import os
import shutil
import subprocess
import json
from typing import Optional


def _find_ffmpeg() -> str:
    path = shutil.which("ffmpeg")
    if path:
        return path
    winget_path = os.path.join(
        os.environ.get("LOCALAPPDATA", ""),
        "Microsoft", "WinGet", "Links", "ffmpeg.exe"
    )
    if os.path.exists(winget_path):
        return winget_path
    alt_paths = [
        r"C:\ffmpeg\bin\ffmpeg.exe",
        r"C:\Program Files\ffmpeg\bin\ffmpeg.exe",
    ]
    for p in alt_paths:
        if os.path.exists(p):
            return p
    raise RuntimeError("FFmpeg not found. Install it via: winget install ffmpeg")


def get_audio_channels(input_path: str) -> int:
    ffmpeg_path = _find_ffmpeg()
    cmd = [
        ffmpeg_path, "-i", input_path,
        "-f", "null", "-"
    ]
    result = subprocess.run(cmd, capture_output=True, text=True)
    stderr = result.stderr
    for line in stderr.split("\n"):
        if "Audio:" in line:
            if "stereo" in line or "2 channels" in line:
                return 2
            elif "mono" in line or "1 channel" in line:
                return 1
            import re
            m = re.search(r"(\d+)\s+channels?", line)
            if m:
                return int(m.group(1))
    return 2


def convert_to_wav(input_path: str, output_dir: str, sample_rate: int = 16000) -> Optional[str]:
    os.makedirs(output_dir, exist_ok=True)
    base = os.path.splitext(os.path.basename(input_path))[0]
    output_path = os.path.join(output_dir, f"{base}_16khz.wav")

    channels = get_audio_channels(input_path)
    ac = "2" if channels == 2 else "1"

    ffmpeg_path = _find_ffmpeg()
    cmd = [
        ffmpeg_path, "-y",
        "-i", input_path,
        "-acodec", "pcm_s16le",
        "-ac", ac,
        "-ar", str(sample_rate),
        output_path
    ]
    result = subprocess.run(cmd, capture_output=True, text=True)
    if result.returncode != 0:
        raise RuntimeError(f"FFmpeg error: {result.stderr}")
    return output_path, channels


def split_stereo_channels(wav_path: str, output_dir: str) -> tuple[Optional[str], Optional[str]]:
    base = os.path.splitext(os.path.basename(wav_path))[0]
    left_path = os.path.join(output_dir, f"{base}_left.wav")
    right_path = os.path.join(output_dir, f"{base}_right.wav")
    ffmpeg_path = _find_ffmpeg()

    cmd = [
        ffmpeg_path, "-y",
        "-i", wav_path,
        "-filter_complex", "[0:a]pan=mono|c0=c0[left];[0:a]pan=mono|c0=c1[right]",
        "-map", "[left]", left_path,
        "-map", "[right]", right_path,
    ]
    result = subprocess.run(cmd, capture_output=True, text=True)
    if result.returncode != 0:
        raise RuntimeError(f"FFmpeg split error: {result.stderr}")
    return left_path, right_path