Serve viewer page and JSON data from the integrated HTTP server

Closes #256

app/.idea/.idea.DiscordHistoryTracker/.idea/codeStyles/Project.xml

@@ -13,10 +13,10 @@
     <CssCodeStyleSettings>
       <option name="HEX_COLOR_LOWER_CASE" value="true" />
     </CssCodeStyleSettings>
-    <DB2CodeStyleSettings version="6">
+    <DB2CodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </DB2CodeStyleSettings>
-    <DerbyCodeStyleSettings version="6">
+    <DerbyCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </DerbyCodeStyleSettings>
     <GoCodeStyleSettings>
@@ -26,10 +26,10 @@
       <option name="WRAP_FUNC_PARAMS" value="5" />
       <option name="WRAP_FUNC_RESULT" value="5" />
     </GoCodeStyleSettings>
-    <H2CodeStyleSettings version="6">
+    <H2CodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </H2CodeStyleSettings>
-    <HSQLCodeStyleSettings version="6">
+    <HSQLCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </HSQLCodeStyleSettings>
     <HTMLCodeStyleSettings>
@@ -85,10 +85,10 @@
     <LessCodeStyleSettings>
       <option name="HEX_COLOR_LOWER_CASE" value="true" />
     </LessCodeStyleSettings>
-    <MSSQLCodeStyleSettings version="6">
+    <MSSQLCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </MSSQLCodeStyleSettings>
-    <MySQLCodeStyleSettings version="6">
+    <MySQLCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </MySQLCodeStyleSettings>
     <Objective-C>
@@ -98,7 +98,7 @@
       <option name="SPACE_BEFORE_INIT_LIST" value="true" />
       <option name="SPACE_AFTER_DICTIONARY_LITERAL_COLON" value="false" />
     </Objective-C>
-    <OracleCodeStyleSettings version="6">
+    <OracleCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </OracleCodeStyleSettings>
     <PHPCodeStyleSettings>
@@ -116,7 +116,7 @@
       <option name="NEW_LINE_AFTER_PHP_OPENING_TAG" value="true" />
       <option name="SPACE_AROUND_ASSIGNMENT_IN_DECLARE" value="true" />
     </PHPCodeStyleSettings>
-    <PostgresCodeStyleSettings version="6">
+    <PostgresCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </PostgresCodeStyleSettings>
     <Properties>
@@ -143,7 +143,7 @@
       <option name="INDENT_WHEN_CASES" value="true" />
       <option name="CHAIN_CALLS_ALIGNMENT" value="2" />
     </Ruby>
-    <SQLiteCodeStyleSettings version="6">
+    <SQLiteCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </SQLiteCodeStyleSettings>
     <ScssCodeStyleSettings>
@@ -152,7 +152,7 @@
     <Shell_Script>
       <option name="KEEP_COLUMN_ALIGNMENT_PADDING" value="true" />
     </Shell_Script>
-    <SqlCodeStyleSettings version="6">
+    <SqlCodeStyleSettings version="7">
       <option name="KEYWORD_CASE" value="2" />
       <option name="TYPE_CASE" value="2" />
       <option name="CUSTOM_TYPE_CASE" value="2" />
@@ -179,7 +179,7 @@
       <option name="IMP_LOOP_LOOP_INDENT" value="false" />
       <option name="EXPR_CASE_WHEN_WRAP" value="false" />
     </SqlCodeStyleSettings>
-    <SybaseCodeStyleSettings version="6">
+    <SybaseCodeStyleSettings version="7">
       <option name="USE_GENERIC_STYLE" value="true" />
     </SybaseCodeStyleSettings>
     <TypeScriptCodeStyleSettings version="0">

app/Desktop/Arguments.cs

@@ -15,6 +15,7 @@ sealed class Arguments {
 	public string? DatabaseFile { get; }
 	public ushort? ServerPort { get; }
 	public string? ServerToken { get; }
+	public byte? ConcurrentDownloads { get; }
 
 	public Arguments(IReadOnlyList<string> args) {
 		for (int i = FirstArgument; i < args.Count; i++) {
@@ -50,11 +51,11 @@ sealed class Arguments {
 					continue;
 
 				case "-port": {
-					if (ushort.TryParse(value, out var port)) {
-						ServerPort = port;
+					if (!ushort.TryParse(value, out var port)) {
+						Log.Warn("Invalid port number: " + value);
 					}
 					else {
-						Log.Warn("Invalid port number: " + value);
+						ServerPort = port;
 					}
 
 					continue;
@@ -64,6 +65,20 @@ sealed class Arguments {
 					ServerToken = value;
 					continue;
 				
+				case "-concurrentdownloads":
+					if (!ulong.TryParse(value, out var concurrentDownloads) || concurrentDownloads == 0) {
+						Log.Warn("Invalid concurrent downloads count: " + value);
+					}
+					else if (concurrentDownloads > 10) {
+						Log.Warn("Limiting concurrent downloads to 10");
+						ConcurrentDownloads = 10;
+					}
+					else {
+						ConcurrentDownloads = (byte) concurrentDownloads;
+					}
+					
+					continue;
+
 				default:
 					Log.Warn("Unknown command line argument: " + key);
 					break;

app/Desktop/Main/MainWindowModel.cs

@@ -30,6 +30,7 @@ sealed partial class MainWindowModel : ObservableObject, IAsyncDisposable {
 	private MainContentScreenModel? mainContentScreenModel;
 
 	private readonly Window window;
+	private readonly int? concurrentDownloads;
 
 	private State? state;
 
@@ -73,6 +74,8 @@ sealed partial class MainWindowModel : ObservableObject, IAsyncDisposable {
 		if (args.ServerToken != null) {
 			ServerConfiguration.Token = args.ServerToken;
 		}
+		
+		concurrentDownloads = args.ConcurrentDownloads;
 	}
 
 	private async void OnDatabaseSelected(object? sender, IDatabaseFile db) {
@@ -80,7 +83,7 @@ sealed partial class MainWindowModel : ObservableObject, IAsyncDisposable {
 		
 		await DisposeState();
 		
-		state = new State(db);
+		state = new State(db, concurrentDownloads);
 
 		try {
 			await state.Server.Start(ServerConfiguration.Port, ServerConfiguration.Token);

app/Desktop/Main/Pages/DebugPageModel.cs

@@ -10,7 +10,8 @@ using DHT.Server;
 using DHT.Server.Data;
 using DHT.Server.Service;
 
-namespace DHT.Desktop.Main.Pages {
+namespace DHT.Desktop.Main.Pages;
+
 sealed class DebugPageModel {
 	public string GenerateChannels { get; set; } = "0";
 	public string GenerateUsers { get; set; } = "0";
@@ -159,9 +160,9 @@ namespace DHT.Desktop.Main.Pages {
 		return string.Join(' ', Enumerable.Range(0, wordCount).Select(_ => RandomWords[rand.Next(RandomWords.Length)]));
 	}
 }
-}
 #else
-namespace DHT.Desktop.Main.Pages {
+namespace DHT.Desktop.Main.Pages;
+
 sealed class DebugPageModel {
 	public string GenerateChannels { get; set; } = "0";
 	public string GenerateUsers { get; set; } = "0";
@@ -169,5 +170,4 @@ namespace DHT.Desktop.Main.Pages {
 
 	public void OnClickAddRandomDataToDatabase() {}
 }
-}
 #endif

app/Desktop/Main/Pages/ViewerPageModel.cs

@@ -60,7 +60,7 @@ sealed partial class ViewerPageModel : ObservableObject, IDisposable {
 			string serverUrl = "http://127.0.0.1:" + ServerConfiguration.Port;
 			string serverToken = ServerConfiguration.Token;
 			
