StoreKit 2面接対策:サブスクリプション管理とレシート検証

import StoreKit

actor ProductService {

    // App Store Connectで設定された製品識別子
    private let productIdentifiers: Set<String> = [
        "com.app.subscription.monthly",
        "com.app.subscription.yearly",
        "com.app.premium.lifetime"
    ]

    // 繰り返しのネットワーク呼び出しを避けるための製品キャッシュ
    private var cachedProducts: [Product] = []

    func loadProducts() async throws -> [Product] {
        // キャッシュが利用可能な場合は返す
        guard cachedProducts.isEmpty else {
            return cachedProducts
        }

        // App Storeへの非同期リクエスト
        let products = try await Product.products(for: productIdentifiers)
        cachedProducts = products
        return products
    }

    func product(for identifier: String) async throws -> Product? {
        let products = try await loadProducts()
        return products.first { $0.id == identifier }
    }
}

import StoreKit

extension Product.ProductType {

    var displayName: String {
        switch self {
        case .consumable:
            // 消耗型製品(クレジット、ライフなど)
            return "Consumable"
        case .nonConsumable:
            // 永続的な購入(機能のアンロック)
            return "Non-Consumable"
        case .autoRenewable:
            // 自動更新サブスクリプション
            return "Auto-Renewable Subscription"
        case .nonRenewable:
            // 更新なしのサブスクリプション(一時的なパス)
            return "Non-Renewable Subscription"
        @unknown default:
            return "Unknown"
        }
    }
}

import StoreKit
import UIKit

actor PurchaseManager {

    enum PurchaseError: Error {
        case productNotFound
        case purchaseCancelled
        case purchasePending
        case verificationFailed
        case unknown
    }

    func purchase(_ product: Product, in scene: UIWindowScene) async throws -> Transaction {
        // UIコンテキスト付きで購入を開始(iOS 18.2以降)
        let result = try await product.purchase(confirmIn: scene)

        switch result {
        case .success(let verification):
            // トランザクション署名の検証
            let transaction = try checkVerification(verification)

            // トランザクションを完了としてマーク
            await transaction.finish()

            return transaction

        case .userCancelled:
            // ユーザーが購入モーダルをキャンセル
            throw PurchaseError.purchaseCancelled

        case .pending:
            // 保留中の購入(保護者の承認など)
            throw PurchaseError.purchasePending

        @unknown default:
            throw PurchaseError.unknown
        }
    }

    private func checkVerification<T>(_ result: VerificationResult<T>) throws -> T {
        switch result {
        case .verified(let safe):
            // App Storeによって署名・検証されたトランザクション
            return safe
        case .unverified(_, let error):
            // 無効または破損した署名
            throw PurchaseError.verificationFailed
        }
    }
}

import StoreKit

actor TransactionObserver {

    private var updateTask: Task<Void, Never>?

    func startObserving() {
        // 以前の監視をキャンセル
        updateTask?.cancel()

        updateTask = Task(priority: .background) {
            // トランザクション更新の無限ストリーム
            for await result in Transaction.updates {
                do {
                    let transaction = try self.checkVerification(result)

                    // タイプに応じてトランザクションを処理
                    await self.handleTransaction(transaction)

                    // 常にトランザクションを完了
                    await transaction.finish()
                } catch {
                    // デバッグのためにエラーをログ記録
                    print("Transaction verification failed: (error)")
                }
            }
        }
    }

    func stopObserving() {
        updateTask?.cancel()
        updateTask = nil
    }

    private func handleTransaction(_ transaction: Transaction) async {
        switch transaction.productType {
        case .autoRenewable:
            // サブスクリプションステータスを更新
            await updateSubscriptionStatus(transaction)
        case .nonConsumable:
            // プレミアム機能をアンロック
            await unlockFeature(transaction.productID)
        default:
            break
        }
    }

    private func checkVerification<T>(_ result: VerificationResult<T>) throws -> T {
        switch result {
        case .verified(let safe):
            return safe
        case .unverified:
            throw PurchaseError.verificationFailed
        }
    }

    private func updateSubscriptionStatus(_ transaction: Transaction) async {
        // ステータス更新の実装
    }

    private func unlockFeature(_ productID: String) async {
        // 機能アンロックの実装
    }

    enum PurchaseError: Error {
        case verificationFailed
    }
}

import StoreKit

struct SubscriptionStatusChecker {

    struct SubscriptionStatus {
        let isActive: Bool
        let expirationDate: Date?
        let willRenew: Bool
        let productID: String?
        let appTransactionID: UInt64?  // iOS 18.4以降
    }

    static func checkCurrentStatus(for productID: String) async -> SubscriptionStatus {
        // 新しいcurrentEntitlements(for:) APIを使用(iOS 18.4以降)
        var latestTransaction: Transaction?

