nc-photos/lib/use_case/update_dynamic_album_cover.dart

import 'package:nc_photos/entity/album.dart';
import 'package:nc_photos/entity/album/cover_provider.dart';
import 'package:nc_photos/entity/album/item.dart';
import 'package:nc_photos/entity/album/provider.dart';
import 'package:nc_photos/entity/file.dart';
import 'package:nc_photos/entity/file_util.dart' as file_util;
import 'package:nc_photos/iterable_extension.dart';

class UpdateDynamicAlbumCover {
  /// Update the cover of a dynamic album with unsorted items
  ///
  /// If no updates are needed, return the same object
  Album call(Album album, List<AlbumItem> populatedItems) {
    if (album.provider is! AlbumDynamicProvider ||
        album.coverProvider is! AlbumAutoCoverProvider) {
      return album;
    } else {
      return _updateWithSortedFiles(
          album,
          populatedItems
              .whereType<AlbumFileItem>()
              .map((e) => e.file)
              .where((element) => file_util.isSupportedFormat(element))
              .sorted(compareFileDateTimeDescending));
    }
  }

  /// Update the cover of a dynamic album with pre-sorted files
  ///
  /// The album items are expected to be sorted by
  /// [compareFileDateTimeDescending], otherwise please call the unsorted
  /// version. If no updates are needed, return the same object
  Album updateWithSortedFiles(Album album, List<File> sortedFiles) {
    if (album.provider is! AlbumDynamicProvider ||
        album.coverProvider is! AlbumAutoCoverProvider) {
      return album;
    } else {
      return _updateWithSortedFiles(album, sortedFiles);
    }
  }

  Album _updateWithSortedFiles(Album album, List<File> sortedFiles) {
    try {
      final coverFile =
          sortedFiles.firstWhere((element) => element.hasPreview ?? false);
      // cache the result for later use
      if (coverFile.path !=
          (album.coverProvider as AlbumAutoCoverProvider).coverFile?.path) {
        return album.copyWith(
          coverProvider: AlbumAutoCoverProvider(
            coverFile: coverFile,
          ),
        );
      }
    } on StateError catch (_) {
      // no files
    }
    return album;
  }
}