// jquery.multi-select.js
// by mySociety
// https://github.com/mysociety/jquery-multi-select

(function($) {

  var pluginName = "multiSelect",
    defaults = {
      containerHTML: '<div class="multi-select-container">',
      menuHTML: '<div class="multi-select-menu">',
      buttonHTML: '<span class="multi-select-button">',
      menuItemsHTML: '<div class="multi-select-menuitems">',
      menuItemHTML: '<label class="multi-select-menuitem">',
      presetsHTML: '<div class="multi-select-presets">',
      activeClass: 'multi-select-container--open',
      noneText: '-- Select --',
      allText: undefined,
      presets: undefined,
      positionedMenuClass: 'multi-select-container--positioned',
      positionMenuWithin: undefined
    };

  function Plugin(element, options) {
    this.element = element;
    this.$element = $(element);
    this.settings = $.extend( {}, defaults, options );
    this._defaults = defaults;
    this._name = pluginName;
    this.init();
  }

  function arraysAreEqual(array1, array2) {
    if ( array1.length != array2.length ){
      return false;
    }

    array1.sort();
    array2.sort();

    for ( var i = 0; i < array1.length; i++ ){
      if ( array1[i] !== array2[i] ){
        return false;
      }
    }

    return true;
  }

  $.extend(Plugin.prototype, {

    init: function() {
      this.checkSuitableInput();
      this.findLabels();
      this.constructContainer();
      this.constructButton();
      this.constructMenu();

      this.setUpBodyClickListener();
      this.setUpLabelsClickListener();

      this.$element.hide();
    },

    checkSuitableInput: function(text) {
      if ( this.$element.is('select[multiple]') === false ) {
        throw new Error('$.multiSelect only works on <select multiple> elements');
      }
    },

    findLabels: function() {
      this.$labels = $('label[for="' + this.$element.attr('id') + '"]');
    },

    constructContainer: function() {
      this.$container = $(this.settings.containerHTML);
      this.$element.data('multi-select-container', this.$container);
      this.$container.insertAfter(this.$element);
    },

    constructButton: function() {
      var _this = this;
      this.$button = $(this.settings.buttonHTML);
      this.$button.attr({
        'role': 'button',
        'aria-haspopup': 'true',
        'tabindex': 0,
        'aria-label': this.$labels.eq(0).text()
      })
      .on('keydown.multiselect', function(e) {
        var key = e.which;
        var returnKey = 13;
        var spaceKey = 32;
        if ((key === returnKey) || (key === spaceKey)) {
          _this.$button.click();
        }
      }).on('click.multiselect', function(e) {
        _this.menuToggle();
      })
      .appendTo(this.$container);

      this.$element.on('change.multiselect', function() {
        _this.updateButtonContents();
      });

      this.updateButtonContents();
    },

    updateButtonContents: function() {
      var _this = this;
      var options = [];
      var selected = [];

      this.$element.children('option').each(function() {
        var text = $(this).text();
        options.push(text);
        if ($(this).is(':selected')) {
          selected.push( $.trim(text) );
        }
      });

      this.$button.empty();

      if (selected.length === 0) {
        this.$button.text( this.settings.noneText );
      } else if ( (selected.length === options.length) && this.settings.allText) {
        this.$button.text( this.settings.allText );
      } else {
        this.$button.text( selected.join(', ') );
      }
    },

    constructMenu: function() {
      var _this = this;

      this.$menu = $(this.settings.menuHTML);
      this.$menu.attr({
        'role': 'menu'
      }).on('keyup.multiselect', function(e){
        var key = e.which;
        var escapeKey = 27;
        if (key === escapeKey) {
          _this.menuHide();
        }
      })
      .appendTo(this.$container);

      this.constructMenuItems();

      if ( this.settings.presets ) {
        this.constructPresets();
      }
    },

    constructMenuItems: function() {
      var _this = this;

      this.$menuItems = $(this.settings.menuItemsHTML);
      this.$menu.append(this.$menuItems);

      this.$element.on('change.multiselect', function(e, internal) {
        // Don't need to update the menu items if this
        // change event was fired by our tickbox handler.
        if(internal !== true){
          _this.updateMenuItems();
        }
      });

      this.updateMenuItems();
    },

    updateMenuItems: function() {
      var _this = this;
      this.$menuItems.empty();

      this.$element.children('option').each(function(option_index, option) {
        var $item = _this.constructMenuItem($(option), option_index);
        _this.$menuItems.append($item);
      });
    },

    constructPresets: function() {
      var _this = this;
      this.$presets = $(this.settings.presetsHTML);
      this.$menu.prepend(this.$presets);

