Add option to export downloaded files

Closes #277

app/Desktop/Dialogs/File/FileDialogs.cs

@@ -8,6 +8,10 @@ using Avalonia.Platform.Storage;
 namespace DHT.Desktop.Dialogs.File;
 
 static class FileDialogs {
+	public static async Task<string[]> OpenFolders(this IStorageProvider storageProvider, FolderPickerOpenOptions options) {
+		return (await storageProvider.OpenFolderPickerAsync(options)).ToLocalPaths();
+	}
+	
 	public static async Task<string[]> OpenFiles(this IStorageProvider storageProvider, FilePickerOpenOptions options) {
 		return (await storageProvider.OpenFilePickerAsync(options)).ToLocalPaths();
 	}
@@ -26,11 +30,11 @@ static class FileDialogs {
 		return suggestedDirectory == null ? Task.FromResult<IStorageFolder?>(null) : window.StorageProvider.TryGetFolderFromPathAsync(suggestedDirectory);
 	}
 	
-	private static string ToLocalPath(this IStorageFile file) {
-		return file.TryGetLocalPath() ?? throw new NotSupportedException("Local filesystem is not supported.");
+	private static string ToLocalPath(this IStorageItem itme) {
+		return itme.TryGetLocalPath() ?? throw new NotSupportedException("Local filesystem is not supported.");
 	}
 	
-	private static string[] ToLocalPaths(this IReadOnlyList<IStorageFile> files) {
-		return files.Select(ToLocalPath).ToArray();
+	private static string[] ToLocalPaths(this IReadOnlyList<IStorageItem> items) {
+		return items.Select(ToLocalPath).ToArray();
 	}
 }

app/Desktop/Dialogs/Progress/IProgressCallback.cs

@@ -3,7 +3,7 @@ using System.Threading.Tasks;
 namespace DHT.Desktop.Dialogs.Progress;
 
 interface IProgressCallback {
-	Task Update(string message, int finishedItems, int totalItems);
+	Task Update(string message, long finishedItems, long totalItems);
 	Task UpdateIndeterminate(string message);
 	Task Hide();
 }

app/Desktop/Dialogs/Progress/ProgressDialog.axaml.cs

@@ -2,7 +2,6 @@ using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
 using Avalonia.Controls;
-using DHT.Desktop.Dialogs.Message;
 using DHT.Utils.Logging;
 
 namespace DHT.Desktop.Dialogs.Progress;
@@ -12,57 +11,37 @@ public sealed partial class ProgressDialog : Window {
 	private static readonly Log Log = Log.ForType<ProgressDialog>();
 	
 	internal static async Task Show(Window owner, string title, Func<ProgressDialog, IProgressCallback, Task> action) {
-		var taskCompletionSource = new TaskCompletionSource();
 		var dialog = new ProgressDialog();
-		
-		dialog.DataContext = new ProgressDialogModel(title, async callbacks => {
-			try {
-				await action(dialog, callbacks[0]);
-				taskCompletionSource.SetResult();
-			} catch (Exception e) {
-				taskCompletionSource.SetException(e);
-			}
-		});
-		
+		dialog.DataContext = new ProgressDialogModel(title, async callbacks => await action(dialog, callbacks[0]));
 		await dialog.ShowProgressDialog(owner);
-		await taskCompletionSource.Task;
 	}
 	
-	internal static async Task ShowIndeterminate(Window owner, string title, string message, Func<ProgressDialog, Task> action) {
-		var taskCompletionSource = new TaskCompletionSource();
-		var dialog = new ProgressDialog();
-		
-		dialog.DataContext = new ProgressDialogModel(title, async callbacks => {
-			await callbacks[0].UpdateIndeterminate(message);
-			try {
-				await action(dialog);
-				taskCompletionSource.SetResult();
-			} catch (Exception e) {
-				taskCompletionSource.SetException(e);
-			}
-		});
-		
-		await dialog.ShowProgressDialog(owner);
-		await taskCompletionSource.Task;
-	}
-	
-	internal static async Task<T> ShowIndeterminate<T>(Window owner, string title, string message, Func<ProgressDialog, Task<T>> action) {
+	internal static async Task<T> Show<T>(Window owner, string title, Func<ProgressDialog, IProgressCallback, Task<T>> action) {
 		var taskCompletionSource = new TaskCompletionSource<T>();
 		var dialog = new ProgressDialog();
 		
 		dialog.DataContext = new ProgressDialogModel(title, async callbacks => {
-			await callbacks[0].UpdateIndeterminate(message);
-			try {
-				taskCompletionSource.SetResult(await action(dialog));
-			} catch (Exception e) {
-				taskCompletionSource.SetException(e);
-			}
+			taskCompletionSource.SetResult(await action(dialog, callbacks[0]));
 		});
 		
 		await dialog.ShowProgressDialog(owner);
 		return await taskCompletionSource.Task;
 	}
 	
