class Reader<T extends Formatter> {
  datasource: Array<any>

  constructor(datasource: Array<any>) {
    this.datasource = datasource
  }

  read(id: number) {
    const data = this.datasource[id]
    if (!data) {
      throw new Error(`${id} was not found.`)
    }

    return this.format(data)
  }

  format(data: any): T {
    return new Formatter(data) as T;
  }
}

class WidgetReader extends Reader<WidgetFormatter> {
  format(data: any): WidgetFormatter {
    return new WidgetFormatter(data)
  }
}