from django.db.models import Count, Q
from rest_framework import viewsets
from rest_framework.decorators import action
from rest_framework.permissions import IsAuthenticated
from rest_framework.request import Request
from rest_framework.response import Response

from .models import JobApplication, JobUpdate
from .serializers import (
    DashboardMetricsSerializer,
    JobApplicationSerializer,
    JobUpdateSerializer,
)


class JobApplicationViewSet(viewsets.ModelViewSet):
    serializer_class = JobApplicationSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        """Filter by user for non-admin users; admins see all."""
        user = self.request.user
        qs = JobApplication.objects.all().prefetch_related("updates")
        if not user.is_admin:
            qs = qs.filter(user=user)
        return qs


class JobUpdateViewSet(viewsets.ModelViewSet):
    serializer_class = JobUpdateSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        """Filter by user via job_application for non-admin users."""
        user = self.request.user
        qs = JobUpdate.objects.select_related("job_application").all()
        if not user.is_admin:
            qs = qs.filter(job_application__user=user)
        return qs

    @action(detail=False, methods=["get"])
    def latest(self, request: Request) -> Response:
        """Return the 3 most recent job updates with job info and metrics."""
        updates = (
            self.get_queryset()
            .select_related("job_application")
            .order_by("-created_at")[:3]
        )
        serializer = self.get_serializer(updates, many=True)
        return Response(serializer.data)

    @action(detail=False, methods=["get"])
    def metrics(self, request: Request) -> Response:
        """Return dashboard metrics: total apps, status breakdown, interview/offer counts."""
        qs = self.get_queryset()

        total = qs.values("job_application").distinct().count()
        # Get status counts from the distinct job applications the user owns
        app_qs = JobApplication.objects.all()
        if not request.user.is_admin:
            app_qs = app_qs.filter(user=request.user)

        total = app_qs.count()
        status_counts = dict(
            app_qs.values("status")
            .annotate(count=Count("id"))
            .values_list("status", "count")
        )
        interview_count = app_qs.filter(
            Q(status="INTERVIEW") | Q(status="OFFER")
        ).count()
        offer_count = app_qs.filter(status="OFFER").count()
        rejection_rate = (
            round(
                status_counts.get("REJECTED", 0) / total * 100, 1
            )
            if total > 0
            else 0.0
        )

        serializer = DashboardMetricsSerializer(
            instance={
                "total_applications": total,
                "status_breakdown": status_counts,
                "interviews_count": interview_count,
                "offers_count": offer_count,
                "rejection_rate": rejection_rate,
            }
        )
        return Response(serializer.data)