camera.dart

import 'dart:async';

import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';

final MethodChannel _channel = const MethodChannel('plugins.flutter.io/camera')
  ..invokeMethod('init');

enum CameraLensDirection { front, back, external }

enum ResolutionPreset { low, medium, high }

/// Returns the resolution preset as a String.
String serializeResolutionPreset(ResolutionPreset resolutionPreset) {
  switch (resolutionPreset) {
    case ResolutionPreset.high:
      return 'high';
    case ResolutionPreset.medium:
      return 'medium';
    case ResolutionPreset.low:
      return 'low';
  }
  throw ArgumentError('Unknown ResolutionPreset value');
}

CameraLensDirection _parseCameraLensDirection(String string) {
  switch (string) {
    case 'front':
      return CameraLensDirection.front;
    case 'back':
      return CameraLensDirection.back;
    case 'external':
      return CameraLensDirection.external;
  }
  throw ArgumentError('Unknown CameraLensDirection value');
}

/// Completes with a list of available cameras.
///
/// May throw a [CameraException].
Future<List<CameraDescription>> availableCameras() async {
  try {
    final List<dynamic> cameras =
        await _channel.invokeMethod('availableCameras');
    return cameras.map((dynamic camera) {
      return CameraDescription(
        name: camera['name'],
        lensDirection: _parseCameraLensDirection(camera['lensFacing']),
      );
    }).toList();
  } on PlatformException catch (e) {
    throw CameraException(e.code, e.message);
  }
}

class CameraDescription {
  CameraDescription({this.name, this.lensDirection});

  final String name;
  final CameraLensDirection lensDirection;

  @override
  bool operator ==(Object o) {
    return o is CameraDescription &&
        o.name == name &&
        o.lensDirection == lensDirection;
  }

  @override
  int get hashCode {
    return hashValues(name, lensDirection);
  }

  @override
  String toString() {
    return '$runtimeType($name, $lensDirection)';
  }
}

/// This is thrown when the plugin reports an error.
class CameraException implements Exception {
  CameraException(this.code, this.description);

  String code;
  String description;

  @override
  String toString() => '$runtimeType($code, $description)';
}

// Build the UI texture view of the video data with textureId.
class CameraPreview extends StatelessWidget {
  const CameraPreview(this.controller);

  final CameraController controller;

  @override
  Widget build(BuildContext context) {
    return controller.value.isInitialized
        ? Texture(textureId: controller._textureId)
        : Container();
  }
}

/// The state of a [CameraController].
class CameraValue {
  const CameraValue({
    this.isInitialized,
    this.errorDescription,
    this.previewSize,
    this.isRecordingVideo,
    this.isTakingPicture,
  });

  const CameraValue.uninitialized()
      : this(
            isInitialized: false,
            isRecordingVideo: false,
            isTakingPicture: false);

  /// True after [CameraController.initialize] has completed successfully.
  final bool isInitialized;

  /// True when a picture capture request has been sent but as not yet returned.
  final bool isTakingPicture;

  /// True when the camera is recording (not the same as previewing).
  final bool isRecordingVideo;

  final String errorDescription;

  /// The size of the preview in pixels.
  ///
  /// Is `null` until  [isInitialized] is `true`.
  final Size previewSize;

  /// Convenience getter for `previewSize.height / previewSize.width`.
  ///
  /// Can only be called when [initialize] is done.
  double get aspectRatio => previewSize.height / previewSize.width;

  bool get hasError => errorDescription != null;

  CameraValue copyWith({
    bool isInitialized,
    bool isRecordingVideo,
    bool isTakingPicture,
    String errorDescription,
    Size previewSize,
  }) {
    return CameraValue(
      isInitialized: isInitialized ?? this.isInitialized,
      errorDescription: errorDescription,
      previewSize: previewSize ?? this.previewSize,
      isRecordingVideo: isRecordingVideo ?? this.isRecordingVideo,
      isTakingPicture: isTakingPicture ?? this.isTakingPicture,
    );
  }

  @override
  String toString() {
    return '$runtimeType('
        'isRecordingVideo: $isRecordingVideo, '
        'isRecordingVideo: $isRecordingVideo, '
        'isInitialized: $isInitialized, '
        'errorDescription: $errorDescription, '
        'previewSize: $previewSize)';
  }
}

/// Controls a device camera.
///
/// Use [availableCameras] to get a list of available cameras.
///
/// Before using a [CameraController] a call to [initialize] must complete.
///
/// To show the camera preview on the screen use a [CameraPreview] widget.
class CameraController extends ValueNotifier<CameraValue> {
  CameraController(this.description, this.resolutionPreset)
      : super(const CameraValue.uninitialized());

  final CameraDescription description;
  final ResolutionPreset resolutionPreset;

  int _textureId;
  bool _isDisposed = false;
  StreamSubscription<dynamic> _eventSubscription;
  Completer<void> _creatingCompleter;

