import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../../../core/l10n/app_localizations.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/utils/top_toast.dart';
import '../../../providers/auth_provider.dart';
import 'auth_widgets.dart';
import 'verify_code_screen.dart';

class LoginScreen extends ConsumerStatefulWidget {
  const LoginScreen({super.key});

  @override
  ConsumerState<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends ConsumerState<LoginScreen> {
  final _emailController = TextEditingController();
  final _passwordController = TextEditingController();
  final _emailFocusNode = FocusNode();
  final _passwordFocusNode = FocusNode();
  bool _obscurePassword = true;
  bool _emailTouched = false;
  bool _passwordTouched = false;

  // ── 字符过滤正则（仅允许数字、字母及常用特殊符号）──────────
  static final _emailCharRegex = RegExp(r'[a-zA-Z0-9@._%+\-]');
  static final _passwordCharRegex =
      RegExp(r'[a-zA-Z0-9!@#$%^&*()_\-+={};:",.<>/?~\[\]]');

  // ── 邮箱格式校验 ─────────────────────────────────────────
  static final _emailRegex = RegExp(r'^[^@\s]+@[^@\s]+\.[^@\s]+$');

  bool get _emailValid => _emailRegex.hasMatch(_emailController.text.trim());

  // ── 密码规则校验 (与 Web 端 validateLoginPasswordRule 一致) ──
  bool get _passwordValid {
    final pwd = _passwordController.text;
    if (pwd.isEmpty) return false;
    if (pwd.length < 6 || pwd.length > 16) return false;
    if (pwd.contains(RegExp(r'\s'))) return false;
    if (!RegExp(r'(?=.*[a-zA-Z])(?=.*\d)').hasMatch(pwd)) return false;
    return true;
  }

  bool get _canSubmit => _emailValid && _passwordValid;

  @override
  void initState() {
    super.initState();
    _emailFocusNode.addListener(() {
      if (!_emailFocusNode.hasFocus && _emailController.text.isNotEmpty) {
        setState(() => _emailTouched = true);
      }
    });
    _passwordFocusNode.addListener(() {
      if (!_passwordFocusNode.hasFocus &&
          _passwordController.text.isNotEmpty) {
        setState(() => _passwordTouched = true);
      }
    });
  }

  @override
  void dispose() {
    _emailController.dispose();
    _passwordController.dispose();
    _emailFocusNode.dispose();
    _passwordFocusNode.dispose();
    super.dispose();
  }

  /// 邮箱脱敏显示
  String get _maskedEmail {
    final email = _emailController.text.trim();
    if (!email.contains('@')) return email;
    final parts = email.split('@');
    final name = parts[0];
    if (name.length <= 1) return '$name***@${parts[1]}';
    return '${name[0]}***@${parts[1]}';
  }

  /// 密码校验错误信息（与 Web 端 validateLoginPasswordRule 一致）
  String? _getPasswordError(AppLocalizations l10n) {
    final pwd = _passwordController.text;
    if (pwd.isEmpty) return null;
    if (pwd.length < 6 || pwd.length > 16) return l10n.passwordLengthError;
    if (pwd.contains(RegExp(r'\s'))) return l10n.passwordSpaceError;
    if (!RegExp(r'(?=.*[a-zA-Z])(?=.*\d)').hasMatch(pwd)) {
      return l10n.passwordLetterDigitError;
    }
    return null;
  }

  /// 点击登录 → 先发送验证码，成功后再跳转验证码页面
  Future<void> _handleLoginTap() async {
    final email = _emailController.text.trim();
    if (email.isEmpty || _passwordController.text.isEmpty) return;
    if (!_canSubmit) return;

    final ok = await ref.read(authProvider.notifier).sendLoginCode(
          email: email,
          password: _passwordController.text,
        );
    if (!ok || !mounted) return;

    context.push(
      '/verify-code',
      extra: VerifyCodeArgs(
        email: email,
        password: _passwordController.text,
        maskedEmail: _maskedEmail,
        codeSent: true,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context)!;
    final state = ref.watch(authProvider);
    final cs = Theme.of(context).colorScheme;

    ref.listen<AuthState>(authProvider, (prev, next) {
      if (next.errorMessage != null && next.errorMessage != prev?.errorMessage) {
        final code = next.errorMessage!;
        WidgetsBinding.instance.addPostFrameCallback((_) {
          if (!context.mounted) return;
          final l10n = AppLocalizations.of(context)!;
          showTopToast(
            context,
            message: resolveProviderError(code, l10n) ?? code,
          );
          ref.read(authProvider.notifier).clearError();
        });
      }
    });

    final isDark = Theme.of(context).brightness == Brightness.dark;

    return Scaffold(
      appBar: AppBar(
        elevation: 0,
        leading: IconButton(
          icon: const Icon(Icons.chevron_left, size: 28),
          onPressed: () => context.go('/'),
        ),
      ),
      body: SingleChildScrollView(
        padding: const EdgeInsets.fromLTRB(24, 16, 24, 40),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            // 标题区
            Text(
              l10n.welcomeBack,
              style: TextStyle(
                color: cs.onSurface,
                fontSize: 28,
                fontWeight: FontWeight.w700,
                letterSpacing: -0.5,
              ),
            ),
            const SizedBox(height: 6),
            Text(
              l10n.loginSubtitle,
              style: TextStyle(
                color: cs.onSurface.withAlpha(120),
                fontSize: 14,
              ),
            ),
            const SizedBox(height: 40),

