// server/supabase/functions/stripe-webhook/index.ts
// Stripe Webhook 핸들러 — checkout 완료, 구독 갱신/취소 등 이벤트 처리.
// Supabase 대시보드 → Functions → stripe-webhook 의 verify_jwt를 false로 설정해야 함
// (Stripe는 JWT 없이 호출, 대신 signature로 검증).
//
// 환경변수:
//   STRIPE_SECRET_KEY
//   STRIPE_WEBHOOK_SECRET (Stripe 대시보드에서 발급)

import { createServiceRoleClient } from '../_shared/quota.ts'

interface StripeEvent {
  id: string
  type: string
  data: {
    object: Record<string, unknown>
  }
}

/**
 * Stripe webhook signature 검증 — Web Crypto API 기반 HMAC-SHA256.
 *
 * Stripe-Signature 헤더 형식: "t=TIMESTAMP,v1=SIG,v1=SIG2,..."
 * 검증 방식: HMAC_SHA256(secret, `${timestamp}.${payload}`) 를 16진수로 인코딩하여
 * v1 시그니처 중 하나와 일치하면 valid.
 *
 * 또한 timestamp가 tolerance(5분) 이상 벗어나면 reject (replay 공격 방지).
 *
 * 참고: https://stripe.com/docs/webhooks/signatures
 */
async function verifyStripeSignature(
  payload: string,
  signatureHeader: string,
  secret: string,
  toleranceSec = 300
): Promise<boolean> {
  if (!signatureHeader || !secret || !payload) return false

  // 헤더 파싱
  const parts = signatureHeader.split(',').map((p) => p.trim())
  const timestampEntry = parts.find((p) => p.startsWith('t='))
  const v1Signatures = parts.filter((p) => p.startsWith('v1=')).map((p) => p.slice(3))

  if (!timestampEntry || v1Signatures.length === 0) return false

  const timestamp = Number(timestampEntry.slice(2))
  if (!Number.isFinite(timestamp)) return false

  // Replay 방지: 5분 이상 오래된 요청 거부
  const nowSec = Math.floor(Date.now() / 1000)
  if (Math.abs(nowSec - timestamp) > toleranceSec) {
    return false
  }

  // HMAC-SHA256 계산
  const signedPayload = `${timestamp}.${payload}`
  const key = await crypto.subtle.importKey(
    'raw',
    new TextEncoder().encode(secret),
    { name: 'HMAC', hash: 'SHA-256' },
    false,
    ['sign']
  )
  const sigBuffer = await crypto.subtle.sign('HMAC', key, new TextEncoder().encode(signedPayload))
  const expectedHex = Array.from(new Uint8Array(sigBuffer))
    .map((b) => b.toString(16).padStart(2, '0'))
    .join('')

  // 타이밍 공격 방지: constant-time 비교
  for (const v1 of v1Signatures) {
    if (constantTimeEqual(v1, expectedHex)) {
      return true
    }
  }
  return false
}

function constantTimeEqual(a: string, b: string): boolean {
  if (a.length !== b.length) return false
  let mismatch = 0
  for (let i = 0; i < a.length; i++) {
    mismatch |= a.charCodeAt(i) ^ b.charCodeAt(i)
  }
  return mismatch === 0
}

// @ts-expect-error — Deno 런타임 전역
Deno.serve(async (req: Request) => {
  if (req.method !== 'POST') {
    return new Response('Method not allowed', { status: 405 })
  }

  // @ts-expect-error — Deno.env
  const webhookSecret = Deno.env.get('STRIPE_WEBHOOK_SECRET') ?? ''
  if (!webhookSecret) {
    return new Response('Webhook secret not configured', { status: 503 })
  }

  const signature = req.headers.get('stripe-signature') ?? ''
  const payload = await req.text()

  const valid = await verifyStripeSignature(payload, signature, webhookSecret)
  if (!valid) {
    return new Response('Invalid signature', { status: 400 })
  }

  let event: StripeEvent
  try {
    event = JSON.parse(payload) as StripeEvent
  } catch {
    return new Response('Invalid JSON', { status: 400 })
  }

  const serviceClient = createServiceRoleClient()

  try {
    switch (event.type) {
      case 'checkout.session.completed': {
        const session = event.data.object as {
          customer: string
          subscription: string
          metadata?: { user_id?: string; tier?: string }
        }
        const userId = session.metadata?.user_id
        const tier = session.metadata?.tier
        if (userId && tier) {
          await serviceClient.from('subscriptions').upsert({
            user_id: userId,
            stripe_customer_id: session.customer,
            stripe_subscription_id: session.subscription,
            tier,
            status: 'active'
          })
        }
        break
      }

      case 'customer.subscription.updated':
      case 'customer.subscription.created': {
        const sub = event.data.object as {
          id: string
          customer: string
          status: string
          current_period_start?: number
          current_period_end?: number
          cancel_at?: number | null
        }
        await serviceClient
          .from('subscriptions')
          .update({
            status: sub.status,
            current_period_start: sub.current_period_start
              ? new Date(sub.current_period_start * 1000).toISOString()
              : null,
            current_period_end: sub.current_period_end
              ? new Date(sub.current_period_end * 1000).toISOString()
              : null,
            cancel_at: sub.cancel_at ? new Date(sub.cancel_at * 1000).toISOString() : null
          })
          .eq('stripe_subscription_id', sub.id)
        break
      }

      case 'customer.subscription.deleted': {
        const sub = event.data.object as { id: string }
        await serviceClient
          .from('subscriptions')
          .update({ tier: 'free', status: 'canceled' })
          .eq('stripe_subscription_id', sub.id)
        break
      }

      default:
        // 기타 이벤트는 무시
        break
    }

    return new Response(JSON.stringify({ received: true }), {
      status: 200,
      headers: { 'Content-Type': 'application/json' }
    })
  } catch (err) {
    const message = err instanceof Error ? err.message : 'Unknown error'
    return new Response(JSON.stringify({ error: message }), {
      status: 500,
      headers: { 'Content-Type': 'application/json' }
    })
  }
})