email: Refactor calculation of delay for scheduled emails.

Refactors the logic for adjusting the delay for sending an email
to not land on a weekend so that it can be used to schedule any
number of onboarding emails we decide to send.

Consolidates duplicate testing into
`zerver/tests/test_email_notifications.py`. The initial test and
function were introduced in commit 610f2cbacf with the test
located in `zerver/tests/test_signup.py`.

Prep commit for adding new welcome / follow up email.

zerver/lib/email_notifications.py

@@ -679,24 +679,31 @@ def handle_missedmessage_emails(
         )
 
 
-def followup_day2_email_delay(user: UserProfile) -> timedelta:
-    days_to_delay = 2
+def get_onboarding_email_schedule(user: UserProfile) -> Dict[str, timedelta]:
+    onboarding_emails = {
+        # The delay should be 1 hour before the below specified number of days
+        # as our goal is to maximize the chance that this email is near the top
+        # of the user's inbox when the user sits down to deal with their inbox,
+        # or comes in while they are dealing with their inbox.
+        "followup_day2": timedelta(days=2, hours=-1),
+    }
+
     user_tz = user.timezone
     if user_tz == "":
         user_tz = "UTC"
     signup_day = user.date_joined.astimezone(zoneinfo.ZoneInfo(user_tz)).isoweekday()
-    if signup_day == 5:
-        # If the day is Friday then delay should be till Monday
-        days_to_delay = 3
-    elif signup_day == 4:
-        # If the day is Thursday then delay should be till Friday
-        days_to_delay = 1
 
-    # The delay should be 1 hour before the above calculated delay as
-    # our goal is to maximize the chance that this email is near the top
-    # of the user's inbox when the user sits down to deal with their inbox,
-    # or comes in while they are dealing with their inbox.
-    return timedelta(days=days_to_delay, hours=-1)
+    # User signed up on Thursday
+    if signup_day == 4:
+        # Send followup_day2 on Friday
+        onboarding_emails["followup_day2"] = timedelta(days=1, hours=-1)
+
+    # User signed up on Friday
+    if signup_day == 5:
+        # Send followup_day2 on Monday
+        onboarding_emails["followup_day2"] = timedelta(days=3, hours=-1)
+
+    return onboarding_emails
 
 
 def enqueue_welcome_emails(user: UserProfile, realm_creation: bool = False) -> None:
@@ -754,6 +761,10 @@ def enqueue_welcome_emails(user: UserProfile, realm_creation: bool = False) -> N
         context=context,
     )
 
+    # Any emails scheduled below should be added to the logic in get_onboarding_email_schedule
+    # to determine how long to delay sending the email based on when the user signed up.
+    onboarding_email_schedule = get_onboarding_email_schedule(user)
+
     if other_account_count == 0:
         send_future_email(
             "zerver/emails/followup_day2",
@@ -762,7 +773,7 @@ def enqueue_welcome_emails(user: UserProfile, realm_creation: bool = False) -> N
             from_name=from_name,
             from_address=from_address,
             context=context,
-            delay=followup_day2_email_delay(user),
+            delay=onboarding_email_schedule["followup_day2"],
         )
 
 

zerver/tests/test_email_notifications.py

@@ -25,7 +25,7 @@ from zerver.lib.email_notifications import (
     enqueue_welcome_emails,
     fix_emojis,
     fix_spoilers_in_html,
-    followup_day2_email_delay,
+    get_onboarding_email_schedule,
     handle_missedmessage_emails,
     include_realm_name_in_missedmessage_emails_subject,
     relative_to_full_url,
@@ -1749,14 +1749,84 @@ class TestMissedMessages(ZulipTestCase):
 
