# -*- coding: utf-8 -*-
"""音频流代理（FastAPI 栈）——与 Flask /audio_stream 行为逐项对齐。

要点（对齐 Flask 实现）：
- 签名校验：token 由 core.security 校验（密钥同源，两栈 token 互认）；失效 403。
- HEAD 无正文：直接 200 + Accept-Ranges，不请求上游。
- Range 透传：客户端 Range 原样转发上游，206/Content-Range 原样回传（拖动进度可用）。
- 编码透明：上游若带 Content-Encoding（aiohttp 会解压），不得沿用压缩前的
  Content-Length/Content-Range（否则头体不一致，同 Flask F92）。
- 流式转发：16KB 分块，不整段入内存；下游中断时 finally 关闭上游响应。
- Cache-Control: no-store。
"""
from fastapi import APIRouter, Request
from fastapi.responses import Response, StreamingResponse

from core import security
from core.http_client import client as http_client
from web.response import error

router = APIRouter()

_UPSTREAM_HEADERS = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36',
    'Referer': 'https://music.163.com/',
}

_CHUNK = 16 * 1024


@router.api_route('/audio_stream', methods=['GET', 'HEAD'])
async def audio_stream(request: Request):
    """签名音频代理流（支持 Range 拖动进度）。"""
    if request.method == 'HEAD':
        return Response(status_code=200, headers={'Accept-Ranges': 'bytes'})

    token = request.query_params.get('token', '')
    url = security.verify_audio_token(token)
    if not url:
        return error('音频链接已过期或无效，请重新解析', 403)

    upstream_headers = dict(_UPSTREAM_HEADERS)
    range_header = request.headers.get('range')
    if range_header:
        upstream_headers['Range'] = range_header

    try:
        upstream = await http_client.open('GET', url, headers=upstream_headers, timeout=20)
    except Exception:
        return error('音频获取失败', 502)

    if upstream.status >= 400:
        upstream.close()
        return error('音频获取失败', 502)

    upstream_encoded = bool(upstream.headers.get('Content-Encoding'))
    pass_headers: dict[str, str] = {}
    if not upstream_encoded:
        for h in ('Content-Length', 'Content-Range', 'Accept-Ranges'):
            if h in upstream.headers:
                pass_headers[h] = upstream.headers[h]
    elif 'Accept-Ranges' in upstream.headers:
        pass_headers['Accept-Ranges'] = upstream.headers['Accept-Ranges']
    pass_headers['Cache-Control'] = 'no-store'

    async def _body():
        try:
            async for chunk in upstream.content.iter_chunked(_CHUNK):
                yield chunk
        finally:
            # 下游断开/提前关闭时也释放上游连接
            upstream.close()

    return StreamingResponse(
        _body(),
        status_code=upstream.status,
        media_type=upstream.headers.get('Content-Type', 'audio/mpeg'),
        headers=pass_headers,
    )