/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */
package java.beans;

import java.io.*;
import java.util.*;
import java.lang.reflect.*;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.IllegalCharsetNameException;
import java.nio.charset.UnsupportedCharsetException;

/**
 * The <code>XMLEncoder</code> class is a complementary alternative to
 * the <code>ObjectOutputStream</code> and can used to generate
 * a textual representation of a <em>JavaBean</em> in the same
 * way that the <code>ObjectOutputStream</code> can
 * be used to create binary representation of <code>Serializable</code>
 * objects. For example, the following fragment can be used to create
 * a textual representation the supplied <em>JavaBean</em>
 * and all its properties:
 * <pre>
 * XMLEncoder e = new XMLEncoder(
 * new BufferedOutputStream(
 * new FileOutputStream("Test.xml")));
 * e.writeObject(new JButton("Hello, world"));
 * e.close();
 * </pre>
 * Despite the similarity of their APIs, the <code>XMLEncoder</code>
 * class is exclusively designed for the purpose of archiving graphs
 * of <em>JavaBean</em>s as textual representations of their public
 * properties. Like Java source files, documents written this way
 * have a natural immunity to changes in the implementations of the classes
 * involved. The <code>ObjectOutputStream</code> continues to be recommended
 * for interprocess communication and general purpose serialization.
 * <p>
 * The <code>XMLEncoder</code> class provides a default denotation for
 * <em>JavaBean</em>s in which they are represented as XML documents
 * complying with version 1.0 of the XML specification and the
 * UTF-8 character encoding of the Unicode/ISO 10646 character set.
 * The XML documents produced by the <code>XMLEncoder</code> class are:
 * <ul>
 * <li>
 * <em>Portable and version resilient</em>: they have no dependencies
 * on the private implementation of any class and so, like Java source
 * files, they may be exchanged between environments which may have
 * different versions of some of the classes and between VMs from
 * different vendors.
 * <li>
 * <em>Structurally compact</em>: The <code>XMLEncoder</code> class
 * uses a <em>redundancy elimination</em> algorithm internally so that the
 * default values of a Bean's properties are not written to the stream.
 * <li>
 * <em>Fault tolerant</em>: Non-structural errors in the file,
 * caused either by damage to the file or by API changes
 * made to classes in an archive remain localized
 * so that a reader can report the error and continue to load the parts
 * of the document which were not affected by the error.
 * </ul>
 * <p>
 * Below is an example of an XML archive containing
 * some user interface components from the <em>swing</em> toolkit:
 * <pre>
 * &lt;?xml version="1.0" encoding="UTF-8"?&gt;
 * &lt;java version="1.0" class="java.beans.XMLDecoder"&gt;
 * &lt;object class="javax.swing.JFrame"&gt;
 * &lt;void property="name"&gt;
 * &lt;string&gt;frame1&lt;/string&gt;
 * &lt;/void&gt;
 * &lt;void property="bounds"&gt;
 * &lt;object class="java.awt.Rectangle"&gt;
 * &lt;int&gt;0&lt;/int&gt;
 * &lt;int&gt;0&lt;/int&gt;
 * &lt;int&gt;200&lt;/int&gt;
 * &lt;int&gt;200&lt;/int&gt;
 * &lt;/object&gt;
 * &lt;/void&gt;
 * &lt;void property="contentPane"&gt;
 * &lt;void method="add"&gt;
 * &lt;object class="javax.swing.JButton"&gt;
 * &lt;void property="label"&gt;
 * &lt;string&gt;Hello&lt;/string&gt;
 * &lt;/void&gt;
 * &lt;/object&gt;
 * &lt;/void&gt;
 * &lt;/void&gt;
 * &lt;void property="visible"&gt;
 * &lt;boolean&gt;true&lt;/boolean&gt;
 * &lt;/void&gt;
 * &lt;/object&gt;
 * &lt;/java&gt;
 * </pre>
