* Copyright (C) 2010-2014 Morgner UG (haftungsbeschränkt)

*

* This file is part of Structr <http://structr.org>.

*

* Structr is free software: you can redistribute it and/or modify

* it under the terms of the GNU Affero General Public License as

* published by the Free Software Foundation, either version 3 of the

* License, or (at your option) any later version.

*

* Structr is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

* GNU General Public License for more details.

*

* You should have received a copy of the GNU Affero General Public License

* along with Structr.  If not, see <http://www.gnu.org/licenses/>.

*/

* Combines AbstractNode and org.w3c.dom.Node.

*

* @author Christian Morgner

*/

  private static final Logger logger = Logger.getLogger(DOMNode.class.getName());

  // ----- error messages for DOMExceptions -----

  protected static final String NO_MODIFICATION_ALLOWED_MESSAGE = "Permission denied.";

  protected static final String INVALID_ACCESS_ERR_MESSAGE = "Permission denied.";

  protected static final String INDEX_SIZE_ERR_MESSAGE = "Index out of range.";

  protected static final String CANNOT_SPLIT_TEXT_WITHOUT_PARENT = "Cannot split text element without parent and/or owner document.";

  protected static final String WRONG_DOCUMENT_ERR_MESSAGE = "Node does not belong to this document.";

  protected static final String HIERARCHY_REQUEST_ERR_MESSAGE_SAME_NODE = "A node cannot accept itself as a child.";

  protected static final String HIERARCHY_REQUEST_ERR_MESSAGE_ANCESTOR = "A node cannot accept its own ancestor as child.";

  protected static final String HIERARCHY_REQUEST_ERR_MESSAGE_DOCUMENT = "A document may only have one html element.";

  protected static final String HIERARCHY_REQUEST_ERR_MESSAGE_ELEMENT = "A document may only accept an html element as its document element.";

  protected static final String NOT_SUPPORTED_ERR_MESSAGE = "Node type not supported.";

  protected static final String NOT_FOUND_ERR_MESSAGE = "Node is not a child.";

  protected static final String NOT_SUPPORTED_ERR_MESSAGE_IMPORT_DOC = "Document nodes cannot be imported into another document.";

  protected static final String NOT_SUPPORTED_ERR_MESSAGE_ADOPT_DOC = "Document nodes cannot be adopted by another document.";

  protected static final String NOT_SUPPORTED_ERR_MESSAGE_RENAME = "Renaming of nodes is not supported by this implementation.";

  private static final List<GraphDataSource<List<GraphObject>>> listSources = new LinkedList<>();

  static {

    // register data sources

    listSources.add(new IdRequestParameterGraphDataSource("nodeId"));

    listSources.add(new RestDataSource());

    listSources.add(new NodeGraphDataSource());

    listSources.add(new FunctionDataSource());

    listSources.add(new CypherGraphDataSource());

    listSources.add(new XPathGraphDataSource());

  }

  public static final Property<String> dataKey          = new StringProperty("dataKey").indexed();

  public static final Property<String> cypherQuery      = new StringProperty("cypherQuery");

  public static final Property<String> xpathQuery       = new StringProperty("xpathQuery");

  public static final Property<String> restQuery        = new StringProperty("restQuery");

  public static final Property<String> functionQuery    = new StringProperty("functionQuery");

  public static final Property<Boolean> renderDetails   = new BooleanProperty("renderDetails");

  public static final Property<List<DOMNode>> syncedNodes = new EndNodes("syncedNodes", Sync.class, new PropertyNotion(id));

  public static final Property<DOMNode> sharedComponent = new StartNode("sharedComponent", Sync.class, new PropertyNotion(id));

  public static final Property<Boolean> hideOnIndex = new BooleanProperty("hideOnIndex").indexed();

  public static final Property<Boolean> hideOnDetail = new BooleanProperty("hideOnDetail").indexed();

  public static final Property<String> showForLocales = new StringProperty("showForLocales").indexed();

