from django.db.models import Avg, Count, F, Q
from django.db.models.functions import Greatest
from django_filters.rest_framework import DjangoFilterBackend
from rest_framework import permissions, status, viewsets
from rest_framework.decorators import action
from rest_framework.response import Response

from .filters import (
    ArticleFilter,
    MagazineCategoryFilter,
    MagazineFilter,
    OrganizeCategoryFilter,
    OrganizeFilter,
    ProfessorFilter,
    SubjectFilter,
    WorkGroupFilter,
    WorkGroupTermFilter,
)
from .models import (
    Article,
    ArticleCollect,
    ArticleComment,
    ArticleLike,
    ArticleShare,
    ArticleType,
    Column,
    Magazine,
    MagazineCategory,
    NavPosition,
    Organize,
    OrganizeCategory,
    Professor,
    RuleBand,
    Specialty,
    StarRule,
    Subject,
    WorkGroup,
    WorkGroupMembership,
    WorkGroupTerm,
)
from .serializers import (
    ArticleCommentSerializer,
    ArticleListSerializer,
    ArticleSerializer,
    ArticleTypeSerializer,
    ArticleWriteSerializer,
    ColumnSerializer,
    MagazineCategorySerializer,
    MagazineSerializer,
    OrganizeCategorySerializer,
    OrganizeListSerializer,
    OrganizeSerializer,
    ProfessorSerializer,
    RuleBandSerializer,
    SpecialtySerializer,
    StarRuleSerializer,
    SubjectSerializer,
    WorkGroupMembershipSerializer,
    WorkGroupSerializer,
    WorkGroupTermSerializer,
)


class IsAdminOrReadOnly(permissions.BasePermission):
    def has_permission(self, request, view):
        if request.method in permissions.SAFE_METHODS:
            return True
        return bool(request.user and request.user.is_staff)


class IsMember(permissions.BasePermission):
    """前台会员（非 staff、已绑定 Member 且未禁用）。"""

    def has_permission(self, request, view):
        user = request.user
        if not user or not user.is_authenticated or user.is_staff:
            return False
        member = getattr(user, "member_profile", None)
        return bool(member and not member.is_disabled)


def _request_member(request):
    return getattr(request.user, "member_profile", None)


# 统计未禁用文献数（反向 M2M Count 不会走 SoftDeleteManager）
_ACTIVE_ARTICLE_COUNT = Count(
    "articles",
    filter=Q(articles__is_disabled=False, articles__is_deleted=False),
    distinct=True,
)


class PublicMixin:
    """公众只读：非管理员默认过滤禁用项；管理员可看全量以便后台管理。"""

    def get_queryset(self):
        qs = super().get_queryset()
        user = getattr(self.request, "user", None)
        if user and user.is_staff:
            return qs
        if self.action in (
            "list",
            "retrieve",
            "ranking",
            "nav",
            "home",
            "facets",
            "record_read",
            "record_share",
            "toggle_like",
            "toggle_collect",
            "my_collections",
            "my_engagement",
        ) and hasattr(qs.model, "is_disabled"):
            qs = qs.filter(is_disabled=False)
        return qs


class ColumnViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Column.objects.all()
    serializer_class = ColumnSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["position", "parent", "is_disabled"]
    ordering_fields = ["sort", "id"]
    ordering = ["position", "sort", "id"]

    @action(detail=False, methods=["get"])
    def nav(self, request):
        position = request.query_params.get("position", NavPosition.TOP)
        qs = self.get_queryset().filter(position=position, parent__isnull=True)
        return Response(ColumnSerializer(qs, many=True).data)


class SubjectViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Subject.objects.all()
    serializer_class = SubjectSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = SubjectFilter

    def get_queryset(self):
        qs = super().get_queryset()
        if self.action == "list":
            qs = qs.annotate(article_count=_ACTIVE_ARTICLE_COUNT)
        return qs


class OrganizeCategoryViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = OrganizeCategory.objects.all()
    serializer_class = OrganizeCategorySerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = OrganizeCategoryFilter


class MagazineCategoryViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = MagazineCategory.objects.all()
    serializer_class = MagazineCategorySerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = MagazineCategoryFilter


class OrganizeViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Organize.objects.all()
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = OrganizeFilter

    def get_queryset(self):
        qs = super().get_queryset()
        if self.action in ("list", "ranking"):
            qs = qs.annotate(
                article_count=_ACTIVE_ARTICLE_COUNT,
                avg_score=Avg(
                    "articles__score",
                    filter=Q(articles__is_disabled=False, articles__is_deleted=False),
                ),
            )
        return qs

    def get_serializer_class(self):
        if self.action == "list":
            return OrganizeListSerializer
        return OrganizeSerializer

    @action(detail=False, methods=["get"])
    def ranking(self, request):
        qs = self.get_queryset().order_by("-avg_score", "-article_count")
        page = self.paginate_queryset(qs)
        data = OrganizeListSerializer(page or qs, many=True).data
        if page is not None:
            return self.get_paginated_response(data)
        return Response(data)


class MagazineViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Magazine.objects.prefetch_related("subjects").all()
    serializer_class = MagazineSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = MagazineFilter

    def get_queryset(self):
        qs = super().get_queryset()
        if self.action in ("list", "ranking"):
            qs = qs.annotate(
                article_count=_ACTIVE_ARTICLE_COUNT,
                avg_score=Avg(
                    "articles__score",
                    filter=Q(articles__is_disabled=False, articles__is_deleted=False),
                ),
            )
        return qs

    @action(detail=False, methods=["get"])
    def ranking(self, request):
        qs = self.get_queryset().order_by("-avg_score", "-article_count")
        page = self.paginate_queryset(qs)
        data = MagazineSerializer(page or qs, many=True).data
        if page is not None:
            return self.get_paginated_response(data)
        return Response(data)


class WorkGroupViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = WorkGroup.objects.all()
    serializer_class = WorkGroupSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = WorkGroupFilter


class WorkGroupTermViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = WorkGroupTerm.objects.select_related("workgroup").all()
    serializer_class = WorkGroupTermSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = WorkGroupTermFilter


class WorkGroupMembershipViewSet(viewsets.ModelViewSet):
    queryset = WorkGroupMembership.objects.select_related(
        "professor", "term", "term__workgroup"
    ).all()
    serializer_class = WorkGroupMembershipSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["professor", "term"]


class ProfessorViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Professor.objects.prefetch_related(
        "terms", "memberships__term__workgroup"
    ).all()
    serializer_class = ProfessorSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = ProfessorFilter


class SpecialtyViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Specialty.objects.all()
    serializer_class = SpecialtySerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["type", "is_disabled"]


class StarRuleViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = StarRule.objects.prefetch_related("bands").all()
    serializer_class = StarRuleSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["year", "is_disabled"]


class RuleBandViewSet(viewsets.ModelViewSet):
    queryset = RuleBand.objects.all()
    serializer_class = RuleBandSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["rule", "is_disabled"]


class ArticleTypeViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = ArticleType.objects.all()
    serializer_class = ArticleTypeSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["is_disabled"]


class ArticleViewSet(PublicMixin, viewsets.ModelViewSet):
    queryset = Article.objects.select_related("type").prefetch_related(
        "organizes", "magazines", "subjects"
    ).all()
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_class = ArticleFilter

    def get_serializer_class(self):
        if self.action in ("create", "update", "partial_update"):
            return ArticleWriteSerializer
        if self.action == "list":
            return ArticleListSerializer
        return ArticleSerializer

    def _bump_counter(self, field):
        """前台互动计数 +1；先 get_object 以尊重禁用过滤。"""
        instance = self.get_object()
        Article.objects.filter(pk=instance.pk).update(**{field: F(field) + 1})
        instance.refresh_from_db(fields=[field])
        return Response({"id": instance.id, field: getattr(instance, field)})

