// SmoothScroll v1.2.1
// Licensed under the terms of the MIT license.

// People involved
//  - Balazs Galambosi (maintainer)  
//  - Patrick Brunner  (original idea)
//  - Michael Herf     (Pulse Algorithm)
//  - Justin Force     (Resurect)
if (navigator.appVersion.indexOf("Mac") == -1) {
// Scroll Variables (tweakable)
  var framerate = 150; // [Hz]
  var animtime  = 500; // [px]
  var stepsize  = 150; // [px]

// Pulse (less tweakable)
// ratio of "tail" to "acceleration"
  var pulseAlgorithm = true;
  var pulseScale     = 8;
  var pulseNormalize = 1;

// Acceleration
  var acceleration   = true;
  var accelDelta     = 10;  // 20
  var accelMax       = 1;   // 1

// Keyboard Settings
  var keyboardsupport = true;  // option
  var disableKeyboard = false; // other reasons
  var arrowscroll     = 50;    // [px]

// Excluded pages
  var exclude = "";
  var disabled = false;

// Other Variables
  var frame = false;
  var direction = { x: 0, y: 0 };
  var initdone  = false;
  var fixedback = true;
  var root = document.documentElement;
  var activeElement;

  var key = { left: 37, up: 38, right: 39, down: 40, spacebar: 32, pageup: 33, pagedown: 34, end: 35, home: 36 };

  /**
   * Sets up scrolls array, determines if frames are involved.
   */
  function init() {

    if (!document.body) return;

    var body = document.body;
    var html = document.documentElement;
    var windowHeight = window.innerHeight;
    var scrollHeight = body.scrollHeight;

    // check compat mode for root element
    root = (document.compatMode.indexOf('CSS') >= 0) ? html : body;
    activeElement = body;

    initdone = true;

    // Checks if this script is running in a frame
    if (top != self) {
      frame = true;
    }

    /**
     * This fixes a bug where the areas left and right to
     * the content does not trigger the onmousewheel event
     * on some pages. e.g.: html, body { height: 100% }
     */
    else if (scrollHeight > windowHeight &&
        (body.offsetHeight <= windowHeight ||
        html.offsetHeight <= windowHeight)) {

      // DOMChange (throttle): fix height
      var pending = false;
      var refresh = function() {
        if (!pending && html.scrollHeight != document.height) {
          pending = true; // add a new pending action
          setTimeout(function(){
            html.style.height = document.height + 'px';
            pending = false;
          }, 500); // act rarely to stay fast
        }
      };
      html.style.height = '';
      setTimeout(refresh, 10);
      addEvent("DOMNodeInserted", refresh);
      addEvent("DOMNodeRemoved",  refresh);

      // clearfix
      if (root.offsetHeight <= windowHeight) {
        var underlay = document.createElement("div");
        underlay.style.clear = "both";
        body.appendChild(underlay);
      }
    }

    // gmail performance fix
    if (document.URL.indexOf("mail.google.com") > -1) {
      var s = document.createElement("style");
      s.innerHTML = ".iu { visibility: hidden }";
      (document.getElementsByTagName("head")[0] || html).appendChild(s);
    }
    // disable fixed background
    if (!fixedback && !disabled) {
      body.style.backgroundAttachment = "scroll";
      html.style.backgroundAttachment = "scroll";
    }
  }


  /************************************************
   * SCROLLING
   ************************************************/

  var que = [];
  var pending = false;
  var lastScroll = +new Date;

  /**
   * Pushes scroll actions to the scrolling queue.
   */
  function scrollArray(elem, left, top, delay) {

    delay || (delay = 1000);
    directionCheck(left, top);

    if (acceleration) {
      var now = +new Date;
      var elapsed = now - lastScroll;
      if (elapsed < accelDelta) {
        var factor = (1 + (30 / elapsed)) / 2;
        if (factor > 1) {
          factor = Math.min(factor, accelMax);
          left *= factor;
          top  *= factor;
        }
      }
      lastScroll = +new Date;
    }

