Clarify and fix instructions for platform-portable releases

Closes #182

app/Desktop/Dialogs/CheckBox/CheckBoxDialog.axaml

@@ -34,8 +34,8 @@
 
     <StackPanel Margin="20">
         <ScrollViewer MaxHeight="400">
-            <ItemsControl Items="{Binding Items}">
-                <ItemsControl.ItemTemplate>
+            <ItemsRepeater Items="{Binding Items}">
+                <ItemsRepeater.ItemTemplate>
                     <DataTemplate>
                         <CheckBox IsChecked="{Binding Checked}">
                             <Label>
@@ -43,8 +43,8 @@
                             </Label>
                         </CheckBox>
                     </DataTemplate>
-                </ItemsControl.ItemTemplate>
-            </ItemsControl>
+                </ItemsRepeater.ItemTemplate>
+            </ItemsRepeater>
         </ScrollViewer>
         <Panel Classes="buttons">
             <WrapPanel Classes="left">

app/Desktop/Main/Controls/FilterPanel.axaml

@@ -35,26 +35,29 @@
         </Style>
     </UserControl.Styles>
 
-    <WrapPanel>
-        <StackPanel>
-            <CheckBox IsChecked="{Binding FilterByDate}">Filter by Date</CheckBox>
-            <Grid ColumnDefinitions="Auto, 4, 125" RowDefinitions="Auto, 4, Auto" Margin="4 0">
-                <Label Grid.Row="0" Grid.Column="0">From:</Label>
-                <CalendarDatePicker Grid.Row="0" Grid.Column="2" x:Name="StartDatePicker" IsEnabled="{Binding FilterByDate}" SelectedDateChanged="CalendarDatePicker_OnSelectedDateChanged" />
-                <Label Grid.Row="2" Grid.Column="0">To:</Label>
-                <CalendarDatePicker Grid.Row="2" Grid.Column="2" x:Name="EndDatePicker" IsEnabled="{Binding FilterByDate}" SelectedDateChanged="CalendarDatePicker_OnSelectedDateChanged" />
-            </Grid>
-        </StackPanel>
-        <StackPanel>
-            <CheckBox IsChecked="{Binding FilterByChannel}">Filter by Channel</CheckBox>
-            <Button Command="{Binding OpenChannelFilterDialog}" IsEnabled="{Binding FilterByChannel}">Select Channels...</Button>
-            <TextBlock Text="{Binding ChannelFilterLabel}" />
-        </StackPanel>
-        <StackPanel>
-            <CheckBox IsChecked="{Binding FilterByUser}">Filter by User</CheckBox>
-            <Button Command="{Binding OpenUserFilterDialog}" IsEnabled="{Binding FilterByUser}">Select Users...</Button>
-            <TextBlock Text="{Binding UserFilterLabel}" />
-        </StackPanel>
-    </WrapPanel>
+    <StackPanel>
+        <TextBlock Text="{Binding FilterStatisticsText}" />
+        <WrapPanel>
+            <StackPanel>
+                <CheckBox IsChecked="{Binding FilterByDate}">Filter by Date</CheckBox>
+                <Grid ColumnDefinitions="Auto, 4, 125" RowDefinitions="Auto, 4, Auto" Margin="4 0">
+                    <Label Grid.Row="0" Grid.Column="0">From:</Label>
+                    <CalendarDatePicker Grid.Row="0" Grid.Column="2" x:Name="StartDatePicker" IsEnabled="{Binding FilterByDate}" SelectedDateChanged="CalendarDatePicker_OnSelectedDateChanged" />
+                    <Label Grid.Row="2" Grid.Column="0">To:</Label>
+                    <CalendarDatePicker Grid.Row="2" Grid.Column="2" x:Name="EndDatePicker" IsEnabled="{Binding FilterByDate}" SelectedDateChanged="CalendarDatePicker_OnSelectedDateChanged" />
+                </Grid>
+            </StackPanel>
+            <StackPanel>
+                <CheckBox IsChecked="{Binding FilterByChannel}">Filter by Channel</CheckBox>
+                <Button Command="{Binding OpenChannelFilterDialog}" IsEnabled="{Binding FilterByChannel}">Select Channels...</Button>
+                <TextBlock Text="{Binding ChannelFilterLabel}" />
+            </StackPanel>
+            <StackPanel>
+                <CheckBox IsChecked="{Binding FilterByUser}">Filter by User</CheckBox>
+                <Button Command="{Binding OpenUserFilterDialog}" IsEnabled="{Binding FilterByUser}">Select Users...</Button>
+                <TextBlock Text="{Binding UserFilterLabel}" />
+            </StackPanel>
+        </WrapPanel>
+    </StackPanel>
 
 </UserControl>

app/Desktop/Main/Controls/FilterPanelModel.cs

@@ -12,6 +12,7 @@ using DHT.Server.Data;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
 using DHT.Utils.Models;
+using DHT.Utils.Tasks;
 
 namespace DHT.Desktop.Main.Controls {
 	sealed class FilterPanelModel : BaseModel, IDisposable {
@@ -25,6 +26,8 @@ namespace DHT.Desktop.Main.Controls {
 			nameof(IncludedUsers)
 		};
 
