// DualCheck 主页面（多参与者版）
// 一个发起方（initiator）提交标准答案，多个参与者（participant）各自提交文本
// 通过 WebSocket 实时同步参与者列表 + 提交状态 + match 结果
import 'dart:async';
import 'dart:convert';
import 'dart:html' if (dart.library.io) 'package:flutter/foundation.dart';

import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:web_socket_channel/web_socket_channel.dart';

import 'api.dart';
import 'nickname_service.dart';

enum _RoleSelect { initiator, participant }

class DualCheck extends StatefulWidget {
  const DualCheck({super.key});

  @override
  State<DualCheck> createState() => _DualCheckState();
}

class _DualCheckState extends State<DualCheck> with WidgetsBindingObserver {
  final _api = DualCheckApi.instance;
  final _nickService = NicknameService.instance;
  final _textCtrl = TextEditingController();

  // ── 会话状态 ──
  String? _sessionId;
  late String _nickname = '用户';       // 本地显示昵称（由 NicknameService 驱动）
  String _serverNick = '';              // 服务端已知的昵称（与 server 同步）
  late _RoleSelect _myRole = _RoleSelect.initiator;
  SessionResp? _session; // 当前会话全量状态（发起方视图）

  // ── WS ──
  WebSocketChannel? _ws;
  StreamSubscription? _wsSub;
  bool _wsStreamDone = false; // WS 底层 stream 是否已关闭

  // ── 浏览器/APP 生命周期 ──
  bool _pageHidden = false;   // 页面是否被隐藏过（paused）——用于识别浏览器手势返回等场景

  // ── rename 失败回滚 ──
  String? _renamePendingOldNick; // 发送 rename 前暂存当前昵称，若后端报错则回滚
  String? _renamePendingNewNick; // 发送 rename 前暂存目标昵称，用于去重

  // ── UI 状态 ──
  bool _isLoading = false;
  String? _errorMsg;
  String? _mySubmittedText; // 自己提交过的文本（发起方提交后展示用）
  bool _initTextExpanded = false; // 发起方已提交文本是否展开
  bool _sessionEndedShown = false; // 防重复弹 session_ended 弹窗
  bool _mySubmitted = false; // 参与者：自己是否已提交
  bool? _myMatch; // 参与者：自己的 match 结果（null=发起方还没提交）

  StreamSubscription<String>? _nickSub;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    _setupBrowserLifecycle();
    _loadNickname();
    // 开启跨标签页同步（仅 Web 生效）
    _nickService.enableCrossTabSync();
    // 监听昵称变化（本地修改 + 其他标签页修改都会触发）
    _nickSub = _nickService.onChanged.listen((n) {
      if (!mounted) return;
      final oldNick = _nickname;
      setState(() => _nickname = n);
      // 如果正在会话中且是参与者，通知后端改名
      if (_sessionId != null && _myRole == _RoleSelect.participant && oldNick != n) {
        debugPrint('[DC] onChanged: old=$oldNick new=$n sessionId=$_sessionId ws=$_ws');
        _sendRename(n);
      } else {
        debugPrint('[DC] onChanged skip: sessionId=$_sessionId role=$_myRole old=$oldNick new=$n');
      }
    });
  }

  Future<void> _loadNickname() async {
    final n = await _nickService.nickname;
    if (!mounted) return;
    setState(() => _nickname = n);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _teardownBrowserLifecycle();
    _nickSub?.cancel();
    _wsSub?.cancel();
    _ws?.sink.close();
    _textCtrl.dispose();
    super.dispose();
  }

  // ── dart:html 浏览器事件监听（处理 Safari bfcache 手势返回恢复） ──
  // visibilitychange：切 tab 触发（切走 hidden，切回 visible）
  // pageshow：页面显示时触发（包括 bfcache 恢复！Safari 手势拉回来必触发）
  // pagehide：页面隐藏时触发（包括 bfcache 冻结！Safari 手势后退必触发）
  void _setupBrowserLifecycle() {
    try {
      // ignore: undefined_function —— dart:html 仅在 Web 编译时可用
      document.onVisibilityChange.listen((_) {
        final hidden = document.hidden ?? false;
        debugPrint('[DC] html visibilitychange hidden=$hidden');
        if (hidden) {
          _pageHidden = true;
        } else {
          _checkAndExit();
        }
      });
      // ignore: undefined_function
      window.onPageShow.listen((e) {
        // persisted=true 表示从 bfcache 恢复（Safari 手势拉回来的场景）
        final persisted = (e as dynamic).persisted as bool? ?? false;
        debugPrint('[DC] html pageshow persisted=$persisted pageHidden=$_pageHidden wsDone=$_wsStreamDone');
        if (persisted) {
          _pageHidden = true; // bfcache 恢复，标记为隐藏过
        }
        _checkAndExit();
      });
      // ignore: undefined_function
      window.onPageHide.listen((e) {
        final persisted = (e as dynamic).persisted as bool? ?? false;
        debugPrint('[DC] html pagehide persisted=$persisted');
        if (persisted) {
          _pageHidden = true;
        }
      });
      debugPrint('[DC] browser lifecycle listeners installed');
    } catch (_) {
      // 非 Web 平台（iOS/Android native）忽略
      debugPrint('[DC] dart:html not available, skip browser lifecycle setup');
    }
  }

  void _teardownBrowserLifecycle() {
    try {
      // ignore: undefined_function
      document.onVisibilityChange.drain();
      // ignore: undefined_function
      window.onPageShow.drain();
      // ignore: undefined_function
      window.onPageHide.drain();
    } catch (_) {}
  }

  // 统一的退出检查：只要"页面被浏览器隐藏过" + "WS 已断" → 强制退出
  void _checkAndExit() {
    if (_pageHidden && _wsStreamDone && _sessionId != null && mounted) {
      debugPrint('[DC] _checkAndExit → force exit (pageHidden+wsDone)');
      _reset();
      Navigator.of(context).pop();
    } else if (_pageHidden && _wsStreamDone) {
      debugPrint('[DC] _checkAndExit: conditions met but not mounted or no session');
    } else {
      debugPrint('[DC] _checkAndExit: no exit. pageHidden=$_pageHidden wsDone=$_wsStreamDone session=$_sessionId');
    }
  }

