gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/structure/io/graphml/GraphMLWriterHelper.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.tinkerpop.gremlin.structure.io.graphml;

import javax.xml.namespace.NamespaceContext;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;
import java.util.Stack;

/**
 * A wrapper for the different {@code XMLStreamWriter} implementations.
 */
final class GraphMLWriterHelper {

    private GraphMLWriterHelper() {}

    /**
     * @author Tijs Rademakers
     */
    abstract static class DelegatingXMLStreamWriter implements XMLStreamWriter {

        private final XMLStreamWriter writer;

        public DelegatingXMLStreamWriter(XMLStreamWriter writer) {
            this.writer = writer;
        }

        public void writeStartElement(String localName) throws XMLStreamException {
            writer.writeStartElement(localName);
        }

        public void writeStartElement(String namespaceURI, String localName) throws XMLStreamException {
            writer.writeStartElement(namespaceURI, localName);
        }

        public void writeStartElement(String prefix, String localName, String namespaceURI) throws XMLStreamException {
            writer.writeStartElement(prefix, localName, namespaceURI);
        }

        public void writeEmptyElement(String namespaceURI, String localName) throws XMLStreamException {
            writer.writeEmptyElement(namespaceURI, localName);
        }

        public void writeEmptyElement(String prefix, String localName, String namespaceURI) throws XMLStreamException {
            writer.writeEmptyElement(prefix, localName, namespaceURI);
        }

        public void writeEmptyElement(String localName) throws XMLStreamException {
            writer.writeEmptyElement(localName);
        }

        public void writeEndElement() throws XMLStreamException {
            writer.writeEndElement();
        }

        public void writeEndDocument() throws XMLStreamException {
            writer.writeEndDocument();
        }

        public void close() throws XMLStreamException {
            writer.close();
        }

        public void flush() throws XMLStreamException {
            writer.flush();
        }

        public void writeAttribute(String localName, String value) throws XMLStreamException {
            writer.writeAttribute(localName, value);
        }

        public void writeAttribute(String prefix, String namespaceURI, String localName, String value) throws XMLStreamException {
            writer.writeAttribute(prefix, namespaceURI, localName, value);
        }

        public void writeAttribute(String namespaceURI, String localName, String value) throws XMLStreamException {
            writer.writeAttribute(namespaceURI, localName, value);
        }

        public void writeNamespace(String prefix, String namespaceURI) throws XMLStreamException {
            writer.writeNamespace(prefix, namespaceURI);
        }

        public void writeDefaultNamespace(String namespaceURI) throws XMLStreamException {
            writer.writeDefaultNamespace(namespaceURI);
        }

        public void writeComment(String data) throws XMLStreamException {
            writer.writeComment(data);
        }

        public void writeProcessingInstruction(String target) throws XMLStreamException {
            writer.writeProcessingInstruction(target);
        }

        public void writeProcessingInstruction(String target, String data) throws XMLStreamException {
            writer.writeProcessingInstruction(target, data);
        }

        public void writeCData(String data) throws XMLStreamException {
            writer.writeCData(data);
        }

        public void writeDTD(String dtd) throws XMLStreamException {
            writer.writeDTD(dtd);
        }

        public void writeEntityRef(String name) throws XMLStreamException {
            writer.writeEntityRef(name);
        }

        public void writeStartDocument() throws XMLStreamException {
            writer.writeStartDocument();
        }

        public void writeStartDocument(String version) throws XMLStreamException {
            writer.writeStartDocument(version);
        }

        public void writeStartDocument(String encoding, String version) throws XMLStreamException {
            writer.writeStartDocument(encoding, version);
        }

        public void writeCharacters(String text) throws XMLStreamException {
            writer.writeCharacters(text);
        }

        public void writeCharacters(char[] text, int start, int len) throws XMLStreamException {
            writer.writeCharacters(text, start, len);
        }

        public String getPrefix(String uri) throws XMLStreamException {
            return writer.getPrefix(uri);
        }

        public void setPrefix(String prefix, String uri) throws XMLStreamException {
            writer.setPrefix(prefix, uri);
        }

        public void setDefaultNamespace(String uri) throws XMLStreamException {
            writer.setDefaultNamespace(uri);
        }

        public void setNamespaceContext(NamespaceContext context) throws XMLStreamException {
            writer.setNamespaceContext(context);
        }

        public NamespaceContext getNamespaceContext() {
            return writer.getNamespaceContext();
        }

        public Object getProperty(String name) throws IllegalArgumentException {
            return writer.getProperty(name);
        }
    }

