Release v37.2

Closes #204

app/.idea/.idea.DiscordHistoryTracker/.idea/avalonia.xml

@@ -7,6 +7,7 @@
         <entry key="Desktop/Dialogs/CheckBox/CheckBoxDialog.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Dialogs/Message/MessageDialog.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Dialogs/Progress/ProgressDialog.axaml" value="Desktop/Desktop.csproj" />
+        <entry key="Desktop/Dialogs/TextBox/TextBoxDialog.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/AboutWindow.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Controls/AttachmentFilterPanel.axaml" value="Desktop/Desktop.csproj" />
         <entry key="Desktop/Main/Controls/MessageFilterPanel.axaml" value="Desktop/Desktop.csproj" />

app/Desktop/App.axaml

@@ -7,7 +7,7 @@
     <Application.Styles>
 
         <FluentTheme Mode="Light" />
-        <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Default.xaml"/>
+        <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Default.xaml" />
 
         <Style Selector="Button, CheckBox, RadioButton, Expander /template/ ToggleButton#ExpanderHeader">
             <Setter Property="Cursor" Value="Hand" />
@@ -33,8 +33,19 @@
         <Style Selector="TextBox:focus /template/ Border#PART_BorderElement">
             <Setter Property="BorderThickness" Value="1" />
         </Style>
-        <Style Selector="TextBox:disabled"><!-- TODO bug in Avalonia (https://github.com/AvaloniaUI/Avalonia/pull/7792) -->
-            <Setter Property="Foreground" Value="{DynamicResource TextControlForegroundDisabled}" />
+        <Style Selector="TextBox:error DataValidationErrors">
+            <Style.Resources>
+                <ControlTemplate x:Key="InlineDataValidationContentTemplate" TargetType="DataValidationErrors">
+                    <ContentPresenter Name="PART_ContentPresenter"
+                                      Padding="{TemplateBinding Padding}"
+                                      Background="{TemplateBinding Background}"
+                                      BorderThickness="{TemplateBinding BorderThickness}"
+                                      CornerRadius="{TemplateBinding CornerRadius}"
+                                      Content="{TemplateBinding Content}"
+                                      ContentTemplate="{TemplateBinding ContentTemplate}" />
+                </ControlTemplate>
+            </Style.Resources>
+            <Setter Property="Template" Value="{StaticResource InlineDataValidationContentTemplate}" />
         </Style>
 
         <Style Selector="Expander /template/ ToggleButton#ExpanderHeader">

app/Desktop/Common/BytesValueConverter.cs

@@ -4,12 +4,26 @@ using Avalonia.Data.Converters;
 
 namespace DHT.Desktop.Common {
 	sealed class BytesValueConverter : IValueConverter {
-		private static readonly string[] Units = {
-			"B",
-			"kB",
-			"MB",
-			"GB",
-			"TB"
+		private sealed class Unit {
+			private readonly string label;
+			private readonly string numberFormat;
+			
+			public Unit(string label, int decimalPlaces) {
+				this.label = label;
+				this.numberFormat = "{0:n" + decimalPlaces + "}";
+			}
+			
+			public string Format(double size) {
+				return string.Format(Program.Culture, numberFormat, size) + " " + label;
+			}
+		}
+		
+		private static readonly Unit[] Units = {
+			new ("B", decimalPlaces: 0),
+			new ("kB", decimalPlaces: 0),
+			new ("MB", decimalPlaces: 1),
+			new ("GB", decimalPlaces: 1),
+			new ("TB", decimalPlaces: 1)
 		};
 
 		private const int Scale = 1000;
@@ -17,13 +31,7 @@ namespace DHT.Desktop.Common {
 		private static string Convert(ulong size) {
 			int power = size == 0L ? 0 : (int) Math.Log(size, Scale);
 			int unit = power >= Units.Length ? Units.Length - 1 : power;
-			if (unit == 0) {
-				return string.Format(Program.Culture, "{0:n0}", size) + " " + Units[unit];
-			}
-			else {
-				double humanReadableSize = size / Math.Pow(Scale, unit);
-				return string.Format(Program.Culture, "{0:n0}", humanReadableSize) + " " + Units[unit];
-			}
+			return Units[unit].Format(unit == 0 ? size : size / Math.Pow(Scale, unit));
 		}
 
 		public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture) {

app/Desktop/Desktop.csproj

@@ -21,16 +21,20 @@
     <DebugType>none</DebugType>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="Avalonia" Version="0.10.14" />
-    <PackageReference Include="Avalonia.Controls.DataGrid" Version="0.10.14" />
-    <PackageReference Include="Avalonia.Desktop" Version="0.10.14" />
-    <PackageReference Include="Avalonia.Diagnostics" Version="0.10.14" Condition=" '$(Configuration)' == 'Debug' " />
+    <PackageReference Include="Avalonia" Version="0.10.16" />
+    <PackageReference Include="Avalonia.Controls.DataGrid" Version="0.10.16" />
+    <PackageReference Include="Avalonia.Desktop" Version="0.10.16" />
+    <PackageReference Include="Avalonia.Diagnostics" Version="0.10.16" Condition=" '$(Configuration)' == 'Debug' " />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Server\Server.csproj" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\Version.cs" Link="Version.cs" />
+    <Compile Update="Dialogs\TextBox\TextBoxDialog.axaml.cs">
+      <DependentUpon>CheckBoxDialog.axaml</DependentUpon>
+      <SubType>Code</SubType>
+    </Compile>
   </ItemGroup>
   <ItemGroup>
     <AvaloniaResource Include="Resources/icon.ico" />

app/Desktop/Dialogs/TextBox/TextBoxDialog.axaml

@@ -0,0 +1,56 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:namespace="clr-namespace:DHT.Desktop.Dialogs.TextBox"
+        mc:Ignorable="d" d:DesignWidth="500"
+        x:Class="DHT.Desktop.Dialogs.TextBox.TextBoxDialog"
+        Title="{Binding Title}"
+        Icon="avares://DiscordHistoryTracker/Resources/icon.ico"
+        Width="500" SizeToContent="Height" CanResize="False"
+        WindowStartupLocation="CenterOwner">
+
+    <Window.DataContext>
+        <namespace:TextBoxDialogModel />
+    </Window.DataContext>
+
+    <Window.Styles>
+        <Style Selector="Panel.buttons">
+            <Setter Property="Margin" Value="0 20 0 0" />
+        </Style>
+        <Style Selector="Panel.buttons > WrapPanel.right">
+            <Setter Property="HorizontalAlignment" Value="Right" />
+        </Style>
+        <Style Selector="Panel.buttons Button">
+            <Setter Property="MinWidth" Value="80" />
+            <Setter Property="Margin" Value="8 0 0 0" />
+        </Style>
+    </Window.Styles>
+
+    <StackPanel Margin="20">
+        <ScrollViewer MaxHeight="400">
+            <StackPanel Spacing="10">
+                <TextBlock Text="{Binding Description}" TextWrapping="Wrap" />
+                <ItemsRepeater Items="{Binding Items}">
+                    <ItemsRepeater.ItemTemplate>
+                        <DataTemplate>
+                            <DockPanel Margin="0 5 25 0">
+                                <TextBox Name="Input" Text="{Binding Value}" Width="180" VerticalAlignment="Top" DockPanel.Dock="Right" />
+                                <Label Target="Input" VerticalAlignment="Center" DockPanel.Dock="Left">
+                                    <TextBlock Text="{Binding Title}" TextWrapping="Wrap" />
+                                </Label>
+                            </DockPanel>
+                        </DataTemplate>
+                    </ItemsRepeater.ItemTemplate>
+                </ItemsRepeater>
+            </StackPanel>
+        </ScrollViewer>
+        <Panel Classes="buttons">
+            <WrapPanel Classes="right">
+                <Button Click="ClickOk" IsEnabled="{Binding !HasErrors}">OK</Button>
+                <Button Click="ClickCancel">Cancel</Button>
+            </WrapPanel>
+        </Panel>
+    </StackPanel>
+
+</Window>

app/Desktop/Dialogs/TextBox/TextBoxDialog.axaml.cs

@@ -0,0 +1,31 @@
+using System.Diagnostics.CodeAnalysis;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Markup.Xaml;
+using DHT.Desktop.Dialogs.Message;
+
+namespace DHT.Desktop.Dialogs.TextBox {
+	[SuppressMessage("ReSharper", "MemberCanBeInternal")]
+	public sealed class TextBoxDialog : Window {
+		public TextBoxDialog() {
+			InitializeComponent();
+			#if DEBUG
+			this.AttachDevTools();
+			#endif
+		}
+
+		private void InitializeComponent() {
+			AvaloniaXamlLoader.Load(this);
+		}
+
+		public void ClickOk(object? sender, RoutedEventArgs e) {
+			Close(DialogResult.OkCancel.Ok);
+		}
+
+		public void ClickCancel(object? sender, RoutedEventArgs e) {
+			Close(DialogResult.OkCancel.Cancel);
+		}
+	}
+}
+

app/Desktop/Dialogs/TextBox/TextBoxDialogModel.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using DHT.Utils.Models;
+
+namespace DHT.Desktop.Dialogs.TextBox {
+	class TextBoxDialogModel : BaseModel {
+		public string Title { get; init; } = "";
+		public string Description { get; init; } = "";
+
+		private IReadOnlyList<TextBoxItem> items = Array.Empty<TextBoxItem>();
+
+		public IReadOnlyList<TextBoxItem> Items {
+			get => items;
+
+			protected set {
+				foreach (var item in items) {
+					item.ErrorsChanged -= OnItemErrorsChanged;
+				}
+
+				items = value;
+
+				foreach (var item in items) {
+					item.ErrorsChanged += OnItemErrorsChanged;
+				}
+			}
+		}
+		
+		public bool HasErrors => Items.Any(static item => !item.IsValid);
+
+		private void OnItemErrorsChanged(object? sender, DataErrorsChangedEventArgs e) {
+			OnPropertyChanged(nameof(HasErrors));
+		}
+	}
+
+	sealed class TextBoxDialogModel<T> : TextBoxDialogModel {
+		public new IReadOnlyList<TextBoxItem<T>> Items { get; }
+
+		public IEnumerable<TextBoxItem<T>> ValidItems => Items.Where(static item => item.IsValid);
+
+		public TextBoxDialogModel(IEnumerable<TextBoxItem<T>> items) {
+			this.Items = new List<TextBoxItem<T>>(items);
+			base.Items = this.Items;
+		}
+	}
+}

app/Desktop/Dialogs/TextBox/TextBoxItem.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections;
+using System.ComponentModel;
+using DHT.Utils.Models;
+
+namespace DHT.Desktop.Dialogs.TextBox {
+	class TextBoxItem : BaseModel, INotifyDataErrorInfo {
+		public string Title { get; init; } = "";
+		public object? Item { get; init; } = null;
+		
+		public Func<string, bool> ValidityCheck { get; init; } = static _ => true;
+		public bool IsValid => ValidityCheck(Value);
+
+		private string value = string.Empty;
+
+		public string Value {
+			get => this.value;
+			set {
+				Change(ref this.value, value);
+				ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(nameof(Value)));
+			}
+		}
+
+		public IEnumerable GetErrors(string? propertyName) {
+			if (propertyName == nameof(Value) && !IsValid) {
+				yield return string.Empty;
+			}
+		}
+
+		public bool HasErrors => !IsValid;
+		public event EventHandler<DataErrorsChangedEventArgs>? ErrorsChanged;
+	}
+
+	sealed class TextBoxItem<T> : TextBoxItem {
+		public new T Item { get; }
+
+		public TextBoxItem(T item) {
+			this.Item = item;
+			base.Item = item;
+		}
+	}
+}

app/Desktop/Main/Controls/AttachmentFilterPanelModel.cs

@@ -9,7 +9,7 @@ using DHT.Utils.Tasks;
 
 namespace DHT.Desktop.Main.Controls {
 	sealed class AttachmentFilterPanelModel : BaseModel, IDisposable {
-		public sealed record Unit(string Name, int Scale);
+		public sealed record Unit(string Name, uint Scale);
 
 		private static readonly Unit[] AllUnits = {
 			new ("B", 1),
@@ -26,7 +26,7 @@ namespace DHT.Desktop.Main.Controls {
 		public string FilterStatisticsText { get; private set; } = "";
 
 		private bool limitSize = false;
-		private int maximumSize = 0;
+		private ulong maximumSize = 0L;
 		private Unit maximumSizeUnit = AllUnits[0];
 
 		public bool LimitSize {
@@ -34,7 +34,7 @@ namespace DHT.Desktop.Main.Controls {
 			set => Change(ref limitSize, value);
 		}
 