+	internal static Task ShowIndeterminate(Window owner, string title, string message, Func<ProgressDialog, Task> action) {
+		return Show(owner, title, async (dialog, callback) => {
+			await callback.UpdateIndeterminate(message);
+			await action(dialog);
+		});
+	}
+	
+	internal static Task<T> ShowIndeterminate<T>(Window owner, string title, string message, Func<ProgressDialog, Task<T>> action) {
+		return Show<T>(owner, title, async (dialog, callback) => {
+			await callback.UpdateIndeterminate(message);
+			return await action(dialog);
+		});
+	}
+	
 	private bool isFinished = false;
 	private Task progressTask = Task.CompletedTask;
 	
@@ -88,11 +67,6 @@ public sealed partial class ProgressDialog : Window {
 	
 	public async Task ShowProgressDialog(Window owner) {
 		await ShowDialog(owner);
-		try {
-			await progressTask;
-		} catch (Exception e) {
-			Log.Error(e);
-			await Dialog.ShowOk(owner, "Unexpected Error", e.Message);
-		}
+		await progressTask;
 	}
 }

app/Desktop/Dialogs/Progress/ProgressDialogModel.cs

@@ -38,7 +38,7 @@ sealed class ProgressDialogModel {
 			this.item = item;
 		}
 		
-		public async Task Update(string message, int finishedItems, int totalItems) {
+		public async Task Update(string message, long finishedItems, long totalItems) {
 			await Dispatcher.UIThread.InvokeAsync(() => {
 				item.Message = message;
 				item.Items = totalItems == 0 ? string.Empty : finishedItems.Format() + " / " + totalItems.Format();

app/Desktop/Dialogs/Progress/ProgressItem.cs

@@ -23,7 +23,7 @@ sealed partial class ProgressItem : ObservableObject {
 	private string items = "";
 	
 	[ObservableProperty]
-	private int progress = 0;
+	private long progress = 0L;
 	
 	[ObservableProperty]
 	private bool isIndeterminate;

app/Desktop/Main/Pages/DatabasePageModel.cs

@@ -74,15 +74,28 @@ sealed class DatabasePageModel {
 	
 	public async Task MergeWithDatabase() {
 		string[] paths = await DatabaseGui.NewOpenDatabaseFilesDialog(window, Path.GetDirectoryName(Db.Path));
-		if (paths.Length > 0) {
-			await ProgressDialog.Show(window, "Database Merge", async (dialog, callback) => await MergeWithDatabaseFromPaths(Db, paths, dialog, callback));
+		if (paths.Length == 0) {
+			return;
 		}
+		
+		const string Title = "Database Merge";
+		
+		ImportResult? result;
+		try {
+			result = await ProgressDialog.Show(window, Title, async (dialog, callback) => await MergeWithDatabaseFromPaths(Db, paths, dialog, callback));
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, Title, "Could not merge databases: " + e.Message);
+			return;
+		}
+		
+		await Dialog.ShowOk(window, Title, GetImportDialogMessage(result, "database file"));
 	}
 	
-	private static async Task MergeWithDatabaseFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
+	private static async Task<ImportResult?> MergeWithDatabaseFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
 		var schemaUpgradeCallbacks = new SchemaUpgradeCallbacks(dialog, paths.Length);
 		
-		await PerformImport(target, paths, dialog, callback, "Database Merge", "Database Error", "database file", async path => {
+		return await PerformImport(target, paths, dialog, callback, "Database Merge", async path => {
 			IDatabaseFile? db = await DatabaseGui.TryOpenOrCreateDatabaseFromPath(path, dialog, schemaUpgradeCallbacks);
 			
 			if (db == null) {
@@ -137,15 +150,28 @@ sealed class DatabasePageModel {
 			AllowMultiple = true,
 		});
 		
-		if (paths.Length > 0) {
-			await ProgressDialog.Show(window, "Legacy Archive Import", async (dialog, callback) => await ImportLegacyArchiveFromPaths(Db, paths, dialog, callback));
+		if (paths.Length == 0) {
+			return;
 		}
+		
+		const string Title = "Legacy Archive Import";
+		
+		ImportResult? result;
+		try {
+			result = await ProgressDialog.Show(window, Title, async (dialog, callback) => await ImportLegacyArchiveFromPaths(Db, paths, dialog, callback));
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, Title, "Could not import legacy archives: " + e.Message);
+			return;
+		}
+		
+		await Dialog.ShowOk(window, Title, GetImportDialogMessage(result, "archive file"));
 	}
 	