  public static final Property<String> hideForLocales = new StringProperty("hideForLocales").indexed();

  public static final Property<String> showConditions = new StringProperty("showConditions").indexed();

  public static final Property<String> hideConditions = new StringProperty("hideConditions").indexed();

  public static final Property<List<DOMNode>> children = new EndNodes<>("children", DOMChildren.class);

  public static final Property<DOMNode> parent = new StartNode<>("parent", DOMChildren.class);

  public static final Property<DOMNode> previousSibling = new StartNode<>("previousSibling", DOMSiblings.class);

  public static final Property<DOMNode> nextSibling = new EndNode<>("nextSibling", DOMSiblings.class);

  public static final Property<List<String>> childrenIds = new CollectionIdProperty("childrenIds", children);

  public static final Property<String> nextSiblingId = new EntityIdProperty("nextSiblingId", nextSibling);

  public static final Property<String> parentId = new EntityIdProperty("parentId", parent);

  public static final Property<Page> ownerDocument = new EndNode<>("ownerDocument", PageLink.class);

  public static final Property<String> pageId = new EntityIdProperty("pageId", ownerDocument);

  public static final Property<String> dataStructrIdProperty = new StringProperty("data-structr-id");

  public static final Property<String> dataHashProperty = new StringProperty("data-hash");

  static {

    // extend set of builtin functions

    Functions.functions.put("render", new Function<Object, Object>() {

      @Override

      public Object apply(final ActionContext ctx, final GraphObject entity, final Object[] sources) throws FrameworkException {

        if (sources != null && sources.length == 1) {

          RenderContext innerCtx = new RenderContext((RenderContext) ctx);

          if (sources[0] instanceof DOMNode) {

            ((DOMNode) sources[0]).render(entity.getSecurityContext(), innerCtx, 0);

          } else if (sources[0] instanceof Collection) {

            for (final Object obj : (Collection) sources[0]) {

              if (obj instanceof DOMNode) {

                ((DOMNode) obj).render(entity.getSecurityContext(), innerCtx, 0);

              }

            }

          }

          return StringUtils.join(innerCtx.getBuffer().getQueue(), "");

        }

        return usage();

      }

      @Override

      public String usage() {

        return "Usage: ${render(node)} or ${render(nodes)}. Example: ${render(get(this, \"children\"))}";

      }

    });

    /**

     * Conveniance method for ${render(find('DOMNode', 'name',

     * name))}

     */

    Functions.functions.put("include", new Function<Object, Object>() {

      @Override

      public Object apply(final ActionContext ctx, final GraphObject entity, final Object[] sources) throws FrameworkException {

        if (Functions.arrayHasLengthAndAllElementsNotNull(sources, 1) && sources[0] instanceof String) {

          final SecurityContext securityContext = entity.getSecurityContext();

          final App app = StructrApp.getInstance(securityContext);

          final RenderContext innerCtx = new RenderContext((RenderContext) ctx);

          final DOMNode node = app.nodeQuery(DOMNode.class).andName((String) sources[0]).getFirst();

          if (node != null) {

            node.render(entity.getSecurityContext(), innerCtx, 0);

          } else {

            final FileBase file = app.nodeQuery(FileBase.class).andName((String) sources[0]).getFirst();

            if (file != null) {

              final String name = file.getProperty(NodeInterface.name);

              final String contentType = file.getProperty(FileBase.contentType);

              final String charset = StringUtils.substringAfterLast(contentType, "charset=");

              final String extension = StringUtils.substringAfterLast(name, ".");

              if (contentType == null || StringUtils.isBlank(extension)) {

                return "No valid file type detected. Please make sure " + name + " has a valid content type set or file extension.";

              }

              if (contentType.startsWith("text/css")) {

                return "<link href=\"" + file.getPath() + "\" rel=\"stylesheet\">";

              } else if (contentType.contains("/javascript")) {

                return "<script src=\"" + file.getPath() + "\"></script>";

