func attempt<T>(_ behavior: RepeatBehavior, _ body: @escaping () -> Promise<T>) -> Promise<T> {
    var attempts: UInt = 0
    func attempt() -> Promise<T> {
        attempts += 1
        return body().recover({ error -> Promise<T> in
            let (maxCount, delay) = behavior.calculateConditions(attempts)
            guard attempts < maxCount else { throw error }
            return after(delay).then(on: nil, attempt)
        })
    }
    return attempt()
}

let behavior = RepeatBehavior.exponentialDelayed(maxCount: 5, initial: 1, multiplier: 0.5)
attempt(behavior) {
  flakeyTask(parameters: foo)
}.then {
    //…
}.catch { _ in
    // we attempted three times but still failed
}