@CheckReturnValue
@VisibleForTesting
@SuppressWarnings("WeakerAccess")
static boolean isAvailable(@Nonnull AnActionEvent event) {
    final Project project = event.getProject();
    if (project == null) {
        return false;
    }

    final IdeView view = event.getData(LangDataKeys.IDE_VIEW);
    if (view == null) {
        return false;
    }

    final ProjectRootManager rootManager = ProjectRootManager.getInstance(project);
    final ProjectFileIndex fileIndex = rootManager.getFileIndex();
    final Optional<PsiDirectory> sourceDirectory = Stream.of(view.getDirectories())
            .filter(directory -> {
                final VirtualFile virtualFile = directory.getVirtualFile();
                return fileIndex.isUnderSourceRootOfType(virtualFile, JavaModuleSourceRootTypes.SOURCES);
            })
            .findFirst();
    return sourceDirectory.isPresent();
}
 

/**
 * Checked whether or not this action can be enabled.
 * <p>
 * <p>Requirements to be enabled: * User must be in a Java source folder.
 *
 * @param dataContext to figure out where the user is.
 * @return {@code true} when the action is available, {@code false} when the action is not
 * available.
 */
private boolean isAvailable(DataContext dataContext) {
  final Project project = CommonDataKeys.PROJECT.getData(dataContext);
  if (project == null) {
    return false;
  }

  final IdeView view = LangDataKeys.IDE_VIEW.getData(dataContext);
  if (view == null || view.getDirectories().length == 0) {
    return false;
  }

  ProjectFileIndex projectFileIndex = ProjectRootManager.getInstance(project).getFileIndex();
  for (PsiDirectory dir : view.getDirectories()) {
    if (projectFileIndex.isUnderSourceRootOfType(
        dir.getVirtualFile(), JavaModuleSourceRootTypes.SOURCES)
        && checkPackageExists(dir)) {
      return true;
    }
  }

  return false;
}
 

@Override
public void addCompletions(@NotNull CompletionParameters parameters, @NotNull ProcessingContext context, @NotNull CompletionResultSet resultSet, @NotNull String[] query) {
    Project project = parameters.getOriginalFile().getManager().getProject();

    List<VirtualFile> resourceRoots = ProjectRootManager.getInstance(project).getModuleSourceRoots(JavaModuleSourceRootTypes.PRODUCTION);
    resourceRoots.addAll(ProjectRootManager.getInstance(project).getModuleSourceRoots(JavaModuleSourceRootTypes.TESTS));
    ProjectFileIndex projectFileIndex = ProjectRootManager.getInstance(project).getFileIndex();
    for (final VirtualFile sourceRoot : resourceRoots) {
        if (sourceRoot.isValid() && sourceRoot.getCanonicalFile() != null) {
            VfsUtil.processFilesRecursively(sourceRoot.getCanonicalFile(), virtualFile -> {
                propertyCompletionProviders.stream()
                    .filter(p -> p.isValidExtension(virtualFile.getCanonicalPath()) && !projectFileIndex.isExcluded(sourceRoot))
                    .forEach(p -> p.buildResultSet(resultSet, virtualFile));
                return true;
            });
        }
    }
}