 
 class TestFollowupEmailDelay(ZulipTestCase):
-    def test_followup_day2_email_delay(self) -> None:
+    def test_get_onboarding_email_schedule(self) -> None:
         user_profile = self.example_user("hamlet")
-        # Test date_joined == Thursday
-        user_profile.date_joined = datetime(2018, 1, 4, 1, 0, 0, 0, tzinfo=timezone.utc)
-        self.assertEqual(followup_day2_email_delay(user_profile), timedelta(days=1, hours=-1))
-        # Test date_joined == Friday
+        dates_joined = {
+            "Monday": datetime(2018, 1, 1, 1, 0, 0, 0, tzinfo=timezone.utc),
+            "Tuesday": datetime(2018, 1, 2, 1, 0, 0, 0, tzinfo=timezone.utc),
+            "Wednesday": datetime(2018, 1, 3, 1, 0, 0, 0, tzinfo=timezone.utc),
+            "Thursday": datetime(2018, 1, 4, 1, 0, 0, 0, tzinfo=timezone.utc),
+            "Friday": datetime(2018, 1, 5, 1, 0, 0, 0, tzinfo=timezone.utc),
+            "Saturday": datetime(2018, 1, 6, 1, 0, 0, 0, tzinfo=timezone.utc),
+            "Sunday": datetime(2018, 1, 7, 1, 0, 0, 0, tzinfo=timezone.utc),
+        }
+
+        user_profile.date_joined = dates_joined["Monday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Wednesday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=2, hours=-1),
+        )
+
+        user_profile.date_joined = dates_joined["Tuesday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Thursday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=2, hours=-1),
+        )
+
+        user_profile.date_joined = dates_joined["Wednesday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Friday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=2, hours=-1),
+        )
+
+        user_profile.date_joined = dates_joined["Thursday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Friday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=1, hours=-1),
+        )
+
+        user_profile.date_joined = dates_joined["Friday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Monday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=3, hours=-1),
+        )
+
+        user_profile.date_joined = dates_joined["Saturday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Monday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=2, hours=-1),
+        )
+
+        user_profile.date_joined = dates_joined["Sunday"]
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Tuesday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=2, hours=-1),
+        )
+
+        # Time offset of America/Phoenix is -07:00
+        user_profile.timezone = "America/Phoenix"
+        # Test date_joined == Friday in UTC, but Thursday in the user's time zone
         user_profile.date_joined = datetime(2018, 1, 5, 1, 0, 0, 0, tzinfo=timezone.utc)
-        self.assertEqual(followup_day2_email_delay(user_profile), timedelta(days=3, hours=-1))
+        onboarding_email_schedule = get_onboarding_email_schedule(user_profile)
+        # followup_day2 email sent on Friday
+        self.assertEqual(
+            onboarding_email_schedule["followup_day2"],
+            timedelta(days=1, hours=-1),
+        )
 
 
 class TestCustomEmailSender(ZulipTestCase):

zerver/tests/test_signup.py

@@ -38,7 +38,7 @@ from zerver.actions.realm_settings import (
 from zerver.actions.users import change_user_is_active, do_change_user_role, do_deactivate_user
 from zerver.decorator import do_two_factor_login
 from zerver.forms import HomepageForm, check_subdomain_available
-from zerver.lib.email_notifications import enqueue_welcome_emails, followup_day2_email_delay
+from zerver.lib.email_notifications import enqueue_welcome_emails
 from zerver.lib.i18n import get_default_language_for_new_user
 from zerver.lib.initial_password import initial_password
 from zerver.lib.mobile_auth_otp import (
@@ -4170,49 +4170,6 @@ class MobileAuthOTPTest(ZulipTestCase):
         self.assertEqual(decrypted, api_key)
 
 
-class FollowupEmailTest(ZulipTestCase):
-    def test_followup_day2_email(self) -> None:
-        user_profile = self.example_user("hamlet")
-        # Test date_joined == Sunday
-        user_profile.date_joined = datetime.datetime(
-            2018, 1, 7, 1, 0, 0, 0, tzinfo=datetime.timezone.utc
-        )
-        self.assertEqual(
-            followup_day2_email_delay(user_profile), datetime.timedelta(days=2, hours=-1)
-        )
-        # Test date_joined == Tuesday
-        user_profile.date_joined = datetime.datetime(
-            2018, 1, 2, 1, 0, 0, 0, tzinfo=datetime.timezone.utc
-        )
-        self.assertEqual(
-            followup_day2_email_delay(user_profile), datetime.timedelta(days=2, hours=-1)
-        )
-        # Test date_joined == Thursday
-        user_profile.date_joined = datetime.datetime(
-            2018, 1, 4, 1, 0, 0, 0, tzinfo=datetime.timezone.utc
-        )
-        self.assertEqual(
-            followup_day2_email_delay(user_profile), datetime.timedelta(days=1, hours=-1)
-        )
-        # Test date_joined == Friday
-        user_profile.date_joined = datetime.datetime(
-            2018, 1, 5, 1, 0, 0, 0, tzinfo=datetime.timezone.utc
-        )
-        self.assertEqual(
-            followup_day2_email_delay(user_profile), datetime.timedelta(days=3, hours=-1)
-        )
-
-        # Time offset of America/Phoenix is -07:00
-        user_profile.timezone = "America/Phoenix"
-        # Test date_joined == Friday in UTC, but Thursday in the user's time zone
-        user_profile.date_joined = datetime.datetime(
-            2018, 1, 5, 1, 0, 0, 0, tzinfo=datetime.timezone.utc
-        )
-        self.assertEqual(
-            followup_day2_email_delay(user_profile), datetime.timedelta(days=1, hours=-1)
-        )
-
-
 class NoReplyEmailTest(ZulipTestCase):
     def test_noreply_email_address(self) -> None:
         self.assertTrue(