from decimal import Decimal from django.db import transaction from rest_framework import serializers from shop_management.models.data.account_transaction import ( AccountTransaction, AccountTransactionType, ) from shop_management.models.data.account_transfer import AccountTransfer from shop_management.serializers.data.base import DataRootSerializer from account.permissions import assert_shop_access class AccountTransferSerializer(DataRootSerializer): from_account_name = serializers.ReadOnlyField(source="from_account.name") to_account_name = serializers.ReadOnlyField(source="to_account.name") shop = serializers.ReadOnlyField(source="from_account.shop_id") shop_name = serializers.ReadOnlyField(source="from_account.shop.name") from_currency_title = serializers.ReadOnlyField(source="from_currency.title") to_currency_title = serializers.ReadOnlyField(source="to_currency.title") class Meta: model = AccountTransfer fields = [ "id", "from_account", "from_account_name", "to_account", "to_account_name", "shop", "shop_name", "from_currency", "from_currency_title", "to_currency", "to_currency_title", "amount", "exchange_rate", "converted_amount", "service_charge", "service_charge_account", "transfer_number", "uses_controlled_engine", "status", "posted_at", "posted_by", "voided_at", "voided_by", "void_reason", "reference", "note", "transfer_date", "created_at", "updated_at", ] read_only_fields = [ "from_currency", "to_currency", "converted_amount", "created_at", "updated_at", "transfer_number", "status", "posted_at", "posted_by", "voided_at", "voided_by", "void_reason", ] extra_kwargs = {"exchange_rate": {"required": False}} def validate(self, attrs): from_account = attrs.get("from_account") or getattr( self.instance, "from_account", None ) to_account = attrs.get("to_account") or getattr(self.instance, "to_account", None) amount = attrs.get("amount") or getattr(self.instance, "amount", None) if not from_account: raise serializers.ValidationError({"from_account": "From account is required."}) if not to_account: raise serializers.ValidationError({"to_account": "To account is required."}) if from_account.id == to_account.id: raise serializers.ValidationError( {"to_account": "From account and to account cannot be the same."} ) if from_account.shop_id != to_account.shop_id: raise serializers.ValidationError( {"to_account": "Both accounts must belong to the same shop."} ) request = self.context.get("request") if request: assert_shop_access(request.user, from_account.shop, request) if not amount or amount <= 0: raise serializers.ValidationError({"amount": "Amount must be greater than 0."}) resolved_rate = AccountTransaction.resolve_exchange_rate( from_account.shop, from_account.currency_id, to_account.currency_id, attrs.get("transfer_date") or getattr(self.instance, "transfer_date", None), ) provided_rate = attrs.get("exchange_rate") if provided_rate is not None: if provided_rate <= 0: raise serializers.ValidationError( {"exchange_rate": "Exchange rate must be greater than 0."} ) final_rate = Decimal(provided_rate) elif resolved_rate is None: raise serializers.ValidationError( { "to_account": ( "No exchange rate found between source and destination " "account currencies for this shop." ) } ) else: final_rate = Decimal(resolved_rate) attrs["from_currency"] = from_account.currency attrs["to_currency"] = to_account.currency attrs["exchange_rate"] = final_rate attrs["converted_amount"] = AccountTransaction.compute_converted_amount( Decimal(amount), final_rate ) return attrs def _txn_description(self, transfer, direction): prefix = "Transfer out" if direction == "out" else "Transfer in" target = ( f"to {transfer.to_account.name}" if direction == "out" else f"from {transfer.from_account.name}" ) reference = f" | Ref: {transfer.reference}" if transfer.reference else "" note = f" | Note: {transfer.note}" if transfer.note else "" return f"{prefix} {target}{reference}{note}" def _delete_account_transactions(self, transfer): AccountTransaction.objects.filter( account=transfer.from_account, transaction_type=AccountTransactionType.DEBIT, amount=transfer.amount, transaction_date=transfer.transfer_date, description=self._txn_description(transfer, "out"), ).delete() AccountTransaction.objects.filter( account=transfer.to_account, transaction_type=AccountTransactionType.CREDIT, amount=transfer.amount, transaction_date=transfer.transfer_date, description=self._txn_description(transfer, "in"), ).delete() def create(self, validated_data): with transaction.atomic(): if validated_data.get("uses_controlled_engine"): validated_data["status"] = AccountTransfer.Status.DRAFT return super().create(validated_data) transfer = super().create(validated_data) # Double-entry posting: # 1) Debit source account in source currency. AccountTransaction.objects.create( account=transfer.from_account, account_currency=transfer.from_currency, transaction_currency=transfer.from_currency, transaction_type=AccountTransactionType.DEBIT, amount=transfer.amount, exchange_rate=Decimal("1"), converted_amount=transfer.amount, description=self._txn_description(transfer, "out"), transaction_date=transfer.transfer_date, ) # 2) Credit destination account using source currency + exchange rate. AccountTransaction.objects.create( account=transfer.to_account, account_currency=transfer.to_currency, transaction_currency=transfer.from_currency, transaction_type=AccountTransactionType.CREDIT, amount=transfer.amount, exchange_rate=transfer.exchange_rate, converted_amount=transfer.converted_amount, description=self._txn_description(transfer, "in"), transaction_date=transfer.transfer_date, ) return transfer def update(self, instance, validated_data): with transaction.atomic(): if instance.uses_controlled_engine: if instance.status != AccountTransfer.Status.DRAFT: raise serializers.ValidationError("Only draft controlled transfers can be edited.") return super().update(instance, validated_data) self._delete_account_transactions(instance) transfer = super().update(instance, validated_data) AccountTransaction.objects.create( account=transfer.from_account, account_currency=transfer.from_currency, transaction_currency=transfer.from_currency, transaction_type=AccountTransactionType.DEBIT, amount=transfer.amount, exchange_rate=Decimal("1"), converted_amount=transfer.amount, description=self._txn_description(transfer, "out"), transaction_date=transfer.transfer_date, ) AccountTransaction.objects.create( account=transfer.to_account, account_currency=transfer.to_currency, transaction_currency=transfer.from_currency, transaction_type=AccountTransactionType.CREDIT, amount=transfer.amount, exchange_rate=transfer.exchange_rate, converted_amount=transfer.converted_amount, description=self._txn_description(transfer, "in"), transaction_date=transfer.transfer_date, ) return transfer