from django.db import transaction
from core.serializers import BaseSerializer
from rest_framework import serializers
from .models import Invoice, InvoiceItem, InvoiceTransaction
from .services import InvoiceService  #

class InvoiceItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = InvoiceItem
        fields = ['description', 'quantity', 'unit_price']

class InvoiceSerializer(serializers.ModelSerializer):
    items = InvoiceItemSerializer(many=True) # Nested lista stavki

    class Meta:
        model = Invoice
        fields = ['invoice_number', 'client', 'due_date', 'status', 'items', 'amount']
        read_only_fields = ['invoice_number', 'creator', 'status', 'amount']
        extra_kwargs = {
            'invoice_number': {'required': False, 'allow_null': True},
            'creator': {'required': False, 'allow_null': True}
        }

    def create(self, validated_data):
        """
        Delegiramo stvaranje servisu i vraćamo instancu Invoice.
        """
        items = validated_data.pop('items', [])
        # Servisu šaljemo items u validated_data kao što servis očekuje
        validated_data['items'] = items

        # Pokušavamo dohvatiti korisnika iz contexta (ako postoji)
        request = self.context.get('request')
        user = getattr(request, 'user', None)

        # Pozivamo servis unutar transaction.atomic (servis već radi atomic, ali dodatno osiguranje nije štetno)
        invoice = InvoiceService.create_full_invoice(user=user, **validated_data)
        return invoice

class InvoiceTransactionSerializer(BaseSerializer):
    invoice = serializers.PrimaryKeyRelatedField(queryset=Invoice.objects.all())

    def validate_amount(self, value):
        request = self.context.get('request')
        # Ako request ne postoji (npr. unit test), tretiramo ga kao običnog korisnika (sigurnost prvo)
        user = getattr(request, 'user', None)
        
        # Ako user ne postoji ili nije staff, i iznos je <= 0 -> greška
        if value <= 0 and (not user or not user.is_staff):
            raise serializers.ValidationError("Iznos računa mora biti veći od 0.")
        
        return value
    
    class Meta:
        model = InvoiceTransaction
        fields = ['invoice', 'work_order', 'invoice_number', 'amount', 'payment_date', 'is_active']
        read_only_fields = ['id', 'created_at', 'updated_at']