(More or less) proper definition of "months", added more receipt preferences.

matemat/db/facade.py

@@ -577,6 +577,8 @@ class MatematDatabase(object):
         user.balance = old_balance + amount
 
     def check_receipt_due(self, user: User) -> bool:
+        if not isinstance(user.receipt_pref, ReceiptPreference):
+            raise TypeError()
         if user.receipt_pref == ReceiptPreference.NONE or user.email is None:
             return False
         with self.db.transaction() as c:
@@ -587,14 +589,10 @@ class MatematDatabase(object):
               ON r.user_id = u.user_id
             WHERE u.user_id = :user_id
             ''', [user.id])
-        last_receipt: int = c.fetchone()[0]
-        if user.receipt_pref == ReceiptPreference.MONTHLY:
-            date_diff: int = timedelta(days=31).total_seconds()
-        elif user.receipt_pref == ReceiptPreference.YEARLY:
-            date_diff = timedelta(days=365).total_seconds()
-        else:
-            raise ValueError()
-        return datetime.utcnow().timestamp() > last_receipt + date_diff
+        last_receipt: datetime = datetime.fromtimestamp(c.fetchone()[0])
+        next_receipt_due: datetime = user.receipt_pref.next_receipt_due(last_receipt)
+
+        return datetime.utcnow() > next_receipt_due
 
     def create_receipt(self, user: User, write: bool = False) -> Receipt:
         transactions: List[Transaction] = []

matemat/db/primitives/ReceiptPreference.py

@@ -1,5 +1,10 @@
+from typing import Callable
+
 from enum import Enum
 
+from datetime import datetime, timedelta
+from matemat.util.monthdelta import add_months
+
 
 class ReceiptPreference(Enum):
     """
@@ -10,8 +15,10 @@ class ReceiptPreference(Enum):
         e = object.__new__(cls)
         # The enum's internal value
         e._value_: int = args[0]
+        # The function calculating the date after which a new receipt is due.
+        e._datefunc: Callable[[datetime], datetime] = args[1]
         # The human-readable description
-        e._human_readable: str = args[1]
+        e._human_readable: str = args[2]
         return e
 
     @property
@@ -21,17 +28,35 @@ class ReceiptPreference(Enum):
         """
         return self._human_readable
 
+    def next_receipt_due(self, d: datetime) -> datetime:
+        return self._datefunc(d)
+
     """
     No receipts should be generated.
     """
-    NONE = 0, 'No receipts'
+    NONE = 0, (lambda d: None), 'No receipts'
+
+    """
+    A receipt should be generated once a week.
+    """
+    WEEKLY = 1, (lambda d: d + timedelta(weeks=1)), 'Weekly'
 
     """
     A receipt should be generated once a month.
     """
-    MONTHLY = 2, 'Aggregated, monthly'
+    MONTHLY = 2, (lambda d: add_months(d, 1)), 'Monthly'
+
+    """
+    A receipt should be generated once every three month.
+    """
+    QUARTERLY = 3, (lambda d: add_months(d, 3)), 'Quarterly'
+
+    """
+    A receipt should be generated once every six month.
+    """
+    BIANNUALLY = 4, (lambda d: add_months(d, 6)), 'Biannually'
 
     """
     A receipt should be generated once a year.
     """
-    YEARLY = 3, 'Aggregated, yearly'
+    YEARLY = 5, (lambda d: add_months(d, 12)), 'Annually'

matemat/db/test/test_facade.py

@@ -486,7 +486,7 @@ class DatabaseTest(unittest.TestCase):
             self.assertFalse(self.db.check_receipt_due(user4))
             self.assertTrue(self.db.check_receipt_due(user5))
             self.assertFalse(self.db.check_receipt_due(user6))
-            with self.assertRaises(ValueError):
+            with self.assertRaises(TypeError):
                 self.db.check_receipt_due(user7)
 
     def test_create_receipt(self):

matemat/util/monthdelta.py

@@ -0,0 +1,29 @@
+
+from typing import Tuple
+
+from datetime import datetime, timedelta
+import calendar
+
+
+def add_months(d: datetime, months: int) -> datetime:
+    """
+    Add the given number of months to the passed date, considering the varying numbers of days in a month.
+    :param d: The date time to add to.
+    :param months: The number of months to add to.
+    :return: A datetime object offset by the requested number of months.
+    """
+    if not isinstance(d, datetime) or not isinstance(months, int):
+        raise TypeError()
+    if months < 0:
+        raise ValueError('Can only add a positive number of months.')
+    nextmonth: Tuple[int, int] = (d.year, d.month)
+    days: int = 0
+    # Iterate the months between the passed date and the target month
+    for i in range(months):
+        days += calendar.monthlen(*nextmonth)
+        nextmonth = calendar.nextmonth(*nextmonth)
+    # Set the day of month temporarily to 1, then add the day offset to reach the 1st of the target month
+    newdate: datetime = d.replace(day=1) + timedelta(days=days)
+    # Re-set the day of month to the intended value, but capped by the max. day in the target month
+    newdate = newdate.replace(day=min(d.day, calendar.monthlen(newdate.year, newdate.month)))
+    return newdate

matemat/util/test/test_monthdelta.py

@@ -0,0 +1,61 @@
+
+import unittest
+
+from datetime import datetime
+
+from matemat.util.monthdelta import add_months
+
+
+class TestMonthDelta(unittest.TestCase):
+
+    def test_monthdelta_zero(self):
+        date = datetime(2018, 9, 8, 13, 37, 42)
+        offset_date = date
+        self.assertEqual(offset_date, add_months(date, 0))
+
+    def test_monthdelta_one(self):
+        date = datetime(2018, 9, 8, 13, 37, 42)
+        offset_date = date.replace(month=10)
+        self.assertEqual(offset_date, add_months(date, 1))
+
+    def test_monthdelta_two(self):
+        date = datetime(2018, 9, 8, 13, 37, 42)
+        offset_date = date.replace(month=11)
+        self.assertEqual(offset_date, add_months(date, 2))
+
+    def test_monthdelta_yearwrap(self):
+        date = datetime(2018, 9, 8, 13, 37, 42)
+        offset_date = date.replace(year=2019, month=1)
+        self.assertEqual(offset_date, add_months(date, 4))
+
+    def test_monthdelta_yearwrap_five(self):
+        date = datetime(2018, 9, 8, 13, 37, 42)
+        offset_date = date.replace(year=2023, month=3)
+        self.assertEqual(offset_date, add_months(date, 54))
+
+    def test_monthdelta_rounddown_31_30(self):
+        date = datetime(2018, 3, 31, 13, 37, 42)
+        offset_date = date.replace(month=4, day=30)
+        self.assertEqual(offset_date, add_months(date, 1))
+
+    def test_monthdelta_rounddown_feb(self):
+        date = datetime(2018, 1, 31, 13, 37, 42)
+        offset_date = date.replace(month=2, day=28)
+        self.assertEqual(offset_date, add_months(date, 1))
+
+    def test_monthdelta_rounddown_feb_leap(self):
+        date = datetime(2020, 1, 31, 13, 37, 42)
+        offset_date = date.replace(month=2, day=29)
+        self.assertEqual(offset_date, add_months(date, 1))
+
+    def test_fail_negative(self):
+        date = datetime(2020, 1, 31, 13, 37, 42)
+        with self.assertRaises(ValueError):
+            add_months(date, -1)
+
+    def test_fail_type(self):
+        date = datetime(2020, 1, 31, 13, 37, 42)
+        with self.assertRaises(TypeError):
+            add_months(date, 1.2)
+        with self.assertRaises(TypeError):
+            add_months(42, 1)