-		public int MaximumSize {
+		public ulong MaximumSize {
 			get => maximumSize;
 			set => Change(ref maximumSize, value);
 		}
@@ -116,7 +116,11 @@ namespace DHT.Desktop.Main.Controls {
 			AttachmentFilter filter = new();
 
 			if (LimitSize) {
-				filter.MaxBytes = maximumSize * maximumSizeUnit.Scale;
+				try {
+					filter.MaxBytes = maximumSize * maximumSizeUnit.Scale;
+				} catch (ArithmeticException) {
+					// set no size limit, because the overflown size is larger than any file could possibly be
+				}
 			}
 
 			return filter;

app/Desktop/Main/Controls/MessageFilterPanelModel.cs

@@ -169,7 +169,7 @@ namespace DHT.Desktop.Main.Controls {
 			var exportedMessageCountStr = exportedMessageCount?.Format() ?? "(...)";
 			var totalMessageCountStr = totalMessageCount?.Format() ?? "(...)";
 			
-			FilterStatisticsText = verb + " " + exportedMessageCountStr + " out of " + totalMessageCountStr + " message" + (totalMessageCount is null or 0 ? "." : "s.");
+			FilterStatisticsText = verb + " " + exportedMessageCountStr + " out of " + totalMessageCountStr + " message" + (totalMessageCount is null or 1 ? "." : "s.");
 			OnPropertyChanged(nameof(FilterStatisticsText));
 		}
 

app/Desktop/Main/Pages/AttachmentsPageModel.cs

@@ -87,6 +87,9 @@ namespace DHT.Desktop.Main.Pages {
 					downloadStatisticsComputer.Recompute();
 				}
 			}
+			else if (e.PropertyName == nameof(DatabaseStatistics.TotalDownloads)) {
+				downloadStatisticsComputer.Recompute();
+			}
 		}
 
 		private void EnqueueDownloadItems() {
@@ -172,7 +175,6 @@ namespace DHT.Desktop.Main.Pages {
 			};
 
 			db.RemoveDownloadItems(allExceptFailedFilter, FilterRemovalMode.KeepMatching);
-			downloadStatisticsComputer.Recompute();
 
 			if (IsDownloading) {
 				EnqueueDownloadItems();

app/Desktop/Main/Pages/DatabasePage.axaml

@@ -24,6 +24,7 @@
         <WrapPanel>
             <Button Command="{Binding OpenDatabaseFolder}">Open Database Folder</Button>
             <Button Command="{Binding MergeWithDatabase}">Merge with Database(s)...</Button>
+            <Button Command="{Binding ImportLegacyArchive}">Import Legacy Archive(s)...</Button>
         </WrapPanel>
     </StackPanel>
 

app/Desktop/Main/Pages/DatabasePageModel.cs

@@ -1,13 +1,20 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
+using System.Linq;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Controls;
+using Avalonia.Threading;
 using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Dialogs.Progress;
+using DHT.Desktop.Dialogs.TextBox;
+using DHT.Server.Data;
 using DHT.Server.Database;
+using DHT.Server.Database.Import;
 using DHT.Utils.Logging;
 using DHT.Utils.Models;
 
@@ -56,6 +63,10 @@ namespace DHT.Desktop.Main.Pages {
 			}
 		}
 
+		public void CloseDatabase() {
+			DatabaseClosed?.Invoke(this, EventArgs.Empty);
+		}
+
 		public async void MergeWithDatabase() {
 			var fileDialog = DatabaseGui.NewOpenDatabaseFileDialog();
 			fileDialog.Directory = Path.GetDirectoryName(Db.Path);
@@ -74,10 +85,6 @@ namespace DHT.Desktop.Main.Pages {
 			await progressDialog.ShowDialog(window);
 		}
 
-		public void CloseDatabase() {
-			DatabaseClosed?.Invoke(this, EventArgs.Empty);
-		}
-
 		private static async Task MergeWithDatabaseFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
 			int total = paths.Length;
 
@@ -91,8 +98,95 @@ namespace DHT.Desktop.Main.Pages {
 				return DialogResult.YesNo.Yes == upgradeResult;
 			}
 
-			var oldStatistics = target.Statistics.Clone();
-			var oldMessageCount = target.CountMessages();
+			await PerformImport(target, paths, dialog, callback, "Database Merge", "Database Error", "database file", async path => {
+				SynchronizationContext? prevSyncContext = SynchronizationContext.Current;
+				SynchronizationContext.SetSynchronizationContext(new AvaloniaSynchronizationContext());
+				IDatabaseFile? db = await DatabaseGui.TryOpenOrCreateDatabaseFromPath(path, dialog, CheckCanUpgradeDatabase);
+				SynchronizationContext.SetSynchronizationContext(prevSyncContext);
+
+				if (db == null) {
+					return false;
+				}
+
+				try {
+					target.AddFrom(db);
+					return true;
+				} finally {
+					db.Dispose();
+				}
+			});
+		}
+
+		public async void ImportLegacyArchive() {
+			var fileDialog = new OpenFileDialog {
+				Title = "Open Legacy DHT Archive",
+				Directory = Path.GetDirectoryName(Db.Path),
+				AllowMultiple = true
+			};
+
+			string[]? paths = await fileDialog.ShowAsync(window);
+			if (paths == null || paths.Length == 0) {
+				return;
+			}
+
+			ProgressDialog progressDialog = new ProgressDialog();
+			progressDialog.DataContext = new ProgressDialogModel(async callback => await ImportLegacyArchiveFromPaths(Db, paths, progressDialog, callback)) {
+				Title = "Legacy Archive Import"
+			};
+
+			await progressDialog.ShowDialog(window);
+		}
+
+		private static async Task ImportLegacyArchiveFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
+			var fakeSnowflake = new FakeSnowflake();
+
+			await PerformImport(target, paths, dialog, callback, "Legacy Archive Import", "Legacy Archive Error", "archive file", async path => {
+				await using var jsonStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
+				
+				return await LegacyArchiveImport.Read(jsonStream, target, fakeSnowflake, async servers => {
+					SynchronizationContext? prevSyncContext = SynchronizationContext.Current;
+					SynchronizationContext.SetSynchronizationContext(new AvaloniaSynchronizationContext());
+					Dictionary<DHT.Server.Data.Server, ulong>? result = await Dispatcher.UIThread.InvokeAsync(() => AskForServerIds(dialog, servers));
+					SynchronizationContext.SetSynchronizationContext(prevSyncContext);
+					return result;
+				});
+			});
+		}
+
+		private static async Task<Dictionary<DHT.Server.Data.Server, ulong>?> AskForServerIds(Window window, DHT.Server.Data.Server[] servers) {
+			static bool IsValidSnowflake(string value) {
+				return string.IsNullOrEmpty(value) || ulong.TryParse(value, out _);
+			}
+			
+			var items = new List<TextBoxItem<DHT.Server.Data.Server>>();
+
+			foreach (var server in servers.OrderBy(static server => server.Type).ThenBy(static server => server.Name)) {
+				items.Add(new TextBoxItem<DHT.Server.Data.Server>(server) {
+					Title = server.Name + " (" + ServerTypes.ToNiceString(server.Type) + ")",
+					ValidityCheck = IsValidSnowflake
+				});
+			}
+
+			var model = new TextBoxDialogModel<DHT.Server.Data.Server>(items) {
+				Title = "Imported Server IDs",
+				Description = "Please fill in the IDs of servers and direct messages. First enable Developer Mode in Discord, then right-click each server or direct message, click 'Copy ID', and paste it into the input field. If a server no longer exists, leave its input field empty to use a random ID."
+			};
+
+			var dialog = new TextBoxDialog { DataContext = model };
+			var result = await dialog.ShowDialog<DialogResult.OkCancel>(window);
+
+			if (result != DialogResult.OkCancel.Ok) {
+				return null;
+			}
+
+			return model.ValidItems
+			            .Where(static item => !string.IsNullOrEmpty(item.Value))
+			            .ToDictionary(static item => item.Item, static item => ulong.Parse(item.Value));
+		}
+
+		private static async Task PerformImport(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback, string neutralDialogTitle, string errorDialogTitle, string itemName, Func<string, Task<bool>> performImport) {
+			int total = paths.Length;
+			var oldStatistics = target.SnapshotStatistics();
 
 			int successful = 0;
 			int finished = 0;
@@ -102,56 +196,53 @@ namespace DHT.Desktop.Main.Pages {
 				++finished;
 
 				if (!File.Exists(path)) {
-					await Dialog.ShowOk(dialog, "Database Error", "Database '" + Path.GetFileName(path) + "' no longer exists.");
-					continue;
-				}
-
-				IDatabaseFile? db = await DatabaseGui.TryOpenOrCreateDatabaseFromPath(path, dialog, CheckCanUpgradeDatabase);
-				if (db == null) {
+					await Dialog.ShowOk(dialog, errorDialogTitle, "File '" + Path.GetFileName(path) + "' no longer exists.");
 					continue;
 				}
 
 				try {
-					target.AddFrom(db);
+					if (await performImport(path)) {
+						++successful;
+					}
 				} catch (Exception ex) {
 					Log.Error(ex);
-					await Dialog.ShowOk(dialog, "Database Error", "Database '" + Path.GetFileName(path) + "' could not be merged: " + ex.Message);
-					continue;
-				} finally {
-					db.Dispose();
+					await Dialog.ShowOk(dialog, errorDialogTitle, "File '" + Path.GetFileName(path) + "' could not be imported: " + ex.Message);
 				}
-
-				++successful;
 			}
 
 			await callback.Update("Done", finished, total);
 
 			if (successful == 0) {
-				await Dialog.ShowOk(dialog, "Database Merge", "Nothing was merged.");
+				await Dialog.ShowOk(dialog, neutralDialogTitle, "Nothing was imported.");
 				return;
 			}
 
