#!/usr/bin/env python3
"""
Minimal signalling relay for WebRTC data‑channel projects.

Contract:
• Client sends {"type":"register","id": "..."} once on connect.
• Later it sends {"type":"signal","from": "...", "target": "...", "data": {...}}
  The server forwards that JSON verbatim to the socket whose id == target.
"""

import asyncio, json, logging
import websockets

logging.basicConfig(level=logging.INFO)
CLIENTS: dict[str, websockets.WebSocketServerProtocol] = {}

async def handler(ws: websockets.WebSocketServerProtocol):
    peer_id = None
    try:
        async for raw in ws:
            try:
                msg = json.loads(raw)
            except json.JSONDecodeError:
                logging.warning("Bad JSON from %s: %s", peer_id, raw)
                continue

            mtype = msg.get("type")
            if mtype == "register":
                peer_id = msg.get("id")
                if not peer_id:
                    await ws.close(code=4000, reason="Missing id")
                    return
                CLIENTS[peer_id] = ws
                logging.info("Registered %s (%d clients)", peer_id, len(CLIENTS))

            elif mtype == "signal":
                target = msg.get("target")
                if not target:
                    continue
                dest = CLIENTS.get(target)
                if dest:
                    await dest.send(raw)             # relay as‑is
                    logging.debug("Relayed %s → %s", peer_id, target)
                else:
                    logging.warning("Target %s not found", target)

    except websockets.ConnectionClosed:
        pass
    finally:
        # tidy up on disconnect
        if peer_id and CLIENTS.get(peer_id) is ws:
            CLIENTS.pop(peer_id)
            logging.info("Disconnected %s (%d clients left)", peer_id, len(CLIENTS))

async def main():
    async with websockets.serve(handler, host="0.0.0.0", port=8080):
        logging.info("Signalling server listening on :8080")
        await asyncio.Future()            # run forever

if __name__ == "__main__":
    asyncio.run(main())