From 4aca5705498d706fc403786a2eca8378d8ca11a3 Mon Sep 17 00:00:00 2001
From: Matias Bordese <mbordese@gmail.com>
Date: Mon, 7 Nov 2022 17:38:10 -0300
Subject: [PATCH] Ensure start date matches by_day selection

---
 .../schedules/models/custom_on_call_shift.py  |  9 ++++
 .../tests/test_custom_on_call_shift.py        | 49 +++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/engine/apps/schedules/models/custom_on_call_shift.py b/engine/apps/schedules/models/custom_on_call_shift.py
index c285dba9..96cc2db2 100644
--- a/engine/apps/schedules/models/custom_on_call_shift.py
+++ b/engine/apps/schedules/models/custom_on_call_shift.py
@@ -121,6 +121,7 @@ class CustomOnCallShift(models.Model):
         SATURDAY: "SA",
         SUNDAY: "SU",
     }
+    ICAL_WEEKDAY_REVERSE_MAP = {v: k for k, v in ICAL_WEEKDAY_MAP.items()}
 
     WEB_WEEKDAY_MAP = {
         "MO": "Monday",
@@ -365,6 +366,14 @@ class CustomOnCallShift(models.Model):
             else:
                 start = self.get_rotation_date(event_ical)
 
+            # Make sure we respect the selected days if any when defining start date
+            if self.frequency is not None and self.by_day:
+                start_day = CustomOnCallShift.ICAL_WEEKDAY_MAP[start.weekday()]
+                if start_day not in self.by_day:
+                    expected_start_day = min(CustomOnCallShift.ICAL_WEEKDAY_REVERSE_MAP[d] for d in self.by_day)
+                    delta = (expected_start_day - start.weekday()) % 7
+                    start = start + timezone.timedelta(days=delta)
+
             if self.frequency == CustomOnCallShift.FREQUENCY_DAILY and self.by_day:
                 result = self._daily_by_day_to_ical(time_zone, start, users_queue)
                 all_rotation_checked = True
diff --git a/engine/apps/schedules/tests/test_custom_on_call_shift.py b/engine/apps/schedules/tests/test_custom_on_call_shift.py
index 8a746169..3da17a66 100644
--- a/engine/apps/schedules/tests/test_custom_on_call_shift.py
+++ b/engine/apps/schedules/tests/test_custom_on_call_shift.py
@@ -386,6 +386,55 @@ def test_rolling_users_event_daily_by_day(
         assert len(users_on_call) == 0
 
 
+@pytest.mark.django_db
+def test_rolling_users_event_daily_by_day_off_start(make_organization_and_user, make_on_call_shift, make_schedule):
+    organization, user_1 = make_organization_and_user()
+
+    schedule = make_schedule(organization, schedule_class=OnCallScheduleWeb)
+    now = timezone.now().replace(hour=0, minute=0, second=0, microsecond=0)
+    current_week_monday = now - timezone.timedelta(days=now.weekday())
+
+    # WE, FR
+    weekdays = [2, 4]
+    by_day = [CustomOnCallShift.ICAL_WEEKDAY_MAP[day] for day in weekdays]
+    data = {
+        "priority_level": 1,
+        "start": current_week_monday,
+        "rotation_start": current_week_monday,
+        "duration": timezone.timedelta(seconds=10800),
+        "frequency": CustomOnCallShift.FREQUENCY_DAILY,
+        "interval": 1,
+        "by_day": by_day,
+        "schedule": schedule,
+    }
+    rolling_users = [[user_1]]
+    on_call_shift = make_on_call_shift(
+        organization=organization, shift_type=CustomOnCallShift.TYPE_ROLLING_USERS_EVENT, **data
+    )
+    on_call_shift.add_rolling_users(rolling_users)
+
+    date = current_week_monday + timezone.timedelta(minutes=5)
+
+    user_1_on_call_dates = [date + timezone.timedelta(days=2), date + timezone.timedelta(days=4)]
+    nobody_on_call_dates = [
+        date,  # MO
+        date + timezone.timedelta(days=1),  # TU
+        date + timezone.timedelta(days=3),  # TH
+        date + timezone.timedelta(days=5),  # SA
+        date + timezone.timedelta(days=6),  # SU
+        date + timezone.timedelta(days=7),  # MO
+    ]
+
+    for dt in user_1_on_call_dates:
+        users_on_call = list_users_to_notify_from_ical(schedule, dt)
+        assert len(users_on_call) == 1
+        assert user_1 in users_on_call
+
+    for dt in nobody_on_call_dates:
+        users_on_call = list_users_to_notify_from_ical(schedule, dt)
+        assert len(users_on_call) == 0
+
+
 @pytest.mark.django_db
 def test_rolling_users_event_with_interval_daily_by_day(
     make_organization_and_user, make_user_for_organization, make_on_call_shift, make_schedule