  // ── WidgetsBindingObserver 生命周期：识别浏览器手势返回后又恢复的场景 ──

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.paused || state == AppLifecycleState.inactive) {
      _pageHidden = true;
      debugPrint('[DC] lifecycle: page hidden (paused/inactive)');
    } else if (state == AppLifecycleState.resumed) {
      debugPrint('[DC] lifecycle: page resumed, pageHidden=$_pageHidden wsDone=$_wsStreamDone session=$_sessionId');
      if (_pageHidden) {
        _pageHidden = false;
        // 关键：页面被浏览器隐藏过（手势返回/切标签），恢复后 WS 已断 → 强制退出
        if (_wsStreamDone && _sessionId != null) {
          debugPrint('[DC] page was hidden + WS closed → force exit to home');
          _reset();
          if (mounted) {
            Navigator.of(context).pop();
          }
        }
      }
    }
  }

  // ── 发起方：创建会话 ──
  Future<void> _createSession() async {
    setState(() => _isLoading = true);
    try {
      final bid = await _nickService.browserId;
      final resp = await _api.createSession(nickname: _nickname, browserId: bid);
      setState(() {
        _sessionId = resp.sessionId;
        _myRole = _RoleSelect.initiator;
      });
      // WS 连接（发起方不需要 join，直接连接）
      _connectWs();
    } on DioException catch (e) {
      setState(() => _errorMsg = _friendlyError(e, '创建失败'));
    } catch (e) {
      setState(() => _errorMsg = _friendlyError(e, '创建失败'));
    } finally {
      setState(() => _isLoading = false);
    }
  }

  // ── 参与方：输入会话码加入（对话框内校验） ──
  void _showJoinDialog() {
    final ctrl = TextEditingController();
    bool isChecking = false;
    String? err;

    showDialog(
      context: context,
      builder: (ctx) => StatefulBuilder(
        builder: (ctx, set) => AlertDialog(
          title: const Text('输入会话码加入'),
          content: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              TextField(
                controller: ctrl,
                autofocus: true,
                enabled: !isChecking,
                decoration: const InputDecoration(
                  hintText: '粘贴或输入会话码',
                  border: OutlineInputBorder(),
                ),
              ),
              if (err != null)
                Padding(
                  padding: const EdgeInsets.only(top: 10),
                  child: Text(err!,
                      style: const TextStyle(color: Colors.red, fontSize: 13)),
                ),
            ],
          ),
          actions: [
            TextButton(
              onPressed: isChecking ? null : () => Navigator.pop(ctx),
              child: const Text('取消'),
            ),
            FilledButton(
                      onPressed: isChecking
                          ? null
                          : () async {
                      String sid = ctrl.text.trim();
                      if (sid.isEmpty) {
                        set(() => err = '请输入会话码');
                        return;
                      }
                      // 如果粘贴的是 URL，尝试提取 session_id
                      final extracted = _extractSessionId(sid);
                      if (extracted != null) {
                        sid = extracted;
                        ctrl.text = sid;
                      }
                      set(() {
                        isChecking = true;
                        err = null;
                      });
                      try {
                        await _api.checkSession(sid);
                        if (!ctx.mounted) return;
                        Navigator.pop(ctx);
                        setState(() {
                          _sessionId = sid;
                          _myRole = _RoleSelect.participant;
                        });
                        _connectWs();
                      } on DioException catch (e) {
                        set(() {
                          isChecking = false;
                          err = isBizError(e)
                              ? bizErrorMessage(e)
                              : '无法连接服务器';
                        });
                      } catch (e) {
                        set(() {
                          isChecking = false;
                          err = '校验失败：$e';
                        });
                      }
                    },
              child: isChecking
                  ? const SizedBox(width: 16, height: 16,
                      child: CircularProgressIndicator(strokeWidth: 2, color: Colors.white))
                  : const Text('加入'),
            ),
          ],
        ),
      ),
    );
  }

  // ── WS 连接 ──
  Future<void> _connectWs() async {
    final role = _myRole == _RoleSelect.initiator ? 'initiator' : 'participant';
    // 连接时用当前本地昵称；如果参与方被自动改名，server 会在 full_state 或 nickname_auto_changed 里通知
    _serverNick = _nickname;
    final bid = await _nickService.browserId;
    final url = _api.wsUrl(
      sessionId: _sessionId!,
      role: role,
      nickname: _nickname,
      browserId: bid,
    );
    try {
      _ws = WebSocketChannel.connect(Uri.parse(url));
      _wsStreamDone = false;
      _wsSub = _ws!.stream.listen(_onWsMessage, onError: (e) {
        debugPrint('[DC] ws error: $e');
      }, onDone: () {
        debugPrint('[DC] ws stream done (closed)');
        _wsStreamDone = true;
        // 兜底：如果页面之前已被隐藏过（Safari 手势后退 bfcache 场景），
        // WS onDone 可能在 resumed 之后才触发（时序问题），这里立即退出
        if (_pageHidden && _sessionId != null && mounted) {
          debugPrint('[DC] ws done after page hidden → force exit');
          _reset();
          Navigator.of(context).pop();
        }
      });
    } catch (e) {
      debugPrint('[DC] ws connect fail: $e');
    }
  }

