used by 'Lessons learned from handling JWT on mobile' article on Medium

token_refresh_snippet_3.swift

private func getValidUserAuthorizationInMutualExclusion(completion: @escaping (Result<AuthorizationValue, Error>) -> Void) {
    semaphore.wait()
        
    guard let authenticationInfo = authenticationInfoStore.userAuthenticationInfo else {
        semaphore.signal()
        let error = // forge an error for 'missing authorization'
        completion(.failure(error))
        return
    }
        
    if authenticationInfo.isValid {
        semaphore.signal()
        completion(.success(authenticationInfo.bearerToken))
        return
    }
        
    tokenRefreshAPI.refreshAccessToken(authenticationInfo.refreshToken) { result in
        switch result {
        case .success(let authenticationInfo):
            self.authenticationInfoStore.persistUserAuthenticationInfo(authenticationInfo)
            self.semaphore.signal()
            completion(.success(authenticationInfo.bearerToken))
                
        case .failure(let error) where error.isClientError:
            self.authenticationInfoStore.wipeUserAuthenticationInfo()
            self.semaphore.signal()
            completion(.failure(error))
                
        case .failure(let error):
            self.semaphore.signal()
            completion(.failure(error))
        }
    }
}