iOS または macOS アプリケーションにログイン機能を追加する

import Foundation
import Auth0
import Combine

@MainActor
class AuthenticationService: ObservableObject {
    @Published var isAuthenticated = false
    @Published var user: User?
    @Published var isLoading = false
    @Published var errorMessage: String?
    
    private let credentialsManager = CredentialsManager(authentication: Auth0.authentication())
    
    init() {
        Task {
            await checkAuthenticationStatus()
        }
    }
    
    private func checkAuthenticationStatus() async {
        isLoading = true
        defer { isLoading = false }
        
        guard let credentials = try? await credentialsManager.credentials() else {
            isAuthenticated = false
            return
        }
        
        isAuthenticated = true
        // IDトークンからユーザー情報を取得
        user = credentials.user
    }
    
    func login() async {
        isLoading = true
        errorMessage = nil
        defer { isLoading = false }
        
        do {
            let credentials = try await Auth0
                .webAuth()
                .scope("openid profile email offline_access")
                .start()
            
            _ = credentialsManager.store(credentials: credentials)
            isAuthenticated = true
            // IDトークンからユーザー情報を取得
            user = credentials.user
        } catch {
            errorMessage = "ログインに失敗しました: \(error.localizedDescription)"
        }
    }
    
    func logout() async {
        isLoading = true
        defer { isLoading = false }
        
        do {
            try await Auth0.webAuth().clearSession()
            _ = credentialsManager.clear()
            isAuthenticated = false
            user = nil
        } catch {
            errorMessage = "ログアウトに失敗しました: \(error.localizedDescription)"
        }
    }
}