from datetime import datetime
from django.contrib.auth.models import User
from django.db import models


class BaseModel(models.Model):
    class Meta:
        abstract = True

    class ReadonlyMeta:
        readonly = []


class SaleOrder(BaseModel):
    class ReadonlyMeta:
        readonly = ["sold_to", "sold_at", "total"]

    name = models.CharField(max_length=200, unique=True)
    sold_to = models.ForeignKey(User, on_delete=models.DO_NOTHING, default=None, null=True)
    total = models.FloatField(max_length=200, default=0.0)
    sold_at = models.DateTimeField(max_length=200, null=True, default=None)

    @property
    def amount_total(self) -> float:
        return sum(
            map(
                lambda x: x.product.unit_price * x.quantity,
                self.saleorderline_set.all(),
            )
        )

    def sell(self, user: User):
        if not self.sold_at:
            self.sold_at = datetime.now()
            self.sold_to = user
            self.total = self.amount_total
            self.save()
        return self


class Product(models.Model):
    name = models.CharField(max_length=200)
    unit_price = models.IntegerField(default=0)


class SaleOrderLine(models.Model):
    name = models.CharField(max_length=200)
    product = models.ForeignKey(Product, on_delete=models.DO_NOTHING, null=True)
    order = models.ForeignKey(SaleOrder, on_delete=models.CASCADE, null=True)
    quantity = models.IntegerField(default=1)