import json
import asyncio
from channels.generic.websocket import AsyncWebsocketConsumer
from django.core.cache import cache


class QRStatusConsumer(AsyncWebsocketConsumer):
    """
    扫码登录 WebSocket Consumer.
    前端连接 ws://host/ws/qr-status/{token}/，
    后端在扫码/确认/取消/过期时实时推送状态。
    """

    async def connect(self):
        self.qr_token = self.scope['url_route']['kwargs']['token']
        self.group_name = f"qr_{self.qr_token}"

        # 加入该 token 对应的 group
        await self.channel_layer.group_add(self.group_name, self.channel_name)
        await self.accept()

        # 检查 token 是否已过期/不存在
        data = cache.get(f"qr_token:{self.qr_token}")
        if not data:
            await self.send(text_data=json.dumps({"status": "expired"}))
            await self.close()
            return

        # 启动过期倒计时任务
        self._expire_task = asyncio.create_task(self._expire_watcher(data.get("expires_at")))

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

    async def receive(self, text_data):
        """客户端不需要发送消息，忽略即可"""
        pass

    # ── group 消息处理器：由 views 通过 group_send 触发 ──

    async def qr_status_update(self, event):
        """接收扫码/确认/取消状态推送"""
        message = {"status": event["status"]}
        if event.get("username"):
            message["username"] = event["username"]
        if event.get("auth"):
            message["auth"] = event["auth"]
        await self.send(text_data=json.dumps(message))

        # confirmed 或 cancelled 后关闭连接
        if event["status"] in ("confirmed", "cancelled", "expired"):
            await self.close()

    # ── 内部方法 ──

    async def _expire_watcher(self, expires_at):
        """Token 过期时主动推送 expired 并关闭"""
        if not expires_at:
            return
        import time
        wait = max(expires_at - time.time(), 0) + 1  # 多等 1 秒确保 Redis 已清除
        try:
            await asyncio.sleep(wait)
        except asyncio.CancelledError:
            return

        # token 已过期
        await self.send(text_data=json.dumps({"status": "expired"}))
        await self.close()