+		public string FilterStatisticsText { get; private set; } = "";
+
 		public event PropertyChangedEventHandler? FilterPropertyChanged;
 
 		public bool HasAnyFilters => FilterByDate || FilterByChannel || FilterByUser;
@@ -89,13 +92,20 @@ namespace DHT.Desktop.Main.Controls {
 		private readonly Window window;
 		private readonly IDatabaseFile db;
 
+		private readonly AsyncValueComputer<long> exportedMessageCountComputer;
+		private long? exportedMessageCount;
+		private long? totalMessageCount;
+
 		[Obsolete("Designer")]
 		public FilterPanelModel() : this(null!, DummyDatabaseFile.Instance) {}
 
 		public FilterPanelModel(Window window, IDatabaseFile db) {
 			this.window = window;
 			this.db = db;
+			
+			this.exportedMessageCountComputer = AsyncValueComputer<long>.WithResultProcessor(SetExportedMessageCount).Build();
 
+			UpdateFilterStatisticsText();
 			UpdateChannelFilterLabel();
 			UpdateUserFilterLabel();
 
@@ -109,6 +119,7 @@ namespace DHT.Desktop.Main.Controls {
 
 		private void OnPropertyChanged(object? sender, PropertyChangedEventArgs e) {
 			if (e.PropertyName != null && FilterProperties.Contains(e.PropertyName)) {
+				UpdateFilterStatistics();
 				FilterPropertyChanged?.Invoke(sender, e);
 			}
 
@@ -121,7 +132,11 @@ namespace DHT.Desktop.Main.Controls {
 		}
 
 		private void OnDbStatisticsChanged(object? sender, PropertyChangedEventArgs e) {
-			if (e.PropertyName == nameof(DatabaseStatistics.TotalChannels)) {
+			if (e.PropertyName == nameof(DatabaseStatistics.TotalMessages)) {
+				totalMessageCount = db.Statistics.TotalMessages;
+				UpdateFilterStatistics();
+			}
+			else if (e.PropertyName == nameof(DatabaseStatistics.TotalChannels)) {
 				UpdateChannelFilterLabel();
 			}
 			else if (e.PropertyName == nameof(DatabaseStatistics.TotalUsers)) {
@@ -129,6 +144,32 @@ namespace DHT.Desktop.Main.Controls {
 			}
 		}
 
+		private void UpdateFilterStatistics() {
+			var filter = CreateFilter();
+			if (filter.IsEmpty) {
+				exportedMessageCount = totalMessageCount;
+				UpdateFilterStatisticsText();
+			}
+			else {
+				exportedMessageCount = null;
+				UpdateFilterStatisticsText();
+				exportedMessageCountComputer.Compute(_ => db.CountMessages(filter));
+			}
+		}
+
+		private void SetExportedMessageCount(long exportedMessageCount) {
+			this.exportedMessageCount = exportedMessageCount;
+			UpdateFilterStatisticsText();
+		}
+		
+		private void UpdateFilterStatisticsText() {
+			var exportedMessageCountStr = exportedMessageCount?.Format() ?? "(...)";
+			var totalMessageCountStr = totalMessageCount?.Format() ?? "(...)";
+			
+			FilterStatisticsText = "Will export " + exportedMessageCountStr + " out of " + totalMessageCountStr + " message" + (totalMessageCount is null or > 0 ? "s." : ".");
+			OnPropertyChanged(nameof(FilterStatisticsText));
+		}
+
 		public async void OpenChannelFilterDialog() {
 			var servers = db.GetAllServers().ToDictionary(static server => server.Id);
 			var items = new List<CheckBoxItem<ulong>>();

app/Desktop/Main/MainWindow.axaml.cs

@@ -1,8 +1,10 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
+using System.IO;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
+using DHT.Desktop.Main.Pages;
 using JetBrains.Annotations;
 
 namespace DHT.Desktop.Main {
@@ -30,6 +32,14 @@ namespace DHT.Desktop.Main {
 			if (DataContext is IDisposable disposable) {
 				disposable.Dispose();
 			}
+
+			foreach (var temporaryFile in ViewerPageModel.TemporaryFiles) {
+				try {
+					File.Delete(temporaryFile);
+				} catch (Exception) {
+					// ignored
+				}
+			}
 		}
 	}
 }

app/Desktop/Main/Pages/ViewerPage.axaml

@@ -5,9 +5,7 @@
              xmlns:pages="clr-namespace:DHT.Desktop.Main.Pages"
              xmlns:controls="clr-namespace:DHT.Desktop.Main.Controls"
              mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
-             x:Class="DHT.Desktop.Main.Pages.ViewerPage"
-             AttachedToVisualTree="OnAttachedToVisualTree"
-             DetachedFromVisualTree="OnDetachedFromVisualTree">
+             x:Class="DHT.Desktop.Main.Pages.ViewerPage">
 
