"""AMR/任意音频 -> 8kHz 单声道 PCM s16le 转码。

使用系统 ffmpeg（Dockerfile 已 apt-get install ffmpeg）。
"""
from __future__ import annotations

import asyncio
import logging
from typing import Optional

logger = logging.getLogger(__name__)


async def decode_to_pcm_s16le(
    audio_bytes: bytes,
    *,
    duration_sec: int = 3,
    sample_rate: int = 8000,
    channels: int = 1,
    mime: str = "",
) -> bytes:
    """把任意音频（amr/mp3/wav/m4a 等）转成 8kHz 单声道 PCM s16le。

    Args:
        audio_bytes: 输入音频字节
        duration_sec: 截取时长（秒），默认 3
        sample_rate: 采样率，默认 8000（网易云 shazam_v2 要求）
        channels: 声道数，默认 1
        mime: MIME 类型。若为 audio/pcm 则视为已是 PCM s16le 直接截断返回

    Returns:
        PCM s16le 字节流

    Raises:
        RuntimeError: ffmpeg 失败
    """
    # 裸 PCM 直通（便于测试 / 手表若直接录 PCM 也支持）
    if mime in ("audio/pcm", "audio/x-pcm", "application/pcm"):
        needed = sample_rate * channels * 2 * duration_sec
        return audio_bytes[:needed]

    args = [
        "ffmpeg",
        "-i", "pipe:0",
        "-f", "s16le",
        "-acodec", "pcm_s16le",
        "-ar", str(sample_rate),
        "-ac", str(channels),
        "-t", str(duration_sec),
        "pipe:1",
    ]
    logger.info("[amr-decoder] ffmpeg start, input=%d bytes mime=%s", len(audio_bytes), mime)

    proc = await asyncio.create_subprocess_exec(
        *args,
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
    )
    stdout, stderr = await proc.communicate(input=audio_bytes)
    if proc.returncode != 0:
        err = stderr.decode("utf-8", errors="replace")[-500:]
        raise RuntimeError(f"ffmpeg exit {proc.returncode}: {err}")
    logger.info("[amr-decoder] ffmpeg ok, pcm=%d bytes", len(stdout))
    return stdout