              } else if (contentType.startsWith("image/svg")) {

                try {

                  final byte[] buffer = new byte[file.getSize().intValue()];

                  IOUtils.read(file.getInputStream(), buffer);

                  return StringUtils.toEncodedString(buffer, Charset.forName(charset));

                } catch (IOException ex) {

                  logger.log(Level.SEVERE, null, ex);

                }

                return "<img alt=\"" + name + "\" src=\"" + file.getPath() + "\">";

              } else if (contentType.startsWith("image/")) {

                return "<img alt=\"" + name + "\" src=\"" + file.getPath() + "\">";

              } else {

                return "Don't know how to render content type or extension of  " + name + ".";

              }

            }

          }

          return StringUtils.join(innerCtx.getBuffer().getQueue(), "");

        }

        return usage();

      }

      @Override

      public String usage() {

        return "Usage: ${include(name)}. Example: ${include(\"Main Template\")}";

      }

    });

    Functions.functions.put("strip_html", new Function<Object, Object>() {

      @Override

      public Object apply(final ActionContext ctx, final GraphObject entity, final Object[] sources) throws FrameworkException {

        return (Functions.arrayHasMinLengthAndAllElementsNotNull(sources, 1))

          ? sources[0].toString().replaceAll("\\<.*?>","")

          : "";

      }

      @Override

      public String usage() {

        return "Usage: ${strip_html(html)}. Example: ${strip_html(\"<p>foo</p>\")}";

      }

    });

    Functions.functions.put("GET", new Function<Object, Object>() {

      @Override

      public Object apply(ActionContext ctx, final GraphObject entity, final Object[] sources) {

        if (sources != null && sources.length > 0) {

          try {

            String address = sources[0].toString();

            String contentType = null;

            if (sources.length > 1) {

              contentType = sources[1].toString();

            }

            //long t0 = System.currentTimeMillis();

            if ("text/html".equals(contentType)) {

              String selector = null;

              if (sources.length > 2) {

                selector = sources[2].toString();

                String html = Jsoup.parse(new URL(address), 5000).select(selector).html();

                return html;

              } else {

                String html = Jsoup.parse(new URL(address), 5000).html();

                //logger.log(Level.INFO, "Jsoup took {0} ms to get and parse page.", (System.currentTimeMillis() - t0));

                return html;

              }

            } else {

              return getFromUrl(address);

            }

          } catch (Throwable t) {

          }

          return "";

        }

        return usage();

      }

      @Override

      public String usage() {

        return "Usage: ${GET(URL[, contentType[, selector]])}. Example: ${GET('http://structr.org', 'text/html')}";

      }

    });

    Functions.functions.put("parse", new Function<Object, Object>() {

      @Override

      public Object apply(ActionContext ctx, final GraphObject entity, final Object[] sources) {

        if (sources != null && sources.length > 1) {

          try {

            final String source                     = sources[0].toString();

            final String selector                   = sources[1].toString();

            final List<Map<String, Object>> objects = new MicroformatParser().parse(source, selector);

            final List<GraphObjectMap> elements     = new LinkedList<>();

            for (final Map<String, Object> map : objects) {

              final GraphObjectMap obj = new GraphObjectMap();

              elements.add(obj);

              Functions.recursivelyConvertMapToGraphObjectMap(obj, map, 0);

            }

            return elements;

          } catch (Throwable t) {

            t.printStackTrace();

          }

          return "";

        }

        return usage();

      }

      @Override

      public String usage() {

        return "Usage: ${parse(URL, selector)}. Example: ${parse('http://structr.org', 'li.data')}";

      }

    });

    Functions.functions.put("to_json", new Function<Object, Object>() {

      @Override

      public Object apply(ActionContext ctx, final GraphObject entity, final Object[] sources) {

        if (sources != null && sources.length > 0 && sources[0] instanceof GraphObject) {

          final SecurityContext securityContext = entity.getSecurityContext();

          try {

            final Value<String> view = new StaticValue<>("public");

            if (sources.length > 1) {

              view.set(securityContext, sources[1].toString());

