/*
 *仿百度百科右側導航代碼 - 頁面目錄結構導航 v0.01
 * 只寫了兩級，無限級別也可以，是邏輯上的級別，html結構全是同一級別
 * 滑標動畫用的css3過渡動畫，不支持的瀏覽器就沒動畫效果了
 * 和百度百科比起來還是比較弱，沒有實現右邊也可以滾動的功能
 */
 function DirectoryNav($h,config){
  this.opts = $.extend(true,{
   scrollThreshold:0.5, //滾動檢測閥值 0.5在瀏覽器窗口中間部位
   scrollSpeed:700,  //滾動到指定位置的動畫時間
   scrollTopBorder:500, //滾動條距離頂部多少的時候顯示導航
   easing: 'swing',  //不解釋
   delayDetection:200,  //延時檢測，避免滾動的時候檢測過于頻繁
   scrollChange:function(){}
  },config);
  this.$win = $(window);
  this.$h = $h;
  this.$pageNavList = "";
  this.$pageNavListLis ="";
  this.$curTag = "";
  this.$pageNavListLiH = "";
  this.offArr = [];
  this.curIndex = 0;
  this.scrollIng = false;
  this.init();
 }
 DirectoryNav.prototype = {
  init:function(){
   this.make();
   this.setArr();
   this.bindEvent();
  },
  make:function(){
   //生成導航目錄結構,這是根據需求自己生成的。如果你直接在頁面中輸出一個結構那也挺好不用 搞js
   $("body").append('<div class="directory-nav" id="directoryNav"><ul></ul><span class="cur-tag"></span><span class="c-top"></span><span class="c-bottom"></span><span class="line"></span></div>>');
   var $hs = this.$h,
    $directoryNav = $("#directoryNav"),
    temp = [],
    index1 = 0,
    index2 = 0;
   $hs.each(function(index){
    var $this = $(this),
      text = $this.text();
    if(this.tagName.toLowerCase()=='h2'){
     index1++;
     if(index1%2==0) index2 = 0;
     temp.push('<li class="l1"><span class="c-dot"></span>'+index1+'. <a class="l1-text">'+text+'</a></li>');
    }else{
     index2++;
     temp.push('<li class="l2">'+index1+'.'+index2+' <a class="l2-text">'+text+'</a></li>');
    }
   });
   $directoryNav.find("ul").html(temp.join(""));
   //設置變量
   this.$pageNavList = $directoryNav;
   this.$pageNavListLis = this.$pageNavList.find("li");
   this.$curTag = this.$pageNavList.find(".cur-tag");
   this.$pageNavListLiH = this.$pageNavListLis.eq(0).height();
   if(!this.opts.scrollTopBorder){
    this.$pageNavList.show();
   }
  },
  setArr:function(){
   var This = this;
   this.$h.each(function(){
    var $this = $(this),
     offT = Math.round($this.offset().top);
    This.offArr.push(offT);
   });
  },
  posTag:function(top){
   this.$curTag.css({top:top+'px'});
  },
  ifPos:function(st){
   var offArr = this.offArr;
   //console.log(st);
   var windowHeight = Math.round(this.$win.height() * this.opts.scrollThreshold);
   for(var i=0;i<offArr.length;i++){
    if((offArr[i] - windowHeight) < st) {
     var $curLi = this.$pageNavListLis.eq(i),
      tagTop = $curLi.position().top;
     $curLi.addClass("cur").siblings("li").removeClass("cur");
     this.curIndex = i;
     this.posTag(tagTop+this.$pageNavListLiH*0.5);
     //this.curIndex = this.$pageNavListLis.filter(".cur").index();
     this.opts.scrollChange.call(this);
    }
   }
  },
  bindEvent:function(){
   var This = this,
    show = false,
    timer = 0;
   this.$win.on("scroll",function(){
    var $this = $(this);
    clearTimeout(timer);
    timer = setTimeout(function(){
     This.scrollIng = true;
     if($this.scrollTop()>This.opts.scrollTopBorder){
      if(!This.$pageNavListLiH) This.$pageNavListLiH = This.$pageNavListLis.eq(0).height();
      if(!show){
       This.$pageNavList.fadeIn();
       show = true;
      }
      This.ifPos( $(this).scrollTop() );
     }else{
      if(show){
       This.$pageNavList.fadeOut();
       show = false;
      }
     }
    },This.opts.delayDetection);
   });
   this.$pageNavList.on("click","li",function(){
    var $this = $(this),
     index = $this.index();
    This.scrollTo(This.offArr[index]);
   })
  },
  scrollTo: function(offset,callback) {
   var This = this;
   $('html,body').animate({
    scrollTop: offset
   }, this.opts.scrollSpeed, this.opts.easing, function(){
    This.scrollIng = false;
    //修正彈兩次回調 蛋疼
    callback && this.tagName.toLowerCase()=='body' && callback();
   });
  }
 };
 //調用實例化
 var directoryNav = new DirectoryNav($("h2,h3"),{
  scrollTopBorder:0 //滾動條距離頂部多少的時候顯示導航，如果為0，則一直顯示
 });