lastfm.download.helper.user.js

// ==UserScript==
// @name           Last.fm Download Helper
// @namespace      http://d.hatena.ne.jp/bannyan/
// @description    It helps you Last.fm free download easily.
// @include        http://*last.fm/*
// @include        http://www.lastfm.jp/*

// ==/UserScript==

// Configure

// How many files download when botton is clicked.
// Default is 3, but it's OK to change as you like.
const RANGE = 3;

// How long does it wait after when one file downloaded.
// Default is 5000 millisecond, otherwise 503 error occur.
const DONWLOAD_DULATION = 10000;

// ---------------------------------------------------------
GM_addStyle(<><![CDATA[

  #GMDownloadButton {
    border                        : 2px #fff solid;
    font                          : italic bold 20px Georgia,"Times New Roman",Times,serif;
    background                    : #444444;
    position                      : fixed;
    bottom                        : 20px;
    cursor                        : pointer;
    left                          : 0px;
    color                         : #fff;
    width                         : 80px;
    height                        : 30px;
    -moz-background-clip          : border;
    -moz-background-origin        : padding;
    -moz-background-inline-policy : continuous;
    -moz-opacity                  : 0.75;
  }

  #GMDownloadButton:hover {
    background : #d71102;
  }

]]></>);

var DownloadHelper = function() {

  var getDownloadUrls = function() {
    var isProperUrl = function(string) {
      return /^http:\/\/freedownloads\.last\.fm\/download\/[^ ]*\.mp3$/.test(string);
    }
    var links = document.evaluate(
      './/a',
        document,
        null,
        XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
        null
    );
    var downloadLinks = [];
    for (var i = 0; i < links.snapshotLength; i++) {
      var url = links.snapshotItem(i).href;
      if (isProperUrl(url)) {
        downloadLinks.push(url);
      }
    }
    return uniq(downloadLinks);
  }

  var setStatus = function(currentIndex, totalFileSize) {
    update(document.getElementById('GMDownloadButton'), {
      'value' : (currentIndex + 1) + '/' + totalFileSize
    });
  }
  var urls   = getDownloadUrls();
  var cursor = 0;
  var isDone = false;

  if (urls.length === 0) {
    isDone = true;
  }

  return {
    'download': function() {
      if (isDone) return;
      // forEach の break が分からない
      urls.forEach(function(url, i) {
        window.setTimeout(bind(this, function() {
          window.open(encodeURI(url), '_blank');
          if (i === urls.length - 1) {
            alert("You've successfully downloaded all of files in this page!!");
            isDone = true;
            setStatus(i, urls.length);
            return false;
          } else if (i === cursor + RANGE - 1) {
            setStatus(i, urls.length);
            return false;
          } else {
            setStatus(i, urls.length);
          }
        }), DONWLOAD_DULATION * (i));
                  console.log(i);
      });
      cursor = cursor + RANGE;
    },
    'totalFileSize': urls.length
  }
}

var downloadHelper = DownloadHelper();

document.body.appendChild(
  update(document.createElement('input'), {
    'id'    : 'GMDownloadButton',
    'type'  : 'button',
    'value' : '0/' + downloadHelper.totalFileSize
  })
).addEventListener('click', function() {
  downloadHelper.download();
}, false);

// update stolen from LDR - Signal  (c) id:brazil
function update(obj, params) {
  if(obj.setAttribute){
    for(var key in params)
      obj.setAttribute(key, params[key]);
  } else {
    for(var key in params)
      obj[key] = params[key];
  }
  return obj;
}

// bind stolen from Tumblr - Strobo  (c) id:brazil
function bind(obj, func) {
  func = (func instanceof Function)? func : obj[func];
  return function() {
    func.apply(obj, arguments);
  }
}

// uniq stolen from http://d.hatena.ne.jp/javascripter/20080730/1217413682 (c) id:javascripter
function uniq(arr) {
  var o = {};
  return Array.filter(arr,
    function(i) i in o? false: o[i] = true);
}