"""HLS manifest proxy service (Phase 3.3).

Rewrites HLS manifests and proxies .ts segments so the browser treats
them as same-origin, enabling Web Audio API access to the audio track.
"""

import logging
import re
from typing import AsyncGenerator
from urllib.parse import quote, urljoin

import httpx
from fastapi.responses import StreamingResponse

logger = logging.getLogger(__name__)


class HLSProxyService:
    """Streams and rewrites HLS manifests; proxies .ts segments with zero re-encoding."""

    async def rewrite_manifest(self, upstream_url: str, upstream: httpx.Response) -> AsyncGenerator[str, None]:
        base_url = upstream_url
        async for line in upstream.aiter_lines():
            rewritten = self._rewrite_line(line, base_url)
            yield rewritten + "\n"

    def _rewrite_line(self, line: str, base_url: str) -> str:
        stripped = line.rstrip("\r\n")

        if not stripped:
            return stripped

        if stripped.startswith("#"):
            if stripped.startswith("#EXT-X-KEY:") and 'URI="' in stripped:
                return self._rewrite_key_uri(stripped, base_url)
            return stripped

        if "://" in stripped:
            absolute_uri = stripped
        else:
            absolute_uri = urljoin(base_url, stripped)

        return self._build_proxy_url_for_uri(absolute_uri)

    def _rewrite_key_uri(self, line: str, base_url: str) -> str:
        match = re.match(r'(#EXT-X-KEY:.*URI=")(.+?)(".*)', line)
        if not match:
            return line
        prefix, uri, suffix = match.group(1), match.group(2), match.group(3)
        if "://" in uri:
            absolute_uri = uri
        else:
            absolute_uri = urljoin(base_url, uri)
        proxy_uri = self._build_proxy_url_for_uri(absolute_uri)
        return f"{prefix}{proxy_uri}{suffix}"

    def _resolve_url(self, uri: str, base_url: str) -> str:
        return urljoin(base_url, uri)

    def _build_proxy_url_for_uri(self, absolute_uri: str) -> str:
        encoded = quote(absolute_uri, safe="")
        if absolute_uri.endswith(".m3u8"):
            return f"/api/v1/youtube/proxy/manifest.m3u8?url={encoded}"
        return f"/api/v1/youtube/proxy/segment.ts?url={encoded}"

    async def proxy_segment(self, upstream_url: str) -> StreamingResponse:
        async with httpx.AsyncClient(timeout=30.0) as client:
            req = client.build_request("GET", upstream_url)
            upstream = await client.send(req, stream=True)
            return StreamingResponse(
                upstream.aiter_bytes(),
                status_code=upstream.status_code,
                media_type="video/mp2t",
                headers={"access-control-allow-origin": "*"},
            )