import json
import os
import asyncio

video_path = params_kw.get('video_path', '')
vocals_path = params_kw.get('vocals_path', '')
accompaniment_path = params_kw.get('accompaniment_path', '')
subtitle_path = params_kw.get('subtitle_path', '')
output_name = params_kw.get('output_name', 'ktv_output')

output_dir = os.path.join('/tmp/ffmpeg_output', output_name)
os.makedirs(output_dir, exist_ok=True)

output_path = os.path.join(output_dir, 'output.mkv')

try:
    missing = []
    if not video_path:
        missing.append('video_path')
    if not vocals_path:
        missing.append('vocals_path')
    if not accompaniment_path:
        missing.append('accompaniment_path')
    if not subtitle_path:
        missing.append('subtitle_path')

    if missing:
        result = json.dumps({"status": "error", "error": f"Missing required params: {', '.join(missing)}"})
    elif not os.path.isfile(video_path):
        result = json.dumps({"status": "error", "error": f"Video file not found: {video_path}"})
    elif not os.path.isfile(vocals_path):
        result = json.dumps({"status": "error", "error": f"Vocals file not found: {vocals_path}"})
    elif not os.path.isfile(accompaniment_path):
        result = json.dumps({"status": "error", "error": f"Accompaniment file not found: {accompaniment_path}"})
    elif not os.path.isfile(subtitle_path):
        result = json.dumps({"status": "error", "error": f"Subtitle file not found: {subtitle_path}"})
    else:
        proc = await asyncio.create_subprocess_exec(
            'ffmpeg', '-y',
            '-i', video_path,
            '-i', vocals_path,
            '-i', accompaniment_path,
            '-vf', f"ass={subtitle_path}",
            '-map', '0:v',
            '-map', '1:a',
            '-map', '2:a',
            '-c:v', 'libx264',
            '-c:a', 'aac',
            output_path,
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.PIPE
        )
        stdout, stderr = await proc.communicate()

        if proc.returncode == 0:
            result = json.dumps({"status": "success", "output_path": output_path})
        else:
            result = json.dumps({"status": "error", "error": stderr.decode()})

except Exception as e:
    result = json.dumps({"status": "error", "error": str(e)})

return result