            }

            int outputDepth = 3;

            if (sources.length > 2) {

              if (sources[2] instanceof Number) {

                outputDepth = ((Number)sources[2]).intValue();

              }

            }

            final StreamingJsonWriter jsonStreamer = new StreamingJsonWriter(view, true, outputDepth);

            final StringWriter writer              = new StringWriter();

            jsonStreamer.streamSingle(securityContext, writer, (GraphObject)sources[0]);

            return writer.getBuffer().toString();

          } catch (Throwable t) {

            t.printStackTrace();

          }

          return "";

        }

        return usage();

      }

      @Override

      public String usage() {

        return "Usage: ${to_json(obj [, view])}. Example: ${to_json(this)}";

      }

    });

    Functions.functions.put("from_json", new Function<Object, Object>() {

      @Override

      public Object apply(ActionContext ctx, final GraphObject entity, final Object[] sources) {

        if (sources != null && sources.length > 0) {

          try {

            final List<GraphObjectMap> elements     = new LinkedList<>();

            final String source                     = sources[0].toString();

            final Gson gson                         = new GsonBuilder().create();

            List<Map<String, Object>> objects       = new LinkedList<>();

            if (StringUtils.startsWith(source, "[")) {

              final List<Map<String, Object>> list = gson.fromJson(source, new TypeToken<List<Map<String, Object>>>() {}.getType());

              if (list != null) {

                objects.addAll(list);

              }

            } else if (StringUtils.startsWith(source, "{")) {

              final Map<String, Object> value = gson.fromJson(source, new TypeToken<Map<String, Object>>() {}.getType());

              if (value != null) {

                objects.add(value);

              }

            }

            for (final Map<String, Object> map : objects) {

              final GraphObjectMap obj = new GraphObjectMap();

              elements.add(obj);

              Functions.recursivelyConvertMapToGraphObjectMap(obj, map, 0);

            }

            return elements;

          } catch (Throwable t) {

            t.printStackTrace();

          }

          return "";

        }

        return usage();

      }

      @Override

      public String usage() {

        return "Usage: ${from_json(src)}. Example: ${from_json('{name:test}')}";

      }

    });

  }

  public abstract boolean isSynced();

  public abstract boolean contentEquals(final DOMNode otherNode);

  public abstract void updateFromNode(final DOMNode otherNode) throws FrameworkException;

  public String getIdHash() {

    final String uuid = getUuid();

    return Integer.toHexString(uuid.hashCode());

  }

  public String getIdHashOrProperty() {

    String idHash = getProperty(DOMNode.dataHashProperty);

    if (idHash == null) {

      idHash = getIdHash();

    }

    return idHash;

  }

  /**

   * This method will be called by the DOM logic when this node gets a new

   * child. Override this method if you need to set properties on the

   * child depending on its type etc.

   *

   * @param newChild

   */

  protected void handleNewChild(Node newChild) {

    final Page page = (Page) getOwnerDocument();

    for (final DOMNode child : getAllChildNodes()) {

      try {

        child.setProperty(ownerDocument, page);

      } catch (FrameworkException ex) {

        ex.printStackTrace();

      }

    }

  }

  @Override

  public Class<DOMChildren> getChildLinkType() {

    return DOMChildren.class;

  }

  @Override

  public Class<DOMSiblings> getSiblingLinkType() {

    return DOMSiblings.class;

  }

  // ----- public methods -----

  @Override

  public String toString() {

    return getClass().getSimpleName() + " [" + getUuid() + "] (" + getTextContent() + ", " + treeGetChildPosition(this) + ")";

  }

  public List<DOMChildren> getChildRelationships() {

    return treeGetChildRelationships();

  }

  public String getPositionPath() {

    String path = "";

    DOMNode currentNode = this;

    while (currentNode.getParentNode() != null) {

      DOMNode parentNode = (DOMNode) currentNode.getParentNode();

      path = "/" + parentNode.treeGetChildPosition(currentNode) + path;

      currentNode = parentNode;

    }

    return path;

  }

  @Override

  public boolean onModification(SecurityContext securityContext, ErrorBuffer errorBuffer) throws FrameworkException {

    try {

      increasePageVersion();

    } catch (FrameworkException ex) {

      logger.log(Level.WARNING, "Updating page version failed", ex);

    }

    return isValid(errorBuffer);

  }

  /**

   * Render the node including data binding (outer rendering).

