class ChatService {
  private messagesList = [
    {
      user: 'Jeanne',
      messages : ['Salut', 'moi c\'est Jeanne', 'toi c\'est comment ?']
    },
    {
      user: 'Serge',
      messages: ['Salut Jeanne', 'Moi c\'est Serge', 'Je fais du volleyball']
    }
  ];

  public getMessagesByUser(userName): Observable<string> {
    const userMessages = this.messagesList.find(m => m.user === userName).messages;
     return interval(600).pipe(
        map(i => `${userName}: ${userMessages[i]}`),
        take(3),
      );
  }

  public getUsers(): Observable<string> {
    const users = this.messagesList.map(m => m.user);
    return interval(1000).pipe(
      map(i => users[i]),
      take(2),
    );
  }
}