    /**
     * @docauthor Tommy Maintz <tommy@sencha.com>
     *
     * A mixin which allows a data component to be sorted. This is used by e.g. {@link Ext.data.Store} and {@link Ext.data.TreeStore}.
     *
     * **NOTE**: This mixin is mainly for internal use and most users should not need to use it directly. It
     * is more likely you will want to use one of the component classes that import this mixin, such as
     * {@link Ext.data.Store} or {@link Ext.data.TreeStore}.
     */
    Ext.define("Ext.util.Sortable", {
        /**
         * @property {Boolean} isSortable
         * `true` in this class to identify an object as an instantiated Sortable, or subclass thereof.
         */
        isSortable: true,

        /**
         * @cfg {String} defaultSortDirection
         * The default sort direction to use if one is not specified.
         */
        defaultSortDirection: "ASC",

        requires: [
            'Ext.util.Sorter'
        ],

        statics: {
            /**
             * Creates a single comparator function which encapsulates the passed Sorter array.
             * @param {Ext.util.Sorter[]} sorters The sorter set for which to create a comparator function
             * @return {Function} a function, which when passed two comparable objects returns the result
             * of the whole sorter comparator functions.
             */
            createComparator: function(sorters) {
                return sorters && sorters.length ? function(r1, r2) {
                    var result = sorters[0].sort(r1, r2),
                        length = sorters.length,
                        i = 1;

                    // if we have more than one sorter, OR any additional sorter functions together
                    for (; i < length; i++) {
                        result = result || sorters[i].sort.call(this, r1, r2);
                    }
                    return result;
                }: function() {
                    return 0;
                };
            }
        },

        /**
         * @cfg {String} sortRoot
         * The property in each item that contains the data to sort.
         */

        /**
         * @cfg {Ext.util.Sorter[]/Object[]} sorters
         * The initial set of {@link Ext.util.Sorter Sorters}
         */

        /**
         * Performs initialization of this mixin. Component classes using this mixin should call this method during their
         * own initialization.
         */
        initSortable: function() {
            var me = this,
                sorters = me.sorters;

            /**
             * @property {Ext.util.MixedCollection} sorters
             * The collection of {@link Ext.util.Sorter Sorters} currently applied to this Store
             */
            me.sorters = new Ext.util.AbstractMixedCollection(false, function(item) {
                return item.id || item.property;
            });

            if (sorters) {
                me.sorters.addAll(me.decodeSorters(sorters));
            }
        },

        /**
         * Sorts the data in the Store by one or more of its properties. Example usage:
         *
         *     //sort by a single field
         *     myStore.sort('myField', 'DESC');
         *
         *     //sorting by multiple fields
         *     myStore.sort([
         *         {
         *             property : 'age',
         *             direction: 'ASC'
         *         },
         *         {
         *             property : 'name',
         *             direction: 'DESC'
         *         }
         *     ]);
         *
         * Internally, Store converts the passed arguments into an array of {@link Ext.util.Sorter} instances, and delegates
         * the actual sorting to its internal {@link Ext.util.MixedCollection}.
         *
         * When passing a single string argument to sort, Store maintains a ASC/DESC toggler per field, so this code:
         *
         *     store.sort('myField');
         *     store.sort('myField');
         *
         * Is equivalent to this code, because Store handles the toggling automatically:
         *
         *     store.sort('myField', 'ASC');
         *     store.sort('myField', 'DESC');
         *
         * @param {String/Ext.util.Sorter[]} [sorters] Either a string name of one of the fields in this Store's configured
         * {@link Ext.data.Model Model}, or an array of sorter configurations.
         * @param {String} [direction="ASC"] The overall direction to sort the data by.
         * @return {Ext.util.Sorter[]}
         */
        sort: function(sorters, direction, where, doSort) {
            var me = this,
                sorter,
                newSorters;

