protocol ScenarioProtocol {
    // minimum number of scenario events needed to be trigerred before scenario can be executed
    static var minEventsRequired: Int? { get set }

    // maximum number of scenario events which can be trigerred before scenario stops executing
    static var maxEventsPermitted: Int? { get set }

    // maximum number of times that scenario can be executed
    static var maxExecutionsPermitted: Int? { get set }

    // minimum time interval, after the first scenario event was trigerred, before the scenario can be executed
    static var minSecondsSinceFirstEvent: TimeInterval? { get set }

    // minimum time interval, after the last scenario event was trigerred, before the scenario can be executed
    static var minSecondsSinceLastEvent: TimeInterval? { get set }

    // minimum time interval before scenario can be executed again after previous execution
    static var minSecondsBetweenExecutions: TimeInterval? { get set }

    // custom conditions closure
    static var customConditions: (() -> Bool)? { get set }
}

    // increment scenario specific event counter
    static func triggerEvent()

    // try to execute a scenario (it counts as executed only if bool param passed into a block was `true`)
    static func tryToExecute(completion: @escaping (Bool) -> Void)

    // reset scenario event and execution counters
    static func reset()

import WaitForIt

struct ShowTutorial: ScenarioProtocol {
    static func config() {
        maxExecutionsPermitted = 1
    }
}

// In ViewController.swift
func viewDidLoad() {
    super.viewDidLoad()
    ShowTutorial.tryToExecute { didExecute in
        if didExecute {
            self.showTutorial()
        }
    }
}

import WaitForIt

struct AskToSubscribe: ScenarioProtocol {
    static func config() {
        minEventsRequired = 5
        minSecondsSinceFirstEvent = 604 800 // seconds in one week
        maxExecutionsPermitted = 4
        minSecondsBetweenExecutions = 172 800 // seconds in two days
    }
}

// In AppDelegate.swift
func application(_ application: UIApplication,
  didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

    AskToSubscribe.triggerEvent()
    AskToSubscribe.tryToExecute { didExecute in
        if didExecute {
            self.askToSubscribe()
        }
    }

    return true
}

struct ShowLowBrightnessAlertOnce: ScenarioProtocol {
    static func config() {
        customConditions = {
            return UIScreen.main.brightness < 0.3
        }
        maxExecutionsPermitted = 1
    }
}