// Manage back/forward buttons

var History = Base.extend({
  constructor: function(callback) {
    this.visited = {};
  //-  var scrollTop = this.scrollTop = {};
    
    var hash;
    this.timer = setInterval(function() {
      if (hash != location.hash) {
        hash = location.hash;
        callback();
      //-  document.documentElement.scrollTop = scrollTop[hash];
      }
    }, 20);
    
  /*  // preserve scroll position
    window.onscroll = function() {
      if (hash == location.hash) {
        scrollTop[hash] = document.documentElement.scrollTop;
      }
    }; */
    
    this.add(location.hash || ("#" + (document.title.slice(9) || "/")));
  },
  
  timer: 0,
  visited: null,
  
  add: function(hash) {
    if (location.hash != hash) {
      location.hash = hash;
    }
  //-  this.scrollTop[hash] = 0;
    this.visited[hash] = true;
  },
  
  "@MSIE": {
    add: function(hash) {
      History.$write(hash);
      this.base(hash);
    }
  }
}, {    
  init: function() {
    // the hash portion of the location needs to be set for history to work properly
    // -- we need to do it before the page has loaded
    if (!location.hash) location.replace("#" + (document.title.slice(9) || "/"));
  },
  
  "@MSIE": {
    $write: function(hash) {
      if (hash != location.hash) {
        var document = frames[0].document;
        document.open();
        document.write("<script>parent.location.hash='" + hash + "'<\/script>");
        document.close();
      }
    },
    
    init: function() {
      this.base();
      document.write("<iframe style=display:none></iframe>");
      this.$write(location.hash.slice(1)); // make sure it's unique the first time
    }
  }
});