Django_rest_api/backend/ecommerce/models.py

from django.db import models
from django.contrib.auth.models import User
from utils.model_abstracts import Model
from django_extensions.db.models import (
    TimeStampedModel,
    ActivatorModel,
    TitleSlugDescriptionModel
)


class Item(TimeStampedModel, ActivatorModel, TitleSlugDescriptionModel, Model):
    """
    ecommerce.Item
    Almacena una entrada de item para la tienda
    """
    class Meta:
        verbose_name = 'Item'
        verbose_name_plural = 'Items'
        ordering = ["id"]

    def __str__(self):
        return self.title

    stock = models.IntegerField(default=1)
    price = models.IntegerField(default=0)

    def amount(self):
        """
        Converte el precio de centavos a libras
        """
        amount = float(self.price / 100)
        return amount

    def manage_stock(self, qty):
        """
        Reduce stock según `qty`
        """
        new_stock = self.stock - int(qty)
        self.stock = new_stock
        self.save()

    def check_stock(self, qty):
        """
        Comprueba si la cantidad en order excede el stock
        """
        if int(qty) > self.stock:
            return False
        return True

    def place_order(self, user, qty):
        """
        Realiza un order (pedido)
        """
        if self.check_stock(qty):
            order = Order.objects.create(
                item = self,
                quantity = qty,
                user= user)
            self.manage_stock(qty)
            return order
        else:
            return None


class Order(TimeStampedModel, ActivatorModel, Model):
    """
    ecommerce.Order
    Almacena una entrada de order, relacionada con :model:`ecommerce.Item` y
    :model:`auth.User`.
    """
    class Meta:
        verbose_name = 'Order'
        verbose_name_plural = 'Orders'
        ordering = ["id"]

    user = models.ForeignKey( User, on_delete=models.CASCADE,
                              null=True, blank=True )
    item = models.ForeignKey( Item,
                              null=True,
                              blank=True,
                              on_delete=models.CASCADE )
    quantity = models.IntegerField(default=0)

    def __str__(self):
        return f'{self.user.username} - {self.item.title}'