File: app/js/lazy-model-list.js

            /**
            Provides the LazyModelList class, which is a ModelList subclass that manages
            plain objects instead of fully instantiated model instances.
            
            @module app
            @submodule lazy-model-list
            @since 3.6.0
            **/
            
            /**
            LazyModelList is a subclass of ModelList that maintains a list of plain
            JavaScript objects rather than a list of Model instances. This makes it
            well-suited for managing large amounts of data (on the order of thousands of
            items) that would tend to bog down a vanilla ModelList.
            
            The API presented by LazyModelList is the same as that of ModelList, except that
            in every case where ModelList would provide a Model instance, LazyModelList
            provides a plain JavaScript object. LazyModelList also provides a `revive()`
            method that can convert the plain object at a given index into a full Model
            instance.
            
            Since the items stored in a LazyModelList are plain objects and not full Model
            instances, there are a few caveats to be aware of:
            
              * Since items are plain objects and not Model instances, they contain
                properties rather than Model attributes. To retrieve a property, use
                `item.foo` rather than `item.get('foo')`. To set a property, use
                `item.foo = 'bar'` rather than `item.set('foo', 'bar')`.
            
              * Model attribute getters and setters aren't supported, since items in the
                LazyModelList are stored and manipulated as plain objects with simple
                properties rather than YUI attributes.
            
              * Changes made to the plain object version of an item will not trigger or
                bubble up Model `change` events. However, once an item is revived into a
                full Model using the `revive()` method, changes to that Model instance
                will trigger and bubble change events as expected.
            
              * Custom `idAttribute` fields are not supported.
            
              * `id` and `clientId` properties _are_ supported. If an item doesn't have a
                `clientId` property, one will be generated automatically when the item is
                added to a LazyModelList.
            
            LazyModelList is generally much more memory efficient than ModelList when
            managing large numbers of items, and adding/removing items is significantly
            faster. However, the tradeoff is that LazyModelList is only well-suited for
            storing very simple items without complex attributes, and consumers must
            explicitly revive items into full Model instances as needed (this is not done
            transparently for performance reasons).
            
            @class LazyModelList
            @extends ModelList
            @constructor
            @since 3.6.0
            **/
            
            var AttrProto = Y.Attribute.prototype,
                GlobalEnv = YUI.namespace('Env.Model'),
                Lang      = Y.Lang,
                YArray    = Y.Array,
            
                EVT_ADD   = 'add',
                EVT_ERROR = 'error',
                EVT_RESET = 'reset';
            
            Y.LazyModelList = Y.Base.create('lazyModelList', Y.ModelList, [], {
                // -- Lifecycle ------------------------------------------------------------
                initializer: function () {
                    this.after('*:change', this._afterModelChange);
                },
            
                // -- Public Methods -------------------------------------------------------
            
                /**
                Deletes the specified model from the model cache to release memory. The
                model won't be destroyed or removed from the list, just freed from the
                cache; it can still be instantiated again using `revive()`.
            
                If no model or model index is specified, all cached models in this list will
                be freed.
            
                Note: Specifying an index is faster than specifying a model instance, since
                the latter requires an `indexOf()` call.
            
                @method free
                @param {Model|Number} [model] Model or index of the model to free. If not
                    specified, all instantiated models in this list will be freed.
                @chainable
                @see revive()
                **/
                free: function (model) {
                    var index;
            
                    if (model) {
                        index = Lang.isNumber(model) ? model : this.indexOf(model);
            
                        if (index >= 0) {
                            // We don't detach the model because it's not being removed from
                            // the list, just being freed from memory. If something else
                            // still holds a reference to it, it may still bubble events to
                            // the list, but that's okay.
                            //
                            // `this._models` is a sparse array, which ensures that the
                            // indices of models and items match even if we don't have model
                            // instances for all items.
                            delete this._models[index];
                        }
                    } else {
                        this._models = [];
                    }
            
                    return this;
                },
            
                /**
                Overrides ModelList#get() to return a map of property values rather than
                performing attribute lookups.
            
                @method get
                @param {String} name Property name.
                @return {String[]} Array of property values.
                @see ModelList.get()
                **/
                get: function (name) {
                    if (this.attrAdded(name)) {
                        return AttrProto.get.apply(this, arguments);
                    }
            
                    return YArray.map(this._items, function (item) {
                        return item[name];
                    });
                },
            
                /**
                Overrides ModelList#getAsHTML() to return a map of HTML-escaped property
                values rather than performing attribute lookups.
            
