fix(anti-spam): delete all duplicate messages, not just triggering one

src/bot/handlers/duplicate_spam.py

@@ -42,6 +42,7 @@ class RecentMessage:
     timestamp: datetime
     normalized_text: str
     message_id: int
+    delete_attempted: bool = False
 
 
 def normalize_text(text: str) -> str:
@@ -86,13 +87,6 @@ def _prune_old_messages(
         dq.popleft()
 
 
-def count_similar_in_window(
-    dq: deque[RecentMessage], normalized: str, threshold: float = 0.95
-) -> int:
-    """Count how many messages in the deque are similar to the given text."""
-    return sum(1 for m in dq if is_similar(normalized, m.normalized_text, threshold))
-
-
 async def handle_duplicate_spam(
     update: Update, context: ContextTypes.DEFAULT_TYPE
 ) -> None:
@@ -132,35 +126,47 @@ async def handle_duplicate_spam(
     dq = _get_recent_messages(context, group_config.group_id, user.id)
     _prune_old_messages(dq, group_config.duplicate_spam_window_seconds, now)
 
-    similar_count = count_similar_in_window(dq, normalized, group_config.duplicate_spam_similarity)
+    similar_messages = [
+        m for m in dq
+        if is_similar(normalized, m.normalized_text, group_config.duplicate_spam_similarity)
+    ]
 
-    dq.append(
-        RecentMessage(
-            timestamp=now,
-            normalized_text=normalized,
-            message_id=update.message.message_id,
-        )
+    current_message = RecentMessage(
+        timestamp=now,
+        normalized_text=normalized,
+        message_id=update.message.message_id,
     )
+    dq.append(current_message)
 
-    if similar_count < group_config.duplicate_spam_threshold - 1:
+    if len(similar_messages) < group_config.duplicate_spam_threshold - 1:
         return
 
-    total_count = similar_count + 1
+    total_count = len(similar_messages) + 1
     user_mention = get_user_mention(user)
 
     logger.info(
         f"Duplicate spam detected: user_id={user.id}, "
         f"group_id={group_config.group_id}, count={total_count}"
     )
 
-    try:
-        await update.message.delete()
-        logger.info(f"Deleted duplicate spam from user_id={user.id}")
-    except Exception:
-        logger.error(
-            f"Failed to delete duplicate spam: user_id={user.id}",
-            exc_info=True,
-        )
+    pending_deletes = [m for m in similar_messages if not m.delete_attempted]
+    pending_deletes.append(current_message)
+
+    for m in pending_deletes:
+        try:
+            await context.bot.delete_message(
+                chat_id=group_config.group_id, message_id=m.message_id
+            )
+            logger.info(
+                f"Deleted duplicate spam message_id={m.message_id} from user_id={user.id}"
+            )
+        except Exception:
+            logger.error(
+                f"Failed to delete duplicate spam message_id={m.message_id}: user_id={user.id}",
+                exc_info=True,
+            )
+        finally:
+            m.delete_attempted = True
 
     await _enforce_restriction(context, group_config, user, user_mention, total_count)
 

tests/test_duplicate_spam.py

@@ -13,7 +13,6 @@
     RecentMessage,
     _get_recent_messages,
     _prune_old_messages,
-    count_similar_in_window,
     handle_duplicate_spam,
     is_similar,
     normalize_text,
@@ -104,24 +103,6 @@ def test_empty_deque(self):
         assert len(dq) == 0
 
 
-class TestCountSimilarInWindow:
-    """Tests for the count_similar_in_window function."""
-
-    def test_counts_similar(self):
-        dq = deque([
-            RecentMessage(timestamp=datetime.now(UTC), normalized_text="spam message here", message_id=1),
-            RecentMessage(timestamp=datetime.now(UTC), normalized_text="spam message here", message_id=2),
-            RecentMessage(timestamp=datetime.now(UTC), normalized_text="different message", message_id=3),
-        ])
-        assert count_similar_in_window(dq, "spam message here") == 2
-
-    def test_no_similar(self):
-        dq = deque([
-            RecentMessage(timestamp=datetime.now(UTC), normalized_text="hello world foo bar", message_id=1),
-        ])
-        assert count_similar_in_window(dq, "completely different text here") == 0
-
-
 class TestGetRecentMessages:
     """Tests for the _get_recent_messages function."""
 
