from django.db.models import Model, CharField, BooleanField, DecimalField, ForeignKey, CASCADE

from django_countries.fields import CountryField

class Currency(Model):
    name = CharField(max_length=255, unique=True)
    code = CharField(max_length=16, unique=True)
    symbol = CharField(max_length=8)
    base = BooleanField(default=False)
    rate = DecimalField(default=1, max_digits=30, decimal_places=10)

    def set_base(self):
        type(self).get_base().update(base=False)
        self.update(base=True)

    @classmethod
    def get_base(cls):
        return cls.objects.get(base=True)

class TaxPolicy(Model):
    name = CharField(max_length=255, blank=True)
    default_rate = DecimalField(default=0, max_digits=10, decimal_places=5)

    def get_applicable_rate(self, country, reverse_charge=False):
        rule = self.taxrule_set.get(destination_country=country)
        if reverse_charge:
            return rule.tax_rate if not rule.reverse_charge else 0
        return rule.tax_rate

class TaxRule(Model):
    policy = ForeignKey(TaxPolicy, on_delete=CASCADE)
    destination_country = CountryField()
    tax_rate = DecimalField(max_digits=10, decimal_places=5)
    reverse_charge = BooleanField(default=False)