  // ── WS 消息处理（事件驱动 UI） ──
  Future<void> _onWsMessage(dynamic raw) async {
    try {
      final msg = WSMessage.fromJson(raw as String);
      switch (msg.type) {
        case 'full_state':
          final s = DualCheckApi.parseSession(msg.data);
          // 在参与者列表中找到自己，提取 match 结果
          bool? myMatch;
          for (final p in s.participants) {
            if (p.nickname == _nickname && p.match != null) {
              myMatch = p.match;
              break;
            }
          }
          setState(() {
            _session = s;
            if (myMatch != null) _myMatch = myMatch;
          });
          // 如果之前已提交但发起方后来才提交 → 弹结果
          if (_mySubmitted && myMatch != null) {
            _showMyResult(myMatch);
          }
        case 'participant_joined':
          final nick = msg.data['nickname'] as String;
          setState(() {
            _session ??= SessionResp(
                sessionId: _sessionId!,
                initiatorNickname: '',
                initiatorReady: false,
                allowResubmit: false,
                ignoreWs: false,
                participants: [],
                ttlSeconds: 0);
            final list = List<ParticipantResp>.from(_session!.participants);
            if (!list.any((p) => p.nickname == nick)) {
              list.add(ParticipantResp(
                  nickname: nick, joined: true, submitted: false));
            }
            _session = _session!.copyWith(participants: list);
          });
        case 'participant_left':
          final nick = msg.data['nickname'] as String;
          setState(() {
            if (_session == null) return;
            final list = List<ParticipantResp>.from(_session!.participants);
            list.removeWhere((p) => p.nickname == nick);
            _session = _session!.copyWith(participants: list);
          });
        case 'participant_submitted':
          final nick = msg.data['nickname'] as String;
          final submitData = msg.data['submit'] as Map<String, dynamic>;
          setState(() {
            if (_session == null) return;
            final list = List<ParticipantResp>.from(_session!.participants);
            final idx = list.indexWhere((p) => p.nickname == nick);
            if (idx >= 0) {
              list[idx] = list[idx].copyWith(
                submitted: true,
                match: submitData['match'] as bool?,
              );
            }
            _session = _session!.copyWith(participants: list);
          });
        case 'initiator_ready':
          setState(() {
            if (_session != null) {
              _session = _session!.copyWith(initiatorReady: true);
            }
          });
        case 'resubmit_changed':
          final allow = msg.data['allow'] as bool;
          setState(() {
            _session ??= SessionResp(
                sessionId: _sessionId!,
                initiatorNickname: '',
                initiatorReady: false,
                allowResubmit: false,
                ignoreWs: false,
                participants: [],
                ttlSeconds: 0);
            _session = _session!.copyWith(allowResubmit: allow);
            if (allow) _errorMsg = null;
          });
        case 'ignore_ws_changed':
          final ignore = msg.data['ignore'] as bool;
          setState(() {
            _session ??= SessionResp(
                sessionId: _sessionId!,
                initiatorNickname: '',
                initiatorReady: false,
                allowResubmit: false,
                ignoreWs: false,
                participants: [],
                ttlSeconds: 0);
            _session = _session!.copyWith(ignoreWs: ignore);
          });
        case 'session_ended':
          // 只有参与者收到才弹窗——发起方自己就是结束者，不需要再提示自己
          if (_myRole == _RoleSelect.participant) _showSessionEnded();
        case 'participant_nickname_changed':
          final oldNick = msg.data['old_nickname'] as String;
          final newNick = msg.data['new_nickname'] as String;
          setState(() {
            if (_session == null) return;
            final list = List<ParticipantResp>.from(_session!.participants);
            final idx = list.indexWhere((p) => p.nickname == oldNick);
            if (idx >= 0) {
              list[idx] = list[idx].copyWith(nickname: newNick);
              _session = _session!.copyWith(participants: list);
            }
          });
          // 如果改名的是自己，更新 _serverNick 并清 pending
          if (_myRole == _RoleSelect.participant &&
              (_renamePendingNewNick == newNick || _serverNick == oldNick)) {
            _serverNick = newNick;
            _renamePendingOldNick = null;
            _renamePendingNewNick = null;
          }
        case 'nickname_auto_changed':
          // 服务端因昵称冲突自动改名，只发给改名的那个客户端
          final newNick = msg.data['nickname'] as String;
          final oldNick = _nickname;
          debugPrint('[DC] nickname auto changed: $oldNick → $newNick');
          setState(() {
            _nickname = newNick;
            _serverNick = newNick; // 服务端已经用这个名字了
            _nickService.setNickname(newNick); // 持久化
            // 如果 _session 已初始化，更新自己在 participants 里的记录
            if (_session != null) {
              final list = List<ParticipantResp>.from(_session!.participants);
              final idx = list.indexWhere((p) => p.nickname == oldNick);
              if (idx >= 0) {
                list[idx] = list[idx].copyWith(nickname: newNick);
                _session = _session!.copyWith(participants: list);
              }
            }
          });
          if (mounted) {
            ScaffoldMessenger.of(context).showSnackBar(
              _snack('🔔 昵称冲突，已自动改为 $newNick'),
            );
          }
        case 'error':
          final errMsg = msg.error;
          if (errMsg.isNotEmpty) {
            debugPrint('[DC] ws error from server: $errMsg');
            // 如果是 rename 请求期间收到的错误，回滚本地昵称
            bool needRollback = _renamePendingOldNick != null;
            final rollbackTo = _renamePendingOldNick;
            final pendingNew = _renamePendingNewNick;
            _renamePendingOldNick = null;
            _renamePendingNewNick = null;

            if (needRollback && rollbackTo != null) {
              debugPrint('[DC] rename failed, rolling back to: $rollbackTo');
              setState(() {
                _nickname = rollbackTo;
                _serverNick = rollbackTo; // 恢复 serverNick
                _nickService.setNickname(rollbackTo); // 不 await，避免阻塞 SnackBar
                // 如果 _session 的 participants 里有 pending 的新昵称，恢复回来
                if (_session != null && pendingNew != null) {
                  final list = List<ParticipantResp>.from(_session!.participants);
                  final idx = list.indexWhere((p) => p.nickname == pendingNew);
                  if (idx >= 0) {
                    list[idx] = list[idx].copyWith(nickname: rollbackTo);
                    _session = _session!.copyWith(participants: list);
                  }
                }
              });
            }
            if (_sessionId != null && mounted) {
              ScaffoldMessenger.of(context).showSnackBar(
                _snack(errMsg, icon: Icons.error_outline, color: Colors.red),
              );
            }
          }
      }
    } catch (e) {
      debugPrint('[DC] ws parse error: $e');
    }
  }

