feat: added product variants

shop/models.py

@@ -4,6 +4,7 @@ from uuid import uuid4
 
 from django.conf import settings
 from django.contrib.auth import get_user_model
+from django.core.exceptions import ValidationError
 from django.core.files.base import ContentFile
 from django.db import models
 from django.utils import timezone
@@ -91,17 +92,100 @@ class Product(TimestampedModel):
     def price(self):
         return self.prices.filter(current=True).first()
 
+    @property
+    def has_variants(self):
+        return self.variants.exists()
+
+    @property
+    def min_variant_price(self):
+        return ProductPrice.objects.filter(variant__product=self, current=True).order_by('price').first()
+
     class Meta:
         verbose_name = _('producto')
         verbose_name_plural = _('productos')
         ordering = ('id',)
 
 
+class ProductAttribute(models.Model):
+    name = models.CharField(max_length=32, unique=True, verbose_name=_('nombre'))
+
+    def __str__(self):
+        return self.name
+
+    class Meta:
+        verbose_name = _('atributo de producto')
+        verbose_name_plural = _('atributos de producto')
+        ordering = ('name',)
+
+
+class ProductAttributeValue(models.Model):
+    attribute = models.ForeignKey(
+        'shop.ProductAttribute', on_delete=models.CASCADE, related_name='values', verbose_name=_('atributo')
+    )
+    value = models.CharField(max_length=32, verbose_name=_('valor'))
+
+    def __str__(self):
+        return f'{self.attribute.name}: {self.value}'
+
+    class Meta:
+        verbose_name = _('valor de atributo')
+        verbose_name_plural = _('valores de atributo')
+        unique_together = ('attribute', 'value')
+        ordering = ('attribute__name', 'value')
+
+
+class ProductVariant(TimestampedModel):
+    product = models.ForeignKey(
+        'shop.Product', on_delete=models.CASCADE, related_name='variants', verbose_name=_('producto')
+    )
+    sku = models.CharField(max_length=64, blank=False, null=False, unique=True, verbose_name=_('código de referencia'))
+    stock = models.DecimalField(max_digits=13, decimal_places=4, default=Decimal('0'), verbose_name=_('stock'))
+    attribute_values = models.ManyToManyField(
+        'shop.ProductAttributeValue', related_name='variants', blank=True, verbose_name=_('valores de atributo')
+    )
+
+    def __str__(self):
+        attrs = ', '.join(str(value) for value in self.attribute_values.all())
+        return f'{self.product.name} ({attrs})' if attrs else self.product.name
+
+    @property
+    def price(self):
+        return self.prices.filter(current=True).first()
+
+    def clean(self):
+        if not self.pk:
+            return
+
+        combination = set(self.attribute_values.values_list('pk', flat=True))
+
+        for other in ProductVariant.objects.filter(product=self.product).exclude(pk=self.pk):
+            if set(other.attribute_values.values_list('pk', flat=True)) == combination:
+                raise ValidationError(_('Ya existe una variante de este producto con la misma combinación de atributos.'))
+
+    class Meta:
+        verbose_name = _('variante de producto')
+        verbose_name_plural = _('variantes de producto')
+        ordering = ('product', 'sku')
+
+
 class ProductPrice(TimestampedModel):
     price = models.DecimalField(max_digits=11, decimal_places=2, verbose_name=_('precio'))
     date = models.DateTimeField(default=timezone.now, verbose_name=_('fecha'))
     product = models.ForeignKey(
-        'shop.Product', on_delete=models.CASCADE, verbose_name=_('producto'), related_name='prices'
+        'shop.Product',
+        on_delete=models.CASCADE,
+        verbose_name=_('producto'),
+        related_name='prices',
+        blank=True,
+        null=True,
+    )
+    variant = models.ForeignKey(
+        'shop.ProductVariant',
+        on_delete=models.CASCADE,
+        verbose_name=_('variante'),
+        related_name='prices',
+        blank=True,
+        null=True,
     )
     tax = models.ForeignKey('shop.Tax', on_delete=models.PROTECT, verbose_name=_('impuesto aplicable'))
     price_with_tax = models.DecimalField(
@@ -116,6 +200,10 @@ class ProductPrice(TimestampedModel):
     def __str__(self):
         return f'{self.price} - {self.tax.code}'
 
+    def clean(self):
+        if bool(self.product_id) == bool(self.variant_id):
+            raise ValidationError(_('El precio debe pertenecer a un producto o a una variante, pero no a ambos.'))
+
     def save(self, *args, **kwargs):
         tax_value = self.price * Decimal(self.tax.value / 100)
         self.price_with_tax = round(self.price + tax_value, 2)
@@ -275,6 +363,14 @@ class OrderLine(TimestampedModel):
     product = models.ForeignKey(
         'shop.Product', on_delete=models.CASCADE, null=False, blank=False, verbose_name=_('producto')
     )
+    variant = models.ForeignKey(
+        'shop.ProductVariant',
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name='order_lines',
+        verbose_name=_('variante'),
+    )
     quantity = models.DecimalField(
         max_digits=13, decimal_places=4, default=Decimal('1'), null=False, blank=False, verbose_name=_('cantidad')
     )
@@ -336,7 +432,7 @@ class Order(TimestampedModel):
         STATUS_REQUESTED_RETURN = 'RQT', _('devolución solicitada')
         STATUS_RETURNED = 'RTN', _('devuelto')
 
-    uuid = models.UUIDField(default=uuid4, verbose_name=_('UUID'), db_index=True)
+    uuid = models.UUIDField(default=uuid4, verbose_name=_('UUID'), unique=True)
     code = models.CharField(default=create_order_code, max_length=20, unique=True)
 
     status = models.CharField(max_length=3, default=Statuses.STATUS_PENDING, verbose_name=_('estado'))
@@ -418,8 +514,20 @@ class Cart(models.Model):
 class CartItem(models.Model):
     cart = models.ForeignKey('shop.Cart', on_delete=models.CASCADE, related_name='items', verbose_name=_('carrito'))
     product = models.ForeignKey('shop.Product', on_delete=models.CASCADE, verbose_name=_('producto'))
+    variant = models.ForeignKey(
+        'shop.ProductVariant',
+        on_delete=models.CASCADE,
+        null=True,
+        blank=True,
+        related_name='cart_items',
+        verbose_name=_('variante'),
+    )
     quantity = models.PositiveIntegerField(default=1, verbose_name=_('cantidad'))
 
+    @property
+    def price(self):
+        return self.variant.price if self.variant else self.product.price
+
     class Meta:
         verbose_name = _('línea de carrito')
         verbose_name_plural = _('líneas de carrito')