bot.js

// Init requires and imports
require('dotenv').config()
const express = require("express");
const mongoose = require("mongoose");
const cron = require("node-cron");
const axios = require("axios").default;
const {sendMessage, sendMessages, sendMessagesToDiffClients, checkPincodeValidity} = require("./utils");
const app = express();

app.use(express.urlencoded({extended: false}));

// Common data for query URL
const today = new Date();
const day = today.getDate();
const month = ((today.getMonth() < 10) ? "0" : "") + (today.getMonth() + 1);
const year = today.getFullYear();
const DATE = `${day}-${month}-${year}`;
const CONFIG = {
  headers: {
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36"
  }
}

// Create MongoDB schema and connect with MongoDB Atlas
const taskSchema = new mongoose.Schema({pinCode: Number, clientNumber: Number});
const Task = mongoose.model('Task', taskSchema);
mongoose.connect(process.env.DB_URI, {useNewUrlParser: true, useUnifiedTopology: true}).catch(err => console.log(err));

// Root route
app.get("/", (req, res) => {
  res.send("Roses are red, Violets are blue, There's nothing to see here, What will you do?");
});

// Starts the bot
app.listen(process.env.PORT || 8000, () => {
  console.log("Server started.");
});

// Handles incoming messages
app.post("/incoming", async (req) => {

  // Parse user query
  // Key Body & From stores client's message & WhatsApp number respectively
  const query = req.body.Body.split(' ');
  let action = query[0];
  let pinCode = query[1];
  let clientNumber = req.body.From.split(':')[1];

  let isValidPincode = checkPincodeValidity(pinCode);

  // Create new tracking task
  if (action === "track" && isValidPincode === true) {

    // Create new task
    const taskInfo = new Task({pinCode: pinCode, clientNumber: clientNumber});

    // Save the task
    const afterSave = await taskInfo.save();
    if (afterSave === taskInfo)
      sendMessage(`Tracking empty vaccination slots for *${pinCode}*`, clientNumber);
  }

  // Handle checking
  else if (action === "check" && isValidPincode === true) {
    const URL = `https://cdn-api.co-vin.in/api/v2/appointment/sessions/public/calendarByPin?pincode=${pinCode}&date=${DATE}`

    // Send GET request to CoWIN API and process it
    let response = await axios.get(URL, CONFIG);
    try {
      // Cherrypick data, create the message and store them
      let data = response.data.centers;
      let messages = data.map((center) => {
        let sessionsInfo = ``;
        center.sessions.forEach((session, index) => {
          let msg = `\n${index + 1}. ${session.date}:\nDose 1 = ${session.available_capacity_dose1}\nDose 2 = ${session.available_capacity_dose2}\nMin Age = ${session.min_age_limit}\n`;
          sessionsInfo = sessionsInfo + msg;
        });
        return `\`\`\`Name: ${center.name}\nFee Type: ${center.fee_type}\nSessions: \n${sessionsInfo}\`\`\``;
      })
      // Send the stored messages
      sendMessages(messages, clientNumber);
    } catch (err) {
      console.log(err);
    }
  }

  // Remove a tracking task for a given clientNumber & pinCode
  else if (action === "stop" && isValidPincode === true) {
    await Task.deleteOne({pinCode: pinCode, clientNumber: clientNumber});
    sendMessage(`Tracking for ${pinCode} stopped`, clientNumber)
  }

  // Handle invalid input
  else
    sendMessage(`I can't understand your query 🙁. Please check that you typed it correctly`, clientNumber);
});

// Cron task to check availability for saved tasks
// */30 * * * * -> Every 30th minute
cron.schedule('*/30 * * * *', () => {
  console.log("Searching...");
  Task.find({}, (err, tasks) => {
    if (!err) {
      tasks.forEach(async (task) => {
        let messagesForDiffClients = [];
        let URL = `https://cdn-api.co-vin.in/api/v2/appointment/sessions/public/calendarByPin?pincode=${task.pinCode}&date=${DATE}`
        let response = await axios.get(URL, CONFIG)
        try {
          // If any center in the region can administer a dose, inform client
          let data = response.data.centers;
          data.every(center => {
            let regionCanServe = false;
            center.sessions.every(session => {
              if (session.available_capacity_dose1 !== 0 || session.available_capacity_dose2 !== 0) {
                regionCanServe = true;
                return false;
              }
              return true;
            })
            if (regionCanServe === true) {
              var msg = `A session may be available at ${task.pinCode}. Please visit https://www.cowin.gov.in/home for more details`;
              messagesForDiffClients.push({
                message: msg,
                clientNumber: task.clientNumber
              });
              return false;
            }
            return true;
          })
          sendMessagesToDiffClients(messagesForDiffClients);
        } catch (err) {
          console.log(err);
        }
      })
    }
    console.log("Search ended!")
  })
})