21953 Create datetime method to add business days to a date (bcgov#2815)

legal-api/src/legal_api/utils/datetime.py

@@ -14,7 +14,7 @@
 """Date time utilities."""
 # from datetime import datetime, timezone
 import time as _time
-from datetime import date, datetime as _datetime, timezone  # pylint: disable=unused-import # noqa: F401, I001, I005
+from datetime import date, datetime as _datetime, timedelta, timezone  # pylint: disable=unused-import # noqa: E501, F401, I001, I005
 # noqa: I003,I005
 
 
@@ -31,3 +31,17 @@ def utcnow(cls):
     def from_date(cls, date_obj):
         """Get a datetime object from a date object."""
         return datetime(date_obj.year, date_obj.month, date_obj.day)
+
+    @classmethod
+    def add_business_days(cls, from_date: _datetime, num_days: int):
+        """Add business days to an initial date. Only accounts for weekends, not holidays."""
+        current_date = from_date
+        business_days_to_add = abs(num_days)
+        inc = 1 if num_days > 0 else -1
+        while business_days_to_add > 0:
+            current_date += timedelta(days=inc)
+            weekday = current_date.weekday()
+            if weekday >= 5:  # sunday = 6
+                continue
+            business_days_to_add -= 1
+        return current_date

legal-api/tests/unit/utils/test_datetime.py

@@ -13,8 +13,9 @@
 # limitations under the License.
 
 """Tests to ensure the datetime wrappers are working as expected."""
-from datetime import datetime, timezone
+from datetime import date, datetime, timezone
 
+import pytest
 from freezegun import freeze_time
 
 
@@ -38,3 +39,39 @@ def test_datetime_isoformat():
         iso = d.isoformat()
         tz = iso[iso.find('+'):]
         assert tz == '+00:00'
+
+
+@pytest.mark.parametrize(
+    'test_name, from_date_str, num_days, expected_date_str', [
+        (
+            'ADD_WITHIN_WEEKDAYS',
+            '2024-06-19',
+            2,
+            '2024-06-21'
+        ),
+        (
+            'ADD_OVER_WEEKEND',
+            '2024-06-19',
+            5,
+            '2024-06-26'
+        ),
+        (
+            'SUB_WITHIN_WEEKDAYS',
+            '2024-06-19',
+            -2,
+            '2024-06-17'
+        ),
+        (
+            'SUB_OVER_WEEKEND',
+            '2024-06-19',
+            -5,
+            '2024-06-12'
+        ),
+    ]
+)
+def test_datetime_add_business_days(test_name, from_date_str, num_days, expected_date_str):
+    """Assert that business days are added to a date correctly."""
+    import legal_api.utils.datetime as _datetime
+    from_date = date.fromisoformat(from_date_str)
+    new_date = _datetime.datetime.add_business_days(from_date, num_days)
+    assert new_date == date.fromisoformat(expected_date_str)