import uuid

from django.db.models import Sum
from django.http import HttpResponse
from django.utils.dateparse import parse_date
from rest_framework import generics, status
from rest_framework.exceptions import NotFound, ValidationError
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

from apps.bizapps.models import (
    Account,
    Customer,
    Invoice,
    LedgerBook,
    LedgerEntry,
    LedgerInstallment,
    Product,
    StockMovement,
    Transaction,
)

from .accounting import (
    ChartOfAccountsService,
    CustomerStatementService,
    LedgerBookService,
    SubsidiaryLedgerService,
)
from .serializers import (
    AccountSerializer,
    AdjustStockSerializer,
    CreateInvoiceSerializer,
    CustomerSerializer,
    InvoiceSerializer,
    LedgerBookSerializer,
    LedgerEntrySerializer,
    LedgerInstallmentSerializer,
    OpenLedgerBookSerializer,
    ProductSerializer,
    StockMovementSerializer,
    TransactionSerializer,
    UpdateInvoiceStatusSerializer,
)
from .services import InsufficientStockError, InvoiceService, LedgerService


class _OwnedMixin:
    """همه‌ی منابع این اپ فقط متعلق به کاربرِ درخواست‌دهنده‌اند."""

    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        return self.model.objects.filter(user=self.request.user)


# ---------------- مشتریان ----------------


class CustomerListCreateView(_OwnedMixin, generics.ListCreateAPIView):
    model = Customer
    serializer_class = CustomerSerializer

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


class CustomerDetailView(_OwnedMixin, generics.RetrieveUpdateDestroyAPIView):
    model = Customer
    serializer_class = CustomerSerializer


class CustomerStatementView(APIView):
    """صورت‌حسابِ کاملِ یک مشتری — فاکتورها + بدهی‌های باز + اقساط، یک‌جا.
    همان اتصالِ «مشتری ↔ فاکتور ↔ حسابداری» به‌شکلِ یک پاسخِ واحد."""

    permission_classes = [IsAuthenticated]

    def get(self, request, pk):
        customer = Customer.objects.filter(user=request.user, pk=pk).first()
        if customer is None:
            raise NotFound("مشتری یافت نشد.")
        return Response(CustomerStatementService.build(request.user, customer))


# ---------------- دفتر درآمد و هزینه ----------------


class LedgerEntryListCreateView(_OwnedMixin, generics.ListCreateAPIView):
    model = LedgerEntry
    serializer_class = LedgerEntrySerializer

    def get_queryset(self):
        qs = super().get_queryset().prefetch_related("installments").select_related("account")
        # پیش‌فرض فقط فایلِ جاری؟ نه — book=<id> صریح، وگرنه همه؛ تا
        # گزارش‌های چنددوره‌ای هم ممکن بماند.
        book_id = self.request.query_params.get("book")
        if book_id:
            qs = qs.filter(book_id=book_id)
        start = parse_date(self.request.query_params.get("start", "") or "")
        end = parse_date(self.request.query_params.get("end", "") or "")
        if start:
            qs = qs.filter(entry_date__gte=start)
        if end:
            qs = qs.filter(entry_date__lte=end)
        return qs

    def perform_create(self, serializer):
        book = LedgerBookService.ensure_active_book(self.request.user)
        entry = serializer.save(user=self.request.user, book=book)
        LedgerService.sync_entry_account(self.request.user, entry)
        LedgerService.post_entry_transaction(self.request.user, entry)
        if entry.counterparty_phone:
            LedgerService.recompute_customer_balance(self.request.user, entry.counterparty_phone)


class LedgerEntryDetailView(_OwnedMixin, generics.RetrieveUpdateDestroyAPIView):
    model = LedgerEntry
    serializer_class = LedgerEntrySerializer

    def get_queryset(self):
        return super().get_queryset().prefetch_related("installments").select_related("account")

    def perform_update(self, serializer):
        entry = serializer.save()
        LedgerService.sync_entry_account(self.request.user, entry)
        LedgerService.post_entry_transaction(self.request.user, entry)
        if entry.counterparty_phone:
            LedgerService.recompute_customer_balance(self.request.user, entry.counterparty_phone)

    def perform_destroy(self, instance):
        phone = instance.counterparty_phone
        instance.delete()
        if phone:
            LedgerService.recompute_customer_balance(self.request.user, phone)


class LedgerInstallmentListCreateView(generics.ListCreateAPIView):
    serializer_class = LedgerInstallmentSerializer
    permission_classes = [IsAuthenticated]

