Pay: move some model-related methods from helpers to models

Otherwise we end up in circular dependency hell

uncloud/uncloud_pay/helpers.py

@@ -2,32 +2,9 @@ from functools import reduce
 from datetime import datetime
 from rest_framework import mixins
 from rest_framework.viewsets import GenericViewSet
-from django.db.models import Q
-from .models import Bill, Payment, PaymentMethod, Order
 from django.utils import timezone
-from django.core.exceptions import ObjectDoesNotExist
 from calendar import monthrange
 
-def get_balance_for(user):
-    bills = reduce(
-            lambda acc, entry: acc + entry.total,
-            Bill.objects.filter(owner=user),
-            0)
-    payments = reduce(
-            lambda acc, entry: acc + entry.amount,
-            Payment.objects.filter(owner=user),
-            0)
-    return payments - bills
-
-def get_payment_method_for(user):
-    methods = PaymentMethod.objects.filter(owner=user)
-    for method in methods:
-        # Do we want to do something with non-primary method?
-        if method.primary:
-            return method
-
-    return None
-
 def beginning_of_month(year, month):
     tz = timezone.get_current_timezone()
     return datetime(year=year, month=month, day=1, tzinfo=tz)
@@ -38,53 +15,6 @@ def end_of_month(year, month):
     return datetime(year=year, month=month, day=days,
             hour=23, minute=59, second=59, tzinfo=tz)
 
-def generate_bills_for(year, month, user, allowed_delay):
-    # /!\ We exclusively work on the specified year and month.
-
-    # Default values for next bill (if any). Only saved at the end of
-    # this method, if relevant.
-    next_bill = Bill(owner=user,
-            starting_date=beginning_of_month(year, month),
-            ending_date=end_of_month(year, month),
-            creation_date=timezone.now(),
-            due_date=timezone.now() + allowed_delay)
-
-    # Select all orders active on the request period.
-    orders = Order.objects.filter(
-            Q(ending_date__gt=next_bill.starting_date) | Q(ending_date__isnull=True),
-            owner=user)
-
-    # Check if there is already a bill covering the order and period pair:
-    #   * Get latest bill by ending_date: previous_bill.ending_date
-    #   * If previous_bill.ending_date is before next_bill.ending_date, a new
-    #   bill has to be generated.
-    unpaid_orders = []
-    for order in orders:
-        try:
-            previous_bill = order.bill.latest('ending_date')
-        except ObjectDoesNotExist:
-            previous_bill = None
-
-        if previous_bill == None or previous_bill.ending_date < next_bill.ending_date:
-            unpaid_orders.append(order)
-
-    # Commit next_bill if it there are 'unpaid' orders.
-    if len(unpaid_orders) > 0:
-        next_bill.save()
-
-        # It is not possible to register many-to-many relationship before
-        # the two end-objects are saved in database.
-        for order in unpaid_orders:
-            order.bill.add(next_bill)
-
-        # TODO: use logger.
-        print("Generated bill {} (amount: {}) for user {}."
-                .format(next_bill.uuid, next_bill.total, user))
-
-        return next_bill
-
-    # Return None if no bill was created.
-
 class ProductViewSet(mixins.CreateModelMixin,
                    mixins.RetrieveModelMixin,
                    mixins.ListModelMixin,

uncloud/uncloud_pay/management/commands/charge-negative-balance.py

@@ -1,7 +1,6 @@
 from django.core.management.base import BaseCommand
 from uncloud_auth.models import User
-from uncloud_pay.models import Order, Bill
+from uncloud_pay.models import Order, Bill, PaymentMethod, get_balance_for
-from uncloud_pay.helpers import get_balance_for, get_payment_method_for
 
 from datetime import timedelta
 from django.utils import timezone
@@ -19,7 +18,7 @@ class Command(BaseCommand):
             balance = get_balance_for(user)
             if balance < 0:
                 print("User {} has negative balance ({}), charging.".format(user.username, balance))
-                payment_method = get_payment_method_for(user)
+                payment_method = PaymentMethod.get_primary_for(user)
                 if payment_method != None:
                     amount_to_be_charged = abs(balance)
                     charge_ok = payment_method.charge(amount_to_be_charged)

uncloud/uncloud_pay/management/commands/generate-bills.py

@@ -7,7 +7,7 @@ from django.core.exceptions import ObjectDoesNotExist
 
 from datetime import timedelta, date
 from django.utils import timezone
-from uncloud_pay.helpers import generate_bills_for
+from uncloud_pay.models import Bill
 
