conversational_bot.py

import gradio as gr
from langchain_ollama import ChatOllama
from langgraph.graph import StateGraph, START, END
from langgraph.graph.message import MessagesState
from langgraph.checkpoint.memory import MemorySaver
from langchain_core.messages import (
    convert_to_openai_messages,
    SystemMessage,
    HumanMessage,
)

def create_conversation_graph():
    """
    Create a conversational graph with a memory saver.
    """
    memory = MemorySaver()

    llm = ChatOllama(model="gemma3:4b", temperature=0)

    sys_msg = SystemMessage(content="You are a helpful assistant tasked with performing arithmetic on a set of inputs.")

    def assistant(state: MessagesState) -> MessagesState:
        return {"messages": [llm.invoke([sys_msg] + state["messages"])]}

    builder = StateGraph(MessagesState)

    builder.add_node("assistant", assistant)
    builder.add_edge(START, "assistant")
    builder.add_edge("assistant", END)

    graph = builder.compile(checkpointer=memory)
    return graph


def create_chat_interface():
    """
    Create and configure the chat interface with the conversation graph.
    """
    graph = create_conversation_graph()

    # Specify a thread id
    thread_id = "123"
    config = {"configurable": {"thread_id": thread_id}}

    def chat_with_assistant(message, history):
        """
        Chat with the assistant using the conversational graph.
        """
        # Create a MessagesState with a HumanMessage
        messages_state = MessagesState(messages=[HumanMessage(content=message)])

        # Invoke the graph with the properly formatted input
        response = graph.invoke(messages_state, config)

        # Extract the last message from the response's messages list
        ai_message = response["messages"][-1]

        # Return just the content of the AI message
        return convert_to_openai_messages(ai_message)


    demo = gr.ChatInterface(
        fn=chat_with_assistant,
        type="messages",
        title="Conversational Bot",
        description="Ask anything you want",
        examples=["Hello", "What is your name?", "What is the weather in Tokyo?"],
    )
    return demo

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