Backbone-Relational - AutoFetch support

gistfile1.js

/**
 * Backbone-relational.js 0.5.0
 * (c) 2011 Paul Uithol
 *
 * Backbone-relational may be freely distributed under the MIT license.
 * For details and documentation: https://github.com/PaulUithol/Backbone-relational.
 * Depends on (as in, compeletely useless without) Backbone: https://github.com/documentcloud/backbone.
 */
(function(undefined) {
	/**
	 * CommonJS shim
	 **/
	var _, Backbone, exports;
	if ( typeof window === 'undefined') {
		_ = require('underscore');
		Backbone = require('backbone');
		exports = module.exports = Backbone;
	} else {
		var _ = window._;
		Backbone = window.Backbone;
		exports = window;
	}

	Backbone.Relational = {
		showWarnings : true
	};

	/**
	 * Semaphore mixin; can be used as both binary and counting.
	 **/
	Backbone.Semaphore = {
		_permitsAvailable : null,
		_permitsUsed : 0,

		acquire : function() {
			if (this._permitsAvailable && this._permitsUsed >= this._permitsAvailable) {
				throw new Error('Max permits acquired');
			} else {
				this._permitsUsed++;
			}
		},

		release : function() {
			if (this._permitsUsed === 0) {
				throw new Error('All permits released');
			} else {
				this._permitsUsed--;
			}
		},

		isLocked : function() {
			return this._permitsUsed > 0;
		},

		setAvailablePermits : function(amount) {
			if (this._permitsUsed > amount) {
				throw new Error('Available permits cannot be less than used permits');
			}
			this._permitsAvailable = amount;
		}
	};

	/**
	 * A BlockingQueue that accumulates items while blocked (via 'block'),
	 * and processes them when unblocked (via 'unblock').
	 * Process can also be called manually (via 'process').
	 */
	Backbone.BlockingQueue = function() {
		this._queue = [];
	};
	_.extend(Backbone.BlockingQueue.prototype, Backbone.Semaphore, {
		_queue : null,

		add : function(func) {
			if (this.isBlocked()) {
				this._queue.push(func);
			} else {
				func();
			}
		},

		process : function() {
			while (this._queue && this._queue.length) {
				this._queue.shift()();
			}
		},

		block : function() {
			this.acquire();
		},

		unblock : function() {
			this.release();
			if (!this.isBlocked()) {
				this.process();
			}
		},

		isBlocked : function() {
			return this.isLocked();
		}
	});
	/**
	 * Global event queue. Accumulates external events ('add:<key>', 'remove:<key>' and 'update:<key>')
	 * until the top-level object is fully initialized (see 'Backbone.RelationalModel').
	 */
	Backbone.Relational.eventQueue = new Backbone.BlockingQueue();

	/**
	 * Backbone.Store keeps track of all created (and destruction of) Backbone.RelationalModel.
	 * Handles lookup for relations.
	 */
	Backbone.Store = function() {
		this._collections = [];
		this._reverseRelations = [];
	};
	_.extend(Backbone.Store.prototype, Backbone.Events, {
		_collections : null,
		_reverseRelations : null,

		/**
		 * Add a reverse relation. Is added to the 'relations' property on model's prototype, and to
		 * existing instances of 'model' in the store as well.
		 * @param {object} relation
		 * @param {Backbone.RelationalModel} relation.model
		 * @param {String} relation.type
		 * @param {String} relation.key
		 * @param {String|object} relation.relatedModel
		 */
		addReverseRelation : function(relation) {
			var exists = _.any(this._reverseRelations, function(rel) {
				return _.all(relation, function(val, key) {
					return val === rel[key];
				});
			});

			if (!exists && relation.model && relation.type) {
				this._reverseRelations.push(relation);

				if (!relation.model.prototype.relations) {
					relation.model.prototype.relations = [];
				}
				relation.model.prototype.relations.push(relation);

				this.retroFitRelation(relation);
			}
		},

		/**
		 * Add a 'relation' to all existing instances of 'relation.model' in the store
		 * @param {object} relation
		 */
		retroFitRelation : function(relation) {
			var coll = this.getCollection(relation.model);
			coll.each(function(model) {
				new relation.type(model, relation);
			}, this);
		},

		/**
		 * Find the Store's collection for a certain type of model.
		 * @param {Backbone.RelationalModel} model
		 * @return {Backbone.Collection} A collection if found (or applicable for 'model'), or null
		 */
		getCollection : function(model) {
			var coll = _.detect(this._collections, function(c) {
				// Check if model is the type itself (a ref to the constructor), or is of type c.model
				return model === c.model || model.constructor === c.model;
			});

			if (!coll) {
				coll = this._createCollection(model);
			}

			return coll;
		},

		/**
		 * Find a type on the global object by name. Splits name on dots.
		 * @param {String} name
		 * @return {object}
		 */
		getObjectByName : function(name) {
			var type = _.reduce(name.split('.'), function(memo, val) {
				return memo[val];
			}, exports);
			return type !== exports ? type : null;
		},

		_createCollection : function(type) {
			var coll;

