Full Cart API Implementation

// Full checkout flow
async function checkout(domain, productVariantId) {
  // 1. Authenticate
  const authResponse = await fetch('https://api.firmly.work/api/v1/browser-session', {
    method: 'POST',
    headers: { 'x-firmly-app-id': 'YOUR_APP_ID' }
  });
  const { access_token } = await authResponse.json();

  const headers = {
    'x-firmly-authorization': access_token,
    'Content-Type': 'application/json'
  };

  // 2. Add to cart
  const cartResponse = await fetch(
    `https://api.firmly.work/api/v2/domains/${domain}/cart/line-items`,
    {
      method: 'POST',
      headers,
      body: JSON.stringify({
        add_to_cart_ref: { variant_id: productVariantId },
        quantity: 1
      })
    }
  );
  const cart = await cartResponse.json();

  // 3. Set shipping
  const shippingResponse = await fetch(
    `https://api.firmly.work/api/v2/domains/${domain}/cart/shipping-info`,
    {
      method: 'POST',
      headers,
      body: JSON.stringify({
        first_name: 'John',
        last_name: 'Doe',
        email: '[email protected]',
        phone: '555-123-4567',
        address1: '123 Main St',
        city: 'New York',
        state_or_province: 'NY',
        postal_code: '10001',
        country: 'US'
      })
    }
  );
  const cartWithShipping = await shippingResponse.json();

  // 4. Select shipping method
  const shipment = cartWithShipping.shipments[0];
  const shippingMethod = shipment.shipping_method_options[0];
  
  await fetch(
    `https://api.firmly.work/api/v2/domains/${domain}/cart/shipment/methods`,
    {
      method: 'POST',
      headers,
      body: JSON.stringify({
        shipment_id: shipment.shipment_id,
        shipping_method_id: shippingMethod.id
      })
    }
  );

  // 5. Get public key and encrypt card
  const keyResponse = await fetch(
    'https://cc.firmly.work/api/v1/payment/key',
    { headers }
  );
  const { key, kid } = await keyResponse.json();
  
  // Encrypt card data (see Complete Order API docs for encryption details)
  const encryptedCard = await encryptCardData(
    { number: '4242424242424242', cvv: '123', exp_month: '12', exp_year: '2025' },
    key,
    kid
  );

  // 6. Complete order
  const orderResponse = await fetch(
    `https://cc.firmly.work/api/v2/payment/domains/${domain}/complete-order`,
    {
      method: 'POST',
      headers,
      body: JSON.stringify({
        encrypted_card: encryptedCard,
        billing_info: {
          first_name: 'John',
          last_name: 'Doe',
          email: '[email protected]',
          address1: '123 Main St',
          city: 'New York',
          state_or_province: 'NY',
          postal_code: '10001',
          country: 'US'
        }
      })
    }
  );

  const order = await orderResponse.json();
  return order;
}