/*****************************************************************************
 * Open MCT Web, Copyright (c) 2014-2015, United States Government
 * as represented by the Administrator of the National Aeronautics and Space
 * Administration. All rights reserved.
 *
 * Open MCT Web is licensed under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0.
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * Open MCT Web includes source code licensed under additional open source
 * licenses. See the Open Source Licenses file (LICENSES.md) included with
 * this source code distribution or the Licensing information page available
 * at runtime from the About dialog for additional information.
 *****************************************************************************/
/*global define*/

define(
    [],
    function () {
        "use strict";

        /**
         * Used to handle telemetry delegation associated with a
         * given domain object.
         */
        function TelemetryDelegator($q) {
            return {
                /**
                 * Promise telemetry-providing objects associated with
                 * this domain object (either the domain object itself,
                 * or the objects it delegates)
                 * @returns {Promise.<DomainObject[]>} domain objects with
                 *          a telemetry capability
                 */
                promiseTelemetryObjects: function (domainObject) {
                    // If object has been cleared, there are no relevant
                    // telemetry-providing domain objects.
                    if (!domainObject) {
                        return $q.when([]);
                    }

                    // Otherwise, try delegation first, and attach the
                    // object itself if it has a telemetry capability.
                    return $q.when(domainObject.useCapability(
                        "delegation",
                        "telemetry"
                    )).then(function (result) {
                        var head = domainObject.hasCapability("telemetry") ?
                                [ domainObject ] : [],
                            tail = result || [];
                        return head.concat(tail);
                    });
                }
            };
        }

        return TelemetryDelegator;
    }
);