"""Server-Sent Events manager (ROADMAP #85, tranche 4).

Singleton extrait de :mod:`backend.main` sans changement de comportement :
les routers montés par ``main`` partagent la même instance (les clients SSE
connectés sur ``/api/events`` reçoivent les broadcasts émis depuis
n'importe quel router).
"""

from __future__ import annotations

import asyncio
import json as _json
import logging

logger = logging.getLogger("obsigate")


class SSEManager:
    """Manages SSE client connections and broadcasts events."""

    def __init__(self):
        self._clients: list[asyncio.Queue] = []

    async def connect(self) -> asyncio.Queue:
        """Register a new SSE client and return its message queue."""
        queue: asyncio.Queue = asyncio.Queue()
        self._clients.append(queue)
        logger.debug(f"SSE client connected (total: {len(self._clients)})")
        return queue

    def disconnect(self, queue: asyncio.Queue):
        """Remove a disconnected SSE client."""
        if queue in self._clients:
            self._clients.remove(queue)
        logger.debug(f"SSE client disconnected (total: {len(self._clients)})")

    async def broadcast(self, event_type: str, data: dict):
        """Send an event to all connected SSE clients."""
        message = _json.dumps(data, ensure_ascii=False)
        dead: list[asyncio.Queue] = []
        for q in self._clients:
            try:
                q.put_nowait({"event": event_type, "data": message})
            except asyncio.QueueFull:
                dead.append(q)
        for q in dead:
            self.disconnect(q)

    @property
    def client_count(self) -> int:
        return len(self._clients)


sse_manager = SSEManager()