//
//  ON DOCUMENT CHANGE
//  Makes it possible to execute code when the DOM changes.
//
//  Licensed under the terms of the MIT license.
//  (c) 2010 Balazs Galambosi
//

(function( window ) {

var last  = +new Date();
var delay = 100; // default delay

// Manage event queue
var stack = [];

function callback() {
  var now = +new Date();
  if ( now - last > delay ) {
    for ( var i = 0; i < stack.length; i++ ) {
       stack[i]();
    }
    last = now;
  }
}

// Public interface
var onDomChange = function( fn, newdelay ) {
  if ( newdelay ) 
    delay = newdelay;
  stack.push( fn );
};

// Naive approach for compatibility
function naive() {

  var last  = document.getElementsByTagName('*');
  var lastlen = last.length;
  var timer = setTimeout( function check() {

    // get current state of the document
    var current = document.getElementsByTagName('*');
    var len = current.length;

    // if the length is different
    // it's fairly obvious
    if ( len != lastlen ) {
      // just make sure the loop finishes early
      last = [];
    }

    // go check every element in order
    for ( var i = 0; i < len; i++ ) {
      if ( current[i] !== last[i] ) {
        callback();
        last = current;
        lastlen = len;
        break;
      }
    }

    // over, and over, and over again
    setTimeout( check, delay );

  }, delay );
}

//
//  Check for mutation events support
//

var support = {};

var el = document.documentElement;
var remain = 3;

// callback for the tests
function decide() {
  if ( support.DOMNodeInserted ) {
    window.addEventListener( "DOMContentLoaded", function() {
      if ( support.DOMSubtreeModified ) { // for FF 3+, Chrome
         el.addEventListener( 'DOMSubtreeModified', callback, false );
      } else { // for FF 2, Safari, Opera 9.6+
        el.addEventListener( 'DOMNodeInserted', callback, false );
        el.addEventListener( 'DOMNodeRemoved',  callback, false );
      }
    }, false );
  } else if ( document.onpropertychange ) { // for IE 5.5+
    document.onpropertychange = callback;
  } else { // fallback
    naive();
  }
}

// checks a particular event
function test( event ) {
  el.addEventListener( event, function fn() {
    support[event] = true;
    el.removeEventListener( event, fn, false );
    if( --remain === 0 ) decide();
  }, false);
}

// attach test events
if ( window.addEventListener ) {
  test( 'DOMSubtreeModified');
  test( 'DOMNodeInserted' );
  test( 'DOMNodeRemoved' );
} else {
  decide();
}

// do the dummy test
var dummy = document.createElement("div");
el.appendChild( dummy );
el.removeChild( dummy );

// expose
window.onDomChange = onDomChange;

})( window );