from django import forms
from django.core.exceptions import ValidationError

from shop.models import ProductVariant


class ProductVariantForm(forms.ModelForm):
    class Meta:
        model = ProductVariant
        fields = ('sku', 'stock', 'attribute_values')
        widgets = {'attribute_values': forms.CheckboxSelectMultiple}

    def __init__(self, *args, product=None, **kwargs):
        super().__init__(*args, **kwargs)
        self.product = product or self.instance.product

    def clean(self):
        cleaned_data = super().clean()
        attribute_values = cleaned_data.get('attribute_values')

        if attribute_values is not None:
            combination = set(attribute_values.values_list('pk', flat=True))
            siblings = ProductVariant.objects.filter(product=self.product).exclude(pk=self.instance.pk)

            for sibling in siblings:
                if set(sibling.attribute_values.values_list('pk', flat=True)) == combination:
                    raise ValidationError(
                        'Ya existe una variante de este producto con la misma combinación de atributos.'
                    )

        return cleaned_data

    def save(self, commit=True):
        self.instance.product = self.product
        return super().save(commit=commit)