tiers:
  free:
    price: 0
    included_calls: 1000/month
    rate_limit: 10/min
    endpoints: [/v1/basic/*]
    support: community
  pro:
    price: 49/month
    included_calls: 50000/month
    rate_limit: 100/min
    endpoints: [/v1/*]
    support: email
    overage: $0.002/call
  enterprise:
    price: custom
    included_calls: custom
    rate_limit: custom
    endpoints: [/v1/*, /v1/admin/*]
    support: dedicated
    sla: 99.9%

const stripe = require('stripe')(process.env.STRIPE_SECRET_KEY);

// 1. Create product
const product = await stripe.products.create({
  name: 'API Access - Pro Tier',
});

// 2. Create metered price (per-unit usage)
const meteredPrice = await stripe.prices.create({
  product: product.id,
  currency: 'usd',
  recurring: {
    interval: 'month',
    usage_type: 'metered',
    aggregate_usage: 'sum',
  },
  unit_amount: 0.2, // $0.002 per call (in cents: 0.2)
  billing_scheme: 'per_unit',
});

// 3. Create base price for the tier
const basePrice = await stripe.prices.create({
  product: product.id,
  currency: 'usd',
  recurring: { interval: 'month' },
  unit_amount: 4900, // $49.00
});

// 4. Subscribe the customer to both prices
const subscription = await stripe.subscriptions.create({
  customer: 'cus_xxx',
  items: [
    { price: basePrice.id },
    { price: meteredPrice.id },
  ],
});

// Find the metered subscription item
const subscription = await stripe.subscriptions.retrieve('sub_xxx');
const meteredItem = subscription.items.data.find(
  (item) => item.price.recurring.usage_type === 'metered'
);

// Report usage - increment by the count since last report
await stripe.subscriptionItems.createUsageRecord(meteredItem.id, {
  quantity: 1250, // API calls in this reporting period
  timestamp: Math.floor(Date.now() / 1000),
  action: 'increment',
});

const Redis = require('ioredis');
const redis = new Redis(process.env.REDIS_URL);

const TIER_LIMITS = {
  free: { rpm: 10, window: 60 },
  pro: { rpm: 100, window: 60 },
  enterprise: { rpm: 1000, window: 60 },
};

async function rateLimiter(req, res, next) {
  const apiKey = req.headers['x-api-key'];
  const tier = await getTierForApiKey(apiKey); // your lookup
  const limit = TIER_LIMITS[tier];
  const key = `ratelimit:${apiKey}`;
  const now = Date.now();

  // Sliding window using sorted set
  await redis.zremrangebyscore(key, 0, now - limit.window * 1000);
  const count = await redis.zcard(key);

  if (count >= limit.rpm) {
    res.set('Retry-After', String(limit.window));
    res.set('X-RateLimit-Limit', String(limit.rpm));
    res.set('X-RateLimit-Remaining', '0');
    return res.status(429).json({ error: 'Rate limit exceeded' });
  }

  await redis.zadd(key, now, `${now}-${Math.random()}`);
  await redis.expire(key, limit.window);

  res.set('X-RateLimit-Limit', String(limit.rpm));
  res.set('X-RateLimit-Remaining', String(limit.rpm - count - 1));
  next();
}

const usageBuffer = new Map(); // apiKey -> count

function usageTracker(req, res, next) {
  const apiKey = req.headers['x-api-key'];
  usageBuffer.set(apiKey, (usageBuffer.get(apiKey) || 0) + 1);
  next();
}

// Flush every hour
setInterval(async () => {
  for (const [apiKey, count] of usageBuffer.entries()) {
    const subItemId = await getMeteredSubItemForKey(apiKey);
    if (subItemId && count > 0) {
      await stripe.subscriptionItems.createUsageRecord(subItemId, {
        quantity: count,
        timestamp: Math.floor(Date.now() / 1000),
        action: 'increment',
      });
    }
  }
  usageBuffer.clear();
}, 60 * 60 * 1000);

async function checkUsageThresholds(customerId, currentUsage, includedCalls) {
  const percentage = (currentUsage / includedCalls) * 100;
  const thresholds = [80, 100, 120];

  for (const threshold of thresholds) {
    if (percentage >= threshold) {
      const alreadyNotified = await hasNotifiedThreshold(customerId, threshold);
      if (!alreadyNotified) {
        await sendUsageAlert(customerId, {
          currentUsage,
          includedCalls,
          percentage,
          threshold,
          message: threshold >= 100
            ? `You have exceeded your included ${includedCalls} API calls. Overage billing is active.`
            : `You have used ${percentage.toFixed(0)}% of your included API calls.`,
        });
        await markThresholdNotified(customerId, threshold);
      }
    }
  }
}