TechnologyJanuary 23, 2024

Building a Wikipedia Chatbot Using Astra DB, LangChain, and Vercel

Carter Rabasa
Carter RabasaDeveloper relations
Building a Wikipedia Chatbot Using Astra DB, LangChain, and Vercel
@dataclass_json
@dataclass
class ChunkedArticleMetadataOnly:
    _id: str
    article_metadata: ArticleMetadata
    chunks_metadata: dict[str, ChunkMetadata] = field(default_factory=dict)
    suggested_question_chunks: list[Chunk] = field(default_factory=list)
METADATA_COLLECTION.find_one_and_replace(
            filter={"_id": metadata._id},
            replacement=metadata.to_dict(),
            options={"upsert": True}
        )
resp = METADATA_COLLECTION.find_one(filter={"_id": new_metadata._id})
prev_metadata_doc = resp["data"]["document"]
prev_metadata = ChunkedArticleMetadataOnly.from_dict(prev_metadata_doc)
"use client";
import { useChat, useCompletion } from 'ai/react';
import { Message } from 'ai';
const { append, messages, isLoading, input, handleInputChange, handleSubmit } = useChat();
const handleSend = (e) => {
  handleSubmit(e, { options: { body: { useRag, llm, similarityMetric}}});
}
  const [suggestions, setSuggestions] = useState<PromptSuggestion[]>([]);

  const { complete } = useCompletion({
    onFinish: (prompt, completion) => {
      const parsed = JSON.parse(completion);
      const argsObj = JSON.parse(parsed?.function_call.arguments);
      const questions = argsObj.questions;

      const questionsArr: PromptSuggestion[] = [];
      questions.forEach(q => {
        questionsArr.push(q);
      });
      setSuggestions(questionsArr);
    }
  });

  useEffect(() => {
    complete('')
  }, []);
import { AstraDB } from "@datastax/astra-db-ts";
import { OpenAIStream, StreamingTextResponse } from "ai";
import OpenAI from "openai";
import type { ChatCompletionCreateParams } from 'openai/resources/chat';
const {
  ASTRA_DB_APPLICATION_TOKEN,
  ASTRA_DB_ENDPOINT,
  ASTRA_DB_SUGGESTIONS_COLLECTION,
  OPENAI_API_KEY,
} = process.env;

const astraDb = new AstraDB(ASTRA_DB_APPLICATION_TOKEN, ASTRA_DB_ENDPOINT);

const openai = new OpenAI({
  apiKey: OPENAI_API_KEY,
});
const suggestionsCollection = await astraDb.collection(ASTRA_DB_SUGGESTIONS_COLLECTION);

const suggestionsDoc = await suggestionsCollection.findOne(
  {
    _id: "recent_articles"
  },
  {
    projection: {
      "recent_articles.metadata.title" : 1,
      "recent_articles.suggested_chunks.content" : 1,
  },
});
const docMap = suggestionsDoc.recent_articles.map(article => {
        return {
          pageTitle: article.metadata.title,
          content: article.suggested_chunks.map(chunk => chunk.content)
        }
      });

      docContext = JSON.stringify(docMap);
const response = await openai.chat.completions.create({
  model: "gpt-3.5-turbo-16k",
  stream: true,
  temperature: 1.5,
  messages: [{
    role: "user",
    content: `You are an assistant who creates sample questions to ask a chatbot. 
      Given the context below of the most recently added data to the most popular pages 
      on Wikipedia come up with 4 suggested questions. Only write no more than one 
      question per page and keep them to less than 12 words each. Do not label which page 
      the question is for/from.
      START CONTEXT
      ${docContext}
      END CONTEXT
    `,
    }],
  functions
});
const functions: ChatCompletionCreateParams.Function[] = [{
  name: 'get_suggestion_and_category',
  description: 'Prints a suggested question and the category it belongs to.',
  parameters: {
    type: 'object',
    properties: {
      questions: {
        type: 'array',
        description: 'The suggested questions and their categories.',
        items: {
          type: 'object',
          properties: {
            category: {
              type: 'string',
              enum: ['history', 'science', 'sports', 'technology', 'arts', 'culture',
                'geography', 'entertainment', 'politics', 'business', 'health'],
              description: 'The category of the suggested question.',
            },
            question: {
              type: 'string',
              description: 'The suggested question.',
            },
          },
        },
      },
    },
    required: ['questions'],
  },
}]; 
import { CohereEmbeddings } from "@langchain/cohere";
import { Document } from "@langchain/core/documents";
import { 
  RunnableBranch,
  RunnableLambda,
  RunnableMap, 
  RunnableSequence
} from "@langchain/core/runnables";
import { StringOutputParser } from "@langchain/core/output_parsers";
import { PromptTemplate } from "langchain/prompts";
import {
  AstraDBVectorStore,
  AstraLibArgs,
} from "@langchain/community/vectorstores/astradb";
import { ChatOpenAI } from "langchain/chat_models/openai";
import { StreamingTextResponse, Message } from "ai";
const questionTemplate = `You are an AI assistant answering questions about anything 
  from Wikipedia the context will provide you with the most relevant data from wikipedia 
  including the pages title, url, and page content.
  If referencing the text/context refer to it as Wikipedia.
  At the end of the response add one markdown link using the format: [Title](URL) and 
  replace the title and url with the associated title and url of the more relavant page  
  from the context
  This link will not be shown to the user so do not mention it.
  The max links you can include is 1, do not provide any other references or annotations.
  if the context is empty, answer it to the best of your ability. If you cannot find the    
  answer user's question in the context, reply with "I'm sorry, I'm only allowed to 
  answer questions related to the top 1,000 Wikipedia pages".
<context>
  {context}
</context>
 