     <Design.DataContext>
         <pages:ViewerPageModel />
@@ -24,8 +22,7 @@
             <Button Command="{Binding OnClickOpenViewer}" Margin="0 0 5 0">Open Viewer</Button>
             <Button Command="{Binding OnClickSaveViewer}" Margin="5 0 0 0">Save Viewer</Button>
         </StackPanel>
-        <TextBlock Text="{Binding ExportedMessageText}" Margin="0 20 0 0" />
-        <controls:FilterPanel DataContext="{Binding FilterModel}" />
+        <controls:FilterPanel DataContext="{Binding FilterModel}" Margin="0 20 0 0" />
         <Expander Header="Database Tools">
             <StackPanel Orientation="Vertical" Spacing="10">
                 <StackPanel Orientation="Vertical" Spacing="4">

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

@@ -1,5 +1,4 @@
 using System.Diagnostics.CodeAnalysis;
-using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
 
@@ -13,17 +12,5 @@ namespace DHT.Desktop.Main.Pages {
 		private void InitializeComponent() {
 			AvaloniaXamlLoader.Load(this);
 		}
-
-		public void OnAttachedToVisualTree(object? sender, VisualTreeAttachmentEventArgs e) {
-			if (DataContext is ViewerPageModel model) {
-				model.SetPageVisible(true);
-			}
-		}
-
-		public void OnDetachedFromVisualTree(object? sender, VisualTreeAttachmentEventArgs e) {
-			if (DataContext is ViewerPageModel model) {
-				model.SetPageVisible(false);
-			}
-		}
 	}
 }

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -1,8 +1,10 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.IO;
+using System.Text;
 using System.Threading.Tasks;
 using System.Web;
 using Avalonia.Controls;
@@ -17,8 +19,8 @@ using static DHT.Desktop.Program;
 
 namespace DHT.Desktop.Main.Pages {
 	sealed class ViewerPageModel : BaseModel, IDisposable {
-		public string ExportedMessageText { get; private set; } = "";
-
+		public static readonly ConcurrentBag<string> TemporaryFiles = new ();
+		
 		public bool DatabaseToolFilterModeKeep { get; set; } = true;
 		public bool DatabaseToolFilterModeRemove { get; set; } = false;
 
@@ -34,8 +36,6 @@ namespace DHT.Desktop.Main.Pages {
 		private readonly Window window;
 		private readonly IDatabaseFile db;
 
-		private bool isPageVisible = false;
-
 		[Obsolete("Designer")]
 		public ViewerPageModel() : this(null!, DummyDatabaseFile.Instance) {}
 
@@ -45,49 +45,51 @@ namespace DHT.Desktop.Main.Pages {
 
 			FilterModel = new FilterPanelModel(window, db);
 			FilterModel.FilterPropertyChanged += OnFilterPropertyChanged;
-			db.Statistics.PropertyChanged += OnDbStatisticsChanged;
 		}
 
 		public void Dispose() {
-			db.Statistics.PropertyChanged -= OnDbStatisticsChanged;
 			FilterModel.Dispose();
 		}
 
-		public void SetPageVisible(bool isPageVisible) {
-			this.isPageVisible = isPageVisible;
-			if (isPageVisible) {
-				UpdateStatistics();
-			}
-		}
-
 		private void OnFilterPropertyChanged(object? sender, PropertyChangedEventArgs e) {
-			UpdateStatistics();
 			HasFilters = FilterModel.HasAnyFilters;
 		}
 
-		private void OnDbStatisticsChanged(object? sender, PropertyChangedEventArgs e) {
-			if (isPageVisible && e.PropertyName == nameof(DatabaseStatistics.TotalMessages)) {
-				UpdateStatistics();
+		private async Task WriteViewerFile(string path) {
+			const string ArchiveTag = "/*[ARCHIVE]*/";
+
+			string indexFile = await Resources.ReadTextAsync("Viewer/index.html");
+			string viewerTemplate = indexFile.Replace("/*[JS]*/", await Resources.ReadJoinedAsync("Viewer/scripts/", '\n'))
+			                                 .Replace("/*[CSS]*/", await Resources.ReadJoinedAsync("Viewer/styles/", '\n'));
+			
+			int viewerArchiveTagStart = viewerTemplate.IndexOf(ArchiveTag);
+			int viewerArchiveTagEnd = viewerArchiveTagStart + ArchiveTag.Length;
+
+			string jsonTempFile = path + ".tmp";
+
+			await using (var jsonStream = new FileStream(jsonTempFile, FileMode.Create, FileAccess.ReadWrite, FileShare.Read)) {
+				await ViewerJsonExport.Generate(jsonStream, db, FilterModel.CreateFilter());
+
+				char[] jsonBuffer = new char[Math.Min(32768, jsonStream.Position)];
+				jsonStream.Position = 0;
+
+				await using (var outputStream = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.Read))
+				await using (var outputWriter = new StreamWriter(outputStream, Encoding.UTF8)) {
+					await outputWriter.WriteAsync(viewerTemplate[..viewerArchiveTagStart]);
+
+					using (var jsonReader = new StreamReader(jsonStream, Encoding.UTF8)) {
+						int readBytes;
+						while ((readBytes = await jsonReader.ReadAsync(jsonBuffer, 0, jsonBuffer.Length)) > 0) {
+							string jsonChunk = new string(jsonBuffer, 0, readBytes);
+							await outputWriter.WriteAsync(HttpUtility.JavaScriptStringEncode(jsonChunk));
+						}
+					}
+
+					await outputWriter.WriteAsync(viewerTemplate[viewerArchiveTagEnd..]);
+				}
 			}
-		}
 
