/**
 * @file
 * A Backbone Model for the state of Contextual module's edit toolbar tab.
 */

(function(Drupal, Backbone) {
  Drupal.contextualToolbar.StateModel = Backbone.Model.extend(
    /** @lends Drupal.contextualToolbar.StateModel# */ {
      /**
       * @type {object}
       *
       * @prop {bool} isViewing
       * @prop {bool} isVisible
       * @prop {number} contextualCount
       * @prop {Drupal~TabbingContext} tabbingContext
       */
      defaults: /** @lends Drupal.contextualToolbar.StateModel# */ {
        /**
         * Indicates whether the toggle is currently in "view" or "edit" mode.
         *
         * @type {bool}
         */
        isViewing: true,

        /**
         * Indicates whether the toggle should be visible or hidden. Automatically
         * calculated, depends on contextualCount.
         *
         * @type {bool}
         */
        isVisible: false,

        /**
         * Tracks how many contextual links exist on the page.
         *
         * @type {number}
         */
        contextualCount: 0,

        /**
         * A TabbingContext object as returned by {@link Drupal~TabbingManager}:
         * the set of tabbable elements when edit mode is enabled.
         *
         * @type {?Drupal~TabbingContext}
         */
        tabbingContext: null,
      },

      /**
       * Models the state of the edit mode toggle.
       *
       * @constructs
       *
       * @augments Backbone.Model
       *
       * @param {object} attrs
       *   Attributes for the backbone model.
       * @param {object} options
       *   An object with the following option:
       * @param {Backbone.collection} options.contextualCollection
       *   The collection of {@link Drupal.contextual.StateModel} models that
       *   represent the contextual links on the page.
       */
      initialize(attrs, options) {
        // Respond to new/removed contextual links.
        this.listenTo(
          options.contextualCollection,
          'reset remove add',
          this.countContextualLinks,
        );
        this.listenTo(
          options.contextualCollection,
          'add',
          this.lockNewContextualLinks,
        );

        // Automatically determine visibility.
        this.listenTo(this, 'change:contextualCount', this.updateVisibility);

        // Whenever edit mode is toggled, lock all contextual links.
        this.listenTo(this, 'change:isViewing', (model, isViewing) => {
          options.contextualCollection.each(contextualModel => {
            contextualModel.set('isLocked', !isViewing);
          });
        });
      },

      /**
       * Tracks the number of contextual link models in the collection.
       *
       * @param {Drupal.contextual.StateModel} contextualModel
       *   The contextual links model that was added or removed.
       * @param {Backbone.Collection} contextualCollection
       *    The collection of contextual link models.
       */
      countContextualLinks(contextualModel, contextualCollection) {
        this.set('contextualCount', contextualCollection.length);
      },

      /**
       * Lock newly added contextual links if edit mode is enabled.
       *
       * @param {Drupal.contextual.StateModel} contextualModel
       *   The contextual links model that was added.
       * @param {Backbone.Collection} [contextualCollection]
       *    The collection of contextual link models.
       */
      lockNewContextualLinks(contextualModel, contextualCollection) {
        if (!this.get('isViewing')) {
          contextualModel.set('isLocked', true);
        }
      },

      /**
       * Automatically updates visibility of the view/edit mode toggle.
       */
      updateVisibility() {
        this.set('isVisible', this.get('contextualCount') > 0);
      },
    },
  );
})(Drupal, Backbone);