                @method getAsHTML
                @param {String} name Property name.
                @return {String[]} Array of HTML-escaped property values.
                @see ModelList.getAsHTML()
                **/
                getAsHTML: function (name) {
                    if (this.attrAdded(name)) {
                        return Y.Escape.html(AttrProto.get.apply(this, arguments));
                    }
            
                    return YArray.map(this._items, function (item) {
                        return Y.Escape.html(item[name]);
                    });
                },
            
                /**
                Overrides ModelList#getAsURL() to return a map of URL-encoded property
                values rather than performing attribute lookups.
            
                @method getAsURL
                @param {String} name Property name.
                @return {String[]} Array of URL-encoded property values.
                @see ModelList.getAsURL()
                **/
                getAsURL: function (name) {
                    if (this.attrAdded(name)) {
                        return encodeURIComponent(AttrProto.get.apply(this, arguments));
                    }
            
                    return YArray.map(this._items, function (item) {
                        return encodeURIComponent(item[name]);
                    });
                },
            
                /**
                Returns the index of the given object or Model instance in this
                LazyModelList.
            
                @method indexOf
                @param {Model|Object} needle The object or Model instance to search for.
                @return {Number} Item index, or `-1` if not found.
                @see ModelList.indexOf()
                **/
                indexOf: function (model) {
                    return YArray.indexOf(model && model._isYUIModel ?
                        this._models : this._items, model);
                },
            
                /**
                Overrides ModelList#reset() to work with plain objects.
            
                @method reset
                @param {Object[]|Model[]|ModelList} [models] Models to add.
                @param {Object} [options] Options.
                @chainable
                @see ModelList.reset()
                **/
                reset: function (items, options) {
                    items || (items  = []);
                    options || (options = {});
            
                    var facade = Y.merge({src: 'reset'}, options);
            
                    // Convert `items` into an array of plain objects, since we don't want
                    // model instances.
                    items = items._isYUIModelList ? items.map(this._modelToObject) :
                        YArray.map(items, this._modelToObject);
            
                    facade.models = items;
            
                    if (options.silent) {
                        this._defResetFn(facade);
                    } else {
                        // Sort the items before firing the reset event.
                        if (this.comparator) {
                            items.sort(Y.bind(this._sort, this));
                        }
            
                        this.fire(EVT_RESET, facade);
                    }
            
                    return this;
                },
            
                /**
                Revives an item (or all items) into a full Model instance. The _item_
                argument may be the index of an object in this list, an actual object (which
                must exist in the list), or may be omitted to revive all items in the list.
            
                Once revived, Model instances are attached to this list and cached so that
                reviving them in the future doesn't require another Model instantiation. Use
                the `free()` method to explicitly uncache and detach a previously revived
                Model instance.
            
                Note: Specifying an index rather than an object will be faster, since
                objects require an `indexOf()` lookup in order to retrieve the index.
            
                @method revive
                @param {Number|Object} [item] Index of the object to revive, or the object
                    itself. If an object, that object must exist in this list. If not
                    specified, all items in the list will be revived and an array of models
                    will be returned.
                @return {Model|Model[]|null} Revived Model instance, array of revived Model
                    instances, or `null` if the given index or object was not found in this
                    list.
                @see free()
                **/
                revive: function (item) {
                    var i, len, models;
            
                    if (item || item === 0) {
                        return this._revive(Lang.isNumber(item) ? item :
                            this.indexOf(item));
                    } else {
                        models = [];
            
                        for (i = 0, len = this._items.length; i < len; i++) {
                            models.push(this._revive(i));
                        }
            
                        return models;
                    }
                },
            
                /**
                Overrides ModelList#toJSON() to use toArray() instead, since it's more
                efficient for LazyModelList.
            
                @method toJSON
                @return {Object[]} Array of objects.
                @see ModelList.toJSON()
                **/
                toJSON: function () {
                    return this.toArray();
                },
            
                // -- Protected Methods ----------------------------------------------------
            
                /**
                Overrides ModelList#add() to work with plain objects.
            
                @method _add
                @param {Object|Model} item Object or model to add.
                @param {Object} [options] Options.
                @return {Object} Added item.
                @protected
                @see ModelList._add()
                **/
                _add: function (item, options) {
                    var facade;
            
                    options || (options = {});
            
                    // If the item is a model instance, convert it to a plain object.
                    item = this._modelToObject(item);
            
                    // Ensure that the item has a clientId.
                    if (!('clientId' in item)) {
                        item.clientId = this._generateClientId();
                    }
            
                    if (this._isInList(item)) {
                        this.fire(EVT_ERROR, {
                            error: 'Model is already in the list.',
                            model: item,
                            src  : 'add'
                        });
            
                        return;
                    }
            
                    facade = Y.merge(options, {
                        index: 'index' in options ? options.index : this._findIndex(item),
                        model: item
                    });
            
                    options.silent ? this._defAddFn(facade) : this.fire(EVT_ADD, facade);
            
                    return item;
                },
            
                /**
                Overrides ModelList#clear() to support `this._models`.
            
