Facade Pattern

// Facade Pattern Example

// Complex subsystem classes
class CPU {
  freeze() {
    console.log('CPU: Freezing processor');
  }
  
  jump(position) {
    console.log(`CPU: Jumping to position ${position}`);
  }
  
  execute() {
    console.log('CPU: Executing instructions');
  }
}

class Memory {
  load(position, data) {
    console.log(`Memory: Loading data "${data}" at position ${position}`);
  }
}

class HardDrive {
  read(lba, size) {
    console.log(`HardDrive: Reading ${size} bytes from LBA ${lba}`);
    return 'boot data';
  }
}

class GPU {
  initialize() {
    console.log('GPU: Initializing graphics processor');
  }
  
  renderBootScreen() {
    console.log('GPU: Rendering boot screen');
  }
}

class PowerSupply {
  turnOn() {
    console.log('PowerSupply: Providing power to components');
  }
  
  turnOff() {
    console.log('PowerSupply: Cutting power to components');
  }
}

// Facade class
class ComputerFacade {
  constructor() {
    this.cpu = new CPU();
    this.memory = new Memory();
    this.hardDrive = new HardDrive();
    this.gpu = new GPU();
    this.powerSupply = new PowerSupply();
  }
  
  start() {
    console.log('=== Starting Computer ===');
    this.powerSupply.turnOn();
    this.gpu.initialize();
    this.gpu.renderBootScreen();
    this.cpu.freeze();
    this.memory.load(0x00, this.hardDrive.read(0x00, 1024));
    this.cpu.jump(0x00);
    this.cpu.execute();
    console.log('=== Computer Started Successfully ===\n');
  }
  
  shutdown() {
    console.log('=== Shutting Down Computer ===');
    this.cpu.freeze();
    this.powerSupply.turnOff();
    console.log('=== Computer Shut Down ===\n');
  }
}

// Usage - Simple interface hiding complexity
const computer = new ComputerFacade();
computer.start();
computer.shutdown();

// Another example: Home Theater Facade
class Amplifier {
  on() { console.log('Amplifier: Turning on'); }
  off() { console.log('Amplifier: Turning off'); }
  setVolume(level) { console.log(`Amplifier: Setting volume to ${level}`); }
  setSurroundSound() { console.log('Amplifier: Surround sound enabled'); }
}

class DVDPlayer {
  on() { console.log('DVD Player: Turning on'); }
  off() { console.log('DVD Player: Turning off'); }
  play(movie) { console.log(`DVD Player: Playing "${movie}"`); }
  stop() { console.log('DVD Player: Stopped'); }
}

class Projector {
  on() { console.log('Projector: Turning on'); }
  off() { console.log('Projector: Turning off'); }
  wideScreenMode() { console.log('Projector: Wide screen mode enabled'); }
}

class TheaterLights {
  dim(level) { console.log(`Lights: Dimming to ${level}%`); }
  on() { console.log('Lights: Turning on'); }
}

class PopcornMaker {
  on() { console.log('Popcorn Maker: Turning on'); }
  off() { console.log('Popcorn Maker: Turning off'); }
  pop() { console.log('Popcorn Maker: Popping corn!'); }
}

// Home Theater Facade
class HomeTheaterFacade {
  constructor() {
    this.amp = new Amplifier();
    this.dvd = new DVDPlayer();
    this.projector = new Projector();
    this.lights = new TheaterLights();
    this.popcorn = new PopcornMaker();
  }
  
  watchMovie(movie) {
    console.log('=== Get ready to watch a movie! ===');
    
    this.popcorn.on();
    this.popcorn.pop();
    
    this.lights.dim(10);
    
    this.projector.on();
    this.projector.wideScreenMode();
    
    this.amp.on();
    this.amp.setSurroundSound();
    this.amp.setVolume(8);
    
    this.dvd.on();
    this.dvd.play(movie);
    
    console.log('=== Enjoy your movie! ===\n');
  }
  
  endMovie() {
    console.log('=== Shutting down theater... ===');
    
    this.dvd.stop();
    this.dvd.off();
    
    this.amp.off();
    this.projector.off();
    this.lights.on();
    this.popcorn.off();
    
    console.log('=== Theater shut down ===\n');
  }
}

// Usage
const homeTheater = new HomeTheaterFacade();
homeTheater.watchMovie('The Matrix');
homeTheater.endMovie();

// API Facade example
class APIFacade {
  constructor() {
    this.baseURL = 'https://api.example.com';
  }
  
  async getUser(userId) {
    try {
      // Hide complex authentication, headers, error handling
      const token = await this._authenticate();
      const response = await fetch(`${this.baseURL}/users/${userId}`, {
        headers: {
          'Authorization': `Bearer ${token}`,
          'Content-Type': 'application/json'
        }
      });
      
      if (!response.ok) {
        throw new Error('Failed to fetch user');
      }
      
      return await response.json();
    } catch (error) {
      console.error('Error fetching user:', error);
      throw error;
    }
  }
  
  async _authenticate() {
    // Complex authentication logic hidden
    return 'mock-token';
  }
}

// Simple usage hiding all complexity
const api = new APIFacade();
// api.getUser(123).then(user => console.log(user));