swift

final class MockApiClient: Api {
    
    private static let delay = 4
    private static var requestCount = 0
    
    func fetchMovies(completion: @escaping (Bool, FilmsData?) -> Void) {
        switch MockApiClient.requestCount {
        case 0:
            DispatchQueue.main.async {
                completion(false, nil)
            }
        default:
            DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(MockApiClient.delay)) {
                let filePath = "films"
                MockApiClient.loadJsonDataFromFile(filePath, completion: { data in
                    if let json = data {
                        do {
                            let films = try JSONDecoder().decode(FilmsData.self, from: json)
                            completion(true, films)
                        }
                        catch _ as NSError {
                            fatalError("Couldn't load data from \(filePath)")
                        }
                    }
                })
            }
        }
        
        MockApiClient.requestCount += 1
    }
}