# core/assembler.py
"""
Assembler combines video + music and optionally overlays images/text,
and produces final assembled output. Uses ffmpeg for merging audio/video.
Returns a dict with final path and metadata.
"""
import subprocess
import time
from pathlib import Path
from typing import Dict
from config import OUTPUT_DIR

OUTPUT_DIR = Path(OUTPUT_DIR)
OUTPUT_DIR.mkdir(parents=True, exist_ok=True)

def assemble_video(video_result: Dict, music_result: Dict, out_name: str = None) -> Dict:
    """
    video_result: dict returned from video_generator
    music_result: dict returned from music_generator
    Returns dict { "final_path":..., "duration":..., "meta":... }
    """
    t0 = time.time()
    video_path = Path(video_result.get("video_path"))
    music_path = Path(music_result.get("music_path"))
    out_name = out_name or f"final_{int(time.time()*1000)}.mp4"
    out_path = OUTPUT_DIR / out_name

    # If ffmpeg is available, merge audio and video
    if video_path.exists() and music_path.exists():
        cmd = [
            "ffmpeg", "-y",
            "-i", str(video_path),
            "-i", str(music_path),
            "-c:v", "copy",  # copy video stream
            "-c:a", "aac",
            "-shortest",
            str(out_path)
        ]
        try:
            subprocess.run(cmd, check=True, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
            duration = video_result.get("duration", 0.0)
        except Exception as e:
            print(f"[assembler] ffmpeg merge failed: {e}. Creating placeholder final output.")
            with open(out_path, "wb") as f:
                f.write(b"")
            duration = 0.0
    else:
        # If audio or video missing, create a placeholder
        with open(out_path, "wb") as f:
            f.write(b"")
        duration = 0.0

    meta = {
        "video_src": str(video_path),
        "music_src": str(music_path),
        "assembled_at": time.time() - t0
    }
    return {"final_path": str(out_path), "duration": duration, "meta": meta}