Reader.ts

interface Reader {
  read(): Promise<Buffer>;
}

class FileReader implements Reader {
  private path: string;

  constructor(path: string) {
    this.path = path;
  }

  async read() {
    return fs.readFileSync(path);
  }
}

class URLReader implements Reader {
  private url: string;

  constructor(url: string) {
    this.url = url;
  }

  async read() {
    return new Promise((resolve, reject) => {
      http.get(this.url, res => {
        // stream data from response and resolve Promise
      });
    }
  }
}

Renamable.ts

interface Renamable {
  name: string
  modificationDate: Date;
}

function rename(r: Renamable, name: string) {
  r.name = name;
  r.modificationDate = new Date();
}

class File implements Renamable {
  name: string;
  creationDate: Date;
  modificationDate: Date;

  contents: Buffer;
}

class Bucket implements Renamable {
  name: string;
  creationDate: Date;
  modificationDate: Date;

  files: File[]
}