サブスクの『今・誰が・どの権利を持つか』を取り違えない — Rork で実装するエンタイトルメント状態機械の設計

// ❌ アンチパターン: 期限だけで判定する
function canUseProFeature(user: User): boolean {
  return user.subscriptionExpiresAt > Date.now();
}

// Cloudflare D1 / KV のスキーマ例
type SubscriptionEvent = {
  notificationUuid: string;        // Apple の場合は ASSN V2 の notificationUUID
  eventType: string;               // 'DID_RENEW' | 'EXPIRED' | 'REFUND' | 'REFUND_REVERSED' | ...
  productId: string;
  originalTransactionId: string;   // サブスク全体を貫く一意のID
  receivedAt: number;              // サーバー受信時刻（ms）
  signedDate: number;              // Apple が発行した時刻（ms、検証済み）
  rawPayload: string;              // JWS 検証後の JSON 文字列
};
 
type Entitlement = {
  userId: string;
  productId: string;
  status: 'active' | 'grace' | 'expired' | 'refunded' | 'revoked' | 'family_shared';
  expiresAt: number;
  willAutoRenew: boolean;
  inFamily: boolean;               // 家族共有で得た権限かどうか
  lastEventUuid: string;           // 最後に状態を変えたイベントの UUID（冪等化）
  updatedAt: number;
};

// イベント正規化レイヤー
type NormalizedEvent =
  | { kind: 'started'; userId: string; originalTransactionId: string; productId: string; expiresAt: number; isFamily: boolean }
  | { kind: 'renewed'; userId: string; originalTransactionId: string; expiresAt: number }
  | { kind: 'auto_renew_off'; userId: string; originalTransactionId: string }
  | { kind: 'auto_renew_on'; userId: string; originalTransactionId: string }
  | { kind: 'grace_period'; userId: string; originalTransactionId: string; expiresAt: number }
  | { kind: 'expired'; userId: string; originalTransactionId: string; reason: 'voluntary' | 'billing_retry' | 'price_increase' }
  | { kind: 'refunded'; userId: string; originalTransactionId: string; refundedAt: number }
  | { kind: 'refund_reversed'; userId: string; originalTransactionId: string };
 
// ASSN V2 -> NormalizedEvent
function normalizeAssnV2(payload: AssnV2Payload, signedDate: number): NormalizedEvent | null {
  const t = payload.notificationType;
  const sub = payload.subType;
  const otx = payload.data.signedTransactionInfo.originalTransactionId;
  const userId = payload.data.signedTransactionInfo.appAccountToken; // 事前にバインドが必要
  if (!userId) return null;
 
  switch (t) {
    case 'SUBSCRIBED':
      return { kind: 'started', userId, originalTransactionId: otx,
               productId: payload.data.signedTransactionInfo.productId,
               expiresAt: payload.data.signedTransactionInfo.expiresDate,
               isFamily: payload.data.signedTransactionInfo.inAppOwnershipType === 'FAMILY_SHARED' };
    case 'DID_RENEW':
      return { kind: 'renewed', userId, originalTransactionId: otx,
               expiresAt: payload.data.signedTransactionInfo.expiresDate };
    case 'DID_CHANGE_RENEWAL_STATUS':
      return sub === 'AUTO_RENEW_DISABLED'
        ? { kind: 'auto_renew_off', userId, originalTransactionId: otx }
        : { kind: 'auto_renew_on', userId, originalTransactionId: otx };
    case 'DID_FAIL_TO_RENEW':
      return sub === 'GRACE_PERIOD'
        ? { kind: 'grace_period', userId, originalTransactionId: otx,
            expiresAt: payload.data.signedRenewalInfo.gracePeriodExpiresDate }
        : null; // GRACE_PERIOD でなければここでは扱わない（後続の EXPIRED を待つ）
    case 'EXPIRED':
      return { kind: 'expired', userId, originalTransactionId: otx,
               reason: sub === 'VOLUNTARY' ? 'voluntary' :
                       sub === 'PRICE_INCREASE' ? 'price_increase' : 'billing_retry' };
    case 'REFUND':
      return { kind: 'refunded', userId, originalTransactionId: otx, refundedAt: signedDate };
    case 'REFUND_REVERSED':
      return { kind: 'refund_reversed', userId, originalTransactionId: otx };
    default:
      return null; // 未対応の通知は無視（テストやポリシー外イベント）
  }
}

async function applyEvent(env: Env, evt: NormalizedEvent): Promise<void> {
  const key = `${evt.userId}:${evt.originalTransactionId}`;
  const current = await env.DB.prepare(
    'SELECT * FROM entitlements WHERE user_id = ? AND original_tx = ?'
  ).bind(evt.userId, evt.originalTransactionId).first<Entitlement>();
 