            // 邮箱字段
            Text(
              l10n.email,
              style: TextStyle(
                color: cs.onSurface.withAlpha(153),
                fontSize: 13,
                fontWeight: FontWeight.w500,
              ),
            ),
            const SizedBox(height: 8),
            AuthField(
              controller: _emailController,
              hint: l10n.emailHint,
              keyboardType: TextInputType.emailAddress,
              maxLength: 100,
              focusNode: _emailFocusNode,
              inputFormatters: [
                FilteringTextInputFormatter.allow(_emailCharRegex),
              ],
              onChanged: (_) => setState(() { _emailTouched = false; }),
              errorText: _emailTouched && !_emailValid ? l10n.emailError : null,
              semanticsLabel: 'login_input_email',
            ),
            const SizedBox(height: 20),

            // 密码字段
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Text(
                  l10n.password,
                  style: TextStyle(
                    color: cs.onSurface.withAlpha(153),
                    fontSize: 13,
                    fontWeight: FontWeight.w500,
                  ),
                ),
                Semantics(
                  label: 'login_link_forgot_password',
                  child: GestureDetector(
                    onTap: () => context.push('/forgot-password'),
                    child: Text(
                      l10n.forgotPassword,
                      style: TextStyle(
                        color: AppColors.brand,
                        fontSize: 13,
                        fontWeight: FontWeight.w500,
                      ),
                    ),
                  ),
                ),
              ],
            ),
            const SizedBox(height: 8),
            AuthField(
              controller: _passwordController,
              hint: l10n.loginPasswordHint,
              obscure: _obscurePassword,
              maxLength: 16,
              focusNode: _passwordFocusNode,
              inputFormatters: [
                FilteringTextInputFormatter.allow(_passwordCharRegex),
              ],
              onChanged: (_) => setState(() {}),
              errorText: _passwordTouched
                  ? _getPasswordError(l10n)
                  : null,
              semanticsLabel: 'login_input_password',
              suffixIcon: IconButton(
                onPressed: () =>
                    setState(() => _obscurePassword = !_obscurePassword),
                icon: Icon(
                  _obscurePassword
                      ? Icons.visibility_off_outlined
                      : Icons.visibility_outlined,
                  color: cs.onSurface.withAlpha(120),
                  size: 20,
                ),
              ),
            ),
            const SizedBox(height: 40),

            // 登录按钮
            Semantics(
              label: 'login_btn_submit',
              button: true,
              enabled: _canSubmit && !state.isLoading,
              onTap: (_canSubmit && !state.isLoading) ? _handleLoginTap : null,
              child: SizedBox(
                width: double.infinity,
                height: 50,
                child: ElevatedButton(
                  onPressed: (_canSubmit && !state.isLoading) ? _handleLoginTap : null,
                  style: ElevatedButton.styleFrom(
                    backgroundColor: AppColors.brand,
                    foregroundColor: Colors.black,
                    disabledBackgroundColor: isDark
                        ? AppColors.darkBgTertiary
                        : AppColors.lightBgTertiary,
                    disabledForegroundColor: isDark
                        ? AppColors.darkTextDisabled
                        : AppColors.lightTextDisabled,
                    shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(10),
                    ),
                  ),
                  child: state.isLoading
                      ? const SizedBox(
                          width: 20,
                          height: 20,
                          child: CircularProgressIndicator(
                            strokeWidth: 2,
                            color: Colors.black,
                          ),
                        )
                      : Text(
                          l10n.login,
                          style: const TextStyle(
                            fontSize: 16,
                            fontWeight: FontWeight.w600,
                          ),
                        ),
                ),
              ),
            ),
            const SizedBox(height: 32),

            // 注册引导
            Center(
              child: Row(
                mainAxisSize: MainAxisSize.min,
                children: [
                  Text(
                    l10n.noAccount,
                    style: TextStyle(
                      color: cs.onSurface.withAlpha(120),
                      fontSize: 14,
                    ),
                  ),
                  Semantics(
                    label: 'auth_link_register',
                    child: GestureDetector(
                      onTap: () => context.push('/register'),
                      child: Text(
                        l10n.registerNow,
                        style: const TextStyle(
                          color: AppColors.brand,
                          fontSize: 14,
                          fontWeight: FontWeight.w600,
                        ),
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}