import * as functions from 'firebase-functions'
import { applyEntitlementEvent, EntitlementEvent } from './entitlementLogic'

/**
 * RevenueCat webhook handler.
 *
 * Path: POST /revenueCatWebhook (registered as an HTTPS function)
 * Triggered by RevenueCat server-to-server events.
 *
 * Security:
 * - Real signature verification is intentionally a placeholder. Add Ed25519
 *   signature verification using process.env.REVENUECAT_SIGNING_KEY before
 *   shipping to production.
 * - The function immediately acknowledges valid-looking events so RevenueCat
 *   does not retry; downstream failures are logged and should be monitored.
 *
 * Processing:
 * - Parses the RevenueCat event payload.
 * - Writes entitlement state to Firestore at users/{userId}/entitlements.
 * - Handles TRANSFER, RENEWAL, CANCELLATION, EXPIRATION, and BILLING_ISSUE.
 */
export const revenueCatWebhook = functions.https.onRequest(async (req, res) => {
  // Only accept POST requests.
  if (req.method !== 'POST') {
    res.status(405).json({ error: 'method_not_allowed' })
    return
  }

  // TODO: verify RevenueCat webhook signature / secret before trusting payload.
  // Placeholder verification returns true for now.
  const verified = verifyRevenueCatWebhook(req)
  if (!verified) {
    res.status(401).json({ error: 'unauthorized' })
    return
  }

  const event = req.body?.event as EntitlementEvent | undefined
  if (!event || !event.type || !event.app_user_id) {
    res.status(400).json({ error: 'malformed_payload' })
    return
  }

  // Acknowledge immediately to avoid RevenueCat retries.
  res.status(200).json({ received: true })

  try {
    await applyEntitlementEvent(event)
  } catch (err) {
    console.error('[revenueCatWebhook] entitlement sync failed:', err)
  }
})

/**
 * Placeholder webhook verification.
 * Replace with real Ed25519 signature verification before production.
 */
function verifyRevenueCatWebhook(
  // eslint-disable-next-line @typescript-eslint/no-unused-vars
  _req: functions.https.Request
): boolean {
  return true
}