// ignore_for_file: public_member_api_docs, avoid_print

import 'dart:async';
import 'dart:io';

import 'package:camera/camera.dart';
import 'package:path_provider/path_provider.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

List<CameraDescription> cameras = <CameraDescription>[];

/// Returns a suitable camera icon for [direction].
IconData getCameraLensIcon(CameraLensDirection direction) {
  switch (direction) {
    case CameraLensDirection.back:
      return Icons.camera_rear;
    case CameraLensDirection.front:
      return Icons.camera_front;
    case CameraLensDirection.external:
      return Icons.camera;
    default:
      throw ArgumentError('Unknown lens direction');
  }
}

void logError(String code, String? message) {
  if (message != null) {
    print('Error: $code\nError Message: $message');
  } else {
    print('Error: $code');
  }
}

Future<void> main() async {
  // Fetch the available cameras before initializing the app.
  try {
    WidgetsFlutterBinding.ensureInitialized();
    cameras = await availableCameras();
  } on CameraException catch (e) {
    logError(e.code, e.description);
  }
  runApp(const CameraApp());
}

class CameraExampleHome extends StatefulWidget {
  const CameraExampleHome({Key? key}) : super(key: key);

  @override
  _CameraExampleHomeState createState() => _CameraExampleHomeState();
}

class _CameraExampleHomeState extends State<CameraExampleHome>
    with WidgetsBindingObserver, TickerProviderStateMixin {
  CameraController? controller;
  XFile? imageFile;
  XFile? videoFile;
  bool enableAudio = true;

  // Counting pointers (number of user fingers on screen)
  int _pointers = 0;

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

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

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    final CameraController? cameraController = controller;

    // App state changed before we got the chance to initialize.
    if (cameraController == null || !cameraController.value.isInitialized) {
      return;
    }

    if (state == AppLifecycleState.inactive) {
      cameraController.dispose();
    } else if (state == AppLifecycleState.resumed) {
      onNewCameraSelected(cameraController.description);
    }
  }

  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        title: const Text('Camera example'),
      ),
      body: Column(
        children: <Widget>[
          Expanded(
            child: Container(
              child: Padding(
                padding: const EdgeInsets.all(1.0),
                child: Center(
                  child: _cameraPreviewWidget(),
                ),
              ),
              decoration: BoxDecoration(
                color: Colors.black,
                border: Border.all(
                  color:
                      controller != null && controller!.value.isRecordingVideo
                          ? Colors.redAccent
                          : Colors.grey,
                  width: 3.0,
                ),
              ),
            ),
          ),
          _captureControlRowWidget(),
          Padding(
            padding: const EdgeInsets.all(5.0),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.start,
              children: <Widget>[_cameraTogglesRowWidget()],
            ),
          ),
        ],
      ),
    );
  }

  /// Display the preview from the camera (or a message if the preview is not available).
  Widget _cameraPreviewWidget() {
    final CameraController? cameraController = controller;

    if (cameraController == null || !cameraController.value.isInitialized) {
      return const Text(
        'Tap a camera',
        style: TextStyle(
          color: Colors.white,
          fontSize: 24.0,
          fontWeight: FontWeight.w900,
        ),
      );
    } else {
      return Listener(
        onPointerDown: (_) => _pointers++,
        onPointerUp: (_) => _pointers--,
        child: CameraPreview(
          controller!,
          child: LayoutBuilder(
              builder: (BuildContext context, BoxConstraints constraints) {
            return GestureDetector(
              behavior: HitTestBehavior.opaque,
              onTapDown: (TapDownDetails details) =>
                  onViewFinderTap(details, constraints),
            );
          }),
        ),
      );
    }
  }

  Widget _captureControlRowWidget() {
    final CameraController? cameraController = controller;

    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
      mainAxisSize: MainAxisSize.max,
      children: <Widget>[
        IconButton(
          icon: const Icon(Icons.videocam),
          color: Colors.blue,
          onPressed: cameraController != null &&
                  cameraController.value.isInitialized &&
                  !cameraController.value.isRecordingVideo
              ? onVideoRecordButtonPressed
              : null,
        ),
        IconButton(
          icon: const Icon(Icons.stop),
          color: Colors.red,
          onPressed: cameraController != null &&
                  cameraController.value.isInitialized &&
                  cameraController.value.isRecordingVideo
              ? onStopButtonPressed
              : null,
        ),
      ],
    );
  }

