app.py

import os
import streamlit as st
from dotenv import load_dotenv
from PyPDF2 import PdfReader
from langchain_community.llms import llamacpp
from langchain_community.embeddings import HuggingFaceEmbeddings
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.callbacks import CallbackManager, StreamingStdOutCallbackHandler
from langchain.vectorstores import Chroma
from langchain.chat_models import ChatOpenAI
from langchain_community.chat_message_histories.streamlit import StreamlitChatMessageHistory
from langchain.prompts import PromptTemplate,SystemMessagePromptTemplate,ChatPromptTemplate
from langchain.chains.combine_documents import create_stuff_documents_chain
from langchain.chains import create_history_aware_retriever, create_retrieval_chain, ConversationalRetrievalChain
from langchain.text_splitter import TokenTextSplitter,RecursiveCharacterTextSplitter
from langchain_core.runnables.history import RunnableWithMessageHistory
from langchain_community.document_loaders.directory import DirectoryLoader
from langchain.document_loaders import PyPDFLoader
from htmlTemplates import css, bot_template, user_template
from langchain.memory import ConversationBufferMemory
from langchain.chains import ConversationalRetrievalChain
from langchain_core.output_parsers import StrOutputParser
from langchain_core.runnables import RunnablePassthrough
from langchain import hub






lang_api_key = os.getenv("lang_api_key")

os.environ["LANGCHAIN_TRACING_V2"] = "true"
os.environ["LANGCHAIN_ENDPOINT"] = "https://api.langchain.plus"
os.environ["LANGCHAIN_API_KEY"] = lang_api_key
os.environ["LANGCHAIN_PROJECT"] = "Chat with multiple PDFs"


def get_pdf_text(pdf_docs):
    text = ""
    for pdf in pdf_docs:
        pdf_reader = PdfReader(pdf)
        for page in pdf_reader.pages:
            text += page.extract_text()
    return text    

def get_text_chunks(text):
    text_splitter = RecursiveCharacterTextSplitter.from_tiktoken_encoder(
        chunk_size=250, chunk_overlap=50,
        separators=["\n \n \n", "\n \n", "\n1", "(?<=\. )", " ", ""],
    )
    chunks = text_splitter.split_text(text)
    return chunks

def get_vectorstore(text_chunks):
    model_name = "Alibaba-NLP/gte-base-en-v1.5"
    model_kwargs = {'device': 'cpu',
                   "trust_remote_code" : 'True'}
    encode_kwargs = {'normalize_embeddings': True}
    embeddings = HuggingFaceEmbeddings(
        model_name=model_name,
        model_kwargs=model_kwargs,
        encode_kwargs=encode_kwargs
    )
    vectorstore = Chroma.from_texts(
        texts=text_chunks, embedding=embeddings, persist_directory="docs/chroma/")
    return vectorstore   



def get_conversation_chain(vectorstore):
    
    callback_manager = CallbackManager([StreamingStdOutCallbackHandler()])

    
    llm = llamacpp.LlamaCpp(
            model_path="qwen2-0_5b-instruct-q8_0.gguf",
            n_gpu_layers=0,
            temperature=0.1,
            top_p = 0.9,
            n_ctx=20000,
            n_batch=2000,
            max_tokens = 300,
            repeat_penalty=1.9,
            last_n_tokens_size = 300,
            
            #callback_manager=callback_manager,
            verbose=False,
            )

    

    retriever = vectorstore.as_retriever(search_type='mmr', k=7)

    
    
    
    prompt = hub.pull("rlm/rag-prompt")
    rag_chain = ({"context": retriever} | prompt  | llm | StrOutputParser(),return_source_documents = True)


    return rag_chain



         
    
        
 
     

          



def main():
    st.set_page_config(page_title="Chat with multiple PDFs", page_icon=":books:")
    st.write(css, unsafe_allow_html=True)

    st.header("Chat with multiple PDFs :books:")

    


    if user_question := st.text_input("Ask a question about your documents:"):
        handle_userinput(user_question)
    
   
    with st.sidebar:
        st.subheader("Your documents")
        pdf_docs = st.file_uploader(
            "Upload your PDFs here and click on 'Process'", accept_multiple_files=True)
        if st.button("Process"):
            with st.spinner("Processing"):
                # get pdf text
                raw_text = get_pdf_text(pdf_docs)

                # get the text chunks
                text_chunks = get_text_chunks(raw_text)

                # create vector store
                vectorstore = get_vectorstore(text_chunks)

                # create conversation chain
                st.session_state.conversation = get_conversation_chain(
                    vectorstore)

    
    

        



    
    
    

def handle_userinput(user_question ):
    
    if "chat_history" not in st.session_state:
        st.session_state["chat_history"] = [
        {"role": "assistant", "content": "Hi, I'm a Q&A chatbot who is based on your imported pdf documents  . How can I help you?"}
    ]
    
    
    st.session_state.chat_history.append({"role": "user", "content": user_question})
    
    
    retriever = st.session_state.conversation.retriever()
    docs = retriever.invoke(user_question)
    
        
    
    doc_txt = [doc.page_content for doc in docs]
    
    # Invoke conversation chain
    response = st.session_state.conversation.invoke({"question": user_question})
    st.session_state.chat_history.append({"role": "assistant", "content": response})

    for i, message in enumerate(st.session_state.chat_history):
        if i % 2 == 0:
            st.write(user_template.replace(
                "{{MSG}}", message['content']), unsafe_allow_html=True) 
        else:
            st.write(bot_template.replace(
                "{{MSG}}", message['content']), unsafe_allow_html=True)

    st.subheader("Your documents")
        
    for doc in docs:
        st.write(f"Document: {doc}")

            

if __name__ == '__main__':
    main()