-			Process.Start(new ProcessStartInfo(serverUrl + "/viewer?token=" + HttpUtility.UrlEncode(serverToken)) {
+			Process.Start(new ProcessStartInfo(serverUrl + "/viewer/?token=" + HttpUtility.UrlEncode(serverToken)) {
 				UseShellExecute = true
 			});
 		} catch (Exception e) {

app/Resources/Tracker/scripts/state.js

@@ -48,6 +48,16 @@ const STATE = (function() {
 		});
 	};
 	
+	const getDate = function(date) {
+		if (date instanceof Date) {
+			return date;
+		}
+		else {
+			// noinspection JSUnresolvedReference
+			return date.toDate();
+		}
+	};
+	
 	const trackingStateChangedListeners = [];
 	let isTracking = false;
 	
@@ -69,8 +79,8 @@ const STATE = (function() {
 	 * @property {String} channel_id
 	 * @property {DiscordUser} author
 	 * @property {String} content
-	 * @property {Timestamp} timestamp
-	 * @property {Timestamp|null} editedTimestamp
+	 * @property {Date} timestamp
+	 * @property {Date|null} editedTimestamp
 	 * @property {DiscordAttachment[]} attachments
 	 * @property {Object[]} embeds
 	 * @property {DiscordMessageReaction[]} [reactions]
@@ -106,11 +116,6 @@ const STATE = (function() {
 	 * @property {Boolean} animated
 	 */
 	
-	/**
-	 * @name Timestamp
-	 * @property {Function} toDate
-	 */
-	
 	return {
 		setup(port, token) {
 			serverPort = port;
@@ -223,12 +228,12 @@ const STATE = (function() {
 					sender: msg.author.id,
 					channel: msg.channel_id,
 					text: msg.content,
-					timestamp: msg.timestamp.toDate().getTime()
+					timestamp: getDate(msg.timestamp).getTime()
 				};
 				
 				if (msg.editedTimestamp !== null) {
 					// noinspection JSUnusedGlobalSymbols
-					obj.editTimestamp = msg.editedTimestamp.toDate().getTime();
+					obj.editTimestamp = getDate(msg.editedTimestamp).getTime();
 				}
 				
 				if (msg.messageReference !== null) {

app/Resources/Viewer/index.html

@@ -13,7 +13,6 @@
     <link rel="stylesheet" href="styles/modal.css">
     
     <script type="text/javascript">
-		window.DHT_SERVER_URL = location.protocol + "//" + location.host + location.pathname;
 		window.DHT_SERVER_TOKEN = new URLSearchParams(location.search).get("token");
     </script>
     <script type="module" src="scripts/bootstrap.mjs"></script>
@@ -70,7 +69,9 @@
     </div>
     
     <div id="app">
-      <div id="channels"></div>
+      <div id="channels">
+        <div class="loading"></div>
+      </div>
       <div id="messages"></div>
     </div>
     

app/Resources/Viewer/scripts/bootstrap.mjs

@@ -36,10 +36,25 @@ document.addEventListener("DOMContentLoaded", () => {
 		gui.scrollMessagesToTop();
 	});
 	
+	async function loadData() {
 		try {
-		state.uploadFile(JSON.parse(window.DHT_EMBEDDED));
+			const response = await fetch("/get-viewer-data?token=" + encodeURIComponent(window.DHT_SERVER_TOKEN), {
+				method: "GET",
+				headers: {
+					"Content-Type": "application/json",
+				},
+				credentials: "omit",
+				redirect: "error",
+			});
+			
+			const json = await response.json();
+			state.uploadFile(json);
 		} catch (e) {
 			console.error(e);
-		alert("Could not parse embedded file, see console for details.");
+			alert("Could not load data, see console for details.");
+			document.querySelector("#channels > div.loading").remove();
 		}
+	}
+	
+	loadData();
 });

app/Resources/Viewer/scripts/discord.mjs

@@ -41,17 +41,14 @@ export default (function() {
 	let templateReaction;
 	let templateReactionCustom;
 	
-	const fileUrlProcessor = function(serverUrl, serverToken) {
-		if (typeof serverUrl === "string" && typeof serverToken === "string") {
-			return url => serverUrl + "/get-downloaded-file/" + encodeURIComponent(url) + "?token=" + encodeURIComponent(serverToken);
+	const fileUrlProcessor = function(serverToken) {
+		if (typeof serverToken === "string") {
+			return url => "/get-downloaded-file/" + encodeURIComponent(url) + "?token=" + encodeURIComponent(serverToken);
 		}
 		else {
 			return url => url;
 		}
-	}(
-		window["DHT_SERVER_URL"],
-		window["DHT_SERVER_TOKEN"]
-	);
+	}(window.DHT_SERVER_TOKEN);
 	
 	const getEmoji = function(name, id, extension) {
 		const tag = ":" + name + ":";
@@ -116,14 +113,14 @@ export default (function() {
 	return {
 		setup() {
 			templateChannelServer = new template([
-				"<div data-channel='{id}'>",
+				"<div class='channel' data-channel='{id}'>",
 				"<div class='info' title='{topic}'><strong class='name'>#{name}</strong>{nsfw}<span class='tag'>{msgcount}</span></div>",
 				"<span class='server'>{server.name} ({server.type})</span>",
 				"</div>"
 			].join(""));
 			
 			templateChannelPrivate = new template([
-				"<div data-channel='{id}'>",
+				"<div class='channel' data-channel='{id}'>",
 				"<div class='info'><strong class='name'>{name}</strong><span class='tag'>{msgcount}</span></div>",
 				"<span class='server'>({server.type})</span>",
 				"</div>"
@@ -164,12 +161,12 @@ export default (function() {
 			
 			// noinspection HtmlUnknownTarget
 			templateEmbedImage = new template([
-				"<a href='{url}' class='embed thumbnail loading'><img src='{src}' alt='' onload='DISCORD.handleImageLoad(this)' onerror='DISCORD.handleImageLoadError(this)'></a><br>"
+				"<a href='{url}' class='embed thumbnail loading'><img src='{src}' alt='' onload='window.DISCORD.handleImageLoad(this)' onerror='window.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>"
+				"<a href='{url}' class='embed thumbnail loading'><img src='{src}' width='{width}' height='{height}' alt='' onload='window.DISCORD.handleImageLoad(this)' onerror='window.DISCORD.handleImageLoadError(this)'></a><br>"
 			].join(""));
 			
 			// noinspection HtmlUnknownTarget

app/Resources/Viewer/styles/channels.css

@@ -3,18 +3,24 @@
   min-width: 215px;
   max-width: 300px;
   overflow-y: auto;
+  color: #eee;
   background-color: #1c1e22;
+  font-size: 15px;
 }
 
-#channels > div {
+#channels > div.loading {
+  margin: 0 auto;
+  width: 150px;
+  height: 150px;
+}
+
+#channels > div.channel {
   cursor: pointer;
   padding: 10px 12px;
-  color: #eee;
-  font-size: 15px;
   border-bottom: 1px solid #333333;
 }
 
-#channels > div:hover, #channels > div.active {
+#channels > div.channel:hover, #channels > div.channel.active {
   background-color: #282b30;
 }
 

app/Resources/Viewer/styles/main.css

@@ -11,3 +11,20 @@ body {
   display: flex;
   flex-direction: row;
 }
+
+.loading {
+  position: relative;
+  --loading-backdrop: rgba(0, 0, 0, 0);
+}
+
+.loading::after {
+  content: "";
+  background: var(--loading-backdrop)
+  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%;
+}

app/Resources/Viewer/styles/messages.css

@@ -107,23 +107,11 @@
 }
 
 .message .thumbnail {
-  position: relative;
+  --loading-backdrop: rgba(0, 0, 0, 0.75);
   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%;

app/Server/Data/DownloadWithData.cs

@@ -1,3 +0,0 @@
-namespace DHT.Server.Data;
-
-public readonly record struct DownloadWithData(Download Download, byte[]? Data);

app/Server/Database/DatabaseExtensions.cs

@@ -26,7 +26,9 @@ public static class DatabaseExtensions {
 		await target.Messages.Add(batchedMessages);
 
 		await foreach (var download in source.Downloads.Get()) {
-			await target.Downloads.AddDownload(await source.Downloads.HydrateWithData(download));
+			if (download.Status != DownloadStatus.Success || !await source.Downloads.GetDownloadData(download.NormalizedUrl, stream => target.Downloads.AddDownload(download, stream))) {
+				await target.Downloads.AddDownload(download, stream: null);
+			}
 		}
 	}
 }

app/Server/Database/Export/ViewerJsonExport.cs

@@ -10,7 +10,7 @@ using DHT.Utils.Logging;
 
 namespace DHT.Server.Database.Export;
 
