sidmani

/// custom unique identifier
/// @see https://www.firebase.com/blog/2015-02-11-firebase-unique-identifiers.html
private let ASC_CHARS = Array("-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz")
private let DESC_CHARS = ASC_CHARS.reverse()
private var lastPushTime: UInt64 = 0
private var lastRandChars = Array<Int>(count: 12, repeatedValue: 0)

func generatePushID(ascending: Bool = true) -> String {
  let PUSH_CHARS = ascending ? ASC_CHARS: DESC_CHARS
  var timeStampChars = Array<Character>(count: 8, repeatedValue: PUSH_CHARS.first!)