app.py

import streamlit as st
from langchain_core.messages import HumanMessage, AIMessage

def get_llm(provider, config):
    """Initialize the selected LLM with configuration"""
    try:
        if provider == "OpenAI":
            from langchain_openai import ChatOpenAI
            return ChatOpenAI(
                api_key=config.get("api_key"),
                model=config.get("model_name", "gpt-3.5-turbo")
            )
        elif provider == "Anthropic":
            from langchain_anthropic import ChatAnthropic
            return ChatAnthropic(
                api_key=config.get("api_key"),
                model=config.get("model_name", "claude-3-sonnet-20240229")
            )
        elif provider == "Gemini":
            from langchain_google_genai import ChatGoogleGenerativeAI
            return ChatGoogleGenerativeAI(
                google_api_key=config.get("api_key"),
                model=config.get("model_name", "gemini-pro")
            )
        elif provider == "DeepSeek":
            from langchain_openai import ChatOpenAI
            return ChatOpenAI(
                api_key=config.get("api_key"),
                base_url=config.get("base_url", "https://api.deepseek.com/v1"),
                model=config.get("model_name", "deepseek-chat")
            )
        elif provider == "Ollama":
            from langchain_community.chat_models import ChatOllama
            return ChatOllama(
                base_url=config.get("base_url", "http://localhost:11434"),
                model=config.get("model_name", "llama2")
            )
        else:
            raise ValueError("Selected provider is not supported")
    except ImportError as e:
        st.error(f"Missing required package: {e}")
        return None

# Initialize chat history
if "messages" not in st.session_state:
    st.session_state.messages = []

# Sidebar configuration
with st.sidebar:
    st.title("⚙️ LLM Configuration")
    provider = st.selectbox(
        "Select Provider",
        ["OpenAI", "Anthropic", "Gemini", "DeepSeek", "Ollama"]
    )

    config = {}
    if provider in ["OpenAI", "Anthropic", "Gemini", "DeepSeek"]:
        config["api_key"] = st.text_input(
            f"{provider} API Key", 
            type="password",
            help=f"Get your API key from {provider}'s platform"
        )
        if provider == "DeepSeek":
            config["base_url"] = st.text_input(
                "API Base URL",
                "https://api.deepseek.com/v1"
            )
        
        # Model name input with provider-specific defaults
        default_models = {
            "OpenAI": "gpt-3.5-turbo",
            "Anthropic": "claude-3-sonnet-20240229",
            "Gemini": "gemini-pro",
            "DeepSeek": "deepseek-chat"
        }
        config["model_name"] = st.text_input(
            "Model Name", 
            value=default_models.get(provider, "")
        )
    elif provider == "Ollama":
        config["model_name"] = st.text_input(
            "Model Name", 
            value="llama2",
            help="Make sure the model is available in your Ollama instance"
        )
        config["base_url"] = st.text_input(
            "Ollama Base URL",
            "http://localhost:11434",
            help="URL where your Ollama server is running"
        )

# Main chat interface
st.title("💬 LLM Chat Interface")

# Display chat messages
for message in st.session_state.messages:
    with st.chat_message(message["role"]):
        st.markdown(message["content"])

# Handle user input
if prompt := st.chat_input("Type your message..."):
    # Add user message to chat history
    st.session_state.messages.append({"role": "user", "content": prompt})
    
    # Display user message
    with st.chat_message("user"):
        st.markdown(prompt)

    # Generate response
    with st.spinner("Thinking..."):
        try:
            llm = get_llm(provider, config)
            if llm is None:
                st.error("Failed to initialize LLM. Check configuration.")
                st.stop()

            # Convert messages to LangChain format
            lc_messages = [
                HumanMessage(content=msg["content"]) if msg["role"] == "user"
                else AIMessage(content=msg["content"])
                for msg in st.session_state.messages
            ]

            # Get LLM response
            response = llm.invoke(lc_messages)
            
            # Display and store assistant response
            with st.chat_message("assistant"):
                st.markdown(response.content)
            st.session_state.messages.append(
                {"role": "assistant", "content": response.content}
            )
        except Exception as e:
            st.error(f"Error generating response: {str(e)}")