Copyright (c) 2000, 2018 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.internal.core;


import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.eclipse.debug.core.DebugPlugin;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

An XML memento. Copied from workspace plug-in.
/**
 * An XML memento. Copied from workspace plug-in.
 */
public final class XMLMemento {
	private Document factory;

	private Element element;

	
Creates a Document from the Reader
and returns a memento on the first Element for reading
the document.

Same as calling createReadRoot(reader, null)

Params:
reader – the Reader used to create the memento's document
Throws:
Exception – if IO problems, invalid format, or no element.
Returns:
a memento on the first Element for reading the document/**
	 * Creates a <code>Document</code> from the <code>Reader</code>
	 * and returns a memento on the first <code>Element</code> for reading
	 * the document.
	 * <p>
	 * Same as calling createReadRoot(reader, null)
	 * </p>
	 *
	 * @param reader the <code>Reader</code> used to create the memento's document
	 * @return a memento on the first <code>Element</code> for reading the document
	 * @throws Exception if IO problems, invalid format, or no element.
	 */
	public static XMLMemento createReadRoot(Reader reader)
			throws Exception {
		return createReadRoot(reader, null);
	}

	
Creates a Document from the Reader
and returns a memento on the first Element for reading
the document.
Params:
reader – the Reader used to create the memento's document
baseDir – the directory used to resolve relative file names
		in the XML document. This directory must exist and include the
		trailing separator. The directory format, including the separators,
		must be valid for the platform. Can be null if not
		needed.
Throws:
Exception – if IO problems, invalid format, or no element.
Returns:
a memento on the first Element for reading the document/**
	 * Creates a <code>Document</code> from the <code>Reader</code>
	 * and returns a memento on the first <code>Element</code> for reading
	 * the document.
	 *
	 * @param reader the <code>Reader</code> used to create the memento's document
	 * @param baseDir the directory used to resolve relative file names
	 * 		in the XML document. This directory must exist and include the
	 * 		trailing separator. The directory format, including the separators,
	 * 		must be valid for the platform. Can be <code>null</code> if not
	 * 		needed.
	 * @return a memento on the first <code>Element</code> for reading the document
	 * @throws Exception if IO problems, invalid format, or no element.
	 */
	public static XMLMemento createReadRoot(Reader reader, String baseDir)
			throws Exception {
		String errorMessage = null;
		Exception exception = null;

		try {
			DocumentBuilderFactory factory = DocumentBuilderFactory
					.newInstance();
			DocumentBuilder parser = factory.newDocumentBuilder();
			InputSource source = new InputSource(reader);
			if (baseDir != null) {
				source.setSystemId(baseDir);
			}
			Document document = parser.parse(source);
			NodeList list = document.getChildNodes();
			for (int i = 0; i < list.getLength(); i++) {
				Node node = list.item(i);
				if (node instanceof Element) {
					return new XMLMemento(document, (Element) node);
				}
			}
		} catch (ParserConfigurationException e) {
			exception = e;
			// errorMessage = WorkbenchMessages.XMLMemento_parserConfigError;
		} catch (IOException e) {
			exception = e;
			// errorMessage = WorkbenchMessages.XMLMemento_ioError;
		} catch (SAXException e) {
			exception = e;
			// errorMessage = WorkbenchMessages.XMLMemento_formatError;
		}

		String problemText = null;
		if (exception != null) {
			problemText = exception.getMessage();
		}
		if (problemText == null || problemText.length() == 0) {
			problemText = errorMessage != null ? errorMessage
					:"ERROR"; //;WorkbenchMessages.XMLMemento_noElement; //$NON-NLS-1$
		}
		throw new Exception(problemText, exception);
	}

	
Returns a root memento for writing a document.
Params:
type – the element node type to create on the document
Returns:
the root memento for writing a document/**
	 * Returns a root memento for writing a document.
	 *
	 * @param type the element node type to create on the document
	 * @return the root memento for writing a document
	 */
	public static XMLMemento createWriteRoot(String type) {
		Document document;
		try {
			document = DocumentBuilderFactory.newInstance()
					.newDocumentBuilder().newDocument();
			Element element = document.createElement(type);
			document.appendChild(element);
			return new XMLMemento(document, element);
		} catch (ParserConfigurationException e) {
//            throw new Error(e);
			throw new Error(e.getMessage());
		}
	}

	
Creates a memento for the specified document and element.

