// 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 '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> {
  final _api = DualCheckApi();
  final _nickService = NicknameService.instance;
  final _textCtrl = TextEditingController();

  // ── 会话状态 ──
  String? _sessionId;
  late String _nickname = '用户';
  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;

  // ── UI 状态 ──
  bool _isLoading = false;
  String? _errorMsg;

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

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

  @override
  void dispose() {
    _wsSub?.cancel();
    _ws?.sink.close();
    _textCtrl.dispose();
    super.dispose();
  }

  // ── 发起方：创建会话 ──
  Future<void> _createSession() async {
    setState(() => _isLoading = true);
    try {
      final resp = await _api.createSession(nickname: _nickname);
      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 = isBizError(e) ? bizErrorMessage(e) : '创建失败');
    } catch (e) {
      setState(() => _errorMsg = '创建失败：$e');
    } 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,
                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 {
                      final sid = ctrl.text.trim();
                      if (sid.isEmpty) {
                        set(() => err = '请输入会话码');
                        return;
                      }
                      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 ──
  void _connectWs() {
    final role = _myRole == _RoleSelect.initiator ? 'initiator' : 'participant';
    final url = _api.wsUrl(
      sessionId: _sessionId!,
      role: role,
      nickname: _nickname,
    );
    try {
      _ws = WebSocketChannel.connect(Uri.parse(url));
      _wsSub = _ws!.stream.listen(_onWsMessage, onError: (e) {
        debugPrint('[DC] ws error: $e');
      }, onDone: () {
        debugPrint('[DC] ws closed');
      });
    } catch (e) {
      debugPrint('[DC] ws connect fail: $e');
    }
  }

  // ── WS 消息处理（事件驱动 UI） ──
  void _onWsMessage(dynamic raw) {
    try {
      final msg = WSMessage.fromJson(
          jsonDecode(raw as String) as Map<String, dynamic>);
      switch (msg.type) {
        case 'full_state':
          final s = DualCheckApi.parseSession(msg.data);
          setState(() => _session = s);
        case 'participant_joined':
          final nick = msg.data['nickname'] as String;
          setState(() {
            _session ??= SessionResp(
                sessionId: _sessionId!,
                initiatorNickname: '',
                initiatorReady: false,
                allowResubmit: 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,
                participants: [],
                ttlSeconds: 0);
            _session = _session!.copyWith(allowResubmit: allow);
            if (allow) _errorMsg = null; // 开关打开时清掉上次"不能重提交"的报错
          });
        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();
      }
    } catch (e) {
      debugPrint('[DC] ws parse error: $e');
    }
  }

  // ── 提交文本 ──
  Future<void> _submit() async {
    if (_sessionId == null) return;
    final text = _textCtrl.text.trim();
    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,
      );
      _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,
              participants: [],
              ttlSeconds: 0);
          _session = _session!.copyWith(
            initiatorReady: resp.initiatorReady,
          );
        });
        // 如果 initiator 已提交，可以直接显示 match
        if (resp.initiatorReady && resp.match != null) {
          _showMyResult(resp.match!);
        } else {
          _showParticipantWaiting();
        }
      } else {
        // 发起方提交后等 WS full_state 来刷新
        if (!mounted) return;
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(content: Text('标准答案已提交，等待参与者...')),
        );
      }
    } 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);
    }
  }

  // ── 重置 ──
  void _reset() {
    _wsSub?.cancel();
    _ws?.sink.close();
    _textCtrl.clear();
    setState(() {
      _ws = null;
      _wsSub = null;
      _sessionId = null;
      _session = null;
      _errorMsg = 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() {
    // 防重复弹窗（多次 session_ended / 重复 Build）
    if (!mounted || _sessionId == null) return;
    final sid = _sessionId!;
    _reset();
    if (!mounted) return;
    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'),
          ),
        ],
      ),
    );
  }

  // ── 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(
        SnackBar(content: Text('操作失败：${bizErrorMessage(e)}')),
      );
    }
  }

  // ── 设置昵称对话框 ──
  void _showNicknameDialog() {
    final ctrl = TextEditingController(text: _nickname);
    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('设置昵称'),
        content: TextField(
          controller: ctrl,
          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 ok = await _nickService.setNickname(ctrl.text);
              if (ok && ctx.mounted) Navigator.pop(ctx);
              setState(() {
                if (ok) _nickname = ctrl.text.trim();
              });
              if (ctx.mounted && !ok) {
                ScaffoldMessenger.of(ctx).showSnackBar(
                  const SnackBar(content: Text('昵称无效')),
                );
              }
            },
            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)),
        content: Text('你的昵称：$_nickname'),
        actions: [
          TextButton(
              onPressed: () => Navigator.pop(ctx),
              child: const Text('好的')),
        ],
      ),
    );
  }

  void _showParticipantWaiting() {
    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('已提交，等待发起方确认答案...')),
    );
  }

  // ── 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: [
          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),
        Container(
          padding: const EdgeInsets.all(12),
          decoration: BoxDecoration(
            color: Colors.grey.shade100,
            borderRadius: BorderRadius.circular(8),
          ),
          child: Row(
            children: [
              const Icon(Icons.person, color: Colors.grey),
              const SizedBox(width: 8),
              const Text('当前昵称：'),
              Text(_nickname,
                  style: const TextStyle(fontWeight: FontWeight.bold)),
              const Spacer(),
              TextButton(
                onPressed: _showNicknameDialog,
                child: const Text('修改'),
              ),
            ],
          ),
        ),
        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: [
        _buildSessionBar(),
        const SizedBox(height: 16),
        // 发起方输入框（标准答案）
        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(
            padding: const EdgeInsets.all(12),
            decoration: BoxDecoration(
              color: Colors.green.shade50,
              borderRadius: BorderRadius.circular(8),
            ),
            child: Row(
              children: [
                Icon(Icons.check_circle, color: Colors.green.shade700),
                const SizedBox(width: 8),
                Expanded(
                  child: Text('标准答案已提交（$initNick）',
                      style: TextStyle(color: Colors.green.shade700)),
                ),
              ],
            ),
          ),
        ],
        const SizedBox(height: 24),

        // 参与者列表
        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)
          Expanded(
            child: 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
          Expanded(
            child: ListView.separated(
              itemCount: participants.length,
              separatorBuilder: (_, _) => const SizedBox(height: 8),
              itemBuilder: (_, i) =>
                  _buildParticipantCard(participants[i]),
            ),
          ),

        // 发起方控制区
        SwitchListTile.adaptive(
          contentPadding: const EdgeInsets.symmetric(horizontal: 4),
          title: const Text('允许参与者重新提交'),
          subtitle: const Text('开启后参与者可以覆盖之前的提交结果'),
          value: _session?.allowResubmit ?? false,
          onChanged: _toggleResubmit,
        ),
        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: _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(const SnackBar(content: Text('已复制')));
  }

  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,
    List<ParticipantResp>? participants,
    int? ttlSeconds,
  }) {
    return SessionResp(
      sessionId: sessionId ?? this.sessionId,
      initiatorNickname: initiatorNickname ?? this.initiatorNickname,
      initiatorReady: initiatorReady ?? this.initiatorReady,
      allowResubmit: allowResubmit ?? this.allowResubmit,
      participants: participants ?? this.participants,
      ttlSeconds: ttlSeconds ?? this.ttlSeconds,
    );
  }
}