Restoroo/core/models/billing.py

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

from .profiles import Profile


class ExpenseTypeChoices(models.IntegerChoices):
    """Defines different types of expenses
    """
    MONTHLY_FEE = (0, _("Monthly Fee"))
    SUPPORT = (1, _("Support"))
    DEVELOPMENT = (2, _("Custom Development"))
    COMMISSION = (3, _("Commission"))
    CONTRIBUTION = (4, _("Contribution"))
    OTHER = (99, _("Various Expenses"))


class Expense(models.Model):
    """Contains information on an individual expense to be invoiced

    By relation to an Invoice model, this is simultaneously an invoice item
    """
    expense_type = models.IntegerField(
        choices=ExpenseTypeChoices.choices, null=True, blank=True)
    text = models.CharField(max_length=256)
    payer = models.ForeignKey(Profile, models.PROTECT)

    """Of course, an Expense needs 
    """

    """An activity leading to an expense can have a starting and ending date
    (the day a reservation was made in case of per-reservation commissions,
    or the month for which a monthly fee is due) - but this is optional.
    """
    datetime_from = models.DateTimeField(null=True, blank=True)
    datetime_to = models.DateTimeField(null=True, blank=True)

    """An expense can be related to any other object in the database – for
    example, it can be related to a Reservation object for a per-reservation
    commission, to a Restaurant object for its monthly fee, or to a Profile
    object for a per-user fee. This also allows easy reverse lookups to find
    out which expenses have occurred for which object. This is optional.
    """
    object_type = models.ForeignKey(
        ContentType, on_delete=models.CASCADE, null=True)
    object_id = models.PositiveIntegerField(null=True, blank=True)
    related_object = GenericForeignKey('object_type', 'object_id', null=True)