-	private static async Task ImportLegacyArchiveFromPaths(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback) {
+	private static async Task<ImportResult?> 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 => {
+		return await PerformImport(target, paths, dialog, callback, "Legacy Archive Import", async path => {
 			await using var jsonStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
 			
 			return await LegacyArchiveImport.Read(jsonStream, target, fakeSnowflake, async servers => {
@@ -189,7 +215,7 @@ sealed class DatabasePageModel {
 		            .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) {
+	private static async Task<ImportResult?> PerformImport(IDatabaseFile target, string[] paths, ProgressDialog dialog, IProgressCallback callback, string dialogTitle, Func<string, Task<bool>> performImport) {
 		int total = paths.Length;
 		DatabaseStatistics oldStatistics = await DatabaseStatistics.Take(target);
 		
@@ -201,7 +227,7 @@ sealed class DatabasePageModel {
 			++finished;
 			
 			if (!File.Exists(path)) {
-				await Dialog.ShowOk(dialog, errorDialogTitle, "File '" + Path.GetFileName(path) + "' no longer exists.");
+				await Dialog.ShowOk(dialog, dialogTitle, "File '" + Path.GetFileName(path) + "' no longer exists.");
 				continue;
 			}
 			
@@ -211,19 +237,18 @@ sealed class DatabasePageModel {
 				}
 			} catch (Exception ex) {
 				Log.Error(ex);
-				await Dialog.ShowOk(dialog, errorDialogTitle, "File '" + Path.GetFileName(path) + "' could not be imported: " + ex.Message);
+				await Dialog.ShowOk(dialog, dialogTitle, "File '" + Path.GetFileName(path) + "' could not be imported: " + ex.Message);
 			}
 		}
 		
 		await callback.Update("Done", finished, total);
 		
 		if (successful == 0) {
-			await Dialog.ShowOk(dialog, neutralDialogTitle, "Nothing was imported.");
-			return;
+			return null;
 		}
 		
 		DatabaseStatistics newStatistics = await DatabaseStatistics.Take(target);
-		await Dialog.ShowOk(dialog, neutralDialogTitle, GetImportDialogMessage(oldStatistics, newStatistics, successful, total, itemName));
+		return new ImportResult(oldStatistics, newStatistics, successful, total);
 	}
 	
 	private sealed record DatabaseStatistics(long ServerCount, long ChannelCount, long UserCount, long MessageCount) {
@@ -237,7 +262,16 @@ sealed class DatabasePageModel {
 		}
 	}
 	
-	private static string GetImportDialogMessage(DatabaseStatistics oldStatistics, DatabaseStatistics newStatistics, int successfulItems, int totalItems, string itemName) {
+	private sealed record ImportResult(DatabaseStatistics OldStatistics, DatabaseStatistics NewStatistics, int SuccessfulItems, int TotalItems);
+	
+	private static string GetImportDialogMessage(ImportResult? result, string itemName) {
+		if (result == null) {
+			return "Nothing was imported.";
+		}
+		
+		var oldStatistics = result.OldStatistics;
+		var newStatistics = result.NewStatistics;
+		
 		long newServers = newStatistics.ServerCount - oldStatistics.ServerCount;
 		long newChannels = newStatistics.ChannelCount - oldStatistics.ChannelCount;
 		long newUsers = newStatistics.UserCount - oldStatistics.UserCount;
@@ -246,11 +280,11 @@ sealed class DatabasePageModel {
 		var message = new StringBuilder();
 		message.Append("Processed ");
 		
-		if (successfulItems == totalItems) {
-			message.Append(successfulItems.Pluralize(itemName));
+		if (result.SuccessfulItems == result.TotalItems) {
+			message.Append(result.SuccessfulItems.Pluralize(itemName));
 		}
 		else {
-			message.Append(successfulItems.Format()).Append(" out of ").Append(totalItems.Pluralize(itemName));
+			message.Append(result.SuccessfulItems.Format()).Append(" out of ").Append(result.TotalItems.Pluralize(itemName));
 		}
 		
 		message.Append(" and added:\n\n  \u2022 ");
@@ -264,7 +298,15 @@ sealed class DatabasePageModel {
 	
