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

(function($, Drupal, Backbone, _) {
  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(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));
        this.manageTabbing();
      },

      /**
       * @inheritdoc
       *
       * @return {Drupal.contextualToolbar.AuralView}
       *   The current contextual toolbar aural view.
       */
      render() {
        // 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() {
        let tabbingContext = this.model.get('tabbingContext');
        // Always release an existing tabbing context.
        if (tabbingContext) {
          // Only announce release when the context was active.
          if (tabbingContext.active) {
            Drupal.announce(this.options.strings.tabbingReleased);
          }
          tabbingContext.release();
        }
        // 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() {
        const 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(event) {
        // The first tab key press is tracked so that an announcement 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, _);