persagy-web/persagy-web-base/src/undo/SUndoStack.ts

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 *      .&888888I                                          Copyright (c) 2009-2020.  博锐尚格科技股份有限公司
 *        ~8888'
 *        .!88~                                                                     All rights reserved.
 *
 * *********************************************************************************************************************
 */

import { SObject } from "../SObject";
import { SUndoCommand } from "./SUndoCommand";
import { SCommandLog } from "./SCommandLog";

/**
 * Undo操作堆栈
 *
 * @author  庞利祥(sybotan@126.com)
 */
export class SUndoStack extends SObject {
    /** 命令栈 */
    private cmdStack = Array<SUndoCommand>();

    /** 当前命令索引 */
    private _index = -1;
    get index(): number {
        return this._index;
    } // Get index

    /** 命令栈是否为空 */
    get isEmpty(): boolean {
        return this.cmdStack.length <= 0;
    } // Get isEmpty

    /** 是否更改 */
    isChange: boolean = false;

    /**
     * 执行redo操作
     */
    redo(): void {
        if (!this.canRedo()) {
            return;
        }

        this._index++;
        this.cmdStack[this._index].redo();
        this.isChange = true;
    } // Function redo()

    /**
     * 执行undo操作
     */
    undo(): void {
        if (!this.canUndo()) {
            return;
        }

        this.cmdStack[this._index].undo();
        this._index--;
        this.isChange = true;
    } // Function undo()

    /**
     * 是否可以执行Redo操作
     *
     * @return  可以执行，返回true；否则返回false。
     */
    canRedo(): boolean {
        return this.index + 1 < this.cmdStack.length;
    } // Function canRedo()

    /**
     * 是否可以执行Undo操作
     *
     * @return  可以执行，返回true；否则返回false。
     */
    canUndo(): boolean {
        return this.index >= 0;
    } // Function canUndo()

    /**
     * 清空堆栈
     */
    clear(): void {
        this.cmdStack.length = 0;
        this._index = -1;
        this.isChange = true;
    } // Function clear()

    /**
     * 返回指定索引的命令
     *
     * @param   index       命令在栈中的索引
     */
    command(index: number): SUndoCommand | null {
        // 如果索引越界，则返回null
        if (index < 0 || index >= this.cmdStack.length) {
            return null;
        }

        return this.cmdStack[index];
    } // Function command()

    /**
     * 统计命令栈中命令的数量
     */
    count(): number {
        return this.cmdStack.length;
    } // Function count()

    /**
     * 将命令添加到命令栈
     *
     * @param   cmd     被添加的命令
     */
    push(cmd: SUndoCommand): void {
        this.cmdStack.length = this._index + 1;
        if (this._index >= 0 && cmd.mergeWith(this.cmdStack[this._index])) {
            return;
        }

        this.cmdStack.push(cmd);
        this._index = this.cmdStack.length - 1;
        this.isChange = true;
    } // Function push()

    /**
     * 将命令堆栈转为日志(命令数组)
     *
     * */
    toLog(): SCommandLog[] {
        let stackList: SCommandLog[] = [];
        for (let i = 0; i <= this.index; i++) {
            stackList.push({
                command: this.cmdStack[i].command,
                desc: this.cmdStack[i].desc,
                detail: this.cmdStack[i].toString()
            });
        }
        return stackList;
    } // Function toLog()
} // Class SUndoStack