app.py

import os
from typing import TypedDict, Annotated
from dotenv import load_dotenv
from langgraph.graph.message import add_messages
from langchain_core.messages import AnyMessage, HumanMessage, SystemMessage
from langgraph.prebuilt import ToolNode
from langgraph.graph import START, StateGraph
from langgraph.prebuilt import tools_condition
from langgraph.checkpoint.memory import MemorySaver
from langchain_huggingface import HuggingFaceEndpoint, ChatHuggingFace
from langfuse.callback import CallbackHandler
from retriever import guest_info_tool
from tools import search_tool, weather_info_tool, hub_stats_tool

import gradio as gr

load_dotenv()

# Initialize Langfuse
langfuse_handler = CallbackHandler(
    secret_key=os.getenv("LANGFUSE_SECRET_KEY"),
    public_key=os.getenv("LANGFUSE_PUBLIC_KEY"),
    host=os.getenv("LANGFUSE_HOST"),
)

# Generate the chat interface, including the tools
llm = HuggingFaceEndpoint(
    repo_id="Qwen/Qwen2.5-Coder-32B-Instruct",
    huggingfacehub_api_token=os.getenv("HUGGINGFACEHUB_API_TOKEN")
)
chat = ChatHuggingFace(llm=llm, verbose=True)
tools = [guest_info_tool, search_tool, weather_info_tool, hub_stats_tool]
chat_with_tools = chat.bind_tools(tools)


# Define the AgentState structure
class AgentState(TypedDict):
    messages: Annotated[list[AnyMessage], add_messages]


def assistant(state: AgentState):
    # Define the system prompt (this is not part of the conversation history)
    system_message = SystemMessage(content="""You are Alfred, a helpful and sophisticated assistant.

Your capabilities:
- Answer questions using your knowledge
- Search the web for recent or factual information using the DuckDuckGoSearchResults tool
- Retrieve information about guests using the guest_info_tool
- Use weather_info_tool to give information about the weather

Guidelines:
- Be concise, polite and helpful
- When you don't know something, use the appropriate tool rather than guessing
- For guest information requests, always use the guest_info_tool first
- For factual or current information, use the search tool
- Present information in a clear, organized manner

Always think carefully about which tool is most appropriate for the user's request.
""")
    # Call the agent with the system prompt and conversation history (state messages)
    assistant_response = chat_with_tools.invoke([system_message] + state.get("messages"))
    # Return the updated conversation state including the new assistant response
    return {"messages": state.get("messages") + [assistant_response]}

# Build the graph
builder = StateGraph(AgentState)
builder.add_node("assistant", assistant)
builder.add_node("tools", ToolNode(tools))
builder.add_edge(START, "assistant")
builder.add_conditional_edges("assistant", tools_condition)
builder.add_edge("tools", "assistant")
checkpointer = MemorySaver()
alfred = builder.compile(checkpointer=checkpointer)
config = {"configurable": {"thread_id": "1"}, "callbacks": [langfuse_handler]}

# Gradio chat function
def chat_fn(message, history):
    state = {"messages": [HumanMessage(content=message)]}
    result = alfred.invoke(state, config)
    return result["messages"][-1].content

# Launch Gradio interface
interface = gr.ChatInterface(fn=chat_fn,type="messages")
interface.launch()