-		private void UpdateStatistics() {
-			var filter = FilterModel.CreateFilter();
-			var allMessagesCount = db.Statistics.TotalMessages?.Format() ?? "?";
-			var filteredMessagesCount = filter.IsEmpty ? allMessagesCount : db.CountMessages(filter).Format();
-
-			ExportedMessageText = "Will export " + filteredMessagesCount + " out of " + allMessagesCount + " message(s).";
-			OnPropertyChanged(nameof(ExportedMessageText));
-		}
-
-		private async Task<string> GenerateViewerContents() {
-			string json = ViewerJsonExport.Generate(db, FilterModel.CreateFilter());
-
-			string index = await Resources.ReadTextAsync("Viewer/index.html");
-			string viewer = index.Replace("/*[JS]*/", await Resources.ReadJoinedAsync("Viewer/scripts/", '\n'))
-			                     .Replace("/*[CSS]*/", await Resources.ReadJoinedAsync("Viewer/styles/", '\n'))
-			                     .Replace("/*[ARCHIVE]*/", HttpUtility.JavaScriptStringEncode(json));
-			return viewer;
+			File.Delete(jsonTempFile);
 		}
 
 		public async void OnClickOpenViewer() {
@@ -101,8 +103,10 @@ namespace DHT.Desktop.Main.Pages {
 				fullPath = Path.Combine(rootPath, filenameBase + "-" + counter + ".html");
 			}
 
+			TemporaryFiles.Add(fullPath);
+			
 			Directory.CreateDirectory(rootPath);
-			await File.WriteAllTextAsync(fullPath, await GenerateViewerContents());
+			await WriteViewerFile(fullPath);
 
 			Process.Start(new ProcessStartInfo(fullPath) { UseShellExecute = true });
 		}
@@ -110,7 +114,7 @@ namespace DHT.Desktop.Main.Pages {
 		public async void OnClickSaveViewer() {
 			var dialog = new SaveFileDialog {
 				Title = "Save Viewer",
-				InitialFileName = "archive.html",
+				InitialFileName = Path.GetFileNameWithoutExtension(db.Path) + ".html",
 				Directory = Path.GetDirectoryName(db.Path),
 				Filters = new List<FileDialogFilter> {
 					new() {
@@ -122,7 +126,7 @@ namespace DHT.Desktop.Main.Pages {
 
 			string? path = await dialog;
 			if (!string.IsNullOrEmpty(path)) {
-				await File.WriteAllTextAsync(path, await GenerateViewerContents());
+				await WriteViewerFile(path);
 			}
 		}
 

app/Server/Database/Export/ViewerJsonExport.cs

@@ -1,6 +1,8 @@
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text.Json;
+using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
 using DHT.Utils.Logging;
@@ -9,7 +11,7 @@ namespace DHT.Server.Database.Export {
 	public static class ViewerJsonExport {
 		private static readonly Log Log = Log.ForType(typeof(ViewerJsonExport));
 
-		public static string Generate(IDatabaseFile db, MessageFilter? filter = null) {
+		public static async Task Generate(Stream stream, IDatabaseFile db, MessageFilter? filter = null) {
 			var perf = Log.Start();
 
 			var includedUserIds = new HashSet<ulong>();
@@ -37,17 +39,20 @@ namespace DHT.Server.Database.Export {
 
 			perf.Step("Collect database data");
 
+			var value = new {
+				meta = new { users, userindex, servers, channels },
+				data = GenerateMessageList(includedMessages, userIndices)
+			};
+			
+			perf.Step("Generate value object");
+			
 			var opts = new JsonSerializerOptions();
 			opts.Converters.Add(new ViewerJsonSnowflakeSerializer());
 
-			var json = JsonSerializer.Serialize(new {
-				meta = new { users, userindex, servers, channels },
-				data = GenerateMessageList(includedMessages, userIndices)
-			}, opts);
+			await JsonSerializer.SerializeAsync(stream, value, opts);
 
 			perf.Step("Serialize to JSON");
 			perf.End();
-			return json;
 		}
 
 		private static object GenerateUserList(IDatabaseFile db, HashSet<ulong> userIds, out List<string> userindex, out Dictionary<ulong, object> userIndices) {
@@ -159,8 +164,8 @@ namespace DHT.Server.Database.Export {
 					}
 
 					if (!message.Attachments.IsEmpty) {
-						obj["a"] = message.Attachments.Select(static attachment => new {
-							url = attachment.Url
+						obj["a"] = message.Attachments.Select(static attachment => new Dictionary<string, object> {
+							{ "url", attachment.Url }
 						}).ToArray();
 					}
 

