Harrison/file chat history (#3198)

Co-authored-by: Young Lee <joybro201@gmail.com>

langchain/memory/chat_message_histories/__init__.py

@@ -1,4 +1,5 @@
 from langchain.memory.chat_message_histories.dynamodb import DynamoDBChatMessageHistory
+from langchain.memory.chat_message_histories.file import FileChatMessageHistory
 from langchain.memory.chat_message_histories.postgres import PostgresChatMessageHistory
 from langchain.memory.chat_message_histories.redis import RedisChatMessageHistory
 
@@ -6,4 +7,5 @@ __all__ = [
     "DynamoDBChatMessageHistory",
     "RedisChatMessageHistory",
     "PostgresChatMessageHistory",
+    "FileChatMessageHistory",
 ]

langchain/memory/chat_message_histories/file.py

@@ -0,0 +1,53 @@
+import json
+import logging
+from pathlib import Path
+from typing import List
+
+from langchain.schema import (
+    AIMessage,
+    BaseChatMessageHistory,
+    BaseMessage,
+    HumanMessage,
+    messages_from_dict,
+    messages_to_dict,
+)
+
+logger = logging.getLogger(__name__)
+
+
+class FileChatMessageHistory(BaseChatMessageHistory):
+    """
+    Chat message history that stores history in a local file.
+
+    Args:
+        file_path: path of the local file to store the messages.
+    """
+
+    def __init__(self, file_path: str):
+        self.file_path = Path(file_path)
+        if not self.file_path.exists():
+            self.file_path.touch()
+            self.file_path.write_text(json.dumps([]))
+
+    @property
+    def messages(self) -> List[BaseMessage]:  # type: ignore
+        """Retrieve the messages from the local file"""
+        items = json.loads(self.file_path.read_text())
+        messages = messages_from_dict(items)
+        return messages
+
+    def add_user_message(self, message: str) -> None:
+        self.append(HumanMessage(content=message))
+
+    def add_ai_message(self, message: str) -> None:
+        self.append(AIMessage(content=message))
+
+    def append(self, message: BaseMessage) -> None:
+        """Append the message to the record in the local file"""
+        messages = messages_to_dict(self.messages)
+        messages.append(messages_to_dict([message])[0])
+        self.file_path.write_text(json.dumps(messages))
+
+    def clear(self) -> None:
+        """Clear session memory from the local file"""
+        self.file_path.write_text(json.dumps([]))

tests/unit_tests/memory/__init__.py

@@ -0,0 +1 @@
+"""Unit tests for memory module"""

tests/unit_tests/memory/chat_message_histories/__init__.py

@@ -0,0 +1 @@
+"""Unit tests for chat_message_history modules"""

tests/unit_tests/memory/chat_message_histories/test_file.py

@@ -0,0 +1,71 @@
+import tempfile
+from pathlib import Path
+from typing import Generator
+
+import pytest
+
+from langchain.memory.chat_message_histories import FileChatMessageHistory
+from langchain.schema import AIMessage, HumanMessage
+
+
+@pytest.fixture
+def file_chat_message_history() -> Generator[FileChatMessageHistory, None, None]:
+    with tempfile.TemporaryDirectory() as temp_dir:
+        file_path = Path(temp_dir) / "test_chat_history.json"
+        file_chat_message_history = FileChatMessageHistory(str(file_path))
+        yield file_chat_message_history
+
+
+def test_add_messages(file_chat_message_history: FileChatMessageHistory) -> None:
+    file_chat_message_history.add_user_message("Hello!")
+    file_chat_message_history.add_ai_message("Hi there!")
+
+    messages = file_chat_message_history.messages
+    assert len(messages) == 2
+    assert isinstance(messages[0], HumanMessage)
+    assert isinstance(messages[1], AIMessage)
+    assert messages[0].content == "Hello!"
+    assert messages[1].content == "Hi there!"
+
+
+def test_clear_messages(file_chat_message_history: FileChatMessageHistory) -> None:
+    file_chat_message_history.add_user_message("Hello!")
+    file_chat_message_history.add_ai_message("Hi there!")
+
+    file_chat_message_history.clear()
+    messages = file_chat_message_history.messages
+    assert len(messages) == 0
+
+
+def test_multiple_sessions(file_chat_message_history: FileChatMessageHistory) -> None:
+    # First session
+    file_chat_message_history.add_user_message("Hello, AI!")
+    file_chat_message_history.add_ai_message("Hello, how can I help you?")
+    file_chat_message_history.add_user_message("Tell me a joke.")
+    file_chat_message_history.add_ai_message(
+        "Why did the chicken cross the road? To get to the other side!"
+    )
+
+    # Ensure the messages are added correctly in the first session
+    messages = file_chat_message_history.messages
+    assert len(messages) == 4
+    assert messages[0].content == "Hello, AI!"
+    assert messages[1].content == "Hello, how can I help you?"
+    assert messages[2].content == "Tell me a joke."
+    expected_content = "Why did the chicken cross the road? To get to the other side!"
+    assert messages[3].content == expected_content
+
+    # Second session (reinitialize FileChatMessageHistory)
+    file_path = file_chat_message_history.file_path
+    second_session_chat_message_history = FileChatMessageHistory(
+        file_path=str(file_path)
+    )
+
+    # Ensure the history is maintained in the second session
+    messages = second_session_chat_message_history.messages
+    assert len(messages) == 4
+    assert messages[0].content == "Hello, AI!"
+    assert messages[1].content == "Hello, how can I help you?"
+    assert messages[2].content == "Tell me a joke."
+    expected_content = "Why did the chicken cross the road? To get to the other side!"
+    assert messages[3].content == expected_content