Clients should use createReadRoot and
createWriteRoot to create the initial
memento on a document.

Params:
document – the document for the memento
element – the element node for the memento/**
	 * Creates a memento for the specified document and element.
	 * <p>
	 * Clients should use <code>createReadRoot</code> and
	 * <code>createWriteRoot</code> to create the initial
	 * memento on a document.
	 * </p>
	 *
	 * @param document the document for the memento
	 * @param element the element node for the memento
	 */
	public XMLMemento(Document document, Element element) {
		super();
		this.factory = document;
		this.element = element;
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public XMLMemento createChild(String type) {
		Element child = factory.createElement(type);
		element.appendChild(child);
		return new XMLMemento(factory, child);
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public XMLMemento createChild(String type, String id) {
		Element child = factory.createElement(type);
		child.setAttribute(IMementoConstants.TAG_ID, id == null ? "" : id); //$NON-NLS-1$
		element.appendChild(child);
		return new XMLMemento(factory, child);
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public XMLMemento copyChild(XMLMemento child) {
		Element childElement = child.element;
		Element newElement = (Element) factory.importNode(childElement, true);
		element.appendChild(newElement);
		return new XMLMemento(factory, newElement);
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public XMLMemento getChild(String type) {

		// Get the nodes.
		NodeList nodes = element.getChildNodes();
		int size = nodes.getLength();
		if (size == 0) {
			return null;
		}

		// Find the first node which is a child of this node.
		for (int nX = 0; nX < size; nX++) {
			Node node = nodes.item(nX);
			if (node instanceof Element) {
				Element element1 = (Element) node;
				if (element1.getNodeName().equals(type)) {
					return new XMLMemento(factory, element1);
				}
			}
		}

		// A child was not found.
		return null;
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public XMLMemento[] getChildren(String type) {

		// Get the nodes.
		NodeList nodes = element.getChildNodes();
		int size = nodes.getLength();
		if (size == 0) {
			return new XMLMemento[0];
		}

		// Extract each node with given type.
		ArrayList<Element> list = new ArrayList<>(size);
		for (int nX = 0; nX < size; nX++) {
			Node node = nodes.item(nX);
			if (node instanceof Element) {
				Element element1 = (Element) node;
				if (element1.getNodeName().equals(type)) {
					list.add(element1);
				}
			}
		}

		// Create a memento for each node.
		size = list.size();
		XMLMemento[] results = new XMLMemento[size];
		for (int x = 0; x < size; x++) {
			results[x] = new XMLMemento(factory, list.get(x));
		}
		return results;
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public Float getFloat(String key) {
		Attr attr = element.getAttributeNode(key);
		if (attr == null) {
			return null;
		}
		String strValue = attr.getValue();
		try {
			return Float.valueOf(strValue);
		} catch (NumberFormatException e) {
			DebugPlugin.logMessage("Memento problem - Invalid float for key: " //$NON-NLS-1$
					+ key + " value: " + strValue, e); //$NON-NLS-1$
			return null;
		}
	}

	public String getType() {
		return element.getNodeName();
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public String getID() {
		return element.getAttribute(IMementoConstants.TAG_ID);
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public Integer getInteger(String key) {
		Attr attr = element.getAttributeNode(key);
		if (attr == null) {
			return null;
		}
		String strValue = attr.getValue();
		try {
			return Integer.valueOf(strValue);
		} catch (NumberFormatException e) {
			DebugPlugin
					.logMessage("Memento problem - invalid integer for key: " + key //$NON-NLS-1$
							+ " value: " + strValue, e); //$NON-NLS-1$
			return null;
		}
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public String getString(String key) {
		Attr attr = element.getAttributeNode(key);
		if (attr == null) {
			return null;
		}
		return attr.getValue();
	}

	public Boolean getBoolean(String key) {
		Attr attr = element.getAttributeNode(key);
		if (attr == null) {
			return null;
		}
		return Boolean.valueOf(attr.getValue());
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public String getTextData() {
		Text textNode = getTextNode();
		if (textNode != null) {
			return textNode.getData();
		}
		return null;
	}

	public String[] getAttributeKeys() {
		NamedNodeMap map = element.getAttributes();
		int size = map.getLength();
		String[] attributes = new String[size];
		for (int i = 0; i < size; i++) {
			Node node = map.item(i);
			attributes[i] = node.getNodeName();
		}
		return attributes;
	}

