from __future__ import annotations

import json
import shutil
import subprocess
from pathlib import Path


def require_binary(name: str) -> str:
    path = shutil.which(name)
    if not path:
        raise RuntimeError(f"Required executable '{name}' was not found in PATH.")
    return path


def run(command: list[str]) -> None:
    process = subprocess.run(command, text=True)
    if process.returncode != 0:
        raise RuntimeError(f"Command failed with exit code {process.returncode}: {' '.join(command)}")


def extract_audio(media_path: Path, wav_path: Path, sample_rate: int = 16000) -> Path:
    require_binary("ffmpeg")
    wav_path.parent.mkdir(parents=True, exist_ok=True)
    run([
        "ffmpeg", "-y", "-i", str(media_path),
        "-vn", "-ac", "1", "-ar", str(sample_rate),
        "-c:a", "pcm_s16le", str(wav_path),
    ])
    return wav_path


def probe_fps(media_path: Path) -> float:
    require_binary("ffprobe")
    result = subprocess.run([
        "ffprobe", "-v", "error", "-select_streams", "v:0",
        "-show_entries", "stream=avg_frame_rate", "-of", "json", str(media_path)
    ], capture_output=True, text=True, check=True)
    data = json.loads(result.stdout)
    rate = data["streams"][0]["avg_frame_rate"]
    num, den = rate.split("/")
    return float(num) / float(den)


def render_ass(media_path: Path, ass_path: Path, output_path: Path) -> Path:
    require_binary("ffmpeg")
    escaped = str(ass_path.resolve()).replace("\\", "/").replace(":", "\\:")
    output_path.parent.mkdir(parents=True, exist_ok=True)
    run([
        "ffmpeg", "-y", "-i", str(media_path),
        "-vf", f"ass='{escaped}'",
        "-c:v", "libx264", "-preset", "slow", "-crf", "16",
        "-c:a", "copy", str(output_path),
    ])
    return output_path