gogo-telefon/gogo/voice/server.py

"""AudioSocket server — Asterisk connects here per agent-handled call (M4).

AudioSocket wire protocol (Asterisk `AudioSocket()` app):
    1 byte kind | 2 bytes big-endian payload length | payload
    kind 0x00 = terminate, 0x01 = UUID (16 raw bytes), 0x10 = SLIN audio,
    0xff = error. Audio is 16-bit LE mono PCM @ 8 kHz, ~20 ms per message.

Run:  python -m gogo.voice.server
"""

from __future__ import annotations

import asyncio
import logging
import uuid

from gogo.config import get_settings
from gogo.voice.call import CallSession, Transport

log = logging.getLogger("gogo.voice.server")

KIND_TERMINATE = 0x00
KIND_UUID = 0x01
KIND_AUDIO = 0x10
KIND_ERROR = 0xFF


class AudioSocketTransport(Transport):
    def __init__(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter):
        self.reader = reader
        self.writer = writer
        self._closed = False

    async def read_message(self) -> tuple[int, bytes] | None:
        try:
            header = await self.reader.readexactly(3)
        except (asyncio.IncompleteReadError, ConnectionResetError):
            return None
        kind = header[0]
        length = int.from_bytes(header[1:3], "big")
        payload = b""
        if length:
            try:
                payload = await self.reader.readexactly(length)
            except (asyncio.IncompleteReadError, ConnectionResetError):
                return None
        return kind, payload

    async def read_frame(self) -> bytes | None:
        """Next audio frame; skips non-audio messages; None on hangup/close."""
        while True:
            msg = await self.read_message()
            if msg is None:
                return None
            kind, payload = msg
            if kind == KIND_AUDIO:
                return payload
            if kind == KIND_TERMINATE:
                return None
            if kind == KIND_ERROR:
                log.warning("audiosocket error frame: %s", payload[:64])

    async def send_audio(self, pcm: bytes) -> None:
        if self._closed:
            return
        try:
            self.writer.write(bytes([KIND_AUDIO]) + len(pcm).to_bytes(2, "big") + pcm)
            await self.writer.drain()
        except (ConnectionResetError, BrokenPipeError):
            self._closed = True

    async def hangup(self) -> None:
        if self._closed:
            return
        self._closed = True
        try:
            self.writer.write(bytes([KIND_TERMINATE, 0, 0]))
            await self.writer.drain()
            self.writer.close()
        except (ConnectionResetError, BrokenPipeError):
            pass


async def handle_connection(reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
    transport = AudioSocketTransport(reader, writer)
    msg = await transport.read_message()
    if msg is None or msg[0] != KIND_UUID or len(msg[1]) != 16:
        log.warning("connection without UUID handshake — dropping")
        await transport.hangup()
        return
    registration_id = uuid.UUID(bytes=msg[1])
    log.info("call connected: %s", registration_id)
    session = CallSession(transport, registration_id)
    await session.run()


async def serve() -> None:
    s = get_settings()
    server = await asyncio.start_server(handle_connection, s.voice_host, s.voice_port)
    addrs = ", ".join(str(sock.getsockname()) for sock in server.sockets)
    log.info("AudioSocket server listening on %s", addrs)
    # health heartbeat file for the admin panel / monitoring (M6)
    async with server:
        await server.serve_forever()


def main() -> None:
    logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(name)s %(message)s")
    asyncio.run(serve())


if __name__ == "__main__":
    main()