wikimedia/mediawiki-extensions-Wikibase

/**
 * @license GPL-2.0-or-later
 * @author Adrian Heine <adrian.heine@wikimedia.de>
 */
( function () {
    'use strict';

    var EntityStore = require( './store.EntityStore.js' );

    /**
     * Passes item to the handlers one after the other until it has a resolution
     */
    function asyncFallback( item, handlers ) {
        var deferred = $.Deferred(),
            index = 0;

        function tryNext() {
            if ( handlers.length <= index ) {
                deferred.reject();
                return;
            }
            handlers[ index++ ]( item )
            .fail( tryNext )
            .done( deferred.resolve );
        }

        window.setTimeout( tryNext, 0 );

        return deferred.promise();
    }

    /**
     * Entity store wrapping multiple EntityStore instances.
     *
     * @constructor
     * @extends EntityStore
     *
     * @param {Object[]} stores
     */
    module.exports = util.inherit(
        'WbCombiningEntityStore',
        EntityStore,
        function ( stores ) {
            this._stores = stores;
        },
        {
            /**
             * @type {Object[]}
             */
            _stores: null,

            /**
             * @see EntityStore.get
             */
            get: function ( entityId ) {
                return asyncFallback( entityId, this._stores.map( function ( store ) {
                    return function ( id ) {
                        return store.get( id );
                    };
                } ) );
            }
        } );
}() );