Service Level Project 
- 실제 업무 환경과 동일한 프로세스로 진행되는 개인 프로젝트
- 서비스 레벨의 API/기획 명세서와 디자인 리소스를 전달 받아서 앱 개발 진행

    func refreshIdToken(completion: @escaping (Result<String, Error>) -> Void) {
        Auth.auth().currentUser?.getIDTokenForcingRefresh(true) { idToken, error in
            if let error = error {
                completion(.failure(error))
            } else {
                guard let idToken = idToken else { return }
                UserData.idtoken = idToken
                completion(.success(idToken))
            }
        }
    }

@frozen
enum APIError: Int, Error {
    case takenUser = 201
    case invalidNickname = 202
    case invalidAuthorization = 401
    case unsubscribedUser = 406
    case serverError = 500
    case emptyParameters = 501
}

extension APIError: LocalizedError {
    var errorDescription: String? {
        switch self {
        case .takenUser:
            return "이미 가입한 유저입니다."
        case .invalidNickname:
            return "유효하지 않은 닉네임입니다."
        case .invalidAuthorization:
            return "토큰이 만료되었습니다. 다시 로그인 해주세요."
        case .unsubscribedUser:
            return "아직 가입하지 않은 유저입니다."
        case .serverError:
            return "서버 에러입니다. 잠시 후 이용해주세요."
        case .emptyParameters:
            return "request header/body를 확인해주세요."
        }
    }
}

private func checkIdToken() {
        GenericAPI.shared.requestDecodableData(type: Login.self, router: UserRouter.login) { [weak self] response in
            print("기존 - ", UserData.idtoken)
            guard let self = self else { return }
            
            switch response {
            case .success(let data):
                UserData.nickName = data.nick
                
                Helper.convertNavigationRootViewController(view: self.view, controller: TabBarViewController())
                
            case .failure(let error):
                switch error {
                case .takenUser, .invalidNickname:
                    return
                case .invalidAuthorization:
                    UserAPI.shared.refreshIdToken { result in
                        switch result {
                        case .success(let idtoken):
                            print("갱신 - ", UserData.idtoken)
                            self.refreshToken(idtoken)
                            
                        case .failure(let error):
                            print(error.localizedDescription)
                            return
                        }
                    }
                case .unsubscribedUser:
                    Helper.convertNavigationRootViewController(view: self.view, controller: NicknameViewController())
                case .serverError:
                    self.showToast(message: "서버 내부 오류입니다. 잠시 후 재인증 해주세요.")
                case .emptyParameters:
                    self.showToast(message: "Client Error")
                }
                
            }
        }
    }

enum MDSFloatingButtonType {
    case plain
    case matching
    case matched
    
    var image: UIImage {
        switch self {
        case .plain:
            return Constant.Image.search
        case .matching:
            return Constant.Image.antenna
        case .matched:
            return Constant.Image.message
        }
    }
}

            floatingButton.rx.tap
            .withUnretained(self)
            .bind { vc, _ in
                if vc.floatingButton.type == .plain {
                    let viewController = StudyViewController()
                    viewController.viewModel.mapLatitude.accept(vc.mapLatitude)
                    viewController.viewModel.mapLongitude.accept(vc.mapLongitude)
                    vc.navigationController?.pushViewController(viewController, animated: true)
                } else if vc.floatingButton.type == .matching {
                    // 매칭중
                    let studyViewController = StudyViewController()
                    let searchViewController = SearchSesacViewController()
                    searchViewController.mapLatitude = vc.mapLatitude
                    searchViewController.mapLongitude = vc.mapLongitude
                    searchViewController.stateType = .matching
                    vc.navigationController?.pushViewControllers([studyViewController, searchViewController], animated: false)
                } else {
                    // 매칭된 > 채팅화면으로 이동
                    let viewController = ChatViewController()
                    vc.navigationController?.pushViewController(viewController, animated: true)
                }
            }
            .disposed(by: disposeBag)

extension UINavigationController {
    func pushViewControllers(_ inViewControllers: [UIViewController], animated: Bool) {
        var stack = self.viewControllers
        stack.append(contentsOf: inViewControllers)
        self.setViewControllers(stack, animated: animated)
    }
}

@frozen
enum CardViewType {
    case plain
    case info
}