/**
 * @file
 * A Backbone View that provides the aural view of the edit mode toggle.
 */

(function ($, Drupal, Backbone, _) {

  'use strict';

  Drupal.contextualToolbar.AuralView = Backbone.View.extend(/** @lends Drupal.contextualToolbar.AuralView# */{

    /**
     * Tracks whether the tabbing constraint announcement has been read once.
     *
     * @type {bool}
     */
    announcedOnce: false,

    /**
     * Renders the aural view of the edit mode toggle (screen reader support).
     *
     * @constructs
     *
     * @augments Backbone.View
     *
     * @param {object} options
     *   Options for the view.
     */
    initialize: function (options) {
      this.options = options;

      this.listenTo(this.model, 'change', this.render);
      this.listenTo(this.model, 'change:isViewing', this.manageTabbing);

      $(document).on('keyup', _.bind(this.onKeypress, this));
    },

    /**
     * @inheritdoc
     *
     * @return {Drupal.contextualToolbar.AuralView}
     *   The current contextual toolbar aural view.
     */
    render: function () {
      // Render the state.
      this.$el.find('button').attr('aria-pressed', !this.model.get('isViewing'));

      return this;
    },

    /**
     * Limits tabbing to the contextual links and edit mode toolbar tab.
     */
    manageTabbing: function () {
      var tabbingContext = this.model.get('tabbingContext');
      // Always release an existing tabbing context.
      if (tabbingContext) {
        tabbingContext.release();
        Drupal.announce(this.options.strings.tabbingReleased);
      }
      // Create a new tabbing context when edit mode is enabled.
      if (!this.model.get('isViewing')) {
        tabbingContext = Drupal.tabbingManager.constrain($('.contextual-toolbar-tab, .contextual'));
        this.model.set('tabbingContext', tabbingContext);
        this.announceTabbingConstraint();
        this.announcedOnce = true;
      }
    },

    /**
     * Announces the current tabbing constraint.
     */
    announceTabbingConstraint: function () {
      var strings = this.options.strings;
      Drupal.announce(Drupal.formatString(strings.tabbingConstrained, {
        '@contextualsCount': Drupal.formatPlural(Drupal.contextual.collection.length, '@count contextual link', '@count contextual links')
      }));
      Drupal.announce(strings.pressEsc);
    },

    /**
     * Responds to esc and tab key press events.
     *
     * @param {jQuery.Event} event
     *   The keypress event.
     */
    onKeypress: function (event) {
      // The first tab key press is tracked so that an annoucement about tabbing
      // constraints can be raised if edit mode is enabled when the page is
      // loaded.
      if (!this.announcedOnce && event.keyCode === 9 && !this.model.get('isViewing')) {
        this.announceTabbingConstraint();
        // Set announce to true so that this conditional block won't run again.
        this.announcedOnce = true;
      }
      // Respond to the ESC key. Exit out of edit mode.
      if (event.keyCode === 27) {
        this.model.set('isViewing', true);
      }
    }

  });

})(jQuery, Drupal, Backbone, _);
