import subprocess
from pathlib import Path

from ..errors import AudioExtractionError
from ..logging_config import get_logger

log = get_logger(__name__)


def extract_audio(video_path: Path, audio_path: Path) -> Path:
    """Extract 16kHz mono wav from any video/audio container."""
    if audio_path.exists():
        log.info("Audio already extracted at %s, skipping", audio_path)
        return audio_path

    if not video_path.exists():
        raise AudioExtractionError(f"Uploaded file not found on disk at {video_path}. It may not have finished uploading, or the upload volume isn't mounted correctly.")

    log.info("Extracting audio: %s -> %s", video_path, audio_path)
    result = subprocess.run(
        [
            "ffmpeg", "-y", "-i", str(video_path),
            "-vn", "-acodec", "pcm_s16le", "-ar", "16000", "-ac", "1",
            str(audio_path),
        ],
        capture_output=True, text=True,
    )
    if result.returncode != 0:
        # surface ffmpeg's own error line rather than the whole verbose log
        stderr_tail = "\n".join(result.stderr.strip().splitlines()[-5:])
        raise AudioExtractionError(
            f"ffmpeg failed to extract audio (exit code {result.returncode}). "
            f"This usually means the file is corrupt or not a supported format. Last output:\n{stderr_tail}"
        )
    return audio_path


def generate_playback_audio(video_path: Path, playback_path: Path) -> Path | None:
    """Generate a compressed Opus file for browser playback (~48 kbps).

    This is done alongside the WAV extraction so the frontend can download a
    small file for instant-seeking Blob playback.  Existing sessions that lack
    the Opus file will fall back to the original upload or the extracted WAV.
    """
    if playback_path.exists():
        log.info("Playback audio already exists at %s, skipping", playback_path)
        return playback_path

    log.info("Generating playback audio: %s -> %s", video_path, playback_path)
    result = subprocess.run(
        [
            "ffmpeg", "-y", "-i", str(video_path),
            "-vn", "-c:a", "libopus", "-b:a", "48k",
            str(playback_path),
        ],
        capture_output=True, text=True,
    )
    if result.returncode != 0:
        stderr_tail = "\n".join(result.stderr.strip().splitlines()[-5:])
        log.warning("Failed to generate playback audio (non-fatal): %s", stderr_tail)
        return None
    return playback_path