define([
  'jquery',
  './utils'
], function ($, Utils) {
  function Results ($element, options, dataAdapter) {
    this.$element = $element;
    this.data = dataAdapter;
    this.options = options;

    Results.__super__.constructor.call(this);
  }

  Utils.Extend(Results, Utils.Observable);

  Results.prototype.render = function () {
    var $results = $(
      '<ul class="select2-results__options" role="listbox"></ul>'
    );

    if (this.options.get('multiple')) {
      $results[0].setAttribute('aria-multiselectable', 'true');
    }

    this.$results = $results;

    return $results;
  };

  Results.prototype.clear = function () {
    this.$results.empty();
  };

  Results.prototype.displayMessage = function (params) {
    var escapeMarkup = this.options.get('escapeMarkup');

    this.clear();
    this.hideLoading();

    var $message = $(
      '<li role="alert" aria-live="assertive"' +
      ' class="select2-results__option"></li>'
    );

    var message = this.options.get('translations').get(params.message);

    $message.append(
      escapeMarkup(
        message(params.args)
      )
    );

    $message[0].className += ' select2-results__message';

    this.$results.append($message);
  };

  Results.prototype.hideMessages = function () {
    this.$results.find('.select2-results__message').remove();
  };

  Results.prototype.append = function (data) {
    this.hideLoading();

    var $options = [];

    if (data.results == null || data.results.length === 0) {
      if (this.$results.children().length === 0) {
        this.trigger('results:message', {
          message: 'noResults'
        });
      }

      return;
    }

    data.results = this.sort(data.results);

    for (var d = 0; d < data.results.length; d++) {
      var item = data.results[d];

      var $option = this.option(item);

      $options.push($option);
    }

    this.$results.append($options);
  };

  Results.prototype.position = function ($results, $dropdown) {
    var $resultsContainer = $dropdown.find('.select2-results');
    $resultsContainer.append($results);
  };

  Results.prototype.sort = function (data) {
    var sorter = this.options.get('sorter');

    return sorter(data);
  };

  Results.prototype.highlightFirstItem = function () {
    var $options = this.$results
      .find('.select2-results__option--selectable');

    var $selected = $options.filter('.select2-results__option--selected');

    // Check if there are any selected options
    if ($selected.length > 0) {
      // If there are selected options, highlight the first
      $selected.first().trigger('mouseenter');
    } else {
      // If there are no selected options, highlight the first option
      // in the dropdown
      $options.first().trigger('mouseenter');
    }

    this.ensureHighlightVisible();
  };

  Results.prototype.setClasses = function () {
    var self = this;

    this.data.current(function (selected) {
      var selectedIds = selected.map(function (s) {
        return s.id.toString();
      });

      var $options = self.$results
        .find('.select2-results__option--selectable');

      $options.each(function () {
        var $option = $(this);

        var item = Utils.GetData(this, 'data');

        // id needs to be converted to a string when comparing
        var id = '' + item.id;

        if ((item.element != null && item.element.selected) ||
            (item.element == null && selectedIds.indexOf(id) > -1)) {
          this.classList.add('select2-results__option--selected');
          $option[0].setAttribute('aria-selected', 'true');
        } else {
          this.classList.remove('select2-results__option--selected');
          $option[0].setAttribute('aria-selected', 'false');
        }
      });

    });
  };

  Results.prototype.showLoading = function (params) {
    this.hideLoading();

    var loadingMore = this.options.get('translations').get('searching');

    var loading = {
      disabled: true,
      loading: true,
      text: loadingMore(params)
    };
    var $loading = this.option(loading);
    $loading.className += ' loading-results';

    this.$results.prepend($loading);
  };

  Results.prototype.hideLoading = function () {
    this.$results.find('.loading-results').remove();
  };

