public String[] knownNamespaces() {
   final PsiElement parentElement = getParent();
   BidirectionalMap<String, String> map = initNamespaceMaps(parentElement);
   Set<String> known = Collections.emptySet();
   if (map != null) {
     known = new HashSet<String>(map.values());
   }
   if (parentElement instanceof XmlTag) {
     if (known.isEmpty()) return ((XmlTag) parentElement).knownNamespaces();
     ContainerUtil.addAll(known, ((XmlTag) parentElement).knownNamespaces());
   } else {
     XmlExtension xmlExtension = XmlExtension.getExtensionByElement(this);
     if (xmlExtension != null) {
       final XmlFile xmlFile = xmlExtension.getContainingFile(this);
       if (xmlFile != null) {
         final XmlTag rootTag = xmlFile.getRootTag();
         if (rootTag != null && rootTag != this) {
           if (known.isEmpty()) return rootTag.knownNamespaces();
           ContainerUtil.addAll(known, rootTag.knownNamespaces());
         }
       }
     }
   }
   return ArrayUtil.toStringArray(known);
 }
  private static void fillFromSchema(PsiFile file, ElementNames names) {
    if (!(file instanceof XmlFile)) return;
    final XmlFile f = (XmlFile) file;
    final XmlDocument d = f.getDocument();
    if (d == null) return;
    final XmlTag rootTag = d.getRootTag();
    if (rootTag == null) return;

    //noinspection unchecked
    names.dependencies.add(new NSDeclTracker(rootTag));

    try {
      final Map<String, String> namespaceDeclarations = rootTag.getLocalNamespaceDeclarations();
      final Collection<String> prefixes = namespaceDeclarations.keySet();

      //noinspection unchecked
      final Set<XmlElementDescriptor> history = new THashSet<XmlElementDescriptor>();

      final XmlElementFactory ef = XmlElementFactory.getInstance(file.getProject());
      int noSchemaNamespaces = 0;
      for (String prefix : prefixes) {
        final String namespace = namespaceDeclarations.get(prefix);
        if (isIgnoredNamespace(prefix, namespace)) continue;

        final XmlTag tag =
            ef.createTagFromText("<dummy-tag xmlns='" + namespace + "' />", XMLLanguage.INSTANCE);
        final XmlDocument document = PsiTreeUtil.getParentOfType(tag, XmlDocument.class);
        final XmlNSDescriptor rootDescriptor = tag.getNSDescriptor(tag.getNamespace(), true);
        if (rootDescriptor == null
            || (rootDescriptor instanceof XmlNSDescriptorImpl
                && ((XmlNSDescriptorImpl) rootDescriptor).getTag() == null)
            || !rootDescriptor.getDeclaration().isPhysical()) {
          final QName any = QNameUtil.createAnyLocalName(namespace);
          names.elementNames.add(any);
          names.attributeNames.add(any);
          noSchemaNamespaces++;
          continue;
        }

        //noinspection unchecked
        names.dependencies.add(rootDescriptor.getDescriptorFile());

        final XmlElementDescriptor[] e = rootDescriptor.getRootElementsDescriptors(document);
        for (XmlElementDescriptor descriptor : e) {
          processElementDescriptors(descriptor, tag, names, history);
        }
      }

      names.validateNames = names.elementNames.size() > noSchemaNamespaces;

