import 'dart:async';

import 'package:flutter/material.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/brand_mark.dart';
import 'package:patbond_flutter/features/auth/auth_repository.dart';
import 'package:patbond_flutter/features/auth/session_manager.dart';

enum _SplashState { checking, failed }

/// 启动 Splash（12 号组装稿 §7）：静默恢复会话。
///
/// 流程约束：最短停留 500ms；刷新超时 5s；spinner 等待超过 300ms 才出现；
/// 网络失败不清除本地 refresh token（只有服务端明确 401/40102 才清）。
class SplashPage extends StatefulWidget {
  const SplashPage({
    required this.authRepository,
    required this.sessionManager,
    super.key,
  });

  final AuthRepository authRepository;
  final SessionManager sessionManager;

  @override
  State<SplashPage> createState() => _SplashPageState();
}

class _SplashPageState extends State<SplashPage> {
  _SplashState _state = _SplashState.checking;
  bool _showSpinner = false;
  Timer? _spinnerTimer;

  @override
  void initState() {
    super.initState();
    _restore();
  }

  @override
  void dispose() {
    _spinnerTimer?.cancel();
    super.dispose();
  }

  Future<void> _restore() async {
    _spinnerTimer?.cancel();
    _spinnerTimer = Timer(const Duration(milliseconds: 300), () {
      if (mounted) setState(() => _showSpinner = true);
    });
    final minStay = Future<void>.delayed(const Duration(milliseconds: 500));
    try {
      final result = await widget.authRepository.restoreSession().timeout(
        const Duration(seconds: 5),
      );
      await minStay;
      if (!mounted) return;
      switch (result) {
        case SessionRestoreResult.authenticated:
          widget.sessionManager.markAuthenticated();
        case SessionRestoreResult.noSession:
          widget.sessionManager.markUnauthenticated();
      }
    } on SessionExpiredException {
      // refresh 已被服务端判失效，会话已清、状态机已切换，无需处理。
    } catch (_) {
      // 网络失败 / 超时：token 保留，转错误态供重试。
      await minStay;
      if (!mounted) return;
      setState(() {
        _state = _SplashState.failed;
        _showSpinner = false;
      });
    }
  }

  void _retryRefresh() {
    setState(() {
      _state = _SplashState.checking;
      _showSpinner = false;
    });
    _restore();
  }

  Future<void> _clearCredentialsAndGoLogin() async {
    // 逃生通道：放弃本地凭证，改用账号登录。
    await widget.sessionManager.clearSession();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: AppColors.canvas,
      body: Center(
        child: _state == _SplashState.checking
            ? Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  const BrandMark(),
                  const SizedBox(height: 32),
                  // 占位保高度，spinner 出现时不跳动。
                  SizedBox.square(
                    dimension: 20,
                    child: _showSpinner
                        ? const CircularProgressIndicator(
                            strokeWidth: 2.5,
                            color: AppColors.primary,
                          )
                        : null,
                  ),
                ],
              )
            : Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  const BrandMark(),
                  const SizedBox(height: 24),
                  const Text(
                    '网络连接失败，无法恢复登录',
                    style: TextStyle(color: AppColors.ink, fontSize: 14),
                  ),
                  const SizedBox(height: 16),
                  OutlinedButton(
                    style: OutlinedButton.styleFrom(
                      minimumSize: const Size(120, 44),
                      foregroundColor: AppColors.primaryStrong,
                      side: const BorderSide(color: AppColors.border),
                    ),
                    onPressed: _retryRefresh,
                    child: const Text('重试'),
                  ),
                  const SizedBox(height: 8),
                  TextButton(
                    style: TextButton.styleFrom(
                      foregroundColor: AppColors.primaryStrong,
                      minimumSize: const Size(44, 44),
                    ),
                    onPressed: _clearCredentialsAndGoLogin,
                    child: const Text('改用账号登录'),
                  ),
                ],
              ),
      ),
    );
  }
}