  Results.prototype.option = function (data) {
    var option = document.createElement('li');
    option.classList.add('select2-results__option');
    option.classList.add('select2-results__option--selectable');

    var attrs = {
      'role': 'option'
    };

    var matches = window.Element.prototype.matches ||
      window.Element.prototype.msMatchesSelector ||
      window.Element.prototype.webkitMatchesSelector;

    if ((data.element != null && matches.call(data.element, ':disabled')) ||
        (data.element == null && data.disabled)) {
      attrs['aria-disabled'] = 'true';

      option.classList.remove('select2-results__option--selectable');
      option.classList.add('select2-results__option--disabled');
    }

    if (data.id == null) {
      option.classList.remove('select2-results__option--selectable');
    }

    if (data._resultId != null) {
      option.id = data._resultId;
    }

    if (data.title) {
      option.title = data.title;
    }

    if (data.children) {
      attrs.role = 'group';
      attrs['aria-label'] = data.text;

      option.classList.remove('select2-results__option--selectable');
      option.classList.add('select2-results__option--group');
    }

    for (var attr in attrs) {
      var val = attrs[attr];

      option.setAttribute(attr, val);
    }

    if (data.children) {
      var $option = $(option);

      var label = document.createElement('strong');
      label.className = 'select2-results__group';

      this.template(data, label);

      var $children = [];

      for (var c = 0; c < data.children.length; c++) {
        var child = data.children[c];

        var $child = this.option(child);

        $children.push($child);
      }

      var $childrenContainer = $('<ul></ul>', {
        'class': 'select2-results__options select2-results__options--nested',
        'role': 'none'
      });

      $childrenContainer.append($children);

      $option.append(label);
      $option.append($childrenContainer);
    } else {
      this.template(data, option);
    }

    Utils.StoreData(option, 'data', data);

    return option;
  };

  Results.prototype.bind = function (container, $container) {
    var self = this;

    var id = container.id + '-results';

    this.$results[0].setAttribute('id', id);

    container.on('results:all', function (params) {
      self.clear();
      self.append(params.data);

      if (container.isOpen()) {
        self.setClasses();
        self.highlightFirstItem();
      }
    });

    container.on('results:append', function (params) {
      self.append(params.data);

      if (container.isOpen()) {
        self.setClasses();
      }
    });

    container.on('query', function (params) {
      self.hideMessages();
      self.showLoading(params);
    });

    container.on('select', function () {
      if (!container.isOpen()) {
        return;
      }

      self.setClasses();

      if (self.options.get('scrollAfterSelect')) {
        self.highlightFirstItem();
      }
    });

    container.on('unselect', function () {
      if (!container.isOpen()) {
        return;
      }

      self.setClasses();

      if (self.options.get('scrollAfterSelect')) {
        self.highlightFirstItem();
      }
    });

    container.on('open', function () {
      // When the dropdown is open, aria-expended="true"
      self.$results[0].setAttribute('aria-expanded', 'true');
      self.$results[0].setAttribute('aria-hidden', 'false');

      self.setClasses();
      self.ensureHighlightVisible();
    });

    container.on('close', function () {
      // When the dropdown is closed, aria-expended="false"
      self.$results[0].setAttribute('aria-expanded', 'false');
      self.$results[0].setAttribute('aria-hidden', 'true');
      self.$results[0].removeAttribute('aria-activedescendant');
    });

    container.on('results:toggle', function () {
      var $highlighted = self.getHighlightedResults();

      if ($highlighted.length === 0) {
        return;
      }

      $highlighted.trigger('mouseup');
    });

    container.on('results:select', function () {
      var $highlighted = self.getHighlightedResults();

      if ($highlighted.length === 0) {
        return;
      }

      var data = Utils.GetData($highlighted[0], 'data');

      if ($highlighted.hasClass('select2-results__option--selected')) {
        self.trigger('close', {});
      } else {
        self.trigger('select', {
          data: data
        });
      }
    });

    container.on('results:previous', function () {
      var $highlighted = self.getHighlightedResults();

      var $options = self.$results.find('.select2-results__option--selectable');

      var currentIndex = $options.index($highlighted);

      // If we are already at the top, don't move further
      // If no options, currentIndex will be -1
      if (currentIndex <= 0) {
        return;
      }

      var nextIndex = currentIndex - 1;

      // If none are highlighted, highlight the first
      if ($highlighted.length === 0) {
        nextIndex = 0;
      }

      var $next = $options.eq(nextIndex);

      $next.trigger('mouseenter');

      var currentOffset = self.$results.offset().top;
      var nextTop = $next.offset().top;
      var nextOffset = self.$results.scrollTop() + (nextTop - currentOffset);

      if (nextIndex === 0) {
        self.$results.scrollTop(0);
      } else if (nextTop - currentOffset < 0) {
        self.$results.scrollTop(nextOffset);
      }
    });

    container.on('results:next', function () {
      var $highlighted = self.getHighlightedResults();

      var $options = self.$results.find('.select2-results__option--selectable');

      var currentIndex = $options.index($highlighted);

      var nextIndex = currentIndex + 1;