app/Server/Database/Sqlite/SqliteDatabaseFile.cs

@@ -2,12 +2,14 @@ using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database.Sqlite.Utils;
 using DHT.Utils.Collections;
 using DHT.Utils.Logging;
+using DHT.Utils.Tasks;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite {
@@ -36,12 +38,12 @@ namespace DHT.Server.Database.Sqlite {
 
 		private readonly Log log;
 		private readonly SqliteConnectionPool pool;
-		private readonly SqliteMessageStatisticsThread messageStatisticsThread;
+		private readonly AsyncValueComputer<long>.Single totalMessagesComputer;
 
 		private SqliteDatabaseFile(string path, SqliteConnectionPool pool) {
 			this.log = Log.ForType(typeof(SqliteDatabaseFile), System.IO.Path.GetFileName(path));
 			this.pool = pool;
-			this.messageStatisticsThread = new SqliteMessageStatisticsThread(pool, UpdateMessageStatistics);
+			this.totalMessagesComputer = AsyncValueComputer<long>.WithResultProcessor(UpdateMessageStatistics).WithOutdatedResults().BuildWithComputer(ComputeMessageStatistics);
 
 			this.Path = path;
 			this.Statistics = new DatabaseStatistics();
@@ -52,11 +54,10 @@ namespace DHT.Server.Database.Sqlite {
 				UpdateUserStatistics(conn);
 			}
 
-			messageStatisticsThread.RequestUpdate();
+			totalMessagesComputer.Recompute();
 		}
 
 		public void Dispose() {
-			messageStatisticsThread.Dispose();
 			pool.Dispose();
 		}
 
@@ -193,119 +194,121 @@ namespace DHT.Server.Database.Sqlite {
 				cmd.ExecuteNonQuery();
 			}
 
-			using var conn = pool.Take();
-			using var tx = conn.BeginTransaction();
+			using (var conn = pool.Take()) {
+				using var tx = conn.BeginTransaction();
 
-			using var messageCmd = conn.Upsert("messages", new[] {
-				("message_id", SqliteType.Integer),
-				("sender_id", SqliteType.Integer),
-				("channel_id", SqliteType.Integer),
-				("text", SqliteType.Text),
-				("timestamp", SqliteType.Integer)
-			});
+				using var messageCmd = conn.Upsert("messages", new[] {
+					("message_id", SqliteType.Integer),
+					("sender_id", SqliteType.Integer),
+					("channel_id", SqliteType.Integer),
+					("text", SqliteType.Text),
+					("timestamp", SqliteType.Integer)
+				});
 
-			using var deleteEditTimestampCmd = DeleteByMessageId(conn, "edit_timestamps");
-			using var deleteRepliedToCmd = DeleteByMessageId(conn, "replied_to");
+				using var deleteEditTimestampCmd = DeleteByMessageId(conn, "edit_timestamps");
+				using var deleteRepliedToCmd = DeleteByMessageId(conn, "replied_to");
 
-			using var deleteAttachmentsCmd = DeleteByMessageId(conn, "attachments");
-			using var deleteEmbedsCmd = DeleteByMessageId(conn, "embeds");
-			using var deleteReactionsCmd = DeleteByMessageId(conn, "reactions");
+				using var deleteAttachmentsCmd = DeleteByMessageId(conn, "attachments");
+				using var deleteEmbedsCmd = DeleteByMessageId(conn, "embeds");
+				using var deleteReactionsCmd = DeleteByMessageId(conn, "reactions");
 
-			using var editTimestampCmd = conn.Insert("edit_timestamps", new [] {
-				("message_id", SqliteType.Integer),
-				("edit_timestamp", SqliteType.Integer)
-			});
+				using var editTimestampCmd = conn.Insert("edit_timestamps", new [] {
+					("message_id", SqliteType.Integer),
+					("edit_timestamp", SqliteType.Integer)
+				});
 
-			using var repliedToCmd = conn.Insert("replied_to", new [] {
-				("message_id", SqliteType.Integer),
-				("replied_to_id", SqliteType.Integer)
-			});
+				using var repliedToCmd = conn.Insert("replied_to", new [] {
+					("message_id", SqliteType.Integer),
+					("replied_to_id", SqliteType.Integer)
+				});
 
-			using var attachmentCmd = conn.Insert("attachments", new[] {
-				("message_id", SqliteType.Integer),
-				("attachment_id", SqliteType.Integer),
-				("name", SqliteType.Text),
-				("type", SqliteType.Text),
-				("url", SqliteType.Text),
-				("size", SqliteType.Integer)
-			});
+				using var attachmentCmd = conn.Insert("attachments", new[] {
+					("message_id", SqliteType.Integer),
+					("attachment_id", SqliteType.Integer),
+					("name", SqliteType.Text),
+					("type", SqliteType.Text),
+					("url", SqliteType.Text),
+					("size", SqliteType.Integer)
+				});
 
-			using var embedCmd = conn.Insert("embeds", new[] {
-				("message_id", SqliteType.Integer),
-				("json", SqliteType.Text)
-			});
+				using var embedCmd = conn.Insert("embeds", new[] {
+					("message_id", SqliteType.Integer),
+					("json", SqliteType.Text)
+				});
 
