from django.db import models


class Item(models.Model):
    VALID_CURRENCIES = (
        ('CAD', 'CAD'),
        ('USD', 'USD'),
    )
    name = models.CharField(max_length=120)
    price = models.DecimalField(max_digits=5, decimal_places=2)
    currency = models.CharField(max_length=3, choices=VALID_CURRENCIES)

    def __str__(self):
        return self.name


class Shop(models.Model):
    name = models.CharField(max_length=120)

    def __str__(self):
        return self.name


class Inventory(models.Model):
    class Meta:
        unique_together = ['shop', 'item']
        ordering = ['shop', 'item__name']
        verbose_name_plural = 'Inventory'

    shop = models.ForeignKey(to=Shop, on_delete=models.CASCADE, related_name='inventory')
    item = models.ForeignKey(to=Item, on_delete=models.CASCADE)
    quantity = models.PositiveIntegerField()