      // If we are at the last option, stay there
      if (nextIndex >= $options.length) {
        return;
      }

      var $next = $options.eq(nextIndex);

      $next.trigger('mouseenter');

      var currentOffset = self.$results.offset().top +
        self.$results.outerHeight(false);
      var nextBottom = $next.offset().top + $next.outerHeight(false);
      var nextOffset = self.$results.scrollTop() + nextBottom - currentOffset;

      if (nextIndex === 0) {
        self.$results.scrollTop(0);
      } else if (nextBottom > currentOffset) {
        self.$results.scrollTop(nextOffset);
      }
    });

    container.on('results:focus', function (params) {
      params.element[0].classList.add('select2-results__option--highlighted');
      params.element[0].setAttribute('aria-selected', 'true');
    });

    container.on('results:message', function (params) {
      self.displayMessage(params);
    });

    if ($.fn.mousewheel) {
      this.$results.on('mousewheel', function (e) {
        var top = self.$results.scrollTop();

        var bottom = self.$results.get(0).scrollHeight - top + e.deltaY;

        var isAtTop = e.deltaY > 0 && top - e.deltaY <= 0;
        var isAtBottom = e.deltaY < 0 && bottom <= self.$results.height();

        if (isAtTop) {
          self.$results.scrollTop(0);

          e.preventDefault();
          e.stopPropagation();
        } else if (isAtBottom) {
          self.$results.scrollTop(
            self.$results.get(0).scrollHeight - self.$results.height()
          );

          e.preventDefault();
          e.stopPropagation();
        }
      });
    }

    this.$results.on('mouseup', '.select2-results__option--selectable',
      function (evt) {
      var $this = $(this);

      var data = Utils.GetData(this, 'data');

      if ($this.hasClass('select2-results__option--selected')) {
        if (self.options.get('multiple')) {
          self.trigger('unselect', {
            originalEvent: evt,
            data: data
          });
        } else {
          self.trigger('close', {
            originalEvent: evt,
            data: data
          });
        }

        return;
      }

      self.trigger('select', {
        originalEvent: evt,
        data: data
      });
    });

    this.$results.on('mouseenter', '.select2-results__option--selectable',
      function (evt) {
      var data = Utils.GetData(this, 'data');

      var $highlighted = self.getHighlightedResults();
      $highlighted.removeClass('select2-results__option--highlighted');
      $highlighted.each(function () {
        this.setAttribute('aria-selected', 'false');
      });

      self.trigger('results:focus', {
        data: data,
        element: $(this)
      });
    });
  };

  Results.prototype.getHighlightedResults = function () {
    var $highlighted = this.$results
    .find('.select2-results__option--highlighted');

    return $highlighted;
  };

  Results.prototype.destroy = function () {
    this.$results.remove();
  };

  Results.prototype.ensureHighlightVisible = function () {
    var $highlighted = this.getHighlightedResults();

    if ($highlighted.length === 0) {
      return;
    }

    var $options = this.$results.find('.select2-results__option--selectable');

    var currentIndex = $options.index($highlighted);

    var currentOffset = this.$results.offset().top;
    var nextTop = $highlighted.offset().top;
    var nextOffset = this.$results.scrollTop() + (nextTop - currentOffset);

    var offsetDelta = nextTop - currentOffset;
    nextOffset -= $highlighted.outerHeight(false) * 2;

    if (currentIndex <= 2) {
      this.$results.scrollTop(0);
    } else if (offsetDelta > this.$results.outerHeight() || offsetDelta < 0) {
      this.$results.scrollTop(nextOffset);
    }
  };

  Results.prototype.template = function (result, container) {
    var template = this.options.get('templateResult');
    var escapeMarkup = this.options.get('escapeMarkup');

    var content = template(result, container);

    if (content == null) {
      container.style.display = 'none';
    } else if (typeof content === 'string') {
      container.innerHTML = escapeMarkup(content);
    } else {
      $(container).append(content);
    }
  };

  return Results;
});