-			var newStatistics = target.Statistics;
+			await Dialog.ShowOk(dialog, neutralDialogTitle, GetImportDialogMessage(oldStatistics, target.SnapshotStatistics(), successful, total, itemName));
+		}
+
+		private static string GetImportDialogMessage(DatabaseStatisticsSnapshot oldStatistics, DatabaseStatisticsSnapshot newStatistics, int successfulItems, int totalItems, string itemName) {
 			long newServers = newStatistics.TotalServers - oldStatistics.TotalServers;
 			long newChannels = newStatistics.TotalChannels - oldStatistics.TotalChannels;
-			long newMessages = target.CountMessages() - oldMessageCount;
+			long newUsers = newStatistics.TotalUsers - oldStatistics.TotalUsers;
+			long newMessages = newStatistics.TotalMessages - oldStatistics.TotalMessages;
 
 			StringBuilder message = new StringBuilder();
 			message.Append("Processed ");
 
-			if (successful == total) {
-				message.Append(successful.Pluralize("database file"));
+			if (successfulItems == totalItems) {
+				message.Append(successfulItems.Pluralize(itemName));
 			}
 			else {
-				message.Append(successful.Format()).Append(" out of ").Append(total.Pluralize("database file"));
+				message.Append(successfulItems.Format()).Append(" out of ").Append(totalItems.Pluralize(itemName));
 			}
 
 			message.Append(" and added:\n\n  \u2022 ");
 			message.Append(newServers.Pluralize("server")).Append("\n  \u2022 ");
 			message.Append(newChannels.Pluralize("channel")).Append("\n  \u2022 ");
+			message.Append(newUsers.Pluralize("user")).Append("\n  \u2022 ");
 			message.Append(newMessages.Pluralize("message"));
 
-			await Dialog.ShowOk(dialog, "Database Merge", message.ToString());
+			return message.ToString();
 		}
 	}
 }

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -11,9 +11,11 @@ using Avalonia.Controls;
 using DHT.Desktop.Common;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Main.Controls;
+using DHT.Desktop.Server;
 using DHT.Server.Data.Filters;
 using DHT.Server.Database;
 using DHT.Server.Database.Export;
+using DHT.Server.Database.Export.Strategy;
 using DHT.Utils.Models;
 using static DHT.Desktop.Program;
 
@@ -55,7 +57,7 @@ namespace DHT.Desktop.Main.Pages {
 			HasFilters = FilterModel.HasAnyFilters;
 		}
 
-		private async Task WriteViewerFile(string path) {
+		private async Task WriteViewerFile(string path, IViewerExportStrategy strategy) {
 			const string ArchiveTag = "/*[ARCHIVE]*/";
 
 			string indexFile = await Resources.ReadTextAsync("Viewer/index.html");
@@ -68,7 +70,7 @@ namespace DHT.Desktop.Main.Pages {
 			string jsonTempFile = path + ".tmp";
 
 			await using (var jsonStream = new FileStream(jsonTempFile, FileMode.Create, FileAccess.ReadWrite, FileShare.Read)) {
-				await ViewerJsonExport.Generate(jsonStream, db, FilterModel.CreateFilter());
+				await ViewerJsonExport.Generate(jsonStream, strategy, db, FilterModel.CreateFilter());
 
 				char[] jsonBuffer = new char[Math.Min(32768, jsonStream.Position)];
 				jsonStream.Position = 0;
@@ -106,7 +108,7 @@ namespace DHT.Desktop.Main.Pages {
 			TemporaryFiles.Add(fullPath);
 			
 			Directory.CreateDirectory(rootPath);
-			await WriteViewerFile(fullPath);
+			await WriteViewerFile(fullPath, new LiveViewerExportStrategy(ServerManager.Port, ServerManager.Token));
 
 			Process.Start(new ProcessStartInfo(fullPath) { UseShellExecute = true });
 		}
@@ -126,7 +128,7 @@ namespace DHT.Desktop.Main.Pages {
 
 			string? path = await dialog;
 			if (!string.IsNullOrEmpty(path)) {
-				await WriteViewerFile(path);
+				await WriteViewerFile(path, StandaloneViewerExportStrategy.Instance);
 			}
 		}
 

app/Resources/Tracker/scripts/discord.js

@@ -91,11 +91,13 @@ class DISCORD {
 	static getMessageElementProps(ele) {
 		const props = DOM.getReactProps(ele);
 		
-		if (props.children && props.children.length >= 4) {
-			const childProps = props.children[3].props;
+		if (props.children && props.children.length) {
+			for (let i = 3; i < props.children.length; i++) {
+				const childProps = props.children[i].props;
 				
-			if ("message" in childProps && "channel" in childProps) {
-				return childProps;
+				if (childProps && "message" in childProps && "channel" in childProps) {
+					return childProps;
+				}
 			}
 		}
 		
@@ -110,16 +112,20 @@ class DISCORD {
 			const messages = [];
 			
 			for (const ele of this.getMessageElements()) {
-				const props = this.getMessageElementProps(ele);
+				try {
+					const props = this.getMessageElementProps(ele);
 					
-				if (props != null) {
-					messages.push(props.message);
+					if (props != null) {
+						messages.push(props.message);
+					}
+				} catch (e) {
+					console.error("[DHT] Error extracing message data, skipping it.", e, ele, DOM.tryGetReactProps(ele));
 				}
 			}
 			
 			return messages;
 		} catch (e) {
-			console.error(e);
+			console.error("[DHT] Error retrieving messages.", e);
 			return [];
 		}
 	}
@@ -191,9 +197,22 @@ class DISCORD {
 				return { server, channel };
 			}
 			else if (obj.guild_id) {
+				let guild;
+				
+				for (const child of DOM.getReactProps(document.querySelector("nav header [class*='headerContent-']")).children) {
+					if (child && child.props && child.props.guild) {
+						guild = child.props.guild;
+						break;
+					}
+				}
+				
+				if (!guild || typeof guild.name !== "string" || obj.guild_id !== guild.id) {
+					return null;
+				}
+				
 				const server = {
-					"id": obj.guild_id,
-					"name": document.querySelector("nav header h1[class*='name-']").innerText,
+					"id": guild.id,
+					"name": guild.name,
 					"type": "SERVER"
 				};
 				

app/Resources/Tracker/scripts/dom.js

@@ -71,4 +71,15 @@ class DOM {
 		key = keys.find(key => key.startsWith("__reactProps$"));
 		return key ? ele[key] : null;
 	}
+	
+	/**
+	 * Returns internal React state object of an element, or null if the retrieval throws.
+	 */
+	static tryGetReactProps(ele) {
+		try {
+			return this.getReactProps(ele);
+		} catch (e) {
+			return null;
+		}
+	}
 }

app/Resources/Tracker/scripts/state.js

@@ -251,6 +251,11 @@ const STATE = (function() {
 							mapped.type = attachment.content_type;
 						}
 						
+						if (attachment.width && attachment.height) {
+							mapped.width = attachment.width;
+							mapped.height = attachment.height;
+						}
+						
 						return mapped;
 					});
 				}

app/Resources/Tracker/styles/controller.css

@@ -1,9 +1,5 @@
-#app-mount div[class*="app-"] {
-  margin-bottom: 48px !important;
-}
-
-#app-mount div[class*="app-"] > div[class*="app-"] {
-  margin-bottom: 0 !important;
+#app-mount {
+  height: calc(100% - 48px) !important;
 }
 
 #dht-ctrl {

app/Resources/Viewer/scripts/discord.js

@@ -1,7 +1,7 @@
 const DISCORD = (function() {
 	const regex = {
 		formatBold: /\*\*([\s\S]+?)\*\*(?!\*)/g,
-		formatItalic: /(.)?\*([\s\S]+?)\*(?!\*)/g,
+		formatItalic: /(.)?([_*])([\s\S]+?)\2(?!\2)/g,
 		formatUnderline: /__([\s\S]+?)__(?!_)/g,
 		formatStrike: /~~([\s\S]+?)~~(?!~)/g,
 		formatCodeInline: /(`+)\s*([\s\S]*?[^`])\s*\1(?!`)/g,
@@ -9,7 +9,7 @@ const DISCORD = (function() {
 		formatUrl: /(\b(?:https?|ftp|file):\/\/[-A-Z0-9+&@#\/%?=~_|!:,.;]*[-A-Z0-9+&@#\/%=~_|])/ig,
 		formatUrlNoEmbed: /<(\b(?:https?|ftp|file):\/\/[-A-Z0-9+&@#\/%?=~_|!:,.;]*[-A-Z0-9+&@#\/%=~_|])>/ig,
 		specialEscapedBacktick: /\\`/g,
-		specialEscapedSingle: /\\([*\\])/g,
+		specialEscapedSingle: /\\([*_\\])/g,
 		specialEscapedDouble: /\\__|_\\_|\\_\\_|\\~~|~\\~|\\~\\~/g,
 		specialUnescaped: /([*_~\\])/g,
 		mentionRole: /&lt;@&(\d+?)&gt;/g,
@@ -26,6 +26,7 @@ const DISCORD = (function() {
 	let templateUserAvatar;
 	let templateAttachmentDownload;
 	let templateEmbedImage;
+	let templateEmbedImageWithSize;
 	let templateEmbedRich;
 	let templateEmbedRichNoDescription;
 	let templateEmbedUrl;
@@ -46,8 +47,8 @@ const DISCORD = (function() {
 				.replace(regex.specialEscapedSingle, escapeHtmlMatch)
 				.replace(regex.specialEscapedDouble, full => full.replace(/\\/g, "").replace(/(.)/g, escapeHtmlMatch))
 				.replace(regex.formatBold, "<b>$1</b>")
-				.replace(regex.formatItalic, (full, pre, match) => pre === "\\" ? full : (pre || "") + "<i>" + match + "</i>")
 				.replace(regex.formatUnderline, "<u>$1</u>")
+				.replace(regex.formatItalic, (full, pre, char, match) => pre === "\\" ? full : (pre || "") + "<i>" + match + "</i>")
 				.replace(regex.formatStrike, "<s>$1</s>");
 		}
 		
@@ -64,6 +65,25 @@ const DISCORD = (function() {
 		return "<p>" + processed + "</p>";
 	};
 	
+	const getImageEmbed = function(url, image) {
+		if (!SETTINGS.enableImagePreviews) {
+			return "";
+		}
+		
+		if (image.width && image.height) {
+			return templateEmbedImageWithSize.apply({ url, src: image.url, width: image.width, height: image.height });
+		}
+		else {
+			return templateEmbedImage.apply({ url, src: image.url });
+		}
+	};
+	
+	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 {
 		setup() {
 			templateChannelServer = new TEMPLATE([
@@ -109,12 +129,17 @@ const DISCORD = (function() {
 			
 			// noinspection HtmlUnknownTarget
 			templateAttachmentDownload = new TEMPLATE([
-				"<a href='{url}' class='embed download'>Download {filename}</a>"
+				"<a href='{url}' class='embed download'>Download {name}</a>"
 			].join(""));
 			
 			// noinspection HtmlUnknownTarget
 			templateEmbedImage = new TEMPLATE([
-				"<a href='{url}' class='embed thumbnail'><img src='{src}' alt='(image attachment not found)'></a><br>"
+				"<a href='{url}' class='embed thumbnail loading'><img src='{src}' alt='' onload='DISCORD.handleImageLoad(this)' onerror='DISCORD.handleImageLoadError(this)'></a><br>"
+			].join(""));
+			
+			// noinspection HtmlUnknownTarget
+			templateEmbedImageWithSize = new TEMPLATE([
+				"<a href='{url}' class='embed thumbnail loading'><img src='{src}' width='{width}' height='{height}' alt='' onload='DISCORD.handleImageLoad(this)' onerror='DISCORD.handleImageLoadError(this)'></a><br>"
 			].join(""));
 			
