import json

from channels.db import database_sync_to_async
from channels.generic.websocket import AsyncJsonWebsocketConsumer

from .models import BoardSession


class BoardConsumer(AsyncJsonWebsocketConsumer):
    async def connect(self):
        self.session_id = self.scope["url_route"]["kwargs"]["session_id"]
        self.group_name = f"board_{self.session_id}"
        user = self.scope["user"]
        if not user.is_authenticated or not await self._is_participant(user.id):
            await self.close(code=4403)
            return
        await self.channel_layer.group_add(self.group_name, self.channel_name)
        await self.accept()
        await self.send_json(
            {
                "type": "connected",
                "session_id": str(self.session_id),
            }
        )

    async def disconnect(self, close_code):
        if hasattr(self, "group_name"):
            await self.channel_layer.group_discard(
                self.group_name,
                self.channel_name,
            )

    async def receive_json(self, content, **kwargs):
        event_type = content.get("type")
        if event_type == "ping":
            await self.send_json({"type": "pong"})
            return
        if event_type not in {"canvas", "geometry"}:
            await self.send_json({"type": "error", "message": "不支持的画板消息"})
            return
        if not await self._is_active():
            await self.send_json({"type": "error", "message": "画板尚未开始或已经结束"})
            return
        payload = content.get("payload")
        if event_type == "canvas":
            valid = (
                isinstance(payload, str)
                and payload.startswith("data:image/")
                and len(payload) <= 700_000
            )
        else:
            valid = isinstance(payload, dict) and len(
                json.dumps(payload, ensure_ascii=False)
            ) <= 100_000
        if not valid:
            await self.send_json({"type": "error", "message": "画板消息无效或过大"})
            return
        await self.channel_layer.group_send(
            self.group_name,
            {
                "type": "board.update",
                "event_type": event_type,
                "payload": payload,
                "user_id": str(self.scope["user"].id),
            },
        )

    async def board_update(self, event):
        await self.send_json(
            {
                "type": event["event_type"],
                "payload": event["payload"],
                "user_id": event["user_id"],
            }
        )

    async def board_state(self, event):
        await self.send_json(
            {
                "type": "state",
                "reason": event["reason"],
                "session_id": str(self.session_id),
            }
        )

    @database_sync_to_async
    def _is_participant(self, user_id):
        return BoardSession.objects.filter(id=self.session_id).filter(
            host_id=user_id
        ).exists() or BoardSession.objects.filter(
            id=self.session_id,
            guest_id=user_id,
        ).exists()

    @database_sync_to_async
    def _is_active(self):
        return BoardSession.objects.filter(
            id=self.session_id,
            status=BoardSession.Status.ACTIVE,
        ).exists()