KitchenUseCase.swift

// Module: Domain

struct KitchenUseCase {
    
    // Obtains stuff already stored in some place inside the restaurant
    // For example: fetching it from CoreData, KeychainManager, UserDefaults and so on.
    private let localDataSource: KitchenLocalRepository
    
    // Obtains stuff needed from outside of our restaurant.
    // For example: doing API calls to a NetworkManager.
    private let remoteDataSource: KitchenRemoteRepository
    
    // Our entity that knows how to cook a dish. It's a protocol, so each cooker can have
    // his own way to prepare the food. However, they must
    // always follow our specifications defined in here to deliver the dish
    private let cooker: CookerProtocol
    
    public init(localDataSource: KitchenLocalDataSource, remoteDataSource: KitchenRemoteDataSource, cooker: CookerProtocol) {
        self.localDataSource = localDataSource
        self.remoteDataSource = remoteDataSource
        self.cooker = cooker
    }
    
    // Defines what our Kitchen should do to cook every dish we have in menu, but don't specify HOW
    // the Kitchen will do that. That task will be delegate to ours Cookers
    public func prepareRecipe(_ recipe: Recipe) {
        
        switch recipe {
        case recipe is SpaghettiCarbonara:
            cookSpaghettiCarbonara()
        default:
            break
        }
    }
    
    // The set of instructions we provide to our kitchen so can delivery our Carbonara dish.
    private func cookSpaghettiCarbonara() {
        
        func cook(using ingredients: [Ingredient]) {
            let carbonara = SpaghettiCarbonara(ingredients: storedCarbonaraIngredients)
            cooker.cook(carbonara)   
        }
        
        if let storedCarbonaraIngredients = localDataSource.getIngredients(for: SpaghettiCarbonara.self) {
            cook(using: storedCarbonaraIngredients)
        } else {
            remoteDataSource.getIngredients(for: SpaghettiCarbonara.self) { carbonaraIngredients in
                cook(using: carbonaraIngredients)
            }
        }
    }
}