Starting point for App Store receipt validation with Vapor 3

1_AppStoreReceiptValidation.swift

import Foundation

struct AppStoreReceiptValidationRequest: Encodable {
    let receiptData: String
    let password: String?
    let excludeOldTransactions: Bool

    private enum CodingKeys: String, CodingKey {
        case receiptData = "receipt-data"
        case password
        case excludeOldTransactions = "exclude-old-transactions"
    }
}

struct AppStoreReceiptValidationResponse: Decodable {
    let status: Int
    // TODO: other fields

    enum ValidationStatus: Int {
        case success = 0
        case invalidJSON = 21000
        case invalidReceiptData = 21002
        case authenticationFailed = 21003
        case invalidSharedSecret = 21004
        case serverUnavailable = 21005
        case subscriptionExpired = 21006
        case testReceiptInProduction = 21007
        case productionReceiptInTest = 21008
        case authorizationFailed = 21010
    }
}

2_routes.swift

public func routes(_ router: Router) throws {
    router.post("ios-receipt") { request -> Future<String> in
        // Represents the body that the iOS application POSTs to the server.
        // For the sake of simplicity, it's assumed to contain a base64-encoded receipt.
        struct ReceiptRequest: Decodable {
            let receipt: String
        }

        let client = try request.make(Client.self)
        let receipt = try request.content.syncDecode(ReceiptRequest.self).receipt
        let appStoreRequest = AppStoreReceiptValidationRequest(receiptData: receipt, password: nil, excludeOldTransactions: false)

        let postReq = Request(http: HTTPRequest(method: .POST, url: "https://buy.itunes.apple.com/verifyReceipt"), using: request)
        try postReq.content.encode(appStoreRequest, as: .json)

        return client.send(postReq)
            .flatMap { try $0.content.decode(AppStoreReceiptValidationResponse.self) }
            .map { (resp: AppStoreReceiptValidationResponse) -> String in
                // TODO: check resp.status and other fields
                // TODO: if all is well, give the user what he purchased and return a successful response
                return "ok"
            }
    }
}