 	public async Task VacuumDatabase() {
 		const string Title = "Vacuum Database";
-		await ProgressDialog.ShowIndeterminate(window, Title, "Vacuuming database...", _ => Db.Vacuum());
+		
+		try {
+			await ProgressDialog.ShowIndeterminate(window, Title, "Vacuuming database...", _ => Db.Vacuum());
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, Title, "Could not vacuum database: " + e.Message);
+			return;
+		}
+		
 		await Dialog.ShowOk(window, Title, "Done.");
 	}
 }

app/Desktop/Main/Pages/DebugPageModel.cs

@@ -51,7 +51,7 @@ sealed class DebugPageModel {
 	
 	private async Task GenerateRandomData(int channelCount, int userCount, int messageCount, IProgressCallback callback) {
 		int batchCount = (messageCount + BatchSize - 1) / BatchSize;
-		await callback.Update("Adding messages in batches of " + BatchSize, finishedItems: 0, batchCount);
+		await callback.Update("Adding messages in batches of " + BatchSize, finishedItems: 0, totalItems: batchCount);
 		
 		var rand = new Random();
 		var server = new DHT.Server.Data.Server {

app/Desktop/Main/Pages/DownloadsPage.axaml

@@ -33,8 +33,9 @@
     <StackPanel Orientation="Vertical">
         <WrapPanel Orientation="Horizontal">
             <Button Command="{Binding OnClickToggleDownload}" Content="{Binding ToggleDownloadButtonText}" IsEnabled="{Binding IsToggleDownloadButtonEnabled}" />
-            <Button Command="{Binding OnClickRetryFailedDownloads}" IsEnabled="{Binding IsRetryFailedOnDownloadsButtonEnabled}">Retry Failed Downloads</Button>
-            <Button Command="{Binding OnClickDeleteOrphanedDownloads}">Delete Orphaned Downloads</Button>
+            <Button Command="{Binding OnClickRetryFailed}" IsEnabled="{Binding IsRetryFailedOnDownloadsButtonEnabled}">Retry Failed</Button>
+            <Button Command="{Binding OnClickDeleteOrphaned}">Delete Orphaned</Button>
+            <Button Command="{Binding OnClickExportAll}" IsEnabled="{Binding HasSuccessfulDownloads}">Export All</Button>
         </WrapPanel>
         <StackPanel Orientation="Vertical" Spacing="20" Margin="0 10 0 0">
             <controls:DownloadItemFilterPanel DataContext="{Binding FilterModel}" IsEnabled="{Binding !$parent[UserControl].((pages:DownloadsPageModel)DataContext).IsDownloading}" />

app/Desktop/Main/Pages/DownloadsPageModel.cs

@@ -4,9 +4,11 @@ using System.Collections.ObjectModel;
 using System.Reactive.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
+using Avalonia.Platform.Storage;
 using Avalonia.ReactiveUI;
 using CommunityToolkit.Mvvm.ComponentModel;
 using DHT.Desktop.Common;
+using DHT.Desktop.Dialogs.File;
 using DHT.Desktop.Dialogs.Message;
 using DHT.Desktop.Dialogs.Progress;
 using DHT.Desktop.Main.Controls;
@@ -33,6 +35,9 @@ sealed partial class DownloadsPageModel : ObservableObject, IAsyncDisposable {
 	[NotifyPropertyChangedFor(nameof(IsRetryFailedOnDownloadsButtonEnabled))]
 	private bool isRetryingFailedDownloads = false;
 	
+	[ObservableProperty(Setter = Access.Private)]
+	private bool hasSuccessfulDownloads;
+	
 	[ObservableProperty(Setter = Access.Private)]
 	[NotifyPropertyChangedFor(nameof(IsRetryFailedOnDownloadsButtonEnabled))]
 	private bool hasFailedDownloads;
@@ -148,7 +153,7 @@ sealed partial class DownloadsPageModel : ObservableObject, IAsyncDisposable {
 		RecomputeDownloadStatistics();
 	}
 	
-	public async Task OnClickRetryFailedDownloads() {
+	public async Task OnClickRetryFailed() {
 		IsRetryingFailedDownloads = true;
 		
 		try {
@@ -165,46 +170,94 @@ sealed partial class DownloadsPageModel : ObservableObject, IAsyncDisposable {
 		downloadStatisticsTask.Post(cancellationToken => state.Db.Downloads.GetStatistics(currentDownloadFilter ?? new DownloadItemFilter(), cancellationToken));
 	}
 	
-	public async Task OnClickDeleteOrphanedDownloads() {
+	public async Task OnClickDeleteOrphaned() {
 		const string Title = "Delete Orphaned Downloads";
 		
