Add function for finding user mentions

tests/test_comments.py

@@ -1,9 +1,8 @@
 import pytest
 from srht.database import db
-from todosrht.tickets import add_comment
+from todosrht.tickets import add_comment, find_mentioned_users
 from todosrht.types import TicketResolution, TicketStatus
 from todosrht.types import TicketSubscription, EventType
-from unittest.mock import patch
 
 from .factories import UserFactory, TrackerFactory, TicketFactory
 
@@ -170,3 +169,21 @@ def test_failed_comments():
 
     with pytest.raises(AssertionError):
         add_comment(user, ticket)
+
+
+def test_find_mentioned_users():
+    comment = "mentioning users ~mention1, ~mention2, and ~mention3 in a comment"
+
+    assert find_mentioned_users(comment) == set()
+
+    u1 = UserFactory(username="mention1")
+    db.session.commit()
+    assert find_mentioned_users(comment) == {u1}
+
+    u2 = UserFactory(username="mention2")
+    db.session.commit()
+    assert find_mentioned_users(comment) == {u1, u2}
+
+    u3 = UserFactory(username="mention3")
+    db.session.commit()
+    assert find_mentioned_users(comment) == {u1, u2, u3}

todosrht/tickets.py

@@ -1,3 +1,4 @@
+import re
 from collections import namedtuple
 from datetime import datetime
 from srht.config import cfg
@@ -5,7 +6,7 @@ from srht.database import db
 from todosrht.email import notify
 from todosrht.types import Event, EventType, EventNotification
 from todosrht.types import TicketComment, TicketStatus, TicketSubscription
-from todosrht.types import TicketSeen, TicketAssignee
+from todosrht.types import TicketSeen, TicketAssignee, User
 from todosrht.urls import ticket_url
 from sqlalchemy import func
 
@@ -20,6 +21,14 @@ StatusChange = namedtuple("StatusChange", [
     "new_resolution",
 ])
 
+# Matches user mentions, e.g. ~username
+USER_MENTION_PATTERN = re.compile(r"~(\w+)\b")
+
+def find_mentioned_users(text):
+    usernames = re.findall(USER_MENTION_PATTERN, text)
+    users = User.query.filter(User.username.in_(usernames)).all()
+    return set(users)
+
 def _create_comment(ticket, user, text):
     comment = TicketComment()
     comment.text = text