			// If 'type' is an instance, take it's constructor
			if ( type instanceof Backbone.RelationalModel) {
				type = type.constructor;
			}

			// Type should inherit from Backbone.RelationalModel.
			if (type.prototype instanceof Backbone.RelationalModel.prototype.constructor) {
				coll = new Backbone.Collection();
				coll.model = type;

				this._collections.push(coll);
			}

			return coll;
		},

		find : function(type, id) {
			var coll = this.getCollection(type);
			return coll && coll.get(id);
		},

		/**
		 * Add a 'model' to it's appropriate collection. Retain the original contents of 'model.collection'.
		 * @param {Backbone.RelationalModel} model
		 */
		register : function(model) {
			var modelColl = model.collection;
			var coll = this.getCollection(model);
			coll && coll.add(model);
			model.bind('destroy', this.unregister, this);
			model.collection = modelColl;
		},

		/**
		 * Explicitly update a model's id in it's store collection
		 * @param {Backbone.RelationalModel} model
		 */
		update : function(model) {
			var coll = this.getCollection(model);
			coll._onModelEvent('change:' + model.idAttribute, model, coll);
		},

		/**
		 * Remove a 'model' from the store.
		 * @param {Backbone.RelationalModel} model
		 */
		unregister : function(model) {
			model.unbind('destroy', this.unregister);
			var coll = this.getCollection(model);
			coll && coll.remove(model);
		}
	});
	Backbone.Relational.store = new Backbone.Store();

	/**
	 * The main Relation class, from which 'HasOne' and 'HasMany' inherit. Internally, 'relational:<key>' events
	 * are used to regulate addition and removal of models from relations.
	 *
	 * @param {Backbone.RelationalModel} instance
	 * @param {object} options
	 * @param {string} options.key
	 * @param {Backbone.RelationalModel.constructor} options.relatedModel
	 * @param {Boolean|String} [options.includeInJSON=true] Serialize the given attribute for related model(s)' in toJSON,  or just their ids.
	 * @param {Boolean} [options.createModels=true] Create objects from the contents of keys if the object is not found in Backbone.store.
	 * @param {object} [options.reverseRelation] Specify a bi-directional relation. If provided, Relation will reciprocate
	 *    the relation to the 'relatedModel'. Required and optional properties match 'options', except that it also needs
	 *    {Backbone.Relation|String} type ('HasOne' or 'HasMany').
	 */
	Backbone.Relation = function(instance, options) {
		this.instance = instance;
		// Make sure 'options' is sane, and fill with defaults from subclasses and this object's prototype
		options = ( typeof options === 'object' && options ) || {};
		this.reverseRelation = _.defaults(options.reverseRelation || {}, this.options.reverseRelation);
		this.reverseRelation.type = !_.isString(this.reverseRelation.type) ? this.reverseRelation.type : Backbone[this.reverseRelation.type] || Backbone.Relational.store.getObjectByName(this.reverseRelation.type);
		this.model = options.model || this.instance.constructor;
		this.options = _.defaults(options, this.options, Backbone.Relation.prototype.options);

		this.key = this.options.key;

		// 'exports' should be the global object where 'relatedModel' can be found on if given as a string.
		this.relatedModel = this.options.relatedModel;
		if (_.isString(this.relatedModel)) {
			this.relatedModel = Backbone.Relational.store.getObjectByName(this.relatedModel);
		}

		if (!this.checkPreconditions()) {
			return false;
		}

		if (instance) {
			this.keyContents = this.instance.get(this.key);
			// Add this Relation to instance._relations
			this.instance._relations.push(this);
		}

		// Add the reverse relation on 'relatedModel' to the store's reverseRelations
		if (!this.options.isAutoRelation && this.reverseRelation.type && this.reverseRelation.key) {
			Backbone.Relational.store.addReverseRelation(_.defaults({
				isAutoRelation : true,
				model : this.relatedModel,
				relatedModel : this.model,
				reverseRelation : this.options // current relation is the 'reverseRelation' for it's own reverseRelation
			}, this.reverseRelation // Take further properties from this.reverseRelation (type, key, etc.)
			));
		}

		_.bindAll(this, '_modelRemovedFromCollection', '_relatedModelAdded', '_relatedModelRemoved');

		if (instance) {
			this.initialize();

			if (options.autoFetch) {
				this.instance.fetchRelated(options.key, _.isObject(options.autoFetch) ? options.autoFetch : {});
			}

			// When a model in the store is destroyed, check if it is 'this.instance'.
			Backbone.Relational.store.getCollection(this.instance).bind('relational:remove', this._modelRemovedFromCollection);

			// When 'relatedModel' are created or destroyed, check if it affects this relation.
			Backbone.Relational.store.getCollection(this.relatedModel).bind('relational:add', this._relatedModelAdded).bind('relational:remove', this._relatedModelRemoved);
		}
	};
	// Fix inheritance :\
	Backbone.Relation.extend = Backbone.Model.extend;
	// Set up all inheritable **Backbone.Relation** properties and methods.
	_.extend(Backbone.Relation.prototype, Backbone.Events, Backbone.Semaphore, {
		options : {
			createModels : true,
			includeInJSON : true,
			isAutoRelation : false,
			autoFetch : false
		},

		instance : null,
		key : null,
		keyContents : null,
		relatedModel : null,
		reverseRelation : null,
		related : null,