 			// noinspection HtmlUnknownTarget
@@ -145,10 +170,20 @@ const DISCORD = (function() {
 			].join(""));
 		},
 		
+		handleImageLoad(ele) {
+			ele.parentElement.classList.remove("loading");
+		},
+		
+		handleImageLoadError(ele) {
+			// noinspection JSUnusedGlobalSymbols
+			ele.onerror = null;
+			ele.parentElement.classList.remove("loading");
+			ele.setAttribute("alt", "(image attachment not found)");
+		},
+		
 		isImageAttachment(attachment) {
-			const dot = attachment.url.lastIndexOf(".");
-			const ext = dot === -1 ? "" : attachment.url.substring(dot).toLowerCase();
-			return ext === ".png" || ext === ".gif" || ext === ".jpg" || ext === ".jpeg";
+			const url = DOM.tryParseUrl(attachment.url);
+			return url != null && isImageUrl(url);
 		},
 		
 		getChannelHTML(channel) { // noinspection FunctionWithInconsistentReturnsJS
@@ -183,10 +218,10 @@ const DISCORD = (function() {
 							return templateEmbedUnsupported.apply(embed);
 						}
 						else if ("image" in embed && embed.image.url) {
-							return SETTINGS.enableImagePreviews ? templateEmbedImage.apply({ url: embed.url, src: embed.image.url }) : "";
+							return getImageEmbed(embed.url, embed.image);
 						}
 						else if ("thumbnail" in embed && embed.thumbnail.url) {
-							return SETTINGS.enableImagePreviews ? templateEmbedImage.apply({ url: embed.url, src: embed.thumbnail.url }) : "";
+							return getImageEmbed(embed.url, embed.thumbnail);
 						}
 						else if ("title" in embed && "description" in embed) {
 							return templateEmbedRich.apply(embed);
@@ -205,16 +240,14 @@ const DISCORD = (function() {
 					}
 					
 					return value.map(attachment => {
-						if (this.isImageAttachment(attachment) && SETTINGS.enableImagePreviews) {
-							return templateEmbedImage.apply({ url: attachment.url, src: attachment.url });
+						if (!DISCORD.isImageAttachment(attachment) || !SETTINGS.enableImagePreviews) {
+							return templateAttachmentDownload.apply(attachment);
+						}
+						else if ("width" in attachment && "height" in attachment) {
+							return templateEmbedImageWithSize.apply({ url: attachment.url, src: attachment.url, width: attachment.width, height: attachment.height });
 						}
 						else {
-							const sliced = attachment.url.split("/");
-							
-							return templateAttachmentDownload.apply({
-								"url": attachment.url,
-								"filename": sliced[sliced.length - 1]
-							});
+							return templateEmbedImage.apply({ url: attachment.url, src: attachment.url });
 						}
 					}).join("");
 				}

app/Resources/Viewer/scripts/dom.js

@@ -51,4 +51,15 @@ class DOM {
 		const date = new Date(timestamp);
 		return date.toLocaleDateString() + ", " + date.toLocaleTimeString();
 	};
+	
+	/**
+	 * Parses a url string into a URL object and returns it. If the parsing fails, returns null.
+	 */
+	static tryParseUrl(url) {
+		try {
+			return new URL(url);
+		} catch (ignore) {
+			return null;
+		}
+	}
 }

app/Resources/Viewer/styles/messages.css

@@ -107,11 +107,25 @@
 }
 
 .message .thumbnail {
+  position: relative;
   max-width: calc(100% - 20px);
   max-height: 320px;
 }
 
+.message .thumbnail.loading::after {
+  content: "";
+  background: rgba(0, 0, 0, 0.75)
+              url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 300 300' preserveAspectRatio='xMidYMid'%3E %3Ccircle cx='150' cy='150' fill='none' stroke='%237983f5' stroke-width='8' r='42' stroke-dasharray='198 68'%3E %3CanimateTransform attributeName='transform' type='rotate' repeatCount='indefinite' dur='1.25s' values='0 150 150;360 150 150' keyTimes='0;1' /%3E %3C/circle%3E %3C/svg%3E")
+              no-repeat center center;
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+}
+
 .message .thumbnail img {
+  width: auto;
   max-width: 100%;
   max-height: 320px;
   border-radius: 3px;

app/Server/Data/Attachment.cs

@@ -5,5 +5,7 @@ namespace DHT.Server.Data {
 		public string? Type { get; internal init; }
 		public string Url { get; internal init; }
 		public ulong Size { get; internal init; }
+		public int? Width { get; internal init; }
+		public int? Height { get; internal init; }
 	}
 }

app/Server/Data/Download.cs

@@ -3,10 +3,6 @@ using System.Net;
 
 namespace DHT.Server.Data {
 	public readonly struct Download {
-		internal static Download NewEnqueued(string url, ulong size) {
-			return new Download(url, DownloadStatus.Enqueued, size);
-		}
-
 		internal static Download NewSuccess(string url, byte[] data) {
 			return new Download(url, DownloadStatus.Success, (ulong) Math.Max(data.LongLength, 0), data);
 		}
@@ -20,11 +16,15 @@ namespace DHT.Server.Data {
 		public ulong Size { get; }
 		public byte[]? Data { get; }
 
-		private Download(string url, DownloadStatus status, ulong size, byte[]? data = null) {
+		internal Download(string url, DownloadStatus status, ulong size, byte[]? data = null) {
 			Url = url;
 			Status = status;
 			Size = size;
 			Data = data;
 		}
+
+		internal Download WithData(byte[] data) {
+			return new Download(Url, Status, Size, data);
+		}
 	}
 }

app/Server/Data/DownloadedAttachment.cs

@@ -0,0 +1,6 @@
+namespace DHT.Server.Data {
+	public readonly struct DownloadedAttachment {
+		public string? Type { get; internal init; }
+		public byte[] Data { get; internal init; }
+	}
+}

app/Server/Data/Filters/AttachmentFilter.cs

@@ -1,6 +1,6 @@
 namespace DHT.Server.Data.Filters {
 	public sealed class AttachmentFilter {
-		public long? MaxBytes { get; set; } = null;
+		public ulong? MaxBytes { get; set; } = null;
 
 		public DownloadItemRules? DownloadItemRule { get; set; } = null;
 

app/Server/Data/ServerType.cs

@@ -24,6 +24,15 @@ namespace DHT.Server.Data {
 			};
 		}
 
+		public static string ToNiceString(ServerType? type) {
+			return type switch {
+				ServerType.Server        => "Server",
+				ServerType.Group         => "Group",
+				ServerType.DirectMessage => "DM",
+				_                        => "Unknown"
+			};
+		}
+
 		internal static string ToJsonViewerString(ServerType? type) {
 			return type switch {
 				ServerType.Server        => "server",

app/Server/Database/DatabaseExtensions.cs

@@ -1,16 +1,29 @@
+using System.Collections.Generic;
+using DHT.Server.Data;
+
 namespace DHT.Server.Database {
 	public static class DatabaseExtensions {
 		public static void AddFrom(this IDatabaseFile target, IDatabaseFile source) {
-			foreach (var server in source.GetAllServers()) {
-				target.AddServer(server);
-			}
-
-			foreach (var channel in source.GetAllChannels()) {
-				target.AddChannel(channel);
-			}
-
+			target.AddServers(source.GetAllServers());
+			target.AddChannels(source.GetAllChannels());
 			target.AddUsers(source.GetAllUsers().ToArray());
 			target.AddMessages(source.GetMessages().ToArray());
+			
+			foreach (var download in source.GetDownloadsWithoutData()) {
+				target.AddDownload(download.Status == DownloadStatus.Success ? source.GetDownloadWithData(download) : download);
+			}
+		}
+
+		internal static void AddServers(this IDatabaseFile target, IEnumerable<Data.Server> servers) {
+			foreach (var server in servers) {
+				target.AddServer(server);
+			}
+		}
+
+		internal static void AddChannels(this IDatabaseFile target, IEnumerable<Channel> channels) {
+			foreach (var channel in channels) {
+				target.AddChannel(channel);
+			}
 		}
 	}
 }

app/Server/Database/DatabaseStatistics.cs

@@ -1,12 +1,17 @@
 using DHT.Utils.Models;
 
 namespace DHT.Server.Database {
+	/// <summary>
+	/// A live view of database statistics.
+	/// Some of the totals are computed asynchronously and may not reflect the most recent version of the database, or may not be available at all until computed for the first time.
+	/// </summary>
 	public sealed class DatabaseStatistics : BaseModel {
 		private long totalServers;
 		private long totalChannels;
 		private long totalUsers;
 		private long? totalMessages;
 		private long? totalAttachments;
+		private long? totalDownloads;
 
 		public long TotalServers {
 			get => totalServers;
@@ -33,14 +38,9 @@ namespace DHT.Server.Database {
 			internal set => Change(ref totalAttachments, value);
 		}
 
-		public DatabaseStatistics Clone() {
-			return new DatabaseStatistics {
-				totalServers = totalServers,
-				totalChannels = totalChannels,
-				totalUsers = TotalUsers,
-				totalMessages = totalMessages,
-				totalAttachments = totalAttachments
-			};
+		public long? TotalDownloads {
+			get => totalDownloads;
+			internal set => Change(ref totalDownloads, value);
 		}
 	}
 }

app/Server/Database/DatabaseStatisticsSnapshot.cs

@@ -0,0 +1,11 @@
+namespace DHT.Server.Database {
+	/// <summary>
+	/// A complete snapshot of database statistics at a particular point in time.
+	/// </summary>
+	public readonly struct DatabaseStatisticsSnapshot {
+		public long TotalServers { get; internal init; }
+		public long TotalChannels { get; internal init; }
+		public long TotalUsers { get; internal init; }
+		public long TotalMessages { get; internal init; }
+	}
+}

app/Server/Database/DummyDatabaseFile.cs

@@ -13,6 +13,10 @@ namespace DHT.Server.Database {
 
 		private DummyDatabaseFile() {}
 
+		public DatabaseStatisticsSnapshot SnapshotStatistics() {
+			return new();
+		}
+
 		public void AddServer(Data.Server server) {}
 
 		public List<Data.Server> GetAllServers() {
@@ -41,13 +45,29 @@ namespace DHT.Server.Database {
 			return new();
 		}
 
+		public HashSet<ulong> GetMessageIds(MessageFilter? filter = null) {
+			return new();
+		}
+
 		public void RemoveMessages(MessageFilter filter, FilterRemovalMode mode) {}
 
 		public int CountAttachments(AttachmentFilter? filter = null) {
 			return new();
 		}
 
