payment skill

---
name: payment
description: Integrate Stripe, PayPal, and payment processors. Use when implementing payments, billing, or subscriptions.
---

# Payment Integration

Integrate payment processors securely.

## When to use

- Payment gateway integration
- Subscription billing
- Checkout flows
- Webhook handling
- PCI compliance

## Stripe integration

### Setup

```javascript
import Stripe from "stripe";

const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);

// Create payment intent
async function createPayment(amount, currency = "usd") {
  const paymentIntent = await stripe.paymentIntents.create({
    amount: amount * 100, // cents
    currency,
    automatic_payment_methods: { enabled: true },
    metadata: { order_id: "order_123" },
  });

  return {
    clientSecret: paymentIntent.client_secret,
    id: paymentIntent.id,
  };
}
```

### Subscriptions

```javascript
// Create subscription
async function createSubscription(customerId, priceId) {
  const subscription = await stripe.subscriptions.create({
    customer: customerId,
    items: [{ price: priceId }],
    payment_behavior: "default_incomplete",
    expand: ["latest_invoice.payment_intent"],
  });

  return {
    subscriptionId: subscription.id,
    clientSecret: subscription.latest_invoice.payment_intent.client_secret,
  };
}

// Cancel subscription
async function cancelSubscription(subscriptionId) {
  return await stripe.subscriptions.update(subscriptionId, {
    cancel_at_period_end: true,
  });
}
```

### Webhooks

```javascript
import { buffer } from "micro";

export async function handleWebhook(req, res) {
  const sig = req.headers["stripe-signature"];
  const body = await buffer(req);

  let event;
  try {
    event = stripe.webhooks.constructEvent(
      body,
      sig,
      process.env.STRIPE_WEBHOOK_SECRET,
    );
  } catch (err) {
    return res.status(400).send(`Webhook Error: ${err.message}`);
  }

  switch (event.type) {
    case "payment_intent.succeeded":
      await handlePaymentSuccess(event.data.object);
      break;
    case "payment_intent.payment_failed":
      await handlePaymentFailure(event.data.object);
      break;
    case "customer.subscription.deleted":
      await handleSubscriptionCanceled(event.data.object);
      break;
  }

  res.json({ received: true });
}
```

## Database schema

```sql
CREATE TABLE payments (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID REFERENCES users(id),
    stripe_payment_id VARCHAR(255) UNIQUE,
    amount DECIMAL(10,2) NOT NULL,
    currency VARCHAR(3) DEFAULT 'usd',
    status VARCHAR(50) NOT NULL,
    metadata JSONB,
    created_at TIMESTAMP DEFAULT NOW()
);

CREATE TABLE subscriptions (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID REFERENCES users(id),
    stripe_subscription_id VARCHAR(255) UNIQUE,
    stripe_customer_id VARCHAR(255),
    plan VARCHAR(50) NOT NULL,
    status VARCHAR(50) NOT NULL,
    current_period_start TIMESTAMP,
    current_period_end TIMESTAMP,
    canceled_at TIMESTAMP,
    created_at TIMESTAMP DEFAULT NOW()
);

CREATE INDEX idx_payments_user ON payments(user_id);
CREATE INDEX idx_subscriptions_user ON subscriptions(user_id);
```

## Security checklist

- [ ] Never log full card numbers
- [ ] Use HTTPS everywhere
- [ ] Validate webhook signatures
- [ ] Implement idempotency keys
- [ ] Store only necessary data
- [ ] Use Stripe.js for card collection
- [ ] Handle errors gracefully

## Examples

**Input:** "Add Stripe payments"
**Action:** Set up Stripe, create payment intent endpoint, add webhook handler

**Input:** "Implement subscriptions"
**Action:** Create subscription flow, handle lifecycle webhooks, add cancellation