  // 冪等性: 同じイベントを2回処理しない
  if (current?.lastEventUuid === evt.notificationUuid) return;
 
  // 重要: 古いイベントが新しい状態を上書きしないようにする
  if (current && evt.signedDate < current.signedDate) {
    console.warn('[entitlement] stale event, skipping', { key, evtKind: evt.kind });
    return;
  }
 
  let next: Partial<Entitlement>;
 
  switch (evt.kind) {
    case 'started':
    case 'renewed':
      next = {
        status: 'active',
        expiresAt: evt.expiresAt,
        willAutoRenew: true,
        inFamily: 'isFamily' in evt ? evt.isFamily : current?.inFamily ?? false,
      };
      break;
    case 'auto_renew_off':
      next = { willAutoRenew: false }; // status は変えない（期限まで active のまま）
      break;
    case 'auto_renew_on':
      next = { willAutoRenew: true };
      break;
    case 'grace_period':
      next = { status: 'grace', expiresAt: evt.expiresAt };
      break;
    case 'expired':
      // ⚠️ 重要: 即座に剥奪しない。短時間内に DID_RENEW が来る可能性があるため
      // 60秒の遅延を挟むのが本番運用の経験則
      next = { status: 'expired', willAutoRenew: false };
      break;
    case 'refunded':
      next = { status: 'refunded', willAutoRenew: false };
      break;
    case 'refund_reversed':
      // 返金が取り消された場合、元の expiresAt がまだ未来なら復活させる
      if (current && current.expiresAt > Date.now()) {
        next = { status: 'active' };
      } else {
        next = { status: 'expired' };
      }
      break;
    default:
      return;
  }
 
  await env.DB.prepare(`
    INSERT INTO entitlements (user_id, product_id, status, expires_at, will_auto_renew, in_family, last_event_uuid, signed_date, updated_at)
    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
    ON CONFLICT(user_id, original_tx) DO UPDATE SET
      status = excluded.status,
      expires_at = COALESCE(excluded.expires_at, entitlements.expires_at),
      will_auto_renew = excluded.will_auto_renew,
      last_event_uuid = excluded.last_event_uuid,
      signed_date = excluded.signed_date,
      updated_at = excluded.updated_at
  `).bind(
    evt.userId, current?.productId ?? '',
    next.status ?? current?.status ?? 'active',
    next.expiresAt ?? current?.expiresAt ?? 0,
    next.willAutoRenew ?? current?.willAutoRenew ?? false,
    next.inFamily ?? current?.inFamily ?? false,
    evt.notificationUuid,
    evt.signedDate,
    Date.now(),
  ).run();
}

// hooks/useEntitlement.ts
import { useEffect, useState } from 'react';
import * as InAppPurchases from 'expo-in-app-purchases';
 
type EntitlementStatus = 'loading' | 'active' | 'grace' | 'expired' | 'refunded';
 
export function useEntitlement(productId: string): { status: EntitlementStatus; revalidate: () => Promise<void> } {
  const [status, setStatus] = useState<EntitlementStatus>('loading');
 
  const fetchFromServer = async () => {
    try {
      const res = await fetch('/api/entitlements/me', { credentials: 'include' });
      if (!res.ok) throw new Error(`HTTP ${res.status}`);
      const data = await res.json() as { entitlements: { productId: string; status: EntitlementStatus; expiresAt: number }[] };
      const ent = data.entitlements.find(e => e.productId === productId);
      if (!ent) { setStatus('expired'); return; }
      // grace と active は同じく利用可能扱い、ただし UI で警告は出す
      if ((ent.status === 'active' || ent.status === 'grace') && ent.expiresAt > Date.now()) {
        setStatus(ent.status);
      } else {
        setStatus(ent.status);
      }
    } catch (e) {
      console.error('[entitlement] fetch failed', e);
      // ネットワーク失敗時はキャッシュから読む。ローカルの secureStore が望ましい
      setStatus('expired'); // フェイルクローズ（不明なら閉じる）
    }
  };
 
  useEffect(() => {
    fetchFromServer();
    // StoreKit 2 transactions.updates 相当のリスナー
    const sub = InAppPurchases.setPurchaseListener(({ responseCode }) => {
      if (responseCode === InAppPurchases.IAPResponseCode.OK) {
        // 購入直後はサーバーの ASSN V2 受信より早いことがあるため、少し待ってから revalidate
        setTimeout(fetchFromServer, 3000);
      }
    });
    return () => { sub.remove(); };
  }, [productId]);
 
  return { status, revalidate: fetchFromServer };
}