#!/usr/bin/env python3
"""Build a final voice-over video on Ubuntu with ffmpeg."""

from __future__ import annotations

import argparse
import shutil
import subprocess
from pathlib import Path


AUDIO_EXTS = {".mp3", ".wav", ".m4a", ".aac", ".flac", ".ogg"}


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


def require_tool(name: str) -> str:
    path = shutil.which(name)
    if not path:
        raise SystemExit(f"{name} is required. Install it with: sudo apt install -y ffmpeg")
    return path


def media_duration(path: Path) -> float:
    result = subprocess.check_output(
        [
            "ffprobe",
            "-v",
            "error",
            "-show_entries",
            "format=duration",
            "-of",
            "default=nw=1:nk=1",
            str(path),
        ],
        text=True,
    ).strip()
    return float(result)


def audio_files(audio_dir: Path) -> list[Path]:
    files = [
        path
        for path in sorted(audio_dir.iterdir())
        if path.is_file() and path.suffix.lower() in AUDIO_EXTS
    ]
    if not files:
        raise FileNotFoundError(f"No audio files found in {audio_dir}")
    return files


def concat_audio_dir(audio_dir: Path, work_dir: Path, silence: float) -> Path:
    work_dir.mkdir(parents=True, exist_ok=True)
    normalized: list[Path] = []
    silence_path = work_dir / "silence.wav"
    run(
        [
            "ffmpeg",
            "-hide_banner",
            "-loglevel",
            "error",
            "-y",
            "-f",
            "lavfi",
            "-t",
            f"{silence:.3f}",
            "-i",
            "anullsrc=channel_layout=stereo:sample_rate=48000",
            "-c:a",
            "pcm_s16le",
            str(silence_path),
        ]
    )

    for index, src in enumerate(audio_files(audio_dir), start=1):
        dst = work_dir / f"audio_{index:02d}.wav"
        run(
            [
                "ffmpeg",
                "-hide_banner",
                "-loglevel",
                "error",
                "-y",
                "-i",
                str(src),
                "-vn",
                "-ar",
                "48000",
                "-ac",
                "2",
                "-c:a",
                "pcm_s16le",
                str(dst),
            ]
        )
        normalized.append(dst)

    concat_items: list[Path] = []
    for index, item in enumerate(normalized):
        concat_items.append(item)
        if index != len(normalized) - 1 and silence > 0:
            concat_items.append(silence_path)

    list_path = work_dir / "audio_concat.txt"
    with list_path.open("w", encoding="utf-8") as handle:
        for item in concat_items:
            escaped = item.resolve().as_posix().replace("'", "'\\''")
            handle.write(f"file '{escaped}'\n")

    out_audio = work_dir / "combined_voice.wav"
    run(
        [
            "ffmpeg",
            "-hide_banner",
            "-loglevel",
            "error",
            "-y",
            "-f",
            "concat",
            "-safe",
            "0",
            "-i",
            str(list_path),
            "-c:a",
            "pcm_s16le",
            str(out_audio),
        ]
    )
    return out_audio


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Combine one video with voice-over audio.")
    parser.add_argument("--video", type=Path, required=True, help="Source video path.")
    parser.add_argument("--audio", type=Path, default=None, help="Single voice-over audio file.")
    parser.add_argument("--audio-dir", type=Path, default=None, help="Directory of ordered audio files.")
    parser.add_argument("--output", type=Path, default=Path("05_outputs/final_voiceover.mp4"))
    parser.add_argument("--work-dir", type=Path, default=Path("04_intermediate/ubuntu_voiceover"))
    parser.add_argument("--silence", type=float, default=0.35, help="Gap seconds between audio files.")
    parser.add_argument("--width", type=int, default=1920)
    parser.add_argument("--height", type=int, default=1080)
    parser.add_argument("--fps", type=int, default=30)
    parser.add_argument("--crf", type=int, default=20)
    parser.add_argument("--preset", default="medium")
    parser.add_argument("--video-speed", type=float, default=None, help="Override automatic speed.")
    return parser.parse_args()


def main() -> int:
    args = parse_args()
    require_tool("ffmpeg")
    require_tool("ffprobe")

    if not args.video.exists():
        raise FileNotFoundError(args.video)
    if bool(args.audio) == bool(args.audio_dir):
        raise SystemExit("Use exactly one of --audio or --audio-dir.")

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

    audio_path = args.audio if args.audio else concat_audio_dir(args.audio_dir, args.work_dir, args.silence)
    if not audio_path or not audio_path.exists():
        raise FileNotFoundError(audio_path)

    video_duration = media_duration(args.video)
    audio_duration = media_duration(audio_path)
    if video_duration <= 0 or audio_duration <= 0:
        raise RuntimeError("Invalid media duration.")

    speed = args.video_speed if args.video_speed else video_duration / audio_duration
    if speed <= 0:
        raise ValueError("--video-speed must be greater than 0.")

    print(f"video_duration={video_duration:.3f}s")
    print(f"audio_duration={audio_duration:.3f}s")
    print(f"video_speed={speed:.6f}x")

    vf = (
        f"[0:v]setpts=PTS/{speed:.8f},fps={args.fps},"
        f"scale={args.width}:{args.height}:force_original_aspect_ratio=decrease,"
        f"pad={args.width}:{args.height}:(ow-iw)/2:(oh-ih)/2:black,"
        "setsar=1,format=yuv420p[v];"
        "[1:a]aresample=48000,apad[a]"
    )
    run(
        [
            "ffmpeg",
            "-hide_banner",
            "-y",
            "-i",
            str(args.video),
            "-i",
            str(audio_path),
            "-filter_complex",
            vf,
            "-map",
            "[v]",
            "-map",
            "[a]",
            "-t",
            f"{audio_duration:.3f}",
            "-c:v",
            "libx264",
            "-preset",
            args.preset,
            "-crf",
            str(args.crf),
            "-c:a",
            "aac",
            "-b:a",
            "192k",
            "-ar",
            "48000",
            "-ac",
            "2",
            "-movflags",
            "+faststart",
            str(args.output),
        ]
    )
    final_duration = media_duration(args.output)
    print(f"output={args.output}")
    print(f"final_duration={final_duration:.3f}s")
    return 0


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