 * The XML syntax uses the following conventions:
 * <ul>
 * <li>
 * Each element represents a method call.
 * <li>
 * The "object" tag denotes an <em>expression</em> whose value is
 * to be used as the argument to the enclosing element.
 * <li>
 * The "void" tag denotes a <em>statement</em> which will
 * be executed, but whose result will not be used as an
 * argument to the enclosing method.
 * <li>
 * Elements which contain elements use those elements as arguments,
 * unless they have the tag: "void".
 * <li>
 * The name of the method is denoted by the "method" attribute.
 * <li>
 * XML's standard "id" and "idref" attributes are used to make
 * references to previous expressions - so as to deal with
 * circularities in the object graph.
 * <li>
 * The "class" attribute is used to specify the target of a static
 * method or constructor explicitly; its value being the fully
 * qualified name of the class.
 * <li>
 * Elements with the "void" tag are executed using
 * the outer context as the target if no target is defined
 * by a "class" attribute.
 * <li>
 * Java's String class is treated specially and is
 * written &lt;string&gt;Hello, world&lt;/string&gt; where
 * the characters of the string are converted to bytes
 * using the UTF-8 character encoding.
 * </ul>
 * <p>
 * Although all object graphs may be written using just these three
 * tags, the following definitions are included so that common
 * data structures can be expressed more concisely:
 * <p>
 * <ul>
 * <li>
 * The default method name is "new".
 * <li>
 * A reference to a java class is written in the form
 * &lt;class&gt;javax.swing.JButton&lt;/class&gt;.
 * <li>
 * Instances of the wrapper classes for Java's primitive types are written
 * using the name of the primitive type as the tag. For example, an
 * instance of the <code>Integer</code> class could be written:
 * &lt;int&gt;123&lt;/int&gt;. Note that the <code>XMLEncoder</code> class
 * uses Java's reflection package in which the conversion between
 * Java's primitive types and their associated "wrapper classes"
 * is handled internally. The API for the <code>XMLEncoder</code> class
 * itself deals only with <code>Object</code>s.
 * <li>
 * In an element representing a nullary method whose name
 * starts with "get", the "method" attribute is replaced
 * with a "property" attribute whose value is given by removing
 * the "get" prefix and decapitalizing the result.
 * <li>
 * In an element representing a monadic method whose name
 * starts with "set", the "method" attribute is replaced
 * with a "property" attribute whose value is given by removing
 * the "set" prefix and decapitalizing the result.
 * <li>
 * In an element representing a method named "get" taking one
 * integer argument, the "method" attribute is replaced
 * with an "index" attribute whose value the value of the
 * first argument.
 * <li>
 * In an element representing a method named "set" taking two arguments,
 * the first of which is an integer, the "method" attribute is replaced
 * with an "index" attribute whose value the value of the
 * first argument.
 * <li>
 * A reference to an array is written using the "array"
 * tag. The "class" and "length" attributes specify the
 * sub-type of the array and its length respectively.
 * </ul>
 *
 *<p>
 * For more information you might also want to check out
 * <a
 href="http://java.sun.com/products/jfc/tsc/articles/persistence4">Using XMLEncoder</a>,
 * an article in <em>The Swing Connection.</em>
 * @see XMLDecoder
 * @see java.io.ObjectOutputStream
 *
 * @since 1.4
 *
 * @author Philip Milne
 */
public class XMLEncoder extends Encoder implements AutoCloseable {

