refactor: improve error handling and response formatting in API endpoints

with_ui.py

@@ -71,15 +71,17 @@ def get_info():
             cmd, capture_output=True, text=True, timeout=30, cwd=DOWNLOAD_DIR
         )
         if result.returncode != 0:
-            return jsonify({"error": result.stderr or "Failed to fetch info"}), 400
+            msg = result.stderr or "Failed to fetch info"
+            return jsonify({"error": msg}), 400
         info = json.loads(result.stdout)
         formats = []
         for f in info.get("formats", []):
+            res = f.get("resolution") or f.get("format_note") or ""
             formats.append(
                 {
                     "id": f.get("format_id"),
                     "ext": f.get("ext"),
-                    "resolution": f.get("resolution") or f.get("format_note") or "",
+                    "resolution": res,
                     "vcodec": f.get("vcodec", "none"),
                     "acodec": f.get("acodec", "none"),
                     "filesize": f.get("filesize") or f.get("filesize_approx"),
@@ -125,7 +127,11 @@ def start_download():
     cmd.append(url)
 
     job_id = str(uuid.uuid4())
-    thread = threading.Thread(target=run_ytdlp, args=(job_id, cmd), daemon=True)
+    thread = threading.Thread(
+        target=run_ytdlp,
+        args=(job_id, cmd),
+        daemon=True,
+    )
     thread.start()
 
     return jsonify({"job_id": job_id})
@@ -139,14 +145,17 @@ def job_status(job_id):
             with jobs_lock:
                 job = jobs.get(job_id)
             if not job:
-                yield f"data: {json.dumps({'error': 'Job not found'})}\n\n"
+                payload = json.dumps({"error": "Job not found"})
+                yield "data: " + payload + "\n\n"
                 break
             lines = job["lines"]
             while sent < len(lines):
-                yield f"data: {json.dumps({'line': lines[sent]})}\n\n"
+                payload = json.dumps({"line": lines[sent]})
+                yield "data: " + payload + "\n\n"
                 sent += 1
             if job["done"]:
-                yield f"data: {json.dumps({'done': True, 'error': job['error']})}\n\n"
+                payload = json.dumps({"done": True, "error": job["error"]})
+                yield "data: " + payload + "\n\n"
                 break
             time.sleep(0.2)
 
@@ -158,6 +167,6 @@ def job_status(job_id):
 
 
 if __name__ == "__main__":
-    print(f"[yt-dlp UI] Serving on http://localhost:5000")
-    print(f"[yt-dlp UI] Download directory: {DOWNLOAD_DIR}")
+    print("[yt-dlp UI] Serving on http://localhost:5000")
+    print("[yt-dlp UI] Download directory: {}".format(DOWNLOAD_DIR))
     app.run(debug=False, host="0.0.0.0", port=5000, threaded=True)