import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:mobile_scanner/mobile_scanner.dart';

import 'mobile_scanner_arguments.dart';

import  'web/flutter_qr_web.dart';

enum Ratio { ratio_4_3, ratio_16_9 }

/// A widget showing a live camera preview.
class MobileScanner extends StatefulWidget {
  /// The controller of the camera.
  final MobileScannerController? controller;

  /// Function that gets called when a Barcode is detected.
  ///
  /// [barcode] The barcode object with all information about the scanned code.
  /// [args] Information about the state of the MobileScanner widget
  final Function(Barcode barcode, MobileScannerArguments? args)? onDetect;

  /// TODO: Function that gets called when the Widget is initialized. Can be usefull
  /// to check wether the device has a torch(flash) or not.
  ///
  /// [args] Information about the state of the MobileScanner widget
  // final Function(MobileScannerArguments args)? onInitialize;

  /// Handles how the widget should fit the screen.
  final BoxFit fit;

  /// Create a [MobileScanner] with a [controller], the [controller] must has been initialized.
  const MobileScanner(
      {Key? key, this.onDetect, this.controller, this.fit = BoxFit.cover})
      : assert((controller != null)),
        super(key: key);

  @override
  State<MobileScanner> createState() => _MobileScannerState();
}

class _MobileScannerState extends State<MobileScanner>
    with WidgetsBindingObserver {
  bool onScreen = true;
  late MobileScannerController controller;

  @override
  void initState() {
    super.initState();
    if (widget.controller == null) {
      controller = MobileScannerController();
    } else {
      controller = widget.controller!;
    }
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      setState(() => onScreen = true);
    } else {
      if (onScreen) {
        controller.stop();
      }
      setState(() {
        onScreen = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    if (kIsWeb) {
      return createWebQrView(
        onDetect: (barcode) => widget.onDetect!(barcode, null),
        cameraFacing: CameraFacing.back,
      );
    } else {
      return LayoutBuilder(builder: (context, BoxConstraints constraints) {
        if (!onScreen) return const Text("Camera Paused.");
        return ValueListenableBuilder(
            valueListenable: controller.args,
            builder: (context, value, child) {
              value = value as MobileScannerArguments?;
              if (value == null) {
                return Container(color: Colors.black);
              } else {
                controller.barcodes.listen(
                        (a) =>
                        widget.onDetect!(a, value as MobileScannerArguments));
                return ClipRect(
                  child: SizedBox(
                    width: MediaQuery
                        .of(context)
                        .size
                        .width,
                    height: MediaQuery
                        .of(context)
                        .size
                        .height,
                    child: FittedBox(
                      fit: widget.fit,
                      child: SizedBox(
                        width: value.size.width,
                        height: value.size.height,
                        child: Texture(textureId: value.textureId),
                      ),
                    ),
                  ),
                );
              }
            });
      });
    }
  }

  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }
}