/**
 * @class Ext.view.BoundListKeyNav
 * @extends Ext.util.KeyNav
 * A specialized {@link Ext.util.KeyNav} implementation for navigating a {@link Ext.view.BoundList} using
 * the keyboard. The up, down, pageup, pagedown, home, and end keys move the active highlight
 * through the list. The enter key (and optionally the tab key) invokes the selection model's
 * select action using the highlighted item.
 */
Ext.define('Ext.view.BoundListKeyNav', {
    extend: 'Ext.util.KeyNav',
    requires: 'Ext.view.BoundList',

    
/**
     * @cfg {Ext.view.BoundList} boundList
     * @required
     * The {@link Ext.view.BoundList} instance for which key navigation will be managed. This is required.
     */

    
/**
     * @cfg {Boolean} selectOnTab
     * Whether the Tab key should select the currently highlighted item. Defaults to true.
     */
    selectOnTab: true,

    constructor: function(el, config) {
        var me = this;
        Ext.copyTo(me, config, 'boundList,selectOnTab');
        config = Ext.apply({}, config, me.defaultHandlers);
        me.callParent([el, config]);
    },

    defaultHandlers: {
        up: function() {
            var me = this,
                boundList = me.boundList,
                allItems = boundList.all,
                oldItem = boundList.highlightedItem,
                oldItemIdx = oldItem ? boundList.indexOf(oldItem) : -1,
                newItemIdx = oldItemIdx > 0 ? oldItemIdx - 1 : allItems.getCount() - 1; //wraps around
            me.highlightAt(newItemIdx);
        },

        down: function() {
            var me = this,
                boundList = me.boundList,
                allItems = boundList.all,
                oldItem = boundList.highlightedItem,
                oldItemIdx = oldItem ? boundList.indexOf(oldItem) : -1,
                newItemIdx = oldItemIdx < allItems.getCount() - 1 ? oldItemIdx + 1 : 0; //wraps around
            me.highlightAt(newItemIdx);
        },

        pageup: function() {
            //TODO
        },

        pagedown: function() {
            //TODO
        },

        home: function() {
            this.highlightAt(0);
        },

        end: function() {
            var me = this;
            me.highlightAt(me.boundList.all.getCount() - 1);
        },

        enter: function(e) {
            this.selectHighlighted(e);
        },

        tab: function(e) {
            var me = this;
            if (me.selectOnTab) {
                me.selectHighlighted(e);
            }
            // Tab key event is allowed to propagate to field
            return true;
        }
    },

    
/**
     * Highlights the item at the given index.
     * @param {Number} index
     */
    highlightAt: function(index) {
        var boundList = this.boundList,
            item = boundList.all.item(index);
        if (item) {
            item = item.dom;
            boundList.highlightItem(item);
            boundList.el.scrollChildIntoView(item, false);
        }
    },

    
/**
     * Triggers selection of the currently highlighted item according to the behavior of
     * the configured SelectionModel.
     */
    selectHighlighted: function(e) {
        var me = this,
            boundList = me.boundList,
            highlighted = boundList.highlightedItem,
            selModel = boundList.getSelectionModel();
        if (highlighted) {
            selModel.selectWithEvent(boundList.getRecord(highlighted), e);
        }
    }

});