gpsc

var casper = require('casper').create({
  viewportSize: {
    width: 1280,
    height: 1024
  },
  pageSettings: {
    webSecurityEnabled: false,
    // TODO: generated slight variations of the UA strings
    userAgent: "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36"
  }
});

var links = [];
var price = casper.cli.get('price');
var keyword = casper.cli.get('search');
var topN = casper.cli.get('top');
var timeout = 5000;
var baseurl = 'https://play.google.com/store/search?c=apps';

var retries = 0;
var max_retries = 3;
var scrolled = 0;
var delta = 0;
var scrollInc = 50;
var scrollAdj = 10;

function sY() {
  return window.scrollY;
}

function geturl() {
  baseurl = baseurl + '&q=' + keyword;

  if (price === "free")
    price = 1;
  else if (price === "paid")
    price = 2;
  else
    price = false;

  if (price != false)
    baseurl = baseurl + '&price=' + price;

  if (topN == undefined)
    topN = 10;

  return baseurl;
}

function getLinks() {
  var links = document.querySelectorAll('a.title');
  return Array.prototype.map.call(links, function(e) {
    return e.getAttribute('href').split('=')[1];
  });
}

function slowScrollUp(casper) {
  casper.log('^^^', 'debug');

  casper.scrollTo(0, scrolled - scrollAdj);
  pos = casper.evaluate(sY);
  scrolled = pos;
}

function enoughResults(casper) {
  var l = casper.evaluate(getLinks).length;

  casper.log('Enough links found? (' + l + ')', 'debug');

  return l >= topN;
}

function slowScrollDown(casper) {
  casper.log('vvv', 'debug');

  casper.scrollTo(0, scrolled + scrollInc);
  pos = casper.evaluate(sY);
  delta = scrolled - pos;
  scrolled = pos;

  casper.log('sY = ' + scrolled + ' (+' + delta + ')', 'debug');

  if (!delta) {
    if (retries == max_retries) {
      casper.emit('bottom.reached');
      retries = 0;
      return;
    } else {
      casper.wait(700, function() {
        slowScrollUp(casper);
      });
      retries += 1;
    }
  }

  if (enoughResults(casper))
    casper.emit('end.reached');
  else
    casper.wait(700, function(){
      slowScrollDown(casper);
    });
}

casper.start(geturl(), function() {
  this.wait(timeout, function() {
    this.waitUntilVisible(
      '.copyright',
      function then() {
        this.wait(1000, function(){
          this.emit('page.loaded');
        });
      },
      function ontimeout() {
        casper.log('Timeout!', 'debug');
      },
      1000);
  });
});

casper.on('page.loaded', function() {
  casper.log('Page loaded', 'debug');

  if (enoughResults(this))
    this.emit('end.reached');
  else
    slowScrollDown(this);
});

casper.on('bottom.reached', function() {
  casper.log('Bottom reached', 'debug');

  if (enoughResults(this))
    this.emit('end.reached');
  else {
    if (this.visible('#show-more-button')) {
      casper.log('Button is visible: there is more to load!', 'debug')

      this.click('#show-more-button');
      this.wait(300, function() {
        slowScrollDown(this);
      });
    } else {
      this.emit('end.reached');
    }
  }
});

casper.on('end.reached', function () {
  casper.log('Dumping links...', 'debug');
  links = this.evaluate(getLinks);
});

casper.run(function() {
  this.echo(links.slice(0, topN).join('\n'));
  this.exit();
});