<div id="dateCarousel">
    <a href="#" id="dateCarouselPrev" class="prev"></a>
    <a href="#" id="dateCarouselNext" class="next"></a>
    <div class="wrapper">
      <div class="viewport">
        <a href="#">Week 1</a>
        <a href="#">Week 2</a>
        <a href="#">Week 3</a>
        <a href="#">Week 4</a>
        <a href="#">Week 5</a>
        <a href="#">Week 6</a>
        <a href="#">Week 7</a>
        <a href="#">Week 8</a>
        <a href="#">Week 9</a>
        <a href="#">Week 10</a>
        <a href="#">Week 11</a>
        <a href="#">Week 12</a>
        <a href="#">Week 13</a>
        <a href="#">Week 14</a>
        <a href="#">Week 15</a>
        <a href="#">Week 16</a>
        <a href="#">Week 17</a>
        <a href="#">Week 18</a>
        <a href="#">Week 19</a>
        <a href="#">Week 20</a>
        <a href="#">Week 21</a>
        <a href="#">Week 22</a>
        <a href="#">Week 23</a>
        <a href="#">Week 24</a>
        <a href="#">Week 25</a>
        <a href="#">Week 26</a>
        <a href="#">Week 27</a>
        <a href="#" class="dateCarouselSelected">Week 28</a>
        <a href="#">Week 29</a>
        <a href="#">Week 30</a>
        <a href="#">Week 31</a>
        <a href="#">Week 32</a>
        <a href="#">Week 33</a>
        <a href="#">Week 34</a>
        <a href="#">Week 35</a>
        <a href="#">Week 36</a>
        <a href="#">Week 37</a>
        <a href="#">Week 38</a>
        <a href="#">Week 39</a>
        <a href="#">Week 40</a>
        <a href="#">Birth</a>
      </div>
    </div>
</div>

@import "compass/css3";

$white: #fff;
$light-gray: #faf9f8;
$light-blue: #b2deed; 
$dark-blue: #0091c2;
$dark-pink: #ef005b;
$light-pink: #f9c8d3;

body {
  font-family: Arial, sans-serif;
}
a:focus { outline: none }

$height: 50px;
#dateCarousel {
  position: relative;
  .wrapper {
    overflow: hidden;
    height: $height;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
  }
  .prev, .next {
    position: absolute;
    height: $height;
    width: 30px;
    top:0;
    z-index: 1;
    background-color: $dark-blue;
    &:hover {
      background-color: $light-blue;
    }
    &:before, &:after{
      z-index:2; 
      content: ""; 
      display: block; 
      position: absolute;
    }
  }
  .prev {
    left: 0;
    border-right: 10px solid $light-gray;
    &:before {
      width: 0; 
      left:6px; 
      bottom:17px; 
      border-width: 8px 8px 8px 0;
      border-style: solid; 
      border-color: transparent $white;
    }
    &:after {
      width: 8px; 
      height:8px; 
      left:13px; 
      bottom:21px; 
      background-color: $white;
    }
  }
  .next {
    right: 0;
    border-left: 10px solid $light-gray;
    &:before {
      width: 0; 
      right:6px; 
      bottom:17px; 
      border-width: 8px 0 8px 8px; 
      border-style: solid; 
      border-color: transparent $white;
    }
    &:after {
      width: 8px; 
      height:8px; 
      right:14px; 
      bottom:21px;
      background-color: $white;
    }
  }
  .viewport {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 200px;
    white-space: nowrap;
    background: $light-gray;
    padding: 1rem;
    overflow: auto;
    overflow-x: scroll; /* has to be scroll, not auto */
    -webkit-overflow-scrolling: touch;
    
    a {
      padding: 0 0.5rem 0 0;
      white-space: normal;
      display: inline-block;
      &:not(:last-of-type) {
        border-right: 1px solid $light-pink;
      }
      &:not(:first-of-type) {
        margin-left: 0.4rem;
      }
      &.dateCarouselSelected {
        color: $dark-pink;
      }
    }
    
