Load previous conversation

src/llm_chat/chat.py

@@ -80,15 +80,41 @@ class Chat:
         self,
         settings: OpenAISettings | None = None,
         context: list[Message] = [],
+        initial_system_messages: bool = True,
     ) -> None:
         self._settings = settings
         self.conversation = Conversation(
-            messages=INITIAL_SYSTEM_MESSAGES + context,
+            messages=INITIAL_SYSTEM_MESSAGES + context
+            if initial_system_messages
+            else context,
             model=self.settings.model,
             temperature=self.settings.temperature,
         )
         self._start_time = datetime.now(tz=ZoneInfo("UTC"))
 
+    @classmethod
+    def load(
+        cls, path: Path, api_key: str | None = None, history_dir: Path | None = None
+    ) -> ChatProtocol:
+        """Load a chat from a file."""
+        with path.open() as f:
+            conversation = Conversation.model_validate_json(f.read())
+        args = {
+            "model": conversation.model,
+            "temperature": conversation.temperature,
+        }
+        if api_key is not None:
+            args["api_key"] = api_key
+        if history_dir is not None:
+            args["history_dir"] = history_dir
+
+        settings = OpenAISettings(**args)
+        return cls(
+            settings=settings,
+            context=conversation.messages,
+            initial_system_messages=False,
+        )
+
     @property
     def settings(self) -> OpenAISettings:
         """Get OpenAI chat settings."""