    def _entry(self) -> LedgerEntry:
        entry = LedgerEntry.objects.filter(
            user=self.request.user, pk=self.kwargs["entry_id"]
        ).prefetch_related("installments").first()
        if entry is None:
            raise NotFound("ردیف دفتر یافت نشد.")
        return entry

    def get_serializer_context(self):
        context = super().get_serializer_context()
        context["ledger_entry"] = self._entry()
        return context

    def get_queryset(self):
        return self._entry().installments.all()

    def perform_create(self, serializer):
        entry = self._entry()
        installment = serializer.save(id=str(uuid.uuid4()), ledger_entry=entry)
        # هر قسط، هم مانده‌ی مشتری را به‌روز می‌کند هم یک سندِ حسابداری
        # دوطرفه می‌سازد — همان اتصالِ دفتر به درختِ حساب‌ها.
        LedgerService.post_installment_transaction(self.request.user, installment)
        if entry.counterparty_phone:
            LedgerService.recompute_customer_balance(self.request.user, entry.counterparty_phone)


class LedgerInstallmentDetailView(generics.DestroyAPIView):
    serializer_class = LedgerInstallmentSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        return LedgerInstallment.objects.filter(ledger_entry__user=self.request.user)

    def perform_destroy(self, instance):
        phone = instance.ledger_entry.counterparty_phone
        instance.delete()
        if phone:
            LedgerService.recompute_customer_balance(self.request.user, phone)


class LedgerExportView(APIView):
    """خروجیِ دفتر — پیش‌فرض اکسلِ چندبرگی (?type=csv برای نسخه‌ی ساده).

    عمداً `type` و نه `format`: پارامترِ `format` را خودِ DRF برای مذاکره‌ی
    محتوا رزرو کرده و `?format=csv` را به‌عنوان درخواستِ رندررِ ثبت‌نشده‌ی
    csv تفسیر و ۴۰۴ می‌دهد."""

    permission_classes = [IsAuthenticated]

    def get(self, request):
        start = parse_date(request.query_params.get("start", "") or "")
        end = parse_date(request.query_params.get("end", "") or "")

        if request.query_params.get("type") == "csv":
            content = LedgerService.export_csv(request.user, start, end)
            response = HttpResponse(content, content_type="text/csv; charset=utf-8-sig")
            response["Content-Disposition"] = 'attachment; filename="ledger.csv"'
            return response

        content = LedgerService.export_xlsx(request.user, start, end)
        response = HttpResponse(
            content,
            content_type="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
        )
        response["Content-Disposition"] = 'attachment; filename="shopship-report.xlsx"'
        return response


# ---------------- درخت حساب‌ها ----------------


class AccountListView(generics.ListCreateAPIView):
    serializer_class = AccountSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        ChartOfAccountsService.ensure_chart(self.request.user)
        qs = Account.objects.filter(user=self.request.user).select_related("parent")
        level = self.request.query_params.get("level")
        if level:
            qs = qs.filter(level=level)
        return qs

    def perform_create(self, serializer):
        serializer.save(id=str(uuid.uuid4()), user=self.request.user, is_system=False)


class AccountDetailView(generics.RetrieveUpdateDestroyAPIView):
    serializer_class = AccountSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        return Account.objects.filter(user=self.request.user)

    def perform_destroy(self, instance):
        # حساب‌های سیستمی پایه‌ی سندهای خودکارند؛ حذفشان گزارش‌ها را می‌شکند.
        if instance.is_system:
            raise ValidationError({"detail": "حساب‌های سیستمی قابل حذف نیستند."})
        instance.delete()


class TrialBalanceView(APIView):
    """ترازِ حساب‌ها — جمعِ بدهکار/بستانکار و مانده‌ی هر حسابِ معین."""

    permission_classes = [IsAuthenticated]

    def get(self, request):
        start = parse_date(request.query_params.get("start", "") or "")
        end = parse_date(request.query_params.get("end", "") or "")
        return Response(ChartOfAccountsService.trial_balance(request.user, start, end))


class TransactionListView(generics.ListAPIView):
    serializer_class = TransactionSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        return Transaction.objects.filter(user=self.request.user).select_related(
            "debit_account_ref", "credit_account_ref"
        )


# ---------------- انبار ----------------


class ProductListCreateView(_OwnedMixin, generics.ListCreateAPIView):
    model = Product
    serializer_class = ProductSerializer

    def perform_create(self, serializer):
        product = serializer.save(user=self.request.user)
        product.recompute_purchase_value()
        product.save(update_fields=["total_purchase_value", "updated_at"])


class ProductDetailView(_OwnedMixin, generics.RetrieveUpdateDestroyAPIView):
    model = Product
    serializer_class = ProductSerializer

    def perform_update(self, serializer):
        product = serializer.save()
        product.recompute_purchase_value()
        product.save(update_fields=["total_purchase_value", "updated_at"])


class ProductAdjustStockView(APIView):
    permission_classes = [IsAuthenticated]

    def post(self, request, pk):
        product = Product.objects.filter(user=request.user, pk=pk).first()
        if product is None:
            raise NotFound("کالا یافت نشد.")
        serializer = AdjustStockSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)

        product.quantity += serializer.validated_data["delta"]
        product.recompute_purchase_value()
        product.save(update_fields=["quantity", "total_purchase_value", "updated_at"])
        StockMovement.objects.create(
            product=product,
            delta=serializer.validated_data["delta"],
            quantity_after=product.quantity,
            note=serializer.validated_data.get("note", ""),
        )
        return Response(ProductSerializer(product).data)


class ProductMovementsView(generics.ListAPIView):
    serializer_class = StockMovementSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        return StockMovement.objects.filter(
            product__user=self.request.user, product_id=self.kwargs["pk"]
        )


class InventorySummaryView(APIView):
    """خلاصه‌ی انبار — ارزشِ کل، تعداد اقلام، و کالاهای روی آستانه‌ی کمبود."""

    permission_classes = [IsAuthenticated]

    def get(self, request):
        products = Product.objects.filter(user=request.user)
        low = [p for p in products if p.is_low_stock]
        return Response(
            {
                "total_products": products.count(),
                "total_value": products.aggregate(v=Sum("total_purchase_value"))["v"] or 0,
                "low_stock_count": len(low),
                "low_stock": ProductSerializer(low, many=True).data,
            }
        )


# ---------------- فاکتور ----------------


class InvoiceListCreateView(_OwnedMixin, generics.ListCreateAPIView):
    model = Invoice
    serializer_class = InvoiceSerializer

    def get_queryset(self):
        return super().get_queryset().prefetch_related("items")

    def create(self, request, *args, **kwargs):
        serializer = CreateInvoiceSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        data = dict(serializer.validated_data)
        send_sms = data.pop("send_sms", False)
        try:
            invoice = InvoiceService.create_invoice(request.user, data, send_sms=send_sms)
        except InsufficientStockError as exc:
            raise ValidationError({"detail": str(exc)})
        return Response(InvoiceSerializer(invoice).data, status=status.HTTP_201_CREATED)


class InvoiceDetailView(_OwnedMixin, generics.RetrieveAPIView):
    model = Invoice
    serializer_class = InvoiceSerializer

    def get_queryset(self):
        return super().get_queryset().prefetch_related("items")


class InvoiceStatusView(APIView):
    permission_classes = [IsAuthenticated]

    def post(self, request, pk):
        serializer = UpdateInvoiceStatusSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        try:
            invoice = InvoiceService.update_status(request.user, pk, **serializer.validated_data)
        except Invoice.DoesNotExist:
            raise NotFound("فاکتور یافت نشد.")
        return Response(InvoiceSerializer(invoice).data)


class InvoiceCancelView(APIView):
    permission_classes = [IsAuthenticated]

    def post(self, request, pk):
        try:
            invoice = InvoiceService.cancel_invoice(request.user, pk)
        except Invoice.DoesNotExist:
            raise NotFound("فاکتور یافت نشد.")
        except ValueError as exc:
            raise ValidationError({"detail": str(exc)})
        return Response(InvoiceSerializer(invoice).data)


class BusinessDashboardView(APIView):
    """داشبوردِ یکپارچه — همان «اتصالِ بخش‌ها» به‌شکلِ یک پاسخ: فروش، بدهی،
    انبار و فاکتورها کنار هم، به‌جای چهار درخواستِ جدا از چهار صفحه."""

    permission_classes = [IsAuthenticated]

    def get(self, request):
        user = request.user
        entries = LedgerEntry.objects.filter(user=user).prefetch_related("installments")
        products = Product.objects.filter(user=user)
        invoices = Invoice.objects.filter(user=user)

        income = sum(e.amount for e in entries if e.entry_type == LedgerEntry.EntryType.INCOME)
        expense = sum(e.amount for e in entries if e.entry_type == LedgerEntry.EntryType.EXPENSE)
        receivable = sum(
            e.remaining_amount for e in entries if e.category == LedgerEntry.Category.SALE_CREDIT
        )
        payable = sum(
            e.remaining_amount for e in entries if e.category == LedgerEntry.Category.PURCHASE_CREDIT
        )