   *

   * @param securityContext

   * @param renderContext

   * @param depth

   * @throws FrameworkException

   */

  @Override

  public void render(final SecurityContext securityContext, final RenderContext renderContext, final int depth) throws FrameworkException {

    if (!securityContext.isVisible(this)) {

      return;

    }

    final GraphObject details = renderContext.getDetailsDataObject();

    final boolean detailMode = details != null;

    if (detailMode && getProperty(hideOnDetail)) {

      return;

    }

    if (!detailMode && getProperty(hideOnIndex)) {

      return;

    }

    final EditMode editMode  = renderContext.getEditMode(securityContext.getUser(false));

    if (EditMode.RAW.equals(editMode) || EditMode.WIDGET.equals(editMode)) {

      renderContent(securityContext, renderContext, depth);

    } else {

      final String subKey = getProperty(dataKey);

      if (StringUtils.isNotBlank(subKey)) {

        setDataRoot(renderContext, this, subKey);

        final GraphObject currentDataNode = renderContext.getDataObject();

        // fetch (optional) list of external data elements

        final List<GraphObject> listData = checkListSources(securityContext, renderContext);

        final PropertyKey propertyKey;

        if (getProperty(renderDetails) && detailMode) {

          renderContext.setDataObject(details);

          renderContext.putDataObject(subKey, details);

          renderContent(securityContext, renderContext, depth);

        } else {

          if (listData.isEmpty() && currentDataNode != null) {

          // There are two alternative ways of retrieving sub elements:

            // First try to get generic properties,

            // if that fails, try to create a propertyKey for the subKey

            final Object elements = currentDataNode.getProperty(new GenericProperty(subKey));

            renderContext.setRelatedProperty(new GenericProperty(subKey));

            renderContext.setSourceDataObject(currentDataNode);

            if (elements != null) {

              if (elements instanceof Iterable) {

                for (Object o : (Iterable) elements) {

                  if (o instanceof GraphObject) {

                    GraphObject graphObject = (GraphObject) o;

                    renderContext.putDataObject(subKey, graphObject);

                    renderContent(securityContext, renderContext, depth);

                  }

                }

              }

            } else {

              propertyKey = StructrApp.getConfiguration().getPropertyKeyForJSONName(currentDataNode.getClass(), subKey, false);

              renderContext.setRelatedProperty(propertyKey);

              if (propertyKey != null) {

                final Object value = currentDataNode.getProperty(propertyKey);

                if (value != null) {

                  if (value instanceof Iterable) {

                    for (final Object o : ((Iterable) value)) {

                      if (o instanceof GraphObject) {

                        renderContext.putDataObject(subKey, (GraphObject) o);

                        renderContent(securityContext, renderContext, depth);

                      }

                    }

                  }

                }

              }

            }

            // reset data node in render context

            renderContext.setDataObject(currentDataNode);

            renderContext.setRelatedProperty(null);

          } else {

            renderContext.setListSource(listData);

            renderNodeList(securityContext, renderContext, depth, subKey);

          }

        }

      } else {

        renderContent(securityContext, renderContext, depth);

      }

    }

  }

  public Template getClosestTemplate(final Page page) {

    DOMNode node = this;

    while (node != null) {

      if (node instanceof Template) {

        final Template template = (Template) node;

        Document doc = template.getOwnerDocument();

        if (doc == null) {

          doc = node.getClosestPage();

        }

        if (doc != null && (page == null || doc.equals(page))) {

          try {

            template.setProperty(DOMNode.ownerDocument, (Page) doc);

            return template;

