dashboard/billing/utils.py

# Copyright © 2022 Aravinth Manivannan <realaravinth@batsense.net>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
from enum import Enum, unique
from urllib.parse import urlparse, urlunparse
from datetime import datetime, timedelta, timezone

from payments import get_payment_model, RedirectNeeded, PaymentStatus
from django.core.mail import send_mail
from django.urls import reverse
from django.template.loader import render_to_string
from django.contrib.auth.models import User
from django.conf import settings
from django.shortcuts import get_object_or_404

from dash.models import Instance

Payment = get_payment_model()


def __get_delta():
    now = datetime.now(tz=timezone.utc)
    delta = now - timedelta(seconds=(60 * 60 * 24 * 30))  # one month
    return delta


def get_invoice_link(payment: Payment):
    invoice_link = reverse("billing.invoice.details", args=(payment.public_ref,))
    parsed = urlparse(settings.PAYMENT_HOST)
    return urlunparse((parsed.scheme, parsed.netloc, invoice_link, "", "", ""))


def payment_fullfilled(instance: Instance) -> bool:
    delta = __get_delta()

    payment = None
    for p in Payment.objects.filter(
        date__gt=(delta), instance_name=instance.name, vm_deleted=False
    ):
        if p.status == PaymentStatus.CONFIRMED:
            return True

    return False


@unique
class GenerateInvoiceErrorCode(Enum):
    ALREADY_PAID = "already paid"
    DUPLICATE_PAYMENT = "DUPLICATE PAYMENT"

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


class GenerateInvoiceException(Exception):
    error: str
    code: GenerateInvoiceErrorCode

    def __init__(self, code: GenerateInvoiceErrorCode):
        self.error = str(code)
        self.code = code

    def __str__(self):
        return self.error


def generate_invoice(instance: Instance) -> Payment:
    delta = __get_delta()

    payment = None
    for p in Payment.objects.filter(
        date__gt=(delta), instance_name=instance.name, vm_deleted=False
    ):
        if p.status == PaymentStatus.CONFIRMED:
            raise GenerateInvoiceException(code=GenerateInvoiceErrorCode.ALREADY_PAID)
        if any([p.status == PaymentStatus.INPUT, p.status == PaymentStatus.WAITING]):
            if payment is None:
                payment = p
            else:
                print(f"Duplicate payment {p}, deleting in favor of {payment}")
                p.delete()

    if payment is None:
        print("Payment not found, generating new payment")
        payment = Payment.objects.create(
            variant="stripe",  # this is the variant from PAYMENT_VARIANTS
            instance=instance,
        )

        invoice_link = get_invoice_link(payment=payment)

        ctx = {
            "username": instance.owned_by.username,
            "link": invoice_link,
            "payment": payment,
        }

        body = render_to_string(
            "billing/emails/payment-notification.txt",
            context=ctx,
        )

        email = instance.owned_by.email
        sender = settings.DEFAULT_FROM_EMAIL

        send_mail(
            subject="[Hostea] An invoice is generated for your Hostea VM",
            message=body,
            from_email=f"No reply Hostea<{sender}>",  # TODO read from settings.py
            recipient_list=[email],
        )

    return payment