refactor: follow DRY principle in YtdlpService.cs

- Extract BuildYtdlpArgs method to centralize yt-dlp argument building
- Add ArgsToCommandString helper method for shell command string conversion
- Refactor cookies workaround to reuse BuildYtdlpArgs and eliminate duplication
- Add XML documentation comments for new methods

Signed-off-by: Jim Chen <Jim@ChenJ.im>

Author: bot0419

SingletonServices/Downloader/YtdlpService.cs

@@ -24,14 +24,36 @@ public Task CreateJobAsync(Video video,
         string fileName = NameHelper.GetFileName(video, Name);
         video.Filename = fileName;
         string[]? command = null;
-        string[] args;
+        string[] args = BuildYtdlpArgs(fileName, url, liveFromStart);
 
+        if (useCookiesFile)
+            //args = ["--cookies", $"/cookies/{video.ChannelId}.txt", .. args];
+            // Remove this workaround if issue resolved.
+            // https://github.com/yt-dlp/yt-dlp/issues/5977#issuecomment-2121742572
+            (command, args) = BuildCookiesHackCommand(fileName, url, liveFromStart, video.ChannelId, mountPath);
+
+        return jobService.CreateInstanceAsync(deploymentName: instanceName,
+                                              containerName: instanceName,
+                                              imageName: "yt-dlp",
+                                              fileName: fileName,
+                                              command: command,
+                                              args: args,
+                                              mountPath: mountPath,
+                                              cancellation: cancellation);
+    }
+
+    /// <summary>
+    /// Builds yt-dlp command line arguments.
+    /// </summary>
+    private string[] BuildYtdlpArgs(string fileName, string url, bool liveFromStart)
+    {
         // Live-from-start mode uses minimal args to avoid compatibility issues
         // Working example: yt-dlp --live-from-start --no-part -o filename url
         if (liveFromStart)
         {
-            args =
+            return
             [
+                "-v",
                 "--live-from-start",
                 "--embed-thumbnail",
                 "--embed-metadata",
@@ -40,76 +62,70 @@ public Task CreateJobAsync(Video video,
                 url
             ];
         }
-        else
+
+        var args = new List<string>
         {
-            args =
-            [
-                "--ignore-config",
-                "--retries", "30",
-                "--concurrent-fragments", "16",
-                "--merge-output-format", "mp4",
-                "-S", "+proto:http,+codec:h264",
-                "--embed-thumbnail",
-                "--embed-metadata",
-                "--no-part",
-                "-o", fileName,
-                url
-            ];
+            "-v",
+            "--ignore-config",
+            "--retries", "30",
+            "--concurrent-fragments", "16",
+            "--merge-output-format", "mp4",
+            "-S", "+proto:http,+codec:h264",
+            "--embed-thumbnail",
+            "--embed-metadata",
+            "--no-part",
+            "-o", fileName,
+            url
+        };
 
-            // Workaround for twitcasting ERROR:
-            // Initialization fragment found after media fragments, unable to download
-            // https://github.com/yt-dlp/yt-dlp/issues/5497
-            if (url.Contains("twitcasting.tv")) args = ["--downloader", "ffmpeg", .. args];
+        // Workaround for twitcasting ERROR:
+        // Initialization fragment found after media fragments, unable to download
+        // https://github.com/yt-dlp/yt-dlp/issues/5497
+        if (url.Contains("twitcasting.tv"))
+        {
+            args.InsertRange(0, ["--downloader", "ffmpeg"]);
         }
 
-        if (useCookiesFile)
-            //args = ["--cookies", $"/cookies/{video.ChannelId}.txt", .. args];
-            // Remove this workaround if issue resolved.
-            // https://github.com/yt-dlp/yt-dlp/issues/5977#issuecomment-2121742572
-            (command, args) = copyCookiesHack();
+        return [.. args];
+    }
 
-        return jobService.CreateInstanceAsync(deploymentName: instanceName,
-                                              containerName: instanceName,
-                                              imageName: "yt-dlp",
-                                              fileName: fileName,
-                                              command: command,
-                                              args: args,
-                                              mountPath: mountPath,
-                                              cancellation: cancellation);
+    /// <summary>
+    /// Converts arguments array to shell command string with proper quoting.
+    /// </summary>
+    private static string ArgsToCommandString(string[] args)
+    {
+        return string.Join(" ", args.Select(arg =>
+            arg.Contains(' ') || arg.Contains('\'') ? $"'{arg.Replace("'", "'\\''")}'" : arg));
+    }
 
-        (string[] command, string[] args) copyCookiesHack()
-        {
-            // Cookies file has to be mounted elsewhere and then cp.
-            // Because yt-dlp does not support using cookies file in Read-only file system.
-            // Which it is how K8s handle secrets.
-
-            // original ENTRYPOINT: "dumb-init", "--", "yt-dlp", "--no-cache-dir"
-
-            command = ["dumb-init", "--", "sh", "-c"];
-
-            // cp under mountPath to make sure the permission is writable
-            // Live-from-start mode uses minimal args to avoid compatibility issues
-            if (liveFromStart)
-            {
-                args =
-                [
-                    $"cp -r /cookies {mountPath}/cookies && yt-dlp --live-from-start --no-part --cookies {mountPath}/cookies/{video.ChannelId}.txt -o '{fileName}' '{url}'"
-                ];
-            }
-            else
-            {
-                args =
-                [
-                    $"cp -r /cookies {mountPath}/cookies && yt-dlp --ignore-config --retries 30 --concurrent-fragments 16 --merge-output-format mp4 -S '+proto:http,+codec:h264' --embed-thumbnail --embed-metadata --no-part --cookies {mountPath}/cookies/{video.ChannelId}.txt -o '{fileName}' '{url}'"
-                ];
-
-                // Workaround for twitcasting ERROR:
-                // Initialization fragment found after media fragments, unable to download
-                // https://github.com/yt-dlp/yt-dlp/issues/5497
-                if (url.Contains("twitcasting.tv")) args[0] = args[0].Replace("--ignore-config", "--ignore-config --downloader ffmpeg");
-            }
-
-            return (command, args);
-        }
+    /// <summary>
+    /// Builds command for cookies workaround.
+    /// Cookies file has to be mounted elsewhere and then copied,
+    /// because yt-dlp does not support using cookies file in Read-only file system,
+    /// which is how K8s handles secrets.
+    /// </summary>
+    private (string[] command, string[] args) BuildCookiesHackCommand(
+        string fileName,
+        string url,
+        bool liveFromStart,
+        string channelId,
+        string mountPath)
+    {
+        // original ENTRYPOINT: "dumb-init", "--", "yt-dlp", "--no-cache-dir"
+        var command = new[] { "dumb-init", "--", "sh", "-c" };
+
+        // Build yt-dlp args and convert to command string
+        var ytdlpArgs = BuildYtdlpArgs(fileName, url, liveFromStart);
+        var ytdlpCommand = ArgsToCommandString(ytdlpArgs);
+
+        // Insert cookies parameter
+        var cookiesPath = $"{mountPath}/cookies/{channelId}.txt";
+        ytdlpCommand = ytdlpCommand.Replace("-o ", $"--cookies {cookiesPath} -o ");
+
+        // cp under mountPath to make sure the permission is writable
+        var shellScript = $"cp -r /cookies {mountPath}/cookies && yt-dlp {ytdlpCommand}";
+        var args = new[] { shellScript };
+
+        return (command, args);
     }
 }