		_relatedModelAdded : function(model, coll, options) {
			// Allow 'model' to set up it's relations, before calling 'tryAddRelated'
			// (which can result in a call to 'addRelated' on a relation of 'model')
			var dit = this;
			model.queue(function() {
				dit.tryAddRelated(model, options);
			});
		},

		_relatedModelRemoved : function(model, coll, options) {
			this.removeRelated(model, options);
		},

		_modelRemovedFromCollection : function(model) {
			if (model === this.instance) {
				this.destroy();
			}
		},

		/**
		 * Check several pre-conditions.
		 * @return {Boolean} True if pre-conditions are satisfied, false if they're not.
		 */
		checkPreconditions : function() {
			var i = this.instance, k = this.key, m = this.model, rm = this.relatedModel, warn = Backbone.Relational.showWarnings;
			if (!m || !k || !rm) {
				warn && typeof console !== 'undefined' && console.warn('Relation=%o; no model, key or relatedModel (%o, %o, %o)', this, k, rm);
				return false;
			}
			// Check if the type in 'relatedModel' inherits from Backbone.RelationalModel
			if (!(m.prototype instanceof Backbone.RelationalModel.prototype.constructor )) {
				warn && typeof console !== 'undefined' && console.warn('Relation=%o; model does not inherit from Backbone.RelationalModel (%o)', this, i);
				return false;
			}
			// Check if the type in 'relatedModel' inherits from Backbone.RelationalModel
			if (!(rm.prototype instanceof Backbone.RelationalModel.prototype.constructor )) {
				warn && typeof console !== 'undefined' && console.warn('Relation=%o; relatedModel does not inherit from Backbone.RelationalModel (%o)', this, rm);
				return false;
			}
			// Check if this is not a HasMany, and the reverse relation is HasMany as well
			if (this instanceof Backbone.HasMany && this.reverseRelation.type === Backbone.HasMany.prototype.constructor) {
				warn && typeof console !== 'undefined' && console.warn('Relation=%o; relation is a HasMany, and the reverseRelation is HasMany as well.', this);
				return false;
			}

			if (i) {
				// Check if we're not attempting to create a duplicate relationship
				if (i._relations.length) {
					var exists = _.any(i._relations, function(rel) {
						var hasReverseRelation = this.reverseRelation.key && rel.reverseRelation.key;
						return rel.relatedModel === rm && rel.key === k && (!hasReverseRelation || this.reverseRelation.key === rel.reverseRelation.key );
					}, this);

					if (exists) {
						warn && typeof console !== 'undefined' && console.warn('Relation=%o between instance=%o.%s and relatedModel=%o.%s already exists', this, i, k, rm, this.reverseRelation.key);
						return false;
					}
				}
			}
			return true;
		},

		setRelated : function(related, options) {
			this.related = related;
			var value = {};
			value[this.key] = related;
			this.instance.acquire();
			this.instance.set(value, _.defaults(options || {}, {
				silent : true
			}));
			this.instance.release();
		},

		createModel : function(item) {
			if (this.options.createModels && typeof (item ) === 'object') {
				return new this.relatedModel(item);
			}
		},

		/**
		 * Determine if a relation (on a different RelationalModel) is the reverse
		 * relation of the current one.
		 */
		_isReverseRelation : function(relation) {
			if (relation.instance instanceof this.relatedModel && this.reverseRelation.key === relation.key && this.key === relation.reverseRelation.key) {
				return true;
			}
			return false;
		},

		/**
		 * Get the reverse relations (pointing back to 'this.key' on 'this.instance') for the currently related model(s).
		 * @param {Backbone.RelationalModel} [model] Get the reverse relations for a specific model.
		 *    If not specified, 'this.related' is used.
		 */
		getReverseRelations : function(model) {
			var reverseRelations = [];
			// Iterate over 'model', 'this.related.models' (if this.related is a Backbone.Collection), or wrap 'this.related' in an array.
			var models = !_.isUndefined(model) ? [model] : this.related && (this.related.models || [this.related] );
			_.each(models, function(related) {
				_.each(related.getRelations(), function(relation) {
					if (this._isReverseRelation(relation)) {
						reverseRelations.push(relation);
					}
				}, this);
			}, this);

			return reverseRelations;
		},

		/**
		 * Rename options.silent, so add/remove events propagate properly.
		 * (for example in HasMany, from 'addRelated'->'handleAddition')
		 */
		sanitizeOptions : function(options) {
			options || ( options = {} );
			if (options.silent) {
				options = _.extend({}, options, {
					silentChange : true
				});
				delete options.silent;
			}
			return options;
		},

		// Cleanup. Get reverse relation, call removeRelated on each.
		destroy : function() {
			Backbone.Relational.store.getCollection(this.instance).unbind('relational:remove', this._modelRemovedFromCollection);

			Backbone.Relational.store.getCollection(this.relatedModel).unbind('relational:add', this._relatedModelAdded).unbind('relational:remove', this._relatedModelRemoved);