    def _toggle_relation(self, model, counter_field, active_key):
        """会员点赞/收藏切换；同步维护计数。"""
        article = self.get_object()
        member = _request_member(self.request)
        if not member:
            return Response(
                {"detail": "请先登录前台会员"},
                status=status.HTTP_401_UNAUTHORIZED,
            )
        existing = model.objects.filter(article=article, member=member).first()
        if existing:
            existing.delete()
            Article.objects.filter(pk=article.pk).update(
                **{counter_field: Greatest(F(counter_field) - 1, 0)}
            )
            active = False
        else:
            model.objects.create(article=article, member=member)
            Article.objects.filter(pk=article.pk).update(
                **{counter_field: F(counter_field) + 1}
            )
            active = True
        article.refresh_from_db(fields=[counter_field])
        return Response(
            {
                "id": article.id,
                active_key: active,
                counter_field: getattr(article, counter_field),
            }
        )

    @action(
        detail=True,
        methods=["post"],
        url_path="record-read",
        permission_classes=[permissions.AllowAny],
    )
    def record_read(self, request, pk=None):
        """前台详情页显式上报阅读，避免 GET 详情误增。"""
        return self._bump_counter("read_num")

    @action(
        detail=True,
        methods=["post"],
        url_path="toggle-like",
        permission_classes=[IsMember],
    )
    def toggle_like(self, request, pk=None):
        """会员点赞 / 取消点赞。"""
        return self._toggle_relation(ArticleLike, "like_num", "liked")

    @action(
        detail=True,
        methods=["post"],
        url_path="toggle-collect",
        permission_classes=[IsMember],
    )
    def toggle_collect(self, request, pk=None):
        """会员收藏 / 取消收藏。"""
        return self._toggle_relation(ArticleCollect, "collect_num", "collected")

    @action(
        detail=True,
        methods=["post"],
        url_path="record-share",
        permission_classes=[permissions.AllowAny],
    )
    def record_share(self, request, pk=None):
        """
        前台分享计数：同一人对同一文献只 +1 一次。
        已登录按会员去重；未登录按 visitor_key 去重。
        """
        from django.db import IntegrityError

        article = self.get_object()
        member = _request_member(request)
        raw_key = (request.data.get("visitor_key") or "").strip()
        # 限制长度，避免异常长串
        visitor_key = raw_key[:64] if raw_key else ""

        if member:
            exists = ArticleShare.objects.filter(
                article=article, member=member
            ).exists()
            if exists:
                return Response(
                    {
                        "id": article.id,
                        "share_num": article.share_num,
                        "counted": False,
                    }
                )
            try:
                ArticleShare.objects.create(article=article, member=member)
            except IntegrityError:
                article.refresh_from_db(fields=["share_num"])
                return Response(
                    {
                        "id": article.id,
                        "share_num": article.share_num,
                        "counted": False,
                    }
                )
        elif visitor_key:
            exists = ArticleShare.objects.filter(
                article=article, visitor_key=visitor_key
            ).exists()
            if exists:
                return Response(
                    {
                        "id": article.id,
                        "share_num": article.share_num,
                        "counted": False,
                    }
                )
            try:
                ArticleShare.objects.create(
                    article=article, visitor_key=visitor_key
                )
            except IntegrityError:
                article.refresh_from_db(fields=["share_num"])
                return Response(
                    {
                        "id": article.id,
                        "share_num": article.share_num,
                        "counted": False,
                    }
                )
        else:
            # 无身份标识时无法去重，仍允许计数（兼容旧客户端）
            Article.objects.filter(pk=article.pk).update(share_num=F("share_num") + 1)
            article.refresh_from_db(fields=["share_num"])
            return Response(
                {"id": article.id, "share_num": article.share_num, "counted": True}
            )

        Article.objects.filter(pk=article.pk).update(share_num=F("share_num") + 1)
        article.refresh_from_db(fields=["share_num"])
        return Response(
            {"id": article.id, "share_num": article.share_num, "counted": True}
        )

