    /**
     * @class Ext.grid.feature.Grouping
     * @extends Ext.grid.feature.Feature
     *
     * This feature allows to display the grid rows aggregated into groups as specified by the {@link Ext.data.Store#groupers}
     * specified on the Store. The group will show the title for the group name and then the appropriate records for the group
     * underneath. The groups can also be expanded and collapsed.
     *
     * ## Extra Events
     * This feature adds several extra events that will be fired on the grid to interact with the groups:
     *
     *  - {@link #groupclick}
     *  - {@link #groupdblclick}
     *  - {@link #groupcontextmenu}
     *  - {@link #groupexpand}
     *  - {@link #groupcollapse}
     *
     * ## Menu Augmentation
     * This feature adds extra options to the grid column menu to provide the user with functionality to modify the grouping.
     * This can be disabled by setting the {@link #enableGroupingMenu} option. The option to disallow grouping from being turned off
     * by thew user is {@link #enableNoGroups}.
     *
     * ## Controlling Group Text
     * The {@link #groupHeaderTpl} is used to control the rendered title for each group. It can modified to customized
     * the default display.
     *
     * ## Example Usage
     *
     *     var groupingFeature = Ext.create('Ext.grid.feature.Grouping', {
     *         groupHeaderTpl: 'Group: {name} ({rows.length})', //print the number of items in the group
     *         startCollapsed: true // start all groups collapsed
     *     });
     *
     * @ftype grouping
     * @author Nicolas Ferrero
     */
    Ext.define('Ext.grid.feature.Grouping', {
        extend: 'Ext.grid.feature.Feature',
        alias: 'feature.grouping',

        eventPrefix: 'group',
        eventSelector: '.' + Ext.baseCSSPrefix + 'grid-group-hd',

        constructor: function() {
            this.collapsedState = {};
            this.callParent(arguments);
        },

        /**
         * @event groupclick
         * @param {Ext.view.Table} view
         * @param {HTMLElement} node
         * @param {Number} unused
         * @param {Number} unused
         * @param {Ext.EventObject} e
         */

        /**
         * @event groupdblclick
         * @param {Ext.view.Table} view
         * @param {HTMLElement} node
         * @param {Number} unused
         * @param {Number} unused
         * @param {Ext.EventObject} e
         */

        /**
         * @event groupcontextmenu
         * @param {Ext.view.Table} view
         * @param {HTMLElement} node
         * @param {Number} unused
         * @param {Number} unused
         * @param {Ext.EventObject} e
         */

        /**
         * @event groupcollapse
         * @param {Ext.view.Table} view
         * @param {HTMLElement} node
         * @param {Number} unused
         * @param {Number} unused
         * @param {Ext.EventObject} e
         */

        /**
         * @event groupexpand
         * @param {Ext.view.Table} view
         * @param {HTMLElement} node
         * @param {Number} unused
         * @param {Number} unused
         * @param {Ext.EventObject} e
         */

        /**
         * @cfg {String} groupHeaderTpl
         * Template snippet, this cannot be an actual template. {name} will be replaced with the current group.
         * Defaults to 'Group: {name}'
         */
        groupHeaderTpl: 'Group: {name}',

        /**
         * @cfg {Number} depthToIndent
         * Number of pixels to indent per grouping level
         */
        depthToIndent: 17,

        collapsedCls: Ext.baseCSSPrefix + 'grid-group-collapsed',
        hdCollapsedCls: Ext.baseCSSPrefix + 'grid-group-hd-collapsed',

        /**
         * @cfg {String} groupByText Text displayed in the grid header menu for grouping by header
         * (defaults to 'Group By This Field').
         */
        groupByText : 'Group By This Field',
        /**
         * @cfg {String} showGroupsText Text displayed in the grid header for enabling/disabling grouping
         * (defaults to 'Show in Groups').
         */
        showGroupsText : 'Show in Groups',

        /**
         * @cfg {Boolean} hideGroupedHeader<tt>true</tt> to hide the header that is currently grouped (defaults to <tt>false</tt>)
         */
        hideGroupedHeader : false,

