feat(reaction): 后台表情统计接口

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

reaction/views/admin.py

@@ -0,0 +1,39 @@
+from django.db.models import Count, F, FloatField, Q
+from django.db.models.functions import Cast
+
+from account.decorators import super_admin_required
+from reaction.models import Reaction, ReactionType
+from utils.api import APIView
+
+MIN_USERS_FOR_RATIO = 3
+DEFAULT_ORDERING = "-users"
+
+
+class ReactionStatsAPI(APIView):
+    @super_admin_required
+    def get(self, request):
+        queryset = (
+            Reaction.objects.values(pid=F("problem___id"), title=F("problem__title"))
+            .annotate(users=Count("user", distinct=True))
+            .annotate(**{t.value: Count("id", filter=Q(type=t.value)) for t in ReactionType})
+            .annotate(**{f"{t.value}_ratio": Cast(t.value, FloatField()) / Cast("users", FloatField()) for t in ReactionType})
+        )
+
+        problem_id = request.GET.get("problem")
+        if problem_id:
+            queryset = queryset.filter(problem___id__iexact=problem_id, problem__contest_id__isnull=True)
+
+        ordering = request.GET.get("ordering") or DEFAULT_ORDERING
+        prefix = "-" if ordering.startswith("-") else ""
+        field = ordering.lstrip("-")
+        if field == "users":
+            order_by = f"{prefix}users"
+        elif field in ReactionType.values:
+            # 按占比排序时过滤低样本，避免 1 人点 1 个就冲到 100%
+            queryset = queryset.filter(users__gte=MIN_USERS_FOR_RATIO)
+            order_by = f"{prefix}{field}_ratio"
+        else:
+            order_by = DEFAULT_ORDERING
+
+        queryset = queryset.order_by(order_by)
+        return self.success(self.paginate_data(request, queryset))