-public static class ViewerJsonExport {
+static class ViewerJsonExport {
 	private static readonly Log Log = Log.ForType(typeof(ViewerJsonExport));
 
 	public static async Task Generate(Stream stream, IDatabaseFile db, MessageFilter? filter = null) {

app/Server/Database/Import/LegacyArchiveImport.cs

@@ -161,7 +161,7 @@ public static class LegacyArchiveImport {
 
 		var messagesObj = data.HasKey(channelIdStr) ? data.RequireObject(channelIdStr, DataPath) : (JsonElement?) null;
 		if (messagesObj == null) {
-			return Array.Empty<Message>();
+			return [];
 		}
 
 		return messagesObj.Value.EnumerateObject().Select(item => {

app/Server/Database/Repositories/IDownloadRepository.cs

@@ -1,10 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Reactive.Linq;
 using System.Threading;
 using System.Threading.Tasks;
-using DHT.Server.Data;
 using DHT.Server.Data.Aggregations;
 using DHT.Server.Data.Filters;
 using DHT.Server.Download;
@@ -14,7 +14,7 @@ namespace DHT.Server.Database.Repositories;
 public interface IDownloadRepository {
 	IObservable<long> TotalCount { get; }
 
-	Task AddDownload(DownloadWithData item);
+	Task AddDownload(Data.Download item, Stream? stream);
 
 	Task<long> Count(DownloadItemFilter filter, CancellationToken cancellationToken = default);
 	
@@ -22,9 +22,9 @@ public interface IDownloadRepository {
 	
 	IAsyncEnumerable<Data.Download> Get();
 
-	Task<DownloadWithData> HydrateWithData(Data.Download download);
+	Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor);
 	
-	Task<DownloadWithData?> GetSuccessfulDownloadWithData(string normalizedUrl);
+	Task<bool> GetSuccessfulDownloadWithData(string normalizedUrl, Func<Data.Download, Stream, Task> dataProcessor);
 
 	IAsyncEnumerable<DownloadItem> PullPendingDownloadItems(int count, DownloadItemFilter filter, CancellationToken cancellationToken = default);
 	
@@ -35,7 +35,7 @@ public interface IDownloadRepository {
 	internal sealed class Dummy : IDownloadRepository {
 		public IObservable<long> TotalCount { get; } = Observable.Return(0L);
 
-		public Task AddDownload(DownloadWithData item) {
+		public Task AddDownload(Data.Download item, Stream? stream) {
 			return Task.CompletedTask;
 		}
 
@@ -51,12 +51,12 @@ public interface IDownloadRepository {
 			return AsyncEnumerable.Empty<Data.Download>();
 		}
 
-		public Task<DownloadWithData> HydrateWithData(Data.Download download) {
-			return Task.FromResult(new DownloadWithData(download, Data: null));
+		public Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor) {
+			return Task.FromResult(false);
 		}
 
-		public Task<DownloadWithData?> GetSuccessfulDownloadWithData(string normalizedUrl) {
-			return Task.FromResult<DownloadWithData?>(null);
+		public Task<bool> GetSuccessfulDownloadWithData(string normalizedUrl, Func<Data.Download, Stream, Task> dataProcessor) {
+			return Task.FromResult(false);
 		}
 
 		public IAsyncEnumerable<DownloadItem> PullPendingDownloadItems(int count, DownloadItemFilter filter, CancellationToken cancellationToken) {

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

@@ -19,9 +19,9 @@ sealed class SqliteChannelRepository : BaseSqliteRepository, IChannelRepository
 	}
 
 	public async Task Add(IReadOnlyList<Channel> channels) {
-		await using var conn = await pool.Take();
+		await using (var conn = await pool.Take()) {
+			await conn.BeginTransactionAsync();
 			
-		await using (var tx = await conn.BeginTransactionAsync()) {
 			await using var cmd = conn.Upsert("channels", [
 				("id", SqliteType.Integer),
 				("server", SqliteType.Integer),
@@ -43,7 +43,7 @@ sealed class SqliteChannelRepository : BaseSqliteRepository, IChannelRepository
 				await cmd.ExecuteNonQueryAsync();
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 		}
 
 		UpdateTotalCount();

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

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -14,15 +15,9 @@ using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Repositories;
 
-sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepository {
+sealed class SqliteDownloadRepository(SqliteConnectionPool pool) : BaseSqliteRepository(Log), IDownloadRepository {
 	private static readonly Log Log = Log.ForType<SqliteDownloadRepository>();
 
-	private readonly SqliteConnectionPool pool;
-
-	public SqliteDownloadRepository(SqliteConnectionPool pool) : base(Log) {
-		this.pool = pool;
-	}
-
 	internal sealed class NewDownloadCollector : IAsyncDisposable {
 		private readonly SqliteDownloadRepository repository;
 		private bool hasAdded = false;
@@ -66,11 +61,9 @@ sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepositor
 		}
 	}
 
-	public async Task AddDownload(DownloadWithData item) {
-		var (download, data) = item;
-
+	public async Task AddDownload(Data.Download item, Stream? stream) {
 		await using (var conn = await pool.Take()) {
-			var tx = await conn.BeginTransactionAsync();
+			await conn.BeginTransactionAsync();
 			
 			await using var metadataCmd = conn.Upsert("download_metadata", [
 				("normalized_url", SqliteType.Text),
@@ -80,30 +73,37 @@ sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepositor
 				("size", SqliteType.Integer),
 			]);
 
-			metadataCmd.Set(":normalized_url", download.NormalizedUrl);
-			metadataCmd.Set(":download_url", download.DownloadUrl);
-			metadataCmd.Set(":status", (int) download.Status);
-			metadataCmd.Set(":type", download.Type);
-			metadataCmd.Set(":size", download.Size);
+			metadataCmd.Set(":normalized_url", item.NormalizedUrl);
+			metadataCmd.Set(":download_url", item.DownloadUrl);
+			metadataCmd.Set(":status", (int) item.Status);
+			metadataCmd.Set(":type", item.Type);
+			metadataCmd.Set(":size", item.Size);
 			await metadataCmd.ExecuteNonQueryAsync();
 
-			if (data == null) {
+			if (stream == null) {
 				await using var deleteBlobCmd = conn.Command("DELETE FROM download_blobs WHERE normalized_url = :normalized_url");
-				deleteBlobCmd.AddAndSet(":normalized_url", SqliteType.Text, download.NormalizedUrl);
+				deleteBlobCmd.AddAndSet(":normalized_url", SqliteType.Text, item.NormalizedUrl);
 				await deleteBlobCmd.ExecuteNonQueryAsync();
 			}
 			else {
-				await using var upsertBlobCmd = conn.Upsert("download_blobs", [
-					("normalized_url", SqliteType.Text),
-					("blob", SqliteType.Blob)
-				]);
+				await using var upsertBlobCmd = conn.Command(
+					"""
+					INSERT INTO download_blobs (normalized_url, blob)
+					VALUES (:normalized_url, ZEROBLOB(:blob_length))
+					ON CONFLICT (normalized_url) DO UPDATE SET blob = excluded.blob
+					RETURNING rowid
+					"""
+				);
 				