        for await result in Transaction.currentEntitlements(for: productID) {
            if case .verified(let transaction) = result {
                if transaction.productType == .autoRenewable {
                    if latestTransaction == nil ||
                       transaction.purchaseDate > latestTransaction!.purchaseDate {
                        latestTransaction = transaction
                    }
                }
            }
        }

        guard let transaction = latestTransaction else {
            return SubscriptionStatus(
                isActive: false,
                expirationDate: nil,
                willRenew: false,
                productID: nil,
                appTransactionID: nil
            )
        }

        // サブスクリプションがまだアクティブかチェック
        let isActive = transaction.expirationDate ?? Date.distantPast > Date()

        // 更新情報を取得
        let renewalInfo = await getRenewalInfo(for: transaction.productID)

        return SubscriptionStatus(
            isActive: isActive,
            expirationDate: transaction.expirationDate,
            willRenew: renewalInfo?.willAutoRenew ?? false,
            productID: transaction.productID,
            appTransactionID: transaction.appTransactionID
        )
    }

    private static func getRenewalInfo(for productID: String) async -> Product.SubscriptionInfo.RenewalInfo? {
        guard let product = try? await Product.products(for: [productID]).first,
              let subscription = product.subscription else {
            return nil
        }

        // 更新ステータスを取得
        let status = try? await subscription.status.first
        return status?.renewalInfo
    }
}

import StoreKit

struct OfferManager {

    enum OfferType {
        case freeTrial(duration: String)
        case payAsYouGo(periods: Int, price: Decimal)
        case payUpFront(duration: String, price: Decimal)
        case oneTime(price: Decimal)  // iOS 17.2以降:すべての製品タイプのオファーコード
        case none
    }

    static func getIntroductoryOffer(for product: Product) -> OfferType {
        guard let subscription = product.subscription,
              let offer = subscription.introductoryOffer else {
            return .none
        }

        switch offer.paymentMode {
        case .freeTrial:
            // 無料トライアル期間
            return .freeTrial(duration: formatPeriod(offer.period))

        case .payAsYouGo:
            // 複数期間にわたる割引価格
            return .payAsYouGo(
                periods: offer.periodCount,
                price: offer.price
            )

        case .payUpFront:
            // 期間に対する一括支払い
            return .payUpFront(
                duration: formatPeriod(offer.period),
                price: offer.price
            )

        case .oneTime:
            // 一回限りのオファーコード(消耗型、非消耗型、非更新型)
            return .oneTime(price: offer.price)

        @unknown default:
            return .none
        }
    }

    static func checkEligibility(for product: Product) async -> Bool {
        // ユーザーがオファーを利用できるかチェック
        guard let subscription = product.subscription else {
            return false
        }

        // isEligibleForIntroOfferは新規サブスクライバーかを示す
        return await subscription.isEligibleForIntroOffer
    }

    private static func formatPeriod(_ period: Product.SubscriptionPeriod) -> String {
        let value = period.value
        switch period.unit {
        case .day:
            return "(value) day(value > 1 ? "s" : "")"
        case .week:
            return "(value) week(value > 1 ? "s" : "")"
        case .month:
            return "(value) month(value > 1 ? "s" : "")"
        case .year:
            return "(value) year(value > 1 ? "s" : "")"
        @unknown default:
            return ""
        }
    }
}

import StoreKit

actor RestoreManager {

    struct RestoreResult {
        let restoredProducts: [String]
        let activeSubscriptions: [String]
    }

    func restorePurchases() async throws -> RestoreResult {
        var restoredProducts: [String] = []
        var activeSubscriptions: [String] = []

        // App Storeと同期
        try await AppStore.sync()