	
Returns the Text node of the memento. Each memento is allowed only
one Text node.
Returns:
the Text node of the memento, or null if
the memento has no Text node./**
	 * Returns the Text node of the memento. Each memento is allowed only
	 * one Text node.
	 *
	 * @return the Text node of the memento, or <code>null</code> if
	 * the memento has no Text node.
	 */
	private Text getTextNode() {
		// Get the nodes.
		NodeList nodes = element.getChildNodes();
		int size = nodes.getLength();
		if (size == 0) {
			return null;
		}
		for (int nX = 0; nX < size; nX++) {
			Node node = nodes.item(nX);
			if (node instanceof Text) {
				return (Text) node;
			}
		}
		// a Text node was not found
		return null;
	}

	
Places the element's attributes into the document.
Params:
element1 – the element
copyText – true if the first text node should be copied/**
	 * Places the element's attributes into the document.
	 * @param element1 the element
	 * @param copyText true if the first text node should be copied
	 */
	private void putElement(Element element1, boolean copyText) {
		NamedNodeMap nodeMap = element1.getAttributes();
		int size = nodeMap.getLength();
		for (int i = 0; i < size; i++) {
			Attr attr = (Attr) nodeMap.item(i);
			putString(attr.getName(), attr.getValue());
		}

		NodeList nodes = element1.getChildNodes();
		size = nodes.getLength();
		// Copy first text node (fixes bug 113659).
		// Note that text data will be added as the first child (see putTextData)
		boolean needToCopyText = copyText;
		for (int i = 0; i < size; i++) {
			Node node = nodes.item(i);
			if (node instanceof Element) {
				XMLMemento child = createChild(node.getNodeName());
				child.putElement((Element) node, true);
			} else if (node instanceof Text && needToCopyText) {
				putTextData(((Text) node).getData());
				needToCopyText = false;
			}
		}
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public void putFloat(String key, float f) {
		element.setAttribute(key, String.valueOf(f));
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public void putInteger(String key, int n) {
		element.setAttribute(key, String.valueOf(n));
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public void putMemento(XMLMemento memento) {
		// Do not copy the element's top level text node (this would overwrite the existing text).
		// Text nodes of children are copied.
		putElement(memento.element, false);
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public void putString(String key, String value) {
		if (value == null) {
			return;
		}
		element.setAttribute(key, value);
	}

	
Params:
key – the attribute key
value – the boolean value for the key
Since:
3.4/**
	 * @param key the attribute key
	 * @param value the boolean value for the key
	 * @since 3.4
	 */
	public void putBoolean(String key, boolean value) {
		element.setAttribute(key, value ? "true" : "false"); //$NON-NLS-1$ //$NON-NLS-2$
	}

	/*
	 * Method declared in XMLMemento.
	 */
	public void putTextData(String data) {
		Text textNode = getTextNode();
		if (textNode == null) {
			textNode = factory.createTextNode(data);
			// Always add the text node as the first child (fixes bug 93718)
			element.insertBefore(textNode, element.getFirstChild());
		} else {
			textNode.setData(data);
		}
	}

	
Saves this memento's document current values to the
specified writer.
Params:
writer – the writer used to save the memento's document
Throws:
IOException – if there is a problem serializing the document to the stream./**
	 * Saves this memento's document current values to the
	 * specified writer.
	 *
	 * @param writer the writer used to save the memento's document
	 * @throws IOException if there is a problem serializing the document to the stream.
	 */
	public void save(Writer writer) throws IOException {
		try (DOMWriter out = new DOMWriter(writer)) {
			out.print(element);
		}
	}

	
A simple XML writer.  Using this instead of the javax.xml.transform classes allows
compilation against JCL Foundation (bug 80053).
/**
	 * A simple XML writer.  Using this instead of the javax.xml.transform classes allows
	 * compilation against JCL Foundation (bug 80053).
	 */
	private static final class DOMWriter extends PrintWriter {

//    	private int tab;

		/* constants */
		private static final String XML_VERSION = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"; //$NON-NLS-1$