  // ── 提交文本 ──
  Future<void> _submit() async {
    if (_sessionId == null) return;
    final text = _textCtrl.text;
    if (text.isEmpty) {
      setState(() => _errorMsg = '请输入内容后再提交');
      return;
    }
    setState(() {
      _isLoading = true;
      _errorMsg = null; // 清除上次残留的报错
    });
    try {
      final role = _myRole == _RoleSelect.initiator ? 'initiator' : 'participant';
      final resp = await _api.submit(
        sessionId: _sessionId!,
        nickname: _nickname,
        role: role,
        text: text,
      );
      // 只清发起方的输入框（发起方提交后有只读预览卡片展示文本，参与者要保留原输入方便重提）
      if (_myRole == _RoleSelect.initiator) _textCtrl.clear();

      // 参与者提交后立刻在本地更新会话状态
      if (_myRole == _RoleSelect.participant) {
        setState(() {
          _session ??= SessionResp(
              sessionId: _sessionId!,
              initiatorNickname: '',
              initiatorReady: false,
              allowResubmit: false,
              ignoreWs: false,
              participants: [],
              ttlSeconds: 0);
          _session = _session!.copyWith(
            initiatorReady: resp.initiatorReady,
          );
          _mySubmitted = true;
          _myMatch = resp.match; // null 表示发起方还没提交
        });
        // 如果 initiator 已提交，可以直接显示 match 弹窗
        if (resp.initiatorReady && resp.match != null) {
          _showMyResult(resp.match!);
        }
      } else {
        // 发起方提交后等 WS full_state 来刷新；同时保存自己的文本用于只读展示
        setState(() => _mySubmittedText = text);
      }
    } on DioException catch (e) {
      final code = bizErrorCode(e);
      String msg;
      if (code == 1003) {
        msg = '已提交过，等待发起方开启"允许重新提交"后再试';
      } else {
        msg = isBizError(e) ? bizErrorMessage(e) : '提交失败';
      }
      setState(() => _errorMsg = msg);
    } catch (e) {
      setState(() => _errorMsg = '提交失败：$e');
    } finally {
      setState(() => _isLoading = false);
    }
  }

  // 从粘贴的 URL/文本中提取会话码
  // 支持的格式：
  //   http://host/?session_id=M_xxx
  //   http://host/api/v1/dual-check/session/M_xxx
  //   /api/v1/dual-check/session/M_xxx
  //   session_id=M_xxx
  //   M_xxx → 原样返回 null（不是 URL）
  String? _extractSessionId(String input) {
    // 1. 先试 query param
    try {
      final uri = Uri.tryParse(input);
      if (uri != null) {
        if (uri.queryParameters['session_id'] case final sid?) return sid;
        // 2. 再试 path 里的 session/XXX 或 check/XXX 段
        final segs = uri.pathSegments;
        for (int i = 0; i < segs.length - 1; i++) {
          if (segs[i] == 'session' || segs[i] == 'check') return segs[i + 1];
        }
      }
    } catch (_) {}
    // 3. 纯文本匹配 session_id=XXX
    final m = RegExp(r'session[_\-]?id=([^\s&]+)', caseSensitive: false).firstMatch(input);
    if (m != null) return m.group(1);
    return null;
  }

  // 通过 WS 发送 rename 消息（仅参与者用）
  void _sendRename(String newNick) {
    if (_ws == null) {
      debugPrint('[DC] _sendRename SKIP: ws is null');
      return;
    }
    // 重要：必须和 _serverNick 比较，不能和 _nickname 比。
    // 因为 _nickService.setNickname() 会同步触发 onChanged 把 _nickname 改成 newNick，
    // 这时再和 _nickname 比永远相等，WS 消息就发不出去了。
    if (newNick == _serverNick) {
      debugPrint('[DC] _sendRename SKIP: same as server-known nick ($_serverNick)');
      return;
    }
    // 暂存旧昵称，用于后端报错时回滚
    _renamePendingOldNick = _serverNick; // 用 serverNick 而不是 _nickname
    _renamePendingNewNick = newNick;
    try {
      final msg = jsonEncode({
        'type': 'rename',
        'data': {'new_nickname': newNick},
      });
      debugPrint('[DC] _sendRename → $msg');
      _ws!.sink.add(msg);
    } catch (e) {
      debugPrint('[DC] _sendRename FAIL: $e');
      _renamePendingOldNick = null;
      _renamePendingNewNick = null;
    }
  }

  // ── 重置 ──
  void _reset() {
    _wsSub?.cancel();
    _ws?.sink.close();
    _textCtrl.clear();
    _renamePendingOldNick = null;
    _renamePendingNewNick = null;
    _serverNick = '';
    setState(() {
      _ws = null;
      _wsSub = null;
      _sessionId = null;
      _session = null;
      _errorMsg = null;
      _mySubmittedText = null;
      _initTextExpanded = false;
      _sessionEndedShown = false;
      _mySubmitted = false;
      _myMatch = null;
    });
  }

  // ── 发起方：主动结束会话（广播给所有人后退出） ──
  Future<void> _confirmAndEndSession() async {
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        icon: const Icon(Icons.warning_amber_rounded, size: 40, color: Colors.orange),
        title: const Text('确定结束会话？'),
        content: const Text('结束后所有参与者都会收到通知并自动退出，无法恢复。'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx, false),
            child: const Text('取消'),
          ),
          FilledButton(
            onPressed: () => Navigator.pop(ctx, true),
            style: FilledButton.styleFrom(backgroundColor: Colors.red),
            child: const Text('确定结束'),
          ),
        ],
      ),
    );
    if (confirmed == true && mounted) {
      await _endSession();
    }
  }