 BILL_PAYMENT_DELAY=timedelta(days=10)
 
@@ -28,7 +28,7 @@ class Command(BaseCommand):
 
         for user in users:
             now = timezone.now()
-            generate_bills_for(
+            Bill.generate_for(
                     year=now.year,
                     month=now.month,
                     user=user,

uncloud/uncloud_pay/management/commands/handle-overdue-bills.py

@@ -1,7 +1,6 @@
 from django.core.management.base import BaseCommand
 from uncloud_auth.models import User
-from uncloud_pay.models import Order, Bill
+from uncloud_pay.models import Order, Bill, get_balance_for
-from uncloud_pay.helpers import get_balance_for, get_payment_method_for
 
 from datetime import timedelta
 from django.utils import timezone

uncloud/uncloud_pay/models.py

@@ -1,17 +1,23 @@
 from django.db import models
-from functools import reduce
+from django.db.models import Q
 from django.contrib.auth import get_user_model
 from django.core.validators import MinValueValidator
 from django.utils.translation import gettext_lazy as _
 from django.utils import timezone
+from django.dispatch import receiver
+from django.core.exceptions import ObjectDoesNotExist
+import django.db.models.signals as signals
+
+import uuid
+from functools import reduce
 from math import ceil
 from datetime import timedelta
 from calendar import monthrange
+
 import uncloud_pay.stripe
+from uncloud_pay.helpers import beginning_of_month, end_of_month
 
 from decimal import Decimal
-import uuid
-
 # Define DecimalField properties, used to represent amounts of money.
 AMOUNT_MAX_DIGITS=10
 AMOUNT_DECIMALS=2
@@ -26,6 +32,34 @@ class RecurringPeriod(models.TextChoices):
     PER_HOUR   = 'HOUR', _('Per Hour')
     PER_SECOND = 'SECOND', _('Per Second')
 
+# See https://docs.djangoproject.com/en/dev/ref/models/fields/#field-choices-enum-types
+class ProductStatus(models.TextChoices):
+    PENDING          = 'PENDING', _('Pending')
+    AWAITING_PAYMENT = 'AWAITING_PAYMENT', _('Awaiting payment')
+    BEING_CREATED    = 'BEING_CREATED', _('Being created')
+    ACTIVE           = 'ACTIVE', _('Active')
+    DELETED          = 'DELETED', _('Deleted')
+
+###
+# Users.
+
+def get_balance_for(user):
+    bills = reduce(
+            lambda acc, entry: acc + entry.total,
+            Bill.objects.filter(owner=user),
+            0)
+    payments = reduce(
+            lambda acc, entry: acc + entry.amount,
+            Payment.objects.filter(owner=user),
+            0)
+    return payments - bills
+
+class StripeCustomer(models.Model):
+    owner = models.OneToOneField( get_user_model(),
+            primary_key=True,
+            on_delete=models.CASCADE)
+    stripe_id = models.CharField(max_length=32)
+
 ###
 # Payments and Payment Methods.
 
@@ -100,15 +134,19 @@ class PaymentMethod(models.Model):
         else:
             raise Exception('Cannot charge negative amount.')
 
+
+    def get_primary_for(user):
+        methods = PaymentMethod.objects.filter(owner=user)
+        for method in methods:
+            # Do we want to do something with non-primary method?
+            if method.primary:
+                return method
+
+        return None
+
     class Meta:
         unique_together = [['owner', 'primary']]
 
-class StripeCustomer(models.Model):
-    owner = models.OneToOneField( get_user_model(),
-            primary_key=True,
-            on_delete=models.CASCADE)
-    stripe_id = models.CharField(max_length=32)
-
 ###
 # Bills & Payments.
 
