Updates3.swift

// MARK: Updates
public class Updates: UpdatesProtocol {
    enum StorageKeys: String {
        case postponedVersion = "UpdatesPostponedVersion"
    }
    
    private let userDefaults = UserDefaults.standard
    private let queue = DispatchQueue(label: "com.limbo.FormsUpdates", qos: .default)
    private let bundleId: String
    private let currentVersion: Version?
    private var _appStoreVersion: Version?
    
    private var postponedVersion: Version? {
        get { return Version(self.userDefaults.object(forKey: StorageKeys.postponedVersion.rawValue) as? String) }
        set { self.userDefaults.set(newValue?.description, forKey: StorageKeys.postponedVersion.rawValue) }
    }
    
    public convenience init(bundle bundleId: String,
                            version currentVersion: String) {
        self.init(
            bundle: bundleId,
            version: Version(currentVersion))
    }
    
    public init(bundle bundleId: String,
                version currentVersion: Version?) {
        self.bundleId = bundleId
        self.currentVersion = currentVersion
    }
    
    public func check(completion: @escaping ((UpdatesStatus) -> Void)) {
        self.check(cancelToken: nil, completion: completion)
    }
    
    public func check(cancelToken: CancelToken?,
                      completion: @escaping ((UpdatesStatus) -> Void)) {
        self.queue.async {
            let status: UpdatesStatus = {
                guard let appStore: Version = self.appStoreVersion() else { return .undefined }
                guard let current: Version = self.currentVersion else { return .newVersion(appStore) }
                guard appStore > current else { return .noChanges }
                guard let postponed: Version = self.postponedVersion,
                      appStore != postponed else { return .newVersion(appStore) }
                return UpdatesStatus.postponed
            }()
            guard cancelToken?.isCancelled != true else { return }
            DispatchQueue.main.async { completion(status) }
        }
    }
    
    public func reset() {
        self.postponedVersion = nil
    }
    
    public func postpone() {
        self.postponedVersion = self._appStoreVersion
    }
    
    private func appStoreVersion() -> Version? {
        let version: Version? = {
            let stringURL = String(format: "http://itunes.apple.com/lookup?bundleId=%@", self.bundleId)
            guard let url = URL(string: stringURL),
                  let data = try? Data(contentsOf: url),
                  let jsonObject = try? JSONSerialization.jsonObject(with: data, options: [.allowFragments]),
                  let json = jsonObject as? [String: Any],
                  let results = json["results"] as? [Any],
                  let result = results.first as? [String: Any],
                  let version = result["version"] as? String else { return nil }
            return Version(version)
        }()
        self._appStoreVersion = version
        return version
    }
}