// device_limit_screen.dart — 设备数超上限挡板(#16)。
//
// 登录成功但账户活跃设备数超套餐上限时,顶层路由把用户挡在此页(登录已生效、token
// 已发,但先移除设备降到上限内才进主界面)。降到上限内后清除 deviceLimitProvider 放行。
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../l10n/app_text.dart';
import '../models/device.dart';
import '../pangolin_theme.dart';
import '../services/auth_api.dart';
import '../services/device_identity.dart';
import '../state/account_providers.dart';
import '../state/auth_provider.dart';

class DeviceLimitScreen extends ConsumerStatefulWidget {
  const DeviceLimitScreen({super.key, required this.t, required this.limit});

  final AppText t;
  final DeviceLimit limit;

  @override
  ConsumerState<DeviceLimitScreen> createState() => _DeviceLimitScreenState();
}

class _DeviceLimitScreenState extends ConsumerState<DeviceLimitScreen> {
  String? _busyUuid; // 正在移除的设备 uuid

  Future<void> _remove(String uuid) async {
    setState(() => _busyUuid = uuid);
    try {
      await ref.read(devicesProvider.notifier).remove(uuid);
    } catch (_) {
      // 失败保持在本页;build 会据最新列表决定是否放行。
    } finally {
      if (mounted) setState(() => _busyUuid = null);
    }
  }

  void _removeOldest(List<Device> devices, String currentId) {
    final others = devices.where((d) => d.uuid != currentId).toList()
      ..sort((a, b) {
        final ta = a.lastSeen?.millisecondsSinceEpoch ?? 0;
        final tb = b.lastSeen?.millisecondsSinceEpoch ?? 0;
        return ta.compareTo(tb); // 最久未用在前
      });
    if (others.isNotEmpty) _remove(others.first.uuid);
  }

  Future<void> _logout() async {
    ref.read(deviceLimitProvider.notifier).state = null;
    await ref.read(authProvider.notifier).logout();
  }

  @override
  Widget build(BuildContext context) {
    final t = widget.t;
    final c = context.pangolin;
    final max = widget.limit.maxDevices;
    final currentId = ref.watch(localDeviceIdProvider).valueOrNull ?? '';
    final devicesAsync = ref.watch(devicesProvider);
    final devices = devicesAsync.valueOrNull ?? const <Device>[];

    // 已降到上限内 → 清除挡板放行(下一帧改 provider,避免 build 内写状态)。
    if (devicesAsync.hasValue && devices.length <= max) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        if (mounted && ref.read(deviceLimitProvider) != null) {
          ref.read(deviceLimitProvider.notifier).state = null;
        }
      });
    }

    final removableCount = devices.where((d) => d.uuid != currentId).length;

    return Scaffold(
      backgroundColor: c.bg,
      body: SafeArea(
        child: Center(
          child: ConstrainedBox(
            constraints: const BoxConstraints(maxWidth: 460),
            child: Padding(
              padding: const EdgeInsets.symmetric(horizontal: 20),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  const SizedBox(height: 32),
                  Icon(Icons.devices_other_rounded, size: 40, color: c.accent),
                  const SizedBox(height: 14),
                  Text(t.deviceLimitTitle,
                      textAlign: TextAlign.center,
                      style: TextStyle(color: c.fg1, fontSize: 20, fontWeight: FontWeight.w700)),
                  const SizedBox(height: 8),
                  Text(t.deviceLimitDesc.replaceFirst('%s', '$max'),
                      textAlign: TextAlign.center,
                      style: TextStyle(color: c.fg2, fontSize: 14, height: 1.5)),
                  const SizedBox(height: 18),
                  if (removableCount > 0)
                    OutlinedButton.icon(
                      onPressed: _busyUuid != null ? null : () => _removeOldest(devices, currentId),
                      icon: const Icon(Icons.history_rounded, size: 18),
                      label: Text(t.deviceLimitRemoveOldest),
                      style: OutlinedButton.styleFrom(
                        foregroundColor: c.accent,
                        side: BorderSide(color: c.accentBorder),
                        padding: const EdgeInsets.symmetric(vertical: 12),
                      ),
                    ),
                  const SizedBox(height: 14),
                  Expanded(
                    child: !devicesAsync.hasValue
                        ? Center(child: CircularProgressIndicator(color: c.accent, strokeWidth: 2.4))
                        : ListView.separated(
                            itemCount: devices.length,
                            separatorBuilder: (_, __) => const SizedBox(height: 8),
                            itemBuilder: (_, i) => _deviceTile(c, t, devices[i], currentId),
                          ),
                  ),
                  const SizedBox(height: 8),
                  TextButton(
                    onPressed: _busyUuid != null ? null : _logout,
                    style: TextButton.styleFrom(foregroundColor: c.fg3),
                    child: Text(t.signOut),
                  ),
                  const SizedBox(height: 12),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }

  Widget _deviceTile(PangolinScheme c, AppText t, Device d, String currentId) {
    final isCurrent = d.uuid == currentId;
    final busy = _busyUuid == d.uuid;
    final sub = d.online
        ? t.devOnline
        : (d.lastSeen != null ? '${t.devLastOnline} ${_rel(d.lastSeen!)}' : t.devOffline);
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 12),
      decoration: BoxDecoration(
        color: c.surface,
        borderRadius: BorderRadius.circular(12),
        border: Border.all(color: c.border),
      ),
      child: Row(
        children: [
          Icon(_platformIcon(d.platformKind), size: 22, color: c.fg2),
          const SizedBox(width: 12),
          Expanded(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(d.name.isEmpty ? d.platformKind.label : d.name,
                    maxLines: 1, overflow: TextOverflow.ellipsis,
                    style: TextStyle(color: c.fg1, fontSize: 15, fontWeight: FontWeight.w600)),
                const SizedBox(height: 2),
                Text(sub, style: TextStyle(color: c.fg2, fontSize: 12)),
              ],
            ),
          ),
          const SizedBox(width: 10),
          if (isCurrent)
            Container(
              padding: const EdgeInsets.symmetric(horizontal: 9, vertical: 4),
              decoration: BoxDecoration(
                color: c.accentSubtle,
                borderRadius: BorderRadius.circular(999),
              ),
              child: Text(t.thisDevice, style: TextStyle(color: c.accent, fontSize: 12, fontWeight: FontWeight.w600)),
            )
          else if (busy)
            SizedBox(width: 20, height: 20, child: CircularProgressIndicator(color: c.danger, strokeWidth: 2.2))
          else
            TextButton(
              onPressed: _busyUuid != null ? null : () => _remove(d.uuid),
              style: TextButton.styleFrom(foregroundColor: c.danger),
              child: Text(t.remove),
            ),
        ],
      ),
    );
  }

  static IconData _platformIcon(DevicePlatform p) => switch (p) {
        DevicePlatform.ios || DevicePlatform.android => Icons.smartphone_rounded,
        DevicePlatform.windows || DevicePlatform.linux => Icons.computer_rounded,
        DevicePlatform.macos => Icons.laptop_mac_rounded,
        DevicePlatform.unknown => Icons.devices_other_rounded,
      };

  // 相对时间(粗粒度):x 分钟/小时/天前。
  static String _rel(DateTime t) {
    final d = DateTime.now().toUtc().difference(t.toUtc());
    if (d.inMinutes < 1) return '刚刚';
    if (d.inMinutes < 60) return '${d.inMinutes} 分钟前';
    if (d.inHours < 24) return '${d.inHours} 小时前';
    return '${d.inDays} 天前';
  }
}