import StoreKit

@MainActor
class StoreEngine: ObservableObject {
    @Published var products: [Product] = []
    @Published var showThankYou = false
    var transactionListener: Task<Void, Never>? = nil

    init() {
        // FIX: Added [weak self] to prevent retain cycle
        transactionListener = Task.detached { [weak self] in
            for await result in Transaction.updates {
                do {
                    guard let self = self else { return }
                    let transaction = try self.checkVerified(result)
                    await transaction.finish()
                    await MainActor.run { self.showThankYou = true }
                } catch {}
            }
        }
    }

    deinit { transactionListener?.cancel() }

    func loadProducts() async {
        do {
            let p = try await Product.products(for: AppConfig.tipJarProductIDs)
            self.products = p
            #if DEBUG
            if p.isEmpty { print("⚠️ StoreEngine: No products found. Verify IAP ID in AppConfig.") }
            #endif
        } catch { print("Store Error: \(error)") }
    }

    func purchase(_ product: Product) async {
        guard let result = try? await product.purchase() else { return }
        switch result {
        case .success(let verification):
            if let transaction = try? checkVerified(verification) {
                await transaction.finish()
                self.showThankYou = true
            }
        case .pending, .userCancelled: break
        @unknown default: break
        }
    }

    nonisolated func checkVerified<T>(_ result: VerificationResult<T>) throws -> T {
        switch result {
        case .unverified: throw StoreError.failedVerification
        case .verified(let safe): return safe
        }
    }
    enum StoreError: Error { case failedVerification }
}