langchain_client.py

import os

from langchain_openai import ChatOpenAI
from langchain_core.output_parsers import StrOutputParser
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_community.chat_message_histories import ChatMessageHistory
from langchain_core.chat_history import BaseChatMessageHistory
from langchain_core.runnables.history import RunnableWithMessageHistory

OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")

class LangchainClient:
    
    def __init__(self):
        self.llm = ChatOpenAI(
            openai_api_key=OPENAI_API_KEY,
            temperature=0,   
            model_name='gpt-4o'
            )
        self.store = {}
    
    def create_prompt(self):
        template_prompt = """You are a chatbot that can answer questions in English and Bahasa Indonesia.
                        answer using language from user, if user use bahasa indonesia answer in bahasa indonesia.
                        if user language is english answer in english"""

        prompt = ChatPromptTemplate.from_messages(
            [
                (
                    "system",
                    template_prompt,
                ),
                MessagesPlaceholder(variable_name="history"),
                ("human", "{question}"),
            ]
        )
        
        return prompt

    def get_session_history(self, session_id: str) -> BaseChatMessageHistory:
        if session_id not in self.store:
            self.store[session_id] = ChatMessageHistory()
        return self.store[session_id]
    
    def create_model(self):
        prompt = self.create_prompt()
        parser = StrOutputParser()
        conversation_chain = prompt | self.llm | parser
        conversation_chain_history = RunnableWithMessageHistory(
            conversation_chain,
            self.get_session_history,
            input_messages_key="question",
            history_messages_key="history",
        )
        return conversation_chain_history

    def invoke_llm(self, model, text):
        response = model.invoke(
            {"question": text},
            config={"configurable": {"session_id": "default"}}
            )
        return response