polkawallet_sdk_fork/lib/service/jaguar_flutter_asset.dart

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

/// Serves static files from Flutter assets.
///
/// Example:
///
///       final server = Jaguar();
///       server.addRoute(serveFlutterAssets());
///       await server.serve();
Route serveFlutterAssets(
    {String path: '*',
    bool stripPrefix: true,
    String prefix: '',
    Map<String, String>? pathRegEx,
    ResponseProcessor? responseProcessor}) {
  Route route;
  int skipCount = -1;
  route = Route.get(path, (ctx) async {
    Iterable<String> segs = ctx.pathSegments;
    if (skipCount > 0) segs = segs.skip(skipCount);

    String lookupPath =
        segs.join('/') + (ctx.path.endsWith('/') ? 'index.html' : '');
    final body = (await rootBundle
            .load('packages/polkawallet_sdk/assets/$prefix$lookupPath'))
        .buffer
        .asUint8List();

    String? mimeType;
    if (!ctx.path.endsWith('/')) {
      if (ctx.pathSegments.isNotEmpty) {
        final String last = ctx.pathSegments.last;
        if (last.contains('.')) {
          mimeType = MimeTypes.fromFileExtension[last.split('.').last];
        }
      }
    } else {
      mimeType = 'text/html';
    }

    ctx.response = ByteResponse(body: body, mimeType: mimeType);
  }, pathRegEx: pathRegEx, responseProcessor: responseProcessor);

  if (stripPrefix) skipCount = route.pathSegments.length - 1;

  return route;
}