-			using var reactionCmd = conn.Insert("reactions", new[] {
-				("message_id", SqliteType.Integer),
-				("emoji_id", SqliteType.Integer),
-				("emoji_name", SqliteType.Text),
-				("emoji_flags", SqliteType.Integer),
-				("count", SqliteType.Integer)
-			});
+				using var reactionCmd = conn.Insert("reactions", new[] {
+					("message_id", SqliteType.Integer),
+					("emoji_id", SqliteType.Integer),
+					("emoji_name", SqliteType.Text),
+					("emoji_flags", SqliteType.Integer),
+					("count", SqliteType.Integer)
+				});
 
-			foreach (var message in messages) {
-				object messageId = message.Id;
+				foreach (var message in messages) {
+					object messageId = message.Id;
 
-				messageCmd.Set(":message_id", messageId);
-				messageCmd.Set(":sender_id", message.Sender);
-				messageCmd.Set(":channel_id", message.Channel);
-				messageCmd.Set(":text", message.Text);
-				messageCmd.Set(":timestamp", message.Timestamp);
-				messageCmd.ExecuteNonQuery();
+					messageCmd.Set(":message_id", messageId);
+					messageCmd.Set(":sender_id", message.Sender);
+					messageCmd.Set(":channel_id", message.Channel);
+					messageCmd.Set(":text", message.Text);
+					messageCmd.Set(":timestamp", message.Timestamp);
+					messageCmd.ExecuteNonQuery();
 
-				ExecuteDeleteByMessageId(deleteEditTimestampCmd, messageId);
-				ExecuteDeleteByMessageId(deleteRepliedToCmd, messageId);
+					ExecuteDeleteByMessageId(deleteEditTimestampCmd, messageId);
+					ExecuteDeleteByMessageId(deleteRepliedToCmd, messageId);
 
-				ExecuteDeleteByMessageId(deleteAttachmentsCmd, messageId);
-				ExecuteDeleteByMessageId(deleteEmbedsCmd, messageId);
-				ExecuteDeleteByMessageId(deleteReactionsCmd, messageId);
+					ExecuteDeleteByMessageId(deleteAttachmentsCmd, messageId);
+					ExecuteDeleteByMessageId(deleteEmbedsCmd, messageId);
+					ExecuteDeleteByMessageId(deleteReactionsCmd, messageId);
 
-				if (message.EditTimestamp is {} timestamp) {
-					editTimestampCmd.Set(":message_id", messageId);
-					editTimestampCmd.Set(":edit_timestamp", timestamp);
-					editTimestampCmd.ExecuteNonQuery();
-				}
+					if (message.EditTimestamp is {} timestamp) {
+						editTimestampCmd.Set(":message_id", messageId);
+						editTimestampCmd.Set(":edit_timestamp", timestamp);
+						editTimestampCmd.ExecuteNonQuery();
+					}
 
-				if (message.RepliedToId is {} repliedToId) {
-					repliedToCmd.Set(":message_id", messageId);
-					repliedToCmd.Set(":replied_to_id", repliedToId);
-					repliedToCmd.ExecuteNonQuery();
-				}
+					if (message.RepliedToId is {} repliedToId) {
+						repliedToCmd.Set(":message_id", messageId);
+						repliedToCmd.Set(":replied_to_id", repliedToId);
+						repliedToCmd.ExecuteNonQuery();
+					}
 
-				if (!message.Attachments.IsEmpty) {
-					foreach (var attachment in message.Attachments) {
-						attachmentCmd.Set(":message_id", messageId);
-						attachmentCmd.Set(":attachment_id", attachment.Id);
-						attachmentCmd.Set(":name", attachment.Name);
-						attachmentCmd.Set(":type", attachment.Type);
-						attachmentCmd.Set(":url", attachment.Url);
-						attachmentCmd.Set(":size", attachment.Size);
-						attachmentCmd.ExecuteNonQuery();
+					if (!message.Attachments.IsEmpty) {
+						foreach (var attachment in message.Attachments) {
+							attachmentCmd.Set(":message_id", messageId);
+							attachmentCmd.Set(":attachment_id", attachment.Id);
+							attachmentCmd.Set(":name", attachment.Name);
+							attachmentCmd.Set(":type", attachment.Type);
+							attachmentCmd.Set(":url", attachment.Url);
+							attachmentCmd.Set(":size", attachment.Size);
+							attachmentCmd.ExecuteNonQuery();
+						}
+					}
+
+					if (!message.Embeds.IsEmpty) {
+						foreach (var embed in message.Embeds) {
+							embedCmd.Set(":message_id", messageId);
+							embedCmd.Set(":json", embed.Json);
+							embedCmd.ExecuteNonQuery();
+						}
+					}
+
+					if (!message.Reactions.IsEmpty) {
+						foreach (var reaction in message.Reactions) {
+							reactionCmd.Set(":message_id", messageId);
+							reactionCmd.Set(":emoji_id", reaction.EmojiId);
+							reactionCmd.Set(":emoji_name", reaction.EmojiName);
+							reactionCmd.Set(":emoji_flags", (int) reaction.EmojiFlags);
+							reactionCmd.Set(":count", reaction.Count);
+							reactionCmd.ExecuteNonQuery();
+						}
 					}
 				}
 
