Build usage threshold alerts with Chargebee

# One POST per threshold. Store the returned alert.id for each.
# --- Alert 1: 70% warn ---
curl -s -X POST https://{SITE}.chargebee.com/api/v2/alerts \
  -u {API_KEY}: \
  -d type=usage_exceeded \
  -d "name=ai_actions_warn_70" \
  -d metered_feature_id=ai_actions \
  -d "threshold[value]=70"
# Save as: ALERT_WARN_ID = response.alert.id

# --- Alert 2: 100% hard gate ---
curl -s -X POST https://{SITE}.chargebee.com/api/v2/alerts \
  -u {API_KEY}: \
  -d type=usage_exceeded \
  -d "name=ai_actions_gate_100" \
  -d metered_feature_id=ai_actions \
  -d "threshold[value]=100"
# Save as: ALERT_GATE_ID = response.alert.id

// 1. Verify signature — reject spoofed requests
const sig = req.headers['chargebee-webhook-signature']
if (!verifyHmac(sig, req.rawBody, WEBHOOK_SECRET)) {
  return res.status(401).send('Invalid signature')
}

// 2. Acknowledge fast — Chargebee retries on timeout
res.status(200).send('OK')

const { alert, alert_status } = req.body.content
if (alert_status.alarm_status !== "in_alarm") return  // cleared = billing period reset

// 3. Deduplicate — Chargebee retries on non-2xx
if (await redis.get(`cb_event:${req.body.id}`)) return
await redis.setex(`cb_event:${req.body.id}`, 86400, 1)

// 4. Route by alert.id
const subId = alert_status.subscription_id
const sub  = await chargebee.subscription.retrieve(subId).request()

if (alert.id === process.env.ALERT_WARN_ID) {
  await sendWarningEmail({ customer: sub.customer, pct: 70 })
}

if (alert.id === process.env.ALERT_GATE_ID) {
  await chargebee.subscriptionEntitlement.setAvailability(subId, {
    is_enabled: false,
    "subscription_entitlements[feature_id][0]": "ai_actions",
  })
  await sendLimitReachedEmail({ customer: sub.customer })
}

curl -s -X POST https://{SITE}.chargebee.com/api/v2/alerts \
  -u {API_KEY}: \
  -d type=usage_exceeded \
  -d "name=ai_actions_am_alert_70" \
  -d metered_feature_id=ai_actions \
  -d "threshold[value]=70" \
  # Scope: Growth + Enterprise plans only
  -d "filter_conditions[field][0]=plan_price_id" \
  -d "filter_conditions[operator][0]=not_equals" \
  -d "filter_conditions[value][0]=starter_monthly_usd"
# Save as: ALERT_AM_ID = response.alert.id

const sig = req.headers['chargebee-webhook-signature']
if (!verifyHmac(sig, req.rawBody, WEBHOOK_SECRET)) return res.status(401).end()
res.status(200).send('OK')

const { alert, alert_status } = req.body.content
if (alert_status.alarm_status !== "in_alarm") return
if (await redis.get(`cb_event:${req.body.id}`)) return
await redis.setex(`cb_event:${req.body.id}`, 86400, 1)

// Enrich: retrieve full subscription + customer record
const sub = await chargebee.subscription
  .retrieve(alert_status.subscription_id).request()

// Confirm it's still in_alarm — guard against race conditions
const statuses = await chargebee.alertStatus
  .list({ subscription_id: alert_status.subscription_id }).request()
const current = statuses.list.find(
  x => x.alert_status.alert_id === alert.id
)
if (current?.alert_status.alarm_status !== "in_alarm") return

// No gate. Notify AM — they own the conversation.
await notifySlackAM({
  customer:    sub.customer,
  planId:      sub.subscription.plan_id,
  subId:       alert_status.subscription_id,
  triggeredAt: alert_status.alarm_triggered_at,
})

const thresholds = [
  { name: "ai_nudge_50",  value: 50, env: "ALERT_ID_50"  },
  { name: "ai_warn_80",   value: 80, env: "ALERT_ID_80"  },
  { name: "ai_gate_100",  value: 100, env: "ALERT_ID_100" },
]

for (const t of thresholds) {
  const res = await chargebee.request("POST", "/api/v2/alerts", {
    type: "usage_exceeded",
    name: t.name,
    metered_feature_id: "ai_actions",
    "threshold[value]": t.value,
  })
  console.log(t.env, '=', res.alert.id)  // paste into .env
}

const sig = req.headers['chargebee-webhook-signature']
if (!verifyHmac(sig, req.rawBody, WEBHOOK_SECRET)) return res.status(401).end()
res.status(200).send('OK')

const { alert, alert_status } = req.body.content
if (alert_status.alarm_status !== "in_alarm") return
if (await redis.get(`cb_event:${req.body.id}`)) return
await redis.setex(`cb_event:${req.body.id}`, 86400, 1)

const sub = await chargebee.subscription.retrieve(alert_status.subscription_id).request()

// Route by alert.id — your mapping, not a Chargebee concept
const actions = {
  [process.env.ALERT_ID_50]:  () => showInAppBanner(alert_status.subscription_id),
  [process.env.ALERT_ID_80]:  () => sendWarningEmail({ customer: sub.customer, pct: 80 }),
  [process.env.ALERT_ID_100]: async () => {
    await chargebee.subscriptionEntitlement.setAvailability(
      alert_status.subscription_id,
      { is_enabled: false, "subscription_entitlements[feature_id][0]": "ai_actions" }
    )
    await sendLimitReachedEmail({ customer: sub.customer })
  },
}
await actions[alert.id]?.()

curl -s -X POST https://{SITE}.chargebee.com/api/v2/alerts \
  -u {API_KEY}: \
  -d type=usage_exceeded \
  -d "name=ai_credits_low_60" \
  -d metered_feature_id=ai_credits \
  -d "threshold[value]=60"
# Save as: ALERT_CREDITS_ID = response.alert.id

const sig = req.headers['chargebee-webhook-signature']
if (!verifyHmac(sig, req.rawBody, WEBHOOK_SECRET)) return res.status(401).end()
res.status(200).send('OK')

const { alert, alert_status } = req.body.content
if (alert_status.alarm_status !== "in_alarm") return
if (await redis.get(`cb_event:${req.body.id}`)) return
await redis.setex(`cb_event:${req.body.id}`, 86400, 1)

const sub = await chargebee.subscription.retrieve(alert_status.subscription_id).request()

// Generate a Chargebee-hosted top-up checkout URL
const page = await chargebee.hostedPage
  .checkoutOneTimeForItems({
    subscription_id: alert_status.subscription_id,
    item_prices: [{ item_price_id: "ai_credits_topup_1000", quantity: 1 }],
  }).request()

await sendCreditLowEmail({
  customer:  sub.customer,
  topup_url: page.hosted_page.url,   // CB-hosted, no PCI scope
  credits_remaining: 400,          // retrieve live if needed
})