    /**
     * @author Tijs Rademakers
     */
    public static class IndentingXMLStreamWriter extends DelegatingXMLStreamWriter {

        private final static Object SEEN_NOTHING = new Object();
        private final static Object SEEN_ELEMENT = new Object();
        private final static Object SEEN_DATA = new Object();

        private Object state = SEEN_NOTHING;
        private Stack<Object> stateStack = new Stack<Object>();

        private String indentStep = "  ";
        private int depth = 0;

        public IndentingXMLStreamWriter(XMLStreamWriter writer) {
            super(writer);
        }

        /**
         * Return the current indent step.
         *
         * <p>
         * Return the current indent step: each start tag will be indented by this
         * number of spaces times the number of ancestors that the element has.
         * </p>
         *
         * @return The number of spaces in each indentation step, or 0 or less for no
         *         indentation.
         * @see #setIndentStep(int)
         *
         * @deprecated Only return the length of the indent string.
         */
        public int getIndentStep() {
            return indentStep.length();
        }

        /**
         * Set the current indent step.
         *
         * @param indentStep
         *          The new indent step (0 or less for no indentation).
         * @see #getIndentStep()
         *
         * @deprecated Should use the version that takes string.
         */
        public void setIndentStep(int indentStep) {
            StringBuilder s = new StringBuilder();
            for (; indentStep > 0; indentStep--)
                s.append(' ');
            this.indentStep = s.toString();
        }

        public void setIndentStep(String s) {
            this.indentStep = s;
        }

        private void onStartElement() throws XMLStreamException {
            stateStack.push(SEEN_ELEMENT);
            state = SEEN_NOTHING;
            if (depth > 0) {
                super.writeCharacters("\n");
            }
            doIndent();
            depth++;
        }

        private void onEndElement() throws XMLStreamException {
            depth--;
            if (state == SEEN_ELEMENT) {
                super.writeCharacters("\n");
                doIndent();
            }
            state = stateStack.pop();
        }

        private void onEmptyElement() throws XMLStreamException {
            state = SEEN_ELEMENT;
            if (depth > 0) {
                super.writeCharacters("\n");
            }
            doIndent();
        }

        /**
         * Print indentation for the current level.
         *
         * @exception org.xml.sax.SAXException
         *              If there is an error writing the indentation characters, or if
         *              a filter further down the chain raises an exception.
         */
        private void doIndent() throws XMLStreamException {
            if (depth > 0) {
                for (int i = 0; i < depth; i++)
                    super.writeCharacters(indentStep);
            }
        }

        public void writeStartDocument() throws XMLStreamException {
            super.writeStartDocument();
            super.writeCharacters("\n");
        }

        public void writeStartDocument(String version) throws XMLStreamException {
            super.writeStartDocument(version);
            super.writeCharacters("\n");
        }

        public void writeStartDocument(String encoding, String version)
                throws XMLStreamException {
            super.writeStartDocument(encoding, version);
            super.writeCharacters("\n");
        }

        public void writeStartElement(String localName) throws XMLStreamException {
            onStartElement();
            super.writeStartElement(localName);
        }

        public void writeStartElement(String namespaceURI, String localName)
                throws XMLStreamException {
            onStartElement();
            super.writeStartElement(namespaceURI, localName);
        }

        public void writeStartElement(String prefix, String localName,
                                      String namespaceURI) throws XMLStreamException {
            onStartElement();
            super.writeStartElement(prefix, localName, namespaceURI);
        }

        public void writeEmptyElement(String namespaceURI, String localName)
                throws XMLStreamException {
            onEmptyElement();
            super.writeEmptyElement(namespaceURI, localName);
        }

        public void writeEmptyElement(String prefix, String localName,
                                      String namespaceURI) throws XMLStreamException {
            onEmptyElement();
            super.writeEmptyElement(prefix, localName, namespaceURI);
        }

        public void writeEmptyElement(String localName) throws XMLStreamException {
            onEmptyElement();
            super.writeEmptyElement(localName);
        }

        public void writeEndElement() throws XMLStreamException {
            onEndElement();
            super.writeEndElement();
        }

        public void writeCharacters(String text) throws XMLStreamException {
            state = SEEN_DATA;
            super.writeCharacters(text);
        }

        public void writeCharacters(char[] text, int start, int len)
                throws XMLStreamException {
            state = SEEN_DATA;
            super.writeCharacters(text, start, len);
        }

        public void writeCData(String data) throws XMLStreamException {
            state = SEEN_DATA;
            super.writeCData(data);
        }

    }
}