from rest_framework import viewsets, status, mixins, parsers
from rest_framework.decorators import action
from rest_framework.response import Response
from rest_framework import serializers
from django.core.signing import TimestampSigner, BadSignature, SignatureExpired
from drf_spectacular.utils import extend_schema

from shop.models import WeChatUser
from .models import Activity, ActivitySignup, Topic, Reply, TopicMedia
from .serializers import ActivitySerializer, ActivitySignupSerializer, TopicSerializer, ReplySerializer, TopicMediaSerializer

def get_current_wechat_user(request):
    """
    根据 Authorization 头获取当前微信用户 (复用 shop app 的逻辑)
    """
    auth_header = request.headers.get('Authorization')
    if not auth_header or not auth_header.startswith('Bearer '):
        return None
    token = auth_header.split(' ')[1]
    signer = TimestampSigner()
    try:
        # 签名包含 openid
        openid = signer.unsign(token, max_age=86400 * 30) # 30天有效
        return WeChatUser.objects.filter(openid=openid).first()
    except (BadSignature, SignatureExpired):
        return None

class ActivityViewSet(viewsets.ReadOnlyModelViewSet):
    """
    社区活动接口
    """
    queryset = Activity.objects.filter(is_active=True).order_by('-created_at')
    serializer_class = ActivitySerializer

    @extend_schema(summary="报名活动")
    @action(detail=True, methods=['post'])
    def signup(self, request, pk=None):
        user = get_current_wechat_user(request)
        if not user:
            return Response({'error': '请先登录'}, status=401)
        
        activity = self.get_object()
        
        # Check if already signed up
        if ActivitySignup.objects.filter(activity=activity, user=user).exists():
            return Response({'error': '您已报名该活动'}, status=400)
        
        if activity.signups.count() >= activity.max_participants:
             return Response({'error': '活动名额已满'}, status=400)
            
        signup = ActivitySignup.objects.create(activity=activity, user=user)
        serializer = ActivitySignupSerializer(signup)
        return Response(serializer.data, status=201)

    @extend_schema(summary="我的报名记录")
    @action(detail=False, methods=['get'])
    def my_signups(self, request):
        user = get_current_wechat_user(request)
        if not user:
            return Response({'error': '请先登录'}, status=401)
        signups = ActivitySignup.objects.filter(user=user).order_by('-signup_time')
        serializer = ActivitySignupSerializer(signups, many=True)
        return Response(serializer.data)

class TopicViewSet(viewsets.ModelViewSet):
    """
    技术论坛帖子接口
    """
    queryset = Topic.objects.all()
    serializer_class = TopicSerializer

    def perform_create(self, serializer):
        user = get_current_wechat_user(self.request)
        # Auth check is done in create or permission, but here we need user for save
        if user:
            serializer.save(author=user)
    
    def create(self, request, *args, **kwargs):
        user = get_current_wechat_user(request)
        if not user:
            return Response({'error': '请先登录'}, status=401)
        return super().create(request, *args, **kwargs)

class ReplyViewSet(viewsets.ModelViewSet):
    """
    帖子回复接口
    """
    queryset = Reply.objects.all()
    serializer_class = ReplySerializer

    def perform_create(self, serializer):
        user = get_current_wechat_user(self.request)
        if user:
            serializer.save(author=user)

    def create(self, request, *args, **kwargs):
        user = get_current_wechat_user(request)
        if not user:
            return Response({'error': '请先登录'}, status=401)
        return super().create(request, *args, **kwargs)

class TopicMediaViewSet(viewsets.GenericViewSet, mixins.CreateModelMixin):
    """
    论坛多媒体资源上传接口
    """
    queryset = TopicMedia.objects.all()
    serializer_class = TopicMediaSerializer
    parser_classes = [parsers.MultiPartParser, parsers.FormParser]

    @extend_schema(summary="上传媒体文件 (返回URL用于Markdown)")
    def create(self, request, *args, **kwargs):
        user = get_current_wechat_user(request)
        if not user:
            return Response({'error': '请先登录'}, status=401)
            
        # 允许上传时不关联 Topic (发帖前上传)，或后续关联
        # 主要是返回 url
        return super().create(request, *args, **kwargs)