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undo-redo.ts
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undo-redo.ts
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/*
* Tencent is pleased to support the open source community by making TMagicEditor available.
*
* Copyright (C) 2021 THL A29 Limited, a Tencent company. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import { cloneDeep } from 'lodash-es';
export class UndoRedo<T = any> {
private elementList: T[];
private listCursor: number;
private listMaxSize: number;
constructor(listMaxSize = 200) {
const minListMaxSize = 2;
this.elementList = [];
this.listCursor = 0;
this.listMaxSize = listMaxSize > minListMaxSize ? listMaxSize : minListMaxSize;
}
public pushElement(element: T): void {
// 新元素进来时,把游标之外的元素全部丢弃,并把新元素放进来
this.elementList.splice(this.listCursor, this.elementList.length - this.listCursor, cloneDeep(element));
this.listCursor += 1;
// 如果list中的元素超过maxSize,则移除第一个元素
if (this.elementList.length > this.listMaxSize) {
this.elementList.shift();
this.listCursor -= 1;
}
}
public canUndo(): boolean {
return this.listCursor > 1;
}
// 返回undo后的当前元素
public undo(): T | null {
if (!this.canUndo()) {
return null;
}
this.listCursor -= 1;
return this.getCurrentElement();
}
public canRedo() {
return this.elementList.length > this.listCursor;
}
// 返回redo后的当前元素
public redo(): T | null {
if (!this.canRedo()) {
return null;
}
this.listCursor += 1;
return this.getCurrentElement();
}
public getCurrentElement(): T | null {
if (this.listCursor < 1) {
return null;
}
return cloneDeep(this.elementList[this.listCursor - 1]);
}
}