        // すべてのユーザートランザクションを反復
        for await result in Transaction.currentEntitlements {
            guard case .verified(let transaction) = result else {
                continue
            }

            switch transaction.productType {
            case .nonConsumable:
                // 永続的な購入を復元
                restoredProducts.append(transaction.productID)

            case .autoRenewable:
                // サブスクリプションがアクティブかチェック
                if let expiration = transaction.expirationDate,
                   expiration > Date() {
                    activeSubscriptions.append(transaction.productID)
                }

            default:
                // 消耗型は復元不可
                break
            }
        }

        return RestoreResult(
            restoredProducts: restoredProducts,
            activeSubscriptions: activeSubscriptions
        )
    }
}

import SwiftUI
import StoreKit

struct SubscriptionSettingsView: View {
    let subscriptionGroupID = "com.app.subscription.group"
    
    var body: some View {
        VStack(spacing: 16) {
            // 現在の購読者にアップグレードオプションを表示
            SubscriptionOfferView(groupID: subscriptionGroupID)
                .visibleRelationship(.upgrade)
                .prefersPromotionalIcon(true)
                .subscriptionOfferViewDetailAction { path in
                    path.append("subscriptionDetail")
                }
            
            // 現在のプラン詳細を表示
            SubscriptionOfferView(groupID: subscriptionGroupID)
                .visibleRelationship(.current)
        }
        .padding()
    }
}

import StoreKit

struct TransactionPayload: Codable {
    let transactionID: String
    let originalTransactionID: String
    let productID: String
    let purchaseDate: Date
    let expirationDate: Date?
    let jwsRepresentation: String
    let appTransactionID: String?  // iOS 18.4以降
}

actor ServerValidationService {

    private let apiEndpoint = "https://api.example.com/verify"

    func validateWithServer(_ transaction: Transaction) async throws -> Bool {
        // サーバー用のペイロードを作成
        let payload = TransactionPayload(
            transactionID: String(transaction.id),
            originalTransactionID: String(transaction.originalID),
            productID: transaction.productID,
            purchaseDate: transaction.purchaseDate,
            expirationDate: transaction.expirationDate,
            jwsRepresentation: transaction.jwsRepresentation ?? "",
            appTransactionID: transaction.appTransactionID.map { String($0) }
        )

        // JSONにエンコード
        let encoder = JSONEncoder()
        encoder.dateEncodingStrategy = .iso8601
        let jsonData = try encoder.encode(payload)

        // サーバーへ送信
        var request = URLRequest(url: URL(string: apiEndpoint)!)
        request.httpMethod = "POST"
        request.httpBody = jsonData
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")

        let (data, response) = try await URLSession.shared.data(for: request)

        guard let httpResponse = response as? HTTPURLResponse,
              httpResponse.statusCode == 200 else {
            return false
        }

        // サーバー応答をデコード
        let validationResponse = try JSONDecoder().decode(
            ValidationResponse.self,
            from: data
        )

        return validationResponse.isValid
    }
}

struct ValidationResponse: Codable {
    let isValid: Bool
    let subscriptionStatus: String?
}

enum NotificationType: String, Codable {
    case subscribed = "SUBSCRIBED"
    case didRenew = "DID_RENEW"
    case didFailToRenew = "DID_FAIL_TO_RENEW"
    case didChangeRenewalStatus = "DID_CHANGE_RENEWAL_STATUS"
    case expired = "EXPIRED"
    case gracePeriodExpired = "GRACE_PERIOD_EXPIRED"
    case offerRedeemed = "OFFER_REDEEMED"
    case priceIncrease = "PRICE_INCREASE"
    case refund = "REFUND"
    case renewalExtended = "RENEWAL_EXTENDED"
    case revoke = "REVOKE"
}

struct ServerNotification: Codable {
    let notificationType: NotificationType
    let subtype: String?
    let data: NotificationData

    struct NotificationData: Codable {
        let bundleId: String
        let environment: String
        let signedTransactionInfo: String
        let signedRenewalInfo: String?
    }
}

import StoreKit

struct PurchaseErrorHandler {

    enum UserFacingError {
        case networkError
        case paymentFailed
        case notAuthorized
        case productNotAvailable
        case unknown

        var message: String {
            switch self {
            case .networkError:
                return "Connection failed. Please check your internet connection."
            case .paymentFailed:
                return "Payment failed. Please verify your payment information."
            case .notAuthorized:
                return "In-app purchases are disabled on this device."
            case .productNotAvailable:
                return "This product is not currently available."
            case .unknown:
                return "An unexpected error occurred."
            }
        }
    }

    static func handle(_ error: Error) -> UserFacingError {
        // StoreKitエラーかチェック
        if let storeKitError = error as? StoreKitError {
            switch storeKitError {
            case .networkError:
                return .networkError
            case .userCancelled:
                // エラーを表示しない、ユーザーがキャンセル
                return .unknown
            case .notAvailableInStorefront:
                return .productNotAvailable
            case .notEntitled:
                return .notAuthorized
            default:
                return .unknown
            }
        }