  }

  &.first {
    .prev {
      display: none;
    }
  }
  &.last {
    .next {
      display: none;
    }
  }
}

//http://pure-essence.net/2013/10/25/how-i-made-tiny-carousel-swipeable/
(function ($) {
  var opts = {
    viewport: '.viewport'
    , selected: '.dateCarouselSelected'
    , prev: '.prev'
    , next: '.next'
    , defaultScrollDistance: 200
    , scrollAnimationDuration: 500 // ms
    , itemSelector: 'a'
    , offset: 50
    , firstClass: 'first'
    , lastClass: 'last'
  };

  $.fn.carouselSwipeable = function (options) {
    var options = $.extend({}, opts, options);
    this.each(function () {
      new CarouselSwipeable($(this), options);
    });
    return this;
  };

  function CarouselSwipeable(root, options) {
    /* init date carousel */
    var $wrapper = root.find(options.viewport);
    var $selectedElement = root.find(options.selected);

    var $minItem = $wrapper.find(options.itemSelector).first();
    var $maxItem = $wrapper.find(options.itemSelector).last();
    root.removeClass(options.firstClass + ' ' + options.lastClass);

    if ($selectedElement && $selectedElement.length === 1) {
      if ($minItem[0] !== $selectedElement[0]) {
        var childPos = $selectedElement.offset();
        var parentPos = $wrapper.offset();
        var childOffset = {
          left: childPos.left - parentPos.left
        };

        var startPos = childOffset.left;
        if ($maxItem[0] !== $selectedElement[0]) {
          startPos = startPos - options.offset;
        }
        else {
          root.addClass(options.lastClass);
        }
        scroll('right', $wrapper, startPos);
      }
      else {
        root.addClass(options.firstClass);
      }
    }

    var scrollDone;
    $wrapper.on('scroll', function() {
      clearTimeout(scrollDone);
      scrollDone = setTimeout(checkEnds, 100);
    });
    
    var resizeDone;
    $(window).on('resize', function() {
      clearTimeout(resizeDone);
      resizeDone = setTimeout(checkEnds, 500);
    });

    root.find(options.prev).on('click', function (e) {
      e.preventDefault();
      e.stopPropagation();
      scroll('left', $wrapper, getDistance());
    });
    root.find(options.next).on('click', function (e) {
      e.preventDefault();
      e.stopPropagation();
      scroll('right', $wrapper, getDistance());
    });
    
    function scroll(direction, $innerWrapper, distance) {
      if (distance === undefined) {
        distance = options.defaultScrollDistance;
      }
      var leftPos = $innerWrapper.scrollLeft();

      if ('left' === direction) {
        leftPos = leftPos - distance;
      } else {
        leftPos = leftPos + distance;
      }
      $innerWrapper.animate({scrollLeft: leftPos},
        options.scrollAnimationDuration, checkEnds);
    }

    function checkEnds() {
      root.removeClass(options.firstClass + ' ' + options.lastClass);
      markFirst();
      markLast();
    }

    function markFirst() {
      var $wrapper = root.find(options.viewport);
      var minItemOffsetLeft = $minItem.offset().left;
      var minItemPositionLeft = minItemOffsetLeft - $wrapper.offset().left;
      if (minItemPositionLeft >= 0) {
        root.addClass(options.firstClass);
      }
    }

    function markLast() {
      var $wrapper = root.find(options.viewport);
      var maxItemOffsetLeft = $maxItem.offset().left;
      var maxItemPositionLeft = maxItemOffsetLeft - $wrapper.offset().left;
      if (maxItemPositionLeft <= $wrapper.outerWidth()) {
        root.addClass(options.lastClass);
      }
    }

    function getDistance() {
      var $wrapper = root.find(options.viewport);
      return $wrapper.outerWidth() - options.offset;
    }
  }
})(jQuery);

$('#dateCarousel').carouselSwipeable();