import argparse
import subprocess
from pathlib import Path


def resolve_path(value: str) -> Path:
    return Path(value).expanduser().resolve()


def run(command: list[str]) -> None:
    print("Running:", " ".join(command))
    subprocess.run(command, check=True)


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Replace a video's original audio with a new voiceover audio file."
    )
    parser.add_argument("--video", required=True, help="Input video file, for example input/tutorial.mp4")
    parser.add_argument("--audio", required=True, help="Input voiceover audio file, for example output/voiceover.wav")
    parser.add_argument("--output", required=True, help="Output MP4 file, for example output/final_video.mp4")
    parser.add_argument(
        "--reencode-video",
        action="store_true",
        help="Re-encode video with H.264 instead of copying. Use only if the copied output has playback issues.",
    )
    args = parser.parse_args()

    video_file = resolve_path(args.video)
    audio_file = resolve_path(args.audio)
    output_file = resolve_path(args.output)

    if not video_file.exists():
        raise FileNotFoundError(f"Video not found: {video_file}")
    if not audio_file.exists():
        raise FileNotFoundError(f"Audio not found: {audio_file}")

    output_file.parent.mkdir(parents=True, exist_ok=True)

    video_codec_args = ["-c:v", "libx264", "-preset", "medium", "-crf", "18"] if args.reencode_video else ["-c:v", "copy"]

    command = [
        "ffmpeg", "-y",
        "-i", str(video_file),
        "-i", str(audio_file),
        "-map", "0:v:0",      # video from first input
        "-map", "1:a:0",      # audio from second input only, so original video audio is muted/removed
        *video_codec_args,
        "-c:a", "aac",
        "-b:a", "192k",
        "-movflags", "+faststart",
        str(output_file),
    ]
    run(command)
    print(f"Done: {output_file}")


if __name__ == "__main__":
    main()