reimplement flashlight delegate & use media capabilities which is more supported

+import 'dart:js_interop';
+
+import 'package:mobile_scanner/src/enums/torch_state.dart';
+import 'package:web/web.dart';
+
+/// This class represents a flashlight delegate for the web platform.
+///
+/// It provides an interface to query and update the flashlight state of a [MediaStream].
+final class FlashlightDelegate {
+  /// Returns a list of supported flashlight modes for the given [mediaStream].
+  ///
+  /// The [TorchState.off] mode is always supported, regardless of the return value.
+  Future<List<TorchState>> getSupportedFlashlightModes(MediaStream? mediaStream) async {
+    if (mediaStream == null) {
+      return [];
+    }
+
+    final List<JSAny?> tracks = mediaStream.getVideoTracks().toDart;
+
+    if (tracks.isEmpty) {
+      return [];
+    }
+
+    final MediaStreamTrack? track = tracks.first as MediaStreamTrack?;
+
+    if (track == null) {
+      return [];
+    }
+
+    try {
+      final MediaTrackCapabilities capabilities = track.getCapabilities();
+
+      return [
+        if (capabilities.torch) TorchState.on,
+      ];
+    } catch (_) {
+      // Firefox does not support getCapabilities() yet.
+      // https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamTrack/getCapabilities#browser_compatibility
+
+      return [];
+    }
+  }
+
+  /// Returns whether the given [mediaStream] has a flashlight.
+  Future<bool> hasFlashlight(MediaStream? mediaStream) async {
+    return (await getSupportedFlashlightModes(mediaStream)).isNotEmpty;
+  }
+
+  /// Set the flashlight state of the given [mediaStream] to the given [value].
+  Future<void> setFlashlightState(MediaStream? mediaStream, TorchState value) async {
+    if (mediaStream == null) {
+      return;
+    }
+
+    if (await hasFlashlight(mediaStream)) {
+      final List<JSAny?> tracks = mediaStream.getVideoTracks().toDart;
+
+      if (tracks.isEmpty) {
+        return;
+      }
+
+      final bool flashlightEnabled = switch (value) {
+        TorchState.on => true,
+        TorchState.off || TorchState.unavailable => false,
+      };
+
+      final MediaStreamTrack? track = tracks.first as MediaStreamTrack?;
+
+      final MediaTrackConstraints constraints = MediaTrackConstraints(
+        advanced: [
+          {'torch': flashlightEnabled}.jsify(),
+        ].toJS,
+      );
+
+      await track?.applyConstraints(constraints).toDart;
+    }
+  }
+}