main.py

from fastapi import FastAPI
import os
from langchain.chat_models import ChatOpenAI
from langchain.prompts import PromptTemplate
from langchain.memory import ConversationBufferMemory
from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.output_parsers import StrOutputParser
from langchain_core.runnables import RunnablePassthrough
import os
from langchain_community.document_loaders import PyPDFLoader
import os
from langchain_text_splitters import RecursiveCharacterTextSplitter
from langchain_community.embeddings.sentence_transformer import (
    SentenceTransformerEmbeddings,
)
from langchain_chroma import Chroma
from sentence_transformers import SentenceTransformer
from langchain_core.messages import AIMessage, HumanMessage
from fastapi import FastAPI, Request, UploadFile, File

os.environ['HF_HOME'] = '/hug/cache/'
os.environ['TRANSFORMERS_CACHE'] = '/blabla/cache/'

app = FastAPI()

def predict(message, db):

    llm = ChatOpenAI(model_name="gpt-4o-mini", temperature=0)
    template = """You are a general purpose chatbot. Be friendly and kind. Help people answer their questions. Use the context below to answer the questions
    {context}
    Question: {question}
    Helpful Answer:"""
    QA_CHAIN_PROMPT = PromptTemplate(input_variables=["context", "question"],template=template,)
    memory = ConversationBufferMemory(
        memory_key="chat_history",
        return_messages=True
    )
        
    retriever = db.as_retriever(k=3)

    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(variable_name="chat_history"),
            ("human", "{question}"),
        ]
    )
    contextualize_q_chain = contextualize_q_prompt | llm | StrOutputParser()
    def contextualized_question(input: dict):
      if input.get("chat_history"):
          return contextualize_q_chain
      else:
          return input["question"]

    rag_chain = (
        RunnablePassthrough.assign(
            context=contextualized_question | retriever
        )
        | QA_CHAIN_PROMPT
        | llm
      )
    history = []
    ai_msg = rag_chain.invoke({"question": message, "chat_history": history})
    print(ai_msg)
    bot_response = ai_msg.content.strip()

    # Ensure history is correctly formatted as a list of tuples (user_message, bot_response)
    history.append((HumanMessage(content=message), AIMessage(content=bot_response)))

    docs = db.similarity_search(message,k=3)
    extra = "\n" + "*"*100 + "\n"
    additional_info = []
    for d in docs:
        citations = d.metadata["source"] + " pg." + str(d.metadata["page"])
        additional_info = d.page_content
        extra += citations + "\n" + additional_info + "\n" + "*"*100 + "\n"
    # Return the bot's response and the updated history
    return bot_response + extra

def upload_file(file_path):

    loaders = []
    print(file_path)
    loaders.append(PyPDFLoader(file_path))

    documents = []
    for loader in loaders:
        documents.extend(loader.load())

    text_splitter = RecursiveCharacterTextSplitter(chunk_size=512, chunk_overlap=16)
    docs = text_splitter.split_documents(documents)

    model = "thenlper/gte-large"
    embedding_function = SentenceTransformerEmbeddings(model_name=model)
    print(f"Model's maximum sequence length: {SentenceTransformer(model).max_seq_length}")
    collection_name = "Autism"
    persist_directory = "./chroma"
    print(len(docs))
    db = Chroma.from_documents(docs, embedding_function)
    print("Done Processing, you can query")

    return db

@app.get("/")
async def root():
 return {"Entvin":"Version 1.0 'First Draft'"}

@app.post("/UploadFile/")
def predicts(question: str, file: UploadFile = File(...)):
    contents =  file.file.read()
    with open(file.filename, 'wb') as f:
        f.write(contents)
    
    db = upload_file(file.filename)
    result = predict(question, db)
    return {"answer":result}