 private final CharsetEncoder encoder;
 private final String charset;
 private final boolean declaration;

 private OutputStreamWriter out;
 private Object owner;
 private int indentation = 0;
 private boolean internal = false;
 private Map<Object, ValueData> valueToExpression;
 private Map<Object, List<Statement>> targetToStatementList;
 private boolean preambleWritten = false;
 private NameGenerator nameGenerator;

 private class ValueData {
 public int refs = 0;
 public boolean marked = false; // Marked -> refs > 0 unless ref was a target.
 public String name = null;
 public Expression exp = null;
 }

 /**
 * Creates a new XML encoder to write out <em>JavaBeans</em>
 * to the stream <code>out</code> using an XML encoding.
 *
 * @param out the stream to which the XML representation of
 * the objects will be written
 *
 * @throws IllegalArgumentException
 * if <code>out</code> is <code>null</code>
 *
 * @see XMLDecoder#XMLDecoder(InputStream)
 */
 public XMLEncoder(OutputStream out) {
 this(out, "UTF-8", true, 0);
 }

 /**
 * Creates a new XML encoder to write out <em>JavaBeans</em>
 * to the stream <code>out</code> using the given <code>charset</code>
 * starting from the given <code>indentation</code>.
 *
 * @param out the stream to which the XML representation of
 * the objects will be written
 * @param charset the name of the requested charset;
 * may be either a canonical name or an alias
 * @param declaration whether the XML declaration should be generated;
 * set this to <code>false</code>
 * when embedding the contents in another XML document
 * @param indentation the number of space characters to indent the entire XML document by
 *
 * @throws IllegalArgumentException
 * if <code>out</code> or <code>charset</code> is <code>null</code>,
 * or if <code>indentation</code> is less than 0
 *
 * @throws IllegalCharsetNameException
 * if <code>charset</code> name is illegal
 *
 * @throws UnsupportedCharsetException
 * if no support for the named charset is available
 * in this instance of the Java virtual machine
 *
 * @throws UnsupportedOperationException
 * if loaded charset does not support encoding
 *
 * @see Charset#forName(String)
 *
 * @since 1.7
 */
 public XMLEncoder(OutputStream out, String charset, boolean declaration, int indentation) {
 if (out == null) {
 throw new IllegalArgumentException("the output stream cannot be null");
 }
 if (indentation < 0) {
 throw new IllegalArgumentException("the indentation must be >= 0");
 }
 Charset cs = Charset.forName(charset);
 this.encoder = cs.newEncoder();
 this.charset = charset;
 this.declaration = declaration;
 this.indentation = indentation;
 this.out = new OutputStreamWriter(out, cs.newEncoder());
 valueToExpression = new IdentityHashMap<>();
 targetToStatementList = new IdentityHashMap<>();
 nameGenerator = new NameGenerator();
 }

 /**
 * Sets the owner of this encoder to <code>owner</code>.
 *
 * @param owner The owner of this encoder.
 *
 * @see #getOwner
 */
 public void setOwner(Object owner) {
 this.owner = owner;
 writeExpression(new Expression(this, "getOwner", new Object[0]));
 }

 /**
 * Gets the owner of this encoder.
 *
 * @return The owner of this encoder.
 *
 * @see #setOwner
 */
 public Object getOwner() {
 return owner;
 }

 /**
 * Write an XML representation of the specified object to the output.
 *
 * @param o The object to be written to the stream.
 *
 * @see XMLDecoder#readObject
 */
 public void writeObject(Object o) {
 if (internal) {
 super.writeObject(o);
 }
 else {
 writeStatement(new Statement(this, "writeObject", new Object[]{o}));
 }
 }

 private List<Statement> statementList(Object target) {
 List<Statement> list = targetToStatementList.get(target);
 if (list == null) {
 list = new ArrayList<>();
 targetToStatementList.put(target, list);
 }
 return list;
 }


 private void mark(Object o, boolean isArgument) {
 if (o == null || o == this) {
 return;
 }
 ValueData d = getValueData(o);
 Expression exp = d.exp;
 // Do not mark liternal strings. Other strings, which might,
 // for example, come from resource bundles should still be marked.
 if (o.getClass() == String.class && exp == null) {
 return;
 }

 // Bump the reference counts of all arguments
 if (isArgument) {
 d.refs++;
 }
 if (d.marked) {
 return;
 }
 d.marked = true;
 Object target = exp.getTarget();
 mark(exp);
 if (!(target instanceof Class)) {
 statementList(target).add(exp);
 // Pending: Why does the reference count need to
 // be incremented here?
 d.refs++;
 }
 }

 private void mark(Statement stm) {
 Object[] args = stm.getArguments();
 for (int i = 0; i < args.length; i++) {
 Object arg = args[i];
 mark(arg, true);
 }
 mark(stm.getTarget(), stm instanceof Expression);
 }


