구독

// Via subscription creation
const subscription = await client.subscriptions.create({
  customer_id: 'cus_123',
  product_id: 'prod_monthly',
  trial_period_days: 14  // Overrides product's trial period
});

// Via checkout session
const session = await client.checkoutSessions.create({
  product_cart: [{ product_id: 'prod_monthly', quantity: 1 }],
  subscription_data: { trial_period_days: 14 }
});

const product = await client.products.create({
  name: 'Pro Plan',
  tax_category: 'saas',
  price: {
    type: 'recurring_price',
    price: 2900,                      // $29.00 per month after the trial
    currency: 'USD',
    payment_frequency_count: 1,
    payment_frequency_interval: 'Month',
    subscription_period_count: 1,
    subscription_period_interval: 'Year',
    trial_period_days: 14,            // A paid trial requires a positive trial period
    trial_amount: 500,                // $5.00 charged today
    trial_apply_discounts: false      // Discounts apply to the recurring price only
  }
});

const subscription = await client.subscriptions.retrieve('sub_123');
const payments = await client.payments.list({
  subscription_id: subscription.subscription_id
});

// Check if subscription is in trial
const isInTrial = payments.items.length === 1 && 
                  payments.items[0].total_amount === 0;

await client.subscriptions.update('sub_123', {
  next_billing_date: '2025-02-15T00:00:00Z'  // New trial end date
});

await client.subscriptions.changePlan('sub_123', {
  product_id: 'prod_pro',
  quantity: 1,
  proration_billing_mode: 'prorated_immediately'
});

// Upgrade: charges $50 (difference between $30 and $80)
// Downgrade: credits remaining value, auto-applied to renewals
await client.subscriptions.changePlan('sub_123', {
  product_id: 'prod_pro',
  quantity: 1,
  proration_billing_mode: 'difference_immediately'
});

await client.subscriptions.changePlan('sub_123', {
  product_id: 'prod_monthly',
  quantity: 1,
  proration_billing_mode: 'full_immediately'
});

await client.subscriptions.changePlan('sub_123', {
  product_id: 'prod_new_plan',
  quantity: 1,
  proration_billing_mode: 'do_not_bill'
});

await client.subscriptions.changePlan('sub_123', {
  product_id: 'prod_pro',
  quantity: 1,
  proration_billing_mode: 'difference_immediately',
  addons: [{ addon_id: 'addon_extra_seats', quantity: 2 }]  // Add add-ons
  // addons: []  // Empty array removes all existing add-ons
});

const preview = await client.subscriptions.previewChangePlan('sub_123', {
  product_id: 'prod_pro',
  quantity: 1,
  proration_billing_mode: 'prorated_immediately'
});

// Show customer the charge before confirming
console.log('You will be charged:', preview.immediate_charge.summary);

// Reactivate subscription from on_hold
const response = await client.subscriptions.updatePaymentMethod('sub_123', {
  payment_method: {
    type: 'new',
    return_url: 'https://example.com/return'
  }
});

// For on_hold subscriptions, a charge is automatically created
if (response.payment_id) {
  console.log('Charge created:', response.payment_id);
  // Redirect customer to response.payment_link to complete payment
  // Monitor webhooks for payment.succeeded and subscription.active
}

const session = await client.checkoutSessions.create({
  product_cart: [
    {
      product_id: 'prod_subscription',
      quantity: 1
    }
  ]
});

await client.subscriptions.changePlan('sub_123', {
  product_id: 'prod_new',
  quantity: 1,
  proration_billing_mode: 'difference_immediately'
});

await client.subscriptions.update('sub_123', {
  cancel_at_next_billing_date: true
});

await client.subscriptions.update('sub_123', {
  subscription_period_count: 5,
  subscription_period_interval: 'Month'
});

const onDemand = await client.subscriptions.create({
  customer_id: 'cus_123',
  product_id: 'prod_on_demand',
  on_demand: { mandate_only: true }
});

await client.subscriptions.charge(onDemand.subscription_id, {
  product_price: 4900,
  product_currency: 'USD',
  product_description: 'Extra usage for September'
});

// Update with new payment method
const response = await client.subscriptions.updatePaymentMethod('sub_123', {
  payment_method: {
    type: 'new',
    return_url: 'https://example.com/return'
  }
});

// Or use existing payment method
await client.subscriptions.updatePaymentMethod('sub_123', {
  payment_method: {
    type: 'existing',
    payment_method_id: 'pm_abc123'
  }
});

// Update payment method - automatically creates charge for remaining dues
const response = await client.subscriptions.updatePaymentMethod('sub_123', {
  payment_method: {
    type: 'new',
    return_url: 'https://example.com/return'
  }
});

if (response.payment_id) {
  // Charge created for remaining dues
  // Redirect customer to response.payment_link
  // Monitor webhooks: payment.succeeded → subscription.active
}