    // push a scroll command
    que.push({
      x: left,
      y: top,
      lastX: (left < 0) ? 0.99 : -0.99,
      lastY: (top  < 0) ? 0.99 : -0.99,
      start: +new Date
    });

    // don't act if there's a pending queue
    if (pending) {
      return;
    }

    var scrollWindow = (elem === document.body);

    var step = function() {

      var now = +new Date;
      var scrollX = 0;
      var scrollY = 0;

      for (var i = 0; i < que.length; i++) {

        var item = que[i];
        var elapsed  = now - item.start;
        var finished = (elapsed >= animtime);

        // scroll position: [0, 1]
        var position = (finished) ? 1 : elapsed / animtime;

        // easing [optional]
        if (pulseAlgorithm) {
          position = pulse(position);
        }

        // only need the difference
        var x = (item.x * position - item.lastX) >> 0;
        var y = (item.y * position - item.lastY) >> 0;

        // add this to the total scrolling
        scrollX += x;
        scrollY += y;

        // update last values
        item.lastX += x;
        item.lastY += y;

        // delete and step back if it's over
        if (finished) {
          que.splice(i, 1); i--;
        }
      }

      // scroll left and top
      if (scrollWindow) {
        window.scrollBy(scrollX, scrollY)
      }
      else {
        if (scrollX) elem.scrollLeft += scrollX;
        if (scrollY) elem.scrollTop  += scrollY;
      }

      // clean up if there's nothing left to do
      if (!left && !top) {
        que = [];
      }

      if (que.length) {
        requestFrame(step, elem, (delay / framerate + 1));
      } else {
        pending = false;
      }
    }

    // start a new queue of actions
    requestFrame(step, elem, 0);
    pending = true;
  }


  /***********************************************
   * EVENTS
   ***********************************************/

  /**
   * Mouse wheel handler.
   * @param {Object} event
   */
  function wheel(event) {

    if (!initdone) {
      init();
    }

    var target = event.target;
    var overflowing = overflowingAncestor(target);

    // use default if there's no overflowing
    // element or default action is prevented
    if (!overflowing || event.defaultPrevented ||
        isNodeName(activeElement, "embed") ||
        (isNodeName(target, "embed") && /\.pdf/i.test(target.src))) {
      return true;
    }

    var deltaX = event.wheelDeltaX || 0;
    var deltaY = event.wheelDeltaY || 0;

    // use wheelDelta if deltaX/Y is not available
    if (!deltaX && !deltaY) {
      deltaY = event.wheelDelta || 0;
    }

    // scale by step size
    // delta is 120 most of the time
    // synaptics seems to send 1 sometimes
    if (Math.abs(deltaX) > 1.2) {
      deltaX *= stepsize / 120;
    }
    if (Math.abs(deltaY) > 1.2) {
      deltaY *= stepsize / 120;
    }

    scrollArray(overflowing, -deltaX, -deltaY);
    event.preventDefault();
  }

  /**
   * Keydown event handler.
   * @param {Object} event
   */
  function keydown(event) {

    var target   = event.target;
    var modifier = event.ctrlKey || event.altKey || event.metaKey ||
        (event.shiftKey && event.keyCode !== key.spacebar);

    // do nothing if user is editing text
    // or using a modifier key (except shift)
    // or in a dropdown
    if ( /input|textarea|select|embed/i.test(target.nodeName) ||
        target.isContentEditable ||
        event.defaultPrevented   ||
        modifier ) {
      return true;
    }
    // spacebar should trigger button press
    if (isNodeName(target, "button") &&
        event.keyCode === key.spacebar) {
      return true;
    }

    var shift, x = 0, y = 0;
    var elem = overflowingAncestor(activeElement);
    var clientHeight = elem.clientHeight;

