src/app/custom_modules/undo-redo-stack/undo-redo-stack.component.ts

/*
******************************************************************************
* Copyright © 2018 PTA GmbH.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
*
*     http://www.eclipse.org/legal/epl-v10.html
*
******************************************************************************
*/
import { Component } from '@angular/core';
import { Command } from './commands/command';

export class UndoRedoStackComponent {
  private stack: Command[] = [];
  private pointer = -1;
  private limit = -1;

  constructor(isMergeable: boolean = true) {
    this.clear();
  }

  public push(cmd: Command) {
    if (this.pointer >= 0 && this.stack[this.pointer].mergePossible(cmd)) {
      this.stack[this.pointer].merge(cmd);
    } else {
      this.pointer++;
      this.limit = this.pointer;
      this.stack[this.pointer] = cmd;
    }
  }

  public undo() {
    if (this.isUndoPossible()) {
      this.stack[this.pointer].undo();
      this.pointer--;
    }
  }

  public redo() {
    if (this.isRedoPossible()) {
      this.pointer++;
      this.stack[this.pointer].redo();
    }
  }

  public isUndoPossible() {
    return this.pointer >= 0;
  }

  public isRedoPossible() {
    return this.pointer < this.limit;
  }

  public clear() {
    this.stack = [];
    this.pointer = -1;
    this.limit = -1;
  }

}