 /**
 * Records the Statement so that the Encoder will
 * produce the actual output when the stream is flushed.
 * <P>
 * This method should only be invoked within the context
 * of initializing a persistence delegate.
 *
 * @param oldStm The statement that will be written
 * to the stream.
 * @see java.beans.PersistenceDelegate#initialize
 */
 public void writeStatement(Statement oldStm) {
 // System.out.println("XMLEncoder::writeStatement: " + oldStm);
 boolean internal = this.internal;
 this.internal = true;
 try {
 super.writeStatement(oldStm);
 /*
 Note we must do the mark first as we may
 require the results of previous values in
 this context for this statement.
 Test case is:
 os.setOwner(this);
 os.writeObject(this);
 */
 mark(oldStm);
 Object target = oldStm.getTarget();
 if (target instanceof Field) {
 String method = oldStm.getMethodName();
 Object[] args = oldStm.getArguments();
 if ((method == null) || (args == null)) {
 }
 else if (method.equals("get") && (args.length == 1)) {
 target = args[0];
 }
 else if (method.equals("set") && (args.length == 2)) {
 target = args[0];
 }
 }
 statementList(target).add(oldStm);
 }
 catch (Exception e) {
 getExceptionListener().exceptionThrown(new Exception("XMLEncoder: discarding statement " + oldStm, e));
 }
 this.internal = internal;
 }


 /**
 * Records the Expression so that the Encoder will
 * produce the actual output when the stream is flushed.
 * <P>
 * This method should only be invoked within the context of
 * initializing a persistence delegate or setting up an encoder to
 * read from a resource bundle.
 * <P>
 * For more information about using resource bundles with the
 * XMLEncoder, see
 * http://java.sun.com/products/jfc/tsc/articles/persistence4/#i18n
 *
 * @param oldExp The expression that will be written
 * to the stream.
 * @see java.beans.PersistenceDelegate#initialize
 */
 public void writeExpression(Expression oldExp) {
 boolean internal = this.internal;
 this.internal = true;
 Object oldValue = getValue(oldExp);
 if (get(oldValue) == null || (oldValue instanceof String && !internal)) {
 getValueData(oldValue).exp = oldExp;
 super.writeExpression(oldExp);
 }
 this.internal = internal;
 }

 /**
 * This method writes out the preamble associated with the
 * XML encoding if it has not been written already and
 * then writes out all of the values that been
 * written to the stream since the last time <code>flush</code>
 * was called. After flushing, all internal references to the
 * values that were written to this stream are cleared.
 */
 public void flush() {
 if (!preambleWritten) { // Don't do this in constructor - it throws ... pending.
 if (this.declaration) {
 writeln("<?xml version=" + quote("1.0") +
 " encoding=" + quote(this.charset) + "?>");
 }
 writeln("<java version=" + quote(System.getProperty("java.version")) +
 " class=" + quote(XMLDecoder.class.getName()) + ">");
 preambleWritten = true;
 }
 indentation++;
 List<Statement> statements = statementList(this);
 while (!statements.isEmpty()) {
 Statement s = statements.remove(0);
 if ("writeObject".equals(s.getMethodName())) {
 outputValue(s.getArguments()[0], this, true);
 }
 else {
 outputStatement(s, this, false);
 }
 }
 indentation--;

 Statement statement = getMissedStatement();
 while (statement != null) {
 outputStatement(statement, this, false);
 statement = getMissedStatement();
 }

 try {
 out.flush();
 }
 catch (IOException e) {
 getExceptionListener().exceptionThrown(e);
 }
 clear();
 }

 void clear() {
 super.clear();
 nameGenerator.clear();
 valueToExpression.clear();
 targetToStatementList.clear();
 }

 Statement getMissedStatement() {
 for (List<Statement> statements : this.targetToStatementList.values()) {
 for (int i = 0; i < statements.size(); i++) {
 if (Statement.class == statements.get(i).getClass()) {
 return statements.remove(i);
 }
 }
 }
 return null;
 }


 /**
 * This method calls <code>flush</code>, writes the closing
 * postamble and then closes the output stream associated
 * with this stream.
 */
 public void close() {
 flush();
 writeln("</java>");
 try {
 out.close();
 }
 catch (IOException e) {
 getExceptionListener().exceptionThrown(e);
 }
 }

 private String quote(String s) {
 return "\"" + s + "\"";
 }

 private ValueData getValueData(Object o) {
 ValueData d = valueToExpression.get(o);
 if (d == null) {
 d = new ValueData();
 valueToExpression.put(o, d);
 }
 return d;
 }