          } catch (FrameworkException ex) {

            ex.printStackTrace();

          }

        }

        final List<DOMNode> _syncedNodes = template.getProperty(DOMNode.syncedNodes);

        for (final DOMNode syncedNode : _syncedNodes) {

          doc = syncedNode.getOwnerDocument();

          if (doc != null && (page == null || doc.equals(page))) {

            return (Template) syncedNode;

          }

        }

      }

      node = (DOMNode) node.getParentNode();

    }

    return null;

  }

  public Page getClosestPage() {

    DOMNode node = this;

    while (node != null) {

      if (node instanceof Page) {

        return (Page) node;

      }

      node = (DOMNode) node.getParentNode();

    }

    return null;

  }

  // ----- private methods -----

  /**

   * Get all ancestors of this node

   *

   * @return list of ancestors

   */

  private List<Node> getAncestors() {

    List<Node> ancestors = new LinkedList();

    Node _parent = getParentNode();

    while (_parent != null) {

      ancestors.add(_parent);

      _parent = _parent.getParentNode();

    }

    return ancestors;

  }

  // ----- protected methods -----

  protected void setDataRoot(final RenderContext renderContext, final AbstractNode node, final String dataKey) {

    // an outgoing RENDER_NODE relationship points to the data node where rendering starts

    for (RenderNode rel : node.getOutgoingRelationships(RenderNode.class)) {

      NodeInterface dataRoot = rel.getTargetNode();

      // set start node of this rendering to the data root node

      renderContext.putDataObject(dataKey, dataRoot);

      // allow only one data tree to be rendered for now

      break;

    }

  }

  protected void renderNodeList(SecurityContext securityContext, RenderContext renderContext, int depth, String dataKey) throws FrameworkException {

    Iterable<GraphObject> listSource = renderContext.getListSource();

    if (listSource != null) {

      for (GraphObject dataObject : listSource) {

        // make current data object available in renderContext

        renderContext.putDataObject(dataKey, dataObject);

        renderContent(securityContext, renderContext, depth + 1);

      }

      renderContext.clearDataObject(dataKey);

    }

  }

  protected void migrateSyncRels() {

    try {

      org.neo4j.graphdb.Node n = getNode();

      Iterable<Relationship> incomingSyncRels = n.getRelationships(DynamicRelationshipType.withName("SYNC"), Direction.INCOMING);

      Iterable<Relationship> outgoingSyncRels = n.getRelationships(DynamicRelationshipType.withName("SYNC"), Direction.OUTGOING);

      if (getOwnerDocument() instanceof ShadowDocument) {

        // We are a shared component and must not have any incoming SYNC rels

        for (Relationship r : incomingSyncRels) {

          r.delete();

        }

      } else {

        for (Relationship r : outgoingSyncRels) {

          r.delete();

        }

        for (Relationship r : incomingSyncRels) {

          DOMElement possibleSharedComp = StructrApp.getInstance().get(DOMElement.class, (String) r.getStartNode().getProperty("id"));

          if (!(possibleSharedComp.getOwnerDocument() instanceof ShadowDocument)) {

            r.delete();

          }

        }

      }

    } catch (FrameworkException ex) {

      Logger.getLogger(DOMElement.class.getName()).log(Level.SEVERE, null, ex);

    }

  }

  protected List<GraphObject> checkListSources(final SecurityContext securityContext, final RenderContext renderContext) {

    // try registered data sources first

    for (GraphDataSource<List<GraphObject>> source : listSources) {

      try {

        List<GraphObject> graphData = source.getData(securityContext, renderContext, this);

        if (graphData != null && !graphData.isEmpty()) {

          return graphData;

        }

      } catch (FrameworkException fex) {

        fex.printStackTrace();

        logger.log(Level.WARNING, "Could not retrieve data from graph data source {0}: {1}", new Object[]{source, fex});

      }

    }

    return Collections.EMPTY_LIST;

  }

  /**

   * Increase version of the page.