                @method _clear
                @protected
                @see ModelList.clear()
                **/
                _clear: function () {
                    YArray.each(this._models, this._detachList, this);
            
                    this._clientIdMap = {};
                    this._idMap       = {};
                    this._items       = [];
                    this._models      = [];
                },
            
                /**
                Generates an ad-hoc clientId for a non-instantiated Model.
            
                @method _generateClientId
                @return {String} Unique clientId.
                @protected
                **/
                _generateClientId: function () {
                    GlobalEnv.lastId || (GlobalEnv.lastId = 0);
                    return this.model.NAME + '_' + (GlobalEnv.lastId += 1);
                },
            
                /**
                Returns `true` if the given item is in this list, `false` otherwise.
            
                @method _isInList
                @param {Object} item Plain object item.
                @return {Boolean} `true` if the item is in this list, `false` otherwise.
                @protected
                **/
                _isInList: function (item) {
                    return !!(('clientId' in item && this._clientIdMap[item.clientId]) ||
                            ('id' in item && this._idMap[item.id]));
                },
            
                /**
                Converts a Model instance into a plain object. If _model_ is not a Model
                instance, it will be returned as is.
            
                This method differs from Model#toJSON() in that it doesn't delete the
                `clientId` property.
            
                @method _modelToObject
                @param {Model|Object} model Model instance to convert.
                @return {Object} Plain object.
                @protected
                **/
                _modelToObject: function (model) {
                    if (model._isYUIModel) {
                        model = model.getAttrs();
                        delete model.destroyed;
                        delete model.initialized;
                    }
            
                    return model;
                },
            
                /**
                Overrides ModelList#_remove() to convert Model instances to indices
                before removing to ensure consistency in the `remove` event facade.
            
                @method _remove
                @param {Object|Model} item Object or model to remove.
                @param {Object} [options] Options.
                @return {Object} Removed object.
                @protected
                **/
                _remove: function (item, options) {
                    // If the given item is a model instance, turn it into an index before
                    // calling the parent _remove method, since we only want to deal with
                    // the plain object version.
                    if (item._isYUIModel) {
                        item = this.indexOf(item);
                    }
            
                    return Y.ModelList.prototype._remove.call(this, item, options);
                },
            
                /**
                Revives a single model at the specified index and returns it. This is the
                underlying implementation for `revive()`.
            
                @method _revive
                @param {Number} index Index of the item to revive.
                @return {Model} Revived model.
                @protected
                **/
                _revive: function (index) {
                    var item, model;
            
                    if (index < 0) {
                        return null;
                    }
            
                    item = this._items[index];
            
                    if (!item) {
                        return null;
                    }
            
                    model = this._models[index];
            
                    if (!model) {
                        model = new this.model(item);
            
                        // The clientId attribute is read-only, but revived models should
                        // have the same clientId as the original object, so we need to set
                        // it manually.
                        model._set('clientId', item.clientId);
            
                        this._attachList(model);
                        this._models[index] = model;
                    }
            
                    return model;
                },
            
                // -- Event Handlers -------------------------------------------------------
            
                /**
                Handles `change` events on revived models and updates the original objects
                with the changes.
            
                @method _afterModelChange
                @param {EventFacade} e
                @protected
                **/
                _afterModelChange: function (e) {
                    var changed = e.changed,
                        item    = this._clientIdMap[e.target.get('clientId')],
                        name;
            
                    if (item) {
                        for (name in changed) {
                            if (changed.hasOwnProperty(name)) {
                                item[name] = changed[name].newVal;
                            }
                        }
                    }
                },
            
                // -- Default Event Handlers -----------------------------------------------
            
                /**
                Overrides ModelList#_defAddFn() to support plain objects.
            
                @method _defAddFn
                @param {EventFacade} e
                @protected
                **/
                _defAddFn: function (e) {
                    var item = e.model;
            
                    this._clientIdMap[item.clientId] = item;
            
                    if (Lang.isValue(item.id)) {
                        this._idMap[item.id] = item;
                    }
            
                    this._items.splice(e.index, 0, item);
                },
            
                /**
                Overrides ModelList#_defRemoveFn() to support plain objects.
            
                @method _defRemoveFn
                @param {EventFacade} e
                @protected
                **/
                _defRemoveFn: function (e) {
                    var index = e.index,
                        item  = e.model,
                        model = this._models[index];
            
                    delete this._clientIdMap[item.clientId];
            
                    if ('id' in item) {
                        delete this._idMap[item.id];
                    }
            
                    if (model) {
                        this._detachList(model);
                    }
            
                    this._items.splice(index, 1);
                    this._models.splice(index, 1);
                }
            });