app.py

import nltk
nltk.download('punkt_tab')

import os
from dotenv import load_dotenv
import asyncio
from fastapi import FastAPI, Request, WebSocket, WebSocketDisconnect
from fastapi.responses import HTMLResponse
from fastapi.templating import Jinja2Templates
from fastapi.middleware.cors import CORSMiddleware
from langchain.chains import create_history_aware_retriever, create_retrieval_chain
from langchain.chains.combine_documents import create_stuff_documents_chain
from langchain_community.chat_message_histories import ChatMessageHistory
from langchain.schema import BaseChatMessageHistory
from langchain.prompts.chat import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.runnables import RunnableWithMessageHistory
from pinecone import Pinecone
from pinecone_text.sparse import BM25Encoder
from langchain_community.embeddings import OpenAIEmbeddings
from langchain_community.retrievers import PineconeHybridSearchRetriever
from langchain.retrievers import ContextualCompressionRetriever
from langchain_community.chat_models import ChatOpenAI
from langchain.retrievers.document_compressors import CrossEncoderReranker
from langchain_community.cross_encoders import HuggingFaceCrossEncoder
from langchain.prompts import PromptTemplate
import re
from langchain_huggingface import HuggingFaceEmbeddings

# Load environment variables
load_dotenv(".env")
USER_AGENT = os.getenv("USER_AGENT")
OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
SECRET_KEY = os.getenv("SECRET_KEY")
PINECONE_API_KEY = os.getenv("PINECONE_API_KEY")
SESSION_ID_DEFAULT = "abc123"

# Set environment variables
os.environ['USER_AGENT'] = USER_AGENT
os.environ["OPENAI_API_KEY"] = OPENAI_API_KEY
os.environ["TOKENIZERS_PARALLELISM"] = 'true'

# Initialize FastAPI app and CORS
app = FastAPI()
origins = ["*"]  # Adjust as needed

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

templates = Jinja2Templates(directory="templates")

# Function to initialize Pinecone connection
def initialize_pinecone(index_name: str):
    try:
        pc = Pinecone(api_key=PINECONE_API_KEY)
        return pc.Index(index_name)
    except Exception as e:
        print(f"Error initializing Pinecone: {e}")
        raise

##################################################
##          Change down here
##################################################

# Initialize Pinecone index and BM25 encoder
pinecone_index = initialize_pinecone("updated-mbzuai-policies")
bm25 = BM25Encoder().load("./mbzuai-policies.json")

##################################################
##################################################

# Initialize models and retriever
embed_model = HuggingFaceEmbeddings(model_name="jinaai/jina-embeddings-v3", model_kwargs={"trust_remote_code":True})

retriever = PineconeHybridSearchRetriever(
    embeddings=embed_model, 
    sparse_encoder=bm25, 
    index=pinecone_index, 
    top_k=20, 
    alpha=0.5,
)

# Initialize LLM
llm = ChatOpenAI(temperature=0, model_name="gpt-4o-mini", max_tokens=512)

# Initialize Reranker
model = HuggingFaceCrossEncoder(model_name="BAAI/bge-reranker-base")
compressor = CrossEncoderReranker(model=model, top_n=10)

compression_retriever = ContextualCompressionRetriever(
    base_compressor=compressor, base_retriever=retriever
)

# Contextualization prompt and retriever
contextualize_q_system_prompt = """Given a chat history and the latest user question \
which might reference context in the chat history, formulate a standalone question \
which can be understood without the chat history. Do NOT answer the question, \
just reformulate it if needed and otherwise return it as is.
"""
contextualize_q_prompt = ChatPromptTemplate.from_messages(
    [
        ("system", contextualize_q_system_prompt),
        MessagesPlaceholder("chat_history"),
        ("human", "{input}")
    ]
)
history_aware_retriever = create_history_aware_retriever(llm, compression_retriever, contextualize_q_prompt)

# QA system prompt and chain
qa_system_prompt = """ You are a highly skilled information retrieval assistant. Use the following context to answer questions effectively. 
If you don't know the answer, state that you don't know. 
Your answer should be in {language} language. 

When responding to queries, follow these guidelines:

1. Provide Clear Answers: 
   - Based on the language of the question, you have to answer in that language. E.g., if the question is in English, then answer in English; if the question is in Arabic, you should answer in Arabic.
   - Ensure the response directly addresses the query with accurate and relevant information.
   - Do not give long answers. Provide detailed but concise responses.

2. Formatting for Readability: 
   - Provide the entire response in proper markdown format.
   - Use structured Markdown elements such as headings, subheadings, lists, tables, and links.
   - Use emphasis on headings, important texts, and phrases.

3. Proper Citations:
   - ALWAYS USE INLINE CITATIONS with embedded source URLs where users can verify information or explore further. 
   - The inline citations should be in the format [[1]], [[2]], etc., in the response with links to reference sources.
   - AT THE END OF THE RESPONSE, LIST OUT THE CITATIONS WITH THEIR SOURCES. If there are multiple citations with same source url then only mention that single source url for all of those.

FOLLOW ALL THE GIVEN INSTRUCTIONS, FAILURE TO DO SO WILL RESULT IN THE TERMINATION OF THE CHAT.
{context}
"""
qa_prompt = ChatPromptTemplate.from_messages(
    [
        ("system", qa_system_prompt),
        MessagesPlaceholder("chat_history"),
        ("human", "{input}")
    ]
)

document_prompt = PromptTemplate(input_variables=["page_content", "source"], template="{page_content} \n\n Source: {source}")
question_answer_chain = create_stuff_documents_chain(llm, qa_prompt, document_prompt=document_prompt)

# Retrieval and Generative (RAG) Chain
rag_chain = create_retrieval_chain(history_aware_retriever, question_answer_chain)

# Chat message history storage
store = {}

def get_session_history(session_id: str) -> BaseChatMessageHistory:
    if session_id not in store:
        store[session_id] = ChatMessageHistory()
    return store[session_id]

# Conversational RAG chain with message history
conversational_rag_chain = RunnableWithMessageHistory(
    rag_chain,
    get_session_history,
    input_messages_key="input",
    history_messages_key="chat_history",
    language_message_key="language",
    output_messages_key="answer",
)

# WebSocket endpoint with streaming
@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    print(f"Client connected: {websocket.client}")
    session_id = None
    try:
        while True:
            data = await websocket.receive_json()
            question = data.get('question')
            language = data.get('language')
            if "en" in language:
                language = "English"
            else:
                language = "Arabic"
            session_id = data.get('session_id', SESSION_ID_DEFAULT)
            # Process the question
            try:
                # Define an async generator for streaming
                async def stream_response():
                    complete_response = ""
                    context = {}
                    async for chunk in conversational_rag_chain.astream(
                        {"input": question, 'language': language},
                        config={"configurable": {"session_id": session_id}}
                    ):
                        if "context" in chunk:
                            context = chunk['context']
                        # Send each chunk to the client
                        if "answer" in chunk:
                            complete_response += chunk['answer']
                            await websocket.send_json({'response': chunk['answer']})

                await stream_response()
            except Exception as e:
                print(traceback.format_exc())
                print(f"Error during message handling: {e}")
                await websocket.send_json({'response': "Something went wrong, Please try again." + str(e)})
    except WebSocketDisconnect:
        print(f"Client disconnected: {websocket.client}")
        if session_id:
            store.pop(session_id, None)

# Home route
@app.get("/", response_class=HTMLResponse)
async def read_index(request: Request):
    return templates.TemplateResponse("chat.html", {"request": request})