   *

   * A {@link Page} is a {@link DOMNode} as well, so we have to check

   * 'this' as well.

   *

   * @throws FrameworkException

   */

  protected void increasePageVersion() throws FrameworkException {

    Page page = null;

    if (this instanceof Page) {

      page = (Page) this;

    } else {

      // ignore page-less nodes

      if (getProperty(DOMNode.parent) == null) {

        return;

      }

    }

    if (page == null) {

      final List<Node> ancestors = getAncestors();

      if (!ancestors.isEmpty()) {

        final DOMNode rootNode = (DOMNode) ancestors.get(ancestors.size() - 1);

        if (rootNode instanceof Page) {

          page = (Page) rootNode;

        } else {

          rootNode.increasePageVersion();

        }

      } else {

        final List<DOMNode> _syncedNodes = getProperty(DOMNode.syncedNodes);

        for (final DOMNode syncedNode : _syncedNodes) {

          syncedNode.increasePageVersion();

        }

      }

    }

    if (page != null) {

      page.unlockReadOnlyPropertiesOnce();

      page.increaseVersion();

    }

  }

  protected boolean avoidWhitespace() {

    return false;

  }

  protected void checkIsChild(Node otherNode) throws DOMException {

    if (otherNode instanceof DOMNode) {

      Node _parent = otherNode.getParentNode();

      if (!isSameNode(_parent)) {

        throw new DOMException(DOMException.NOT_FOUND_ERR, NOT_FOUND_ERR_MESSAGE);

      }

      // validation successful

      return;

    }

    throw new DOMException(DOMException.NOT_SUPPORTED_ERR, NOT_SUPPORTED_ERR_MESSAGE);

  }

  protected void checkHierarchy(Node otherNode) throws DOMException {

    // we can only check DOMNodes

    if (otherNode instanceof DOMNode) {

      // verify that the other node is not this node

      if (isSameNode(otherNode)) {

        throw new DOMException(DOMException.HIERARCHY_REQUEST_ERR, HIERARCHY_REQUEST_ERR_MESSAGE_SAME_NODE);

      }

      // verify that otherNode is not one of the

      // the ancestors of this node

      // (prevent circular relationships)

      Node _parent = getParentNode();

      while (_parent != null) {

        if (_parent.isSameNode(otherNode)) {

          throw new DOMException(DOMException.HIERARCHY_REQUEST_ERR, HIERARCHY_REQUEST_ERR_MESSAGE_ANCESTOR);

        }

        _parent = _parent.getParentNode();

      }

      // TODO: check hierarchy constraints imposed by the schema

      // validation sucessful

      return;

    }

    throw new DOMException(DOMException.NOT_SUPPORTED_ERR, NOT_SUPPORTED_ERR_MESSAGE);

  }

  protected void checkSameDocument(Node otherNode) throws DOMException {

    Document doc = getOwnerDocument();

    if (doc != null) {

      Document otherDoc = otherNode.getOwnerDocument();

      // Shadow doc is neutral

      if (otherDoc != null && !doc.equals(otherDoc) && !(doc instanceof ShadowDocument)) {

        throw new DOMException(DOMException.WRONG_DOCUMENT_ERR, WRONG_DOCUMENT_ERR_MESSAGE);

      }

      if (otherDoc == null) {

        ((DOMNode) otherNode).doAdopt((Page) doc);

      }

    }

  }

  protected void checkWriteAccess() throws DOMException {

    if (!securityContext.isAllowed(this, Permission.write)) {

      throw new DOMException(DOMException.NO_MODIFICATION_ALLOWED_ERR, NO_MODIFICATION_ALLOWED_MESSAGE);

    }

  }

  protected void checkReadAccess() throws DOMException {

    if (securityContext.isVisible(this) || securityContext.isAllowed(this, Permission.read)) {

      return;

    }

    throw new DOMException(DOMException.INVALID_ACCESS_ERR, INVALID_ACCESS_ERR_MESSAGE);

  }

  protected String indent(final int depth) {