import 'package:flutter/cupertino.dart';

import '../api/api_client.dart';

/// 独立登录页，对应 Android 端 `activity/login/LoginActivity`。
///
/// 行为与 Android 端保持一致：
/// - 用户名 / 密码双输入，均非空才允许提交；
/// - 支持注册（`POST /api/auth/register`），注册成功后停留在登录页提示登录；
/// - 登录成功（`POST /api/auth/login`）后持久化令牌并回显用户名，
///   通过命名路由 `/home` 替换栈顶进入主页；
/// - 提交过程中禁用输入与按钮，展示加载指示。
class LoginPage extends StatefulWidget {
  const LoginPage({super.key, required this.apiClient, this.message});

  final ApiClient apiClient;

  /// 从主页因登录失效跳转过来时展示的提示文案。
  final String? message;

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

class _LoginPageState extends State<LoginPage> {
  final _usernameController = TextEditingController();
  final _passwordController = TextEditingController();
  final _passwordFocus = FocusNode();

  bool _busy = false;
  String? _error;

  @override
  void initState() {
    super.initState();
    _error = widget.message;
    // 回显上次登录的用户名（对应 LoginViewModel.lastUsername()）。
    widget.apiClient.getUsername().then((name) {
      if (mounted && name != null && name.isNotEmpty) {
        _usernameController.text = name;
      }
    });
  }

  @override
  void dispose() {
    _usernameController.dispose();
    _passwordController.dispose();
    _passwordFocus.dispose();
    super.dispose();
  }

  /// 读取并校验输入；返回 null 表示校验未通过（错误已展示）。
  ({String username, String password})? _readInput() {
    final username = _usernameController.text.trim();
    final password = _passwordController.text.trim();
    if (username.isEmpty || password.isEmpty) {
      setState(() => _error = '请输入用户名和密码');
      return null;
    }
    return (username: username, password: password);
  }

  Future<void> _login() async {
    final input = _readInput();
    if (input == null) return;

    setState(() {
      _busy = true;
      _error = null;
    });
    try {
      await widget.apiClient.login(input.username, input.password);
      if (!mounted) return;
      Navigator.of(context).pushReplacementNamed('/home');
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _busy = false;
        _error = _describe(e, '登录失败');
      });
    }
  }

  Future<void> _register() async {
    final input = _readInput();
    if (input == null) return;

    setState(() {
      _busy = true;
      _error = null;
    });
    try {
      await widget.apiClient.register(input.username, input.password);
      if (!mounted) return;
      setState(() {
        _busy = false;
        _error = '注册成功，请登录';
      });
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _busy = false;
        _error = _describe(e, '注册失败');
      });
    }
  }

  /// 优先展示服务端返回的错误文案，其余异常回落到通用提示。
  String _describe(Object e, String fallback) {
    if (e is ApiException) return e.code;
    return '$fallback：$e';
  }

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      navigationBar: const CupertinoNavigationBar(middle: Text('登录')),
      child: SafeArea(
        child: Center(
          child: SingleChildScrollView(
            padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 32),
            child: ConstrainedBox(
              constraints: const BoxConstraints(maxWidth: 420),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  const Icon(
                    CupertinoIcons.device_phone_portrait,
                    size: 56,
                    color: CupertinoColors.activeBlue,
                  ),
                  const SizedBox(height: 16),
                  const Text(
                    'WebRTC 控制端',
                    textAlign: TextAlign.center,
                    style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
                  ),
                  const SizedBox(height: 8),
                  const Text(
                    '登录后可连接已绑定的被控设备',
                    textAlign: TextAlign.center,
                    style: TextStyle(
                      fontSize: 13,
                      color: CupertinoColors.systemGrey,
                    ),
                  ),
                  const SizedBox(height: 32),
                  CupertinoTextField(
                    controller: _usernameController,
                    enabled: !_busy,
                    placeholder: '用户名',
                    prefix: const Padding(
                      padding: EdgeInsets.only(left: 12),
                      child: Icon(CupertinoIcons.person,
                          size: 20, color: CupertinoColors.systemGrey),
                    ),
                    textInputAction: TextInputAction.next,
                    autocorrect: false,
                    onSubmitted: (_) => _passwordFocus.requestFocus(),
                    padding: const EdgeInsets.symmetric(
                        vertical: 14, horizontal: 12),
                  ),
                  const SizedBox(height: 12),
                  CupertinoTextField(
                    controller: _passwordController,
                    focusNode: _passwordFocus,
                    enabled: !_busy,
                    placeholder: '密码',
                    obscureText: true,
                    prefix: const Padding(
                      padding: EdgeInsets.only(left: 12),
                      child: Icon(CupertinoIcons.lock,
                          size: 20, color: CupertinoColors.systemGrey),
                    ),
                    textInputAction: TextInputAction.done,
                    onSubmitted: (_) => _busy ? null : _login(),
                    padding: const EdgeInsets.symmetric(
                        vertical: 14, horizontal: 12),
                  ),
                  if (_error != null) ...[
                    const SizedBox(height: 12),
                    Text(
                      _error!,
                      textAlign: TextAlign.center,
                      style: const TextStyle(
                        fontSize: 13,
                        color: CupertinoColors.destructiveRed,
                      ),
                    ),
                  ],
                  const SizedBox(height: 24),
                  CupertinoButton.filled(
                    onPressed: _busy ? null : _login,
                    child: _busy
                        ? const CupertinoActivityIndicator(
                            color: CupertinoColors.white)
                        : const Text('登录'),
                  ),
                  const SizedBox(height: 8),
                  CupertinoButton(
                    onPressed: _busy ? null : _register,
                    child: const Text('注册新账号'),
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}