        /**
         * @cfg {Boolean} startCollapsed <tt>true</tt> to start all groups collapsed (defaults to <tt>false</tt>)
         */
        startCollapsed : false,

        /**
         * @cfg {Boolean} enableGroupingMenu <tt>true</tt> to enable the grouping control in the header menu (defaults to <tt>true</tt>)
         */
        enableGroupingMenu : true,

        /**
         * @cfg {Boolean} enableNoGroups <tt>true</tt> to allow the user to turn off grouping (defaults to <tt>true</tt>)
         */
        enableNoGroups : true,

        enable: function() {
            var me    = this,
                view  = me.view,
                store = view.store,
                groupToggleMenuItem;

            if (me.lastGroupIndex) {
                store.group(me.lastGroupIndex);
            }
            me.callParent();
            groupToggleMenuItem = me.view.headerCt.getMenu().down('#groupToggleMenuItem');
            groupToggleMenuItem.setChecked(true, true);
            view.refresh();
        },

        disable: function() {
            var me    = this,
                view  = me.view,
                store = view.store,
                groupToggleMenuItem,
                lastGroup;

            lastGroup = store.groupers.first();
            if (lastGroup) {
                me.lastGroupIndex = lastGroup.property;
                store.groupers.clear();
            }

            me.callParent();
            groupToggleMenuItem = me.view.headerCt.getMenu().down('#groupToggleMenuItem');
            groupToggleMenuItem.setChecked(true, true);
            groupToggleMenuItem.setChecked(false, true);
            view.refresh();
        },

        getFeatureTpl: function(values, parent, x, xcount) {
            var me = this;

            return [
                '<tpl if="typeof rows !== \'undefined\'">',
                    // group row tpl
                    '<tr class="' + Ext.baseCSSPrefix + 'grid-group-hd ' + (me.startCollapsed ? me.hdCollapsedCls : '') + ' {hdCollapsedCls}"><td class="' + Ext.baseCSSPrefix + 'grid-cell" colspan="' + parent.columns.length + '" {[this.indentByDepth(values)]}><div class="' + Ext.baseCSSPrefix + 'grid-cell-inner"><div class="' + Ext.baseCSSPrefix + 'grid-group-title">{collapsed}' + me.groupHeaderTpl + '</div></div></td></tr>',
                    // this is the rowbody
                    '<tr id="{viewId}-gp-{name}" class="' + Ext.baseCSSPrefix + 'grid-group-body ' + (me.startCollapsed ? me.collapsedCls : '') + ' {collapsedCls}"><td colspan="' + parent.columns.length + '">{[this.recurse(values)]}</td></tr>',
                '</tpl>'
            ].join('');
        },

        getFragmentTpl: function() {
            return {
                indentByDepth: this.indentByDepth,
                depthToIndent: this.depthToIndent
            };
        },

        indentByDepth: function(values) {
            var depth = values.depth || 0;
            return 'style="padding-left:'+ depth * this.depthToIndent + 'px;"';
        },

        // Containers holding these components are responsible for
        // destroying them, we are just deleting references.
        destroy: function() {
            var me = this;

            delete me.view;
            delete me.prunedHeader;
        },

        // perhaps rename to afterViewRender
        attachEvents: function() {
            var me = this,
                view = me.view,
                header, headerId, menu, menuItem;

            view.on({
                scope: me,
                groupclick: me.onGroupClick,
                rowfocus: me.onRowFocus
            });
            view.store.on('groupchange', me.onGroupChange, me);

            me.pruneGroupedHeader();

            if (me.enableGroupingMenu) {
                me.injectGroupingMenu();
            }

            if (me.hideGroupedHeader) {
                header = view.headerCt.down('gridcolumn[dataIndex=' + me.getGroupField() + ']');
                headerId = header.id;
                menu = view.headerCt.getMenu();
                menuItem = menu.down('menuitem[headerId='+ headerId +']');
                if (menuItem) {
                    menuItem.setChecked(false);
                }
            }
        },

