app.py

from typing import Annotated, TypedDict, Literal
from langchain_openai import ChatOpenAI
from langgraph.graph import StateGraph, START, END
from langgraph.graph.message import MessagesState
from langgraph.prebuilt import ToolNode
from langgraph.graph.message import add_messages

from langchain_core.messages import HumanMessage, AIMessage, SystemMessage
from langchain.schema.runnable.config import RunnableConfig
from langchain_community.tools.tavily_search import TavilySearchResults
from langchain.tools import Tool
from langchain_core.tools import tool

import chainlit as cl
from rag import create_rag_pipeline, add_urls_to_vectorstore

# Initialize RAG pipeline
rag_components = create_rag_pipeline(collection_name="london_events")

# Add some initial URLs to the vector store
urls = [
    "https://www.timeout.com/london/things-to-do-in-london-this-weekend",
    "https://www.timeout.com/london/london-events-in-march"
]
add_urls_to_vectorstore(
    rag_components["vector_store"],
    rag_components["text_splitter"],
    urls
)

class AgentState(TypedDict):
    messages: Annotated[list, add_messages]
    context: list  # Store retrieved context

# Create a retrieve tool
@tool
def retrieve_context(query: str) -> list[str]:
    """Searches the knowledge base for relevant information about events and activities. Use this when you need specific details about events."""
    return [doc.page_content for doc in rag_components["retriever"].get_relevant_documents(query)]

tavily_tool = TavilySearchResults(max_results=5)
tool_belt = [tavily_tool, retrieve_context]

llm = ChatOpenAI(model="gpt-4o-mini", temperature=0)
model = llm.bind_tools(tool_belt)

# Define system prompt
SYSTEM_PROMPT = SystemMessage(content="""
You are a helpful AI assistant that answers questions clearly and concisely.
If you don't know something, simply say you don't know.
Be engaging and professional in your responses.
Use the retrieve_context tool when you need specific information about events and activities.
Use the tavily_search tool for general web searches.
""")

def call_model(state: AgentState):
    messages = [SYSTEM_PROMPT] + state["messages"]
    response = model.invoke(messages)
    return {"messages": [response]}

tool_node = ToolNode(tool_belt)

# Simple flow control - always go to final
def should_continue(state):
  last_message = state["messages"][-1]

  if last_message.tool_calls:
    return "action"

  return END

# Create the graph
builder = StateGraph(AgentState)

# Remove retrieve node and modify graph structure
builder.add_node("agent", call_model)
builder.add_node("action", tool_node)

# Update edges
builder.set_entry_point("agent")
builder.add_conditional_edges(
    "agent",
    should_continue,
)
builder.add_edge("action", "agent")

# Compile the graph
compiled_graph = builder.compile()  # Changed variable name to be more explicit

# Export the graph for visualization
graph = compiled_graph  # This is what we'll import in the script

@cl.on_chat_start
async def on_chat_start():
    await cl.Message("Hello! I'm your chief joy officer, here to help you with finding fun things to do in London! You can ask me anything but I'm particularly good at finding events and activities. What can I help you with today?").send()

@cl.on_message
async def on_message(message: cl.Message):
    # Create configuration with thread ID
    config = {
        "configurable": {
            "thread_id": cl.context.session.id,
            "checkpoint_ns": "default_namespace"
        }
    }
    
    # Setup callback handler and final answer message
    cb = cl.LangchainCallbackHandler()
    final_answer = cl.Message(content="")
    await final_answer.send()
    
    loading_msg = None  # Initialize reference to loading message
    
    # Stream the response
    async for chunk in graph.astream(
        {"messages": [HumanMessage(content=message.content)], "context": []},
        config=RunnableConfig(callbacks=[cb], **config)
    ):
        for node, values in chunk.items():
            if node == "retrieve":
                loading_msg = cl.Message(content="🔍 Searching knowledge base...", author="System")
                await loading_msg.send()
            elif values.get("messages"):
                last_message = values["messages"][-1]
                # Check for tool calls in additional_kwargs
                if hasattr(last_message, "additional_kwargs") and last_message.additional_kwargs.get("tool_calls"):
                    tool_name = last_message.additional_kwargs["tool_calls"][0]["function"]["name"]
                    if loading_msg:
                        await loading_msg.remove()
                    loading_msg = cl.Message(
                        content=f"🔍 Using {tool_name}...",
                        author="Tool"
                    )
                    await loading_msg.send()
                # Only stream AI messages, skip tool outputs
                elif isinstance(last_message, AIMessage):
                    if loading_msg:
                        await loading_msg.remove()
                        loading_msg = None
                    await final_answer.stream_token(last_message.content)

    await final_answer.send()