app.py

import os
import gradio as gr
from typing import List

from langchain.chat_models import init_chat_model
from langchain_huggingface import HuggingFaceEmbeddings
from langchain_chroma import Chroma

from langgraph.prebuilt import create_react_agent
from langgraph.checkpoint.memory import MemorySaver

from langchain_core.tools import tool
from langchain_core.documents import Document


os.environ["LANGCHAIN_TRACING_V2"] = "true"
os.environ["LANGSMITH_ENDPOINT"] = "https://api.smith.langchain.com"
os.environ["LANGCHAIN_API_KEY"] = os.environ.get("LANGCHAIN_API_KEY", "")
os.environ["LANGCHAIN_PROJECT"] = "KlagRAG"
os.environ["GOOGLE_API_KEY"] = os.environ.get("GOOGLE_API_KEY", "")

# Load embeddings and vectorstore
embeddings_model = HuggingFaceEmbeddings(model_name="sentence-transformers/all-mpnet-base-v2")
vector_store = Chroma(persist_directory="./chroma_db", embedding_function=embeddings_model)

def format_doc_with_source(docs: List[Document]):
    documents_separator = '\n\n[SEP]\n\n'
    return documents_separator.join([f"SOURCE LINK: {doc.metadata['source']}\nCONTENT: {doc.page_content}" for doc in docs])

@tool(response_format="content_and_artifact")
def retrieve(query: str):
    """Retrieve information related to a query from University's website."""
    retrieved_docs = vector_store.similarity_search(query, k=3)
    serialized = format_doc_with_source(retrieved_docs)
    return serialized, retrieved_docs

memory = MemorySaver()

llm = init_chat_model("gemini-2.0-flash", model_provider="google_genai")

# Agent executor
system_prompt = "You are an assistant for question-answering tasks in university. " \
  "You help future students, current students and university staff to find relevant information. " \
  "Use the following pieces of retrieved context to answer the question. " \
  "If you don't know the answer, just say that you don't know. " \
  "Keep the answer concise and structured. Always provide a links to the sources you used and refer to." \
  "You can ask user questions to give more specific answers, if needed."
agent_executor = create_react_agent(llm, [retrieve], checkpointer=memory, prompt=system_prompt)


def respond(user_input):
    response = agent_executor.invoke({"input": user_input})
    return response.get("output", "No response.")

demo = gr.ChatInterface(
    respond,
)

if __name__ == "__main__":
    demo.launch()