Building an OpenAI-Powered Slack Chatbot: A Step-by-Step Guide

import { NextRequest, NextResponse } from "next/server";
const { WebClient, LogLevel } = require("@slack/web-api");
import { ObjectId } from "mongodb";
import {
  encodeChat,
  encode,
  decode,
  isWithinTokenLimit,
} from 'gpt-tokenizer'
import moment from 'moment';


export async function POST(req: NextRequest) {
  try {

    let retryNum = req.headers.get('X-Slack-Retry-Num');
    //if retryNum is available then return the response with status 200
    if (retryNum) {
      return new NextResponse('', { status: 200 });
    }
    //read the incomming parameter from webhook
    let resData: any = await req.json();
    // return the challenge on first time verification
    if (resData.challenge) {
      return new NextResponse(JSON.stringify({ challenge: resData.challenge }), { status: 200 });
    }
    else {
      if (resData.event.type === 'app_mention') {

        // setImmediate(async () => {
        await writeInDataBase(resData);
        // });

        return new NextResponse('', { status: 200 });
      }
      else {
        //handle else part here.
      }
    }

  }
  catch (error: any) {
    console.log('error', error);
  }
}

// Asynchronous function to write data into the database
async function writeInDataBase(data: any) {

  // Define the token limit for different models
  const tokenLimit = [
    {
      model: "gpt-3.5-turbo",
      tokens: 15385,
    },
    {
      model: "gpt-4",
      tokens: 8000
    }
  ]

  let step = 1;

  try {
    // Extract the app ID and channel ID from the data
    const appId = data.api_app_id;
    const channelId = data.event.channel;

    // Connect to the database
    const db = (await clientPromise!)?.db();
    let slackCollection = db.collection('slack-app-details');

    // Find the app details in the database
    let appDetails: SlackAppData = await slackCollection.findOne({
      appId: appId,
    });

    // If app details are found
    if (appDetails) {
      // Extract the auth token, chat bot ID, and user ID from the app details
      const authOToken = appDetails.authOToken;
      const chatBotId = appDetails.chatBotId;
      const message = data.event.text.replace(/<@.*?>\s*\n?/, "");
      const userID = appDetails.userId;

      // Create a new Slack client with the auth token
      const client = new WebClient(authOToken, {
        // LogLevel can be imported and used to make debugging simpler
        logLevel: LogLevel.DEBUG,
      });

      // If the message is empty, return a message
      if (message.length === 0) {
        await client.chat.postMessage({
          channel: channelId,
          text: "I guess you sent me an empty message.",
          threadId: data.event.ts,
        });

        return new NextResponse('', { status: 200 });
      }
      else {
        // Send a POST request to the OpenAI API
        const responseOpenAI: any = await fetch(
          "https://api.openai.com/v1/chat/completions",
          {
            method: "POST",
            headers: {
              "Content-Type": "application/json",
              Authorization: `Bearer ${process.env.NEXT_PUBLIC_OPENAI_KEY}`,
            },
            body: JSON.stringify({
              model: userChatBotModel.model,
              temperature: userChatBotModel.temperature,
              top_p: 1,
              messages: [
                {
                  role: "system",
                  content: `Use the following pieces of context to answer the users question.
                  If you don't know the answer, just say that you don't know, don't try to make up an answer.
                  ----------------
                  context:
                  ${similaritySearchResults}
                  
                  Answer user query and include images write respect to each line if available`,
                },
                // ...messages,
                {
                  role: "user",
                  content: `Answer user query and include images in response if available in the given context 
                
                            query: ${message} `,
                },
              ],
            }),
          }
        );

        // Parse the response from OpenAI
        const openaiBody = JSON.parse(await responseOpenAI.text());

        // If the response from OpenAI contains content, post it to the Slack channel
        if (openaiBody.choices[0].message.content) {
          await client.chat.postMessage({
            channel: channelId,
            text: openaiBody.choices[0].message.content,
            thread_ts: data.event.ts,
          });
          return new NextResponse('', { status: 200 });

        }
        else {

        }
      }
    }
  }
  catch (error: any) {
    // If an error occurs with the OpenAI or Slack API, log the error
    console.log('error', error);
  }

}