  /// Initializes the camera on the device.
  ///
  /// Throws a [CameraException] if the initialization fails.
  Future<void> initialize() async {
    if (_isDisposed) {
      return Future<void>.value();
    }
    try {
      _creatingCompleter = Completer<void>();
      final Map<dynamic, dynamic> reply = await _channel.invokeMethod(
        'initialize',
        <String, dynamic>{
          'cameraName': description.name,
          'resolutionPreset': serializeResolutionPreset(resolutionPreset),
        },
      );
      _textureId = reply['textureId'];
      value = value.copyWith(
        isInitialized: true,
        previewSize: Size(
          reply['previewWidth'].toDouble(),
          reply['previewHeight'].toDouble(),
        ),
      );
    } on PlatformException catch (e) {
      throw CameraException(e.code, e.message);
    }
    _eventSubscription =
        EventChannel('flutter.io/cameraPlugin/cameraEvents$_textureId')
            .receiveBroadcastStream()
            .listen(_listener);
    _creatingCompleter.complete();
    return _creatingCompleter.future;
  }

  /// Listen to events from the native plugins.
  ///
  /// A "cameraClosing" event is sent when the camera is closed automatically by the system (for example when the app go to background). The plugin will try to reopen the camera automatically but any ongoing recording will end.
  void _listener(dynamic event) {
    final Map<dynamic, dynamic> map = event;
    if (_isDisposed) {
      return;
    }

    switch (map['eventType']) {
      case 'error':
        value = value.copyWith(errorDescription: event['errorDescription']);
        break;
      case 'cameraClosing':
        value = value.copyWith(isRecordingVideo: false);
        break;
    }
  }

  /// Captures an image and saves it to [path].
  ///
  /// A path can for example be obtained using
  /// [path_provider](https://pub.dartlang.org/packages/path_provider).
  ///
  /// If a file already exists at the provided path an error will be thrown.
  /// The file can be read as this function returns.
  ///
  /// Throws a [CameraException] if the capture fails.
  Future<void> takePicture(String path) async {
    if (!value.isInitialized || _isDisposed) {
      throw CameraException(
        'Uninitialized CameraController.',
        'takePicture was called on uninitialized CameraController',
      );
    }
    if (value.isTakingPicture) {
      throw CameraException(
        'Previous capture has not returned yet.',
        'takePicture was called before the previous capture returned.',
      );
    }
    try {
      value = value.copyWith(isTakingPicture: true);
      await _channel.invokeMethod(
        'takePicture',
        <String, dynamic>{'textureId': _textureId, 'path': path},
      );
      value = value.copyWith(isTakingPicture: false);
    } on PlatformException catch (e) {
      value = value.copyWith(isTakingPicture: false);
      throw CameraException(e.code, e.message);
    }
  }

  /// Start a video recording and save the file to [path].
  ///
  /// A path can for example be obtained using
  /// [path_provider](https://pub.dartlang.org/packages/path_provider).
  ///
  /// The file is written on the flight as the video is being recorded.
  /// If a file already exists at the provided path an error will be thrown.
  /// The file can be read as soon as [stopVideoRecording] returns.
  ///
  /// Throws a [CameraException] if the capture fails.
  Future<void> startVideoRecording(String filePath) async {
    if (!value.isInitialized || _isDisposed) {
      throw CameraException(
        'Uninitialized CameraController',
        'startVideoRecording was called on uninitialized CameraController',
      );
    }
    if (value.isRecordingVideo) {
      throw CameraException(
        'A video recording is already started.',
        'startVideoRecording was called when a recording is already started.',
      );
    }
    try {
      await _channel.invokeMethod(
        'startVideoRecording',
        <String, dynamic>{'textureId': _textureId, 'filePath': filePath},
      );
      value = value.copyWith(isRecordingVideo: true);
    } on PlatformException catch (e) {
      throw CameraException(e.code, e.message);
    }
  }

  /// Stop recording.
  Future<void> stopVideoRecording() async {
    if (!value.isInitialized || _isDisposed) {
      throw CameraException(
        'Uninitialized CameraController',
        'stopVideoRecording was called on uninitialized CameraController',
      );
    }
    if (!value.isRecordingVideo) {
      throw CameraException(
        'No video is recording',
        'stopVideoRecording was called when no video is recording.',
      );
    }
    try {
      value = value.copyWith(isRecordingVideo: false);
      await _channel.invokeMethod(
        'stopVideoRecording',
        <String, dynamic>{'textureId': _textureId},
      );
    } on PlatformException catch (e) {
      throw CameraException(e.code, e.message);
    }
  }

  /// Releases the resources of this camera.
  @override
  Future<void> dispose() async {
    if (_isDisposed) {
      return;
    }
    _isDisposed = true;
    super.dispose();
    if (_creatingCompleter != null) {
      await _creatingCompleter.future;
      await _channel.invokeMethod(
        'dispose',
        <String, dynamic>{'textureId': _textureId},
      );
      await _eventSubscription?.cancel();
    }
  }
}