import 'package:camera/camera.dart';
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';

import '../services/coin_scan_gate.dart';
import '../widgets/guide_overlay.dart';
import 'preview_screen.dart';

/// Capture only — blur + detect run after shutter (CoinSnap flow).
class CaptureScreen extends StatefulWidget {
  const CaptureScreen({super.key});

  @override
  State<CaptureScreen> createState() => _CaptureScreenState();
}

class _CaptureScreenState extends State<CaptureScreen>
    with WidgetsBindingObserver {
  final _picker = ImagePicker();

  CameraController? _camera;
  List<CameraDescription> _cameras = const [];
  bool _ready = false;
  bool _busy = false;
  String? _error;
  Size? _previewSize;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    _initCamera();
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _camera?.dispose();
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    final cam = _camera;
    if (cam == null || !cam.value.isInitialized) return;
    if (state == AppLifecycleState.inactive) {
      cam.dispose();
      _camera = null;
      _ready = false;
    } else if (state == AppLifecycleState.resumed) {
      _initCamera();
    }
  }

  Future<void> _initCamera() async {
    try {
      _cameras = await availableCameras();
      if (_cameras.isEmpty) {
        setState(() => _error = '没有可用相机');
        return;
      }
      final back = _cameras.firstWhere(
        (c) => c.lensDirection == CameraLensDirection.back,
        orElse: () => _cameras.first,
      );
      final controller = CameraController(
        back,
        ResolutionPreset.high,
        enableAudio: false,
      );
      await controller.initialize();
      if (!mounted) {
        await controller.dispose();
        return;
      }
      _camera = controller;
      setState(() {
        _ready = true;
        _error = null;
      });
    } catch (e) {
      setState(() => _error = '相机初始化失败: $e');
    }
  }

  Future<void> _openPreviewIfOk(String path) async {
    final result = await CoinScanGate.evaluate(
      imagePath: path,
      captureViewport: _previewSize,
    );
    if (!mounted) return;
    if (!result.ok) {
      final msg = switch (result.fail) {
        CoinGateFail.blurry =>
          '图像过模糊（清晰度 ${(result.blur!.clearScore * 100).toStringAsFixed(0)}%），请重拍',
        CoinGateFail.noCoin => '未检测到硬币，请对准圆框后重拍',
        CoinGateFail.none => '无法处理该图片',
      };
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text(msg), duration: const Duration(seconds: 2)),
      );
      return;
    }
    await Navigator.of(context).push(
      MaterialPageRoute(
        builder: (_) => PreviewScreen(
          imagePath: path,
          captureViewport: _previewSize,
        ),
      ),
    );
  }

  Future<void> _capture() async {
    if (_busy) return;
    final cam = _camera;
    if (cam == null || !cam.value.isInitialized) return;

    setState(() => _busy = true);
    try {
      final shot = await cam.takePicture();
      await _openPreviewIfOk(shot.path);
    } catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('拍照失败: $e')),
        );
      }
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _pickGallery() async {
    if (_busy) return;
    setState(() => _busy = true);
    try {
      final file = await _picker.pickImage(
        source: ImageSource.gallery,
        imageQuality: 100,
        requestFullMetadata: true,
      );
      if (file == null) return;
      await _openPreviewIfOk(file.path);
    } catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('选图失败: $e')),
        );
      }
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _switchCamera() async {
    if (_cameras.length < 2 || _busy) return;
    final current = _camera?.description;
    final next = _cameras.firstWhere(
      (c) => c.lensDirection != current?.lensDirection,
      orElse: () => _cameras.first,
    );
    setState(() => _ready = false);
    await _camera?.dispose();
    final controller = CameraController(
      next,
      ResolutionPreset.high,
      enableAudio: false,
    );
    await controller.initialize();
    if (!mounted) {
      await controller.dispose();
      return;
    }
    _camera = controller;
    setState(() => _ready = true);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        fit: StackFit.expand,
        children: [
          _buildPreview(),
          SafeArea(
            child: Padding(
              padding: const EdgeInsets.fromLTRB(20, 16, 20, 0),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(
                    '硬币扫描',
                    style: Theme.of(context).textTheme.headlineSmall?.copyWith(
                          fontWeight: FontWeight.w700,
                        ),
                  ),
                  const SizedBox(height: 4),
                  Text(
                    '将硬币放入圆框 → blur 清晰度检测 → detect 轮廓锁定',
                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                          color: Colors.white70,
                        ),
                  ),
                ],
              ),
            ),
          ),
          if (_busy)
            const ColoredBox(
              color: Color(0x66000000),
              child: Center(child: CircularProgressIndicator()),
            ),
          Positioned(
            left: 0,
            right: 0,
            bottom: 0,
            child: _buildControls(),
          ),
        ],
      ),
    );
  }

  Widget _buildPreview() {
    if (_error != null) {
      return Center(
        child: Padding(
          padding: const EdgeInsets.all(24),
          child: Text(_error!, textAlign: TextAlign.center),
        ),
      );
    }
    final cam = _camera;
    if (!_ready || cam == null || !cam.value.isInitialized) {
      return const Center(child: CircularProgressIndicator());
    }

    return LayoutBuilder(
      builder: (context, constraints) {
        final previewSize = Size(constraints.maxWidth, constraints.maxHeight);
        _previewSize = previewSize;
        return Stack(
          fit: StackFit.expand,
          children: [
            FittedBox(
              fit: BoxFit.cover,
              child: SizedBox(
                width: cam.value.previewSize?.height ?? previewSize.width,
                height: cam.value.previewSize?.width ?? previewSize.height,
                child: CameraPreview(cam),
              ),
            ),
            GuideOverlay(size: previewSize),
          ],
        );
      },
    );
  }

  Widget _buildControls() {
    return SafeArea(
      child: Padding(
        padding: const EdgeInsets.fromLTRB(28, 12, 28, 24),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            _RoundButton(
              icon: Icons.photo_library_outlined,
              onTap: _busy ? null : _pickGallery,
            ),
            GestureDetector(
              onTap: _busy ? null : _capture,
              child: Container(
                width: 76,
                height: 76,
                decoration: BoxDecoration(
                  shape: BoxShape.circle,
                  border: Border.all(color: Colors.white, width: 4),
                ),
                padding: const EdgeInsets.all(5),
                child: Container(
                  decoration: const BoxDecoration(
                    color: Colors.white,
                    shape: BoxShape.circle,
                  ),
                ),
              ),
            ),
            _RoundButton(
              icon: Icons.flip_camera_ios_outlined,
              onTap: _busy ? null : _switchCamera,
            ),
          ],
        ),
      ),
    );
  }
}

class _RoundButton extends StatelessWidget {
  const _RoundButton({required this.icon, this.onTap});

  final IconData icon;
  final VoidCallback? onTap;

  @override
  Widget build(BuildContext context) {
    return Material(
      color: Colors.white12,
      shape: const CircleBorder(),
      child: InkWell(
        customBorder: const CircleBorder(),
        onTap: onTap,
        child: SizedBox(
          width: 52,
          height: 52,
          child: Icon(icon, color: Colors.white),
        ),
      ),
    );
  }
}