 /**
 * Returns <code>true</code> if the argument,
 * a Unicode code point, is valid in XML documents.
 * Unicode characters fit into the low sixteen bits of a Unicode code point,
 * and pairs of Unicode <em>surrogate characters</em> can be combined
 * to encode Unicode code point in documents containing only Unicode.
 * (The <code>char</code> datatype in the Java Programming Language
 * represents Unicode characters, including unpaired surrogates.)
 * <par>
 * [2] Char ::= #x0009 | #x000A | #x000D
 * | [#x0020-#xD7FF]
 * | [#xE000-#xFFFD]
 * | [#x10000-#x10ffff]
 * </par>
 *
 * @param code the 32-bit Unicode code point being tested
 * @return <code>true</code> if the Unicode code point is valid,
 * <code>false</code> otherwise
 */
 private static boolean isValidCharCode(int code) {
 return (0x0020 <= code && code <= 0xD7FF)
 || (0x000A == code)
 || (0x0009 == code)
 || (0x000D == code)
 || (0xE000 <= code && code <= 0xFFFD)
 || (0x10000 <= code && code <= 0x10ffff);
 }

 private void writeln(String exp) {
 try {
 StringBuilder sb = new StringBuilder();
 for(int i = 0; i < indentation; i++) {
 sb.append(' ');
 }
 sb.append(exp);
 sb.append('\n');
 this.out.write(sb.toString());
 }
 catch (IOException e) {
 getExceptionListener().exceptionThrown(e);
 }
 }

 private void outputValue(Object value, Object outer, boolean isArgument) {
 if (value == null) {
 writeln("<null/>");
 return;
 }

 if (value instanceof Class) {
 writeln("<class>" + ((Class)value).getName() + "</class>");
 return;
 }

 ValueData d = getValueData(value);
 if (d.exp != null) {
 Object target = d.exp.getTarget();
 String methodName = d.exp.getMethodName();

 if (target == null || methodName == null) {
 throw new NullPointerException((target == null ? "target" :
 "methodName") + " should not be null");
 }

 if (isArgument && target instanceof Field && methodName.equals("get")) {
 Field f = (Field)target;
 writeln("<object class=" + quote(f.getDeclaringClass().getName()) +
 " field=" + quote(f.getName()) + "/>");
 return;
 }

 Class<?> primitiveType = primitiveTypeFor(value.getClass());
 if (primitiveType != null && target == value.getClass() &&
 methodName.equals("new")) {
 String primitiveTypeName = primitiveType.getName();
 // Make sure that character types are quoted correctly.
 if (primitiveType == Character.TYPE) {
 char code = ((Character) value).charValue();
 if (!isValidCharCode(code)) {
 writeln(createString(code));
 return;
 }
 value = quoteCharCode(code);
 if (value == null) {
 value = Character.valueOf(code);
 }
 }
 writeln("<" + primitiveTypeName + ">" + value + "</" +
 primitiveTypeName + ">");
 return;
 }

 } else if (value instanceof String) {
 writeln(createString((String) value));
 return;
 }

 if (d.name != null) {
 if (isArgument) {
 writeln("<object idref=" + quote(d.name) + "/>");
 }
 else {
 outputXML("void", " idref=" + quote(d.name), value);
 }
 }
 else if (d.exp != null) {
 outputStatement(d.exp, outer, isArgument);
 }
 }

 private static String quoteCharCode(int code) {
 switch(code) {
 case '&': return "&amp;";
 case '<': return "&lt;";
 case '>': return "&gt;";
 case '"': return "&quot;";
 case '\'': return "&apos;";
 case '\r': return "&#13;";
 default: return null;
 }
 }

 private static String createString(int code) {
 return "<char code=\"#" + Integer.toString(code, 16) + "\"/>";
 }

 private String createString(String string) {
 StringBuilder sb = new StringBuilder();
 sb.append("<string>");
 int index = 0;
 while (index < string.length()) {
 int point = string.codePointAt(index);
 int count = Character.charCount(point);

