packages/file_selector/file_selector_web/lib/src/utils.dart

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';

/// Convert list of XTypeGroups to a comma-separated string
String acceptedTypesToString(List<XTypeGroup>? acceptedTypes) {
  if (acceptedTypes == null) {
    return '';
  }
  final List<String> allTypes = <String>[];
  for (final XTypeGroup group in acceptedTypes) {
    _assertTypeGroupIsValid(group);
    if (group.extensions != null) {
      allTypes.addAll(group.extensions!.map(_normalizeExtension));
    }
    if (group.mimeTypes != null) {
      allTypes.addAll(group.mimeTypes!);
    }
    if (group.webWildCards != null) {
      allTypes.addAll(group.webWildCards!);
    }
  }
  return allTypes.join(',');
}

/// Make sure that at least one of its fields is populated.
void _assertTypeGroupIsValid(XTypeGroup group) {
  assert(
      !((group.extensions == null || group.extensions!.isEmpty) &&
          (group.mimeTypes == null || group.mimeTypes!.isEmpty) &&
          (group.webWildCards == null || group.webWildCards!.isEmpty)),
      'At least one of extensions / mimeTypes / webWildCards is required for web.');
}

/// Append a dot at the beggining if it is not there png -> .png
String _normalizeExtension(String ext) {
  return ext.isNotEmpty && ext[0] != '.' ? '.$ext' : ext;
}