app.py

import os
import logging
import openai
import gradio as gr
from langchain_community.document_loaders import TextLoader
from langchain_community.vectorstores import FAISS
from langchain_community.embeddings import HuggingFaceEmbeddings
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain_openai import OpenAIEmbeddings, ChatOpenAI
from langchain.chains import ConversationalRetrievalChain
from langchain.memory import ConversationBufferMemory
from langchain.schema import Document

# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# Environment setup
openai_api_key = os.getenv('OPENAI_API_KEY')
if not openai_api_key:
    raise ValueError("OPENAI_API_KEY environment variable is not set")

# Constants
DB_NAME = 'vector_db'
MODEL = "gpt-3.5-turbo"

# Load vector DB
if not os.path.exists(DB_NAME):
    logger.error(f"Vector database '{DB_NAME}' not found")
    raise FileNotFoundError(f"Vector database '{DB_NAME}' not found in the current directory")

db = FAISS.load_local(DB_NAME, HuggingFaceEmbeddings(model_name="intfloat/e5-base"), allow_dangerous_deserialization=True)

# Load LLM
llm = ChatOpenAI(
    model_name=MODEL, 
    temperature=0, 
    api_key=openai_api_key
)

# Memory for chat history
memory = ConversationBufferMemory(
    memory_key='chat_history',
    return_messages=True,
    output_key='answer'
)

# Retriever and chain
retriever = db.as_retriever(search_kwargs={"k": 3})
chain = ConversationalRetrievalChain.from_llm(
    llm=llm,
    retriever=retriever,
    memory=memory,
    return_source_documents=True
)

# Gradio interface function
def chat(question, history):
    result = chain.invoke({"question": question})
    return result["answer"]

# Gradio UI
view = gr.ChatInterface(fn=chat, type='messages', theme=gr.themes.Soft())
view.launch()