/*****************************************************************************
 * 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(
    ["uuid"],
    function (uuid) {
        "use strict";

        /**
         * This class encapsulates the process of copying a domain object
         * and all of its children.
         *
         * @param domainObject The object to copy
         * @param parent The new location of the cloned object tree
         * @param $q
         * @constructor
         */
        function CopyTask (domainObject, parent, policyService, $q){
            this.domainObject = domainObject;
            this.parent = parent;
            this.firstClone = undefined;
            this.$q = $q;
            this.deferred = undefined;
            this.policyService = policyService;
            this.persisted = 0;
            this.clones = [];
        }

        function composeChild(child, parent) {
            //Once copied, associate each cloned
            // composee with its parent clone

            parent.getModel().composition.push(child.getId());

            //Check if the object being composed is a link
            if (!child.getCapability("location").isLink()) {
                child.getModel().location = parent.getId();
            }
        }

        function cloneObjectModel(objectModel) {
            var clone = JSON.parse(JSON.stringify(objectModel));

            /**
             * Reset certain fields.
             */
            //If has a composition, set it to an empty array. Will be
            // recomposed later with the ids of its cloned children.
            if (clone.composition) {
                //Important to set it to an empty array here, otherwise
                // hasCapability("composition") returns false;
                clone.composition = [];
            }
            delete clone.persisted;
            delete clone.modified;
            delete clone.location;

            return clone;
        }

        /**
         * Will persist a list of {@link objectClones}. It will persist all
         * simultaneously, irrespective of order in the list. This may
         * result in automatic request batching by the browser.
         */
        function persistObjects(self) {
            return self.$q.all(self.clones.map(function(clone){
                return clone.getCapability("persistence").persist().then(function(){
                    self.deferred.notify({phase: "copying", totalObjects: self.clones.length, processed: ++self.persisted});
                });
            })).then(function(){
                return self;
            });
        }

        /**
         * Will add a list of clones to the specified parent's composition
         */
        function addClonesToParent(self) {
            return self.firstClone.getCapability("persistence").persist()
                .then(function(){self.parent.getCapability("composition").add(self.firstClone.getId());})
                .then(function(){return self.parent.getCapability("persistence").persist();})
                .then(function(){return self.firstClone;});
        }

        /**
         * Given an array of objects composed by a parent, clone them, then
         * add them to the parent.
         * @private
         * @returns {*}
         */
        CopyTask.prototype.copyComposees = function(composees, clonedParent, originalParent){
            var self = this;

            return (composees || []).reduce(function(promise, composee){
                //If the composee is composed of other
                // objects, chain a promise..
                return promise.then(function(){
                    // ...to recursively copy it (and its children)
                    return self.copy(composee, originalParent).then(function(composee){
                        return composeChild(composee, clonedParent);
                    });
                });}, self.$q.when(undefined)
            );
        };

        /**
         * A recursive function that will perform a bottom-up copy of
         * the object tree with originalObject at the root. Recurses to
         * the farthest leaf, then works its way back up again,
         * cloning objects, and composing them with their child clones
         * as it goes
         * @private
         * @param originalObject
         * @param originalParent
         * @returns {*}
         */
        CopyTask.prototype.copy = function(originalObject, originalParent) {
            var self = this,
                clone;

            //Check if the type of the object being copied allows for
            // creation of new instances. If it does not, then a link to the
            // original will be created instead.
            if (this.policyService.allow("creation", originalObject.getCapability("type"))){
                //create a new clone of the original object. Use the
                // creation capability of the targetParent to create the
                // new clone. This will ensure that the correct persistence
                // space is used.
                clone = this.parent.hasCapability("instantiation") && this.parent.useCapability("instantiation", cloneObjectModel(originalObject.getModel()));

                //Iterate through child tree
                return this.$q.when(originalObject.useCapability('composition')).then(function(composees){
                    self.deferred.notify({phase: "preparing"});
                    //Duplicate the object's children, and their children, and
                    // so on down to the leaf nodes of the tree.
                    //If it is a link, don't both with children
                    return self.copyComposees(composees, clone, originalObject).then(function (){
                        //Add the clone to the list of clones that will
                        //be returned by this function
                        self.clones.push(clone);
                        return clone;
                    });
                });
            } else {
                //Creating a link, no need to iterate children
                return self.$q.when(originalObject);
            }


        };

        /**
         * Will build a graph of an object and all of its child objects in
         * memory
         * @private
         * @param domainObject The original object to be copied
         * @param parent The parent of the original object to be copied
         * @returns {Promise} resolved with an array of clones of the models
         * of the object tree being copied. Copying is done in a bottom-up
         * fashion, so that the last member in the array is a clone of the model
         * object being copied. The clones are all full composed with
         * references to their own children.
         */
        CopyTask.prototype.buildCopyPlan = function() {
            var self = this;

            return this.copy(self.domainObject, self.parent).then(function(domainObjectClone){
                if (domainObjectClone !== self.domainObject) {
                    domainObjectClone.getModel().location = self.parent.getId();
                }
                self.firstClone = domainObjectClone;
                return self;
            });
        };

        /**
         * Execute the copy task with the objects provided in the constructor.
         * @returns {promise} Which will resolve with a clone of the object
         * once complete.
         */
        CopyTask.prototype.perform = function(){
            this.deferred = this.$q.defer();

            this.buildCopyPlan()
                .then(persistObjects)
                .then(addClonesToParent)
                .then(this.deferred.resolve, this.deferred.reject);

            return this.deferred.promise;
        };

        return CopyTask;
    }
);