 if (isValidCharCode(point) && this.encoder.canEncode(string.substring(index, index + count))) {
 String value = quoteCharCode(point);
 if (value != null) {
 sb.append(value);
 } else {
 sb.appendCodePoint(point);
 }
 index += count;
 } else {
 sb.append(createString(string.charAt(index)));
 index++;
 }
 }
 sb.append("</string>");
 return sb.toString();
 }

 private void outputStatement(Statement exp, Object outer, boolean isArgument) {
 Object target = exp.getTarget();
 String methodName = exp.getMethodName();

 if (target == null || methodName == null) {
 throw new NullPointerException((target == null ? "target" :
 "methodName") + " should not be null");
 }

 Object[] args = exp.getArguments();
 boolean expression = exp.getClass() == Expression.class;
 Object value = (expression) ? getValue((Expression)exp) : null;

 String tag = (expression && isArgument) ? "object" : "void";
 String attributes = "";
 ValueData d = getValueData(value);

 // Special cases for targets.
 if (target == outer) {
 }
 else if (target == Array.class && methodName.equals("newInstance")) {
 tag = "array";
 attributes = attributes + " class=" + quote(((Class)args[0]).getName());
 attributes = attributes + " length=" + quote(args[1].toString());
 args = new Object[]{};
 }
 else if (target.getClass() == Class.class) {
 attributes = attributes + " class=" + quote(((Class)target).getName());
 }
 else {
 d.refs = 2;
 if (d.name == null) {
 getValueData(target).refs++;
 List<Statement> statements = statementList(target);
 if (!statements.contains(exp)) {
 statements.add(exp);
 }
 outputValue(target, outer, false);
 }
 if (expression) {
 outputValue(value, outer, isArgument);
 }
 return;
 }
 if (expression && (d.refs > 1)) {
 String instanceName = nameGenerator.instanceName(value);
 d.name = instanceName;
 attributes = attributes + " id=" + quote(instanceName);
 }

 // Special cases for methods.
 if ((!expression && methodName.equals("set") && args.length == 2 &&
 args[0] instanceof Integer) ||
 (expression && methodName.equals("get") && args.length == 1 &&
 args[0] instanceof Integer)) {
 attributes = attributes + " index=" + quote(args[0].toString());
 args = (args.length == 1) ? new Object[]{} : new Object[]{args[1]};
 }
 else if ((!expression && methodName.startsWith("set") && args.length == 1) ||
 (expression && methodName.startsWith("get") && args.length == 0)) {
 if (3 < methodName.length()) {
 attributes = attributes + " property=" +
 quote(Introspector.decapitalize(methodName.substring(3)));
 }
 }
 else if (!methodName.equals("new") && !methodName.equals("newInstance")) {
 attributes = attributes + " method=" + quote(methodName);
 }
 outputXML(tag, attributes, value, args);
 }

 private void outputXML(String tag, String attributes, Object value, Object... args) {
 List<Statement> statements = statementList(value);
 // Use XML's short form when there is no body.
 if (args.length == 0 && statements.size() == 0) {
 writeln("<" + tag + attributes + "/>");
 return;
 }

 writeln("<" + tag + attributes + ">");
 indentation++;

 for(int i = 0; i < args.length; i++) {
 outputValue(args[i], null, true);
 }

 while (!statements.isEmpty()) {
 Statement s = statements.remove(0);
 outputStatement(s, value, false);
 }

 indentation--;
 writeln("</" + tag + ">");
 }

 @SuppressWarnings("rawtypes")
 static Class primitiveTypeFor(Class wrapper) {
 if (wrapper == Boolean.class) return Boolean.TYPE;
 if (wrapper == Byte.class) return Byte.TYPE;
 if (wrapper == Character.class) return Character.TYPE;
 if (wrapper == Short.class) return Short.TYPE;
 if (wrapper == Integer.class) return Integer.TYPE;
 if (wrapper == Long.class) return Long.TYPE;
 if (wrapper == Float.class) return Float.TYPE;
 if (wrapper == Double.class) return Double.TYPE;
 if (wrapper == Void.class) return Void.TYPE;
 return null;
 }
}