        injectGroupingMenu: function() {
            var me       = this,
                view     = me.view,
                headerCt = view.headerCt;
            headerCt.showMenuBy = me.showMenuBy;
            headerCt.getMenuItems = me.getMenuItems();
        },

        showMenuBy: function(t, header) {
            var menu = this.getMenu(),
                groupMenuItem  = menu.down('#groupMenuItem'),
                groupableMth = header.groupable === false ?  'disable' : 'enable';

            groupMenuItem[groupableMth]();
            Ext.grid.header.Container.prototype.showMenuBy.apply(this, arguments);
        },

        getMenuItems: function() {
            var me                 = this,
                groupByText        = me.groupByText,
                disabled           = me.disabled,
                showGroupsText     = me.showGroupsText,
                enableNoGroups     = me.enableNoGroups,
                groupMenuItemClick = Ext.Function.bind(me.onGroupMenuItemClick, me),
                groupToggleMenuItemClick = Ext.Function.bind(me.onGroupToggleMenuItemClick, me)

            // runs in the scope of headerCt
            return function() {
                var o = Ext.grid.header.Container.prototype.getMenuItems.call(this);
                o.push('-', {
                    itemId: 'groupMenuItem',
                    text: groupByText,
                    handler: groupMenuItemClick
                });
                if (enableNoGroups) {
                    o.push({
                        itemId: 'groupToggleMenuItem',
                        text: showGroupsText,
                        checked: !disabled,
                        checkHandler: groupToggleMenuItemClick
                    });
                }
                return o;
            };
        },

        /**
         * Group by the header the user has clicked on.
         * @private
         */
        onGroupMenuItemClick: function(menuItem, e) {
            var menu = menuItem.parentMenu,
                hdr  = menu.activeHeader,
                view = this.view;

            delete this.lastGroupIndex;
            this.enable();
            view.store.group(hdr.dataIndex);
            this.pruneGroupedHeader();

        },

        /**
         * Turn on and off grouping via the menu
         * @private
         */
        onGroupToggleMenuItemClick: function(menuItem, checked) {
            this[checked ? 'enable' : 'disable']();
        },

        /**
         * Prunes the grouped header from the header container
         * @private
         */
        pruneGroupedHeader: function() {
            var me         = this,
                view       = me.view,
                store      = view.store,
                groupField = me.getGroupField(),
                headerCt   = view.headerCt,
                header     = headerCt.down('header[dataIndex=' + groupField + ']');

            if (header) {
                if (me.prunedHeader) {
                    me.prunedHeader.show();
                }
                me.prunedHeader = header;
                header.hide();
            }
        },

        getGroupField: function(){
            var group = this.view.store.groupers.first();
            if (group) {
                return group.property;
            }
            return '';
        },

        /**
         * When a row gains focus, expand the groups above it
         * @private
         */
        onRowFocus: function(rowIdx) {
            var node    = this.view.getNode(rowIdx),
                groupBd = Ext.fly(node).up('.' + this.collapsedCls);

            if (groupBd) {
                // for multiple level groups, should expand every groupBd
                // above
                this.expand(groupBd);
            }
        },

        /**
         * Expand a group by the groupBody
         * @param {Ext.core.Element} groupBd
         * @private
         */
        expand: function(groupBd) {
            var me = this,
                view = me.view,
                grid = view.up('gridpanel'),
                groupBdDom = Ext.getDom(groupBd);

            me.collapsedState[groupBdDom.id] = false;

            groupBd.removeCls(me.collapsedCls);
            groupBd.prev().removeCls(me.hdCollapsedCls);

            grid.determineScrollbars();
            grid.invalidateScroller();
            view.fireEvent('groupexpand');
        },

