chat: added 'update_messages()' function and test

chatmastermind/chat.py

@@ -386,3 +386,19 @@ class ChatDB(Chat):
         msgs = iter(messages if messages else self.messages)
         while (m := next(msgs, None)):
             m.to_file()
+
+    def update_messages(self, messages: list[Message], write: bool = True) -> None:
+        """
+        Update existing messages. A message is determined as 'existing' if a message with
+        the same base filename (i. e. 'file_path.name') is already in the list. Only accepts
+        existing messages.
+        """
+        if any(not message_in(m, self.messages) for m in messages):
+            raise ChatError("Can't update messages that are not in the internal list")
+        # remove old versions and add new ones
+        self.messages = [m for m in self.messages if not message_in(m, messages)]
+        self.messages += messages
+        self.sort()
+        # write the UPDATED messages if requested
+        if write:
+            self.write_messages(messages)