from collections import defaultdict from datetime import date, timedelta from decimal import Decimal from django.db.models import Sum from rest_framework.exceptions import ValidationError from rest_framework.permissions import IsAuthenticated from rest_framework.response import Response from rest_framework.views import APIView from account.permissions import HasTabPermission, get_user_shop_filter from shop_management.models.data.purchase import Purchase from shop_management.models.data.purchase_return import PurchaseReturn from shop_management.models.data.supplier_payment import SupplierPayment from shop_management.models.data.shop import Shop def money(value): return str(Decimal(value or 0).quantize(Decimal("0.01"))) def purchase_total(purchase): subtotal = sum( (Decimal(item.quantity or 0) * Decimal(item.buy_price or 0) for item in purchase.purchase_items.all()), Decimal("0"), ) return max(subtotal - Decimal(purchase.amount or 0), Decimal("0")) class PurchaseAnalysisReportView(APIView): """Posted purchase facts only; legacy drafts and editable balance fields are excluded.""" permission_classes = [IsAuthenticated, HasTabPermission] required_tab = "reports" def get(self, request): try: end = date.fromisoformat(request.query_params.get("end_date") or str(date.today())) start = date.fromisoformat(request.query_params.get("start_date") or str(end - timedelta(days=29))) except ValueError: raise ValidationError({"date": "Use YYYY-MM-DD format."}) if start > end: raise ValidationError({"end_date": "End date cannot be before start date."}) try: shop = Shop.objects.get(get_user_shop_filter(request.user), pk=request.query_params.get("shop")) except (Shop.DoesNotExist, ValueError, TypeError): raise ValidationError({"shop": "Branch was not found or is not accessible."}) purchases = list(Purchase.objects.filter( shop=shop, uses_inventory_engine=True, document_status=Purchase.DocumentStatus.POSTED, purchase_date__range=(start, end), is_deleted=False, ).select_related("supplier", "currency", "warehouse").prefetch_related("purchase_items__product")) purchase_ids = [row.id for row in purchases] period_returns = list(PurchaseReturn.objects.filter( shop=shop, uses_inventory_engine=True, document_status=PurchaseReturn.DocumentStatus.POSTED, return_date__date__range=(start, end), ).select_related("purchase", "purchase__currency", "purchase__supplier").prefetch_related("return_items__purchase_item__product")) returns_by_purchase = defaultdict(Decimal) all_returns = PurchaseReturn.objects.filter( purchase_id__in=purchase_ids, document_status=PurchaseReturn.DocumentStatus.POSTED, return_date__date__lte=end, ).prefetch_related("return_items") for returned in all_returns: returns_by_purchase[returned.purchase_id] += Decimal(returned.total_refund_amount or 0) by_supplier = defaultdict(lambda: {"name": "", "count": 0, "gross": Decimal("0"), "returns": Decimal("0")}) by_product = defaultdict(lambda: {"name": "", "quantity": Decimal("0"), "cost": Decimal("0")}) daily = defaultdict(Decimal) invoices = [] gross_base = Decimal("0") outstanding_base = Decimal("0") paid_base = Decimal("0") for purchase in purchases: rate = Decimal(purchase.exchange_rate_used or 1) total = purchase_total(purchase) returned = returns_by_purchase[purchase.id] allocated = purchase.supplier_payment_allocations.filter( payment__status=SupplierPayment.Status.POSTED, payment__payment_date__lte=end, ).aggregate(total=Sum("allocated_amount"))["total"] or Decimal("0") outstanding = max(total - returned - allocated, Decimal("0")) gross_base += total * rate paid_base += allocated * rate outstanding_base += outstanding * rate daily[purchase.purchase_date] += total * rate supplier_key = purchase.supplier_id or 0 supplier = by_supplier[supplier_key] supplier["name"] = purchase.supplier.name if purchase.supplier else "No supplier" supplier["count"] += 1; supplier["gross"] += total * rate; supplier["returns"] += returned * rate ratio = total / sum((Decimal(item.quantity or 0) * Decimal(item.buy_price or 0) for item in purchase.purchase_items.all()), Decimal("0")) if purchase.purchase_items.all() else Decimal("0") for item in purchase.purchase_items.all(): if not item.product: continue product = by_product[item.product_id]; product["name"] = item.product.name product["quantity"] += Decimal(item.quantity or 0) product["cost"] += Decimal(item.quantity or 0) * Decimal(item.buy_price or 0) * ratio * rate invoices.append({ "date": purchase.purchase_date, "number": purchase.purchase_number, "supplier": supplier["name"], "warehouse": purchase.warehouse.name if purchase.warehouse else "", "currency": purchase.currency.title if purchase.currency else "", "total": money(total), "returns": money(returned), "paid": money(allocated), "outstanding": money(outstanding), }) return_base = sum( (Decimal(row.total_refund_amount or 0) * Decimal(row.purchase.exchange_rate_used or 1) for row in period_returns), Decimal("0"), ) return Response({ "shop": shop.name, "start_date": start, "end_date": end, "summary": {"gross_purchases": money(gross_base), "returns": money(return_base), "net_purchases": money(gross_base - return_base), "paid": money(paid_base), "outstanding": money(outstanding_base), "invoice_count": len(purchases)}, "daily": [{"date": day, "purchases": money(value)} for day, value in sorted(daily.items())], "suppliers": [{"supplier_id": key, "supplier": row["name"], "invoice_count": row["count"], "gross_purchases": money(row["gross"]), "returns": money(row["returns"]), "net_purchases": money(row["gross"] - row["returns"])} for key, row in sorted(by_supplier.items(), key=lambda item: item[1]["gross"], reverse=True)], "products": [{"product_id": key, "product": row["name"], "quantity_purchased": money(row["quantity"]), "purchase_cost": money(row["cost"])} for key, row in sorted(by_product.items(), key=lambda item: item[1]["cost"], reverse=True)], "invoices": invoices, })