invoice.py

from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.utils.translation import gettext_lazy as _

from djmoney.models.fields import CurrencyField, MoneyField
from payments import PurchasedItem
from payments.models import BasePayment

from aleksis.core.mixins import ExtensibleModel, PureDjangoModel

from .base import Client
from ..tables import PurchasedItemsTable, TotalsTable


class InvoiceGroup(ExtensibleModel):
    name = models.CharField(verbose_name=_("Invoice group name"), max_length=255)
    client = models.ForeignKey(
        Client, verbose_name=_("Linked client"), related_name="invoice_groups", on_delete=models.SET_NULL, null=True
    )

    template_name = models.CharField(verbose_name=_("Template to render invoices with as PDF"), blank=True, max_length=255)

    def __str__(self) -> str:
        return self.name


    class Meta:
        constraints = [
            models.UniqueConstraint(fields=["client", "name"], name="group_uniq_per_client")
        ]


class Invoice(BasePayment, PureDjangoModel):
    group = models.ForeignKey(
        InvoiceGroup, verbose_name=_("Invoice group"), related_name="invoices", on_delete=models.SET_NULL, null=True
    )

    number = models.CharField(verbose_name=_("Invoice number"), max_length=255)

    for_content_type = models.ForeignKey(ContentType, on_delete=models.SET_NULL, null=True)
    for_object_id = models.PositiveIntegerField()
    for_object = GenericForeignKey("for_content_type", "for_object_id")

    def get_purchased_items(self):
        return self.for_object.get_purchased_items()

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=["transaction_id", "group"], name="number_uniq_per_group")
        ]

    @property
    def purchased_items_table(self):
        items = [i._asdict() for i in self.get_purchased_items()]
        return PurchasedItemsTable(items)

    @property
    def totals_table(self):
        tax_amounts = {}
        for item in self.get_purchased_items():
            tax_amounts.setdefault(item.tax_rate, 0)
            tax_amounts[item.tax_rate] += item.price / (item.tax_rate + 100) * item.tax_rate

        values = []
        for tax_rate, total in tax_amounts.items():
            values.append({
                "name": _("Included VAT {} %").format(tax_rate),
                "value": total,
                "currency": self.currency,
            })

        values.append({
            "name": _("Gross total"),
            "value": self.total,
            "currency": self.currency,
        })

        return TotalsTable(values)