Fill in the MTR late cert form usling puppeteer.

latecert.js

const puppeteer = require('puppeteer');
const readline = require('readline');
const sleep = require('util').promisify(setTimeout);

require('dotenv').config();

const EVENT_SELECTOR = 'select#ddlEvent';
const NAME_SELECTOR = 'input#username';
const EMAIL_SELECTOR = 'input#email';
const CAPTCHA_SELECTOR = 'input#captcha-form';
const CAPTCHA_IMAGE_SELECTOR = 'img#captcha';
const CAPTCHA_INVALID_SELECTOR = 'span#valid_captcha';
const SUBMIT_FORM_SELECTOR = 'form#regform input[type="submit"]';

let submitSuccess = false;

(async () => {
    const browser = await puppeteer.launch({headless: process.env.HEADLESS === 'true'});
    const page = await browser.newPage();

    page.on('request', async request => {
        console.log(request.url());
        if (submitSuccess) {
            await onSubmitSuccess(browser);
        } else if (request.url() === 'http://www.mtr.com.hk/eng/homepage/cust_index.html') {
            await onNoLateCertProvide(browser)
        }
    });

    page.on('dialog', async dialog => {
        if (dialog.message() === 'The form is submitted successfully') {
            submitSuccess = true;
        }
        await dialog.accept();
    });

    await page.goto('https://tnsms1.mtr.com.hk/latecert/form_en.php');

    await agreeTerms(page);

    const events = await getEvents(page);
    await selectEvent(page, events[0].value);
    await fillInContactInfo(page);

    await changeCaptchaImage(page);
    await extractCaptchaImage(page);

    do {
        const ans = await askQuestion("Type the CAPTCHA: ");
        await fillInCaptcha(page, ans);
        await submitForm(page);
        await sleep(3000);
        if (!submitSuccess) {
            const captchaCorrect = await isCaptchaCorrect(page);
            console.log('captchaCorrect: ' + captchaCorrect);
            await changeCaptchaImage(page);
            await extractCaptchaImage(page);
        }
    } while (!submitSuccess);
})();

async function agreeTerms(page) {
    await page.waitForSelector('#form_agree');
    await page.click('input[type="submit"][value="Agree and submit"]');
}

async function getEvents(page) {
    await page.waitForSelector(EVENT_SELECTOR);
    return await page.evaluate((selector) => {
        return Array.apply(null, document.querySelector(selector).options)
            .map(item => {
                return {text: item.text, value: item.value}
            });
    }, EVENT_SELECTOR);
}

async function selectEvent(page, value) {
    await page.select(EVENT_SELECTOR, value);
}

async function fillInContactInfo(page) {
    await page.type(NAME_SELECTOR, 'Your Name');
    await page.type(EMAIL_SELECTOR, '[email protected]');
}

async function fillInCaptcha(page, captchaText) {
    await page.evaluate((selector) => document.querySelector(selector).value = "", CAPTCHA_SELECTOR);
    await page.type(CAPTCHA_SELECTOR, captchaText);
}

async function extractCaptchaImage(page) {
    const captcha = await page.$(CAPTCHA_IMAGE_SELECTOR);
    await captcha.screenshot({
        path: 'captcha.png',
        omitBackground: true,
    });
}

async function changeCaptchaImage(page) {
    await page.click('a[href="javascript:changeCaptcha()"]');
}

async function submitForm(page) {
    await page.click(SUBMIT_FORM_SELECTOR);
}

async function isCaptchaCorrect(page) {
    try {
        await page.waitForNavigation({waitUntil: "networkidle0", timeout: 1500});
    } catch (e) {
    }
    try {
        return await page.$eval(CAPTCHA_INVALID_SELECTOR, (elem) => window.getComputedStyle(elem).getPropertyValue('display') === 'none');
    } catch (e) {
        return false;
    }
}

async function onSubmitSuccess(browser) {
    await browser.close();
}

async function onNoLateCertProvide(browser) {
    await browser.close();
}

function askQuestion(query) {
    const rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout,
    });

    return new Promise(resolve => rl.question(query, ans => {
        rl.close();
        resolve(ans);
    }))
}