-				upsertBlobCmd.Set(":normalized_url", download.NormalizedUrl);
-				upsertBlobCmd.Set(":blob", data);
-				await upsertBlobCmd.ExecuteNonQueryAsync();
+				upsertBlobCmd.AddAndSet(":normalized_url", SqliteType.Text, item.NormalizedUrl);
+				upsertBlobCmd.AddAndSet(":blob_length", SqliteType.Integer, item.Size);
+				long rowid = await upsertBlobCmd.ExecuteLongScalarAsync();
+
+				await using var blob = new SqliteBlob(conn.InnerConnection, "download_blobs", "blob", rowid);
+				await stream.CopyToAsync(blob);
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 		}
 
 		UpdateTotalCount();
@@ -187,24 +187,35 @@ sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepositor
 		}
 	}
 
-	public async Task<DownloadWithData> HydrateWithData(Data.Download download) {
+	public async Task<bool> GetDownloadData(string normalizedUrl, Func<Stream, Task> dataProcessor) {
 		await using var conn = await pool.Take();
 
-		await using var cmd = conn.Command("SELECT blob FROM download_blobs WHERE normalized_url = :url");
-		cmd.AddAndSet(":url", SqliteType.Text, download.NormalizedUrl);
+		await using var cmd = conn.Command("SELECT rowid FROM download_blobs WHERE normalized_url = :normalized_url");
+		cmd.AddAndSet(":normalized_url", SqliteType.Text, normalizedUrl);
 		
-		await using var reader = await cmd.ExecuteReaderAsync();
-		var data = await reader.ReadAsync() && !reader.IsDBNull(0) ? (byte[]) reader["blob"] : null;
+		long rowid;
 		
-		return new DownloadWithData(download, data);
+		await using (var reader = await cmd.ExecuteReaderAsync()) {
+			if (!await reader.ReadAsync()) {
+				return false;
 			}
 
-	public async Task<DownloadWithData?> GetSuccessfulDownloadWithData(string normalizedUrl) {
+			rowid = reader.GetInt64(0);
+		}
+		
+		await using (var blob = new SqliteBlob(conn.InnerConnection, "download_blobs", "blob", rowid, readOnly: true)) {
+			await dataProcessor(blob);
+		}
+
+		return true;
+	}
+
+	public async Task<bool> GetSuccessfulDownloadWithData(string normalizedUrl, Func<Data.Download, Stream, Task> dataProcessor) {
 		await using var conn = await pool.Take();
 
 		await using var cmd = conn.Command(
 			"""
-			SELECT dm.download_url, dm.type, db.blob FROM download_metadata dm
+			SELECT dm.download_url, dm.type, db.rowid FROM download_metadata dm
 			JOIN download_blobs db ON dm.normalized_url = db.normalized_url
 			WHERE dm.normalized_url = :normalized_url AND dm.status = :success IS NOT NULL
 			"""
@@ -213,19 +224,25 @@ sealed class SqliteDownloadRepository : BaseSqliteRepository, IDownloadRepositor
 		cmd.AddAndSet(":normalized_url", SqliteType.Text, normalizedUrl);
 		cmd.AddAndSet(":success", SqliteType.Integer, (int) DownloadStatus.Success);
 
-		await using var reader = await cmd.ExecuteReaderAsync();
+		string downloadUrl;
+		string? type;
+		long rowid;
 		
+		await using (var reader = await cmd.ExecuteReaderAsync()) {
 			if (!await reader.ReadAsync()) {
-			return null;
+				return false;
 			}
 
-		var downloadUrl = reader.GetString(0);
-		var type = reader.IsDBNull(1) ? null : reader.GetString(1);
-		var data = (byte[]) reader[2];
-		var size = (ulong) data.LongLength;
-		var download = new Data.Download(normalizedUrl, downloadUrl, DownloadStatus.Success, type, size);
+			downloadUrl = reader.GetString(0);
+			type = reader.IsDBNull(1) ? null : reader.GetString(1);
+			rowid = reader.GetInt64(2);
+		}
 		
-		return new DownloadWithData(download, data);
+		await using (var blob = new SqliteBlob(conn.InnerConnection, "download_blobs", "blob", rowid, readOnly: true)) {
+			await dataProcessor(new Data.Download(normalizedUrl, downloadUrl, DownloadStatus.Success, type, (ulong) blob.Length), blob);
+		}
+
+		return true;
 	}
 
 	public async IAsyncEnumerable<DownloadItem> PullPendingDownloadItems(int count, DownloadItemFilter filter, [EnumeratorCancellation] CancellationToken cancellationToken) {

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

@@ -39,7 +39,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 		}
 
 		await using (var conn = await pool.Take()) {
-			await using var tx = await conn.BeginTransactionAsync();
+			await conn.BeginTransactionAsync();
 
 			await using var messageCmd = conn.Upsert("messages", [
 				("message_id", SqliteType.Integer),
@@ -167,7 +167,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 				}
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 			downloadCollector.OnCommitted();
 		}
 
@@ -183,11 +183,11 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 		return await conn.ExecuteReaderAsync("SELECT COUNT(*) FROM messages" + filter.GenerateConditions().BuildWhereClause(), static reader => reader?.GetInt64(0) ?? 0L, cancellationToken);
 	}
 
-	private sealed class MesageToManyCommand<T> : IAsyncDisposable {
+	private sealed class MessageToManyCommand<T> : IAsyncDisposable {
 		private readonly SqliteCommand cmd;
 		private readonly Func<SqliteDataReader, T> readItem;
 
-		public MesageToManyCommand(ISqliteConnection conn, string sql, Func<SqliteDataReader, T> readItem) {
+		public MessageToManyCommand(ISqliteConnection conn, string sql, Func<SqliteDataReader, T> readItem) {
 			this.cmd = conn.Command(sql);
 			this.cmd.Add(":message_id", SqliteType.Integer);
 
@@ -223,7 +223,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			WHERE message_id = :message_id
 			""";
 
-		await using var attachmentCmd = new MesageToManyCommand<Attachment>(conn, AttachmentSql, static reader => new Attachment {
+		await using var attachmentCmd = new MessageToManyCommand<Attachment>(conn, AttachmentSql, static reader => new Attachment {
 			Id = reader.GetUint64(0),
 			Name = reader.GetString(1),
 			Type = reader.IsDBNull(2) ? null : reader.GetString(2),
@@ -241,7 +241,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			WHERE message_id = :message_id
 			""";
 
-		await using var embedCmd = new MesageToManyCommand<Embed>(conn, EmbedSql, static reader => new Embed {
+		await using var embedCmd = new MessageToManyCommand<Embed>(conn, EmbedSql, static reader => new Embed {
 			Json = reader.GetString(0)
 		});
 
@@ -252,7 +252,7 @@ sealed class SqliteMessageRepository : BaseSqliteRepository, IMessageRepository
 			WHERE message_id = :message_id
 			""";
 
-		await using var reactionsCmd = new MesageToManyCommand<Reaction>(conn, ReactionSql, static reader => new Reaction {
+		await using var reactionsCmd = new MessageToManyCommand<Reaction>(conn, ReactionSql, static reader => new Reaction {
 			EmojiId = reader.IsDBNull(0) ? null : reader.GetUint64(0),
 			EmojiName = reader.IsDBNull(1) ? null : reader.GetString(1),
 			EmojiFlags = (EmojiFlags) reader.GetInt16(2),

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

@@ -19,9 +19,9 @@ sealed class SqliteServerRepository : BaseSqliteRepository, IServerRepository {
 	}
 
 	public async Task Add(IReadOnlyList<Data.Server> servers) {
-		await using var conn = await pool.Take();
+		await using (var conn = await pool.Take()) {
+			await conn.BeginTransactionAsync();
 			