@@ -144,6 +182,55 @@ class Bill(models.Model):
         # A bill is final when its ending date is passed.
         return self.ending_date < timezone.now()
 
+    @staticmethod
+    def generate_for(year, month, user, allowed_delay):
+        # /!\ We exclusively work on the specified year and month.
+
+        # Default values for next bill (if any). Only saved at the end of
+        # this method, if relevant.
+        next_bill = Bill(owner=user,
+                starting_date=beginning_of_month(year, month),
+                ending_date=end_of_month(year, month),
+                creation_date=timezone.now(),
+                due_date=timezone.now() + allowed_delay)
+
+        # Select all orders active on the request period.
+        orders = Order.objects.filter(
+                Q(ending_date__gt=next_bill.starting_date) | Q(ending_date__isnull=True),
+                owner=user)
+
+        # Check if there is already a bill covering the order and period pair:
+        #   * Get latest bill by ending_date: previous_bill.ending_date
+        #   * If previous_bill.ending_date is before next_bill.ending_date, a new
+        #   bill has to be generated.
+        unpaid_orders = []
+        for order in orders:
+            try:
+                previous_bill = order.bill.latest('ending_date')
+            except ObjectDoesNotExist:
+                previous_bill = None
+
+            if previous_bill == None or previous_bill.ending_date < next_bill.ending_date:
+                unpaid_orders.append(order)
+
+        # Commit next_bill if it there are 'unpaid' orders.
+        if len(unpaid_orders) > 0:
+            next_bill.save()
+
+            # It is not possible to register many-to-many relationship before
+            # the two end-objects are saved in database.
+            for order in unpaid_orders:
+                order.bill.add(next_bill)
+
+            # TODO: use logger.
+            print("Generated bill {} (amount: {}) for user {}."
+                    .format(next_bill.uuid, next_bill.total, user))
+
+            return next_bill
+
+        # Return None if no bill was created.
+        return None
+
 class BillRecord():
     """
     Entry of a bill, dynamically generated from order records.
@@ -258,6 +345,10 @@ class Order(models.Model):
                 recurring_price=recurring_price,
                 description=description)
 
+    def generate_bill(self):
+        pass
+
+
 class OrderRecord(models.Model):
     """
     Order records store billing informations for products: the actual product
@@ -305,15 +396,9 @@ class Product(models.Model):
 
     description = ""
 
-    status = models.CharField(max_length=256,
+    status = models.CharField(max_length=32,
-                              choices = (
+            choices=ProductStatus.choices,
-                                  ('pending', 'Pending'),
+            default=ProductStatus.AWAITING_PAYMENT)
-                                  ('being_created', 'Being created'),
-                                  ('active', 'Active'),
-                                  ('deleted', 'Deleted')
-                              ),
-                              default='pending'
-    )
 
     order = models.ForeignKey(Order,
                               on_delete=models.CASCADE,

uncloud/uncloud_pay/serializers.py

@@ -1,13 +1,6 @@
 from django.contrib.auth import get_user_model
 from rest_framework import serializers
 from .models import *
-from .helpers import get_balance_for
-
-from functools import reduce
-from uncloud_vm.serializers import VMProductSerializer
-from uncloud_vm.models import VMProduct
-
-import uncloud_pay.stripe as stripe
 
 ###
 # Users.
@@ -19,8 +12,6 @@ class UserSerializer(serializers.ModelSerializer):
 
     # Display current 'balance'
     balance = serializers.SerializerMethodField('get_balance')
-    def __sum_balance(self, entries):
-        return reduce(lambda acc, entry: acc + entry.amount, entries, 0)
 
     def get_balance(self, user):
         return get_balance_for(user)
@@ -92,6 +83,3 @@ class OrderSerializer(serializers.ModelSerializer):
         model = Order
         fields = ['uuid', 'creation_date', 'starting_date', 'ending_date',
                 'bill', 'recurring_period', 'records', 'recurring_price', 'one_time_price']
-
-class ProductSerializer(serializers.Serializer):
-    vms = VMProductSerializer(many=True, read_only=True)