First launch

//: Playground - noun: a place where people can play

import UIKit


protocol BoolUserDefaults {
    func bool(forKey defaultName: String) -> Bool
    func set(_ value: Any?, forKey defaultName: String)
}

extension UserDefaults: BoolUserDefaults {}

final class FirstLaunch {
    let wasLaunchedBefore: Bool
    var isFirstLaunch: Bool {
        return !wasLaunchedBefore
    }

    init(userDefaults: BoolUserDefaults = UserDefaults.standard) {
        let key = "com.any-suggestion.FirstLaunch.WasLaunchedBefore"
        let wasLaunchedBefore = userDefaults.bool(forKey: key)
        self.wasLaunchedBefore = wasLaunchedBefore
        if !wasLaunchedBefore {
            userDefaults.set(true, forKey: key)
        }
    }
}

FirstLaunch().isFirstLaunch
FirstLaunch().isFirstLaunch


//TESTS

class MockUserDefaults: BoolUserDefaults {
    var defaults = [String: Bool]()
    var mockedValue: Bool?
    func bool(forKey defaultName: String) -> Bool {
        return mockedValue ?? defaults[defaultName] ?? false
    }
    func set(_ value: Any?, forKey defaultName: String) {
        guard let value = value else {
            defaults[defaultName] = nil
            return
        }
        guard let boolValue = value as? Bool else {
            fatalError("should it be bool?")
        }
        defaults[defaultName] = boolValue
    }
}



let mockedDefaults = MockUserDefaults()
assert(FirstLaunch(userDefaults: mockedDefaults).isFirstLaunch)
assert(!FirstLaunch(userDefaults: mockedDefaults).isFirstLaunch)