-		await ProgressDialog.Show(window, Title, async (_, callback) => {
-			await callback.UpdateIndeterminate("Searching for orphaned downloads...");
-			
-			HashSet<string> reachableNormalizedUrls = [];
-			HashSet<string> orphanedNormalizedUrls = [];
-			
-			await foreach (Download download in state.Db.Downloads.FindAllDownloadableUrls()) {
-				reachableNormalizedUrls.Add(download.NormalizedUrl);
-			}
-			
-			await foreach (Download download in state.Db.Downloads.Get()) {
-				string normalizedUrl = download.NormalizedUrl;
-				if (!reachableNormalizedUrls.Contains(normalizedUrl)) {
-					orphanedNormalizedUrls.Add(normalizedUrl);
+		try {
+			await ProgressDialog.Show(window, Title, async (_, callback) => {
+				await callback.UpdateIndeterminate("Searching for orphaned downloads...");
+				
+				HashSet<string> reachableNormalizedUrls = [];
+				HashSet<string> orphanedNormalizedUrls = [];
+				
+				await foreach (Download download in state.Db.Downloads.FindAllDownloadableUrls()) {
+					reachableNormalizedUrls.Add(download.NormalizedUrl);
 				}
-			}
-			
-			if (orphanedNormalizedUrls.Count == 0) {
-				await Dialog.ShowOk(window, Title, "No orphaned downloads found.");
-				return;
-			}
-			
-			if (await Dialog.ShowYesNo(window, Title, orphanedNormalizedUrls.Count + " orphaned download(s) will be removed from this database. This action cannot be undone. Proceed?") != DialogResult.YesNo.Yes) {
-				return;
-			}
-			
-			await callback.UpdateIndeterminate("Deleting orphaned downloads...");
-			await state.Db.Downloads.Remove(orphanedNormalizedUrls);
-			RecomputeDownloadStatistics();
-			
-			if (await Dialog.ShowYesNo(window, Title, "Orphaned downloads deleted. Vacuum database now to reclaim space?") != DialogResult.YesNo.Yes) {
-				return;
-			}
-			
-			await callback.UpdateIndeterminate("Vacuuming database...");
-			await state.Db.Vacuum();
+				
+				await foreach (Download download in state.Db.Downloads.Get()) {
+					string normalizedUrl = download.NormalizedUrl;
+					if (!reachableNormalizedUrls.Contains(normalizedUrl)) {
+						orphanedNormalizedUrls.Add(normalizedUrl);
+					}
+				}
+				
+				if (orphanedNormalizedUrls.Count == 0) {
+					await Dialog.ShowOk(window, Title, "No orphaned downloads found.");
+					return;
+				}
+				
+				if (await Dialog.ShowYesNo(window, Title, orphanedNormalizedUrls.Count + " orphaned download(s) will be removed from this database. This action cannot be undone. Proceed?") != DialogResult.YesNo.Yes) {
+					return;
+				}
+				
+				await callback.UpdateIndeterminate("Deleting orphaned downloads...");
+				await state.Db.Downloads.Remove(orphanedNormalizedUrls);
+				RecomputeDownloadStatistics();
+				
+				if (await Dialog.ShowYesNo(window, Title, "Orphaned downloads deleted. Vacuum database now to reclaim space?") != DialogResult.YesNo.Yes) {
+					return;
+				}
+				
+				await callback.UpdateIndeterminate("Vacuuming database...");
+				await state.Db.Vacuum();
+			});
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, Title, "Could not delete orphaned downloads: " + e.Message);
+		}
+	}
+	
+	public async Task OnClickExportAll() {
+		const string Title = "Export Downloaded Files";
+		
+		string[] folders = await window.StorageProvider.OpenFolders(new FolderPickerOpenOptions {
+			Title = Title,
+			AllowMultiple = false,
 		});
+		
+		if (folders.Length != 1) {
+			return;
+		}
+		
+		string folderPath = folders[0];
+		
+		DownloadExporter exporter = new DownloadExporter(state.Db, folderPath);
+		DownloadExporter.Result result;
+		try {
+			result = await ProgressDialog.Show(window, Title, async (_, callback) => {
+				await callback.UpdateIndeterminate("Exporting downloaded files...");
+				return await exporter.Export(new ExportProgressReporter(callback));
+			});
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, Title, "Could not export downloaded files: " + e.Message);
+			return;
+		}
+		
+		string messageStart = "Exported " + result.SuccessfulCount.Pluralize("file");
+		
+		if (result.FailedCount > 0L) {
+			await Dialog.ShowOk(window, Title, messageStart + " (" + result.FailedCount.Format() + " failed).");
+		}
+		else {
+			await Dialog.ShowOk(window, Title, messageStart + ".");
+		}
+	}
+	
+	private sealed class ExportProgressReporter(IProgressCallback callback) : DownloadExporter.IProgressReporter {
+		public Task ReportProgress(long processedCount, long totalCount) {
+			return callback.Update("Exporting downloaded files...", processedCount, totalCount);
+		}
 	}
 	
 	private void UpdateStatistics(DownloadStatusStatistics statusStatistics) {
@@ -224,6 +277,7 @@ sealed partial class DownloadsPageModel : ObservableObject, IAsyncDisposable {
 		statisticsSkipped.Size = statusStatistics.SkippedTotalSize;
 		statisticsSkipped.HasFilesWithUnknownSize = statusStatistics.SkippedWithUnknownSizeCount > 0;
 		