            if (Ext.isArray(sorters)) {
                doSort = where;
                where = direction;
                newSorters = sorters;
            }
            else if (Ext.isObject(sorters)) {
                doSort = where;
                where = direction;
                newSorters = [sorters];
            }
            else if (Ext.isString(sorters)) {
                sorter = me.sorters.get(sorters);

                if (!sorter) {
                    sorter = {
                        property : sorters,
                        direction: direction
                    };
                    newSorters = [sorter];
                }
                else if (direction === undefined) {
                    sorter.toggle();
                }
                else {
                    sorter.setDirection(direction);
                }
            }

            if (newSorters && newSorters.length) {
                newSorters = me.decodeSorters(newSorters);
                if (Ext.isString(where)) {
                    if (where === 'prepend') {
                        me.sorters.insert(0, newSorters);
                    }
                    else {
                        me.sorters.addAll(newSorters);
                    }
                }
                else {
                    me.sorters.clear();
                    me.sorters.addAll(newSorters);
                }
            }

            if (doSort !== false) {
                me.fireEvent('beforesort', me, newSorters);
                me.onBeforeSort(newSorters);

                sorters = me.sorters.items;
                if (sorters.length) {
                    // Sort using a generated sorter function which combines all of the Sorters passed
                    me.doSort(me.generateComparator());
                }
            }

            return sorters;
        },

        /**
         * Returns a comparator function which compares two items and returns -1, 0, or 1 depending
         * on the currently defined set of {@link #cfg-sorters}.
         *
         * If there are no {@link #cfg-sorters} defined, it returns a function which returns `0` meaning
         * that no sorting will occur.
         */
        generateComparator: function() {
            var sorters = this.sorters.getRange();
            return sorters.length ? this.createComparator(sorters) : this.emptyComparator;
        },

        emptyComparator: function(){
            return 0;
        },

        onBeforeSort: Ext.emptyFn,

        /**
         * @private
         * Normalizes an array of sorter objects, ensuring that they are all Ext.util.Sorter instances
         * @param {Object[]} sorters The sorters array
         * @return {Ext.util.Sorter[]} Array of Ext.util.Sorter objects
         */
        decodeSorters: function(sorters) {
            if (!Ext.isArray(sorters)) {
                if (sorters === undefined) {
                    sorters = [];
                } else {
                    sorters = [sorters];
                }
            }

            var length = sorters.length,
                Sorter = Ext.util.Sorter,
                fields = this.model ? this.model.prototype.fields : null,
                field,
                config, i;

            for (i = 0; i < length; i++) {
                config = sorters[i];

                if (!(config instanceof Sorter)) {
                    if (Ext.isString(config)) {
                        config = {
                            property: config
                        };
                    }

                    Ext.applyIf(config, {
                        root     : this.sortRoot,
                        direction: "ASC"
                    });

                    //support for 3.x style sorters where a function can be defined as 'fn'
                    if (config.fn) {
                        config.sorterFn = config.fn;
                    }

                    //support a function to be passed as a sorter definition
                    if (typeof config == 'function') {
                        config = {
                            sorterFn: config
                        };
                    }

                    // ensure sortType gets pushed on if necessary
                    if (fields && !config.transform) {
                        field = fields.get(config.property);
                        config.transform = field && field.sortType !== Ext.identityFn ? field.sortType : undefined;
                    }
                    sorters[i] = new Ext.util.Sorter(config);
                }
            }

            return sorters;
        },

        getSorters: function() {
            return this.sorters.items;
        },

        /**
         * Gets the first sorter from the sorters collection, excluding
         * any groupers that may be in place
         * @protected
         * @return {Ext.util.Sorter} The sorter, null if none exist
         */
        getFirstSorter: function(){
            var sorters = this.sorters.items,
                len = sorters.length,
                i = 0,
                sorter;

            for (; i < len; ++i) {
                sorter = sorters[i];
                if (!sorter.isGrouper) {
                    return sorter;
                }
            }
            return null;
        }
    }, function() {
        // Reference the static implementation in prototype
        this.prototype.createComparator = this.createComparator;
    });