app.py

from langchain_community.document_loaders import TextLoader
import os 

loaders = []
folder_path = "Data"

for i in range(12):
  file_path = os.path.join(folder_path,"{}.txt".format(i))
  loaders.append(TextLoader(file_path))
  
docs = []
for loader in loaders:
    docs.extend(loader.load())

from langchain.vectorstores import Chroma
from langchain_community.embeddings import HuggingFaceInferenceAPIEmbeddings

HF_TOKEN = os.getenv("HF_TOKEN")
embeddings = HuggingFaceInferenceAPIEmbeddings(
    api_key=HF_TOKEN, model_name="sentence-transformers/all-mpnet-base-v2"
)

vectordb = Chroma.from_documents(
    documents=docs,
    embedding=embeddings
)

from langchain_community.llms import HuggingFaceHub

llm = HuggingFaceHub(
    repo_id="google/gemma-1.1-2b-it",
    task="text-generation",
    model_kwargs={
        "max_new_tokens": 7000,
        "top_k": 5,
        "temperature": 0.1,
        "repetition_penalty": 1.03,
    },
    huggingfacehub_api_token = HF_TOKEN
)

from langchain.prompts import PromptTemplate

template = """You are a Chatbot at a Restaurant. Help the customer pick the right dish to order. The items in the context are dishes. The field below the item is the cost of the dish. About is the description of the dish. Use the context below to answe the questions 
{context}
Question: {question}
Helpful Answer:"""
QA_CHAIN_PROMPT = PromptTemplate(input_variables=["context", "question"],template=template,)

from langchain.memory import ConversationBufferMemory
memory = ConversationBufferMemory(
    memory_key="chat_history",
    return_messages=True
)

from langchain.chains import ConversationalRetrievalChain

retriever = vectordb.as_retriever()
qa = ConversationalRetrievalChain.from_llm(
    llm,
    retriever=retriever,
    memory=memory,
)

from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.output_parsers import StrOutputParser
from langchain_core.runnables import RunnablePassthrough

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
)


from langchain_core.messages import AIMessage, HumanMessage

os.environ["LANGCHAIN_WANDB_TRACING"] = "true"
os.environ["WANDB_PROJECT"] = "Restaurant_ChatBot"

print("Welcome to the Restaurant. How can I help you today?")
chat_history = []

def predict(message):
  ai_msg = rag_chain.invoke({"question": message, "chat_history": chat_history})
  idx = ai_msg.find("Answer")
  chat_history.extend([HumanMessage(content=message), ai_msg])

  return ai_msg[idx:]