"""Minimal HTTP/3 server on aioquic (the library Hypercorn uses for QUIC). It answers the same paths as app.py.
Hypercorn's own QUIC listener proved unreliable under packet loss (its UDPServer task dies on a KeyError and the
port then goes silent), so HTTP/3 is served from here and Hypercorn serves only TCP."""
import asyncio, ssl
from aioquic.asyncio import QuicConnectionProtocol, serve as quic_serve
from aioquic.h3.connection import H3_ALPN, H3Connection
from aioquic.h3.events import HeadersReceived, DataReceived
from aioquic.quic.configuration import QuicConfiguration
from aioquic.quic.events import ProtocolNegotiated

from app import respond   # (path, http_version, host, port) -> (status, headers, body)

class H3Protocol(QuicConnectionProtocol):
    def __init__(self, *a, **kw):
        super().__init__(*a, **kw)
        self._http = None
        self._pending = {}

    def quic_event_received(self, event):
        if isinstance(event, ProtocolNegotiated) and event.alpn_protocol in H3_ALPN:
            self._http = H3Connection(self._quic)
        if self._http is None:
            return
        for ev in self._http.handle_event(event):
            if isinstance(ev, HeadersReceived):
                self._pending[ev.stream_id] = dict(ev.headers)
                if ev.stream_ended: self._reply(ev.stream_id)
            elif isinstance(ev, DataReceived) and ev.stream_ended:
                self._reply(ev.stream_id)

    def _reply(self, stream_id):
        h = self._pending.pop(stream_id, None)
        if h is None: return
        status, headers, body = respond(h[b":path"].decode(), "3", "127.0.0.1", self._port)
        self._http.send_headers(stream_id, [(b":status", str(status).encode())] + headers)
        self._http.send_data(stream_id, body, end_stream=True)
        self.transmit()

    _port = 4433

async def start(port, certfile, keyfile):
    H3Protocol._port = port
    cfg = QuicConfiguration(is_client=False, alpn_protocols=H3_ALPN)
    cfg.load_cert_chain(certfile, keyfile)
    await quic_serve("127.0.0.1", port, configuration=cfg, create_protocol=H3Protocol)
    await asyncio.Event().wait()