intersection method

Set<String> intersection(FileCollection other)

Compute the intersection between this collection and another.

The result is a Set of all paths that, in theory, could contain overlapping files or directories, taking into consideration all settings of this and the other collection.

Notice that this operation does not require looking at the file system.

Implementation

Set<String> intersection(FileCollection other) {
  final otherDirsInDirs = directories
      .expand((d) => other.directories.where((od) =>
          d.isWithin(od.path, isDir: true) &&
          (od.fileExtensions.isEmpty ||
              od.fileExtensions.intersection(d.fileExtensions).isNotEmpty)))
      .map((e) => e.path);
  final dirsInOtherDirs = other.directories
      .expand((od) => directories.where((d) =>
          od.isWithin(d.path, isDir: true) &&
          (d.fileExtensions.isEmpty ||
              d.fileExtensions.intersection(od.fileExtensions).isNotEmpty)))
      .map((e) => e.path);
  final filesInOtherDirs = other.directories
      .expand((d) => files.where((f) => d.isWithin(f, isDir: false)));
  final otherFilesInDirs = directories
      .expand((d) => other.files.where((f) => d.isWithin(f, isDir: false)));
  final filesIntersection = files
      .where((f) => other.includesFile(f))
      .toSet()
      .intersection(other.files.where((f) => includesFile(f)).toSet());

  // all files must be acceptable by all collection's filters now
  final filters = directories
      .followedBy(other.directories)
      .where((d) => d.fileExtensions.isNotEmpty)
      .map((d) => d.fileExtensions);

  bool Function(String) filter;
  if (filters.isNotEmpty) {
    final extensions = filters.fold(
        filters.first, (Set<String> a, Set<String> b) => a.intersection(b));
    filter = (s) => extensions.any(s.endsWith);
  } else {
    filter = (s) => true;
  }

  return filesIntersection
      .followedBy(filesInOtherDirs)
      .followedBy(otherFilesInDirs)
      .where(filter)
      .followedBy(otherDirsInDirs)
      .followedBy(dirsInOtherDirs)
      .toSet();
}