			_.each(this.getReverseRelations(), function(relation) {
				relation.removeRelated(this.instance);
			}, this);
		}
	});

	Backbone.HasOne = Backbone.Relation.extend({
		options : {
			reverseRelation : {
				type : 'HasMany'
			}
		},

		initialize : function() {
			_.bindAll(this, 'onChange');

			this.instance.bind('relational:change:' + this.key, this.onChange);

			var model = this.findRelated({
				silent : true
			});
			this.setRelated(model);

			// Notify new 'related' object of the new relation.
			var dit = this;
			_.each(dit.getReverseRelations(), function(relation) {
				relation.addRelated(dit.instance);
			});
		},

		findRelated : function(options) {
			var item = this.keyContents;
			var model = null;

			if ( item instanceof this.relatedModel) {
				model = item;
			} else if (item && (_.isString(item) || _.isNumber(item) || typeof (item ) === 'object' )) {
				// Try to find an instance of the appropriate 'relatedModel' in the store, or create it
				var id = _.isString(item) || _.isNumber(item) ? item : item[this.relatedModel.prototype.idAttribute];
				model = Backbone.Relational.store.find(this.relatedModel, id);
				if (model && _.isObject(item)) {
					model.set(item, options);
				} else if (!model) {
					model = this.createModel(item);
				}
			}

			return model;
		},

		/**
		 * If the key is changed, notify old & new reverse relations and initialize the new relation
		 */
		onChange : function(model, attr, options) {
			// Don't accept recursive calls to onChange (like onChange->findRelated->createModel->initializeRelations->addRelated->onChange)
			if (this.isLocked()) {
				return;
			}
			this.acquire();
			options = this.sanitizeOptions(options);

			// 'options._related' is set by 'addRelated'/'removeRelated'. If it is set, the change
			// is the result of a call from a relation. If it's not, the change is the result of
			// a 'set' call on this.instance.
			var changed = _.isUndefined(options._related);
			var oldRelated = changed ? this.related : options._related;

			if (changed) {
				this.keyContents = attr;

				// Set new 'related'
				if ( attr instanceof this.relatedModel) {
					this.related = attr;
				} else if (attr) {
					var related = this.findRelated(options);
					this.setRelated(related);
				} else {
					this.setRelated(null);
				}
			}

			// Notify old 'related' object of the terminated relation
			if (oldRelated && this.related !== oldRelated) {
				_.each(this.getReverseRelations(oldRelated), function(relation) {
					relation.removeRelated(this.instance, options);
				}, this);
			}

			// Notify new 'related' object of the new relation. Note we do re-apply even if this.related is oldRelated;
			// that can be necessary for bi-directional relations if 'this.instance' was created after 'this.related'.
			// In that case, 'this.instance' will already know 'this.related', but the reverse might not exist yet.
			_.each(this.getReverseRelations(), function(relation) {
				relation.addRelated(this.instance, options);
			}, this);

			// Fire the 'update:<key>' event if 'related' was updated
			if (!options.silentChange && this.related !== oldRelated) {
				var dit = this;
				Backbone.Relational.eventQueue.add(function() {
					dit.instance.trigger('update:' + dit.key, dit.instance, dit.related, options);
				});
			}
			this.release();
		},

		/**
		 * If a new 'this.relatedModel' appears in the 'store', try to match it to the last set 'keyContents'
		 */
		tryAddRelated : function(model, options) {
			if (this.related) {
				return;
			}
			options = this.sanitizeOptions(options);

			var item = this.keyContents;
			if (item && (_.isString(item) || _.isNumber(item) || typeof (item ) === 'object' )) {
				var id = _.isString(item) || _.isNumber(item) ? item : item[this.relatedModel.prototype.idAttribute];
				if (model.id === id) {
					this.addRelated(model, options);
				}
			}
		},

		addRelated : function(model, options) {
			if (model !== this.related) {
				var oldRelated = this.related || null;
				this.setRelated(model);
				this.onChange(this.instance, model, {
					_related : oldRelated
				});
			}
		},

		removeRelated : function(model, options) {
			if (!this.related) {
				return;
			}

			if (model === this.related) {
				var oldRelated = this.related || null;
				this.setRelated(null);
				this.onChange(this.instance, model, {
					_related : oldRelated
				});
			}
		}
	});

	Backbone.HasMany = Backbone.Relation.extend({
		collectionType : null,

		options : {
			reverseRelation : {
				type : 'HasOne'
			},
			collectionType : Backbone.Collection,
			collectionKey : true
		},

		initialize : function() {
			_.bindAll(this, 'onChange', 'handleAddition', 'handleRemoval', 'handleReset');
			this.instance.bind('relational:change:' + this.key, this.onChange);

