schon/payments/models.py

from constance import config
from django.conf import settings
from django.contrib.postgres.indexes import GinIndex
from django.db.models import (
    CASCADE,
    CharField,
    FloatField,
    ForeignKey,
    JSONField,
    OneToOneField,
    PositiveIntegerField,
    QuerySet,
    Sum,
)
from django.utils.timezone import now
from django.utils.translation import gettext_lazy as _

from core.abstract import NiceModel


class Transaction(NiceModel):
    amount = FloatField(null=False, blank=False)
    balance = ForeignKey("payments.Balance", on_delete=CASCADE, blank=True, null=True, related_name="transactions")
    currency = CharField(max_length=3, null=False, blank=False)
    payment_method = CharField(max_length=20, null=True, blank=True)
    order = ForeignKey(
        "core.Order",
        on_delete=CASCADE,
        blank=True,
        null=True,
        help_text=_("order to process after paid"),
        related_name="payments_transactions",
    )
    process = JSONField(verbose_name=_("processing details"), default=dict)
    gateway = ForeignKey("payments.Gateway", on_delete=CASCADE, blank=True, null=True, related_name="transactions")

    def __str__(self):
        return (
            f"{self.balance.user.email} | {self.amount}"
            if self.balance
            else f"{self.order.attributes.get('customer_email')} | {self.amount}"
        )

    def save(self, **kwargs):
        if self.amount != 0.0 and (
            (config.PAYMENT_GATEWAY_MINIMUM <= self.amount <= config.PAYMENT_GATEWAY_MAXIMUM)
            or (config.PAYMENT_GATEWAY_MINIMUM == 0 and config.PAYMENT_GATEWAY_MAXIMUM == 0)
        ):
            if len(str(self.amount).split(".")[1]) > 2:
                self.amount = round(self.amount, 2)
            super().save(**kwargs)
            return self
        raise ValueError(
            _(f"transaction amount must fit into {config.PAYMENT_GATEWAY_MINIMUM}-{config.PAYMENT_GATEWAY_MAXIMUM}")
        )

    class Meta:
        verbose_name = _("transaction")
        verbose_name_plural = _("transactions")
        indexes = [
            GinIndex(fields=["process"]),
        ]


class Balance(NiceModel):
    amount = FloatField(null=False, blank=False, default=0)
    user = OneToOneField(
        to="vibes_auth.User", on_delete=CASCADE, blank=True, null=True, related_name="payments_balance"
    )
    transactions: QuerySet["Transaction"]

    def __str__(self):
        return f"{self.user.email} | {self.amount}"

    class Meta:
        verbose_name = _("balance")
        verbose_name_plural = _("balances")

    def save(self, **kwargs):
        if self.amount != 0.0 and len(str(self.amount).split(".")[1]) > 2:
            self.amount = round(self.amount, 2)
        super().save(**kwargs)


class Gateway(NiceModel):
    name = CharField(max_length=20, null=False, blank=False, verbose_name=_("name"))
    default_currency = CharField(
        max_length=3, null=False, blank=False, verbose_name=_("default currency"), choices=settings.CURRENCIES
    )
    currencies = CharField(
        max_length=3,
        null=False,
        blank=False,
        verbose_name=_("currencies"),
        help_text=_(f"comma separated list of currencies supported by this gateway, choose from {settings.CURRENCIES}"),
    )
    integration_path = CharField(max_length=255, null=True, blank=True)
    minimum_transaction_amount = FloatField(
        null=False, blank=False, default=0, verbose_name=_("minimum transaction amount")
    )
    maximum_transaction_amount = FloatField(
        null=False, blank=False, default=0, verbose_name=_("maximum transaction amount")
    )
    daily_limit = PositiveIntegerField(
        null=False,
        blank=False,
        default=0,
        verbose_name=_("daily limit"),
        help_text=_("daily sum limit of transactions' amounts. 0 means no limit"),
    )
    monthly_limit = PositiveIntegerField(
        null=False,
        blank=False,
        default=0,
        verbose_name=_("monthly limit"),
        help_text=_("monthly sum limit of transactions' amounts. 0 means no limit"),
    )
    priority = PositiveIntegerField(null=False, blank=False, default=10, verbose_name=_("priority"), unique=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = _("payment gateway")
        verbose_name_plural = _("payment gateways")

    @property
    def can_be_used(self) -> bool:
        today = now().date()
        current_month_start = today.replace(day=1)

        daily_sum = self.transactions.filter(created__date=today).aggregate(total=Sum("amount"))["total"] or 0

        monthly_sum = (
            self.transactions.filter(created__gte=current_month_start).aggregate(total=Sum("amount"))["total"] or 0
        )

        daily_ok = self.daily_limit == 0 or daily_sum < self.daily_limit
        monthly_ok = self.monthly_limit == 0 or monthly_sum < self.monthly_limit

        return daily_ok and monthly_ok