-		public void AddDownloads(IEnumerable<Data.Download> downloads) {}
+		public List<Data.Download> GetDownloadsWithoutData() {
+			return new();
+		}
+
+		public Data.Download GetDownloadWithData(Data.Download download) {
+			return download;
+		}
+
+		public DownloadedAttachment? GetDownloadedAttachment(string url) {
+			return null;
+		}
+
+		public void AddDownload(Data.Download download) {}
 
 		public void EnqueueDownloadItems(AttachmentFilter? filter = null) {}
 		

app/Server/Database/Export/Strategy/IViewerExportStrategy.cs

@@ -0,0 +1,7 @@
+using DHT.Server.Data;
+
+namespace DHT.Server.Database.Export.Strategy {
+	public interface IViewerExportStrategy {
+		string GetAttachmentUrl(Attachment attachment);
+	}
+}

app/Server/Database/Export/Strategy/LiveViewerExportStrategy.cs

@@ -0,0 +1,18 @@
+using System.Net;
+using DHT.Server.Data;
+
+namespace DHT.Server.Database.Export.Strategy {
+	public sealed class LiveViewerExportStrategy : IViewerExportStrategy {
+		private readonly string safePort;
+		private readonly string safeToken;
+		
+		public LiveViewerExportStrategy(ushort port, string token) {
+			this.safePort = port.ToString();
+			this.safeToken = WebUtility.UrlEncode(token);
+		}
+
+		public string GetAttachmentUrl(Attachment attachment) {
+			return "http://127.0.0.1:" + safePort + "/get-attachment/" + WebUtility.UrlEncode(attachment.Url) + "?token=" + safeToken;
+		}
+	}
+}

app/Server/Database/Export/Strategy/StandaloneViewerExportStrategy.cs

@@ -0,0 +1,13 @@
+using DHT.Server.Data;
+
+namespace DHT.Server.Database.Export.Strategy {
+	public sealed class StandaloneViewerExportStrategy : IViewerExportStrategy {
+		public static StandaloneViewerExportStrategy Instance { get; } = new ();
+
+		private StandaloneViewerExportStrategy() {}
+
+		public string GetAttachmentUrl(Attachment attachment) {
+			return attachment.Url;
+		}
+	}
+}

app/Server/Database/Export/ViewerJsonExport.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -5,13 +6,14 @@ using System.Text.Json;
 using System.Threading.Tasks;
 using DHT.Server.Data;
 using DHT.Server.Data.Filters;
+using DHT.Server.Database.Export.Strategy;
 using DHT.Utils.Logging;
 
 namespace DHT.Server.Database.Export {
 	public static class ViewerJsonExport {
 		private static readonly Log Log = Log.ForType(typeof(ViewerJsonExport));
 
-		public static async Task Generate(Stream stream, IDatabaseFile db, MessageFilter? filter = null) {
+		public static async Task Generate(Stream stream, IViewerExportStrategy strategy, IDatabaseFile db, MessageFilter? filter = null) {
 			var perf = Log.Start();
 
 			var includedUserIds = new HashSet<ulong>();
@@ -41,7 +43,7 @@ namespace DHT.Server.Database.Export {
 
 			var value = new {
 				meta = new { users, userindex, servers, channels },
-				data = GenerateMessageList(includedMessages, userIndices)
+				data = GenerateMessageList(includedMessages, userIndices, strategy)
 			};
 			
 			perf.Step("Generate value object");
@@ -138,7 +140,7 @@ namespace DHT.Server.Database.Export {
 			return channels;
 		}
 
-		private static object GenerateMessageList(List<Message> includedMessages, Dictionary<ulong, object> userIndices) {
+		private static object GenerateMessageList( List<Message> includedMessages, Dictionary<ulong, object> userIndices, IViewerExportStrategy strategy) {
 			var data = new Dictionary<string, Dictionary<string, object>>();
 
 			foreach (var grouping in includedMessages.GroupBy(static message => message.Channel)) {
@@ -164,8 +166,18 @@ namespace DHT.Server.Database.Export {
 					}
 
 					if (!message.Attachments.IsEmpty) {
-						obj["a"] = message.Attachments.Select(static attachment => new Dictionary<string, object> {
-							{ "url", attachment.Url }
+						obj["a"] = message.Attachments.Select(attachment => {
+							var a = new Dictionary<string, object> {
+								{ "url", strategy.GetAttachmentUrl(attachment) },
+								{ "name", Uri.TryCreate(attachment.Url, UriKind.Absolute, out var uri) ? Path.GetFileName(uri.LocalPath) : attachment.Url }
+							};
+
+							if (attachment.Width != null && attachment.Height != null) {
+								a["width"] = attachment.Width;
+								a["height"] = attachment.Height;
+							}
+							
+							return a;
 						}).ToArray();
 					}
 
@@ -188,7 +200,7 @@ namespace DHT.Server.Database.Export {
 							r["a"] = reaction.EmojiFlags.HasFlag(EmojiFlags.Animated);
 							r["c"] = reaction.Count;
 							return r;
-						});
+						}).ToArray();
 					}
 
 					channelData[message.Id.ToString()] = obj;

app/Server/Database/IDatabaseFile.cs

@@ -9,6 +9,7 @@ namespace DHT.Server.Database {
 	public interface IDatabaseFile : IDisposable {
 		string Path { get; }
 		DatabaseStatistics Statistics { get; }
+		DatabaseStatisticsSnapshot SnapshotStatistics();
 
 		void AddServer(Data.Server server);
 		List<Data.Server> GetAllServers();
@@ -22,11 +23,16 @@ namespace DHT.Server.Database {
 		void AddMessages(Message[] messages);
 		int CountMessages(MessageFilter? filter = null);
 		List<Message> GetMessages(MessageFilter? filter = null);
+		HashSet<ulong> GetMessageIds(MessageFilter? filter = null);
 		void RemoveMessages(MessageFilter filter, FilterRemovalMode mode);
 
 		int CountAttachments(AttachmentFilter? filter = null);
 
-		void AddDownloads(IEnumerable<Data.Download> downloads);
+		void AddDownload(Data.Download download);
+		List<Data.Download> GetDownloadsWithoutData();
+		Data.Download GetDownloadWithData(Data.Download download);
+		DownloadedAttachment? GetDownloadedAttachment(string url);
+
 		void EnqueueDownloadItems(AttachmentFilter? filter = null);
 		List<DownloadItem> GetEnqueuedDownloadItems(int count);
 		void RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode);

app/Server/Database/Import/FakeSnowflake.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace DHT.Server.Database.Import {
+	/// <summary>
+	/// https://discord.com/developers/docs/reference#snowflakes
+	/// </summary>
+	public sealed class FakeSnowflake {
+		private const ulong DiscordEpoch = 1420070400000UL;
+			
+		private ulong id;
+
+		public FakeSnowflake() {
+			var unixMillis = (ulong) (DateTime.UtcNow.Subtract(DateTime.UnixEpoch).Ticks / TimeSpan.TicksPerMillisecond);
+			this.id = (unixMillis - DiscordEpoch) << 22;
+		}
+
+		internal ulong Next() {
+			return id++;
+		}
+	}
+}