        return Response(
            {
                "total_income": income,
                "total_expense": expense,
                "net_profit": income - expense,
                "open_receivable": receivable,
                "open_payable": payable,
                "inventory_value": products.aggregate(v=Sum("total_purchase_value"))["v"] or 0,
                "low_stock_count": sum(1 for p in products if p.is_low_stock),
                "invoice_count": invoices.count(),
                "unpaid_invoice_count": invoices.filter(
                    payment_status=Invoice.PaymentStatus.UNPAID
                ).exclude(order_status=Invoice.OrderStatus.CANCELLED).count(),
                "customer_count": Customer.objects.filter(user=user).count(),
                "debtor_count": Customer.objects.filter(user=user, outstanding_balance__gt=0).count(),
            }
        )


# ---------------- فایل‌های دفتر و دفتر معین ----------------


class LedgerBookListView(generics.ListAPIView):
    """فهرست فایل‌های دفتر — همیشه حداقل یک فایلِ جاری وجود دارد."""

    serializer_class = LedgerBookSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        LedgerBookService.ensure_active_book(self.request.user)
        return LedgerBook.objects.filter(user=self.request.user)


class OpenLedgerBookView(APIView):
    """باز کردن فایل تازه — فایلِ جاری بسته می‌شود و (در صورت انتخاب) مانده
    به فایل جدید منتقل می‌گردد."""

    permission_classes = [IsAuthenticated]

    def post(self, request):
        serializer = OpenLedgerBookSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        book = LedgerBookService.open_new_book(
            request.user,
            name=serializer.validated_data["name"],
            start_date=serializer.validated_data["start_date"],
            end_date=serializer.validated_data.get("end_date"),
            carry_balance=serializer.validated_data.get("carry_balance", True),
        )
        return Response(LedgerBookSerializer(book).data, status=status.HTTP_201_CREATED)


class LedgerBookSummaryView(APIView):
    permission_classes = [IsAuthenticated]

    def get(self, request, pk):
        book = LedgerBook.objects.filter(user=request.user, pk=pk).first()
        if book is None:
            raise NotFound("فایل دفتر یافت نشد.")
        return Response(
            {"book": LedgerBookSerializer(book).data, **LedgerBookService.summary(book)}
        )


class LedgerBookDetailView(generics.RetrieveUpdateDestroyAPIView):
    """ویرایش/حذفِ یک فایل دفتر. فایلِ بایگانی‌شده فقط-خواندنی است — نه
    ویرایش و نه حذف. حذف فقط برای فایلِ خالی (بدون هیچ ثبتی) مجاز است تا
    داده‌ی مالی با حذفِ فایل به‌طور آبشاری از بین نرود."""

    serializer_class = LedgerBookSerializer
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        return LedgerBook.objects.filter(user=self.request.user)

    def _guard_editable(self, book: LedgerBook):
        if book.is_closed:
            raise ValidationError("فایلِ بایگانی‌شده فقط-خواندنی است.")

    def perform_update(self, serializer):
        self._guard_editable(serializer.instance)
        serializer.save()

    def perform_destroy(self, instance):
        self._guard_editable(instance)
        if instance.entries.exists():
            raise ValidationError("فقط فایلِ خالی (بدون هیچ ثبتی) قابل‌حذف است.")
        instance.delete()


class LedgerBookArchiveView(APIView):
    """بایگانی‌کردنِ دستیِ یک فایل دفتر — از این پس فقط-خواندنی می‌شود و در
    انتخابِ فایلِ دفتر برای فاکتورهای تازه نشان داده نمی‌شود."""

    permission_classes = [IsAuthenticated]

    def post(self, request, pk):
        book = LedgerBook.objects.filter(user=request.user, pk=pk).first()
        if book is None:
            raise NotFound("فایل دفتر یافت نشد.")
        if book.is_closed:
            raise ValidationError("این فایل قبلا بایگانی شده.")
        book = LedgerBookService.archive_book(book)
        return Response(LedgerBookSerializer(book).data)


class SubsidiaryLedgerView(APIView):
    """دفتر معین یک حساب — گردشِ حساب با مانده‌ی در جریان."""

    permission_classes = [IsAuthenticated]

    def get(self, request, pk):
        account = Account.objects.filter(user=request.user, pk=pk).first()
        if account is None:
            raise NotFound("حساب یافت نشد.")
        start = parse_date(request.query_params.get("start", "") or "")
        end = parse_date(request.query_params.get("end", "") or "")
        return Response(
            SubsidiaryLedgerService.statement(request.user, account, start, end)
        )