-				if (!message.Embeds.IsEmpty) {
-					foreach (var embed in message.Embeds) {
-						embedCmd.Set(":message_id", messageId);
-						embedCmd.Set(":json", embed.Json);
-						embedCmd.ExecuteNonQuery();
-					}
-				}
-
-				if (!message.Reactions.IsEmpty) {
-					foreach (var reaction in message.Reactions) {
-						reactionCmd.Set(":message_id", messageId);
-						reactionCmd.Set(":emoji_id", reaction.EmojiId);
-						reactionCmd.Set(":emoji_name", reaction.EmojiName);
-						reactionCmd.Set(":emoji_flags", (int) reaction.EmojiFlags);
-						reactionCmd.Set(":count", reaction.Count);
-						reactionCmd.ExecuteNonQuery();
-					}
-				}
+				tx.Commit();
 			}
 
-			tx.Commit();
-			messageStatisticsThread.RequestUpdate();
+			totalMessagesComputer.Recompute();
 		}
 
 		public int CountMessages(MessageFilter? filter = null) {
@@ -367,11 +370,12 @@ LEFT JOIN replied_to rt ON m.message_id = rt.message_id" + filter.GenerateWhereC
 			                      .Append("FROM messages")
 			                      .Append(whereClause);
 
-			using var conn = pool.Take();
-			using var cmd = conn.Command(build.ToString());
-			cmd.ExecuteNonQuery();
+			using (var conn = pool.Take()) {
+				using var cmd = conn.Command(build.ToString());
+				cmd.ExecuteNonQuery();
+			}
 
-			UpdateMessageStatistics(conn);
+			totalMessagesComputer.Recompute();
 			perf.End();
 		}
 
@@ -454,8 +458,13 @@ LEFT JOIN replied_to rt ON m.message_id = rt.message_id" + filter.GenerateWhereC
 			Statistics.TotalUsers = conn.SelectScalar("SELECT COUNT(*) FROM users") as long? ?? 0;
 		}
 
-		private void UpdateMessageStatistics(ISqliteConnection conn) {
-			Statistics.TotalMessages = conn.SelectScalar("SELECT COUNT(*) FROM messages") as long? ?? 0L;
+		private long ComputeMessageStatistics(CancellationToken token) {
+			using var conn = pool.Take();
+			return conn.SelectScalar("SELECT COUNT(*) FROM messages") as long? ?? 0L;
+		}
+
+		private void UpdateMessageStatistics(long totalMessages) {
+			Statistics.TotalMessages = totalMessages;
 		}
 	}
 }

app/Server/Database/Sqlite/SqliteMessageStatisticsThread.cs

@@ -1,54 +0,0 @@
-using System;
-using System.Threading;
-using DHT.Server.Database.Sqlite.Utils;
-
-namespace DHT.Server.Database.Sqlite {
-	sealed class SqliteMessageStatisticsThread : IDisposable {
-		private readonly SqliteConnectionPool pool;
-		private readonly Action<ISqliteConnection> action;
-		
-		private readonly CancellationTokenSource cancellationTokenSource = new();
-		private readonly CancellationToken cancellationToken;
-		
-		private readonly AutoResetEvent requestEvent = new (false);
-
-		public SqliteMessageStatisticsThread(SqliteConnectionPool pool, Action<ISqliteConnection> action) {
-			this.pool = pool;
-			this.action = action;
-			
-			this.cancellationToken = cancellationTokenSource.Token;
-			
-			var thread = new Thread(RunThread) {
-				Name = "DHT message statistics thread",
-				IsBackground = true
-			};
-			thread.Start();
-		}
-
-		public void Dispose() {
-			try {
-				cancellationTokenSource.Cancel();
-			} catch (ObjectDisposedException) {}
-		}
-
-		public void RequestUpdate() {
-			try {
-				requestEvent.Set();
-			} catch (ObjectDisposedException) {}
-		}
-
-		private void RunThread() {
-			try {
-				while (!cancellationToken.IsCancellationRequested) {
-					if (requestEvent.WaitOne(TimeSpan.FromMilliseconds(100))) {
-						using var conn = pool.Take();
-						action(conn);
-					}
-				}
-			} finally {
-				cancellationTokenSource.Dispose();
-				requestEvent.Dispose();
-			}
-		}
-	}
-}

