import SwiftUI
import DesignSystem

public struct AuthScreen: View {
    private let viewModel: AuthViewModel
    private let onLoggedIn: () -> Void

    @State private var phone = ""
    @State private var code = ""
    @State private var privacyAgreed = false

    @Environment(\.dismiss) private var dismiss

    public init(viewModel: AuthViewModel, onLoggedIn: @escaping () -> Void) {
        self.viewModel = viewModel
        self.onLoggedIn = onLoggedIn
    }

    public var body: some View {
        NavigationStack {
            ScrollView {
                VStack(alignment: .leading, spacing: DS.Spacing.md) {
                    Text("手机号登录")
                        .font(.title2.bold())
                        .foregroundStyle(DS.Color.brandDark)
                    Text("手机号仅用于账号绑定，不会公开展示")
                        .font(.footnote)
                        .foregroundStyle(DS.Color.faintText)

                    TextField("手机号", text: Binding(get: { phone }, set: { phone = digits($0, max: 11) }))
                        .textFieldStyle(.roundedBorder)

                    HStack(spacing: DS.Spacing.sm) {
                        TextField("验证码", text: Binding(get: { code }, set: { code = digits($0, max: 6) }))
                            .textFieldStyle(.roundedBorder)
                        Button(getCodeTitle) { viewModel.requestSmsCode(phone: phone) }
                            .buttonStyle(.bordered)
                            .disabled(!canSendCode)
                    }

                    Button { privacyAgreed.toggle() } label: {
                        HStack(spacing: DS.Spacing.xs) {
                            Image(systemName: privacyAgreed ? "checkmark.square.fill" : "square")
                                .foregroundStyle(privacyAgreed ? DS.Color.brandGold : DS.Color.brandMuted)
                            Text("我已阅读并同意《用户协议》和《隐私政策》")
                                .font(.caption)
                                .foregroundStyle(DS.Color.faintText)
                        }
                    }
                    .buttonStyle(.plain)

                    if let errorMessage = viewModel.errorMessage {
                        Text(errorMessage)
                            .font(.footnote)
                            .foregroundStyle(DS.Color.danger)
                    }

                    Button(viewModel.isSubmitting ? "登录中..." : "登录") {
                        viewModel.login(phone: phone, code: code)
                    }
                    .buttonStyle(.borderedProminent)
                    .frame(maxWidth: .infinity)
                    .disabled(!canSubmit)
                }
                .padding(DS.Spacing.lg)
            }
            .navigationTitle("登录")
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("取消") { dismiss() }
                }
            }
        }
        .onChange(of: viewModel.didLogin) { _, loggedIn in
            if loggedIn { onLoggedIn() }
        }
    }

    private var phoneValid: Bool {
        phone.range(of: #"^1\d{10}$"#, options: .regularExpression) != nil
    }

    private var canSendCode: Bool {
        phoneValid && viewModel.countdownSeconds == 0 && !viewModel.isSendingCode
    }

    private var canSubmit: Bool {
        phoneValid && !code.isEmpty && privacyAgreed && !viewModel.isSubmitting
    }

    private var getCodeTitle: String {
        if viewModel.countdownSeconds > 0 { return "\(viewModel.countdownSeconds)s 后重发" }
        if viewModel.isSendingCode { return "发送中" }
        return "获取验证码"
    }

    private func digits(_ string: String, max: Int) -> String {
        String(string.filter(\.isNumber).prefix(max))
    }
}