			// Handle a custom 'collectionType'
			this.collectionType = this.options.collectionType;
			if (_(this.collectionType).isString()) {
				this.collectionType = Backbone.Relational.store.getObjectByName(this.collectionType);
			}
			if (!this.collectionType.prototype instanceof Backbone.Collection.prototype.constructor) {
				throw new Error('collectionType must inherit from Backbone.Collection');
			}

			this.setRelated(this.prepareCollection(new this.collectionType()));
			this.findRelated({
				silent : true
			});
		},

		prepareCollection : function(collection) {
			if (this.related) {
				this.related.unbind('relational:add', this.handleAddition).unbind('relational:remove', this.handleRemoval).unbind('relational:reset', this.handleReset)
			}

			collection.reset();
			collection.model = this.relatedModel;

			if (this.options.collectionKey) {
				var key = this.options.collectionKey === true ? this.options.reverseRelation.key : this.options.collectionKey;

				if (collection[key] && collection[key] !== this.instance) {
					if (Backbone.Relational.showWarnings && typeof console !== 'undefined') {
						console.warn('Relation=%o; collectionKey=%s already exists on collection=%o', this, key, this.options.collectionKey);
					}
				} else {
					collection[key] = this.instance;
				}
			}

			collection.bind('relational:add', this.handleAddition).bind('relational:remove', this.handleRemoval).bind('relational:reset', this.handleReset);

			return collection;
		},

		findRelated : function(options) {
			if (this.keyContents) {
				// Handle cases the an API/user supplies just an Object/id instead of an Array
				this.keyContents = _.isArray(this.keyContents) ? this.keyContents : [this.keyContents];

				// Try to find instances of the appropriate 'relatedModel' in the store
				_.each(this.keyContents, function(item) {
					var id = _.isString(item) || _.isNumber(item) ? item : item[this.relatedModel.prototype.idAttribute];

					var model = Backbone.Relational.store.find(this.relatedModel, id);
					if (model && _.isObject(item)) {
						model.set(item, options);
					} else if (!model) {
						model = this.createModel(item);
					}

					if (model && !this.related.getByCid(model) && !this.related.get(model)) {
						this.related.add(model);
					}
				}, this);
			}
		},

		/**
		 * If the key is changed, notify old & new reverse relations and initialize the new relation
		 */
		onChange : function(model, attr, options) {
			options = this.sanitizeOptions(options);
			this.keyContents = attr;

			// Notify old 'related' object of the terminated relation
			_.each(this.getReverseRelations(), function(relation) {
				relation.removeRelated(this.instance, options);
			}, this);

			// Replace 'this.related' by 'attr' if it is a Backbone.Collection
			if ( attr instanceof Backbone.Collection) {
				this.prepareCollection(attr);
				this.related = attr;
			}
			// Otherwise, 'attr' should be an array of related object ids.
			// Re-use the current 'this.related' if it is a Backbone.Collection.
			else {
				var coll = this.related instanceof Backbone.Collection ? this.related : new this.collectionType();
				this.setRelated(this.prepareCollection(coll));
				this.findRelated(options);
			}

			// Notify new 'related' object of the new relation
			_.each(this.getReverseRelations(), function(relation) {
				relation.addRelated(this.instance, options);
			}, this);

			var dit = this;
			Backbone.Relational.eventQueue.add(function() {
				!options.silentChange && dit.instance.trigger('update:' + dit.key, dit.instance, dit.related, options);
			});
		},

		tryAddRelated : function(model, options) {
			options = this.sanitizeOptions(options);
			if (!this.related.getByCid(model) && !this.related.get(model)) {
				// Check if this new model was specified in 'this.keyContents'
				var item = _.any(this.keyContents, function(item) {
					var id = _.isString(item) || _.isNumber(item) ? item : item[this.relatedModel.prototype.idAttribute];
					return id && id === model.id;
				}, this);

				if (item) {
					this.related.add(model, options);
				}
			}
		},

		/**
		 * When a model is added to a 'HasMany', trigger 'add' on 'this.instance' and notify reverse relations.
		 * (should be 'HasOne', must set 'this.instance' as their related).
		 */
		handleAddition : function(model, coll, options) {
			//console.debug('handleAddition called; args=%o', arguments);
			// Make sure the model is in fact a valid model before continuing.
			// (it can be invalid as a result of failing validation in Backbone.Collection._prepareModel)
			if (!( model instanceof Backbone.Model )) {
				return;
			}

			options = this.sanitizeOptions(options);

			_.each(this.getReverseRelations(model), function(relation) {
				relation.addRelated(this.instance, options);
			}, this);

			// Only trigger 'add' once the newly added model is initialized (so, has it's relations set up)
			var dit = this;
			Backbone.Relational.eventQueue.add(function() {
				!options.silentChange && dit.instance.trigger('add:' + dit.key, model, dit.related, options);
			});
		},

		/**
		 * When a model is removed from a 'HasMany', trigger 'remove' on 'this.instance' and notify reverse relations.
		 * (should be 'HasOne', which should be nullified)
		 */
		handleRemoval : function(model, coll, options) {
			//console.debug('handleRemoval called; args=%o', arguments);
			if (!( model instanceof Backbone.Model )) {
				return;
			}

			options = this.sanitizeOptions(options);

