#!/usr/bin/env python3
"""Merge videos/output_n.mp4 with audios/output_n.mp3 into merged/merged_n.mp4."""

from __future__ import annotations

import argparse
import logging
import re
import shutil
import subprocess
from pathlib import Path

from src.logging_config import configure_logging


SCRIPT_DIR = Path(__file__).resolve().parent
DEFAULT_BASE_DIR = SCRIPT_DIR.parents[1]
DEFAULT_VIDEOS_DIR = DEFAULT_BASE_DIR / "videos"
DEFAULT_AUDIOS_DIR = DEFAULT_BASE_DIR / "audios"
DEFAULT_OUTPUT_DIR = DEFAULT_BASE_DIR / "merged"

LOGGER = logging.getLogger(__name__)


def shot_number(path: Path) -> int:
    match = re.search(r"output_(\d+)\.mp4$", path.name)
    return int(match.group(1)) if match else -1


def parse_args(argv: list[str] | None = None) -> argparse.Namespace:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--videos-dir", type=Path, default=DEFAULT_VIDEOS_DIR)
    parser.add_argument("--audios-dir", type=Path, default=DEFAULT_AUDIOS_DIR)
    parser.add_argument("--output-dir", type=Path, default=DEFAULT_OUTPUT_DIR)
    parser.add_argument(
        "--allow-missing-audio",
        action="store_true",
        help="If set, create merged output from video only when audio is missing.",
    )
    parser.add_argument("--log-level", default="INFO")
    return parser.parse_args(argv)


def main(argv: list[str] | None = None) -> int:
    args = parse_args(argv)
    configure_logging(args.log_level)
    args.output_dir.mkdir(parents=True, exist_ok=True)

    videos = sorted(args.videos_dir.glob("output_*.mp4"), key=shot_number)
    if not videos:
        LOGGER.warning("No videos found in %s", args.videos_dir)
        return 1

    for video in videos:
        num = shot_number(video)
        audio = args.audios_dir / f"output_{num}.mp3"
        output = args.output_dir / f"merged_{num}.mp4"

        if output.exists():
            LOGGER.info("Already exists; skipped shot %s", num)
            continue

        if not audio.exists():
            if args.allow_missing_audio:
                LOGGER.warning(
                    "No audio found for shot %s (%s); using video-only output",
                    num,
                    audio,
                )
                shutil.copy2(video, output)
                LOGGER.info("Done (video-only): %s", output)
                continue

            LOGGER.warning("No audio found for shot %s (%s); skipped", num, audio)
            continue

        LOGGER.info("Merging shot %s: %s + %s -> %s", num, video, audio, output)
        subprocess.run(
            [
                "ffmpeg",
                "-i",
                str(video),
                "-i",
                str(audio),
                "-c:v",
                "copy",
                "-c:a",
                "aac",
                "-shortest",
                "-y",
                str(output),
            ],
            check=True,
        )
        LOGGER.info("Done: %s", output)

    return 0


if __name__ == "__main__":
    raise SystemExit(main())