app.py

import chainlit as cl
import os
from dotenv import load_dotenv
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.runnables.config import RunnableConfig
from langchain_openai import ChatOpenAI

load_dotenv()
openai_api_key = os.getenv("OPENAI_API_KEY")

@cl.action_callback("hide_button")
async def on_action(action):
    await cl.Message(content=f"Hiding the button").send()
    await action.remove()

@cl.action_callback("show_text")
async def on_action(action):
    cl.user_session.set("language", "english")
    await cl.Message(content="The button was clicked and this text was shown").send()

@cl.action_callback("english")
async def on_action(action):
    cl.user_session.set("language", "english")
    await cl.Message(content="Responses from the Chatbot will be in English").send()

@cl.action_callback("icelandic")
async def on_action(action):
    cl.user_session.set("language", "icelandic")
    await cl.Message(content="Responses from the Chatbot will be in Icelandic").send()

user_template = """
        Question:
        {question}

        Language:
        {language}
    """

system_template = """
    You are a helpful assistant who always speaks in a pleasant tone!
    Do your best to answer the question succinctly and truthfully.
    Think through your answers carefully.
    Respond in the language provided below. If no language is provided, use Italian.
""" 

#############################################
### On Chat Start (Session Start) Section ###
#############################################
@cl.on_chat_start
async def on_chat_start():
    # create a chain
    chat_prompt = ChatPromptTemplate.from_messages([
        ("system", system_template),
        ("human", user_template)
    ])
    chat_model = ChatOpenAI(model="gpt-4o-mini")
    simple_chain = chat_prompt | chat_model
    cl.user_session.set("chain", simple_chain)

    response = await cl.AskActionMessage(
        content="Do you want to see the buttons?",
        actions=[
            cl.Action(name="yes", value="yes", label="✅ Yes"),
            cl.Action(name="no", value="no", label="❌ No"),
        ],
    ).send()
    if response and response.get("value") == "yes":
        actions = [
            cl.Action(name="hide_button", value="hide-button", description="Hide this button"),
            cl.Action(name="show_text", value="show_text", description="Show text")
        ]

        await cl.Message(content="Different actions", actions=actions).send()
    else: 
        await cl.Message(content="No buttons for you").send()
    
    await cl.Message(content="Lets see how to change the language of the responses from the LLM").send()

    actions = [
        cl.Action(name="english", value="english", description="English"),
        cl.Action(name="icelandic", value="icelandic", description="Icelandic")
    ]

    await cl.Message(content="Languages", actions=actions).send()
    
    await cl.Message(content="Ask the chatbot a question. Then click the Icelandic button and ask again.").send()


@cl.on_message
async def main(message: cl.Message):
    chain = cl.user_session.get("chain")
    language = cl.user_session.get("language", "english")
    question = message.content

    msg = cl.Message(content="")
    # handle streaming of LLM responses 
    async for chunk in chain.astream(
        {"question": question, "language": language},
        config=RunnableConfig(callbacks=[cl.LangchainCallbackHandler()]),
    ):
        await msg.stream_token(chunk.content)

    await msg.send()