Post shift change notifications to the schedule channel (#21) (#22)

Slash command handlers (drop, pick, swap) were posting notifications to
command["channel_id"] — wherever the command was run. If someone ran
/oncall drop from a DM, the notification went there instead of the
schedule channel. Pickup buttons didn't have this problem because
body["channel"]["id"] is always the channel where the button lives.

Added SHIFT_CHANNEL_PARAM to the SlackBotFunction env vars, read it on
cold start, and route all slash command shift-change notifications to
the configured schedule channel.

Closes #21

src/app.py

@@ -78,7 +78,7 @@ def is_today(date_str: str) -> bool:
     return date_str == datetime.now(EASTERN).strftime("%Y-%m-%d")
 
 
-def create_app(bot_token: str, signing_secret: str) -> App:
+def create_app(bot_token: str, signing_secret: str, schedule_channel: str | None = None) -> App:
     app = App(
         token=bot_token,
         signing_secret=signing_secret,
@@ -110,11 +110,11 @@ def create_app(bot_token: str, signing_secret: str) -> App:
         elif text.startswith("register"):
             _handle_register(respond, schedule, user_id, text)
         elif text.startswith("pick"):
-            _handle_pick(respond, schedule, user_id, text, channel_id, client)
+            _handle_pick(respond, schedule, user_id, text, schedule_channel or channel_id, client)
         elif text.startswith("drop"):
-            _handle_drop(respond, schedule, user_id, text, channel_id, client)
+            _handle_drop(respond, schedule, user_id, text, schedule_channel or channel_id, client)
         elif text.startswith("swap"):
-            _handle_swap(respond, schedule, user_id, text, channel_id, client)
+            _handle_swap(respond, schedule, user_id, text, schedule_channel or channel_id, client)
         else:
             respond(text="Unknown command. Try `/oncall help`")
 

src/handler.py

@@ -28,8 +28,11 @@ def _get_handler() -> SlackRequestHandler:
         signing_secret = ssm.get_parameter(
             Name=os.environ["SLACK_SIGNING_SECRET_PARAM"], WithDecryption=True
         )["Parameter"]["Value"]
+        schedule_channel = ssm.get_parameter(
+            Name=os.environ["SHIFT_CHANNEL_PARAM"], WithDecryption=True
+        )["Parameter"]["Value"]
 
-        app = create_app(bot_token, signing_secret)
+        app = create_app(bot_token, signing_secret, schedule_channel=schedule_channel)
         _slack_handler = SlackRequestHandler(app=app)
     return _slack_handler
 

template.yaml

@@ -47,6 +47,7 @@ Resources:
           SHIFT_TABLE: !Ref ShiftTable
           SLACK_BOT_TOKEN_PARAM: /afterhours-shift-manager/slack-bot-token
           SLACK_SIGNING_SECRET_PARAM: /afterhours-shift-manager/slack-signing-secret
+          SHIFT_CHANNEL_PARAM: /afterhours-shift-manager/channel-id
           SCHEDULER_FUNCTION_NAME: !Ref SchedulerFunctionName
           TZ: !Ref Timezone
       Policies: