interface Value<T> {
  data: T;
  timestamp: number;
}
interface Options {
  /** 过期时间，单位毫秒 */
  expires?: number;
  /** 是否保存在本地 */
  isSaveLoacl?: boolean;
}

abstract class Storage {
  protected data = new Map<string, any>();
  protected abstract _setItem(key: string, value: string): void;
  protected abstract _getItem(key: string): string | null;

  /** 设置缓存 */
  public setItem(key: string, data: string | null, options?: Options) {
    if (data === null) {
      this.data.delete(key);
      this._setItem(key, "");
    }
    const expires = options?.expires || 0;
    const value: Value<unknown> = {
      data: data,
      timestamp: expires === 0 ? 0 : Date.now() + expires
    };
    const valueStr = JSON.stringify(value);
    this.data.set(key, valueStr);
    if (expires > 0) {
      this._setItem(key, valueStr);
    }
  }

  /** 读取缓存 */
  public getItem<T>(key: string): T | null {
    const dist = this.data.get(key) || this._getItem(key);
    if (dist) {
      const storage = JSON.parse(dist) as Value<T>;
      // 如果未设置时间，则是走内存
      if (storage.timestamp === 0) {
        return storage.data;
      }
      // 缓存过期
      if (storage.timestamp - Date.now() <= 0) {
        this.setItem(key, null);
        return null;
      }
      return storage.data;
    }
    return null;
  }
}

export default Storage;