import 'package:flutter/material.dart';
import 'package:flutter/semantics.dart';
import 'package:flutter/services.dart';
import 'package:patbond_flutter/core/network/api_exception.dart';
import 'package:patbond_flutter/core/theme/app_theme.dart';
import 'package:patbond_flutter/core/widgets/app_text_field.dart';
import 'package:patbond_flutter/core/widgets/auth_scaffold.dart';
import 'package:patbond_flutter/core/widgets/inline_error_banner.dart';
import 'package:patbond_flutter/core/widgets/primary_button.dart';
import 'package:patbond_flutter/features/auth/auth_repository.dart';

enum _Field { username, phone, password, confirm }

/// 注册页（12 号组装稿 §6）。字段按 ADR-004：用户名 + 手机号 + 密码 + 确认密码；
/// 短信验证码行与第三方登录预留区一律不渲染。注册成功即建立会话直接进首页。
class RegisterPage extends StatefulWidget {
  const RegisterPage({required this.authRepository, super.key});

  final AuthRepository authRepository;

  @override
  State<RegisterPage> createState() => _RegisterPageState();
}

class _RegisterPageState extends State<RegisterPage> {
  static final _usernamePattern = RegExp(r'^[A-Za-z][A-Za-z0-9_]{2,19}$');
  static final _phonePattern = RegExp(r'^1\d{10}$');

  final _usernameCtrl = TextEditingController();
  final _phoneCtrl = TextEditingController();
  final _passwordCtrl = TextEditingController();
  final _confirmCtrl = TextEditingController();
  String? _usernameError;
  String? _phoneError;
  String? _passwordError;
  String? _confirmError;
  String? _formError;
  bool _submitting = false;

  @override
  void dispose() {
    _usernameCtrl.dispose();
    _phoneCtrl.dispose();
    _passwordCtrl.dispose();
    _confirmCtrl.dispose();
    super.dispose();
  }

  String? _validateUsernameValue() {
    final value = _usernameCtrl.text.trim();
    if (value.isEmpty) return '请输入用户名';
    if (!_usernamePattern.hasMatch(value)) {
      return '用户名需 3–20 位，字母开头，可含数字和下划线';
    }
    return null;
  }

  String? _validatePhoneValue() {
    final value = _phoneCtrl.text.trim();
    if (value.isEmpty) return '请输入手机号';
    if (!_phonePattern.hasMatch(value)) return '请输入正确的 11 位手机号';
    return null;
  }

  String? _validatePasswordValue() {
    final value = _passwordCtrl.text;
    final lengthOk = value.length >= 8 && value.length <= 32;
    final hasLetter = value.contains(RegExp('[A-Za-z]'));
    final hasDigit = value.contains(RegExp('[0-9]'));
    if (!lengthOk || !hasLetter || !hasDigit) {
      return '密码需 8–32 位，且同时包含字母和数字';
    }
    return null;
  }

  String? _validateConfirmValue() =>
      _confirmCtrl.text == _passwordCtrl.text ? null : '两次输入的密码不一致';

  void _validateOnBlur(_Field field) {
    if (!mounted) return;
    setState(() {
      switch (field) {
        case _Field.username:
          _usernameError = _validateUsernameValue();
        case _Field.phone:
          _phoneError = _validatePhoneValue();
        case _Field.password:
          _passwordError = _validatePasswordValue();
        case _Field.confirm:
          _confirmError = _validateConfirmValue();
      }
    });
  }

  /// 字段变更清除本字段错误与横幅；密码变更时若确认密码已有值，
  /// 同步重校验一致性（组装稿 §6）。
  void _clearError(_Field field) {
    setState(() {
      _formError = null;
      switch (field) {
        case _Field.username:
          _usernameError = null;
        case _Field.phone:
          _phoneError = null;
        case _Field.password:
          _passwordError = null;
          if (_confirmCtrl.text.isNotEmpty) {
            _confirmError = _validateConfirmValue();
          }
        case _Field.confirm:
          _confirmError = null;
      }
    });
  }

  void _showFormError(String message) {
    setState(() => _formError = message);
    SemanticsService.sendAnnouncement(
      View.of(context),
      message,
      TextDirection.ltr,
    );
  }