+		HasSuccessfulDownloads = statusStatistics.SuccessfulCount > 0;
 		HasFailedDownloads = statusStatistics.FailedCount > 0;
 	}
 	

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -61,18 +61,23 @@ sealed partial class ViewerPageModel : ObservableObject, IDisposable {
 	}
 	
 	public async Task OnClickApplyFiltersToDatabase() {
-		MessageFilter filter = FilterModel.CreateFilter();
-		long messageCount = await ProgressDialog.ShowIndeterminate(window, "Apply Filters", "Counting matching messages...", _ => state.Db.Messages.Count(filter));
-		
-		if (DatabaseToolFilterModeKeep) {
-			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Keep Matching Messages in This Database", messageCount.Pluralize("message") + " will be kept, and the rest will be removed from this database. This action cannot be undone. Proceed?")) {
-				await ApplyFilterToDatabase(filter, FilterRemovalMode.KeepMatching);
+		try {
+			MessageFilter filter = FilterModel.CreateFilter();
+			long messageCount = await ProgressDialog.ShowIndeterminate(window, "Apply Filters", "Counting matching messages...", _ => state.Db.Messages.Count(filter));
+			
+			if (DatabaseToolFilterModeKeep) {
+				if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Keep Matching Messages in This Database", messageCount.Pluralize("message") + " will be kept, and the rest will be removed from this database. This action cannot be undone. Proceed?")) {
+					await ApplyFilterToDatabase(filter, FilterRemovalMode.KeepMatching);
+				}
 			}
-		}
-		else if (DatabaseToolFilterModeRemove) {
-			if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Remove Matching Messages in This Database", messageCount.Pluralize("message") + " will be removed from this database. This action cannot be undone. Proceed?")) {
-				await ApplyFilterToDatabase(filter, FilterRemovalMode.RemoveMatching);
+			else if (DatabaseToolFilterModeRemove) {
+				if (DialogResult.YesNo.Yes == await Dialog.ShowYesNo(window, "Remove Matching Messages in This Database", messageCount.Pluralize("message") + " will be removed from this database. This action cannot be undone. Proceed?")) {
+					await ApplyFilterToDatabase(filter, FilterRemovalMode.RemoveMatching);
+				}
 			}
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, "Apply Filters", "Could not apply filters: " + e.Message);
 		}
 	}
 	

app/Desktop/Main/Screens/WelcomeScreenModel.cs

@@ -112,38 +112,32 @@ sealed partial class WelcomeScreenModel : ObservableObject {
 	}
 	
 	public async Task CheckUpdates() {
-		var latestVersion = await ProgressDialog.ShowIndeterminate<Version?>(window, "Check Updates", "Checking for updates...", async _ => {
-			var client = new HttpClient(new SocketsHttpHandler {
-				AutomaticDecompression = DecompressionMethods.None,
-				AllowAutoRedirect = false,
-				UseCookies = false,
+		string response;
+		try {
+			response = await ProgressDialog.ShowIndeterminate<string>(window, "Check Updates", "Checking for updates...", static async _ => {
+				var client = new HttpClient(new SocketsHttpHandler {
+					AutomaticDecompression = DecompressionMethods.None,
+					AllowAutoRedirect = false,
+					UseCookies = false,
+				});
+				
+				client.Timeout = TimeSpan.FromSeconds(30);
+				client.MaxResponseContentBufferSize = 1024;
+				client.DefaultRequestHeaders.UserAgent.ParseAdd("DiscordHistoryTracker/" + Program.Version);
+				
+				return await client.GetStringAsync(Program.Website + "/version");
 			});
-			
-			client.Timeout = TimeSpan.FromSeconds(30);
-			client.MaxResponseContentBufferSize = 1024;
-			client.DefaultRequestHeaders.UserAgent.ParseAdd("DiscordHistoryTracker/" + Program.Version);
-			
-			string response;
-			try {
-				response = await client.GetStringAsync(Program.Website + "/version");
-			} catch (TaskCanceledException e) when (e.InnerException is TimeoutException) {
-				await Dialog.ShowOk(window, "Check Updates", "Request timed out.");
-				return null;
-			} catch (Exception e) {
-				Log.Error(e);
-				await Dialog.ShowOk(window, "Check Updates", "Error checking for updates: " + e.Message);
-				return null;
-			}
-			
-			if (!System.Version.TryParse(response, out Version? latestVersion)) {
-				await Dialog.ShowOk(window, "Check Updates", "Server returned an invalid response.");
-				return null;
-			}
-			
-			return latestVersion;
-		});
+		} catch (TaskCanceledException e) when (e.InnerException is TimeoutException) {
+			await Dialog.ShowOk(window, "Check Updates", "Request timed out.");
+			return;
+		} catch (Exception e) {
+			Log.Error(e);
+			await Dialog.ShowOk(window, "Check Updates", "Error checking for updates: " + e.Message);
+			return;
+		}
 		