-		await using (var tx = await conn.BeginTransactionAsync()) {
 			await using var cmd = conn.Upsert("servers", [
 				("id", SqliteType.Integer),
 				("name", SqliteType.Text),
@@ -35,7 +35,7 @@ sealed class SqliteServerRepository : BaseSqliteRepository, IServerRepository {
 				await cmd.ExecuteNonQueryAsync();
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 		}
 
 		UpdateTotalCount();

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

@@ -23,7 +23,7 @@ sealed class SqliteUserRepository : BaseSqliteRepository, IUserRepository {
 
 	public async Task Add(IReadOnlyList<User> users) {
 		await using (var conn = await pool.Take()) {
-			await using var tx = await conn.BeginTransactionAsync();
+			await conn.BeginTransactionAsync();
 
 			await using var cmd = conn.Upsert("users", [
 				("id", SqliteType.Integer),
@@ -46,7 +46,7 @@ sealed class SqliteUserRepository : BaseSqliteRepository, IUserRepository {
 				}
 			}
 
-			await tx.CommitAsync();
+			await conn.CommitTransactionAsync();
 			downloadCollector.OnCommitted();
 		}
 

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo6.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Data.Common;
 using System.Threading.Tasks;
 using DHT.Server.Database.Sqlite.Utils;
 using DHT.Server.Download;
@@ -39,7 +38,7 @@ sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
 			}
 		}
 
-		await using var tx = await conn.BeginTransactionAsync();
+		await conn.BeginTransactionAsync();
 
 		int totalUrls = normalizedUrls.Count;
 		int processedUrls = -1;
@@ -61,7 +60,7 @@ sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
 
 		await reporter.SubWork("Updating URLs...", totalUrls, totalUrls);
 
-		await tx.CommitAsync();
+		await conn.CommitTransactionAsync();
 	}
 
 	private async Task NormalizeDownloadUrls(ISqliteConnection conn, ISchemaUpgradeCallbacks.IProgressReporter reporter) {
@@ -84,10 +83,8 @@ sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
 		}
 
 		await conn.ExecuteAsync("PRAGMA cache_size = -20000");
+		await conn.BeginTransactionAsync();
 		
-		DbTransaction tx;
-
-		await using (tx = await conn.BeginTransactionAsync()) {
 		await reporter.SubWork("Deleting duplicates...", 0, 0);
 
 		await using (var deleteCmd = conn.Delete("downloads", ("url", SqliteType.Text))) {
@@ -97,13 +94,12 @@ sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
 			}
 		}
 
-			await tx.CommitAsync();
-		}
+		await conn.CommitTransactionAsync();
 
 		int totalUrls = normalizedUrlsToOriginalUrls.Count;
 		int processedUrls = -1;
 
-		tx = await conn.BeginTransactionAsync();
+		await conn.BeginTransactionAsync();
 
 		await using (var updateCmd = conn.Command("UPDATE downloads SET download_url = :download_url, url = :normalized_url WHERE url = :download_url")) {
 			updateCmd.Add(":normalized_url", SqliteType.Text);
@@ -115,11 +111,10 @@ sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
 
 					// Not proper way of dealing with transactions, but it avoids a long commit at the end.
 					// Schema upgrades are already non-atomic anyways, so this doesn't make it worse.
-					await tx.CommitAsync();
-					await tx.DisposeAsync();
+					await conn.CommitTransactionAsync();
 
-					tx = await conn.BeginTransactionAsync();
-					updateCmd.Transaction = (SqliteTransaction) tx;
+					await conn.BeginTransactionAsync();
+					conn.AssignActiveTransaction(updateCmd);
 				}
 
 				updateCmd.Set(":normalized_url", normalizedUrl);
@@ -130,8 +125,7 @@ sealed class SqliteSchemaUpgradeTo6 : ISchemaUpgrade {
 
 		await reporter.SubWork("Updating URLs...", totalUrls, totalUrls);
 
-		await tx.CommitAsync();
-		await tx.DisposeAsync();
+		await conn.CommitTransactionAsync();
 
 		await conn.ExecuteAsync("PRAGMA cache_size = -2000");
 	}

app/Server/Database/Sqlite/Schema/SqliteSchemaUpgradeTo7.cs

@@ -37,7 +37,7 @@ sealed class SqliteSchemaUpgradeTo7 : ISchemaUpgrade {
 
 		await reporter.SubWork("Processing downloaded files...", 0, totalFiles);
 
-		var tx = await conn.BeginTransactionAsync();
+		await conn.BeginTransactionAsync();
 
 		await using (var insertCmd = conn.Command("INSERT INTO download_blobs (normalized_url, blob) SELECT normalized_url, blob FROM downloads WHERE normalized_url = :normalized_url"))
 		await using (var deleteCmd = conn.Command("DELETE FROM downloads WHERE normalized_url = :normalized_url")) {
@@ -50,12 +50,11 @@ sealed class SqliteSchemaUpgradeTo7 : ISchemaUpgrade {
 
 					// Not proper way of dealing with transactions, but it avoids a long commit at the end.
 					// Schema upgrades are already non-atomic anyways, so this doesn't make it worse.
-					await tx.CommitAsync();
-					await tx.DisposeAsync();
+					await conn.CommitTransactionAsync();
 					
-					tx = await conn.BeginTransactionAsync();
-					insertCmd.Transaction = (SqliteTransaction) tx;
-					deleteCmd.Transaction = (SqliteTransaction) tx;
+					await conn.BeginTransactionAsync();
+					conn.AssignActiveTransaction(insertCmd);
+					conn.AssignActiveTransaction(deleteCmd);
 				}
 
 				insertCmd.Set(":normalized_url", url);
@@ -68,8 +67,7 @@ sealed class SqliteSchemaUpgradeTo7 : ISchemaUpgrade {
 
 		await reporter.SubWork("Processing downloaded files...", totalFiles, totalFiles);
 
-		await tx.CommitAsync();
-		await tx.DisposeAsync();
+		await conn.CommitTransactionAsync();
 	}
 
 	private async Task<List<string>> GetDownloadedFileUrls(ISqliteConnection conn) {
@@ -111,7 +109,8 @@ sealed class SqliteSchemaUpgradeTo7 : ISchemaUpgrade {
 			await insertCmd.ExecuteNonQueryAsync();
 		}
 
-		await using (var tx = await conn.BeginTransactionAsync()) {
+		await conn.BeginTransactionAsync();
+
 		await using var insertCmd = conn.Command("INSERT OR IGNORE INTO download_metadata (normalized_url, download_url, status, type, size) VALUES (:normalized_url, :download_url, :status, :type, :size)");
 		insertCmd.Add(":normalized_url", SqliteType.Text);
 		insertCmd.Add(":download_url", SqliteType.Text);
@@ -149,7 +148,6 @@ sealed class SqliteSchemaUpgradeTo7 : ISchemaUpgrade {
 			}
 		}
 
-			await tx.CommitAsync();
-		}
+		await conn.CommitTransactionAsync();
 	}
 }

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

@@ -1,8 +1,15 @@
 using System;
+using System.Threading.Tasks;
 using Microsoft.Data.Sqlite;
 
 namespace DHT.Server.Database.Sqlite.Utils;
 
 interface ISqliteConnection : IAsyncDisposable {
 	SqliteConnection InnerConnection { get; }
+	
+	Task BeginTransactionAsync();
+	Task CommitTransactionAsync();
+	Task RollbackTransactionAsync();
+	
+	void AssignActiveTransaction(SqliteCommand command);
 }

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

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Data.Common;
 using System.Threading;
 using System.Threading.Tasks;
 using DHT.Utils.Collections;
@@ -73,17 +74,48 @@ sealed class SqliteConnectionPool : IAsyncDisposable {
 		disposalTokenSource.Dispose();
 	}
 
