Text editor undo

interface Command {
  execute(): void;
  undo(): void;
}

class Document {
  private content = "";

  append(text: string) {
    this.content += text;
  }

  removeLast(count: number) {
    this.content = this.content.slice(0, -count);
  }

  print() {
    console.log(this.content);
  }
}

class AppendTextCommand implements Command {
  constructor(
    private readonly document: Document,
    private readonly text: string,
  ) {}

  execute() {
    this.document.append(this.text);
  }

  undo() {
    this.document.removeLast(this.text.length);
  }
}

class Editor {
  private readonly history: Command[] = [];

  run(command: Command) {
    command.execute();
    this.history.push(command);
  }

  undo() {
    this.history.pop()?.undo();
  }
}

const document = new Document();
const editor = new Editor();

editor.run(new AppendTextCommand(document, "Hello, "));
editor.run(new AppendTextCommand(document, "world!"));

document.print();

editor.undo();
document.print();