implement torch state in ZXing barcode reader

@@ -5,9 +5,11 @@ import 'dart:ui';
 import 'package:js/js.dart';
 import 'package:mobile_scanner/src/enums/barcode_format.dart';
 import 'package:mobile_scanner/src/enums/camera_facing.dart';
+import 'package:mobile_scanner/src/enums/torch_state.dart';
 import 'package:mobile_scanner/src/objects/barcode_capture.dart';
 import 'package:mobile_scanner/src/objects/start_options.dart';
 import 'package:mobile_scanner/src/web/barcode_reader.dart';
+import 'package:mobile_scanner/src/web/flashlight_delegate.dart';
 import 'package:mobile_scanner/src/web/zxing/result.dart';
 import 'package:mobile_scanner/src/web/zxing/zxing_browser_multi_format_reader.dart';
 import 'package:web/web.dart' as web;
@@ -16,6 +18,9 @@ import 'package:web/web.dart' as web;
 final class ZXingBarcodeReader extends BarcodeReader {
   ZXingBarcodeReader();
 
+  /// The internal flashlight delegate.
+  final FlashlightDelegate _flashlightDelegate = const FlashlightDelegate();
+
   /// The internal barcode reader.
   ZXingBrowserMultiFormatReader? _reader;
 
@@ -164,6 +169,34 @@ final class ZXingBarcodeReader extends BarcodeReader {
   }
 
   @override
+  Future<bool> hasTorch() {
+    final web.MediaStream? mediaStream = _reader?.stream;
+
+    if (mediaStream == null) {
+      return Future<bool>.value(false);
+    }
+
+    return _flashlightDelegate.hasFlashlight(mediaStream);
+  }
+
+  @override
+  Future<void> setTorchState(TorchState value) {
+    switch (value) {
+      case TorchState.unavailable:
+        return Future<void>.value();
+      case TorchState.off:
+      case TorchState.on:
+        final web.MediaStream? mediaStream = _reader?.stream;
+
+        if (mediaStream == null) {
+          return Future<void>.value();
+        }
+
+        return _flashlightDelegate.setFlashlightState(mediaStream, value);
+    }
+  }
+
+  @override
   Future<void> start(StartOptions options, {required web.HTMLElement containerElement}) async {
     final int detectionTimeoutMs = options.detectionTimeoutMs;
     final List<BarcodeFormat> formats = options.formats;