  /// Display a row of toggle to select the camera (or a message if no camera is available).
  Widget _cameraTogglesRowWidget() {
    final List<Widget> toggles = <Widget>[];

    onChanged(CameraDescription? description) {
      if (description == null) {
        return;
      }

      onNewCameraSelected(description);
    }

    if (cameras.isEmpty) {
      return const Text('No camera found');
    } else {
      for (final CameraDescription cameraDescription in cameras) {
        toggles.add(
          SizedBox(
            width: 90.0,
            child: RadioListTile<CameraDescription>(
              title: Icon(getCameraLensIcon(cameraDescription.lensDirection)),
              groupValue: controller?.description,
              value: cameraDescription,
              onChanged:
                  controller != null && controller!.value.isRecordingVideo
                      ? null
                      : onChanged,
            ),
          ),
        );
      }
    }

    return Row(children: toggles);
  }

  String timestamp() => DateTime.now().millisecondsSinceEpoch.toString();

  void showInSnackBar(String message) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text(message)),
    );
  }

  void onViewFinderTap(TapDownDetails details, BoxConstraints constraints) {
    if (controller == null) {
      return;
    }

    final CameraController cameraController = controller!;

    final Offset offset = Offset(
      details.localPosition.dx / constraints.maxWidth,
      details.localPosition.dy / constraints.maxHeight,
    );
    cameraController.setExposurePoint(offset);
    cameraController.setFocusPoint(offset);
  }

  Future<void> onNewCameraSelected(CameraDescription cameraDescription) async {
    if (controller != null) {
      await controller!.dispose();
    }

    final CameraController cameraController = CameraController(
      cameraDescription,
      kIsWeb ? ResolutionPreset.max : ResolutionPreset.medium,
      enableAudio: enableAudio,
      imageFormatGroup: ImageFormatGroup.jpeg,
    );

    controller = cameraController;

    // If the controller is updated then update the UI.
    cameraController.addListener(() {
      if (mounted) {
        setState(() {});
      }
      if (cameraController.value.hasError) {
        showInSnackBar(
            'Camera error ${cameraController.value.errorDescription}');
      }
    });

    try {
      await cameraController.initialize();
    } on CameraException catch (e) {
      _showCameraException(e);
    }

    if (mounted) {
      setState(() {});
    }
  }

  void onVideoRecordButtonPressed() {
    startVideoRecording().then((_) {
      if (mounted) {
        setState(() {});
      }
    });
  }

  void onStopButtonPressed() {
    stopVideoRecording().then((XFile? file) async {
      if (mounted) {
        setState(() {});
      }

      if (file != null) {
        // Save the video elsewhere so that we can find the video
        // using the Files app.
        // The cache directory is not visible.
        // This is purely to demonstrate the issue with the recorded video,
        // it has nothing to do with the bug.
        final dir = await getExternalStorageDirectory();
        final path = dir!.path + Platform.pathSeparator + file.name;
        await file.saveTo(path);

        showInSnackBar('Video recorded to $path');
        videoFile = file;
      }
    });
  }

  Future<void> startVideoRecording() async {
    final CameraController? cameraController = controller;

    if (cameraController == null || !cameraController.value.isInitialized) {
      showInSnackBar('Error: select a camera first.');
      return;
    }

    if (cameraController.value.isRecordingVideo) {
      // A recording is already started, do nothing.
      return;
    }

    try {
      await cameraController.startVideoRecording();
    } on CameraException catch (e) {
      _showCameraException(e);
      return;
    }
  }

  Future<XFile?> stopVideoRecording() async {
    final CameraController? cameraController = controller;

    if (cameraController == null || !cameraController.value.isRecordingVideo) {
      return null;
    }

    try {
      return cameraController.stopVideoRecording();
    } on CameraException catch (e) {
      _showCameraException(e);
      return null;
    }
  }

  void _showCameraException(CameraException e) {
    logError(e.code, e.description);
    showInSnackBar('Error: ${e.code}\n${e.description}');
  }
}

class CameraApp extends StatelessWidget {
  const CameraApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(home: CameraExampleHome());
  }
}