#!/usr/bin/env python3
"""Concatenate merged_*.mp4 files into a single output using ffmpeg concat demuxer."""

from __future__ import annotations

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

from logging_config import configure_logging, debug_log_lifecycle


SCRIPT_DIR = Path(__file__).resolve().parent
DEFAULT_BASE_DIR = SCRIPT_DIR.parents[1]
DEFAULT_MERGED_DIR = DEFAULT_BASE_DIR / "merged"
DEFAULT_OUTPUT = DEFAULT_BASE_DIR / "results" / "run_3" / "final_output.mp4"

LOGGER = logging.getLogger(__name__)


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


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--merged-dir", type=Path, default=DEFAULT_MERGED_DIR)
    parser.add_argument("--output", type=Path, default=DEFAULT_OUTPUT)
    parser.add_argument(
        "--log-level",
        default=None,
        help="Logging level (overrides LOG_LEVEL env var)",
    )
    return parser.parse_args()


@debug_log_lifecycle
def main() -> int:
    args = parse_args()
    configure_logging(args.log_level)

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

    args.output.parent.mkdir(parents=True, exist_ok=True)

    with tempfile.NamedTemporaryFile(mode="w", suffix=".txt", delete=False) as tmp:
        filelist = Path(tmp.name)
        for video in videos:
            tmp.write(f"file '{video}'\\n")

    try:
        LOGGER.info("Concatenating the following files:\n%s", filelist.read_text().rstrip())

        subprocess.run(
            [
                "ffmpeg",
                "-f",
                "concat",
                "-safe",
                "0",
                "-i",
                str(filelist),
                "-c",
                "copy",
                "-y",
                str(args.output),
            ],
            check=True,
        )
    finally:
        filelist.unlink(missing_ok=True)

    LOGGER.info("Done")
    return 0


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