DEV Community

loading...

Let's build Node.js based CLI - Track real time COVID-19 vaccination slots in India

Nabheet Madan
Technology Enthusiast
・8 min read

Why Build?

As we already know the whole world is suffering from COVID-19 and the vaccination's are going in full swing everywhere. Finding a slot is getting tougher in our country India as we have huge population to be vaccinated. Numerous times we have to go to CoWin site to search for a slot and slots are always full. It is pretty time consuming and irritating. Being a developer, I thought most of the time is usually spent by us in the terminal so why can't we have a basic terminal-based app to save time. So this post will help you in two ways

  1. Learn how to create Node.js based CLI's
  2. Get real time info about vaccination slots for your area.

In case you are someone who like to watch then read you can watch the same

Let's begin our initial set up!

Pre-requisite – We are assuming you have installed Node.js and npm,If not you can install from here

So as a first step lets initialize our project using command

npm init
Enter fullscreen mode Exit fullscreen mode

Enter the basic details as shown below.

Set Up Package.json

This will create package.json file in the folder cowinCLI. Next step is to create a bin folder which will have our index.js file containing our application.

bin folder

Open the index.js file and add the below mentioned first line. This actually tells the interpreter that whatever code runs below this will be handled by the node.

#! /usr/bin/env node
Enter fullscreen mode Exit fullscreen mode

If you remember while creating we have mentioned our entry point as index.js but actually this file now exist in bin folder. So we will correct that as well as we will add one more entry. The new entry which we will add is for the keyword we want to use to call our CLI. We want to use something like cowin. So we will add this entry.

"bin": {
    "cowin": "./bin/index.js"
  }
Enter fullscreen mode Exit fullscreen mode

So your package.json will look something like this

{
  "name": "vaccli",
  "version": "1.0.0",
  "description": "CLI vaccination slots",
  "main": "bin/index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Nabheet",
  "license": "ISC",
  "dependencies": {
    "axios": "^0.21.1",
    "chalk": "^4.1.1",
    "commander": "^7.2.0",
    "inquirer": "^8.0.0",
    "node-notifier": "^9.0.1",
    "tty-table": "^4.1.3"
  },
  "bin": {
    "cowin": "./bin/index.js"
  }
}

Enter fullscreen mode Exit fullscreen mode

So the basic structure is set. Now before we start adding the functionality we have not given a thought to how we will fetch the data? Lets first check that.

Do we have any api to fetch covid vaccination slots data?

Thank God on looking at Co-Win site they have provided us with OpenAPI. 50% of work is done. Now all we need to do is, consume this data and work as per our need. Lets now think about what our CLI will do.
Alt Text

What functions our CLI will perform?

On looking at closely at the calendar slots api for a district( In India we have Country comprises of States and Union Territories which in turn consists of districts) we can see it needs some kind of district id.
Alt Text

So looking at how do we get districts id we found another api but that needs state id

Alt Text

How do we get state id's another API😊

Alt Text

So our CLI shall does the following.

  • Ability to get all states and id's
  • Ability to get all district id's for a state id
  • Ability to get slots by district id
  • Ability to filter slots by ages as we have slots by 18-45 and 45 and above.
  • Apart from this some beautification
  • Desktop notification

In order to achieve this we will be using multiple npm modules lets install them first using the below mentioned command

npm install axios chalk commander inquirer node-notifier tty-table
Enter fullscreen mode Exit fullscreen mode

Packages to be installed

  • Axios –for calling the different api's
  • Chalk – for beautifying the console output
  • Commander – giving the different options and command in CLI such as cowin states or cowin districts state id is here;
  • Inquirer – for getting user input for entering the age filter
  • Node-notifier – send desktop notification
  • Tty-table – format our table output

Let's begin by creating separate functions for them. Create a util folder under cowinCLI project. Create files states.js, districts.js, config.js and slots.js in util folder. Config.js is for the configuration related common data such as table header formatting which will be used by all functions.