  Future<void> _endSession() async {
    final sid = _sessionId;
    if (sid == null) return;
    try {
      await _api.endSession(sid);
    } catch (e) {
      // 即使网络失败，后端也可能已成功，直接进入 reset
      debugPrint('[DC] endSession api error (ignoring): $e');
    }
    if (!mounted) return;
    _reset();
  }

  // ── 收到 session_ended WS 事件：弹窗 + 自动退出 ──
  void _showSessionEnded() async {
    // 防重复：收到多个 session_ended / 重复触发都只弹一次
    if (!mounted || _sessionId == null || _sessionEndedShown) return;
    _sessionEndedShown = true;
    final sid = _sessionId!;
    await showDialog(
      context: context,
      barrierDismissible: false,
      builder: (ctx) => AlertDialog(
        icon: const Icon(Icons.info_outline, size: 50, color: Colors.blue),
        title: const Text('会话已结束'),
        content: Text('会话 $sid 已由发起方主动结束，即将返回首页。'),
        actions: [
          FilledButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('好的'),
          ),
        ],
      ),
    );
    if (!mounted) return;
    _reset();
  }

  // ── 发起方：切换允许重提交开关 ──
  Future<void> _toggleResubmit(bool value) async {
    final sid = _sessionId;
    if (sid == null) return;
    setState(() {
      _session = _session?.copyWith(allowResubmit: value);
    });
    try {
      final sess = await _api.setResubmit(sid, allow: value);
      if (!mounted) return;
      setState(() => _session = sess);
    } on DioException catch (e) {
      // 失败回滚
      if (!mounted) return;
      setState(() {
        _session = _session?.copyWith(allowResubmit: !value);
      });
      ScaffoldMessenger.of(context).showSnackBar(
        _snack('操作失败：${bizErrorMessage(e)}', icon: Icons.error_outline, color: Colors.red),
      );
    }
  }

  Future<void> _toggleIgnoreWs(bool value) async {
    final sid = _sessionId;
    if (sid == null) return;
    setState(() {
      _session = _session?.copyWith(ignoreWs: value);
    });
    try {
      final sess = await _api.setIgnoreWs(sid, ignore: value);
      if (!mounted) return;
      setState(() => _session = sess);
    } on DioException catch (e) {
      if (!mounted) return;
      setState(() {
        _session = _session?.copyWith(ignoreWs: !value);
      });
      ScaffoldMessenger.of(context).showSnackBar(
        _snack('操作失败：${bizErrorMessage(e)}', icon: Icons.error_outline, color: Colors.red),
      );
    }
  }

  // ── 设置昵称对话框 ──
  void _showNicknameDialog() {
    final ctrl = TextEditingController(text: _nickname);
    final capturedOldNick = _nickname; // 捕获旧昵称（setNickname 是异步的，onChanged 也会 set，这里做个备份）
    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('设置昵称'),
        content: TextField(
          controller: ctrl,
          autofocus: true,
          maxLength: 32,
          decoration: const InputDecoration(
            hintText: '1-32 字符',
            border: OutlineInputBorder(),
            counterText: '',
          ),
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('取消'),
          ),
          FilledButton(
            onPressed: () async {
              final newNick = ctrl.text.trim();
              final ok = await _nickService.setNickname(newNick);
              if (ok && ctx.mounted) Navigator.pop(ctx);
              setState(() {
                if (ok) _nickname = newNick;
              });
              if (ctx.mounted && !ok) {
                ScaffoldMessenger.of(ctx).showSnackBar(
                  _snack('昵称无效', icon: Icons.error_outline, color: Colors.red),
                );
              }
              // 双保险：保存成功后直接通知后端（不管 onChanged 有没有触发）
              if (ok && capturedOldNick != newNick &&
                  _sessionId != null && _myRole == _RoleSelect.participant) {
                debugPrint('[DC] dialog save: old=$capturedOldNick new=$newNick → _sendRename');
                _sendRename(newNick);
              }
            },
            child: const Text('保存'),
          ),
        ],
      ),
    );
  }

  // ── 参与者结果弹窗 ──
  void _showMyResult(bool match) {
    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        icon: Icon(match ? Icons.check_circle : Icons.cancel,
            size: 60, color: match ? Colors.green : Colors.red),
        title: Text(match ? '🎉 完全一致' : '❌ 不相同',
            style: TextStyle(color: match ? Colors.green : Colors.red)),
        actions: [
          TextButton(
              onPressed: () => Navigator.pop(ctx),
              child: const Text('好的')),
        ],
      ),
    );
  }

  // ── UI ──
  @override
  Widget build(BuildContext context) {
    // 会话中：PopScope 拦截所有返回方式（AppBar back、系统返回键、Android 物理返回）
    final Widget body;
    if (_sessionId == null) {
      body = _buildRoleSelect();
    } else {
      body = PopScope(
        canPop: false,
        onPopInvokedWithResult: (didPop, _) async {
          if (didPop) return; // PopScope 允许了 pop
          await _handleWillPop();
        },
        child: SafeArea(
          child: Padding(
            padding: const EdgeInsets.all(16),
            child: _buildSession(),
          ),
        ),
      );
    }

    return Scaffold(
      appBar: AppBar(
        title: const Text('DualCheck 双验'),
        centerTitle: true,
        actions: [
          // 发起者进入会话后，不允许修改发起者昵称，隐藏按钮
          if (_sessionId == null || _myRole != _RoleSelect.initiator)
            IconButton(
              tooltip: '设置昵称',
              icon: const Icon(Icons.person),
              onPressed: _showNicknameDialog,
            ),
        ],
      ),
      body: body,
    );
  }

