SmartHomeCommandPattern.js

// Receiver: Lamp
class Lamp {
  turnOn() {
    console.log("Lamp is ON");
  }

  turnOff() {
    console.log("Lamp is OFF");
  }
}

// Receiver: Music Player
class MusicPlayer {
  playSong(song) {
    console.log(`Playing song: ${song}`);
  }

  stop() {
    console.log("Music stopped");
  }
}

// Command Interface
class Command {
  execute() {}
  undo() {}
}

// Concrete Commands: Lamp
class TurnOnLampCommand extends Command {
  constructor(lamp) {
    super();
    this.lamp = lamp;
  }

  execute() {
    this.lamp.turnOn();
  }

  undo() {
    this.lamp.turnOff();
  }
}

class TurnOffLampCommand extends Command {
  constructor(lamp) {
    super();
    this.lamp = lamp;
  }

  execute() {
    this.lamp.turnOff();
  }

  undo() {
    this.lamp.turnOn();
  }
}

// Concrete Commands: Music Player
class PlayMusicCommand extends Command {
  constructor(musicPlayer, song) {
    super();
    this.musicPlayer = musicPlayer;
    this.song = song;
  }

  execute() {
    this.musicPlayer.playSong(this.song);
  }

  undo() {
    this.musicPlayer.stop();
  }
}

class StopMusicCommand extends Command {
  constructor(musicPlayer) {
    super();
    this.musicPlayer = musicPlayer;
  }

  execute() {
    this.musicPlayer.stop();
  }

  // Optional: Could replay last song if stored
  undo() {
    console.log("No song to replay");
  }
}

// Invoker: Smart Home Controller
class SmartHomeController {
  constructor() {
    this.history = [];
  }

  pressButton(command) {
    command.execute();
    this.history.push(command);
  }

  pressUndo() {
    const command = this.history.pop();
    if (command) {
      command.undo();
    }
  }
}

// Usage
const lamp = new Lamp();
const musicPlayer = new MusicPlayer();
const controller = new SmartHomeController();

const lampOn = new TurnOnLampCommand(lamp);
const lampOff = new TurnOffLampCommand(lamp);
const playMusic = new PlayMusicCommand(musicPlayer, "Imagine");

controller.pressButton(lampOn);      // Lamp is ON
controller.pressButton(playMusic);   // Playing song: Imagine
controller.pressUndo();             // Music stopped
controller.pressUndo();             // Lamp is OFF