// Common configuration data to be used by all functions.
exports.config = {
  headers: { "User-Agent": "Axios - console app" },
};
exports.options = {
  borderStyle: "solid",
  borderColor: "blue",
  headerAlign: "center",
  align: "left",
  color: "white",
  truncate: "...",
  width: "90%",
};

Enter fullscreen mode Exit fullscreen mode

Let's first code our reusable States function in states.js

If you look, we need to call the states API for that we will use our already installed npm package axios. We are calling the api and once we got response we are formatting the table data by using tty-table package and writing the output to the console. So this function will return formatted output of states and its id's.

const axios = require('axios');
const table = require("tty-table");
const { config,options } = require('./config');
// function to return list of all states
module.exports = function() {
    axios
    .get("https://cdn-api.co-vin.in/api/v2/admin/location/states", config)
    .then((response) => {
      // table formatter
      let header = [
        {
          value: "state_id",
          headerColor: "cyan",
          alias: "State ID",
          color: "white",
          align: "left",
          width: 40,
        },
        {
          value: "state_name",
          alias: "State",
          headerColor: "cyan",
          color: "white",
          align: "left",
          width: 40,
        },
      ];
      const out = table(header, response.data.states, options).render();
      console.table(out);
    })
    .catch((error) => {
      console.log(error);
    });
};
Enter fullscreen mode Exit fullscreen mode

Let's code our second reusable Districts function in districts.js

For this also we will use similar set up of axios and tty-table. Only thing to be noted is, in this function which we are exporting has an argument as stateid.

const axios = require('axios');
const table = require("tty-table");
const { config,options } = require('./config');
// Function which take stateid as input and return all the formatted districts
module.exports = function(stateid) {
    axios
    .get(
      `https://cdn-api.co-vin.in/api/v2/admin/location/districts/${stateid}`,
      config
    )
    .then((response) => {
      // Table header specific formatting
      let header = [
        {
          value: "district_id",
          headerColor: "cyan",
          alias: "District ID",
          color: "white",
          align: "left",
          width: 40,
        },
        {
          value: "district_name",
          alias: "District",
          headerColor: "cyan",
          color: "white",
          align: "left",
          width: 40,
        },
      ];
      // Output the results.
      const out = table(header, response.data.districts, options).render();
      console.table(out);
    })
    .catch((error) => {
      console.log(error);
    });
};
Enter fullscreen mode Exit fullscreen mode

Let's code our third reusable slots function in slots.js

For this also we will use similar set up of axios and tty-table. Only thing to be noted is in this function which we are exporting has an argument as districtid. In addition to it you can see we are using chalk and inquirer package. Chalk is used to format the headers above the table and inquirer is used for taking input from user when slots command is run. We have also used node-notifier which will send desktop notification as soon as it runs, just an example. You can modify this behavior to code your own custom logic.

const axios = require('axios');
const table = require("tty-table");
const chalk = require("chalk");
const notifier = require("node-notifier");
var inquirer = require("inquirer");
const { config,options } = require('./config');

// function to check slots.
module.exports = function(district) {
  //Input prompt for getting what age you want to check records.
    inquirer
    .prompt([
      {
        type: "list",
        name: "choice",
        message: "Which Age group?",
        choices: [
          {
            name: "View All",
            value: "",
          },
          {
            name: "45 Plus",
            value: "45",
          },
          {
            name: "18 - 45 ",
            value: "18",
          },
        ],
      },
    ])
    .then((answers) => {
      const date = new Date();
      var todaysDate = `${date.getDate()}-${String(
        date.getMonth() + 1
      ).padStart(2, "0")}-${date.getFullYear()}`;
      console.log(
        chalk.underline.bgRed.bold(`Showing Slots from - ${todaysDate}`)
      );

      axios
        .get(
          `https://cdn-api.co-vin.in/api/v2/appointment/sessions/public/calendarByDistrict?district_id=${district}&date=${todaysDate}`,
          config
        )
        .then((response) => {
          let finalData = [];
          let districtName;

