public static func syncExpiration(local: Date?, completion: @escaping (_ object: PFObject?) -> ()) {
  // Query Parse for expiration date.
    
  guard let user = PFUser.current(),
    let userID = user.objectId,
    user.isAuthenticated else {
      return
  }
    
  let query = PFQuery(className: "_User")
  query.getObjectInBackground(withId: userID) {
    object, error in
      
    // TODO: Find latest subscription date.

    completion(object)
  }
}

let parseExpiration = object?[expirationDateKey] as? Date
      
// Get to latest date between Parse and local.
var latestDate: Date?
if parseExpiration == nil {
  latestDate = local
} else if local == nil {
  latestDate = parseExpiration
} else if parseExpiration!.compare(local!) == .orderedDescending {
  latestDate = parseExpiration
} else {
  latestDate = local
}
      
if let latestDate = latestDate {
  // Update local
  UserSettings.shared.expirationDate = latestDate
        
  // See if subscription valid
  if latestDate.compare(Date()) == .orderedDescending {
    setRandomProduct(with: true)
  }
}

private static func handleMonthlySubscription(months: Int) {
  // Update local and Parse with new subscription.
    
  syncExpiration(local: UserSettings.shared.expirationDate) {
    object in
      
    // Increase local
    UserSettings.shared.increaseRandomExpirationDate(by: months)
    setRandomProduct(with: true)
      
    // Update Parse with extended purchase
    object?[expirationDateKey] = UserSettings.shared.expirationDate
    object?.saveInBackground()
      
    NotificationCenter.default.post(name: NSNotification.Name(rawValue: PurchaseNotification),
                                    object: nil)
  }    
}