app.py

import os
import streamlit as st
import pandas as pd
import matplotlib.pyplot as plt
from langchain_community.tools.tavily_search import TavilySearchResults
from langchain_openai import ChatOpenAI
from langgraph.graph import MessagesState
from langgraph.graph import START, StateGraph
from langgraph.prebuilt import tools_condition
from langgraph.prebuilt import ToolNode
from langchain_core.messages import HumanMessage, SystemMessage
import tempfile

# ------------------- Environment Variable Setup -------------------
# Fetch API keys from environment variables
openai_api_key = os.getenv("OPENAI_API_KEY")
tavily_api_key = os.getenv("TAVILY_API_KEY")

# Verify if API keys are set
if not openai_api_key:
    raise ValueError("Missing required environment variable: OPENAI_API_KEY")
if not tavily_api_key:
    raise ValueError("Missing required environment variable: TAVILY_API_KEY")

# ------------------- Tool Definitions -------------------
# Tavily Search Tool
tavily_tool = TavilySearchResults(max_results=5)

def multiply(a: int, b: int) -> int:
    """Multiply two numbers."""
    return a * b

def add(a: int, b: int) -> int:
    """Add two numbers."""
    return a + b

def divide(a: int, b: int) -> float:
    """Divide two numbers."""
    if b == 0:
        raise ValueError("Division by zero is not allowed.")
    return a / b

# Combine tools
tools = [add, multiply, divide, tavily_tool]

# ------------------- LLM and System Message Setup -------------------
llm = ChatOpenAI(model="gpt-4o-mini")
llm_with_tools = llm.bind_tools(tools, parallel_tool_calls=False)
sys_msg = SystemMessage(content="You are a helpful assistant tasked with performing arithmetic and search on a set of inputs.")

# ------------------- LangGraph Workflow -------------------
def assistant(state: MessagesState):
    """Assistant node to invoke LLM with tools."""
    return {"messages": [llm_with_tools.invoke([sys_msg] + state["messages"])]}

# Define the graph
app_graph = StateGraph(MessagesState)
app_graph.add_node("assistant", assistant)
app_graph.add_node("tools", ToolNode(tools))
app_graph.add_edge(START, "assistant")
app_graph.add_conditional_edges("assistant", tools_condition)
app_graph.add_edge("tools", "assistant")
react_graph = app_graph.compile()

# Save graph visualization as an image
with tempfile.NamedTemporaryFile(suffix=".png", delete=False) as tmpfile:
    graph = react_graph.get_graph(xray=True)
    tmpfile.write(graph.draw_mermaid_png())  # Write binary image data to file
    graph_image_path = tmpfile.name

# ------------------- Streamlit Interface -------------------
st.title("ReAct Agent for Arithmetic Ops & Web Search")

# Display the workflow graph
#st.header("LangGraph Workflow Visualization")
st.image(graph_image_path, caption="Workflow Visualization")

# Prompt user for inputs
user_question = st.text_area("Enter your question:",
                             placeholder="Example: 'Add 3 and 4. Multiply the result by 2. Divide it by 5.'")

if st.button("Submit"):
    if not user_question.strip():
        st.error("Please enter a valid question.")
        st.stop()
    
    st.info("Processing your question...")
    messages = [HumanMessage(content=user_question)]
    response = react_graph.invoke({"messages": messages})
    
    # Display results step-by-step
    st.subheader("Response:")
    for m in response['messages']:
        if hasattr(m, "content") and m.content:  # Display human and assistant messages
            st.write("**AI Message:**", m.content)
        if hasattr(m, "tool_calls") and m.tool_calls:  # Display tool call steps
            for tool_call in m.tool_calls:
                st.write(f"**Tool Call:** `{tool_call['name']}`")
                st.json(tool_call['args'])  # Display tool arguments in JSON
                if "output" in tool_call:  # Handle tool outputs if available
                    st.write("**Tool Output:**", tool_call['output'])

    st.success("Processing complete!")

# Example Placeholder Suggestions
st.sidebar.subheader("Example Questions")
st.sidebar.write("- Add 3 and 4. Multiply the result by 2. Divide it by 5.")
st.sidebar.write("- Tell me how many centuries Virat Kohli scored.")
st.sidebar.write("- Search for the tallest building in the world.")

st.sidebar.title("References")
st.sidebar.markdown("1. [LangGraph ReAct Agents](https://github.com/aritrasen87/LLM_RAG_Model_Deployment/blob/main/LangGraph_9_ReAct_Agents.ipynb)")