-		if (latestVersion == null) {
+		if (!System.Version.TryParse(response, out Version? latestVersion)) {
+			await Dialog.ShowOk(window, "Check Updates", "Server returned an invalid response.");
 			return;
 		}
 		

app/Server/Database/Repositories/IDownloadRepository.cs

@@ -20,7 +20,7 @@ public interface IDownloadRepository {
 	
 	Task<DownloadStatusStatistics> GetStatistics(DownloadItemFilter nonSkippedFilter, CancellationToken cancellationToken = default);
 	
-	IAsyncEnumerable<Data.Download> Get();
+	IAsyncEnumerable<Data.Download> Get(DownloadItemFilter? filter = null);
 	
 	Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor);
 	
@@ -51,7 +51,7 @@ public interface IDownloadRepository {
 			return Task.FromResult(new DownloadStatusStatistics());
 		}
 		
-		public IAsyncEnumerable<Data.Download> Get() {
+		public IAsyncEnumerable<Data.Download> Get(DownloadItemFilter? filter) {
 			return AsyncEnumerable.Empty<Data.Download>();
 		}
 		

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

@@ -201,10 +201,10 @@ sealed class SqliteDownloadRepository(SqliteConnectionPool pool) : BaseSqliteRep
 		};
 	}
 	
-	public async IAsyncEnumerable<Data.Download> Get() {
+	public async IAsyncEnumerable<Data.Download> Get(DownloadItemFilter? filter) {
 		await using var conn = await pool.Take();
 		
-		await using var cmd = conn.Command("SELECT normalized_url, download_url, status, type, size FROM download_metadata");
+		await using var cmd = conn.Command("SELECT normalized_url, download_url, status, type, size FROM download_metadata" + filter.GenerateConditions().BuildWhereClause());
 		await using var reader = await cmd.ExecuteReaderAsync();
 		
