To be squashed

zulip/integrations/bridge_with_slack/run-slack-bridge

@@ -5,7 +5,7 @@ import os
 import sys
 import threading
 import traceback
-from typing import Any, Callable, Dict, Tuple
+from typing import Any, Callable, Dict, Union
 
 import bridge_with_slack_config
 import slack_sdk
@@ -18,23 +18,25 @@ ZULIP_MESSAGE_TEMPLATE = "**{username}**: {message}"
 SLACK_MESSAGE_TEMPLATE = "<{username}> {message}"
 
 
-def check_zulip_message_validity(
+def get_zulip_message_slack_channel(
     msg: Dict[str, Any], zulip_to_slack_map: Dict[str, Any], bot_email: str
-) -> Tuple[bool, str]:
+) -> Union[str, None]:
     is_a_stream = msg["type"] == "stream"
     if not is_a_stream:
-        return False, ""
+        return None
 
     stream_name = msg["display_recipient"]
     topic_name = msg["subject"]
-    stream_topic = stream_name + "-" + topic_name
+    stream_topic = f"{stream_name}-{topic_name}"
     if stream_topic not in zulip_to_slack_map:
-        return False, ""
+        return None
 
     # We do this to identify the messages generated from Slack -> Zulip
     # and we make sure we don't forward it again to the Slack.
-    not_from_zulip_bot = msg["sender_email"] != bot_email
-    return not_from_zulip_bot, zulip_to_slack_map[stream_topic]
+    from_zulip_bot = msg["sender_email"] == bot_email
+    if from_zulip_bot:
+        return None
+    return zulip_to_slack_map[stream_topic]
 
 
 class SlackBridge:
@@ -43,9 +45,9 @@ class SlackBridge:
         self.zulip_config = config["zulip"]
         self.slack_config = config["slack"]
 
-        self.slack_to_zulip_map = dict(config["pairs"])
+        self.slack_to_zulip_map: Dict[str, Dict[str, str]] = config["pairs"]
         self.zulip_to_slack_map = {
-            z["stream"] + "-" + z["topic"]: s for s, z in config["pairs"].items()
+            f'{z["stream"]}-{z["topic"]}': s for s, z in config["pairs"].items()
         }
 
         # zulip-specific
@@ -77,10 +79,10 @@ class SlackBridge:
 
     def zulip_to_slack(self) -> Callable[[Dict[str, Any]], None]:
         def _zulip_to_slack(msg: Dict[str, Any]) -> None:
-            message_valid, slack_channel = check_zulip_message_validity(
+            slack_channel = get_zulip_message_slack_channel(
                 msg, self.zulip_to_slack_map, self.zulip_config["email"]
             )
-            if message_valid:
+            if slack_channel is not None:
                 self.wrap_slack_mention_with_bracket(msg)
                 slack_text = SLACK_MESSAGE_TEMPLATE.format(
                     username=msg["sender_full_name"], message=msg["content"]