chatbot.py

from typing import TypedDict, Annotated
from langchain_core.messages import BaseMessage, SystemMessage
from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph import StateGraph, START, END
from langgraph.graph.message import add_messages
from langgraph.prebuilt import ToolNode, tools_condition
from langchain_openai import ChatOpenAI
from dotenv import load_dotenv

from tools import (
    create_rag_tool,
    arxiv_search,
    wikipedia_search,
    tavily_search,
)

load_dotenv()

# ===============================
# SYSTEM PROMPT
# ===============================
SYSTEM_PROMPT = SystemMessage(
    content="""
You are an AI assistant using Retrieval-Augmented Generation.

If a document is uploaded, you MUST answer using it.
If no relevant info exists, clearly say so.
Never hallucinate document content.
"""
)

# ===============================
# STATE
# ===============================
class ChatState(TypedDict):
    messages: Annotated[list[BaseMessage], add_messages]


# ===============================
# LLM
# ===============================
llm = ChatOpenAI(
    model="gpt-4.1-nano",
    temperature=0.3,
    streaming=True
)

# ===============================
# TOOLS
# ===============================
rag_tool = create_rag_tool()

tools = [
    rag_tool,
    wikipedia_search,
    arxiv_search,
    tavily_search,
]

llm = llm.bind_tools(tools)
tool_node = ToolNode(tools)


# ===============================
# CHAT NODE
# ===============================
def chatbot(state: ChatState):
    messages = [SYSTEM_PROMPT] + state["messages"]
    response = llm.invoke(messages)
    return {"messages": [response]}


# ===============================
# GRAPH
# ===============================
memory = MemorySaver()
graph = StateGraph(ChatState)

graph.add_node("chat", chatbot)
graph.add_node("tools", tool_node)

graph.add_edge(START, "chat")
graph.add_conditional_edges("chat", tools_condition)
graph.add_edge("tools", "chat")
graph.add_edge("chat", END)

app = graph.compile(checkpointer=memory)