app/Server/Database/Import/LegacyArchiveImport.cs

@@ -0,0 +1,263 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Linq;
+using System.Text.Json;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Utils.Collections;
+using DHT.Utils.Http;
+using DHT.Utils.Logging;
+using Microsoft.AspNetCore.StaticFiles;
+
+namespace DHT.Server.Database.Import {
+	public static class LegacyArchiveImport {
+		private static readonly Log Log = Log.ForType(typeof(LegacyArchiveImport));
+
+		private static readonly FileExtensionContentTypeProvider ContentTypeProvider = new ();
+
+		public static async Task<bool> Read(Stream stream, IDatabaseFile db, FakeSnowflake fakeSnowflake, Func<Data.Server[], Task<Dictionary<Data.Server, ulong>?>> askForServerIds) {
+			var perf = Log.Start();
+			var root = await JsonSerializer.DeserializeAsync<JsonElement>(stream);
+
+			try {
+				var meta = root.RequireObject("meta");
+				var data = root.RequireObject("data");
+
+				perf.Step("Deserialize JSON");
+
+				var users = ReadUserList(meta);
+				var servers = ReadServerList(meta, fakeSnowflake);
+
+				var newServersOnly = new HashSet<Data.Server>(servers);
+				var oldServersById = db.GetAllServers().ToDictionary(static server => server.Id, static server => server);
+
+				var oldChannels = db.GetAllChannels();
+				var oldChannelsById = oldChannels.ToDictionary(static channel => channel.Id, static channel => channel);
+
+				foreach (var (channelId, serverIndex) in ReadChannelToServerIndexMapping(meta, servers)) {
+					if (oldChannelsById.TryGetValue(channelId, out var oldChannel) && oldServersById.TryGetValue(oldChannel.Server, out var oldServer) && newServersOnly.Remove(servers[serverIndex])) {
+						servers[serverIndex] = oldServer;
+					}
+				}
+
+				perf.Step("Read server and user list");
+
+				if (newServersOnly.Count > 0) {
+					var askedServerIds = await askForServerIds(newServersOnly.ToArray());
+					if (askedServerIds == null) {
+						return false;
+					}
+
+					perf.Step("Ask for server IDs");
+
+					for (var i = 0; i < servers.Length; i++) {
+						var server = servers[i];
+						if (askedServerIds.TryGetValue(server, out var serverId)) {
+							servers[i] = new Data.Server {
+								Id = serverId,
+								Name = server.Name,
+								Type = server.Type
+							};
+						}
+					}
+				}
+
+				var channels = ReadChannelList(meta, servers);
+
+				perf.Step("Read channel list");
+
+				var oldMessageIds = db.GetMessageIds();
+				var newMessages = channels.SelectMany(channel => ReadMessages(data, channel, users, fakeSnowflake))
+				                          .Where(message => !oldMessageIds.Contains(message.Id))
+				                          .ToArray();
+
+				perf.Step("Read messages");
+
+				db.AddUsers(users);
+				db.AddServers(servers);
+				db.AddChannels(channels);
+				db.AddMessages(newMessages);
+
+				perf.Step("Import into database");
+			} catch (HttpException e) {
+				throw new JsonException(e.Message);
+			}
+
+			perf.End();
+			return true;
+		}
+
+		private static User[] ReadUserList(JsonElement meta) {
+			const string UsersPath = "meta.users[]";
+
+			static ulong ParseUserIndex(JsonElement element, int index) {
+				return ulong.Parse(element.GetString() ?? throw new JsonException("Expected key 'meta.userindex[" + index + "]' to be a string."));
+			}
+
+			var userindex = meta.RequireArray("userindex", "meta")
+			                    .Select(static (item, index) => (ParseUserIndex(item, index), index))
+			                    .ToDictionary();
+
+			var users = new User[userindex.Count];
+
+			foreach (var item in meta.RequireObject("users", "meta").EnumerateObject()) {
+				var path = UsersPath + "." + item.Name;
+				var userId = ulong.Parse(item.Name);
+				var userObj = item.Value;
+
+				users[userindex[userId]] = new User {
+					Id = userId,
+					Name = userObj.RequireString("name", path),
+					AvatarUrl = userObj.HasKey("avatar") ? userObj.RequireString("avatar", path) : null,
+					Discriminator = userObj.HasKey("tag") ? userObj.RequireString("tag", path) : null
+				};
+			}
+
+			return users;
+		}
+
+		private static Data.Server[] ReadServerList(JsonElement meta, FakeSnowflake fakeSnowflake) {
+			const string ServersPath = "meta.servers[]";
+
+			return meta.RequireArray("servers", "meta").Select(serverObj => new Data.Server {
+				Id = fakeSnowflake.Next(),
+				Name = serverObj.RequireString("name", ServersPath),
+				Type = ServerTypes.FromString(serverObj.RequireString("type", ServersPath))
+			}).ToArray();
+		}
+
+		private const string ChannelsPath = "meta.channels";
+
+		private static Dictionary<ulong, int> ReadChannelToServerIndexMapping(JsonElement meta, Data.Server[] servers) {
+			return meta.RequireObject("channels", "meta").EnumerateObject().Select(item => {
+				var path = ChannelsPath + "." + item.Name;
+				var channelId = ulong.Parse(item.Name);
+				var channelObj = item.Value;
+
+				return (channelId, channelObj.RequireInt("server", path, min: 0, max: servers.Length - 1));
+			}).ToDictionary();
+		}
+
+		private static Channel[] ReadChannelList(JsonElement meta, Data.Server[] servers) {
+			return meta.RequireObject("channels", "meta").EnumerateObject().Select(item => {
+				var path = ChannelsPath + "." + item.Name;
+				var channelId = ulong.Parse(item.Name);
+				var channelObj = item.Value;
+
+				return new Channel {
+					Id = channelId,
+					Server = servers[channelObj.RequireInt("server", path, min: 0, max: servers.Length - 1)].Id,
+					Name = channelObj.RequireString("name", path),
+					Position = channelObj.HasKey("position") ? channelObj.RequireInt("position", path, min: 0) : null,
+					Topic = channelObj.HasKey("topic") ? channelObj.RequireString("topic", path) : null,
+					Nsfw = channelObj.HasKey("nsfw") ? channelObj.RequireBool("nsfw", path) : null
+				};
+			}).ToArray();
+		}
+
+		private static Message[] ReadMessages(JsonElement data, Channel channel, User[] users, FakeSnowflake fakeSnowflake) {
+			const string DataPath = "data";
+
+			var channelId = channel.Id;
+			var channelIdStr = channelId.ToString();
+
+			var messagesObj = data.HasKey(channelIdStr) ? data.RequireObject(channelIdStr, DataPath) : (JsonElement?) null;
+			if (messagesObj == null) {
+				return Array.Empty<Message>();
+			}
+
+			return messagesObj.Value.EnumerateObject().Select(item => {
+				var path = DataPath + "." + item.Name;
+				var messageId = ulong.Parse(item.Name);
+				var messageObj = item.Value;
+
+				return new Message {
+					Id = messageId,
+					Sender = users[messageObj.RequireInt("u", path, min: 0, max: users.Length - 1)].Id,
+					Channel = channelId,
+					Text = messageObj.HasKey("m") ? messageObj.RequireString("m", path) : string.Empty,
+					Timestamp = messageObj.RequireLong("t", path),
+					EditTimestamp = messageObj.HasKey("te") ? messageObj.RequireLong("te", path) : null,
+					RepliedToId = messageObj.HasKey("r") ? messageObj.RequireSnowflake("r", path) : null,
+					Attachments = messageObj.HasKey("a") ? ReadMessageAttachments(messageObj.RequireArray("a", path), fakeSnowflake, path + ".a[]").ToImmutableArray() : ImmutableArray<Attachment>.Empty,
+					Embeds = messageObj.HasKey("e") ? ReadMessageEmbeds(messageObj.RequireArray("e", path), path + ".e[]").ToImmutableArray() : ImmutableArray<Embed>.Empty,
+					Reactions = messageObj.HasKey("re") ? ReadMessageReactions(messageObj.RequireArray("re", path), path + ".re[]").ToImmutableArray() : ImmutableArray<Reaction>.Empty
+				};
+			}).ToArray();
+		}
+
+		[SuppressMessage("ReSharper", "ConvertToLambdaExpression")]
+		private static IEnumerable<Attachment> ReadMessageAttachments(JsonElement.ArrayEnumerator attachmentsArray, FakeSnowflake fakeSnowflake, string path) {
+			return attachmentsArray.Select(attachmentObj => {
+				string url = attachmentObj.RequireString("url", path);
+				string name = url[(url.LastIndexOf('/') + 1)..];
+				string? type = ContentTypeProvider.TryGetContentType(name, out var contentType) ? contentType : null;
+
+				return new Attachment {
+					Id = fakeSnowflake.Next(),
+					Name = name,
+					Type = type,
+					Url = url,
+					Size = 0 // unknown size
+				};
+			}).DistinctByKeyStable(static attachment => {
+				// Some Discord messages have duplicate attachments with the same id for unknown reasons.
+				return attachment.Id;
+			});
+		}
+
+		private static IEnumerable<Embed> ReadMessageEmbeds(JsonElement.ArrayEnumerator embedsArray, string path) {
+			// Some rich embeds are missing URLs which causes a missing 'url' key.
+			return embedsArray.Where(static embedObj => embedObj.HasKey("url")).Select(embedObj => {
+				string url = embedObj.RequireString("url", path);
+				string type = embedObj.RequireString("type", path);
+
+				var embedJson = new Dictionary<string, object> {
+					{ "url", url },
+					{ "type", type },
+					{ "dht_legacy", true }
+				};
+
+				if (type == "image") {
+					embedJson["image"] = new Dictionary<string, string> {
+						{ "url", url }
+					};
+				}
+				else if (type == "rich") {
+					if (embedObj.HasKey("t")) {
+						embedJson["title"] = embedObj.RequireString("t", path);
+					}
+
+					if (embedObj.HasKey("d")) {
+						embedJson["description"] = embedObj.RequireString("d", path);
+					}
+				}
+
+				return new Embed {
+					Json = JsonSerializer.Serialize(embedJson)
+				};
+			});
+		}
+
+		private static IEnumerable<Reaction> ReadMessageReactions(JsonElement.ArrayEnumerator reactionsArray, string path) {
+			return reactionsArray.Select(reactionObj => {
+				var id = reactionObj.HasKey("id") ? reactionObj.RequireSnowflake("id", path) : (ulong?) null;
+				var name = reactionObj.HasKey("n") ? reactionObj.RequireString("n", path) : null;
+
+				if (id == null && name == null) {
+					throw new JsonException("Expected key '" + path + ".id' and/or '" + path + ".n' to be present.");
+				}
+
+				return new Reaction {
+					EmojiId = id,
+					EmojiName = name,
+					EmojiFlags = reactionObj.HasKey("an") && reactionObj.RequireBool("an", path) ? EmojiFlags.Animated : EmojiFlags.None,
+					Count = reactionObj.RequireInt("c", path, min: 0)
+				};
+			});
+		}
+	}
+}

app/Server/Database/Sqlite/Schema.cs

@@ -6,7 +6,7 @@ using DHT.Utils.Logging;
 
 namespace DHT.Server.Database.Sqlite {
 	sealed class Schema {
-		internal const int Version = 4;
+		internal const int Version = 5;
 
 		private static readonly Log Log = Log.ForType<Schema>();
 
@@ -79,7 +79,9 @@ namespace DHT.Server.Database.Sqlite {
 			        name TEXT NOT NULL,
 			        type TEXT,
 			        url TEXT NOT NULL,
-			        size INTEGER NOT NULL)");
+			        size INTEGER NOT NULL,
+			        width INTEGER,
+			        height INTEGER)");
 
 			Execute(@"CREATE TABLE embeds (
 			        message_id INTEGER NOT NULL,
@@ -159,6 +161,12 @@ namespace DHT.Server.Database.Sqlite {
 				perf.Step("Upgrade to version 4");
 			}
 
+			if (dbVersion <= 4) {
+				Execute("ALTER TABLE attachments ADD width INTEGER");
+				Execute("ALTER TABLE attachments ADD height INTEGER");
+				perf.Step("Upgrade to version 5");
+			}
+
 			perf.End();
 		}
 	}

app/Server/Database/Sqlite/SqliteDatabaseFile.cs

@@ -24,14 +24,19 @@ namespace DHT.Server.Database.Sqlite {
 			};
 
 			var pool = new SqliteConnectionPool(connectionString, DefaultPoolSize);
+			bool wasOpened;
 
 			using (var conn = pool.Take()) {
-				if (!await new Schema(conn).Setup(checkCanUpgradeSchemas)) {
-					return null;
-				}
+				wasOpened = await new Schema(conn).Setup(checkCanUpgradeSchemas);
 			}
 
-			return new SqliteDatabaseFile(path, pool);
+			if (wasOpened) {
+				return new SqliteDatabaseFile(path, pool);
+			}
+			else {
+				pool.Dispose();
+				return null;
+			}
 		}
 
 		public string Path { get; }
@@ -41,6 +46,7 @@ namespace DHT.Server.Database.Sqlite {
 		private readonly SqliteConnectionPool pool;
 		private readonly AsyncValueComputer<long>.Single totalMessagesComputer;
 		private readonly AsyncValueComputer<long>.Single totalAttachmentsComputer;
+		private readonly AsyncValueComputer<long>.Single totalDownloadsComputer;
 
 		private SqliteDatabaseFile(string path, SqliteConnectionPool pool) {
 			this.log = Log.ForType(typeof(SqliteDatabaseFile), System.IO.Path.GetFileName(path));
@@ -48,6 +54,7 @@ namespace DHT.Server.Database.Sqlite {
 			
 			this.totalMessagesComputer = AsyncValueComputer<long>.WithResultProcessor(UpdateMessageStatistics).WithOutdatedResults().BuildWithComputer(ComputeMessageStatistics);
 			this.totalAttachmentsComputer = AsyncValueComputer<long>.WithResultProcessor(UpdateAttachmentStatistics).WithOutdatedResults().BuildWithComputer(ComputeAttachmentStatistics);
+			this.totalDownloadsComputer = AsyncValueComputer<long>.WithResultProcessor(UpdateDownloadStatistics).WithOutdatedResults().BuildWithComputer(ComputeDownloadStatistics);
 
 			this.Path = path;
 			this.Statistics = new DatabaseStatistics();
@@ -60,12 +67,22 @@ namespace DHT.Server.Database.Sqlite {
 
 			totalMessagesComputer.Recompute();
 			totalAttachmentsComputer.Recompute();
+			totalDownloadsComputer.Recompute();
 		}
 
 		public void Dispose() {
 			pool.Dispose();
 		}
 
+		public DatabaseStatisticsSnapshot SnapshotStatistics() {
+			return new DatabaseStatisticsSnapshot {
+				TotalServers = Statistics.TotalServers,
+				TotalChannels = Statistics.TotalChannels,
+				TotalUsers = Statistics.TotalUsers,
+				TotalMessages = ComputeMessageStatistics()
+			};
+		}
+
 		public void AddServer(Data.Server server) {
 			using var conn = pool.Take();
 			using var cmd = conn.Upsert("servers", new[] {
@@ -235,7 +252,9 @@ namespace DHT.Server.Database.Sqlite {
 					("name", SqliteType.Text),
 					("type", SqliteType.Text),
 					("url", SqliteType.Text),
-					("size", SqliteType.Integer)
+					("size", SqliteType.Integer),
+					("width", SqliteType.Integer),
+					("height", SqliteType.Integer)
 				});
 
 				using var embedCmd = conn.Insert("embeds", new[] {
@@ -290,6 +309,8 @@ namespace DHT.Server.Database.Sqlite {
 							attachmentCmd.Set(":type", attachment.Type);
 							attachmentCmd.Set(":url", attachment.Url);
 							attachmentCmd.Set(":size", attachment.Size);
+							attachmentCmd.Set(":width", attachment.Width);
+							attachmentCmd.Set(":height", attachment.Height);
 							attachmentCmd.ExecuteNonQuery();
 						}
 					}
@@ -369,31 +390,41 @@ LEFT JOIN replied_to rt ON m.message_id = rt.message_id" + filter.GenerateWhereC
 			return list;
 		}
 
