protocol AnimalType {
    var name: String? { get }
}

class Cat: AnimalType {
    let name: String?

    init(name: String?) {
        self.name = name
    }
}

protocol PersonType {
    var pet: AnimalType { get }
    func play() -> String
}

class PetOwner: PersonType {
    let pet: AnimalType

    init(pet: AnimalType) {
        self.pet = pet
    }

    func play() -> String {
        let name = pet.name ?? "someone"
        return "I'm playing with \(name)."
    }
}

let resolver = Resolver()
resolver.register {
    Cat(name: "tom") as AnimalType
}

let cat = try! resolver.resolve() as AnimalType
XCTAssert(cat.name == "tom")

let resolver = Resolver()
resolver.register(tag: "tom") {
    Cat(name: "tom") as AnimalType
}

resolver.register(tag: "meo") {
    Cat(name: "meo") as AnimalType
}

let tom = try! resolver.resolve(tag: "tom") as AnimalType
let meo = try! resolver.resolve(tag: "meo") as AnimalType

XCTAssert(tom.name == "tom")
XCTAssert(meo.name == "meo")

let resolver = Resolver()

resolver.register {
    Cat(name: "tom") as AnimalType
}

resolver.register { cat in
    PetOwner(pet: cat) as PersonType
}

let cat = try! resolver.resolve() as AnimalType
let owner = try! resolver.resolve(arg1: cat) as PersonType

XCTAssert(owner.pet.name == "tom")
XCTAssert(owner.play() == "I'm playing with tom.")

let cat = Cat(name: "tom") as AnimalType

let resolver = Resolver()
resolver.registerSingleton(cat)

let someCat = try! resolver.resolve() as AnimalType
XCTAssert(someCat as! Cat === cat as! Cat)