    @action(
        detail=False,
        methods=["get"],
        url_path="my-collections",
        permission_classes=[IsMember],
    )
    def my_collections(self, request):
        """当前会员的收藏列表。"""
        member = _request_member(request)
        qs = (
            self.get_queryset()
            .filter(collections__member=member)
            .order_by("-collections__created_at", "-id")
            .distinct()
        )
        page = self.paginate_queryset(qs)
        data = ArticleListSerializer(page or qs, many=True).data
        if page is not None:
            return self.get_paginated_response(data)
        return Response(data)

    @action(
        detail=False,
        methods=["get"],
        url_path="my-engagement",
        permission_classes=[IsMember],
    )
    def my_engagement(self, request):
        """批量查询当前会员对若干文献的点赞/收藏状态。"""
        member = _request_member(request)
        raw = request.query_params.get("ids") or ""
        ids = [x.strip() for x in raw.split(",") if x.strip().isdigit()]
        if not ids:
            return Response({"liked": [], "collected": []})
        liked = list(
            ArticleLike.objects.filter(member=member, article_id__in=ids).values_list(
                "article_id", flat=True
            )
        )
        collected = list(
            ArticleCollect.objects.filter(
                member=member, article_id__in=ids
            ).values_list("article_id", flat=True)
        )
        return Response({"liked": liked, "collected": collected})

    @action(detail=False, methods=["get"])
    def ranking(self, request):
        article_type = request.query_params.get("type")
        year = request.query_params.get("year")
        subject = request.query_params.get("subject")
        qs = self.get_queryset().order_by("-score", "-year")
        if article_type:
            qs = qs.filter(type=article_type)
        if year:
            qs = qs.filter(year=year)
        if subject:
            qs = qs.filter(subjects=subject)
        page = self.paginate_queryset(qs)
        data = ArticleListSerializer(page or qs, many=True).data
        if page is not None:
            return self.get_paginated_response(data)
        return Response(data)

    @action(detail=False, methods=["get"])
    def home(self, request):
        """首页精选：按 rank 展示。"""
        qs = self.get_queryset().filter(rank__isnull=False).order_by("rank")[:20]
        return Response(ArticleListSerializer(qs, many=True).data)

    @action(detail=False, methods=["get"])
    def facets(self, request):
        """筛选面板用：文献总量、按类型计数、实际存在的年份列表。"""
        qs = self.get_queryset()
        by_type = {
            row["type_id"]: row["count"]
            for row in qs.values("type_id").annotate(count=Count("id"))
        }
        type_rows = list(
            ArticleType.objects.filter(is_disabled=False).order_by("sort", "id")
        )
        type_map = {str(t.id): by_type.get(t.id, 0) for t in type_rows}
        years = list(
            qs.exclude(year__isnull=True)
            .values_list("year", flat=True)
            .distinct()
            .order_by("-year")
        )
        return Response(
            {
                "total": qs.count(),
                "type": type_map,
                "types": [
                    {
                        "id": t.id,
                        "name": t.name,
                        "count": by_type.get(t.id, 0),
                    }
                    for t in type_rows
                ],
                "years": years,
            }
        )


class ArticleCommentViewSet(viewsets.ModelViewSet):
    """文献用户评价（后台审核）。"""

    queryset = ArticleComment.objects.select_related("article", "member").all()
    serializer_class = ArticleCommentSerializer
    permission_classes = [IsAdminOrReadOnly]
    filter_backends = [DjangoFilterBackend]
    filterset_fields = ["review_status", "article", "member"]

    def get_queryset(self):
        qs = super().get_queryset()
        user = getattr(self.request, "user", None)
        # 公众只看已通过；管理员看全量
        if not (user and user.is_staff):
            qs = qs.filter(review_status=3)
        start = self.request.query_params.get("start_date")
        end = self.request.query_params.get("end_date")
        if start:
            qs = qs.filter(created_at__date__gte=start)
        if end:
            qs = qs.filter(created_at__date__lte=end)
        return qs