      $.each(this.settings.presets, function(i, preset){
        var unique_id = _this.$element.attr('name') + '_preset_' + i;
        var $item = $(_this.settings.menuItemHTML)
          .attr({
            'for': unique_id,
            'role': 'menuitem'
          })
          .text(' ' + preset.name)
          .appendTo(_this.$presets);

        var $input = $('<input>')
          .attr({
            'type': 'radio',
            'name': _this.$element.attr('name') + '_presets',
            'id': unique_id
          })
          .prependTo($item);

        $input.on('change.multiselect', function(){
          _this.$element.val(preset.options);
          _this.$element.trigger('change');
        });
      });

      this.$element.on('change.multiselect', function() {
        _this.updatePresets();
      });

      this.updatePresets();
    },

    updatePresets: function() {
      var _this = this;

      $.each(this.settings.presets, function(i, preset){
        var unique_id = _this.$element.attr('name') + '_preset_' + i;
        var $input = _this.$presets.find('#' + unique_id);

        if ( arraysAreEqual(preset.options || [], _this.$element.val() || []) ){
          $input.prop('checked', true);
        } else {
          $input.prop('checked', false);
        }
      });
    },

    constructMenuItem: function($option, option_index) {
      var unique_id = this.$element.attr('name') + '_' + option_index;
      var $item = $(this.settings.menuItemHTML)
        .attr({
          'for': unique_id,
          'role': 'menuitem'
        })
        .text(' ' + $option.text());

      var $input = $('<input>')
        .attr({
          'type': 'checkbox',
          'id': unique_id,
          'value': $option.val()
        })
        .prependTo($item);

      if ( $option.is(':disabled') ) {
        $input.attr('disabled', 'disabled');
      }
      if ( $option.is(':selected') ) {
        $input.prop('checked', 'checked');
      }

      $input.on('change.multiselect', function() {
        if ($(this).prop('checked')) {
          $option.prop('selected', true);
        } else {
          $option.prop('selected', false);
        }

        // .prop() on its own doesn't generate a change event.
        // Other plugins might want to do stuff onChange.
        $option.trigger('change', [true]);
      });

      return $item;
    },

    setUpBodyClickListener: function() {
      var _this = this;

      // Hide the $menu when you click outside of it.
      $('html').on('click.multiselect', function(){
        _this.menuHide();
      });

      // Stop click events from inside the $button or $menu from
      // bubbling up to the body and closing the menu!
      this.$container.on('click.multiselect', function(e){
        e.stopPropagation();
      });
    },

    setUpLabelsClickListener: function() {
      var _this = this;
      this.$labels.on('click.multiselect', function(e) {
        e.preventDefault();
        e.stopPropagation();
        _this.menuToggle();
      });
    },

    menuShow: function() {
      this.$container.addClass(this.settings.activeClass);
      if (this.settings.positionMenuWithin && this.settings.positionMenuWithin instanceof $) {
        var menuLeftEdge = this.$menu.offset().left + this.$menu.outerWidth();
        var withinLeftEdge = this.settings.positionMenuWithin.offset().left +
          this.settings.positionMenuWithin.outerWidth();

        if( menuLeftEdge > withinLeftEdge ) {
          this.$menu.css( 'width', (withinLeftEdge - this.$menu.offset().left) );
          this.$container.addClass(this.settings.positionedMenuClass);
        }
      }
    },

    menuHide: function() {
      this.$container.removeClass(this.settings.activeClass);
      this.$container.removeClass(this.settings.positionedMenuClass);
      this.$menu.css('width', 'auto');
    },

    menuToggle: function() {
      if ( this.$container.hasClass(this.settings.activeClass) ) {
        this.menuHide();
      } else {
        this.menuShow();
      }
    }

  });

  $.fn[ pluginName ] = function(options) {
    return this.each(function() {
      if ( !$.data(this, "plugin_" + pluginName) ) {
        $.data(this, "plugin_" + pluginName,
          new Plugin(this, options) );
      }
    });
  };

})(jQuery);