  // ── PopScope：拦截返回 ──
  Future<void> _handleWillPop() async {
    if (_sessionId == null) return;
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        icon: Icon(
          _myRole == _RoleSelect.initiator
              ? Icons.warning_amber_rounded
              : Icons.exit_to_app,
          size: 40,
          color: _myRole == _RoleSelect.initiator ? Colors.orange : Colors.blue,
        ),
        title: Text(_myRole == _RoleSelect.initiator ? '确定退出会话？' : '确定离开会话？'),
        content: Text(_myRole == _RoleSelect.initiator
            ? '退出将结束会话，所有参与者都会收到通知并自动下线，无法恢复。'
            : '离开后将断开连接，不再接收会话消息。'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx, false),
            child: const Text('取消'),
          ),
          FilledButton(
            onPressed: () => Navigator.pop(ctx, true),
            style: FilledButton.styleFrom(
              backgroundColor: _myRole == _RoleSelect.initiator ? Colors.red : null,
            ),
            child: Text(_myRole == _RoleSelect.initiator ? '结束并退出' : '离开'),
          ),
        ],
      ),
    );
    if (confirmed == true && mounted) {
      if (_myRole == _RoleSelect.initiator) {
        await _endSession(); // 广播 session_ended + 删 Redis → 参与者自动下线
      } else {
        _reset();
      }
    }
  }

  // ── 首页：选择角色 ──
  Widget _buildRoleSelect() {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        const SizedBox(height: 32),
        const Text('双验',
            textAlign: TextAlign.center,
            style: TextStyle(fontSize: 32, fontWeight: FontWeight.bold)),
        const SizedBox(height: 8),
        const Text('多人各输入一段文字，看谁和发起方一致',
            textAlign: TextAlign.center,
            style: TextStyle(color: Colors.grey)),
        const SizedBox(height: 24),
        const Spacer(),
        ElevatedButton.icon(
          onPressed: _isLoading ? null : _createSession,
          icon: const Icon(Icons.add_circle_outline),
          label: Text(_isLoading ? '创建中...' : '我是发起方'),
          style: ElevatedButton.styleFrom(
              padding: const EdgeInsets.symmetric(vertical: 16)),
        ),
        const SizedBox(height: 12),
        OutlinedButton.icon(
          onPressed: _isLoading ? null : _showJoinDialog,
          icon: const Icon(Icons.login),
          label: const Text('我是参与方'),
          style: OutlinedButton.styleFrom(
              padding: const EdgeInsets.symmetric(vertical: 16)),
        ),
        if (_errorMsg != null) _buildError(_errorMsg!),
        const SizedBox(height: 24),
      ],
    );
  }

  // ── 会话页（发起方和参与方共用） ──
  Widget _buildSession() {
    if (_myRole == _RoleSelect.initiator) {
      return _buildInitiatorView();
    } else {
      return _buildParticipantView();
    }
  }

  // 发起方视图
  Widget _buildInitiatorView() {
    final initReady = _session?.initiatorReady ?? false;
    final participants = _session?.participants ?? [];
    final initNick = _session?.initiatorNickname ?? _nickname;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        // ── 上半部分：可滚 ──
        Expanded(
          child: SingleChildScrollView(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                _buildSessionBar(),
                const SizedBox(height: 16),
                if (!initReady) ...[
                  TextField(
                    controller: _textCtrl,
                    maxLines: 4,
                    maxLength: 10000,
                    decoration: const InputDecoration(
                      hintText: '请输入你的答案（标准答案）...',
                      border: OutlineInputBorder(),
                    ),
                  ),
                  const SizedBox(height: 12),
                  ElevatedButton(
                    onPressed: _isLoading ? null : _submit,
                    child: _isLoading
                        ? const CircularProgressIndicator(strokeWidth: 2, color: Colors.white)
                        : const Text('提交标准答案'),
                  ),
                  if (_errorMsg != null) _buildError(_errorMsg!),
                ] else ...[
                  Container(
                    decoration: BoxDecoration(
                      color: Colors.green.shade50,
                      borderRadius: BorderRadius.circular(8),
                      border: Border.all(color: Colors.green.shade200),
                    ),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: [
                        Padding(
                          padding: const EdgeInsets.fromLTRB(12, 10, 8, 6),
                          child: Row(
                            children: [
                              Icon(Icons.check_circle, color: Colors.green.shade700, size: 18),
                              const SizedBox(width: 6),
                              Expanded(
                                child: Text('标准答案已提交（$initNick）',
                                    style: TextStyle(
                                        color: Colors.green.shade700,
                                        fontWeight: FontWeight.w600)),
                              ),
                              if (_mySubmittedText != null && _mySubmittedText!.length > 80)
                                TextButton.icon(
                                  onPressed: () =>
                                      setState(() => _initTextExpanded = !_initTextExpanded),
                                  icon: Icon(
                                    _initTextExpanded
                                        ? Icons.expand_less
                                        : Icons.expand_more,
                                    size: 18,
                                  ),
                                  label: Text(_initTextExpanded ? '收起' : '展开'),
                                  style: TextButton.styleFrom(
                                      padding: EdgeInsets.zero,
                                      minimumSize: Size.zero,
                                      tapTargetSize: MaterialTapTargetSize.shrinkWrap,
                                      foregroundColor: Colors.green.shade700),
                                ),
                              if (_mySubmittedText != null && _mySubmittedText!.isNotEmpty)
                                IconButton(
                                  tooltip: '复制内容',
                                  icon: Icon(Icons.copy, size: 18, color: Colors.green.shade700),
                                  padding: EdgeInsets.zero,
                                  constraints: const BoxConstraints(),
                                  onPressed: () => _copy(_mySubmittedText!),
                                ),
                            ],
                          ),
                        ),
                        if (_mySubmittedText != null)
                          Container(
                            padding: const EdgeInsets.fromLTRB(12, 0, 12, 12),
                            child: Text(
                              _mySubmittedText!,
                              maxLines: _initTextExpanded ? null : 6,
                              style: TextStyle(
                                  color: Colors.green.shade900, height: 1.5),
                            ),
                          ),
                      ],
                    ),
                  ),
                ],
                const SizedBox(height: 24),
                Row(
                  children: [
                    const Text('参与者',
                        style: TextStyle(fontSize: 16, fontWeight: FontWeight.bold)),
                    const Spacer(),
                    Container(
                      padding:
                          const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
                      decoration: BoxDecoration(
                        color: Colors.blue.shade100,
                        borderRadius: BorderRadius.circular(12),
                      ),
                      child: Text('${participants.length} 人',
                          style: TextStyle(
                              color: Colors.blue.shade800,
                              fontSize: 12,
                              fontWeight: FontWeight.bold)),
                    ),
                  ],
                ),
                const SizedBox(height: 8),
                if (participants.isEmpty)
                  Container(
                    height: 160,
                    alignment: Alignment.center,
                    child: Column(
                      mainAxisSize: MainAxisSize.min,
                      children: [
                        Icon(Icons.group_outlined,
                            size: 48, color: Colors.grey.shade300),
                        const SizedBox(height: 8),
                        const Text('暂无参与者，把会话码分享给他们吧',
                            style: TextStyle(color: Colors.grey)),
                      ],
                    ),
                  )
                else
                  SizedBox(
                    height: 200,
                    child: ListView.separated(
                      itemCount: participants.length,
                      separatorBuilder: (_, _) => const SizedBox(height: 8),
                      itemBuilder: (_, i) =>
                          _buildParticipantCard(participants[i]),
                    ),
                  ),
                const SizedBox(height: 16),
              ],
            ),
          ),
        ),
        // ── 底部控制区：永远贴底 ──
        SwitchListTile.adaptive(
          contentPadding: const EdgeInsets.symmetric(horizontal: 4),
          title: const Text('允许参与者重新提交'),
          value: _session?.allowResubmit ?? false,
          onChanged: _toggleResubmit,
        ),
        SwitchListTile.adaptive(
          contentPadding: const EdgeInsets.symmetric(horizontal: 4),
          title: const Text('比对时忽略首尾空白'),
          value: _session?.ignoreWs ?? false,
          onChanged: _toggleIgnoreWs,
        ),
        const SizedBox(height: 8),
        ElevatedButton(onPressed: _confirmAndEndSession, child: const Text('结束会话')),
      ],
    );
  }

