app.py

import os
import gradio as gr
from langchain_openai import ChatOpenAI
from langchain_core.output_parsers import StrOutputParser
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.runnables import RunnablePassthrough, chain

def create_dynamic_chain(api_key):
    llm = ChatOpenAI(model="gpt-4o-mini", api_key=api_key)
    
    contextualize_prompt = ChatPromptTemplate.from_messages([
        ("system", "Convert the question into a standalone question given the chat history."),
        ("placeholder", "{chat_history}"),
        ("human", "{question}")
    ])
    
    contextualize_question = contextualize_prompt | llm | StrOutputParser()
    
    @chain
    def contextualize_if_needed(input_dict):
        if input_dict.get("chat_history"):
            return contextualize_question
        return RunnablePassthrough() | (lambda x: x["question"])
    
    return contextualize_if_needed

def process_message(message, history, api_key):
    if not api_key:
        return "", [{"role": "assistant", "content": "Please enter your OpenAI API key."}]
    
    try:
        chain = create_dynamic_chain(api_key)
        chat_history = [(msg["role"], msg["content"]) for msg in history]
        
        response = chain.invoke({
            "question": message,
            "chat_history": chat_history
        })
        
        history.append({"role": "user", "content": message})
        history.append({"role": "assistant", "content": response})
        
        return "", history
    except Exception as e:
        return "", history + [{"role": "assistant", "content": f"Error: {str(e)}"}]

with gr.Blocks() as demo:
    gr.Markdown("# Dynamic Chain Demo")
    
    api_key = gr.Textbox(
        label="OpenAI API Key",
        placeholder="Enter your OpenAI API key",
        type="password"
    )
    
    chatbot = gr.Chatbot(type="messages")
    msg = gr.Textbox(label="Message")
    clear = gr.ClearButton([msg, chatbot])
    
    msg.submit(
        process_message,
        inputs=[msg, chatbot, api_key],
        outputs=[msg, chatbot]
    )

if __name__ == "__main__":
    demo.launch()