    if (elem == document.body) {
      clientHeight = window.innerHeight;
    }

    switch (event.keyCode) {
      case key.up:
        y = -arrowscroll;
        break;
      case key.down:
        y = arrowscroll;
        break;
      case key.spacebar: // (+ shift)
        shift = event.shiftKey ? 1 : -1;
        y = -shift * clientHeight * 0.9;
        break;
      case key.pageup:
        y = -clientHeight * 0.9;
        break;
      case key.pagedown:
        y = clientHeight * 0.9;
        break;
      case key.home:
        y = -elem.scrollTop;
        break;
      case key.end:
        var damt = elem.scrollHeight - elem.scrollTop - clientHeight;
        y = (damt > 0) ? damt+10 : 0;
        break;
      case key.left:
        x = -arrowscroll;
        break;
      case key.right:
        x = arrowscroll;
        break;
      default:
        return true; // a key we don't care about
    }

    scrollArray(elem, x, y);
    event.preventDefault();
  }

  /**
   * Mousedown event only for updating activeElement
   */
  function mousedown(event) {
    activeElement = event.target;
  }


  /***********************************************
   * OVERFLOW
   ***********************************************/

  var cache = {}; // cleared out every once in while
  setInterval(function(){ cache = {}; }, 10 * 1000);

  var uniqueID = (function() {
    var i = 0;
    return function (el) {
      return el.uniqueID || (el.uniqueID = i++);
    };
  })();

  function setCache(elems, overflowing) {
    for (var i = elems.length; i--;)
      cache[uniqueID(elems[i])] = overflowing;
    return overflowing;
  }

  function overflowingAncestor(el) {
    var elems = [];
    var rootScrollHeight = root.scrollHeight;
    do {
      var cached = cache[uniqueID(el)];
      if (cached) {
        return setCache(elems, cached);
      }
      elems.push(el);
      if (rootScrollHeight === el.scrollHeight) {
        if (!frame || root.clientHeight + 10 < rootScrollHeight) {
          return setCache(elems, document.body); // scrolling root in WebKit
        }
      } else if (el.clientHeight + 10 < el.scrollHeight) {
        overflow = getComputedStyle(el, "").getPropertyValue("overflow-y");
        if (overflow === "scroll" || overflow === "auto") {
          return setCache(elems, el);
        }
      }
    } while (el = el.parentNode);
  }


  /***********************************************
   * HELPERS
   ***********************************************/

  function addEvent(type, fn, bubble) {
    window.addEventListener(type, fn, (bubble||false));
  }

  function removeEvent(type, fn, bubble) {
    window.removeEventListener(type, fn, (bubble||false));
  }

  function isNodeName(el, tag) {
    return (el.nodeName||"").toLowerCase() === tag.toLowerCase();
  }

  function 
(x, y) {
    x = (x > 0) ? 1 : -1;
    y = (y > 0) ? 1 : -1;
    if (direction.x !== x || direction.y !== y) {
      direction.x = x;
      direction.y = y;
      que = [];
      lastScroll = 0;
    }
  }

  var requestFrame = (function(){
    return  window.requestAnimationFrame       ||
        window.webkitRequestAnimationFrame ||
        function(callback, element, delay){
          window.setTimeout(callback, delay || (1000/60));
        };
  })();

  /***********************************************
   * PULSE
   ***********************************************/

  /**
   * Viscous fluid with a pulse for part and decay for the rest.
   * - Applies a fixed force over an interval (a damped acceleration), and
   * - Lets the exponential bleed away the velocity over a longer interval
   * - Michael Herf, http://stereopsis.com/stopping/
   */
  function pulse_(x) {
    var val, start, expx;
    // test
    x = x * pulseScale;
    if (x < 1) { // acceleartion
      val = x - (1 - Math.exp(-x));
    } else {     // tail
      // the previous animation ended here:
      start = Math.exp(-1);
      // simple viscous drag
      x -= 1;
      expx = 1 - Math.exp(-x);
      val = start + (expx * (1 - start));
    }
    return val * pulseNormalize;
  }

  function pulse(x) {
    if (x >= 1) return 1;
    if (x <= 0) return 0;

    if (pulseNormalize == 1) {
      pulseNormalize /= pulse_(1);
    }
    return pulse_(x);
  }

  addEvent("mousedown", mousedown);
  addEvent("mousewheel", wheel);
  addEvent("load", init);
}

directionCheck