 		while (await reader.ReadAsync()) {

app/Server/Download/DownloadExporter.cs

@@ -0,0 +1,152 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+using DHT.Server.Data;
+using DHT.Server.Data.Filters;
+using DHT.Server.Database;
+using DHT.Utils.Logging;
+using DHT.Utils.Tasks;
+using Channel = System.Threading.Channels.Channel;
+
+namespace DHT.Server.Download;
+
+public sealed partial class DownloadExporter(IDatabaseFile db, string folderPath) {
+	private static readonly Log Log = Log.ForType<DownloadExporter>();
+	
+	private const int Concurrency = 3;
+	
+	private static Channel<Data.Download> CreateExportChannel() {
+		return Channel.CreateBounded<Data.Download>(new BoundedChannelOptions(Concurrency * 4) {
+			SingleWriter = true,
+			SingleReader = false,
+			AllowSynchronousContinuations = true,
+			FullMode = BoundedChannelFullMode.Wait,
+		});
+	}
+	
+	public interface IProgressReporter {
+		Task ReportProgress(long processedCount, long totalCount);
+	}
+	
+	public readonly record struct Result(long SuccessfulCount, long FailedCount) {
+		internal static Result Combine(Result left, Result right) {
+			return new Result(left.SuccessfulCount + right.SuccessfulCount, left.FailedCount + right.FailedCount);
+		}
+	}
+	
+	public async Task<Result> Export(IProgressReporter reporter) {
+		DownloadItemFilter filter = new DownloadItemFilter {
+			IncludeStatuses = [DownloadStatus.Success]
+		};
+		
+		long totalCount = await db.Downloads.Count(filter);
+		
+		Channel<Data.Download> channel = CreateExportChannel();
+		ExportRunner exportRunner = new ExportRunner(db, folderPath, channel.Reader, reporter, totalCount);
+		
+		using CancellableTask progressTask = CancellableTask.Run(exportRunner.RunReportTask);
+		
+		List<Task<Result>> readerTasks = [];
+		for (int reader = 0; reader < Concurrency; reader++) {
+			readerTasks.Add(Task.Run(exportRunner.RunExportTask, CancellationToken.None));
+		}
+		
+		await foreach (Data.Download download in db.Downloads.Get(filter).WithCancellation(CancellationToken.None)) {
+			await channel.Writer.WriteAsync(download, CancellationToken.None);
+		}
+		
+		channel.Writer.Complete();
+		
+		Result result = (await Task.WhenAll(readerTasks)).Aggregate(Result.Combine);
+		
+		progressTask.Cancel();
+		await progressTask.Task;
+		
+		return result;
+	}
+	
+	private sealed partial class ExportRunner(IDatabaseFile db, string folderPath, ChannelReader<Data.Download> reader, IProgressReporter reporter, long totalCount) {
+		private long processedCount;
+		
+		public async Task RunReportTask(CancellationToken cancellationToken) {
+			try {
+				while (true) {
+					await reporter.ReportProgress(processedCount, totalCount);
+					await Task.Delay(TimeSpan.FromMilliseconds(25), cancellationToken);
+				}
+			} catch (OperationCanceledException) {
+				await reporter.ReportProgress(processedCount, totalCount);
+			}
+		}
+		
+		public async Task<Result> RunExportTask() {
+			long successfulCount = 0L;
+			long failedCount = 0L;
+			
+			await foreach (Data.Download download in reader.ReadAllAsync()) {
+				bool success;
+				try {
+					success = await db.Downloads.GetDownloadData(download.NormalizedUrl, stream => CopyToFile(download.NormalizedUrl, stream));
+				} catch (FileAlreadyExistsException) {
+					success = false;
+				} catch (Exception e) {
+					Log.Error(e);
+					success = false;
+				}
+				
+				if (success) {
+					++successfulCount;
+				}
+				else {
+					++failedCount;
+				}
+				
+				Interlocked.Increment(ref processedCount);
+			}
+			
+			return new Result(successfulCount, failedCount);
+		}
+		
+		private async Task CopyToFile(string normalizedUrl, Stream blobStream) {
+			string fileName = UrlToFileName(normalizedUrl);
+			string filePath = Path.Combine(folderPath, fileName);
+			
+			if (File.Exists(filePath)) {
+				Log.Error("Skipping existing file: " + fileName);
+				throw FileAlreadyExistsException.Instance;
+			}
+			
+			await using var fileStream = new FileStream(filePath, FileMode.CreateNew, FileAccess.Write, FileShare.Read);
+			await blobStream.CopyToAsync(fileStream);
+		}
+		
+		[GeneratedRegex("[^a-zA-Z0-9_.-]")]
+		private static partial Regex DisallowedFileNameCharactersRegex();
+		
+		private static string UrlToFileName(string url) {
+			static string UriToFileName(Uri uri) {
+				string fileName = uri.AbsolutePath.TrimStart('/');
+				
+				if (uri.Query.Length > 0) {
+					int periodIndex = fileName.LastIndexOf('.');
+					return fileName.Insert(periodIndex == -1 ? fileName.Length : periodIndex, uri.Query.TrimEnd('&'));
+				}
+				else {
+					return fileName;
+				}
+			}
+			
+			string fileName = Uri.TryCreate(url, UriKind.Absolute, out var uri) ? UriToFileName(uri) : url;
+			return DisallowedFileNameCharactersRegex().Replace(fileName, "_");
+		}
+	}
+	
+	private sealed class FileAlreadyExistsException : Exception {
+		public static FileAlreadyExistsException Instance { get; } = new ();
+	}
+}

app/Utils/Tasks/CancellableTask.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DHT.Utils.Tasks;
+
+public sealed class CancellableTask : IDisposable {
+	public static CancellableTask Run(Func<CancellationToken, Task> action) {
+		return new CancellableTask(action);
+	}
+	
+	public Task Task { get; }
+	
+	private readonly CancellationTokenSource cancellationTokenSource = new ();
+	
+	private CancellableTask(Func<CancellationToken, Task> action) {
+		CancellationToken cancellationToken = cancellationTokenSource.Token;
+		Task = Task.Run(() => action(cancellationToken));
+	}
+	
+	public void Cancel() {
+		cancellationTokenSource.Cancel();
+	}
+	
+	public void Dispose() {
+		cancellationTokenSource.Dispose();
+	}
+}