      //            final QName any = QNameUtil.createAnyLocalName("");
      //            names.elementNames.add(any);
      //            names.attributeNames.add(any);
    } catch (IncorrectOperationException e) {
      Logger.getInstance(XsltContextProvider.class.getName()).error(e);
    }
  }
 @Nullable
 private PsiMetaOwner retrieveOwner(final XmlFile file, final String namespace) {
   if (file == null) {
     return namespace.equals(XmlUtil.getTargetSchemaNsFromTag(this)) ? this : null;
   }
   return file.getDocument();
 }
 @Nullable
 private static XmlNSDescriptor getDtdDescriptor(@NotNull XmlFile containingFile) {
   final XmlDocument document = containingFile.getDocument();
   if (document == null) {
     return null;
   }
   final String url = XmlUtil.getDtdUri(document);
   if (url == null) {
     return null;
   }
   return document.getDefaultNSDescriptor(url, true);
 }
  private static void collectNamesToImport(
      @NotNull final Collection<Pair<String, Boolean>> names,
      @NotNull final Collection<String> demandedForNested,
      @NotNull XmlFile file) {
    file.accept(
        new JavaFxUsedClassesVisitor() {
          @Override
          protected void appendClassName(String fqn) {
            names.add(Pair.create(fqn, false));
          }

          @Override
          protected void appendDemandedPackageName(@NotNull String packageName) {
            demandedForNested.add(packageName);
          }
        });
  }
  @NotNull
  @Override
  public Runnable processFile(final PsiFile file) {
    VirtualFile vFile = file.getVirtualFile();
    if (vFile instanceof VirtualFileWindow) vFile = ((VirtualFileWindow) vFile).getDelegate();
    final Project project = file.getProject();
    if (vFile == null
        || !ProjectRootManager.getInstance(project).getFileIndex().isInSourceContent(vFile)) {
      return EmptyRunnable.INSTANCE;
    }
    final List<Pair<String, Boolean>> names = new ArrayList<Pair<String, Boolean>>();
    final Set<String> demandedForNested = new HashSet<>();
    collectNamesToImport(names, demandedForNested, (XmlFile) file);
    Collections.sort(names, (o1, o2) -> StringUtil.compare(o1.first, o2.first, true));
    final CodeStyleSettings settings = CodeStyleSettingsManager.getSettings(project);
    final List<Pair<String, Boolean>> sortedNames =
        ImportHelper.sortItemsAccordingToSettings(names, settings);
    final HashSet<String> onDemand = new HashSet<String>();
    ImportHelper.collectOnDemandImports(sortedNames, onDemand, settings);
    onDemand.addAll(demandedForNested);
    final Set<String> imported = new HashSet<String>();
    final List<String> imports = new ArrayList<String>();
    for (Pair<String, Boolean> pair : sortedNames) {
      final String qName = pair.first;
      final String packageName = StringUtil.getPackageName(qName);
      if (imported.contains(packageName) || imported.contains(qName)) {
        continue;
      }
      if (onDemand.contains(packageName)) {
        imported.add(packageName);
        imports.add("<?import " + packageName + ".*?>");
      } else {
        imported.add(qName);
        imports.add("<?import " + qName + "?>");
      }
    }
    final PsiFileFactory factory = PsiFileFactory.getInstance(file.getProject());

    final XmlFile dummyFile =
        (XmlFile)
            factory.createFileFromText(
                "_Dummy_.fxml", StdFileTypes.XML, StringUtil.join(imports, "\n"));
    final XmlDocument document = dummyFile.getDocument();
    final XmlProlog newImportList = document != null ? document.getProlog() : null;
    if (newImportList == null) return EmptyRunnable.getInstance();
    return () -> {
      final XmlDocument xmlDocument = ((XmlFile) file).getDocument();
      final XmlProlog prolog = xmlDocument != null ? xmlDocument.getProlog() : null;
      if (prolog != null) {
        final Collection<XmlProcessingInstruction> instructions =
            PsiTreeUtil.findChildrenOfType(prolog, XmlProcessingInstruction.class);
        for (final XmlProcessingInstruction instruction : instructions) {
          final ASTNode node = instruction.getNode();
          final ASTNode nameNode = node.findChildByType(XmlTokenType.XML_NAME);
          if (nameNode != null && nameNode.getText().equals("import")) {
            instruction.delete();
          }
        }
        prolog.add(newImportList);
      } else {
        document.addBefore(newImportList, document.getRootTag());
      }
    };
  }