-	private sealed class PooledConnection : ISqliteConnection {
-		public SqliteConnection InnerConnection { get; }
+	private sealed class PooledConnection(SqliteConnectionPool pool, SqliteConnection conn) : ISqliteConnection {
+		public SqliteConnection InnerConnection { get; } = conn;
 
-		private readonly SqliteConnectionPool pool;
+		private DbTransaction? activeTransaction;
 
-		public PooledConnection(SqliteConnectionPool pool, SqliteConnection conn) {
-			this.pool = pool;
-			this.InnerConnection = conn;
+		public async Task BeginTransactionAsync() {
+			if (activeTransaction != null) {
+				throw new InvalidOperationException("A transaction is already active.");
+			}
+			
+			activeTransaction = await InnerConnection.BeginTransactionAsync();
+		}
+
+		public async Task CommitTransactionAsync() {
+			if (activeTransaction == null) {
+				throw new InvalidOperationException("No active transaction to commit.");
+			}
+
+			await activeTransaction.CommitAsync();
+			await activeTransaction.DisposeAsync();
+			activeTransaction = null;
+		}
+
+		public async Task RollbackTransactionAsync() {
+			if (activeTransaction == null) {
+				throw new InvalidOperationException("No active transaction to rollback.");
+			}
+			
+			await activeTransaction.RollbackAsync();
+			await activeTransaction.DisposeAsync();
+			activeTransaction = null;
+		}
+
+		public void AssignActiveTransaction(SqliteCommand command) {
+			command.Transaction = (SqliteTransaction?) activeTransaction;
 		}
 
 		public async ValueTask DisposeAsync() {
+			if (activeTransaction != null) {
+				await RollbackTransactionAsync();
+			}
+			
 			await pool.Return(this);
 		}
 	}

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

@@ -1,5 +1,4 @@
 using System;
-using System.Data.Common;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -9,10 +8,6 @@ using Microsoft.Data.Sqlite;
 namespace DHT.Server.Database.Sqlite.Utils;
 
 static class SqliteExtensions {
-	public static ValueTask<DbTransaction> BeginTransactionAsync(this ISqliteConnection conn) {
-		return conn.InnerConnection.BeginTransactionAsync();
-	}
-
 	public static SqliteCommand Command(this ISqliteConnection conn, [LanguageInjection("sql")] string sql) {
 		var cmd = conn.InnerConnection.CreateCommand();
 		cmd.CommandText = sql;
@@ -31,6 +26,10 @@ static class SqliteExtensions {
 		return await reader.ReadAsync(cancellationToken) ? readFunction(reader) : readFunction(null);
 	}
 	
+	public static async Task<long> ExecuteLongScalarAsync(this SqliteCommand command) {
+		return (long) (await command.ExecuteScalarAsync())!;
+	}
+
 	public static SqliteCommand Insert(this ISqliteConnection conn, string tableName, (string Name, SqliteType Type)[] columns) {
 		string columnNames = string.Join(',', columns.Select(static c => c.Name));
 		string columnParams = string.Join(',', columns.Select(static c => ':' + c.Name));

app/Server/Download/DownloadItem.cs

@@ -10,13 +10,12 @@ public readonly struct DownloadItem {
 	public string? Type { get; init; }
 	public ulong? Size { get; init; }
 	
-	internal DownloadWithData ToSuccess(byte[] data) {
-		var size = (ulong) Math.Max(data.LongLength, 0);
-		return new DownloadWithData(new Data.Download(NormalizedUrl, DownloadUrl, DownloadStatus.Success, Type, size), data);
+	internal Data.Download ToSuccess(long size) {
+		return new Data.Download(NormalizedUrl, DownloadUrl, DownloadStatus.Success, Type, (ulong) Math.Max(size, 0));
 	}
 	
-	internal DownloadWithData ToFailure(HttpStatusCode? statusCode = null) {
+	internal Data.Download ToFailure(HttpStatusCode? statusCode = null) {
 		var status = statusCode.HasValue ? (DownloadStatus) (int) statusCode : DownloadStatus.GenericError;
-		return new DownloadWithData(new Data.Download(NormalizedUrl, DownloadUrl, status, Type, Size), Data: null);
+		return new Data.Download(NormalizedUrl, DownloadUrl, status, Type, Size);
 	}
 }

app/Server/Download/Downloader.cs

@@ -11,16 +11,18 @@ public sealed class Downloader {
 	public bool IsDownloading => current != null;
 	
 	private readonly IDatabaseFile db;
+	private readonly int? concurrentDownloads;
 	private readonly SemaphoreSlim semaphore = new (1, 1);
 	
-	internal Downloader(IDatabaseFile db) {
+	internal Downloader(IDatabaseFile db, int? concurrentDownloads) {
 		this.db = db;
+		this.concurrentDownloads = concurrentDownloads;
 	}
 
 	public async Task<IObservable<DownloadItem>> Start(DownloadItemFilter filter) {
 		await semaphore.WaitAsync();
 		try {
-			current ??= new DownloaderTask(db, filter);
+			current ??= new DownloaderTask(db, filter, concurrentDownloads);
 			return current.FinishedItems;
 		} finally {
 			semaphore.Release();

app/Server/Download/DownloaderTask.cs

@@ -15,10 +15,14 @@ namespace DHT.Server.Download;
 sealed class DownloaderTask : IAsyncDisposable {
 	private static readonly Log Log = Log.ForType<DownloaderTask>();
 
-	private const int DownloadTasks = 4;
+	private const int DefaultConcurrentDownloads = 4;
 	private const int QueueSize = 25;
 	private const string UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36";
 
+	private static int GetDownloadTaskCount(int? concurrentDownloads) {
+		return Math.Max(1, concurrentDownloads ?? DefaultConcurrentDownloads);
+	}
+
 	private readonly Channel<DownloadItem> downloadQueue = Channel.CreateBounded<DownloadItem>(new BoundedChannelOptions(QueueSize) {
 		SingleReader = false,
 		SingleWriter = true,
@@ -38,12 +42,12 @@ sealed class DownloaderTask : IAsyncDisposable {
 
 	public IObservable<DownloadItem> FinishedItems => finishedItemPublisher;
 
-	internal DownloaderTask(IDatabaseFile db, DownloadItemFilter filter) {
+	internal DownloaderTask(IDatabaseFile db, DownloadItemFilter filter, int? concurrentDownloads) {
 		this.db = db;
 		this.filter = filter;
 		this.cancellationToken = cancellationTokenSource.Token;
 		this.queueWriterTask = Task.Run(RunQueueWriterTask);
-		this.downloadTasks = Enumerable.Range(1, DownloadTasks).Select(taskIndex => Task.Run(() => RunDownloadTask(taskIndex))).ToArray();
+		this.downloadTasks = Enumerable.Range(1, GetDownloadTaskCount(concurrentDownloads)).Select(taskIndex => Task.Run(() => RunDownloadTask(taskIndex))).ToArray();
 	}
 
 	private async Task RunQueueWriterTask() {
@@ -63,24 +67,39 @@ sealed class DownloaderTask : IAsyncDisposable {
 	private async Task RunDownloadTask(int taskIndex) {
 		var log = Log.ForType<DownloaderTask>("Task " + taskIndex);
 
