"""
WebSocket Manager - WebSocket 连接管理器
Manages client connections, topic subscriptions, and broadcasting.
"""

import asyncio
import json
import logging
from datetime import datetime, timezone

from fastapi import WebSocket

logger = logging.getLogger(__name__)

# Maximum concurrent WebSocket connections
MAX_CONNECTIONS = 100

# Valid topics
VALID_TOPICS = {"location", "alarm", "device_status", "attendance", "bluetooth"}


class WebSocketManager:
    """Manages WebSocket connections with topic-based subscriptions."""

    def __init__(self):
        # {websocket: set_of_topics}
        self.active_connections: dict[WebSocket, set[str]] = {}

    @property
    def connection_count(self) -> int:
        return len(self.active_connections)

    async def connect(self, websocket: WebSocket, topics: set[str]) -> bool:
        """Accept and register a WebSocket connection. Returns False if limit reached."""
        if self.connection_count >= MAX_CONNECTIONS:
            await websocket.close(code=1013, reason="Max connections reached")
            return False

        await websocket.accept()
        filtered = topics & VALID_TOPICS
        self.active_connections[websocket] = filtered if filtered else VALID_TOPICS
        logger.info(
            "WebSocket connected (%d total), topics: %s",
            self.connection_count,
            self.active_connections[websocket],
        )
        return True

    def disconnect(self, websocket: WebSocket):
        """Remove a WebSocket connection."""
        self.active_connections.pop(websocket, None)
        logger.info("WebSocket disconnected (%d remaining)", self.connection_count)

    async def broadcast(self, topic: str, data: dict):
        """Broadcast a message to all subscribers of the given topic."""
        if topic not in VALID_TOPICS:
            return

        message = json.dumps(
            {"topic": topic, "data": data, "timestamp": datetime.now(timezone.utc).isoformat()},
            default=str,
            ensure_ascii=False,
        )

        disconnected = []
        # Snapshot dict to avoid RuntimeError from concurrent modification
        for ws, topics in list(self.active_connections.items()):
            if topic in topics:
                try:
                    await ws.send_text(message)
                except Exception:
                    disconnected.append(ws)

        for ws in disconnected:
            self.active_connections.pop(ws, None)

    def broadcast_nonblocking(self, topic: str, data: dict):
        """Fire-and-forget broadcast (used from TCP handler context)."""
        asyncio.create_task(self._safe_broadcast(topic, data))

    async def _safe_broadcast(self, topic: str, data: dict):
        try:
            await self.broadcast(topic, data)
        except Exception:
            logger.exception("WebSocket broadcast error for topic %s", topic)


# Singleton instance
ws_manager = WebSocketManager()