app/Utils/Tasks/AsyncValueComputer.cs

@@ -0,0 +1,115 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Tasks {
+	public sealed class AsyncValueComputer<TValue> {
+		private readonly Action<TValue> resultProcessor;
+		private readonly TaskScheduler resultTaskScheduler;
+		private readonly bool processOutdatedResults;
+
+		private readonly object stateLock = new ();
+
+		private CancellationTokenSource? currentCancellationTokenSource;
+		private Func<CancellationToken, TValue>? currentComputeFunction;
+		private bool hasComputeFunctionChanged = false;
+
+		private AsyncValueComputer(Action<TValue> resultProcessor, TaskScheduler resultTaskScheduler, bool processOutdatedResults) {
+			this.resultProcessor = resultProcessor;
+			this.resultTaskScheduler = resultTaskScheduler;
+			this.processOutdatedResults = processOutdatedResults;
+		}
+
+		public void Compute(Func<CancellationToken, TValue> func) {
+			lock (stateLock) {
+				if (currentComputeFunction != null) {
+					currentComputeFunction = func;
+					hasComputeFunctionChanged = true;
+					currentCancellationTokenSource?.Cancel();
+				}
+				else {
+					EnqueueComputation(func);
+				}
+			}
+		}
+
+		[SuppressMessage("ReSharper", "MethodSupportsCancellation")]
+		private void EnqueueComputation(Func<CancellationToken, TValue> func) {
+			var cancellationTokenSource = new CancellationTokenSource();
+			var cancellationToken = cancellationTokenSource.Token;
+
+			currentCancellationTokenSource?.Cancel();
+			currentCancellationTokenSource = cancellationTokenSource;
+			currentComputeFunction = func;
+			hasComputeFunctionChanged = false;
+
+			var task = Task.Run(() => func(cancellationToken));
+			
+			task.ContinueWith(t => {
+				if (processOutdatedResults || !cancellationToken.IsCancellationRequested) {
+					resultProcessor(t.Result);
+				}
+			}, CancellationToken.None, TaskContinuationOptions.NotOnFaulted, resultTaskScheduler);
+			
+			task.ContinueWith(_ => {
+				lock (stateLock) {
+					cancellationTokenSource.Dispose();
+
+					if (currentCancellationTokenSource == cancellationTokenSource) {
+						currentCancellationTokenSource = null;
+					}
+
+					if (hasComputeFunctionChanged) {
+						EnqueueComputation(currentComputeFunction);
+					}
+					else {
+						currentComputeFunction = null;
+					}
+				}
+			});
+		}
+
+		public sealed class Single {
+			private readonly AsyncValueComputer<TValue> baseComputer;
+			private readonly Func<CancellationToken, TValue> resultComputer;
+
+			internal Single(AsyncValueComputer<TValue> baseComputer, Func<CancellationToken, TValue> resultComputer) {
+				this.baseComputer = baseComputer;
+				this.resultComputer = resultComputer;
+			}
+
+			public void Recompute() {
+				baseComputer.Compute(resultComputer);
+			}
+		}
+
+		public static Builder WithResultProcessor(Action<TValue> resultProcessor, TaskScheduler? scheduler = null) {
+			return new Builder(resultProcessor, scheduler ?? TaskScheduler.FromCurrentSynchronizationContext());
+		}
+
+		public sealed class Builder {
+			private readonly Action<TValue> resultProcessor;
+			private readonly TaskScheduler resultTaskScheduler;
+			private bool processOutdatedResults;
+
+			internal Builder(Action<TValue> resultProcessor, TaskScheduler resultTaskScheduler) {
+				this.resultProcessor = resultProcessor;
+				this.resultTaskScheduler = resultTaskScheduler;
+			}
+
+			public Builder WithOutdatedResults() {
+				this.processOutdatedResults = true;
+				return this;
+			}
+
+			public AsyncValueComputer<TValue> Build() {
+				return new AsyncValueComputer<TValue>(resultProcessor, resultTaskScheduler, processOutdatedResults);
+			}
+
+			public Single BuildWithComputer(Func<CancellationToken, TValue> resultComputer) {
+				return new Single(Build(), resultComputer);
+			}
+		}
+	}
+}

web/index.php

@@ -53,11 +53,11 @@ define('LATEST_VERSION', $version === false ? '_' : $version);
           <svg class="icon">
             <use href="#icon-globe" />
           </svg>
-          <span class="platform">Portable</span>
+          <span class="platform">Other</span>
         </a>
       </div>
       <p>To launch the three OS-specific versions, extract the <strong>DiscordHistoryTracker</strong> executable, and double-click it.</p>
-      <p>To launch the <strong>Portable</strong> version, which works on other operating systems including 32-bit versions, you must install <a href="https://dotnet.microsoft.com/download/dotnet/5.0/runtime" rel="nofollow noopener">.NET 5</a>. Then extract the downloaded archive into a folder, open the folder in a terminal, and type: <code>dotnet DiscordHistoryTracker.dll</code></p>
+      <p>To launch the <strong>Other</strong> version, which works on other operating systems including 32-bit versions, you must install <a href="https://dotnet.microsoft.com/download/dotnet/5.0" rel="nofollow noopener">ASP.NET Core Runtime 5</a>. Then extract the downloaded archive into a folder, open the folder in a terminal, and type: <code>dotnet DiscordHistoryTracker.dll</code></p>
       
       <h3>How to Track Messages</h3>
       <p>The app saves messages into a database file stored on your computer. When you open the app, you are given the option to create a new database file, or open an existing one.</p>