bug: Integrate placeholder in create_message_box.

Author: sahith-ch

zulipterminal/ui_tools/utils.py

@@ -7,8 +7,8 @@
 import urwid
 
 from zulipterminal.api_types import Message
-from zulipterminal.ui_tools.messages import MessageBox
-
+from zulipterminal.ui_tools.messages import MessageBox,PlaceholderMessageBox
+from typing import List, Any
 
 def create_msg_box_list(
     model: Any,
@@ -23,7 +23,14 @@ def create_msg_box_list(
     if not model.narrow and messages is None:
         messages = list(model.index["all_msg_ids"])
     if messages is not None:
-        message_list = [model.index["messages"][id] for id in messages]
+        message_list = [model.index["messages"][id] for id in messages if id in model.index["messages"]]
+    else:
+        message_list = []
+    if not message_list:
+        placeholder = urwid.AttrMap(PlaceholderMessageBox("No messages here"), None, "msg_selected")
+        model.set_focus_in_current_narrow(0)
+        return [placeholder]
+
     message_list.sort(key=lambda msg: msg["timestamp"])
     w_list = []
     focus_msg = None
@@ -32,30 +39,29 @@ def create_msg_box_list(
     for msg in message_list:
         if is_unsubscribed_message(msg, model):
             continue
-        # Remove messages of muted topics / streams.
         if is_muted(msg, model):
             muted_msgs += 1
             if model.narrow == []:  # Don't show in 'All messages'.
                 continue
         msg_flag: Optional[str] = "unread"
         flags = msg.get("flags")
-        # update_messages sends messages with no flags
-        # but flags are set to [] when fetching old messages.
         if flags and ("read" in flags):
             msg_flag = None
-        elif focus_msg is None:
+        elif (focus_msg is None) and (last_msg is None):  # type: ignore[redundant-expr]
             focus_msg = message_list.index(msg) - muted_msgs
         if msg["id"] == focus_msg_id:
             focus_msg = message_list.index(msg) - muted_msgs
+        # Skip invalid last_msg from placeholder
+        if last_msg and "type" not in last_msg:
+            last_msg = None
         w_list.append(
             urwid.AttrMap(MessageBox(msg, model, last_msg), msg_flag, "msg_selected")
         )
         last_msg = msg
     if focus_msg is not None:
         model.set_focus_in_current_narrow(focus_msg)
-    return w_list
-
 
+    return w_list
 # The SIM114 warnings are ignored here since combining the branches would be less clear
 def is_muted(msg: Message, model: Any) -> bool:
     # PMs cannot be muted