-		public void RemoveMessages(MessageFilter filter, FilterRemovalMode mode) {
-			var whereClause = filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching);
+		public HashSet<ulong> GetMessageIds(MessageFilter? filter = null) {
+			var perf = log.Start();
+			var ids = new HashSet<ulong>();
 
-			if (!string.IsNullOrEmpty(whereClause)) {
-				var perf = log.Start();
+			using var conn = pool.Take();
+			using var cmd = conn.Command("SELECT message_id FROM messages" + filter.GenerateWhereClause());
+			using var reader = cmd.ExecuteReader();
 
-				DeleteFromTable("messages", whereClause);
-				totalMessagesComputer.Recompute();
-				
-				perf.End();
+			while (reader.Read()) {
+				ids.Add(reader.GetUint64(0));
 			}
+
+			perf.End();
+			return ids;
+		}
+
+		public void RemoveMessages(MessageFilter filter, FilterRemovalMode mode) {
+			var perf = log.Start();
+
+			DeleteFromTable("messages", filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching));
+			totalMessagesComputer.Recompute();
+
+			perf.End();
 		}
 
 		public int CountAttachments(AttachmentFilter? filter = null) {
 			using var conn = pool.Take();
-			using var cmd = conn.Command("SELECT COUNT(*) FROM attachments a" + filter.GenerateWhereClause("a"));
+			using var cmd = conn.Command("SELECT COUNT(DISTINCT url) FROM attachments a" + filter.GenerateWhereClause("a"));
 			using var reader = cmd.ExecuteReader();
 
 			return reader.Read() ? reader.GetInt32(0) : 0;
 		}
 
-		public void AddDownloads(IEnumerable<Data.Download> downloads) {
+		public void AddDownload(Data.Download download) {
 			using var conn = pool.Take();
-			using var tx = conn.BeginTransaction();
-
 			using var cmd = conn.Upsert("downloads", new[] {
 				("url", SqliteType.Text),
 				("status", SqliteType.Integer),
@@ -401,20 +432,73 @@ LEFT JOIN replied_to rt ON m.message_id = rt.message_id" + filter.GenerateWhereC
 				("blob", SqliteType.Blob)
 			});
 
-			foreach (var download in downloads) {
-				cmd.Set(":url", download.Url);
-				cmd.Set(":status", (int) download.Status);
-				cmd.Set(":size", download.Size);
-				cmd.Set(":blob", download.Data);
-				cmd.ExecuteNonQuery();
+			cmd.Set(":url", download.Url);
+			cmd.Set(":status", (int) download.Status);
+			cmd.Set(":size", download.Size);
+			cmd.Set(":blob", download.Data);
+			cmd.ExecuteNonQuery();
+			
+			totalDownloadsComputer.Recompute();
+		}
+
+		public List<Data.Download> GetDownloadsWithoutData() {
+			var list = new List<Data.Download>();
+			
+			using var conn = pool.Take();
+			using var cmd = conn.Command("SELECT url, status, size FROM downloads");
+			using var reader = cmd.ExecuteReader();
+			
+			while (reader.Read()) {
+				string url = reader.GetString(0);
+				var status = (DownloadStatus) reader.GetInt32(1);
+				ulong size = reader.GetUint64(2);
+				
+				list.Add(new Data.Download(url, status, size));
 			}
 			
-			tx.Commit();
+			return list;
+		}
+
+		public Data.Download GetDownloadWithData(Data.Download download) {
+			using var conn = pool.Take();
+			using var cmd = conn.Command("SELECT blob FROM downloads WHERE url = :url");
+			cmd.AddAndSet(":url", SqliteType.Text, download.Url);
+			
+			using var reader = cmd.ExecuteReader();
+
+			if (reader.Read() && !reader.IsDBNull(0)) {
+				return download.WithData((byte[]) reader["blob"]);
+			}
+			else {
+				return download;
+			}
+		}
+
+		public DownloadedAttachment? GetDownloadedAttachment(string url) {
+			using var conn = pool.Take();
+			using var cmd = conn.Command(@"
+SELECT a.type, d.blob FROM downloads d
+LEFT JOIN attachments a ON d.url = a.url
+WHERE d.url = :url AND d.status = :success AND d.blob IS NOT NULL");
+			
+			cmd.AddAndSet(":url", SqliteType.Text, url);
+			cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
+			
+			using var reader = cmd.ExecuteReader();
+
+			if (!reader.Read()) {
+				return null;
+			}
+			
+			return new DownloadedAttachment {
+				Type = reader.IsDBNull(0) ? null : reader.GetString(0),
+				Data = (byte[]) reader["blob"]
+			};
 		}
 
 		public void EnqueueDownloadItems(AttachmentFilter? filter = null) {
 			using var conn = pool.Take();
-			using var cmd = conn.Command("INSERT INTO downloads (url, status, size) SELECT a.url, :enqueued, a.size FROM attachments a" + filter.GenerateWhereClause("a"));
+			using var cmd = conn.Command("INSERT INTO downloads (url, status, size) SELECT a.url, :enqueued, MAX(a.size) FROM attachments a" + filter.GenerateWhereClause("a") + " GROUP BY a.url");
 			cmd.AddAndSet(":enqueued", SqliteType.Integer, (int) DownloadStatus.Enqueued);
 			cmd.ExecuteNonQuery();
 		}
@@ -440,16 +524,13 @@ LEFT JOIN replied_to rt ON m.message_id = rt.message_id" + filter.GenerateWhereC
 		}
 
 		public void RemoveDownloadItems(DownloadItemFilter? filter, FilterRemovalMode mode) {
-			var whereClause = filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching);
-			
-			if (!string.IsNullOrEmpty(whereClause)) {
-				DeleteFromTable("downloads", whereClause);
-			}
+			DeleteFromTable("downloads", filter.GenerateWhereClause(invert: mode == FilterRemovalMode.KeepMatching));
+			totalDownloadsComputer.Recompute();
 		}
 
 		public DownloadStatusStatistics GetDownloadStatusStatistics() {
 			static void LoadUndownloadedStatistics(ISqliteConnection conn, DownloadStatusStatistics result) {
-				using var cmd = conn.Command("SELECT IFNULL(COUNT(filtered.size), 0), IFNULL(SUM(filtered.size), 0) FROM (SELECT DISTINCT a.url, a.size FROM attachments a  WHERE a.url NOT IN (SELECT d.url FROM downloads d)) filtered");
+				using var cmd = conn.Command("SELECT IFNULL(COUNT(size), 0), IFNULL(SUM(size), 0) FROM (SELECT MAX(a.size) size FROM attachments a WHERE a.url NOT IN (SELECT d.url FROM downloads d) GROUP BY a.url)");
 				using var reader = cmd.ExecuteReader();
 
 				if (reader.Read()) {
@@ -494,7 +575,7 @@ FROM downloads");
 			var dict = new MultiDictionary<ulong, Attachment>();
 
 			using var conn = pool.Take();
-			using var cmd = conn.Command("SELECT message_id, attachment_id, name, type, url, size FROM attachments");
+			using var cmd = conn.Command("SELECT message_id, attachment_id, name, type, url, size, width, height FROM attachments");
 			using var reader = cmd.ExecuteReader();
 
 			while (reader.Read()) {
@@ -505,7 +586,9 @@ FROM downloads");
 					Name = reader.GetString(2),
 					Type = reader.IsDBNull(3) ? null : reader.GetString(3),
 					Url = reader.GetString(4),
-					Size = reader.GetUint64(5)
+					Size = reader.GetUint64(5),
+					Width = reader.IsDBNull(6) ? null : reader.GetInt32(6),
+					Height = reader.IsDBNull(7) ? null : reader.GetInt32(7)
 				});
 			}
 
@@ -593,11 +676,20 @@ FROM downloads");
 
 		private long ComputeAttachmentStatistics() {
 			using var conn = pool.Take();
-			return conn.SelectScalar("SELECT COUNT(*) FROM attachments") as long? ?? 0L;
+			return conn.SelectScalar("SELECT COUNT(DISTINCT url) FROM attachments") as long? ?? 0L;
 		}
 
 		private void UpdateAttachmentStatistics(long totalAttachments) {
 			Statistics.TotalAttachments = totalAttachments;
 		}
+
+		private long ComputeDownloadStatistics() {
+			using var conn = pool.Take();
+			return conn.SelectScalar("SELECT COUNT(*) FROM downloads") as long? ?? 0L;
+		}
+
+		private void UpdateDownloadStatistics(long totalDownloads) {
+			Statistics.TotalDownloads = totalDownloads;
+		}
 	}
 }

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

@@ -45,22 +45,21 @@ namespace DHT.Server.Database.Sqlite.Utils {
 		}
 
 		public ISqliteConnection Take() {
-			PooledConnection? conn = null;
-			
-			while (conn == null) {
+			while (true) {
 				ThrowIfDisposed();
+				
 				lock (monitor) {
-					if (free.TryTake(out conn, TimeSpan.FromMilliseconds(rand.Next(100, 200)))) {
+					if (free.TryTake(out var conn)) {
 						used.Add(conn);
-						break;
+						return conn;
 					}
 					else {
 						Log.ForType<SqliteConnectionPool>().Warn("Thread " + Thread.CurrentThread.ManagedThreadId + " is starving for connections.");
 					}
 				}
-			}
 				
-			return conn;
+				Thread.Sleep(TimeSpan.FromMilliseconds(rand.Next(100, 200)));
+			}
 		}
 
 		private void Return(PooledConnection conn) {

app/Server/Download/BackgroundDownloadThread.cs

@@ -92,9 +92,9 @@ namespace DHT.Server.Download {
 							Log.Debug("Downloading " + url + "...");
 
 							try {
-								db.AddDownloads(new [] { Data.Download.NewSuccess(url, client.DownloadData(url)) });
+								db.AddDownload(Data.Download.NewSuccess(url, client.DownloadData(url)));
 							} catch (WebException e) {
-								db.AddDownloads(new [] { Data.Download.NewFailure(url, e.Response is HttpWebResponse response ? response.StatusCode : null, item.Size) });
+								db.AddDownload(Data.Download.NewFailure(url, e.Response is HttpWebResponse response ? response.StatusCode : null, item.Size));
 								Log.Error(e);
 							} finally {
 								parameters.FireOnItemFinished(item);

app/Server/Endpoints/BaseEndpoint.cs

@@ -8,6 +8,7 @@ using DHT.Utils.Http;
 using DHT.Utils.Logging;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Extensions;
+using Microsoft.Extensions.Primitives;
 
 namespace DHT.Server.Endpoints {
 	abstract class BaseEndpoint {
@@ -21,26 +22,22 @@ namespace DHT.Server.Endpoints {
 			this.parameters = parameters;
 		}
 
-		public async Task Handle(HttpContext ctx) {
+		private async Task Handle(HttpContext ctx, StringValues token) {
 			var request = ctx.Request;
 			var response = ctx.Response;
 
 			Log.Info("Request: " + request.GetDisplayUrl() + " (" + request.ContentLength + " B)");
 			
-			var requestToken = request.Headers["X-DHT-Token"];
-			if (requestToken.Count != 1 || requestToken[0] != parameters.Token) {
-				Log.Error("Token: " + (requestToken.Count == 1 ? requestToken[0] : "<missing>"));
+			if (token.Count != 1 || token[0] != parameters.Token) {
+				Log.Error("Token: " + (token.Count == 1 ? token[0] : "<missing>"));
 				response.StatusCode = (int) HttpStatusCode.Forbidden;
 				return;
 			}
 
 			try {
-				var (statusCode, output) = await Respond(ctx);
-				response.StatusCode = (int) statusCode;
-
-				if (output != null) {
-					await response.WriteAsJsonAsync(output);
-				}
+				response.StatusCode = (int) HttpStatusCode.OK;
+				var output = await Respond(ctx);
+				await output.WriteTo(response);
 			} catch (HttpException e) {
 				Log.Error(e);
 				response.StatusCode = (int) e.StatusCode;
@@ -51,7 +48,15 @@ namespace DHT.Server.Endpoints {
 			}
 		}
 
-		protected abstract Task<(HttpStatusCode, object?)> Respond(HttpContext ctx);
+		public async Task HandleGet(HttpContext ctx) {
+			await Handle(ctx, ctx.Request.Query["token"]);
+		}
+
+		public async Task HandlePost(HttpContext ctx) {
+			await Handle(ctx, ctx.Request.Headers["X-DHT-Token"]);
+		}
+
+		protected abstract Task<IHttpOutput> Respond(HttpContext ctx);
 
 		protected static async Task<JsonElement> ReadJson(HttpContext ctx) {
 			return await ctx.Request.ReadFromJsonAsync<JsonElement?>() ?? throw new HttpException(HttpStatusCode.UnsupportedMediaType, "This endpoint only accepts JSON.");

app/Server/Endpoints/GetAttachmentEndpoint.cs

@@ -0,0 +1,25 @@
+using System.Net;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Database;
+using DHT.Server.Service;
+using DHT.Utils.Http;
+using Microsoft.AspNetCore.Http;
+
+namespace DHT.Server.Endpoints {
+	sealed class GetAttachmentEndpoint : BaseEndpoint {
+		public GetAttachmentEndpoint(IDatabaseFile db, ServerParameters parameters) : base(db, parameters) {}
+		
+		protected override Task<IHttpOutput> Respond(HttpContext ctx) {
+			string attachmentUrl = WebUtility.UrlDecode((string) ctx.Request.RouteValues["url"]!);
+			DownloadedAttachment? maybeDownloadedAttachment = Db.GetDownloadedAttachment(attachmentUrl);
+
+			if (maybeDownloadedAttachment is {} downloadedAttachment) {
+				return Task.FromResult<IHttpOutput>(new HttpOutput.File(downloadedAttachment.Type, downloadedAttachment.Data));
+			}
+			else {
+				return Task.FromResult<IHttpOutput>(new HttpOutput.Redirect(attachmentUrl, permanent: false));
+			}
+		}
+	}
+}

app/Server/Endpoints/TrackChannelEndpoint.cs

@@ -11,7 +11,7 @@ namespace DHT.Server.Endpoints {
 	sealed class TrackChannelEndpoint : BaseEndpoint {
 		public TrackChannelEndpoint(IDatabaseFile db, ServerParameters parameters) : base(db, parameters) {}
 
-		protected override async Task<(HttpStatusCode, object?)> Respond(HttpContext ctx) {
+		protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
 			var root = await ReadJson(ctx);
 			var server = ReadServer(root.RequireObject("server"), "server");
 			var channel = ReadChannel(root.RequireObject("channel"), "channel", server.Id);
@@ -19,7 +19,7 @@ namespace DHT.Server.Endpoints {
 			Db.AddServer(server);
 			Db.AddChannel(channel);
 
-			return (HttpStatusCode.OK, null);
+			return HttpOutput.None;
 		}
 
 		private static Data.Server ReadServer(JsonElement json, string path) => new() {

app/Server/Endpoints/TrackMessagesEndpoint.cs

@@ -17,7 +17,7 @@ namespace DHT.Server.Endpoints {
 	sealed class TrackMessagesEndpoint : BaseEndpoint {
 		public TrackMessagesEndpoint(IDatabaseFile db, ServerParameters parameters) : base(db, parameters) {}
 
-		protected override async Task<(HttpStatusCode, object?)> Respond(HttpContext ctx) {
+		protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
 			var root = await ReadJson(ctx);
 
 			if (root.ValueKind != JsonValueKind.Array) {
@@ -39,7 +39,7 @@ namespace DHT.Server.Endpoints {
 
 			Db.AddMessages(messages);
 
-			return (HttpStatusCode.OK, anyNewMessages ? 1 : 0);
+			return new HttpOutput.Json(anyNewMessages ? 1 : 0);
 		}
 
 		private static Message ReadMessage(JsonElement json, string path) => new() {
@@ -61,7 +61,9 @@ namespace DHT.Server.Endpoints {
 			Name = ele.RequireString("name", path),
 			Type = ele.HasKey("type") ? ele.RequireString("type", path) : null,
 			Url = ele.RequireString("url", path),
-			Size = (ulong) ele.RequireLong("size", path)
+			Size = (ulong) ele.RequireLong("size", path),
+			Width = ele.HasKey("width") ? ele.RequireInt("width", path) : null,
+			Height = ele.HasKey("height") ? ele.RequireInt("height", path) : null
 		}).DistinctByKeyStable(static attachment => {
 			// Some Discord messages have duplicate attachments with the same id for unknown reasons.
 			return attachment.Id;

app/Server/Endpoints/TrackUsersEndpoint.cs

@@ -11,7 +11,7 @@ namespace DHT.Server.Endpoints {
 	sealed class TrackUsersEndpoint : BaseEndpoint {
 		public TrackUsersEndpoint(IDatabaseFile db, ServerParameters parameters) : base(db, parameters) {}
 
-		protected override async Task<(HttpStatusCode, object?)> Respond(HttpContext ctx) {
+		protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
 			var root = await ReadJson(ctx);
 
 			if (root.ValueKind != JsonValueKind.Array) {
@@ -27,7 +27,7 @@ namespace DHT.Server.Endpoints {
 
 			Db.AddUsers(users);
 
-			return (HttpStatusCode.OK, null);
+			return HttpOutput.None;
 		}
 
 		private static User ReadUser(JsonElement json, string path) => new() {

app/Server/Server.csproj

@@ -20,7 +20,7 @@
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="Microsoft.Data.Sqlite" Version="6.0.5" />
+    <PackageReference Include="Microsoft.Data.Sqlite" Version="6.0.7" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Utils\Utils.csproj" />

app/Server/Service/ServerStartup.cs

@@ -9,6 +9,13 @@ using Microsoft.Extensions.Hosting;
 
 namespace DHT.Server.Service {
 	sealed class Startup {
+		private static readonly string[] AllowedOrigins = {
+			"https://discord.com",
+			"https://ptb.discord.com",
+			"https://canary.discord.com",
+			"https://discordapp.com"
+		};
+
 		public void ConfigureServices(IServiceCollection services) {
 			services.Configure<JsonOptions>(static options => {
 				options.SerializerOptions.NumberHandling = JsonNumberHandling.Strict;
@@ -16,7 +23,7 @@ namespace DHT.Server.Service {
 
 			services.AddCors(static cors => {
 				cors.AddDefaultPolicy(static builder => {
-					builder.WithOrigins("https://discord.com", "https://discordapp.com").AllowCredentials().AllowAnyMethod().AllowAnyHeader();
+					builder.WithOrigins(AllowedOrigins).AllowCredentials().AllowAnyMethod().AllowAnyHeader();
 				});
 			});
 		}
@@ -27,13 +34,16 @@ namespace DHT.Server.Service {
 			app.UseCors();
 			app.UseEndpoints(endpoints => {
 				TrackChannelEndpoint trackChannel = new(db, parameters);
-				endpoints.MapPost("/track-channel", async context => await trackChannel.Handle(context));
+				endpoints.MapPost("/track-channel", async context => await trackChannel.HandlePost(context));
 
 				TrackUsersEndpoint trackUsers = new(db, parameters);
-				endpoints.MapPost("/track-users", async context => await trackUsers.Handle(context));
+				endpoints.MapPost("/track-users", async context => await trackUsers.HandlePost(context));
 
 				TrackMessagesEndpoint trackMessages = new(db, parameters);
-				endpoints.MapPost("/track-messages", async context => await trackMessages.Handle(context));
+				endpoints.MapPost("/track-messages", async context => await trackMessages.HandlePost(context));
+
+				GetAttachmentEndpoint getAttachment = new(db, parameters);
+				endpoints.MapGet("/get-attachment/{url}", async context => await getAttachment.HandleGet(context));
 			});
 		}
 	}

app/Utils/Collections/LinqExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace DHT.Utils.Collections {
 	public static class LinqExtensions {
@@ -14,5 +15,9 @@ namespace DHT.Utils.Collections {
 				}
 			}
 		}
+
+		public static Dictionary<TKey, TValue> ToDictionary<TKey, TValue>(this IEnumerable<(TKey, TValue)> collection) where TKey : notnull {
+			return collection.ToDictionary(static item => item.Item1, static item => item.Item2);
+		}
 	}
 }

app/Utils/Http/HttpOutput.cs

@@ -0,0 +1,56 @@
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+
+namespace DHT.Utils.Http {
+	public static class HttpOutput {
+		public static IHttpOutput None { get; } = new NoneImpl();
+		
+		private sealed class NoneImpl : IHttpOutput {
+			public Task WriteTo(HttpResponse response) {
+				return Task.CompletedTask;
+			}
+		}
+
+		public sealed class Json : IHttpOutput {
+			private readonly object? obj;
+			
+			public Json(object? obj) {
+				this.obj = obj;
+			}
+
+			public Task WriteTo(HttpResponse response) {
+				return response.WriteAsJsonAsync(obj);
+			}
+		}
+
+		public sealed class File : IHttpOutput {
+			private readonly string? contentType;
+			private readonly byte[] bytes;
+			
+			public File(string? contentType, byte[] bytes) {
+				this.contentType = contentType;
+				this.bytes = bytes;
+			}
+
+			public async Task WriteTo(HttpResponse response) {
+				response.ContentType = contentType ?? string.Empty;
+				await response.Body.WriteAsync(bytes);
+			}
+		}
+
+		public sealed class Redirect : IHttpOutput {
+			private readonly string url;
+			private readonly bool permanent;
+
+			public Redirect(string url, bool permanent) {
+				this.url = url;
+				this.permanent = permanent;
+			}
+
+			public Task WriteTo(HttpResponse response) {
+				response.Redirect(url, permanent);
+				return Task.CompletedTask;
+			}
+		}
+	}
+}

app/Utils/Http/IHttpOutput.cs

@@ -0,0 +1,8 @@
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+
+namespace DHT.Utils.Http {
+	public interface IHttpOutput {
+		Task WriteTo(HttpResponse response);
+	}
+}

app/Utils/Utils.csproj

@@ -17,7 +17,10 @@
     <DebugType>none</DebugType>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" Version="10.3.0" />
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="JetBrains.Annotations" Version="2022.1.0" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\Version.cs" Link="Version.cs" />

app/Version.cs

@@ -7,6 +7,6 @@ using DHT.Utils;
 
 namespace DHT.Utils {
 	static class Version {
-		public const string Tag = "36.0.0.0";
+		public const string Tag = "37.2.0.0";
 	}
 }