feat: Add get_minimum_due_date function

Author: sondrelg

netsgiro/__init__.py

@@ -5,9 +5,10 @@
 from netsgiro.constants import *
 from netsgiro.enums import *
 from netsgiro.objects import *
+from netsgiro.utils import *
 
-from netsgiro import constants, enums, objects  # isort: skip
+from netsgiro import constants, enums, objects, utils  # isort: skip
 
 __version__ = '1.3.0'
 
-__all__: List[str] = constants.__all__ + enums.__all__ + objects.__all__
+__all__: List[str] = constants.__all__ + enums.__all__ + objects.__all__ + utils.__all__

netsgiro/utils.py

@@ -0,0 +1,56 @@
+from contextlib import suppress
+from datetime import timedelta
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from datetime import date, datetime
+
+try:
+    import zoneinfo
+except ImportError:
+    from backports import zoneinfo  # type: ignore[no-redef]
+
+__all__ = ['get_minimum_due_date']
+
+# Nets operates in the Norwegian timezone
+OSLO_TZ = zoneinfo.ZoneInfo('Europe/Oslo')
+
+
+def get_minimum_due_date(now: 'datetime') -> 'date':
+    """
+    Return the minimum valid due date for an avtalegiro ocrgiro created right now.
+
+    The avtalegiro spec specifies that customers should have at least
+    4 calendar days notice before a payment, so files containing due dates
+    earlier than that will fail.
+
+    "Calendar days" include weekends, but not holidays, so the holidays
+    library is used to offset by holidays if it's installed.
+
+    Logic is used for validation in netsgiro internally, but is also exported
+    to be used downstream, when generating OCR files.
+    """
+    today = now.date()
+
+    # 14:00 is the cut-off for sending in new transmissions;
+    # files sent after 14:00 are processed the next day.
+    delta = 4 if now.hour < 14 else 5
+
+    # Adjust for holidays, if the dependency is installed
+    # - Users of the library that want this, should install
+    # - netsgiro with `pip install netsgiro[holidays]
+    with suppress(ImportError):
+        from holidays import country_holidays
+
+        # Get holidays
+        holidays_in_the_date_range = country_holidays('NO')[now : now + timedelta(days=delta)]  # type: ignore[misc]
+
+        # Add days to `delta` for each holiday found in the date range
+        delta += len(holidays_in_the_date_range)
+
+    # Calendar days don't count weekends, but file do have
+    # to be received on weekdays to be processed the same day
+    if today.weekday() in [5, 6]:
+        delta += 7 - today.weekday()
+
+    return (now + timedelta(days=delta)).date()

setup.cfg

@@ -14,6 +14,7 @@ ignore=
 
 per-file-ignores=
     netsgiro/__init__.py:F403,F401,
+    netsgiro/utils.py:E203,E501,
 
 exclude =
     .git,

tests/test_utils.py

@@ -0,0 +1,72 @@
+from datetime import datetime, timedelta
+
+import holidays
+
+from netsgiro.utils import OSLO_TZ, get_minimum_due_date
+
+monday = datetime(2022, 3, 28, 13, 59, tzinfo=OSLO_TZ)
+
+
+def test_minimum_due_date_before_cutoff():
+    """
+    Files generated before 14:00 Norwegian time should be
+    adjusted by 4 days, minimum.
+    """
+    assert get_minimum_due_date(monday) == (monday + timedelta(days=4)).date()
+
+
+monday_after_cutoff = datetime(2022, 4, 1, 14, 1, tzinfo=OSLO_TZ)
+
+
+def test_minimum_due_date_after_cutoff():
+    """
+    Because files sent in after 14:00 are processed the next day, files
+    generated after 14:00 Norwegian time should be adjusted by 5 days.
+    """
+    assert (
+        get_minimum_due_date(monday_after_cutoff)
+        == (monday_after_cutoff + timedelta(days=5)).date()
+    )
+
+
+day_before_easter = datetime(2022, 4, 13, 13, 59, tzinfo=OSLO_TZ)
+
+
+def test_minimum_due_date_with_holidays_before_cutoff():
+    """
+    There are 2 holidays in the span 13-17th of April 2022,
+    so we expect the function to adjust the timedelta by 2 days.
+    """
+    assert get_minimum_due_date(day_before_easter) == (day_before_easter + timedelta(days=6)).date()
+
+
+day_before_easter_after_cutoff = datetime(2022, 4, 13, 23, 59, tzinfo=OSLO_TZ)
+
+
+def test_minimum_due_date_with_holidays_after_cutoff():
+    """
+    If we send in the file after the cut-off, number of
+    holidays is upped to 3, so we expect 2 more days of offsetting.
+    """
+    assert (
+        get_minimum_due_date(day_before_easter_after_cutoff)
+        == (day_before_easter_after_cutoff + timedelta(days=8)).date()
+    )
+
+
+friday = datetime(2022, 4, 1, 23, 59, tzinfo=OSLO_TZ)
+
+
+def test_minimum_due_date_with_now_being_a_saturday():
+    assert get_minimum_due_date(friday) == (friday + timedelta(days=5)).date()
+
+
+def test_minimum_due_date_without_holiday_dependency():
+    """
+    Make sure an ImportError from a missing dependency isn't propagated.
+    """
+    import sys
+
+    sys.modules['holidays'] = None
+    assert get_minimum_due_date(monday) == (monday + timedelta(days=4)).date()
+    sys.modules['holidays'] = holidays