import 'dart:ui' show PlatformDispatcher;

import 'package:camera/camera.dart';
import 'package:flutter/foundation.dart' show defaultTargetPlatform;
import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:wakelock_plus/wakelock_plus.dart';

import '../detection/detector_worker.dart';
import '../reminder/reminder.dart';
import 'app_camera_controller.dart';
import 'camera_view_model.dart';
import 'detection_overlay.dart';
import 'frame_analyzer.dart';

/// 主界面：相机预览 + 检测框 overlay + 顶栏(返回/切换摄像头)
class CameraScreen extends StatefulWidget {
  const CameraScreen({super.key});

  @override
  State<CameraScreen> createState() => _CameraScreenState();
}

class _CameraScreenState extends State<CameraScreen> {
  CameraViewModel? _viewModel;
  FrameAnalyzer? _analyzer;
  AppCameraController? _cameraController;
  bool _initFailed = false;
  bool _permissionGranted = false;
  String? _globalError;
  String? _initError;

  @override
  void initState() {
    super.initState();
    final oldPlatform = PlatformDispatcher.instance.onError;
    PlatformDispatcher.instance.onError = (error, stack) {
      setState(() => _globalError = 'Platform: $error');
      return oldPlatform?.call(error, stack) ?? false;
    };
    WidgetsBinding.instance.addPostFrameCallback((_) => _init());
    // 相机页常亮：野外观察时保持屏幕不熄（离开页面时关闭）
    WakelockPlus.enable();
  }

  Future<void> _init() async {
    final granted = await Permission.camera.request().isGranted;
    if (!mounted) return;
    setState(() => _permissionGranted = granted);
    if (!granted) return;

    // 模型加载/推理在后台 isolate，不阻塞 UI；worker 为 null 时仅预览并提示
    final worker = await DetectorWorker.create();
    final viewModel = CameraViewModel(reminder: Reminder());
    viewModel.setModelReady(worker != null);
    final analyzer = FrameAnalyzer(worker: worker, viewModel: viewModel);
    if (!mounted) {
      analyzer.dispose();
      viewModel.dispose();
      return;
    }
    setState(() {
      _viewModel = viewModel;
      _analyzer = analyzer;
    });

    await _startCamera();
  }

  Future<void> _startCamera() async {
    final analyzer = _analyzer;
    if (analyzer == null) return;
    try {
      final controller = await AppCameraController.create();
      if (controller == null) {
        setState(() {
          _initFailed = true;
          _initError = '未找到可用摄像头';
        });
        return;
      }
      await controller.start(analyzer);
      if (!mounted) {
        controller.stop();
        return;
      }
      setState(() {
        _cameraController = controller;
        _initFailed = false;
        _initError = null;
      });
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _initFailed = true;
        _initError = '$e';
      });
    }
  }

  @override
  void dispose() {
    WakelockPlus.disable();
    _cameraController?.stop();
    _analyzer?.dispose();
    _viewModel?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final vm = _viewModel;
    final camera = _cameraController;

    return Scaffold(
      backgroundColor: Colors.black,
      body: Stack(
        fit: StackFit.expand,
        children: [
          if (!_permissionGranted)
            _PermissionGuide(onRequest: () => _init())
          else if (vm != null && (camera?.isInitialized ?? false))
            // 预览 + 检测框同几何：overlay 作为 CameraPreview 的 child，
            // 与纹理共享同一 Stack/尺寸，避免比例或裁剪导致的位置偏移
            ListenableBuilder(
              listenable: vm,
              builder: (context, _) => _ZoomablePreview(
                controller: camera!.currentController,
                imageWidthPx: vm.state.imageWidthPx,
                imageHeightPx: vm.state.imageHeightPx,
                overlay: DetectionOverlay(
                  results: vm.state.results,
                  // iOS 纹理不旋转显示（_wrapInRotatedBox 仅 Android），
                  // 显示方向 = buffer 原样 = 检测方向，旋转必须为 0；
                  // Android 纹理被 RotatedBox 旋转，需用插件报告的 rotation。
                  rotation: defaultTargetPlatform == TargetPlatform.iOS
                      ? 0
                      : vm.state.rotation,
                  imageWidthPx: vm.state.imageWidthPx,
                  imageHeightPx: vm.state.imageHeightPx,
                ),
              ),
            )
          else if (camera?.isInitialized ?? false)
            _ZoomablePreview(controller: camera!.currentController)
          else
            const Center(
              child: Text('相机启动中…', style: TextStyle(color: Colors.white70)),
            ),

          // 帧级动态层（横幅/诊断行）单独订阅 viewModel，避免整屏重建
          if (vm != null)
            ListenableBuilder(
              listenable: vm,
              builder: (context, _) => _buildDiagnosticsLayer(camera),
            ),

          if (_initFailed)
            Center(
              child: Container(
                padding: const EdgeInsets.all(24),
                decoration: BoxDecoration(
                  color: Colors.black54,
                  borderRadius: BorderRadius.circular(12),
                ),
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    const Text('相机初始化失败', style: TextStyle(color: Colors.white)),
                    if (_initError != null)
                      Padding(
                        padding: const EdgeInsets.only(top: 8),
                        child: Text(
                          _initError!,
                          maxLines: 3,
                          overflow: TextOverflow.ellipsis,
                          textAlign: TextAlign.center,
                          style: const TextStyle(
                              color: Colors.redAccent, fontSize: 11),
                        ),
                      ),
                    TextButton(
                      onPressed: () {
                        setState(() => _initFailed = false);
                        _startCamera();
                      },
                      child: const Text('重试'),
                    ),
                  ],
                ),
              ),
            ),

