Method tx

src/app/cache.ts:135–173

(
    key: string,
    callback: CB
  )

  // 事务处理,如果有事务正在进行,则等待
  public tx<T, CB extends (val: T | undefined, tx: { set: (newVal: T) => void; del: () => void }) => any>(
    key: string,
    callback: CB
  ): Promise<Awaited<ReturnType<CB>>> {
    const enum Actions {
      NONE = 0,
      SET = 1,
      DEL = 2,
    }
    return stackAsyncTask(key, () => {
      let ret: Awaited<ReturnType<CB>>;
      const act = { action: Actions.NONE } as { action?: number; newVal?: T };
      const set = (newVal: T) => {
        act.action = Actions.SET;
        act.newVal = newVal;
      };
      const del = () => {
        act.action = Actions.DEL;
        act.newVal = undefined;
      };
      return this.get<T>(key)
        .then((result) => {
          const tx = {
            set,
            del,
          };
          return callback(result, tx);
        })
        .then((result) => {
          ret = result;
          if (act.action === Actions.SET) {
            return this.set(key, act.newVal);
          } else if (act.action === Actions.DEL) {
            return this.del(key);
          }
        })
        .then(() => ret);
    });
  }

  incr(key: string, increase: number): Promise<number> {
    return this.tx(key, (value: number | undefined, tx) => {