  Widget _buildParticipantCard(ParticipantResp p) {
    IconData icon;
    Color color;
    String status;
    if (!p.submitted) {
      icon = Icons.hourglass_empty;
      color = Colors.orange;
      status = '等待提交';
    } else if (p.match == null) {
      icon = Icons.check_circle;
      color = Colors.blue;
      status = '已提交';
    } else if (p.match == true) {
      icon = Icons.check_circle;
      color = Colors.green;
      status = '正确 ✓';
    } else {
      icon = Icons.cancel;
      color = Colors.red;
      status = '错误 ✗';
    }

    return Container(
      padding: const EdgeInsets.all(12),
      decoration: BoxDecoration(
        color: Colors.grey.shade50,
        borderRadius: BorderRadius.circular(8),
        border: Border.all(color: Colors.grey.shade200),
      ),
      child: Row(
        children: [
          Icon(icon, size: 20, color: color),
          const SizedBox(width: 10),
          Expanded(
            child: Text(
              p.nickname,
              style: const TextStyle(fontWeight: FontWeight.w500),
            ),
          ),
          Container(
            padding:
                const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
            decoration: BoxDecoration(
              color: color.withValues(alpha: 0.15),
              borderRadius: BorderRadius.circular(12),
            ),
            child: Text(status,
                style: TextStyle(color: color, fontSize: 12, fontWeight: FontWeight.w600)),
          ),
        ],
      ),
    );
  }

  // 参与者视图
  Widget _buildParticipantView() {
    final initReady = _session?.initiatorReady ?? false;
    final initNick = _session?.initiatorNickname ?? '(发起方)';

    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        _buildSessionBar(),
        const SizedBox(height: 16),

        // 发起方状态
        Container(
          padding: const EdgeInsets.all(12),
          decoration: BoxDecoration(
            color: initReady ? Colors.green.shade50 : Colors.orange.shade50,
            borderRadius: BorderRadius.circular(8),
          ),
          child: Row(
            children: [
              Icon(
                  initReady
                      ? Icons.check_circle
                      : Icons.hourglass_empty,
                  color: initReady ? Colors.green : Colors.orange),
              const SizedBox(width: 8),
              Expanded(
                child: Text(
                  initReady
                      ? '发起方 $initNick 已提交标准答案'
                      : '发起方 $initNick 还没提交，先提交你自己的也可以',
                  style: TextStyle(
                      color:
                          initReady ? Colors.green.shade700 : Colors.orange.shade700),
                ),
              ),
            ],
          ),
        ),
        const SizedBox(height: 16),

        // 自己的状态条（提交后显示）
        if (_mySubmitted)
          Container(
            padding: const EdgeInsets.all(12),
            decoration: BoxDecoration(
              color: _myMatch == null
                  ? Colors.blue.shade50
                  : (_myMatch! ? Colors.green.shade50 : Colors.red.shade50),
              borderRadius: BorderRadius.circular(8),
            ),
            child: Row(
              children: [
                Icon(
                    _myMatch == null
                        ? Icons.hourglass_empty
                        : (_myMatch! ? Icons.check_circle : Icons.cancel),
                    color: _myMatch == null
                        ? Colors.blue
                        : (_myMatch! ? Colors.green : Colors.red)),
                const SizedBox(width: 8),
                Expanded(
                  child: Text(
                    _myMatch == null
                        ? '已提交，等待发起方提交标准答案后比对...'
                        : (_myMatch! ? '✅ 你的答案和发起方完全一致' : '❌ 你的答案和发起方不一致'),
                    style: TextStyle(
                        color: _myMatch == null
                            ? Colors.blue.shade700
                            : (_myMatch!
                                ? Colors.green.shade700
                                : Colors.red.shade700)),
                  ),
                ),
              ],
            ),
          ),
        if (_mySubmitted) const SizedBox(height: 16),