QUESTION: {question}  
`;
const prompt = PromptTemplate.fromTemplate(questionTemplate);
const {messages, llm } = await req.json();
const previousMessages = messages.slice(0, -1);
const latestMessage = messages[messages?.length - 1]?.content;

const embeddings = new CohereEmbeddings({
  apiKey: COHERE_API_KEY,
  inputType: "search_query",
  model: "embed-english-v3.0",
});

const chatModel = new ChatOpenAI({
  temperature: 0.5,
  openAIApiKey: OPENAI_API_KEY,
  modelName: llm ?? "gpt-4",
  streaming: true,
}); 
const astraConfig: AstraLibArgs = {
  token: ASTRA_DB_APPLICATION_TOKEN,
  endpoint: ASTRA_DB_ENDPOINT,
  collection: “article_embeddings”,
  contentKey: “content”
};

const vectorStore = new AstraDBVectorStore(embeddings, astraConfig);

await vectorStore.initialize();
 
const retriever = vectorStore.asRetriever(10);
const chain = RunnableSequence.from([
  condenseChatBranch,
  mapQuestionAndContext,
  prompt,
  chatModel,
  new StringOutputParser(),
]).withConfig({ runName: "chatChain"});

const stream = await chain.stream({
  chat_history: formatVercelMessages(previousMessages),
  question: latestMessage, 
});
const hasChatHistoryCheck = RunnableLambda.from(
  (input: ChainInut) => input.chat_history.length > 0
);

const chatHistoryQuestionChain = RunnableSequence.from([
  {
    question: (input: ChainInut) => input.question,
    chat_history: (input: ChainInut) => input.chat_history,
  },
  condenseQuestionPrompt,
  chatModel,
  new StringOutputParser(),
]).withConfig({ runName: "chatHistoryQuestionChain"});

const noChatHistoryQuestionChain = RunnableLambda.from(
  (input: ChainInut) => input.question
).withConfig({ runName: "noChatHistoryQuestionChain"});


const condenseChatBranch = RunnableBranch.from([
  [hasChatHistoryCheck, chatHistoryQuestionChain],
   noChatHistoryQuestionChain,
 ]).withConfig({ runName: "condenseChatBranch"}); 
const condenseQuestionTemplate = `Given the following chat history and a follow up
 question, If the follow up question references previous parts of the chat rephrase the
 follow up question to be a standalone question if not use the follow up question as the
 standalone question.

<chat_history>
  {chat_history}
</chat_history>

Follow Up Question: {question}
Standalone question:`;

const condenseQuestionPrompt = PromptTemplate.fromTemplate(
  condenseQuestionTemplate,
);
const combineDocumentsFn = (docs: Document[]) => {
  const serializedDocs = docs.map((doc) => `Title: ${doc.metadata.title}
URL: ${doc.metadata.url}
Content: ${doc.pageContent}`);

  return serializedDocs.join("\n\n");
};

const retrieverChain = retriever.pipe(combineDocumentsFn).withConfig({ runName:
 "retrieverChain"});

const mapQuestionAndContext = RunnableMap.from({
  question: (input: string) => input,
  context: retrieverChain
}).withConfig({ runName: "mapQuestionAndContext"});
return new StreamingTextResponse(stream);
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