@discardableResult
private class func request<T: JSONCodable>(urlRequest: URLRequest, router: Router?, completion: @escaping RequestCompletion<T>) -> URLSessionDataTask? {
    let dataTask = URLSession.shared.dataTask(with: urlRequest) { data, response, error in
        DispatchQueue.global(qos: .background).async {
            self.handleResponse(data: data, response: response, error: error, router: router, completion: completion)
        }
    }

    dataTask.resume()

    return dataTask
}

private class func handleResponse<T: JSONCodable>(data: Data?, response: URLResponse?, error: Error?, router: Router?, completion: @escaping RequestCompletion<T>) {
    var responseObject: T?

    do {
        responseObject = try T(json: json)
    } catch {
        handleResult(result: .failure(error), response: nil, completion: completion)
        return
    }

    if let responseObject = responseObject {
        handleResult(result: .success(responseObject), response: response, completion: completion)
    } else {
        handleResult(result: .failure(NetworkResponse.unableToDecode), response: response, completion: completion)
    }
}

private class func handleResult<T: JSONCodable>(result: Result<T, Error>, response: HTTPURLResponse?, completion: @escaping RequestCompletion<T>) {
    DispatchQueue.main.async {
        switch result {
        case .success(let result):
            completion(.success(result), response)
        case .failure(let error):
            completion(.failure(error), response)
        }
    }
}