/*****************************************************************************
 * 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(
    ['./PersistenceFailureDialog', './PersistenceFailureConstants'],
    function (PersistenceFailureDialog, PersistenceFailureConstants) {
        "use strict";

        /**
         * Handle failures to persist domain object models.
         * @param $q Angular's `$q`
         * @param {DialogService} dialogService the dialog service
         * @constructor
         * @memberof platform/persistence/queue
         */
        function PersistenceFailureHandler($q, dialogService) {
            this.$q = $q;
            this.dialogService = dialogService;
        }

        /**
         * Handle persistence failures by providing the user with a
         * dialog summarizing these failures, and giving the option
         * to overwrite/cancel as appropriate.
         * @param {Array} failures persistence failures, as prepared
         *        by PersistenceQueueHandler
         * @memberof platform/persistence/queue.PersistenceFailureHandler#
         */
        PersistenceFailureHandler.prototype.handle = function handleFailures(failures) {
            // Prepare dialog for display
            var dialogModel = new PersistenceFailureDialog(failures),
                revisionErrors = dialogModel.model.revised,
                $q = this.$q;

            // Refresh revision information for the domain object associated
            // with this persistence failure
            function refresh(failure) {
                // Refresh the domain object to the latest from persistence
                return failure.persistence.refresh();
            }

            // Issue a new persist call for the domain object associated with
            // this failure.
            function persist(failure) {
                // Note that we reissue the persist request here, but don't
                // return it, to avoid a circular wait. We trust that the
                // PersistenceQueue will behave correctly on the next round
                // of flushing.
                failure.requeue();
            }

            // Retry persistence (overwrite) for this set of failed attempts
            function retry(failures) {
                var models = {};

                // Cache a copy of the model
                function cacheModel(failure) {
                    // Clone...
                    models[failure.id] = JSON.parse(JSON.stringify(
                        failure.domainObject.getModel()
                    ));
                }

                // Mutate a domain object to restore its model
                function remutate(failure) {
                    var model = models[failure.id];
                    return failure.domainObject.useCapability(
                        "mutation",
                        function () { return model; },
                        model.modified
                    );
                }

                // Cache the object models we might want to save
                failures.forEach(cacheModel);

                // Strategy here:
                // * Cache all of the models we might want to save (above)
                // * Refresh all domain objects (so they are latest versions)
                // * Re-insert the cached domain object models
                // * Invoke persistence again
                return $q.all(failures.map(refresh)).then(function () {
                    return $q.all(failures.map(remutate));
                }).then(function () {
                    return $q.all(failures.map(persist));
                });
            }

            // Discard changes for a failed refresh
            function discard(failure) {
                var persistence =
                    failure.domainObject.getCapability('persistence');
                return persistence.refresh();
            }

            // Discard changes associated with a failed save
            function discardAll(failures) {
                return $q.all(failures.map(discard));
            }

            // Handle user input (did they choose to overwrite?)
            function handleChoice(key) {
                // If so, try again
                if (key === PersistenceFailureConstants.OVERWRITE_KEY) {
                    return retry(revisionErrors);
                } else {
                    return discardAll(revisionErrors);
                }
            }

            // Prompt for user input, the overwrite if they said so.
            return this.dialogService.getUserChoice(dialogModel)
                .then(handleChoice, handleChoice);
        };

        return PersistenceFailureHandler;
    }
);