        // 購入エラー
        if let purchaseError = error as? Product.PurchaseError {
            switch purchaseError {
            case .invalidQuantity:
                return .unknown
            case .productUnavailable:
                return .productNotAvailable
            case .purchaseNotAllowed:
                return .notAuthorized
            default:
                return .unknown
            }
        }

        return .unknown
    }
}

import StoreKit

actor OfflineCapabilityManager {

    private let userDefaults = UserDefaults.standard
    private let entitlementsKey = "cached_entitlements"

    func cacheCurrentEntitlements() async {
        var entitlements: [String: Date] = [:]

        for await result in Transaction.currentEntitlements {
            if case .verified(let transaction) = result {
                entitlements[transaction.productID] = transaction.expirationDate
            }
        }

        // ローカルに保存
        if let data = try? JSONEncoder().encode(entitlements) {
            userDefaults.set(data, forKey: entitlementsKey)
        }
    }

    func getCachedEntitlements() -> [String: Date] {
        guard let data = userDefaults.data(forKey: entitlementsKey),
              let entitlements = try? JSONDecoder().decode(
                  [String: Date].self,
                  from: data
              ) else {
            return [:]
        }

        // 期限切れのエンタイトルメントをフィルタ
        let now = Date()
        return entitlements.filter { _, expiration in
            expiration > now
        }
    }

    func hasValidEntitlement(for productID: String) -> Bool {
        let cached = getCachedEntitlements()
        return cached[productID] != nil
    }
}

import StoreKit
import Combine

@MainActor
final class SubscriptionService: ObservableObject {

    static let shared = SubscriptionService()

    @Published private(set) var products: [Product] = []
    @Published private(set) var purchasedProductIDs: Set<String> = []
    @Published private(set) var subscriptionStatus: SubscriptionStatus = .none

    private var transactionObserver: Task<Void, Never>?

    enum SubscriptionStatus {
        case none
        case active(expirationDate: Date)
        case expired
        case inGracePeriod
    }

    private init() {
        // トランザクション監視を開始
        startTransactionObserver()

        // 初期状態をロード
        Task {
            await loadProducts()
            await updateSubscriptionStatus()
        }
    }

    private func startTransactionObserver() {
        transactionObserver = Task.detached(priority: .background) {
            for await result in Transaction.updates {
                if case .verified(let transaction) = result {
                    await transaction.finish()
                    await self.updateSubscriptionStatus()
                }
            }
        }
    }

    func loadProducts() async {
        do {
            let productIDs = [
                "com.app.subscription.monthly",
                "com.app.subscription.yearly"
            ]
            products = try await Product.products(for: productIDs)
        } catch {
            print("Failed to load products: (error)")
        }
    }

    func purchase(_ product: Product) async throws {
        let result = try await product.purchase()

        switch result {
        case .success(let verification):
            if case .verified(let transaction) = verification {
                await transaction.finish()
                await updateSubscriptionStatus()
            }
        case .userCancelled:
            break
        case .pending:
            break
        @unknown default:
            break
        }
    }

    func updateSubscriptionStatus() async {
        var purchasedIDs: Set<String> = []
        var latestSubscription: Transaction?

        for await result in Transaction.currentEntitlements {
            if case .verified(let transaction) = result {
                purchasedIDs.insert(transaction.productID)

                if transaction.productType == .autoRenewable {
                    if latestSubscription == nil ||
                       transaction.purchaseDate > latestSubscription!.purchaseDate {
                        latestSubscription = transaction
                    }
                }
            }
        }

        purchasedProductIDs = purchasedIDs

        if let subscription = latestSubscription,
           let expiration = subscription.expirationDate {
            if expiration > Date() {
                subscriptionStatus = .active(expirationDate: expiration)
            } else {
                subscriptionStatus = .expired
            }
        } else {
            subscriptionStatus = .none
        }
    }

    deinit {
        transactionObserver?.cancel()
    }
}