import { IEntity } from '@ibizstudio/api';
import { last, drop, clone } from 'ramda';

/**
 * 数据历史状态管理
 *
 * @export
 * @class DataHistory
 */
export class DataHistory {
    /**
     * 历史数据列表
     *
     * @type {IEntity[]}
     * @memberof DataHistory
     */
    readonly historyList: IEntity[] = [];
    /**
     * 待前进数据
     *
     * @type {IEntity[]}
     * @memberof DataHistory
     */
    readonly forwardList: IEntity[] = [];

    /**
     * 新增历史数据
     *
     * @param {*} item
     * @return {*}  {*}
     * @memberof DataHistory
     */
    add(item: IEntity): IEntity {
        // 当待前进回滚数据存在时清空
        const num = this.forwardList.length;
        if (num > 0) {
            drop(num, this.forwardList);
        }
        // 加入历史记录并在历史记录达到最大值时清除最老的数据
        this.historyList.push(clone(item));
        if (this.historyList.length > 20) {
            drop(1, this.historyList);
        }
        return item;
    }

    /**
     * 数据回退
     *
     * @return {*}  {*}
     * @memberof DataHistory
     */
    backOff(): IEntity | null {
        if (this.historyList.length > 0) {
            const item = clone(last(this.historyList))!;
            this.forwardList.push(item);
            return item;
        }
        return null;
    }

    /**
     * 数据回退前进
     *
     * @return {*}  {*}
     * @memberof DataHistory
     */
    forward(): IEntity | null {
        if (this.forwardList.length > 0) {
            const item = clone(last(this.forwardList))!;
            this.historyList.push(item);
            return item;
        }
        return null;
    }
}