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

import '../core/api_client.dart';
import '../core/app_exception.dart';
import '../core/error_codes.dart';
import '../core/error_l10n.dart';
import '../l10n/app_localizations.dart';

/// 修改密码页（P3 计划 Task 3；入口在设置页）。
///
/// 当前/新/确认三字段；客户端校验（新密码 ≥8 位、两次一致）先行，
/// 服务端 [ApiClient.changePassword] 成功后 204——当前会话被服务端保留，
/// 无需重登录：toast 提示后直接 pop 回设置页。
/// AUTH_INVALID_CREDENTIALS 在本页语义为「当前密码错误」（覆写通用映射）。
class PasswordChangePage extends ConsumerStatefulWidget {
  const PasswordChangePage({super.key});

  @override
  ConsumerState<PasswordChangePage> createState() =>
      _PasswordChangePageState();
}

class _PasswordChangePageState extends ConsumerState<PasswordChangePage> {
  final _formKey = GlobalKey<FormState>();
  final _oldController = TextEditingController();
  final _newController = TextEditingController();
  final _confirmController = TextEditingController();

  bool _obscureAll = true;
  bool _submitting = false;

  @override
  void dispose() {
    _oldController.dispose();
    _newController.dispose();
    _confirmController.dispose();
    super.dispose();
  }

  Future<void> _submit() async {
    if (!_formKey.currentState!.validate()) return;
    setState(() => _submitting = true);
    final l10n = AppLocalizations.of(context);
    final messenger = ScaffoldMessenger.of(context);
    final navigator = Navigator.of(context);
    try {
      await ref.read(apiClientProvider).changePassword(
            _oldController.text,
            _newController.text,
          );
      // 成功路径：先弹提示再 pop；pop 后 SnackBar 仍挂在根 messenger 上可见。
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.passwordChangeSuccess)),
      );
      navigator.pop();
    } on AppException catch (error) {
      messenger.showSnackBar(
        SnackBar(
          content: Text(
            error.code == ErrorCodes.authInvalidCredentials
                ? l10n.errorOldPasswordIncorrect
                : l10n.messageForError(error),
          ),
        ),
      );
    } on Object {
      messenger.showSnackBar(
        SnackBar(content: Text(l10n.errorGeneric)),
      );
    } finally {
      if (mounted) setState(() => _submitting = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    return Scaffold(
      appBar: AppBar(title: Text(l10n.passwordChangeTitle)),
      body: Center(
        child: ConstrainedBox(
          constraints: const BoxConstraints(maxWidth: 420),
          child: Padding(
            padding: const EdgeInsets.all(24),
            child: Form(
              key: _formKey,
              autovalidateMode: AutovalidateMode.onUserInteraction,
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  TextFormField(
                    controller: _oldController,
                    obscureText: _obscureAll,
                    enableSuggestions: false,
                    autocorrect: false,
                    decoration: InputDecoration(
                      labelText: l10n.currentPassword,
                      border: const OutlineInputBorder(),
                    ),
                    validator: (value) => (value == null || value.isEmpty)
                        ? l10n.fieldRequired
                        : null,
                  ),
                  const SizedBox(height: 16),
                  TextFormField(
                    controller: _newController,
                    obscureText: _obscureAll,
                    enableSuggestions: false,
                    autocorrect: false,
                    decoration: InputDecoration(
                      labelText: l10n.newPassword,
                      border: const OutlineInputBorder(),
                    ),
                    validator: (value) {
                      if (value == null || value.isEmpty) {
                        return l10n.fieldRequired;
                      }
                      if (value.length < 8) return l10n.passwordMinLength;
                      return null;
                    },
                  ),
                  const SizedBox(height: 16),
                  TextFormField(
                    controller: _confirmController,
                    obscureText: _obscureAll,
                    enableSuggestions: false,
                    autocorrect: false,
                    onFieldSubmitted: (_) => _submitting ? null : _submit(),
                    decoration: InputDecoration(
                      labelText: l10n.confirmNewPassword,
                      border: const OutlineInputBorder(),
                    ),
                    validator: (value) {
                      if (value == null || value.isEmpty) {
                        return l10n.fieldRequired;
                      }
                      if (value != _newController.text) {
                        return l10n.passwordMismatch;
                      }
                      return null;
                    },
                  ),
                  const SizedBox(height: 8),
                  Align(
                    alignment: Alignment.centerRight,
                    child: IconButton(
                      onPressed: () =>
                          setState(() => _obscureAll = !_obscureAll),
                      icon: Icon(
                        _obscureAll
                            ? Icons.visibility_outlined
                            : Icons.visibility_off_outlined,
                      ),
                    ),
                  ),
                  const SizedBox(height: 16),
                  FilledButton(
                    onPressed: _submitting ? null : _submit,
                    child: _submitting
                        ? const SizedBox(
                            height: 20,
                            width: 20,
                            child: CircularProgressIndicator(strokeWidth: 2),
                          )
                        : Text(l10n.passwordChangeTitle),
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}