import SwiftUI

// MARK: - Login ViewModel

@MainActor
class LoginViewModel: ObservableObject {
    // MARK: - Published Properties
    @Published var showIDLogin: Bool = false
    @Published var showEmailLogin: Bool = false
    @Published var showLanguageSettings: Bool = false
    @Published var showUserAgreement: Bool = false
    @Published var showPrivacyPolicy: Bool = false
    @Published var isAgreementAccepted: Bool = true // 默认选中
    @Published var showAgreementAlert: Bool = false
    @Published var isAnyLoginCompleted: Bool = false
    
    // MARK: - Callbacks
    var onLoginSuccess: (() -> Void)?
    
    // MARK: - Public Methods
    func onIDLoginTapped() {
        if isAgreementAccepted {
            showIDLogin = true
        } else {
            showAgreementAlert = true
        }
    }
    
    func onEmailLoginTapped() {
        if isAgreementAccepted {
            showEmailLogin = true
        } else {
            showAgreementAlert = true
        }
    }
    
    func onLanguageSettingsTapped() {
        showLanguageSettings = true
    }
    
    func onUserAgreementTapped() {
        showUserAgreement = true
    }
    
    func onPrivacyPolicyTapped() {
        showPrivacyPolicy = true
    }
    
    func onLoginCompleted() {
        isAnyLoginCompleted = true
        onLoginSuccess?()
    }
    
    func onBackFromIDLogin() {
        showIDLogin = false
        if isAnyLoginCompleted {
            onLoginSuccess?()
        }
    }
    
    func onBackFromEmailLogin() {
        showEmailLogin = false
        if isAnyLoginCompleted {
            onLoginSuccess?()
        }
    }
}

// MARK: - Login View

struct LoginPage: View {
    @StateObject private var viewModel = LoginViewModel()
    let onLoginSuccess: () -> Void
    
    var body: some View {
        NavigationStack {
            GeometryReader { geometry in
                ZStack {
                    backgroundView
                    
                    VStack(spacing: 0) {
                        Image("top")
                            .resizable()
                            .aspectRatio(375/400, contentMode: .fit)
                            .frame(maxWidth: .infinity)

                        HStack {
                            Text(LocalizedString("login.app_title", comment: ""))
                                .font(FontManager.adaptedFont(.bayonRegular, designSize: 56, for: geometry.size.width))
                                .foregroundColor(.white)
                                .padding(.leading, 20)
                            Spacer()
                        }
                        .padding(.bottom, 20) // 距离 top 图片底部的间距
                        
                        Spacer()
                        
                        bottomSection
                    }
                    
                    // 语言设置按钮 - 固定在页面右上角
                    languageSettingsButton
                        .position(x: geometry.size.width - 40, y: 60)
                    
                    APILoadingEffectView()
                }
            }
            .ignoresSafeArea()
            .navigationBarHidden(true)
            .navigationDestination(isPresented: $viewModel.showIDLogin) {
                IDLoginPage(
                    onBack: {
                        viewModel.onBackFromIDLogin()
                    },
                    onLoginSuccess: {
                        viewModel.onLoginCompleted()
                    }
                )
                .navigationBarHidden(true)
            }
            .navigationDestination(isPresented: $viewModel.showEmailLogin) {
                EMailLoginPage(
                    onBack: {
                        viewModel.onBackFromEmailLogin()
                    },
                    onLoginSuccess: {
                        viewModel.onLoginCompleted()
                    }
                )
                .navigationBarHidden(true)
            }
            .sheet(isPresented: $viewModel.showLanguageSettings) {
                LanguageSettingsView(isPresented: $viewModel.showLanguageSettings)
            }
            .webView(
                isPresented: $viewModel.showUserAgreement,
                url: APIConfiguration.webURL(for: .userAgreement)
            )
            .webView(
                isPresented: $viewModel.showPrivacyPolicy,
                url: APIConfiguration.webURL(for: .privacyPolicy)
            )
            .alert(LocalizedString("login.agreement_alert_title", comment: ""), isPresented: $viewModel.showAgreementAlert) {
                Button(LocalizedString("login.agreement_alert_confirm", comment: "")) { }
            } message: {
                Text(LocalizedString("login.agreement_alert_message", comment: ""))
            }
        }
        .onAppear {
            viewModel.onLoginSuccess = onLoginSuccess
        }
    }
    
    // MARK: - 子视图
    
    private var backgroundView: some View {
        LoginBackgroundView()
    }
    
    private var bottomSection: some View {
        VStack(spacing: 20) {
            loginButtons
            userAgreementComponent
        }
        .padding(.horizontal, 28)
        .padding(.bottom, 48)
    }
    
    private var loginButtons: some View {
        VStack(spacing: 20) {
            LoginButton(
                iconName: "person.circle",
                iconColor: .blue,
                title: LocalizedString("login.id_login", comment: ""),
                action: {
                    viewModel.onIDLoginTapped()
                }
            )
            
            LoginButton(
                iconName: "envelope",
                iconColor: .green,
                title: LocalizedString("login.email_login", comment: ""),
                action: {
                    viewModel.onEmailLoginTapped()
                }
            )
        }
    }
    
    private var languageSettingsButton: some View {
        Button(action: {
            viewModel.onLanguageSettingsTapped()
        }) {
            Image(systemName: "globe")
                .font(.system(size: 20))
                .foregroundColor(.white.opacity(0.8))
        }
    }
    
    private var userAgreementComponent: some View {
        UserAgreementComponent(
            isAgreed: $viewModel.isAgreementAccepted,
            onAgreementTap: {
                Task { @MainActor in
                    viewModel.onUserAgreementTapped()
                }
            },
            onPolicyTap: {
                Task { @MainActor in
                    viewModel.onPrivacyPolicyTapped()
                }
            }
        )
        .frame(height: 40)
        .padding(.horizontal, -20)
    }
}

#Preview {
    LoginPage(onLoginSuccess: {})
}