var $, ScrollHandler;

$ = jQuery;

ScrollHandler = (function() {
  function ScrollHandler(tree_widget) {
    this.tree_widget = tree_widget;
    this.previous_top = -1;
    this.is_initialized = false;
  }

  ScrollHandler.prototype._initScrollParent = function() {
    var $scroll_parent, getParentWithOverflow, setDocumentAsScrollParent;
    getParentWithOverflow = (function(_this) {
      return function() {
        var css_values, el, hasOverFlow, i, len, ref;
        css_values = ['overflow', 'overflow-y'];
        hasOverFlow = function(el) {
          var css_value, i, len, ref;
          for (i = 0, len = css_values.length; i < len; i++) {
            css_value = css_values[i];
            if ((ref = $.css(el, css_value)) === 'auto' || ref === 'scroll') {
              return true;
            }
          }
          return false;
        };
        if (hasOverFlow(_this.tree_widget.$el[0])) {
          return _this.tree_widget.$el;
        }
        ref = _this.tree_widget.$el.parents();
        for (i = 0, len = ref.length; i < len; i++) {
          el = ref[i];
          if (hasOverFlow(el)) {
            return $(el);
          }
        }
        return null;
      };
    })(this);
    setDocumentAsScrollParent = (function(_this) {
      return function() {
        _this.scroll_parent_top = 0;
        return _this.$scroll_parent = null;
      };
    })(this);
    if (this.tree_widget.$el.css('position') === 'fixed') {
      setDocumentAsScrollParent();
    }
    $scroll_parent = getParentWithOverflow();
    if ($scroll_parent && $scroll_parent.length && $scroll_parent[0].tagName !== 'HTML') {
      this.$scroll_parent = $scroll_parent;
      this.scroll_parent_top = this.$scroll_parent.offset().top;
    } else {
      setDocumentAsScrollParent();
    }
    return this.is_initialized = true;
  };

  ScrollHandler.prototype._ensureInit = function() {
    if (!this.is_initialized) {
      return this._initScrollParent();
    }
  };

  ScrollHandler.prototype.checkScrolling = function() {
    var hovered_area;
    this._ensureInit();
    hovered_area = this.tree_widget.dnd_handler.hovered_area;
    if (hovered_area && hovered_area.top !== this.previous_top) {
      this.previous_top = hovered_area.top;
      if (this.$scroll_parent) {
        return this._handleScrollingWithScrollParent(hovered_area);
      } else {
        return this._handleScrollingWithDocument(hovered_area);
      }
    }
  };

  ScrollHandler.prototype._handleScrollingWithScrollParent = function(area) {
    var distance_bottom;
    distance_bottom = this.scroll_parent_top + this.$scroll_parent[0].offsetHeight - area.bottom;
    if (distance_bottom < 20) {
      this.$scroll_parent[0].scrollTop += 20;
      this.tree_widget.refreshHitAreas();
      return this.previous_top = -1;
    } else if ((area.top - this.scroll_parent_top) < 20) {
      this.$scroll_parent[0].scrollTop -= 20;
      this.tree_widget.refreshHitAreas();
      return this.previous_top = -1;
    }
  };

  ScrollHandler.prototype._handleScrollingWithDocument = function(area) {
    var distance_top;
    distance_top = area.top - $(document).scrollTop();
    if (distance_top < 20) {
      return $(document).scrollTop($(document).scrollTop() - 20);
    } else if ($(window).height() - (area.bottom - $(document).scrollTop()) < 20) {
      return $(document).scrollTop($(document).scrollTop() + 20);
    }
  };

  ScrollHandler.prototype.scrollTo = function(top) {
    var tree_top;
    this._ensureInit();
    if (this.$scroll_parent) {
      return this.$scroll_parent[0].scrollTop = top;
    } else {
      tree_top = this.tree_widget.$el.offset().top;
      return $(document).scrollTop(top + tree_top);
    }
  };

  ScrollHandler.prototype.isScrolledIntoView = function(element) {
    var $element, element_bottom, element_top, view_bottom, view_top;
    this._ensureInit();
    $element = $(element);
    if (this.$scroll_parent) {
      view_top = 0;
      view_bottom = this.$scroll_parent.height();
      element_top = $element.offset().top - this.scroll_parent_top;
      element_bottom = element_top + $element.height();
    } else {
      view_top = $(window).scrollTop();
      view_bottom = view_top + $(window).height();
      element_top = $element.offset().top;
      element_bottom = element_top + $element.height();
    }
    return (element_bottom <= view_bottom) && (element_top >= view_top);
  };

  return ScrollHandler;

})();

module.exports = ScrollHandler;