-		var client = new HttpClient();
+		var client = new HttpClient(new SocketsHttpHandler {
+			ConnectTimeout = TimeSpan.FromSeconds(30)
+		});
+		
+		client.Timeout = Timeout.InfiniteTimeSpan;
 		client.DefaultRequestHeaders.UserAgent.ParseAdd(UserAgent);
-		client.Timeout = TimeSpan.FromSeconds(30);
 
 		while (!cancellationToken.IsCancellationRequested) {
 			var item = await downloadQueue.Reader.ReadAsync(cancellationToken);
 			log.Debug("Downloading " + item.DownloadUrl + "...");
 
 			try {
-				var downloadedBytes = await client.GetByteArrayAsync(item.DownloadUrl, cancellationToken);
-				await db.Downloads.AddDownload(item.ToSuccess(downloadedBytes));
-			} catch (OperationCanceledException) {
+				var response = await client.SendAsync(new HttpRequestMessage(HttpMethod.Get, item.DownloadUrl), HttpCompletionOption.ResponseHeadersRead, cancellationToken);
+				response.EnsureSuccessStatusCode();
+
+				if (response.Content.Headers.ContentLength is {} contentLength) {
+					await using var stream = await response.Content.ReadAsStreamAsync(cancellationToken);
+					await db.Downloads.AddDownload(item.ToSuccess(contentLength), stream);
+				}
+				else {
+					await db.Downloads.AddDownload(item.ToFailure(), stream: null);
+					log.Error("Download response has no content length: " + item.DownloadUrl);
+				}
+			} catch (OperationCanceledException e) when (e.CancellationToken == cancellationToken) {
 				// Ignore.
+			} catch (TaskCanceledException e) when (e.InnerException is TimeoutException) {
+				await db.Downloads.AddDownload(item.ToFailure(), stream: null);
+				log.Error("Download timed out: " + item.DownloadUrl);
 			} catch (HttpRequestException e) {
-				await db.Downloads.AddDownload(item.ToFailure(e.StatusCode));
+				await db.Downloads.AddDownload(item.ToFailure(e.StatusCode), stream: null);
 				log.Error(e);
 			} catch (Exception e) {
-				await db.Downloads.AddDownload(item.ToFailure());
+				await db.Downloads.AddDownload(item.ToFailure(), stream: null);
 				log.Error(e);
 			} finally {
 				try {

app/Server/Endpoints/BaseEndpoint.cs

@@ -9,37 +9,37 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-abstract class BaseEndpoint {
+abstract class BaseEndpoint(IDatabaseFile db) {
 	private static readonly Log Log = Log.ForType<BaseEndpoint>();
 
-	protected IDatabaseFile Db { get; }
-
-	protected BaseEndpoint(IDatabaseFile db) {
-		this.Db = db;
-	}
+	protected IDatabaseFile Db { get; } = db;
 
 	public async Task Handle(HttpContext ctx) {
 		var response = ctx.Response;
 
 		try {
 			response.StatusCode = (int) HttpStatusCode.OK;
-			var output = await Respond(ctx);
-			await output.WriteTo(response);
+			await Respond(ctx.Request, response);
 		} catch (HttpException e) {
 			Log.Error(e);
 			response.StatusCode = (int) e.StatusCode;
+			if (response.HasStarted) {
+				Log.Warn("Response has already started, cannot write status message: " + e.Message);
+			}
+			else {
 				await response.WriteAsync(e.Message);
+			}
 		} catch (Exception e) {
 			Log.Error(e);
 			response.StatusCode = (int) HttpStatusCode.InternalServerError;
 		}
 	}
 
-	protected abstract Task<IHttpOutput> Respond(HttpContext ctx);
+	protected abstract Task Respond(HttpRequest request, HttpResponse response);
 
-	protected static async Task<JsonElement> ReadJson(HttpContext ctx) {
+	protected static async Task<JsonElement> ReadJson(HttpRequest request) {
 		try {
-			return await ctx.Request.ReadFromJsonAsync(JsonElementContext.Default.JsonElement);
+			return await request.ReadFromJsonAsync(JsonElementContext.Default.JsonElement);
 		} catch (JsonException) {
 			throw new HttpException(HttpStatusCode.UnsupportedMediaType, "This endpoint only accepts JSON.");
 		}

app/Server/Endpoints/GetDownloadedFileEndpoint.cs

@@ -7,18 +7,13 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class GetDownloadedFileEndpoint : BaseEndpoint {
-	public GetDownloadedFileEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		string url = WebUtility.UrlDecode((string) ctx.Request.RouteValues["url"]!);
+sealed class GetDownloadedFileEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		string url = WebUtility.UrlDecode((string) request.RouteValues["url"]!);
 		string normalizedUrl = DiscordCdn.NormalizeUrl(url);
 		
-		if (await Db.Downloads.GetSuccessfulDownloadWithData(normalizedUrl) is { Download: {} download, Data: {} data }) {
-			return new HttpOutput.File(download.Type, data);
-		}
-		else {
-			return new HttpOutput.Redirect(url, permanent: false);
+		if (!await Db.Downloads.GetSuccessfulDownloadWithData(normalizedUrl, (download, stream) => response.WriteStreamAsync(download.Type, download.Size, stream))) {
+			response.Redirect(url, permanent: false);
 		}
 	}
 }

app/Server/Endpoints/GetTrackingScriptEndpoint.cs

@@ -1,4 +1,4 @@
-using System.Text;
+using System.Net.Mime;
 using System.Threading.Tasks;
 using System.Web;
 using DHT.Server.Database;
@@ -9,25 +9,17 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class GetTrackingScriptEndpoint : BaseEndpoint {
-	private readonly ServerParameters serverParameters;
-	private readonly ResourceLoader resources;
-
-	public GetTrackingScriptEndpoint(IDatabaseFile db, ServerParameters parameters, ResourceLoader resources) : base(db) {
-		this.serverParameters = parameters;
-		this.resources = resources;
-	}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
+sealed class GetTrackingScriptEndpoint(IDatabaseFile db, ServerParameters parameters, ResourceLoader resources) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
 		string bootstrap = await resources.ReadTextAsync("Tracker/bootstrap.js");
-		string script = bootstrap.Replace("= 0; /*[PORT]*/", "= " + serverParameters.Port + ";")
-		                         .Replace("/*[TOKEN]*/", HttpUtility.JavaScriptStringEncode(serverParameters.Token))
+		string script = bootstrap.Replace("= 0; /*[PORT]*/", "= " + parameters.Port + ";")
+		                         .Replace("/*[TOKEN]*/", HttpUtility.JavaScriptStringEncode(parameters.Token))
 		                         .Replace("/*[IMPORTS]*/", await resources.ReadJoinedAsync("Tracker/scripts/", '\n'))
 		                         .Replace("/*[CSS-CONTROLLER]*/", await resources.ReadTextAsync("Tracker/styles/controller.css"))
 		                         .Replace("/*[CSS-SETTINGS]*/", await resources.ReadTextAsync("Tracker/styles/settings.css"))
-		                         .Replace("/*[DEBUGGER]*/", ctx.Request.Query.ContainsKey("debug") ? "debugger;" : "");
+		                         .Replace("/*[DEBUGGER]*/", request.Query.ContainsKey("debug") ? "debugger;" : "");
 		
-		ctx.Response.Headers.Append("X-DHT", "1");
-		return new HttpOutput.File("text/javascript", Encoding.UTF8.GetBytes(script));
+		response.Headers.Append("X-DHT", "1");
+		await response.WriteTextAsync(MediaTypeNames.Text.JavaScript, script);
 	}
 }

app/Server/Endpoints/TrackChannelEndpoint.cs

@@ -8,18 +8,14 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class TrackChannelEndpoint : BaseEndpoint {
-	public TrackChannelEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		var root = await ReadJson(ctx);
+sealed class TrackChannelEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		var root = await ReadJson(request);
 		var server = ReadServer(root.RequireObject("server"), "server");
 		var channel = ReadChannel(root.RequireObject("channel"), "channel", server.Id);
 
 		await Db.Servers.Add([server]);
 		await Db.Channels.Add([channel]);
-
-		return HttpOutput.None;
 	}
 
 	private static Data.Server ReadServer(JsonElement json, string path) => new () {

app/Server/Endpoints/TrackMessagesEndpoint.cs

@@ -15,14 +15,12 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class TrackMessagesEndpoint : BaseEndpoint {
+sealed class TrackMessagesEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
 	private const string HasNewMessages = "1";
 	private const string NoNewMessages = "0";
 
