from django.db import transaction
from django.utils import timezone
from rest_framework import generics, status
from rest_framework.exceptions import NotFound
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

from apps.account.models import User
from apps.billing.models import BazaarPurchase, FeaturePlan, GemPack, GemTransaction
from apps.billing.providers.bazaar import verify_purchase

from .serializers import (
    ActivateFeatureSerializer,
    CreatePurchaseSerializer,
    FeaturePlanSerializer,
    GemPackSerializer,
    WalletSerializer,
)
from .services import FeatureAccessService, GemWalletService


def _wallet_data(user: User) -> dict:
    return {
        "gem_balance": user.gem_balance,
        "is_in_trial": user.is_in_trial,
        "trial_expires_at": user.trial_expires_at,
        "referral_code": user.referral_code,
        "referral_count": User.objects.filter(referred_by=user, referral_bonus_granted=True).count(),
    }


class WalletView(APIView):
    permission_classes = [IsAuthenticated]

    def get(self, request):
        return Response(WalletSerializer(_wallet_data(request.user)).data)


class FeatureListView(generics.ListAPIView):
    serializer_class = FeaturePlanSerializer
    permission_classes = [IsAuthenticated]
    queryset = FeaturePlan.objects.filter(is_purchasable=True).prefetch_related("tiers")


class ActivateFeatureView(APIView):
    permission_classes = [IsAuthenticated]
    throttle_scope = "billing_write"

    def post(self, request, key):
        serializer = ActivateFeatureSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        FeatureAccessService.activate(request.user, key, serializer.validated_data["duration_months"])
        return Response(
            {
                "success": True,
                "feature": FeaturePlanSerializer(
                    FeaturePlan.objects.get(key=key), context={"request": request}
                ).data,
                "wallet": WalletSerializer(_wallet_data(request.user)).data,
            }
        )


class GemPackListView(generics.ListAPIView):
    serializer_class = GemPackSerializer
    permission_classes = [IsAuthenticated]
    queryset = GemPack.objects.filter(is_active=True)


class CreatePurchaseView(APIView):
    """کلاینت بعد از باز کردن لینک خرید کافه‌بازار و برگشتن، اینجا فقط
    می‌گوید «این خرید را شروع کردم»؛ جمی اضافه نمی‌شود تا verify تایید کند."""

    permission_classes = [IsAuthenticated]
    throttle_scope = "billing_write"

    def post(self, request):
        serializer = CreatePurchaseSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        try:
            gem_pack = GemPack.objects.get(id=serializer.validated_data["gem_pack_id"], is_active=True)
        except GemPack.DoesNotExist:
            raise NotFound("بسته‌ی جم یافت نشد.")

        purchase, _created = BazaarPurchase.objects.get_or_create(
            purchase_token=serializer.validated_data["purchase_token"],
            defaults={"user": request.user, "gem_pack": gem_pack},
        )
        return Response({"id": purchase.id, "status": purchase.status}, status=status.HTTP_201_CREATED)


class VerifyPurchaseView(APIView):
    permission_classes = [IsAuthenticated]
    throttle_scope = "billing_write"

    def post(self, request, purchase_id):
        # قفل ردیفِ همین خرید تا پایان تراکنش — بدون این، دو درخواست verify
        # هم‌زمان (دابل‌تپ یا retry شبکه) هر دو می‌توانند از چک status=pending
        # رد شوند و جم را دوبار اضافه کنند. با این قفل، دومی تا کامیت شدن
        # اولی معطل می‌ماند و بعد status=verified را می‌بیند و کاری نمی‌کند.
        with transaction.atomic():
            try:
                purchase = BazaarPurchase.objects.select_for_update().get(id=purchase_id, user=request.user)
            except BazaarPurchase.DoesNotExist:
                raise NotFound("خرید یافت نشد.")

            if purchase.status == BazaarPurchase.Status.VERIFIED:
                return Response(
                    {"status": purchase.status, "wallet": WalletSerializer(_wallet_data(request.user)).data}
                )

            is_valid = verify_purchase(purchase.gem_pack.bazaar_sku, purchase.purchase_token)
            if not is_valid:
                purchase.status = BazaarPurchase.Status.FAILED
                purchase.save(update_fields=["status"])
                return Response(
                    {"status": purchase.status, "detail": "تایید خرید ناموفق بود."},
                    status=status.HTTP_400_BAD_REQUEST,
                )

            GemWalletService.add_gems(
                request.user,
                purchase.gem_pack.gem_amount,
                GemTransaction.Reason.PURCHASE,
                note=f"خرید {purchase.gem_pack.display_name}",
            )
            purchase.status = BazaarPurchase.Status.VERIFIED
            purchase.gems_granted = purchase.gem_pack.gem_amount
            purchase.verified_at = timezone.now()
            purchase.save(update_fields=["status", "gems_granted", "verified_at"])

        return Response({"status": purchase.status, "wallet": WalletSerializer(_wallet_data(request.user)).data})