  Future<void> _submit() async {
    if (_submitting) return;
    final usernameError = _validateUsernameValue();
    final phoneError = _validatePhoneValue();
    final passwordError = _validatePasswordValue();
    final confirmError = _validateConfirmValue();
    if (usernameError != null ||
        phoneError != null ||
        passwordError != null ||
        confirmError != null) {
      setState(() {
        _usernameError = usernameError;
        _phoneError = phoneError;
        _passwordError = passwordError;
        _confirmError = confirmError;
      });
      return;
    }
    setState(() {
      _submitting = true;
      _formError = null;
    });
    try {
      await widget.authRepository.register(
        username: _usernameCtrl.text.trim(),
        phone: '+86${_phoneCtrl.text.trim()}',
        password: _passwordCtrl.text,
      );
      TextInput.finishAutofillContext();
      if (!mounted) return;
      // 会话已建立，根路由切主壳；弹掉注册页露出新首页，不回登录页。
      Navigator.of(context).popUntil((route) => route.isFirst);
    } on ApiBusinessException catch (error) {
      if (!mounted) return;
      switch (error.code) {
        case ApiCodes.usernameTaken:
          setState(() => _usernameError = '该用户名已被使用');
        case ApiCodes.phoneTaken:
          setState(() => _phoneError = '该手机号已注册，可直接登录');
        default:
          _showFormError('注册失败，请稍后重试');
      }
    } on ApiRateLimitException {
      if (!mounted) return;
      _showFormError('尝试次数过多，请稍后再试');
    } on ApiNetworkException {
      if (!mounted) return;
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: const Text('网络异常，请检查网络后重试'),
          action: SnackBarAction(label: '重试', onPressed: _submit),
        ),
      );
    } on SessionExpiredException {
      // 注册请求不带会话，理论不可达。
    } finally {
      if (mounted) setState(() => _submitting = false);
    }
  }

  Widget _blurValidated(_Field field, Widget child) {
    return Focus(
      onFocusChange: (hasFocus) {
        if (!hasFocus) _validateOnBlur(field);
      },
      child: child,
    );
  }

  @override
  Widget build(BuildContext context) {
    return AuthScaffold(
      appBar: AppBar(
        backgroundColor: Colors.transparent,
        elevation: 0,
        scrolledUnderElevation: 0,
        foregroundColor: AppColors.ink,
      ),
      child: AutofillGroup(
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const SizedBox(height: 8),
            Text('创建账号', style: Theme.of(context).textTheme.headlineSmall),
            const SizedBox(height: 8),
            Text(
              '加入 Patbond，记录毛孩子的每一天',
              style: Theme.of(context).textTheme.bodySmall,
            ),
            const SizedBox(height: 32),
            _blurValidated(
              _Field.username,
              AppTextField(
                label: '用户名',
                controller: _usernameCtrl,
                prefixIcon: Icons.person_outline_rounded,
                errorText: _usernameError,
                enabled: !_submitting,
                textInputAction: TextInputAction.next,
                autofillHints: const [AutofillHints.newUsername],
                onChanged: (_) => _clearError(_Field.username),
              ),
            ),
            const SizedBox(height: 16),
            _blurValidated(
              _Field.phone,
              AppTextField(
                label: '手机号',
                controller: _phoneCtrl,
                prefixIcon: Icons.phone_iphone_rounded,
                prefixText: '+86 ',
                errorText: _phoneError,
                enabled: !_submitting,
                keyboardType: TextInputType.phone,
                textInputAction: TextInputAction.next,
                autofillHints: const [AutofillHints.telephoneNumber],
                onChanged: (_) => _clearError(_Field.phone),
              ),
            ),
            const SizedBox(height: 16),
            _blurValidated(
              _Field.password,
              AppTextField(
                label: '密码',
                controller: _passwordCtrl,
                prefixIcon: Icons.lock_outline_rounded,
                obscurable: true,
                errorText: _passwordError,
                helperText: '密码 8–32 位，需包含字母和数字',
                enabled: !_submitting,
                textInputAction: TextInputAction.next,
                autofillHints: const [AutofillHints.newPassword],
                onChanged: (_) => _clearError(_Field.password),
              ),
            ),
            const SizedBox(height: 16),
            _blurValidated(
              _Field.confirm,
              AppTextField(
                label: '确认密码',
                controller: _confirmCtrl,
                prefixIcon: Icons.lock_outline_rounded,
                obscurable: true,
                errorText: _confirmError,
                enabled: !_submitting,
                textInputAction: TextInputAction.done,
                autofillHints: const [AutofillHints.newPassword],
                onChanged: (_) => _clearError(_Field.confirm),
                onSubmitted: (_) => _submit(),
              ),
            ),
            if (_formError != null) ...[
              const SizedBox(height: 16),
              InlineErrorBanner(message: _formError!),
            ],
            const SizedBox(height: 32),
            PrimaryButton(
              label: '注册',
              isLoading: _submitting,
              onPressed: _submit,
            ),
            const SizedBox(height: 16),
            Center(
              child: Row(
                mainAxisSize: MainAxisSize.min,
                children: [
                  const Text(
                    '已有账号？',
                    style: TextStyle(color: AppColors.muted, fontSize: 14),
                  ),
                  TextButton(
                    style: TextButton.styleFrom(
                      foregroundColor: AppColors.primaryStrong,
                      minimumSize: const Size(44, 44),
                      padding: const EdgeInsets.symmetric(horizontal: 8),
                      textStyle: const TextStyle(
                        fontSize: 14,
                        fontWeight: FontWeight.w700,
                      ),
                    ),
                    onPressed: _submitting
                        ? null
                        : () => Navigator.of(context).pop(),
                    child: const Text('直接登录'),
                  ),
                ],
              ),
            ),
            const SizedBox(height: 24),
          ],
        ),
      ),
    );
  }
}