app.py

import gradio as gr

from langchain.chains import (
    ConversationalRetrievalChain,
    LLMChain,
    MapReduceDocumentsChain,
    ReduceDocumentsChain,
    StuffDocumentsChain,
)
from langchain.embeddings import OpenAIEmbeddings
from langchain.memory import ConversationBufferMemory
from langchain.prompts import PromptTemplate
from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain.vectorstores import Chroma
from langchain_community.chat_models import ChatOpenAI
from langchain_community.document_loaders import WebBaseLoader


def wait_for_summarization(url):
    return [(None, f"Please wait while I summarize the contents of {url}...")]


def load_page(url, api_key, history):
    global docs, summary, llm
    loader = WebBaseLoader(url)
    docs = loader.load()
    llm = ChatOpenAI(
        model_name="gpt-3.5-turbo-1106", temperature=0, openai_api_key=api_key
    )
    map_template = """The following is a set of snippets from a web page:
{docs}
Based on this list of snippets, please identify the main themes
Helpful Answer:"""
    map_prompt = PromptTemplate.from_template(map_template)
    map_chain = LLMChain(llm=llm, prompt=map_prompt)

    # Reduce

    reduce_template = """The following is set of summaries of a web page:
{docs}
Take these and distill it into a final, consolidated summary of the main themes.
Helpful Answer:"""
    reduce_prompt = PromptTemplate.from_template(reduce_template)
    reduce_chain = LLMChain(llm=llm, prompt=reduce_prompt)

    # Takes a list of documents, combines them into a single string, and passes this to an LLMChain
    combine_documents_chain = StuffDocumentsChain(
        llm_chain=reduce_chain, document_variable_name="docs"
    )

    # Combines and iteratively reduces the mapped documents
    reduce_documents_chain = ReduceDocumentsChain(
        # This is final chain that is called.
        combine_documents_chain=combine_documents_chain,
        # If documents exceed context for `StuffDocumentsChain`
        collapse_documents_chain=combine_documents_chain,
        # The maximum number of tokens to group documents into.
        token_max=4000,
    )
    # Combining documents by mapping a chain over them, then combining results
    map_reduce_chain = MapReduceDocumentsChain(
        # Map chain
        llm_chain=map_chain,
        # Reduce chain
        reduce_documents_chain=reduce_documents_chain,
        # The variable name in the llm_chain to put the documents in
        document_variable_name="docs",
        # Return the results of the map steps in the output
        return_intermediate_steps=False,
    )

    text_splitter = RecursiveCharacterTextSplitter.from_tiktoken_encoder(
        chunk_size=1000, chunk_overlap=0
    )
    split_docs = text_splitter.split_documents(docs)

    summary = map_reduce_chain.run(split_docs)
    return history + [(None, summary)]


def prepare_chat(api_key, history):
    global docs, summary, llm, qa
    text_splitter = RecursiveCharacterTextSplitter(chunk_size=512, chunk_overlap=128)
    documents = text_splitter.split_documents(docs)
    embeddings = OpenAIEmbeddings(openai_api_key=api_key)
    vectorstore = Chroma.from_documents(documents, embeddings)
    retriever = vectorstore.as_retriever(
        search_type="similarity", search_kwargs={"k": 6}
    )
    qa_prompt_template = (
        """As an AI assistant you help in answering questions about the contents of a web page.
The summary of the current web page is this:

"""
        + summary
        + """

Also, consider this additional context that may be relevant for the user's question:

{context}

Please answer following question: {question}"""
    )

    qa_prompt = PromptTemplate(
        template=qa_prompt_template, input_variables=["context", "question"]
    )

    memory = ConversationBufferMemory(
        memory_key="chat_history", return_messages=True, output_key="answer"
    )
    qa = ConversationalRetrievalChain.from_llm(
        llm=llm,
        memory=memory,
        retriever=retriever,
        combine_docs_chain_kwargs={"prompt": qa_prompt},
    )
    return history + [(None, "You can now ask me specific questions about the page.")]


def chatbot_function(message, history):
    global qa
    return "", history + [(message, qa.run(message))]


def build_demo():
    with gr.Blocks(theme=gr.themes.Default()) as demo:
        with gr.Row() as config_row:
            with gr.Column():
                api_key_box = gr.Textbox(
                    show_label=False,
                    placeholder="OpenAI API Key",
                    container=False,
                    autofocus=True,
                )
                url_box = gr.Textbox(
                    show_label=False,
                    placeholder="URL",
                    container=False,
                )
                load_btn = gr.Button(value="Load", variant="primary")
        with gr.Row(visible=False) as chat_row:
            with gr.Column():
                with gr.Row():
                    chatbot = gr.Chatbot(
                        elem_id="chatbot",
                        label="Web Chat",
                        height=550,
                    )
                with gr.Row(visible=False) as inputs_row:
                    with gr.Column(scale=8):
                        text_box = gr.Textbox(
                            show_label=False,
                            placeholder="Enter text and press ENTER",
                            autofocus=True,
                            container=False,
                        )
                    with gr.Column(scale=1, min_width=50):
                        submit_btn = gr.Button(
                            value="Send",
                            variant="primary",
                        )

        load_btn.click(
            lambda: gr.update(visible=False),
            outputs=[config_row],
        ).then(
            lambda: gr.update(visible=True),
            outputs=[chat_row],
        ).then(
            wait_for_summarization,
            inputs=[url_box],
            outputs=[chatbot],
        ).then(
            load_page,
            inputs=[url_box, api_key_box, chatbot],
            outputs=[chatbot],
        ).then(
            prepare_chat,
            inputs=[api_key_box, chatbot],
            outputs=[chatbot],
        ).then(
            lambda: gr.update(visible=True),
            outputs=[inputs_row],
        )

        text_box.submit(
            chatbot_function,
            [text_box, chatbot],
            [text_box, chatbot],
        )
        submit_btn.click(
            chatbot_function,
            [text_box, chatbot],
            [text_box, chatbot],
        )

    return demo


if __name__ == "__main__":
    demo = build_demo()
    demo.launch()