add User.suggested_emails

app/models.py

@@ -208,6 +208,21 @@ class User(db.Model, ModelMixin, UserMixin):
 
         self.promo_codes = ",".join(current_promo_codes)
 
+    def suggested_emails(self) -> (str, [str]):
+        """return suggested email and other email choices """
+        all_gen_emails = [ge.email for ge in GenEmail.filter_by(user_id=self.id)]
+        if self.can_create_new_email():
+            # create a new email
+            suggested_gen_email = generate_email()
+        else:
+            # pick an email from the list of gen emails
+            suggested_gen_email = random.choice(all_gen_emails)
+
+        return (
+            suggested_gen_email,
+            list(set(all_gen_emails).difference(set([suggested_gen_email]))),
+        )
+
 
 class ActivationCode(db.Model, ModelMixin):
     """For activate user account"""

tests/test_models.py

@@ -15,3 +15,42 @@ def test_profile_picture_url(flask_client):
     db.session.commit()
 
     assert user.profile_picture_url() == "http://sl.test/static/default-avatar.png"
+
+
+def test_suggested_emails_for_user_who_can_create_new_email(flask_client):
+    user = User.create(
+        email="a@b.c", password="password", name="Test User", activated=True
+    )
+    db.session.commit()
+
+    suggested_email, other_emails = user.suggested_emails()
+    assert suggested_email
+    assert len(other_emails) == 1
+
+    # the suggested email is new and not exist in GenEmail
+    assert GenEmail.get_by(email=suggested_email) is None
+
+    # all other emails are generated emails
+    assert GenEmail.get_by(email=other_emails[0])
+
+
+def test_suggested_emails_for_user_who_cannot_create_new_email(flask_client):
+    user = User.create(
+        email="a@b.c", password="password", name="Test User", activated=True
+    )
+    user.plan = PlanEnum.free
+    db.session.commit()
+
+    # make sure user runs out of quota to create new email
+    for i in range(MAX_NB_EMAIL_FREE_PLAN):
+        GenEmail.create_new_gen_email(user_id=user.id)
+    db.session.commit()
+
+    suggested_email, other_emails = user.suggested_emails()
+
+    # the suggested email is chosen from existing GenEmail
+    assert GenEmail.get_by(email=suggested_email)
+
+    # all other emails are generated emails
+    for email in other_emails:
+        assert GenEmail.get_by(email=email)