@@ -169,7 +150,6 @@ def mock_update(self):
         update.message.text = "Barangkali di sini ada yang sedang mencari kerja bisa menghubungi saya"
         update.message.caption = None
         update.message.message_id = 100
-        update.message.delete = AsyncMock()
         update.effective_chat = MagicMock(spec=Chat)
         update.effective_chat.id = -100
         return update
@@ -181,6 +161,7 @@ def mock_context(self):
         context.bot = MagicMock()
         context.bot.restrict_chat_member = AsyncMock()
         context.bot.send_message = AsyncMock()
+        context.bot.delete_message = AsyncMock()
         return context
 
     async def test_skips_no_message(self, mock_context, group_config):
@@ -291,7 +272,9 @@ async def test_second_message_triggers_restriction(self, mock_update, mock_conte
             with pytest.raises(ApplicationHandlerStop):
                 await handle_duplicate_spam(mock_update, mock_context)
 
-        mock_update.message.delete.assert_called_once()
+        assert mock_context.bot.delete_message.call_count == 2
+        deleted_ids = {c.kwargs["message_id"] for c in mock_context.bot.delete_message.call_args_list}
+        assert deleted_ids == {99, 100}
         mock_context.bot.restrict_chat_member.assert_called_once()
         mock_context.bot.send_message.assert_called_once()
 
@@ -309,7 +292,7 @@ async def test_uses_caption_when_no_text(self, mock_update, mock_context, group_
             with pytest.raises(ApplicationHandlerStop):
                 await handle_duplicate_spam(mock_update, mock_context)
 
-        mock_update.message.delete.assert_called_once()
+        assert mock_context.bot.delete_message.call_count == 2
 
     async def test_expired_messages_not_counted(self, mock_update, mock_context, group_config):
         old = datetime.now(UTC) - timedelta(seconds=200)
@@ -322,7 +305,7 @@ async def test_expired_messages_not_counted(self, mock_update, mock_context, gro
         with patch("bot.handlers.duplicate_spam.get_group_config_for_update", return_value=group_config):
             await handle_duplicate_spam(mock_update, mock_context)
 
-        mock_update.message.delete.assert_not_called()
+        mock_context.bot.delete_message.assert_not_called()
 
     async def test_different_messages_not_counted(self, mock_update, mock_context, group_config):
         now = datetime.now(UTC)
@@ -335,10 +318,10 @@ async def test_different_messages_not_counted(self, mock_update, mock_context, g
         with patch("bot.handlers.duplicate_spam.get_group_config_for_update", return_value=group_config):
             await handle_duplicate_spam(mock_update, mock_context)
 
-        mock_update.message.delete.assert_not_called()
+        mock_context.bot.delete_message.assert_not_called()
 
     async def test_delete_failure_continues(self, mock_update, mock_context, group_config):
-        mock_update.message.delete = AsyncMock(side_effect=Exception("Delete failed"))
+        mock_context.bot.delete_message = AsyncMock(side_effect=Exception("Delete failed"))
         now = datetime.now(UTC)
         norm = normalize_text(mock_update.message.text)
         existing_dq = deque([
@@ -395,5 +378,33 @@ async def test_third_message_also_triggers(self, mock_update, mock_context, grou
             with pytest.raises(ApplicationHandlerStop):
                 await handle_duplicate_spam(mock_update, mock_context)
 
-        mock_update.message.delete.assert_called_once()
+        # Regression check: all prior duplicate messages must be deleted,
+        # not just the one that tripped the threshold.
+        assert mock_context.bot.delete_message.call_count == 3
+        deleted_ids = {c.kwargs["message_id"] for c in mock_context.bot.delete_message.call_args_list}
+        assert deleted_ids == {98, 99, 100}
         mock_context.bot.restrict_chat_member.assert_called_once()
+
+    async def test_does_not_retry_already_attempted_deletes(
+        self, mock_update, mock_context, group_config
+    ):
+        """Messages already deleted in a prior trigger must not be re-attempted."""
+        now = datetime.now(UTC)
+        norm = normalize_text(mock_update.message.text)
+        existing_dq = deque([
+            RecentMessage(
+                timestamp=now, normalized_text=norm, message_id=98, delete_attempted=True
+            ),
+            RecentMessage(
+                timestamp=now, normalized_text=norm, message_id=99, delete_attempted=True
+            ),
+        ])
+        mock_context.bot_data[RECENT_MESSAGES_KEY] = {(-100, 42): existing_dq}
+
+        with patch("bot.handlers.duplicate_spam.get_group_config_for_update", return_value=group_config):
+            with pytest.raises(ApplicationHandlerStop):
+                await handle_duplicate_spam(mock_update, mock_context)
+
+        mock_context.bot.delete_message.assert_called_once_with(
+            chat_id=-100, message_id=100
+        )