// ==UserScript==
// @name               jsmonkey-gcsearch additional Google search filters
// @namespace          http://techexplored.com
// @description        Adds 2 custom search filters to limit search results to the past 6 months or 2 years.
// @contributor        petermac-
// @version            2014.05.09
//
// @icon               http://www.google.com/favicon.ico
// @include            /(http|https)?://.*\.google\.[^\/]+?/(#.*|search\?.*)?$/
// @grant              none
// @run-at             document-end
// ==/UserScript==
var timer, log, start;

function addElement() {
    var search = document.getElementById('qdr_m').firstChild.getAttribute('href');
    var beginURL = search.match(/.*(?=&tbs)/);
    var filter_parent = document.getElementById('qdr_y').parentNode;
    var insert_index = 5;

    var url_6m = beginURL + "&tbs=qdr:m6";
    var url_2y = beginURL + "&tbs=qdr:y2";

    var filters = [url_6m, url_2y];

    for (var filter in filters) {
      var li = document.createElement('li');
      li.setAttribute('class', 'hdtbItm');

      var a = document.createElement('a');
      a.setAttribute('class', 'q qs');
      a.setAttribute('href', filter);
      a.innerHTML = 'Past 6 months';

      li.appendChild(a);
      filter_parent.insertBefore(li, filter_parent.childNodes[insert_index]);
      insert_index += 2;
    }
}

log = document.getElementById("log");
function repeatXI(callback, interval, repeats, immediate) {
    var timer, trigger;
    trigger = function() {
        callback();
        --repeats || clearInterval(timer);
    };

    interval = interval <= 0 ? 1000 : interval; // default: 1000ms
    repeats = parseInt(repeats, 10) || 0; // default: repeat forever
    timer = setInterval(trigger, interval);

    if ( !! immediate) { // Coerce boolean
        trigger();
    }

    return timer;
}

function cb() {
    var search = document.getElementById('qdr_y').parentNode;
    var length = search.children.length;

    if(length > 7) {
        //console.log('element already added');
      return true;
    }
    //console.log('element not yet added');
    addElement();
}

if( timer ) { clearInterval(timer); }
start = (new Date).getTime();
var args = [ 4000, 0, true ];
timer = repeatXI.apply(null, [cb].concat(args));