import Ably from 'ably';

class LoyaltyPOS {
  constructor(apiKey, apiSecret) {
    this.apiKey = apiKey;
    this.apiSecret = apiSecret;
    this.baseUrl = 'https://api.loyalty.lt/en/shop';
    this.ably = null;
    this.currentSession = null;
  }

  async startCustomerIdentification() {
    // 1. Generate QR session
    const sessionResponse = await fetch(`${this.baseUrl}/qr-card/generate`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-API-Key': this.apiKey,
        'X-API-Secret': this.apiSecret
      },
      body: JSON.stringify({
        device_name: 'POS Terminal 1'
      })
    });
    
    const { data: session } = await sessionResponse.json();
    this.currentSession = session;
    
    // 2. Get Ably token (universal endpoint)
    const tokenResponse = await fetch(`${this.baseUrl}/ably/token`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-API-Key': this.apiKey,
        'X-API-Secret': this.apiSecret
      },
      body: JSON.stringify({
        session_id: session.session_id
      })
    });
    
    const { data: tokenData } = await tokenResponse.json();
    
    // 3. Connect to Ably and subscribe
    this.ably = new Ably.Realtime({ token: tokenData.token });
    const channel = this.ably.channels.get(session.ably_channel);
    
    return new Promise((resolve, reject) => {
      // Set timeout for session expiration
      const timeout = setTimeout(() => {
        this.cleanup();
        reject(new Error('Session expired'));
      }, 5 * 60 * 1000); // 5 minutes
      
      channel.subscribe('card_identified', (message) => {
        clearTimeout(timeout);
        this.cleanup();
        resolve(message.data.card_data);
      });
    });
  }
  
  getQRCodeUrl() {
    return this.currentSession?.qr_code;
  }
  
  cleanup() {
    if (this.ably) {
      this.ably.close();
      this.ably = null;
    }
    this.currentSession = null;
  }
}

// Usage
const pos = new LoyaltyPOS('your_api_key', 'your_api_secret');

try {
  // Display QR code on POS screen
  const qrUrl = await pos.startCustomerIdentification();
  displayQRCode(pos.getQRCodeUrl()); // Your QR code display function
  
  // Wait for customer to scan
  const cardData = await pos.startCustomerIdentification();
  
  console.log(`Welcome ${cardData.user.name}!`);
  console.log(`You have ${cardData.points} points`);
  
  if (cardData.redemption?.enabled) {
    // Calculate available discount
    const maxDiscount = Math.floor(cardData.points / cardData.redemption.points_per_currency) 
                        * cardData.redemption.currency_amount;
    console.log(`Available discount: €${maxDiscount}`);
  }
} catch (error) {
  console.error('Customer identification failed:', error);
}