enum State = {
  Created,
  Loading,
  Stopped,
  Playing,
  Discarded,
};

class MediaPlayer {
  private state = State.Created;

  play(): boolean {
    // Validation
    if (this.state !== State.Stopped) {
      console.warn('play() called in invalid state');
      return false;
    }

    // Execution
    this.startPlayback();

    // Transition
    this.state = State.Playing;

    // Result
    return true;
  }
}