		
Creates a new DOM writer on the given output writer.
Params:
output – the output writer/**
		 * Creates a new DOM writer on the given output writer.
		 *
		 * @param output the output writer
		 */
		public DOMWriter(Writer output) {
			super(output);
//    		tab = 0;
			println(XML_VERSION);
		}

		
Prints the given element.
Params:
element – the element to print/**
		 * Prints the given element.
		 *
		 * @param element the element to print
		 */
		public void print(Element element) {
			// Ensure extra whitespace is not emitted next to a Text node,
			// as that will result in a situation where the restored text data is not the
			// same as the saved text data.
			boolean hasChildren = element.hasChildNodes();
			startTag(element, hasChildren);
			if (hasChildren) {
//	        	tab++;
				boolean prevWasText = false;
				NodeList children = element.getChildNodes();
				for (int i = 0; i < children.getLength(); i++) {
					Node node = children.item(i);
					if (node instanceof Element) {
						if (!prevWasText) {
							println();
							printTabulation();
						}
						print((Element) children.item(i));
						prevWasText = false;
					}
					else if (node instanceof Text) {
						print(getEscaped(node.getNodeValue()));
						prevWasText = true;
					}
				}
//	    		tab--;
				if (!prevWasText) {
					println();
					printTabulation();
				}
				endTag(element);
			}
		}

		private void printTabulation() {
			// Indenting is disabled, as it can affect the result of getTextData().
			// In 3.0, elements were separated by a newline but not indented.
			// This causes getTextData() to return "\n" even if no text data had explicitly been set.
			// The code here emulates that behaviour.

//    		for (int i = 0; i < tab; i++)
//    			super.print("\t"); //$NON-NLS-1$
		}

		private void startTag(Element element, boolean hasChildren) {
			StringBuilder sb = new StringBuilder();
			sb.append("<"); //$NON-NLS-1$
			sb.append(element.getTagName());
			NamedNodeMap attributes = element.getAttributes();
			for (int i = 0;  i < attributes.getLength(); i++) {
				Attr attribute = (Attr)attributes.item(i);
				sb.append(" "); //$NON-NLS-1$
				sb.append(attribute.getName());
				sb.append("=\""); //$NON-NLS-1$
				sb.append(getEscaped(String.valueOf(attribute.getValue())));
				sb.append("\""); //$NON-NLS-1$
			}
			sb.append(hasChildren ? ">" : "/>"); //$NON-NLS-1$ //$NON-NLS-2$
			print(sb.toString());
		}

		private void endTag(Element element) {
			StringBuilder sb = new StringBuilder();
			sb.append("</"); //$NON-NLS-1$
			sb.append(element.getNodeName());
			sb.append(">"); //$NON-NLS-1$
			print(sb.toString());
		}

		private static void appendEscapedChar(StringBuilder buffer, char c) {
			String replacement = getReplacement(c);
			if (replacement != null) {
				buffer.append('&');
				buffer.append(replacement);
				buffer.append(';');
			} else if (c==9 || c==10 || c==13 || c>=32){
				buffer.append(c);
			}
		}

		private static String getEscaped(String s) {
			StringBuilder result = new StringBuilder(s.length() + 10);
			for (int i = 0; i < s.length(); ++i) {
				appendEscapedChar(result, s.charAt(i));
			}
			return result.toString();
		}

		private static String getReplacement(char c) {
			// Encode special XML characters into the equivalent character references.
			// The first five are defined by default for all XML documents.
			// The next three (#xD, #xA, #x9) are encoded to avoid them
			// being converted to spaces on deserialization
			// (fixes bug 93720)
			switch (c) {
				case '<' :
					return "lt"; //$NON-NLS-1$
				case '>' :
					return "gt"; //$NON-NLS-1$
				case '"' :
					return "quot"; //$NON-NLS-1$
				case '\'' :
					return "apos"; //$NON-NLS-1$
				case '&' :
					return "amp"; //$NON-NLS-1$
				case '\r':
					return "#x0D"; //$NON-NLS-1$
				case '\n':
					return "#x0A"; //$NON-NLS-1$
				case '\u0009':
					return "#x09"; //$NON-NLS-1$
				default:
					break;
			}
			return null;
		}
	}
}