agent.py

import os
from langchain_google_genai import ChatGoogleGenerativeAI
from langgraph.graph import START, StateGraph, MessagesState
from langgraph.prebuilt import tools_condition
from langgraph.prebuilt import ToolNode
from langchain_core.messages import SystemMessage, HumanMessage
from tools import *

tools = [add, substract, multiply, divide, web_search]

class AgentState(TypedDict):
    question: str

def assistant(state: AgentState):
    return {
        "answer": [chat_with_tools.invoke(state["question"])],
    }

def build_agent():
    llm = ChatGoogleGenerativeAI(model="gemini-2.0-flash", temperature=0)
    llm.bind_tools(tools)

    ## The graph
    builder = StateGraph(AgentState)
    
    # Define nodes: these do the work
    builder.add_node("assistant", assistant)
    builder.add_node("tools", ToolNode(tools))
    
    # Define edges: these determine how the control flow moves
    builder.add_edge(START, "assistant")
    builder.add_conditional_edges(
        "assistant",
        # If the latest message requires a tool, route to tools
        # Otherwise, provide a direct response
        tools_condition,
    )
    builder.add_edge("tools", "assistant")

    return builder.compile()