rng.ts

import { promisify } from 'util';
import * as crypto from 'crypto';
import * as path from 'path';
import * as puppeteer from 'puppeteer';
import * as fs from 'fs';

interface ITargets {
  targetInfos: any;
}

interface IWindowForTarget {
  windowId: any;
}

const TEMP_FILE = path.join(__dirname, '../temp.png');
const readFile = promisify(fs.readFile)
const unlink = promisify(fs.unlink);

process.on('unhandledRejection', error => {
  console.log('unhandledRejection', error);
});

function getChecksum(str: string) {
  return crypto
    .createHash('md5')
    .update(str, 'utf8')
    .digest('hex');
}

function random(seed: string) {
  let seedNumber = seed.split('').map((_, i) => {
    return seed.charCodeAt(i);
  }).reduce((a, b) => a + b, 0);

  var x = Math.sin(seedNumber) * 10000;
  return x - Math.floor(x);
}

async function resizeWindow(browser: puppeteer.Browser, page: puppeteer.Page, width: number, height: number) {
  const client = await browser.target().createCDPSession();
  await page.setViewport({height, width});

  height += 85;
  
  const { targetInfos: [{targetId}] } = await client.send(
    'Target.getTargets'
  ) as ITargets;
  
  const { windowId } = await client.send(
    'Browser.getWindowForTarget',
    {targetId}
  ) as IWindowForTarget;
  
  await client.send('Browser.setWindowBounds', {
    bounds: {height, width},
    windowId
  });    
}

async function randInt(min: number, max: number) {
  const browser = await puppeteer.launch({
    headless: false
  });
  const page = await browser.newPage();
  
  resizeWindow(browser, page, 800, 700);

  await page.goto('https://www.google.fi/search?q=rng');
  await page.evaluate((min, max) => {
    const minEl = document.querySelector('#UMy8j') as HTMLInputElement;
    const maxEl = document.querySelector('#nU5Yvb') as HTMLInputElement;
    const btnEl = document.querySelector('#ZdzlKb') as HTMLElement;
    
    minEl.value = min.toString();
    maxEl.value = max.toString();
    btnEl.click();
  }, min, max);
  
  await page.waitFor(1100);
  
  await page.screenshot({
    clip: {
      x: 163,
      y: 385,
      width: 250,
      height: 50
    },
    path: TEMP_FILE
  });

  await browser.close();

  const content = await readFile(TEMP_FILE, 'utf-8');
  const checksum = getChecksum(content);

  unlink(TEMP_FILE);

  return Math.floor(random(checksum) * max) + min;
}

(async () => {
  console.log(await randInt(1, 1000));
})();