-	public TrackMessagesEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		var root = await ReadJson(ctx);
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		var root = await ReadJson(request);
 
 		if (root.ValueKind != JsonValueKind.Array) {
 			throw new HttpException(HttpStatusCode.BadRequest, "Expected root element to be an array.");
@@ -43,7 +41,7 @@ sealed class TrackMessagesEndpoint : BaseEndpoint {
 
 		await Db.Messages.Add(messages);
 
-		return new HttpOutput.Text(anyNewMessages ? HasNewMessages : NoNewMessages);
+		await response.WriteTextAsync(anyNewMessages ? HasNewMessages : NoNewMessages);
 	}
 
 	private static Message ReadMessage(JsonElement json, string path) => new () {

app/Server/Endpoints/TrackUsersEndpoint.cs

@@ -8,11 +8,9 @@ using Microsoft.AspNetCore.Http;
 
 namespace DHT.Server.Endpoints;
 
-sealed class TrackUsersEndpoint : BaseEndpoint {
-	public TrackUsersEndpoint(IDatabaseFile db) : base(db) {}
-
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		var root = await ReadJson(ctx);
+sealed class TrackUsersEndpoint(IDatabaseFile db) : BaseEndpoint(db) {
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		var root = await ReadJson(request);
 
 		if (root.ValueKind != JsonValueKind.Array) {
 			throw new HttpException(HttpStatusCode.BadRequest, "Expected root element to be an array.");
@@ -26,8 +24,6 @@ sealed class TrackUsersEndpoint : BaseEndpoint {
 		}
 
 		await Db.Users.Add(users);
-
-		return HttpOutput.None;
 	}
 
 	private static User ReadUser(JsonElement json, string path) => new () {

app/Server/Endpoints/ViewerEndpoint.cs

@@ -10,19 +10,14 @@ using Microsoft.AspNetCore.StaticFiles;
 
 namespace DHT.Server.Endpoints;
 
-sealed class ViewerEndpoint : BaseEndpoint {
+sealed class ViewerEndpoint(IDatabaseFile db, ResourceLoader resources) : BaseEndpoint(db) {
 	private static readonly FileExtensionContentTypeProvider ContentTypeProvider = new ();
 
-	private readonly ResourceLoader resources;
 	private readonly Dictionary<string, byte[]?> cache = new ();
 	private readonly SemaphoreSlim cacheSemaphore = new (1);
 
-	public ViewerEndpoint(IDatabaseFile db, ResourceLoader resources) : base(db) {
-		this.resources = resources;
-	}
-	
-	protected override async Task<IHttpOutput> Respond(HttpContext ctx) {
-		string path = (string?) ctx.Request.RouteValues["path"] ?? "index.html";
+	protected override async Task Respond(HttpRequest request, HttpResponse response) {
+		string path = (string?) request.RouteValues["path"] ?? "index.html";
 		string resourcePath = "Viewer/" + path;
 		
 		byte[]? resourceBytes;
@@ -41,7 +36,7 @@ sealed class ViewerEndpoint : BaseEndpoint {
 		}
 		else {
 			var contentType = ContentTypeProvider.TryGetContentType(path, out string? type) ? type : null;
-			return new HttpOutput.File(contentType, resourceBytes);
+			await response.WriteFileAsync(contentType, resourceBytes);
 		}
 	}
 }

app/Server/Service/ServerStartup.cs

@@ -50,6 +50,7 @@ sealed class Startup {
 		app.UseRouting();
 		app.UseEndpoints(endpoints => {
 			endpoints.MapGet("/get-tracking-script", new GetTrackingScriptEndpoint(db, parameters, resources).Handle);
+			endpoints.MapGet("/get-viewer-data", new GetViewerDataEndpoint(db).Handle);
 			endpoints.MapGet("/get-downloaded-file/{url}", new GetDownloadedFileEndpoint(db).Handle);
 			endpoints.MapPost("/track-channel", new TrackChannelEndpoint(db).Handle);
 			endpoints.MapPost("/track-users", new TrackUsersEndpoint(db).Handle);

app/Server/State.cs

@@ -6,18 +6,12 @@ using DHT.Server.Service;
 
 namespace DHT.Server;
 
-public sealed class State : IAsyncDisposable {
-	public static State Dummy { get; } = new (DummyDatabaseFile.Instance);
+public sealed class State(IDatabaseFile db, int? concurrentDownloads) : IAsyncDisposable {
+	public static State Dummy { get; } = new (DummyDatabaseFile.Instance, null);
 	
-	public IDatabaseFile Db { get; }
-	public Downloader Downloader { get; }
-	public ServerManager Server { get; }
-
-	public State(IDatabaseFile db) {
-		Db = db;
-		Downloader = new Downloader(db);
-		Server = new ServerManager(db);
-	}
+	public IDatabaseFile Db { get; } = db;
+	public Downloader Downloader { get; } = new (db, concurrentDownloads);
+	public ServerManager Server { get; } = new (db);
 
 	public async ValueTask DisposeAsync() {
 		await Downloader.Stop();

app/Utils/Collections/LinqExtensions.cs

@@ -8,7 +8,7 @@ public static class LinqExtensions {
 		HashSet<TKey>? seenKeys = null;
 
 		foreach (var item in collection) {
-			seenKeys ??= new HashSet<TKey>();
+			seenKeys ??= [];
 
 			if (seenKeys.Add(getKeyFromItem(item))) {
 				yield return item;

app/Utils/Http/HttpExtensions.cs

@@ -0,0 +1,33 @@
+using System.IO;
+using System.Net.Mime;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+
+namespace DHT.Utils.Http; 
+
+public static class HttpExtensions {
+	public static Task WriteTextAsync(this HttpResponse response, string text) {
+		return WriteTextAsync(response, MediaTypeNames.Text.Plain, text);
+	}
+	
+	public static async Task WriteTextAsync(this HttpResponse response, string contentType, string text) {
+		response.ContentType = contentType;
+		await response.StartAsync();
+		await response.WriteAsync(text, Encoding.UTF8);
+	}
+	
+	public static async Task WriteFileAsync(this HttpResponse response, string? contentType, byte[] bytes) {
+		response.ContentType = contentType ?? string.Empty;
+		response.ContentLength = bytes.Length;
+		await response.StartAsync();
+		await response.Body.WriteAsync(bytes);
+	}
+	
+	public static async Task WriteStreamAsync(this HttpResponse response, string? contentType, ulong? contentLength, Stream source) {
+		response.ContentType = contentType ?? string.Empty;
+		response.ContentLength = (long?) contentLength;
+		await response.StartAsync();
+		await source.CopyToAsync(response.Body);
+	}
+}

app/Utils/Http/HttpOutput.cs

@@ -1,35 +0,0 @@
-using System.Text;
-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 Text(string text) : IHttpOutput {
-		public Task WriteTo(HttpResponse response) {
-			return response.WriteAsync(text, Encoding.UTF8);
-		}
-	}
-
-	public sealed class File(string? contentType, byte[] bytes) : IHttpOutput {
-		public async Task WriteTo(HttpResponse response) {
-			response.ContentType = contentType ?? string.Empty;
-			await response.Body.WriteAsync(bytes);
-		}
-	}
-
-	public sealed class Redirect(string url, bool permanent) : IHttpOutput {
-		public Task WriteTo(HttpResponse response) {
-			response.Redirect(url, permanent);
-			return Task.CompletedTask;
-		}
-	}
-}

app/Utils/Http/IHttpOutput.cs

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

app/Version.cs

@@ -8,5 +8,5 @@ using DHT.Utils;
 namespace DHT.Utils;
 
 static class Version {
-	public const string Tag = "41.0.0.0";
+	public const string Tag = "41.2.0.0";
 }