			_.each(this.getReverseRelations(model), function(relation) {
				relation.removeRelated(this.instance, options);
			}, this);

			var dit = this;
			Backbone.Relational.eventQueue.add(function() {
				!options.silentChange && dit.instance.trigger('remove:' + dit.key, model, dit.related, options);
			});
		},

		handleReset : function(coll, options) {
			options = this.sanitizeOptions(options);

			var dit = this;
			Backbone.Relational.eventQueue.add(function() {
				!options.silentChange && dit.instance.trigger('reset:' + dit.key, dit.related, options);
			});
		},

		addRelated : function(model, options) {
			var dit = this;
			model.queue(function() {// Queued to avoid errors for adding 'model' to the 'this.related' set twice
				if (dit.related && !dit.related.getByCid(model) && !dit.related.get(model)) {
					dit.related.add(model, options);
				}
			});
		},

		removeRelated : function(model, options) {
			if (this.related.getByCid(model) || this.related.get(model)) {
				this.related.remove(model, options);
			}
		}
	});

	/**
	 * A type of Backbone.Model that also maintains relations to other models and collections.
	 * New events when compared to the original:
	 *  - 'add:<key>' (model, related collection, options)
	 *  - 'remove:<key>' (model, related collection, options)
	 *  - 'update:<key>' (model, related model or collection, options)
	 */
	Backbone.RelationalModel = Backbone.Model.extend({
		relations : null, // Relation descriptions on the prototype
		_relations : null, // Relation instances
		_isInitialized : false,
		_deferProcessing : false,
		_queue : null,

		constructor : function(attributes, options) {
			// Nasty hack, for cases like 'model.get( <HasMany key> ).add( item )'.
			// Defer 'processQueue', so that when 'Relation.createModels' is used we:
			// a) Survive 'Backbone.Collection.add'; this takes care we won't error on "can't add model to a set twice"
			//    (by creating a model from properties, having the model add itself to the collection via one of
			//    it's relations, then trying to add it to the collection).
			// b) Trigger 'HasMany' collection events only after the model is really fully set up.
			// Example that triggers both a and b: "p.get('jobs').add( { company: c, person: p } )".
			var dit = this;
			if (options && options.collection) {
				this._deferProcessing = true;

				var processQueue = function(model) {
					if (model === dit) {
						dit._deferProcessing = false;
						dit.processQueue();
						options.collection.unbind('relational:add', processQueue);
					}
				};
				options.collection.bind('relational:add', processQueue);

				// So we do process the queue eventually, regardless of whether this model really gets added to 'options.collection'.
				_.defer(function() {
					processQueue(dit);
				});
			}

			this._queue = new Backbone.BlockingQueue();
			this._queue.block();
			Backbone.Relational.eventQueue.block();

			Backbone.Model.prototype.constructor.apply(this, arguments);

			// Try to run the global queue holding external events
			Backbone.Relational.eventQueue.unblock();
		},

		/**
		 * Override 'trigger' to queue 'change' and 'change:*' events
		 */
		trigger : function(eventName) {
			if (eventName.length > 5 && 'change' === eventName.substr(0, 6)) {
				var dit = this, args = arguments;
				Backbone.Relational.eventQueue.add(function() {
					Backbone.Model.prototype.trigger.apply(dit, args);
				});
			} else {
				Backbone.Model.prototype.trigger.apply(this, arguments);
			}

			return this;
		},

		/**
		 * Initialize Relations present in this.relations; determine the type (HasOne/HasMany), then creates a new instance.
		 * Invoked in the first call so 'set' (which is made from the Backbone.Model constructor).
		 */
		initializeRelations : function() {
			this.acquire();
			// Setting up relations often also involve calls to 'set', and we only want to enter this function once
			this._relations = [];

			_.each(this.relations, function(rel) {
				var type = !_.isString(rel.type) ? rel.type : Backbone[rel.type] || Backbone.Relational.store.getObjectByName(rel.type);
				if (type && type.prototype instanceof Backbone.Relation.prototype.constructor) {
					new type(this, rel);
					// Also pushes the new Relation into _relations
				} else {
					Backbone.Relational.showWarnings && typeof console !== 'undefined' && console.warn('Relation=%o; missing or invalid type!', rel);
				}
			}, this);

			this._isInitialized = true;
			this.release();
			this.processQueue();
		},

		/**
		 * When new values are set, notify this model's relations (also if options.silent is set).
		 * (Relation.setRelated locks this model before calling 'set' on it to prevent loops)
		 */
		updateRelations : function(options) {
			if (this._isInitialized && !this.isLocked()) {
				_.each(this._relations, function(rel) {
					var val = this.attributes[rel.key];
					if (rel.related !== val) {
						this.trigger('relational:change:' + rel.key, this, val, options || {});
					}
				}, this);
			}
		},

		/**
		 * Either add to the queue (if we're not initialized yet), or execute right away.
		 */
		queue : function(func) {
			this._queue.add(func);
		},

		/**
		 * Process _queue
		 */
		processQueue : function() {
			if (this._isInitialized && !this._deferProcessing && this._queue.isBlocked()) {
				this._queue.unblock();
			}
		},

		/**
		 * Get a specific relation.
		 * @param key {string} The relation key to look for.
		 * @return {Backbone.Relation} An instance of 'Backbone.Relation', if a relation was found for 'key', or null.
		 */
		getRelation : function(key) {
			return _.detect(this._relations, function(rel) {
				if (rel.key === key) {
					return true;
				}
			}, this);
		},