          response.data.centers.forEach((item) => {
            item.sessions.forEach((session) => {
              districtName = item.district_name;
              // based on user age choice filter the data
              if (answers.choice == "") {

                let data = {
                  Center: item.name,
                  Address: item.address,
                  Date: session.date,
                  FreeSlots: session.available_capacity,
                  Age: session.min_age_limit,
                };
                finalData.push(data);
              } else if (
                answers.choice == "18" &&
                session.min_age_limit == "18"
              ) {

                let data = {
                  Center: item.name,
                  Address: item.address,
                  Date: session.date,
                  FreeSlots: session.available_capacity,
                  Age: session.min_age_limit,
                };
                finalData.push(data);
              } else if (
                answers.choice == "45" &&
                session.min_age_limit == "45"
              ) {

                let data = {
                  Center: item.name,
                  Address: item.address,
                  Date: session.date,
                  FreeSlots: session.available_capacity,
                  Age: session.min_age_limit,
                };
                finalData.push(data);
              }
            });
          });
          console.log(
            chalk.underline.bgGreen.bold(`District - ${districtName}`)
          );
          switch (answers.choice) {
            case "":
              console.log(chalk.underline.bgBlue.bold(`All ages`));
              break;
            case "45":
              console.log(chalk.underline.bgBlue.bold(`45+ Age`));
              break;
            case "18":
              console.log(chalk.underline.bgBlue.bold(`18-45 Age`));
              break;
            default:
              break;
          }
          // table formatting
          let header = [
            {
              value: "Center",
              headerColor: "cyan",
              color: "white",
              align: "left",
              width: 40,
            },
            {
              value: "Address",
              headerColor: "cyan",
              color: "white",
              align: "left",
              width: 40,
            },
            {
              value: "Date",
              headerColor: "cyan",
              color: "white",
              align: "left",
              width: 15,
            },
            {
              value: "FreeSlots",
              headerColor: "cyan",
              color: "white",
              align: "left",
              width: 20,
            },
            {
              value: "Age",
              headerColor: "cyan",
              color: "white",
              align: "left",
              width: 20,
            },
          ];
          const out = table(header, finalData, options).render();
          console.table(out);
          notifier.notify({
            title: "Vaccination Slots Available",
            subtitle: "Daily Maintenance",
            message: "Immediately go and check Vaccination slots!",
            wait: true,
          });
        })
        .catch((error) => {
          console.log(error);
        });
    })
    .catch((error) => {
      if (error.isTtyError) {
        // Prompt couldn't be rendered in the current environment
      } else {
        // Something else went wrong
      }
    });
};
Enter fullscreen mode Exit fullscreen mode

Now our all basic functions are in place but what is pending is the actual CLI😊 Let's start building that.

Lets now build the CLI by updating index.js

So far we have used all npm packages except commander it is the heart of our CLI. We will be using commander for making the sub commands as well as flag options. As can be seen below we have used both command and option. Commands for getting states, districts and slots and they have a callback function mentioned as our reusable functions under action.

#! /usr/bin/env node


const program = require("commander");
// import all functions
const districts = require('../util/districts');
const states = require('../util/states');
const slots = require('../util/slots');



// adding different cli options,commands and passing callback functions in actions

program.option("-a, --available", "Output If slots available");
program
  .command("states")
  .description("Get all State Codes and descriptions.")
  .action(states);
program
  .command("district <stateid>")
  .description("Get all district of a State")
  .action(districts);

program
  .command("slots <districtid>")
  .description("Get slots for the district")
  .action(slots);

program.parse();

Enter fullscreen mode Exit fullscreen mode

Final touches

So we have everything ready all we need to do is now run below command which will install our package globally.

npm install -g .
Enter fullscreen mode Exit fullscreen mode

Output

cowin states
Enter fullscreen mode Exit fullscreen mode

States list

cowin districts 12
Enter fullscreen mode Exit fullscreen mode

Districts

cowin slots 187
Enter fullscreen mode Exit fullscreen mode

Slots

You can refer the source code

Discussion (0)