        // 自己的输入框
        TextField(
          controller: _textCtrl,
          maxLines: 4,
          maxLength: 10000,
          decoration: const InputDecoration(
            hintText: '请输入你的答案...',
            border: OutlineInputBorder(),
          ),
        ),
        const SizedBox(height: 12),
        ElevatedButton(
          onPressed: _isLoading ? null : _submit,
          child: _isLoading
              ? const CircularProgressIndicator(strokeWidth: 2, color: Colors.white)
              : const Text('提交'),
        ),

        if (_errorMsg != null) _buildError(_errorMsg!),

        const Spacer(),
        ElevatedButton(
          onPressed: () async {
            final ok = await showDialog<bool>(
              context: context,
              builder: (ctx) => AlertDialog(
                icon: const Icon(Icons.exit_to_app, size: 40, color: Colors.blue),
                title: const Text('确定离开会话？'),
                content: const Text('离开后将断开连接，不再接收会话消息。'),
                actions: [
                  TextButton(
                    onPressed: () => Navigator.pop(ctx, false),
                    child: const Text('取消'),
                  ),
                  FilledButton(
                    onPressed: () => Navigator.pop(ctx, true),
                    child: const Text('离开'),
                  ),
                ],
              ),
            );
            if (ok == true && mounted) _reset();
          },
          child: const Text('离开会话'),
        ),
      ],
    );
  }

  // ── 通用组件 ──

  Widget _buildSessionBar() {
    return Container(
      padding: const EdgeInsets.all(12),
      decoration: BoxDecoration(
        color: Colors.grey.shade100,
        borderRadius: BorderRadius.circular(8),
      ),
      child: Row(
        children: [
          const Icon(Icons.share, size: 18, color: Colors.grey),
          const SizedBox(width: 8),
          Expanded(
            child: Text(
              _sessionId ?? '',
              style: const TextStyle(fontFamily: 'monospace', fontSize: 13),
            ),
          ),
          IconButton(
            tooltip: '复制',
            onPressed: () => _copy(_sessionId ?? ''),
            icon: const Icon(Icons.copy, size: 18),
          ),
          const SizedBox(width: 8),
          Container(
            padding:
                const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
            decoration: BoxDecoration(
              color: _myRole == _RoleSelect.initiator
                  ? Colors.blue.shade100
                  : Colors.orange.shade100,
              borderRadius: BorderRadius.circular(4),
            ),
            child: Text(
              _myRole == _RoleSelect.initiator ? '发起方' : '参与方',
              style: TextStyle(
                  color: _myRole == _RoleSelect.initiator
                      ? Colors.blue.shade800
                      : Colors.orange.shade800,
                  fontSize: 12,
                  fontWeight: FontWeight.bold),
            ),
          ),
        ],
      ),
    );
  }

  Future<void> _copy(String text) async {
    await Clipboard.setData(ClipboardData(text: text));
    if (!mounted) return;
    ScaffoldMessenger.of(context)
        .showSnackBar(_snack('已复制', icon: Icons.check_circle, color: Colors.green));
  }

  /// 统一的 SnackBar：圆角 + 图标 + 主题色
  SnackBar _snack(String text, {IconData? icon, Color? color, Duration duration = const Duration(seconds: 2)}) {
    final bg = color ?? Colors.grey.shade800;
    return SnackBar(
      content: Row(
        children: [
          if (icon != null) ...[
            Icon(icon, color: Colors.white, size: 20),
            const SizedBox(width: 8),
          ],
          Expanded(child: Text(text, style: const TextStyle(color: Colors.white))),
        ],
      ),
      backgroundColor: bg,
      behavior: SnackBarBehavior.floating,
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8)),
      margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
      duration: duration,
    );
  }

  Widget _buildError(String msg) {
    return Padding(
      padding: const EdgeInsets.only(top: 12),
      child: Container(
        padding: const EdgeInsets.all(10),
        decoration: BoxDecoration(
            color: Colors.red.shade50,
            borderRadius: BorderRadius.circular(6)),
        child: Row(
          children: [
            const Icon(Icons.error_outline, size: 18, color: Colors.red),
            const SizedBox(width: 8),
            Expanded(child: Text(msg, style: const TextStyle(color: Colors.red))),
          ],
        ),
      ),
    );
  }
}

// ── ParticipantResp.copyWith 辅助扩展 ──

extension _ParticipantCopy on ParticipantResp {
  ParticipantResp copyWith({
    String? nickname,
    bool? joined,
    bool? submitted,
    bool? match,
  }) {
    return ParticipantResp(
      nickname: nickname ?? this.nickname,
      joined: joined ?? this.joined,
      submitted: submitted ?? this.submitted,
      match: match ?? this.match,
    );
  }
}

extension _SessionCopy on SessionResp {
  SessionResp copyWith({
    String? sessionId,
    String? initiatorNickname,
    bool? initiatorReady,
    bool? allowResubmit,
    bool? ignoreWs,
    List<ParticipantResp>? participants,
    int? ttlSeconds,
  }) {
    return SessionResp(
      sessionId: sessionId ?? this.sessionId,
      initiatorNickname: initiatorNickname ?? this.initiatorNickname,
      initiatorReady: initiatorReady ?? this.initiatorReady,
      allowResubmit: allowResubmit ?? this.allowResubmit,
      ignoreWs: ignoreWs ?? this.ignoreWs,
      participants: participants ?? this.participants,
      ttlSeconds: ttlSeconds ?? this.ttlSeconds,
    );
  }
}

// ── 全局辅助：把 DioException 转成用户友好的提示 ──
String _friendlyError(Object e, String fallback) {
  if (e is DioException) {
    switch (e.type) {
      case DioExceptionType.connectionError:
      case DioExceptionType.connectionTimeout:
      case DioExceptionType.sendTimeout:
      case DioExceptionType.receiveTimeout:
        return '无法连接到服务器';
      case DioExceptionType.cancel:
        return '请求已取消';
      case DioExceptionType.badResponse:
        return isBizError(e) ? bizErrorMessage(e) : '服务器返回错误';
      default:
        return isBizError(e) ? bizErrorMessage(e) : fallback;
    }
  }
  return '$fallback：$e';
}