import 'package:flutter/material.dart';
import 'package:shadcn_ui/shadcn_ui.dart';
import 'package:provider/provider.dart';

import '../../../providers/auth_provider.dart';
import '../main/main_page.dart';
import 'register_page.dart';

class LoginPage extends StatefulWidget {
  const LoginPage({super.key});

  @override
  State<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  final formKey = GlobalKey<ShadFormState>();

  static const _maxFormWidth = 400.0;
  static const _logoSize = 64.0;
  static const _loadingIndicatorSize = 16.0;

  @override
  Widget build(BuildContext context) {
    final theme = ShadTheme.of(context);

    return Scaffold(
      body: Center(
        child: ConstrainedBox(
          constraints: const BoxConstraints(maxWidth: _maxFormWidth),
          child: Padding(
            padding: const EdgeInsets.all(24),
            child: ShadForm(
              key: formKey,
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  _buildHeader(theme),
                  const SizedBox(height: 48),
                  _buildUsernameField(),
                  const SizedBox(height: 16),
                  _buildPasswordField(),
                  const SizedBox(height: 24),
                  _buildLoginButton(),
                  const SizedBox(height: 16),
                  _buildRegisterLink(theme),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildHeader(ShadThemeData theme) {
    return Column(
      children: [
        Icon(
          LucideIcons.trendingUp,
          size: _logoSize,
          color: theme.colorScheme.primary,
        ),
        const SizedBox(height: 24),
        Text(
          '模拟所',
          style: theme.textTheme.h1,
          textAlign: TextAlign.center,
        ),
        const SizedBox(height: 8),
        Text(
          '虚拟货币模拟交易平台',
          style: theme.textTheme.muted,
          textAlign: TextAlign.center,
        ),
      ],
    );
  }

  Widget _buildUsernameField() {
    return ShadInputFormField(
      id: 'username',
      label: const Text('用户名'),
      placeholder: const Text('请输入用户名'),
      leading: const Icon(LucideIcons.user),
      validator: _validateUsername,
    );
  }

  Widget _buildPasswordField() {
    return ShadInputFormField(
      id: 'password',
      label: const Text('密码'),
      placeholder: const Text('请输入密码'),
      obscureText: true,
      leading: const Icon(LucideIcons.lock),
      validator: _validatePassword,
    );
  }

  Widget _buildLoginButton() {
    return Consumer<AuthProvider>(
      builder: (context, auth, _) {
        return ShadButton(
          onPressed: auth.isLoading ? null : () => _handleLogin(auth),
          child: auth.isLoading
              ? const SizedBox.square(
                  dimension: _loadingIndicatorSize,
                  child: CircularProgressIndicator(
                    strokeWidth: 2,
                    color: Colors.white,
                  ),
                )
              : const Text('登录'),
        );
      },
    );
  }

  Widget _buildRegisterLink(ShadThemeData theme) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text(
          '还没有账号？',
          style: theme.textTheme.muted,
        ),
        ShadButton.link(
          onPressed: _navigateToRegister,
          child: const Text('立即注册'),
        ),
      ],
    );
  }

  // Validators
  String? _validateUsername(String? value) {
    if (value == null || value.isEmpty) {
      return '请输入用户名';
    }
    if (value.length < 3) {
      return '用户名至少 3 个字符';
    }
    return null;
  }

  String? _validatePassword(String? value) {
    if (value == null || value.isEmpty) {
      return '请输入密码';
    }
    if (value.length < 6) {
      return '密码至少 6 个字符';
    }
    return null;
  }

  // Actions
  Future<void> _handleLogin(AuthProvider auth) async {
    if (!formKey.currentState!.saveAndValidate()) return;

    final values = formKey.currentState!.value;
    final response = await auth.login(
      values['username'],
      values['password'],
    );

    if (!mounted) return;

    if (response.success) {
      _navigateToMainPage();
    } else {
      _showErrorDialog(response.message ?? '用户名或密码错误');
    }
  }

  void _navigateToMainPage() {
    Navigator.of(context).pushAndRemoveUntil(
      MaterialPageRoute(builder: (_) => const MainPage()),
      (route) => false,
    );
  }

  void _navigateToRegister() {
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => const RegisterPage()),
    );
  }

  void _showErrorDialog(String message) {
    showShadDialog(
      context: context,
      builder: (context) => ShadDialog.alert(
        title: const Text('登录失败'),
        description: Text(message),
        actions: [
          ShadButton(
            child: const Text('确定'),
            onPressed: () => Navigator.of(context).pop(),
          ),
        ],
      ),
    );
  }
}