		/**
		 * Get all of the created relations.
		 * @return {Backbone.Relation[]}
		 */
		getRelations : function() {
			return this._relations;
		},

		fetch : function(options) {
			console.log('overriden fetch')
			var that = this;
			var existingSuccess = options.success;
			options.success = function(arg) {
				_.each(that._relations, function(relation) {
					that.fetchRelated(relation.key, _.isObject(relation.options.autoFetch) ? relation.options.autoFetch : {})
				});
				if (existingSuccess)
					existingSuccess(arg);
			};
			return Backbone.Model.prototype.fetch.call(this, options);
		},

		/**
		 * Retrieve related objects.
		 * @param key {string} The relation key to fetch models for.
		 * @param options {object} Options for 'Backbone.Model.fetch' and 'Backbone.sync'.
		 * @return {jQuery.when[]} An array of request objects
		 */
		fetchRelated : function(key, options) {
			options || ( options = {} );
			var setUrl, requests = [], rel = this.getRelation(key), keyContents = rel && rel.keyContents, toFetch = keyContents && _.select(_.isArray(keyContents) ? keyContents : [keyContents], function(item) {
				var id = _.isString(item) || _.isNumber(item) ? item : item[rel.relatedModel.prototype.idAttribute];
				return id;
				/*&& !Backbone.Relational.store.find( rel.relatedModel, id );*/
			}, this);

			if (toFetch && toFetch.length) {
				// Create a model for each entry in 'keyContents' that is to be fetched
				var models = _.map(toFetch, function(item) {
					var model;

					if ( typeof (item ) === 'object') {
						model = new rel.relatedModel(item);
					} else {
						var attrs = {};
						attrs[rel.relatedModel.prototype.idAttribute] = item;
						model = new rel.relatedModel(attrs);
					}

					return model;
				}, this);

				// Try if the 'collection' can provide a url to fetch a set of models in one request.
				if (rel.related instanceof Backbone.Collection && _.isFunction(rel.related.url)) {
					setUrl = rel.related.url(models);
				}

				// An assumption is that when 'Backbone.Collection.url' is a function, it can handle building of set urls.
				// To make sure it can, test if the url we got by supplying a list of models to fetch is different from
				// the one supplied for the default fetch action (without args to 'url').
				if (setUrl && setUrl !== rel.related.url()) {
					var opts = _.defaults({
						error : function() {
							var args = arguments;
							_.each(models, function(model) {
								model.trigger('destroy', model, model.collection, options);
								options.error && options.error.apply(model, args);
							});
						},
						url : setUrl
					}, options, {
						add : true
					});

					requests = [rel.related.fetch(opts)];
				} else {
					requests = _.map(models, function(model) {
						var opts = _.defaults({
							error : function() {
								model.trigger('destroy', model, model.collection, options);
								options.error && options.error.apply(model, arguments);
							}
						}, options);
						return model.fetch(opts);
					}, this);
				}
			}

			return requests;
		},

		set : function(key, value, options) {
			Backbone.Relational.eventQueue.block();

			// Duplicate backbone's behavior to allow separate key/value parameters, instead of a single 'attributes' object
			var attributes;
			if (_.isObject(key) || key == null) {
				attributes = key;
				options = value;
			} else {
				attributes = {};
				attributes[key] = value;
			}

			var result = Backbone.Model.prototype.set.apply(this, arguments);

			// 'set' is called quite late in 'Backbone.Model.prototype.constructor', but before 'initialize'.
			// Ideal place to set up relations :)
			if (!this._isInitialized && !this.isLocked()) {
				Backbone.Relational.store.register(this);
				this.initializeRelations();
			}
			// Update the 'idAttribute' in Backbone.store if; we don't want it to miss an 'id' update due to {silent:true}
			else if (attributes && this.idAttribute in attributes) {
				Backbone.Relational.store.update(this);
			}

			if (attributes) {
				this.updateRelations(options);
			}

			// Try to run the global queue holding external events
			Backbone.Relational.eventQueue.unblock();

			return result;
		},

		unset : function(attribute, options) {
			Backbone.Relational.eventQueue.block();

			var result = Backbone.Model.prototype.unset.apply(this, arguments);
			this.updateRelations(options);

			// Try to run the global queue holding external events
			Backbone.Relational.eventQueue.unblock();

			return result;
		},

		clear : function(options) {
			Backbone.Relational.eventQueue.block();

			var result = Backbone.Model.prototype.clear.apply(this, arguments);
			this.updateRelations(options);

			// Try to run the global queue holding external events
			Backbone.Relational.eventQueue.unblock();

			return result;
		},

		/**
		 * Override 'change', so the change will only execute after 'set' has finised (relations are updated),
		 * and 'previousAttributes' will be available when the event is fired.
		 */
		change : function(options) {
			var dit = this;
			Backbone.Relational.eventQueue.add(function() {
				Backbone.Model.prototype.change.apply(dit, arguments);
			});
		},

		clone : function() {
			var attributes = _.clone(this.attributes);
			if (!_.isUndefined(attributes[this.idAttribute])) {
				attributes[this.idAttribute] = null;
			}