        /**
         * Collapse a group by the groupBody
         * @param {Ext.core.Element} groupBd
         * @private
         */
        collapse: function(groupBd) {
            var me = this,
                view = me.view,
                grid = view.up('gridpanel'),
                groupBdDom = Ext.getDom(groupBd);

            me.collapsedState[groupBdDom.id] = true;

            groupBd.addCls(me.collapsedCls);
            groupBd.prev().addCls(me.hdCollapsedCls);

            grid.determineScrollbars();
            grid.invalidateScroller();
            view.fireEvent('groupcollapse');
        },

        onGroupChange: function(){
            this.view.refresh();
        },

        /**
         * Toggle between expanded/collapsed state when clicking on
         * the group.
         * @private
         */
        onGroupClick: function(view, group, idx, foo, e) {
            var me = this,
                toggleCls = me.toggleCls,
                groupBd = Ext.fly(group.nextSibling, '_grouping');

            if (groupBd.hasCls(me.collapsedCls)) {
                me.expand(groupBd);
            } else {
                me.collapse(groupBd);
            }
        },

        // Injects isRow and closeRow into the metaRowTpl.
        getMetaRowTplFragments: function() {
            return {
                isRow: this.isRow,
                closeRow: this.closeRow
            };
        },

        // injected into rowtpl and wrapped around metaRowTpl
        // becomes part of the standard tpl
        isRow: function() {
            return '<tpl if="typeof rows === \'undefined\'">';
        },

        // injected into rowtpl and wrapped around metaRowTpl
        // becomes part of the standard tpl
        closeRow: function() {
            return '</tpl>';
        },

        // isRow and closeRow are injected via getMetaRowTplFragments
        mutateMetaRowTpl: function(metaRowTpl) {
            metaRowTpl.unshift('{[this.isRow()]}');
            metaRowTpl.push('{[this.closeRow()]}');
        },

        // injects an additional style attribute via tdAttrKey with the proper
        // amount of padding
        getAdditionalData: function(data, idx, record, orig) {
            var view = this.view,
                hCt  = view.headerCt,
                col  = hCt.items.getAt(0),
                o = {},
                tdAttrKey = col.id + '-tdAttr';

            // maintain the current tdAttr that a user may ahve set.
            o[tdAttrKey] = this.indentByDepth(data) + " " + (orig[tdAttrKey] ? orig[tdAttrKey] : '');
            o.collapsed = 'true';
            return o;
        },

        // return matching preppedRecords
        getGroupRows: function(group, records, preppedRecords, fullWidth) {
            var me = this,
                children = group.children,
                rows = group.rows = [],
                view = me.view;
            group.viewId = view.id;

            Ext.Array.each(records, function(record, idx) {
                if (Ext.Array.indexOf(children, record) != -1) {
                    rows.push(Ext.apply(preppedRecords[idx], {
                        depth: 1
                    }));
                }
            });
            delete group.children;
            group.fullWidth = fullWidth;
            if (me.collapsedState[view.id + '-gp-' + group.name]) {
                group.collapsedCls = me.collapsedCls;
                group.hdCollapsedCls = me.hdCollapsedCls;
            }

            return group;
        },

        // return the data in a grouped format.
        collectData: function(records, preppedRecords, startIndex, fullWidth, o) {
            var me    = this,
                store = me.view.store,
                groups;

            if (!me.disabled && store.isGrouped()) {
                groups = store.getGroups();
                Ext.Array.each(groups, function(group, idx){
                    me.getGroupRows(group, records, preppedRecords, fullWidth);
                }, me);
                return {
                    rows: groups,
                    fullWidth: fullWidth
                };
            }
            return o;
        },

        // adds the groupName to the groupclick, groupdblclick, groupcontextmenu
        // events that are fired on the view. Chose not to return the actual
        // group itself because of its expense and because developers can simply
        // grab the group via store.getGroups(groupName)
        getFireEventArgs: function(type, view, featureTarget) {
            var returnArray = [type, view, featureTarget],
                groupBd     = Ext.fly(featureTarget.nextSibling, '_grouping'),
                groupBdId   = Ext.getDom(groupBd).id,
                prefix      = view.id + '-gp-',
                groupName   = groupBdId.substr(prefix.length);

            returnArray.push(groupName);

            return returnArray;
        }
    });