancellationTokenSource.Cancel();
+		taskChannel.Writer.Complete();
 	}
 }
 
 public sealed class ThrottledTask : ThrottledTaskBase<Task> {
-	private readonly Action resultProcessor;
+	private readonly Func<Task> resultProcessor;
 	private readonly TaskScheduler resultScheduler;
 	
-	public ThrottledTask(Log log, Action resultProcessor, TaskScheduler resultScheduler) : base(log) {
+	public ThrottledTask(Log log, Func<Task> resultProcessor, TimeSpan delayBetweenRuns, TaskScheduler resultScheduler) : base(log, delayBetweenRuns) {
 		this.resultProcessor = resultProcessor;
 		this.resultScheduler = resultScheduler;
 		
-		Task.Run(ReaderTask);
+		_ = ReaderTask();
 	}
 	
 	protected override async Task Run(Func<CancellationToken, Task> func, CancellationToken cancellationToken) {
@@ -71,18 +73,22 @@ public sealed class ThrottledTask : ThrottledTaskBase<Task> {
 }
 
 public sealed class ThrottledTask<T> : ThrottledTaskBase<Task<T>> {
-	private readonly Action<T> resultProcessor;
+	private readonly Func<T, Task> resultProcessor;
 	private readonly TaskScheduler resultScheduler;
 	
-	public ThrottledTask(Log log, Action<T> resultProcessor, TaskScheduler resultScheduler) : base(log) {
+	public ThrottledTask(Log log, Func<T, Task> resultProcessor, TimeSpan delayBetweenRuns, TaskScheduler resultScheduler) : base(log, delayBetweenRuns) {
 		this.resultProcessor = resultProcessor;
 		this.resultScheduler = resultScheduler;
 		
-		Task.Run(ReaderTask);
+		_ = 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);
 	}
+	
+	public void Post(T result) {
+		base.Post(_ => Task.FromResult(result));
+	}
 }

app/Utils/Utils.csproj

@@ -16,7 +16,6 @@
   
   <ItemGroup>
     <PackageReference Include="JetBrains.Annotations" Version="2023.2.0" />
-    <PackageReference Include="System.Reactive" Version="6.0.0" />
   </ItemGroup>
   
   <ItemGroup>

app/Version.cs

@@ -8,5 +8,5 @@ using DHT.Utils;
 namespace DHT.Utils;
 
 static class Version {
-	public const string Tag = "47.1.0.0";
+	public const string Tag = "47.2.0.0";
 }