			_.each(this.getRelations(), function(rel) {
				delete attributes[rel.key];
			});

			return new this.constructor(attributes);
		},

		/**
		 * Convert relations to JSON, omits them when required
		 */
		toJSON : function() {
			// If this Model has already been fully serialized in this branch once, return to avoid loops
			if (this.isLocked()) {
				return this.id;
			}

			this.acquire();
			var json = Backbone.Model.prototype.toJSON.call(this);

			_.each(this._relations, function(rel) {
				var value = json[rel.key];

				if (rel.options.includeInJSON === true && value && _.isFunction(value.toJSON)) {
					json[rel.key] = value.toJSON();
				} else if (_.isString(rel.options.includeInJSON)) {
					if ( value instanceof Backbone.Collection) {
						json[rel.key] = value.pluck(rel.options.includeInJSON);
					} else if ( value instanceof Backbone.Model) {
						json[rel.key] = value.get(rel.options.includeInJSON);
					}
				} else {
					delete json[rel.key];
				}
			}, this);

			this.release();
			return json;
		}
	});
	_.extend(Backbone.RelationalModel.prototype, Backbone.Semaphore);

	/**
	 * Override Backbone.Collection.add, so objects fetched from the server multiple times will
	 * update the existing Model. Also, trigger 'relational:add'.
	 */
	var add = Backbone.Collection.prototype.add;
	Backbone.Collection.prototype.add = function(models, options) {
		options || ( options = {});
		if (!_.isArray(models)) {
			models = [models];
		}

		//console.debug( 'calling add on coll=%o; model=%o, options=%o', this, models, options );
		_.each(models, function(model) {
			if (!( model instanceof Backbone.Model )) {
				// Try to find 'model' in Backbone.store. If it already exists, set the new properties on it.
				var existingModel = Backbone.Relational.store.find(this.model, model[this.model.prototype.idAttribute]);
				if (existingModel) {
					existingModel.set(model, options);
					model = existingModel;
				} else {
					model = Backbone.Collection.prototype._prepareModel.call(this, model, options);
				}
			}

			if ( model instanceof Backbone.Model && !this.get(model) && !this.getByCid(model)) {
				add.call(this, model, options);
				this.trigger('relational:add', model, this, options);
			}
		}, this);

		return this;
	};

	/**
	 * Override 'Backbone.Collection.remove' to trigger 'relational:remove'.
	 */
	var remove = Backbone.Collection.prototype.remove;
	Backbone.Collection.prototype.remove = function(models, options) {
		options || ( options = {});
		if (!_.isArray(models)) {
			models = [models];
		}

		//console.debug('calling remove on coll=%o; models=%o, options=%o', this, models, options );
		_.each(models, function(model) {
			model = this.getByCid(model) || this.get(model);

			if ( model instanceof Backbone.Model) {
				remove.call(this, model, options);
				this.trigger('relational:remove', model, this, options);
			}
		}, this);

		return this;
	};

	/**
	 * Override 'Backbone.Collection.reset' to trigger 'relational:reset'.
	 */
	var reset = Backbone.Collection.prototype.reset;
	Backbone.Collection.prototype.reset = function(models, options) {
		reset.call(this, models, options);
		this.trigger('relational:reset', models, options);

		return this;
	};

	/**
	 * Override 'Backbone.Collection.trigger' so 'add', 'remove' and 'reset' events are queued until relations
	 * are ready.
	 */
	var _trigger = Backbone.Collection.prototype.trigger;
	Backbone.Collection.prototype.trigger = function(eventName) {
		if (eventName === 'add' || eventName === 'remove' || eventName === 'reset') {
			var dit = this, args = arguments;
			Backbone.Relational.eventQueue.add(function() {
				_trigger.apply(dit, args);
			});
		} else {
			_trigger.apply(this, arguments);
		}

		return this;
	};

	// Override .extend() to check for reverseRelations to initialize.
	Backbone.RelationalModel.extend = function(protoProps, classProps) {
		var child = Backbone.Model.extend.apply(this, arguments);

		var relations = (protoProps && protoProps.relations ) || [];
		_.each(relations, function(rel) {
			if (rel.reverseRelation) {
				rel.model = child;

				var preInitialize = true;
				if (_.isString(rel.relatedModel)) {
					/**
					 * The related model might not be defined for two reasons
					 *  1. it never gets defined, e.g. a typo
					 *  2. it is related to itself
					 * In neither of these cases do we need to pre-initialize reverse relations.
					 */
					var relatedModel = Backbone.Relational.store.getObjectByName(rel.relatedModel);
					preInitialize = relatedModel && (relatedModel.prototype instanceof Backbone.RelationalModel.prototype.constructor );
				}

				var type = !_.isString(rel.type) ? rel.type : Backbone[rel.type] || Backbone.Relational.store.getObjectByName(rel.type);
				if (preInitialize && type && type.prototype instanceof Backbone.Relation.prototype.constructor) {
					new type(null, rel);
				}
			}
		});

		return child;
	};

})();