/*****************************************************************************
 * Open MCT, Copyright (c) 2014-2018, United States Government
 * as represented by the Administrator of the National Aeronautics and Space
 * Administration. All rights reserved.
 *
 * Open MCT 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 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.
 *****************************************************************************/

define([
    'objectUtils'
], function (
    objectUtils
) {

    /**
     * Compatibility decorator for New API.
     *
     * When the model service returns no results, this attempts to load
     * the model from the new Object API and returns that instead.  In order
     * to prevent infinite recursion, this only tries to fetch from the API
     * a single time.
     *
     */
    function MissingModelCompatibilityDecorator(api, modelService) {
        this.api = api;
        this.modelService = modelService;
        this.apiFetching = {}; // to prevent loops, if we have already
    }

    /**
     * Fetch a set of ids from the public api and return a promise for their
     * models.  If a model is requested twice, respond with a missing result.
     */
    MissingModelCompatibilityDecorator.prototype.apiFetch = function (ids) {
        const results = {};

        const promises = ids.map(function (id) {
            if (this.apiFetching[id]) {
                return Promise.resolve();
            }

            this.apiFetching[id] = true;

            return this.api.objects.get(objectUtils.parseKeyString(id))
                .then(function (newDO) {
                    results[id] = objectUtils.toOldFormat(newDO);
                });
        }, this);

        return Promise.all(promises).then(function () {
            return results;
        });
    };

    /**
     * Return a promise for model results based on provided ids.  Will attempt
     * to fetch any missing results from the object api.
     */
    MissingModelCompatibilityDecorator.prototype.getModels = function (ids) {
        return this.modelService.getModels(ids)
            .then(function (models) {
                const missingIds = ids.filter(function (id) {
                    return !models[id];
                });

                if (!missingIds.length) {
                    return models;
                }

                return this.apiFetch(missingIds)
                    .then(function (apiResults) {
                        Object.keys(apiResults).forEach(function (k) {
                            models[k] = apiResults[k];
                        });

                        return models;
                    });
            }.bind(this));
    };

    return MissingModelCompatibilityDecorator;
});