          Positioned(
            top: MediaQuery.of(context).padding.top + 8,
            left: 0,
            right: 0,
            child: _CameraTopBar(
              onClose: () => Navigator.of(context).pop(),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildDiagnosticsLayer(AppCameraController? camera) {
    final vm = _viewModel!;
    return Stack(
      fit: StackFit.expand,
      children: [
        // 模型未加载时仅显示相机预览，不做检测标注（横幅置于顶栏下方，避免与底部诊断行重叠）
        if (!vm.state.modelReady)
          Positioned(
            left: 16,
            right: 16,
            top: MediaQuery.of(context).padding.top + 56,
            child: Container(
              padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 8),
              decoration: BoxDecoration(
                color: Colors.black54,
                borderRadius: BorderRadius.circular(8),
              ),
              child: Text(
                '识别模型加载失败:${DetectorWorker.lastLoadError ?? '未知原因'}\n最后步骤:${DetectorWorker.lastLog ?? '-'}',
                textAlign: TextAlign.center,
                style: const TextStyle(color: Colors.orange, fontSize: 14),
              ),
            ),
          ),

        Positioned(
          left: 8,
          right: 8,
          bottom: MediaQuery.of(context).padding.bottom + 8,
          child: Column(
            mainAxisSize: MainAxisSize.min,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              Text(
                '模型:${vm.state.modelReady ? '已加载' : '未加载'} 帧:${vm.state.framesReceived} 流:${camera?.streamCallbacks ?? 0} 推理:${vm.state.debugDetectCalls}次 异常:${vm.state.debugDetectErrors}次 处理:${vm.state.debugLastMs}ms 最高分:${(vm.state.debugHighestScore * 100).toStringAsFixed(1)}% 图:${vm.state.imageWidthPx}x${vm.state.imageHeightPx} 旋:${vm.state.rotation}',
                style: const TextStyle(color: Colors.white70, fontSize: 12),
              ),
              if (camera != null)
                Text(
                  'streaming:${camera.currentController.value.isStreamingImages} '
                  'camErr:${camera.currentController.value.errorDescription ?? '无'}',
                  maxLines: 2,
                  overflow: TextOverflow.ellipsis,
                  style: const TextStyle(
                      color: Colors.cyanAccent, fontSize: 11),
                ),
              if (vm.state.debugLastError != null)
                Text(
                  vm.state.debugLastError!,
                  maxLines: 2,
                  overflow: TextOverflow.ellipsis,
                  textAlign: TextAlign.center,
                  style: const TextStyle(
                      color: Colors.redAccent, fontSize: 11),
                ),
              if (_globalError != null)
                Text(
                  _globalError!,
                  maxLines: 3,
                  overflow: TextOverflow.ellipsis,
                  textAlign: TextAlign.center,
                  style: const TextStyle(
                      color: Colors.redAccent, fontSize: 11),
                ),
            ],
          ),
        ),
      ],
    );
  }
}

/// 双指捏合缩放预览；overlay 与纹理同几何（CameraPreview child）
class _ZoomablePreview extends StatefulWidget {
  final CameraController controller;

  /// 检测框 overlay（随帧更新，作为 CameraPreview 的 child 与纹理同区域）
  final Widget? overlay;

  /// 当前帧图像尺寸（用于按 buffer 比例约束预览，保证无拉伸变形）
  final int imageWidthPx;
  final int imageHeightPx;

  const _ZoomablePreview({
    required this.controller,
    this.overlay,
    this.imageWidthPx = 0,
    this.imageHeightPx = 0,
  });

  @override
  State<_ZoomablePreview> createState() => _ZoomablePreviewState();
}

class _ZoomablePreviewState extends State<_ZoomablePreview> {
  double _minZoom = 1.0;
  double _maxZoom = 1.0;
  double _currentZoom = 1.0;
  double _gestureStartZoom = 1.0;

  @override
  void initState() {
    super.initState();
    widget.controller.getMinZoomLevel().then((v) {
      if (mounted) setState(() => _minZoom = v);
    });
    widget.controller.getMaxZoomLevel().then((v) {
      if (mounted) setState(() => _maxZoom = v);
    });
  }

  @override
  Widget build(BuildContext context) {
    final preview = GestureDetector(
      onScaleStart: (_) => _gestureStartZoom = _currentZoom,
      onScaleUpdate: (d) {
        final target =
            (_gestureStartZoom * d.scale).clamp(_minZoom, _maxZoom);
        if ((target - _currentZoom).abs() < 0.01) return;
        _currentZoom = target;
        widget.controller.setZoomLevel(target);
      },
      child: CameraPreview(widget.controller, child: widget.overlay),
    );

    final w = widget.imageWidthPx.toDouble();
    final h = widget.imageHeightPx.toDouble();
    if (w <= 0 || h <= 0) return preview;
    // 按 buffer 比例约束显示区域：纹理与 overlay 同区域等比显示（无变形）
    return Center(
      child: AspectRatio(aspectRatio: w / h, child: preview),
    );
  }
}

class _CameraTopBar extends StatelessWidget {
  final VoidCallback onClose;

  const _CameraTopBar({
    required this.onClose,
  });

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.black54,
      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          IconButton(
            tooltip: '返回',
            icon: const Icon(Icons.arrow_back, color: Colors.white),
            onPressed: onClose,
          ),
        ],
      ),
    );
  }
}

class _PermissionGuide extends StatelessWidget {
  final VoidCallback onRequest;

  const _PermissionGuide({required this.onRequest});

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          const Text(
            '需要相机权限才能进行实时识别',
            style: TextStyle(color: Colors.white),
          ),
          const SizedBox(height: 16),
          FilledButton(onPressed: onRequest, child: const Text('授权相机')),
        ],
      ),
    );
  }
}