/********************************************************************************
 * Copyright (C) 2017 TypeFox and others.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the Eclipse
 * Public License v. 2.0 are satisfied: GNU General Public License, version 2
 * with the GNU Classpath Exception which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 ********************************************************************************/ import { injectable } from 'inversify' ; import { TreeNode } from './tree' ; @ injectable ( ) export class TreeNavigationService { protected index : number = - 1 ; protected nodes : TreeNode [ ] = [ ] ; get next ( ) : TreeNode | undefined { return this . nodes [ this . index + 1 ] ; } get prev ( ) : TreeNode | undefined { return this . nodes [ this . index - 1 ] ; } advance ( ) { const node = this . next ; if ( node ) { this . index = this . index + 1 ; return node ; } return undefined ; } retreat ( ) { const node = this . prev ; if ( node ) { this . index = this . index - 1 ; return node ; } return undefined ; } push ( node ) { this . nodes = this . nodes . slice ( 0 , this . index + 1 ) ; this . nodes . push ( node ) ; this . index = this . index + 1 ; } }