trinidad-impl/src/main/java/org/apache/myfaces/trinidadinternal/io/XhtmlResponseWriter.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.myfaces.trinidadinternal.io;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.ArrayList;

import javax.faces.component.UIComponent;
import javax.faces.context.ResponseWriter;

import org.apache.myfaces.trinidad.logging.TrinidadLogger;
import org.apache.myfaces.trinidad.util.IntegerUtils;
import org.apache.myfaces.trinidadinternal.share.util.CaboHttpUtils;

/**
 * Implementation of ResponseWriter for outputting XHTML.
 *
 */
public class XhtmlResponseWriter extends ResponseWriter
{
  static public final String XHTML_CONTENT_TYPE = "application/xhtml+xml";
  /**
   * Creates an XhtmlResponseWriter.
   * @param out a Writer to write to
   * @param contentType the xhtml content type
   * @param encoding the character encoding the Writer uses
   */
  public XhtmlResponseWriter(
    Writer out,
    String contentType,
    String encoding) throws UnsupportedEncodingException
  {
    _out = out;
    // Ignored: getContentType() always identifies this as XHTML
    //_contentType = contentType;
    _encoding = encoding;
    _cdataCount = 0;
    CaboHttpUtils.validateEncoding(encoding);
  }

  @Override
  public String getCharacterEncoding()
  {
    return _encoding;
  }

  @Override
  public String getContentType()
  {
    return XHTML_CONTENT_TYPE;
  }


  @Override
  public void startDocument() throws IOException
  {
  }

  @Override
  public void endDocument() throws IOException
  {
    _out.flush();
  }
  
  /**
   * Writes out CDATA start.
   * @throws IOException on any read/write error
   */
  public void startCDATA() throws IOException 
  {
    _closeStartIfNecessary();
    // Ignore all nested calls to start a CDATA section except the first - a CDATA section cannot contain the string 
    // "]]>" as the section ends ends with the first occurrence of this sequence.
    _cdataCount++;
    
    if (_cdataCount == 1)
      _out.write("<![CDATA[");
  }

  /**
   * Writes out an end CDATA element.
   * @throws IOException on any read/write error
   */
  public void endCDATA() throws IOException 
  {
    // Only close the outermost CDATA section and ignore nested calls to endCDATA(). 
    if (_cdataCount == 1)
      _out.write("]]>");
    
    _cdataCount--;
  }

  @Override
  public void flush() throws IOException
  {
    _closeStartIfNecessary();
   _out.flush();
  }


  @Override
  public void close()throws IOException
  {
    flush();
    _out.close();
  }

  @Override
  public void startElement(String name,
                           UIComponent component) throws IOException
  {
    // =-=AEW Should we force all lowercase?
    if (name.charAt(0) == 's')
    {
      // Optimization (see bug 2009019): our code has a tendency
      // to write out unnecessary empty <span> elements.  So,
      // when we start a "span" HTML element, don't actually write
      // out anything just yet;  mark it pending.
      if ("span".equals(name))
      {
        // push any pending element onto the stack of skipped elements
        _markPendingElements();

        // make this the current pending element
        _pendingElement = name;
        return;
      }
      else if ("script".equals(name) ||
               "style".equals(name))
      {
        _dontEscape = true;
      }
    }

    // start writing the element
    _startElementImpl(name);
  }


  @Override
  public void endElement(String name) throws IOException
  {
    // eliminate any <pending></pending> combinations
    if (_pendingElement != null)
    {
      // we need to return immedediately because in this
      // case, the element was never pushed onto the
      // element stack.
      _pendingElement = null;
      return;
    }

    // get the name of the last outputted element
    String element = _popSkippedElement();

    // non-null names indicate that the element was ouput, so its
    // end tag should be output as well
    if (element != null)
    {
      if (!element.equals(name))
      {
        _LOG.severe("ELEMENT_END_NAME_NOT_MATCH_START_NAME", new Object[]{name, element});
      }

      Writer out = _out;

      // always turn escaping back on once an element ends
      _dontEscape = false;

      if (_closeStart)
      {
        out.write('>');
        _closeStart = false;
      }

      out.write("</");
      out.write(name);
      out.write('>');
    }
  }


  @Override
  public void writeAttribute(String name,
                             Object value,
                             String componentPropertyName)
        throws IOException
  {
    if (value == null)
      return;

    // if we have a pending element, flush it because
    // it has an attribute, and is thus needed
    _outputPendingElements();

    Writer out = _out;

    Class<?> valueClass = value.getClass();

    // Output Boolean values specially
    if (valueClass == _BOOLEAN_CLASS)
    {
      if (Boolean.TRUE.equals(value))
      {
        out.write(' ');
        out.write(name);
        out.write("=\"");
        out.write(name);
        out.write("\"");
      }
    }
    else
    {
      out.write(' ');
      out.write(name);
      out.write("=\"");

      // write the attribute value
      _writeValue(valueClass, value, true);
      out.write('"');
    }
  }


  @Override
  public void writeURIAttribute(String name,
                                Object value,
                                String componentPropertyName)
    throws IOException
  {
    // XML attributes are XML attributes, etc.
    writeAttribute(name, value, componentPropertyName);
  }

  @Override
  public void writeComment(Object comment) throws IOException
  {
    if (comment != null)
    {
      _closeStartIfNecessary();
      _out.write("<!--");
      _out.write(comment.toString());
      _out.write("-->");
    }
  }


  @Override
  public void writeText(Object text, String componentPropertyName)
     throws IOException
  {
    if (text != null)
    {
      String valueString = text.toString();
      
      if (_dontEscape)
      {
        write(text.toString());
      }
      else
      {
        _closeStartIfNecessary();

        XMLEscapes.writeText(_out, valueString);
      }
    }
  }


  @Override
  public void writeText(char text[], int off, int len)
        throws IOException
  {
    if (_dontEscape)
    {
      write(text, off, len);
    }
    else
    {
      _closeStartIfNecessary();
      XMLEscapes.writeText(_out, text, off, len);
    }
  }

  @Override
  public void write(char cbuf[], int off, int len) throws IOException
  {
    _closeStartIfNecessary();
    _out.write(cbuf, off, len);
  }

  @Override
  public void write(String str) throws IOException
  {
    _closeStartIfNecessary();
    _out.write(str);
  }

  @Override
  public void write(int c) throws IOException
  {
    _closeStartIfNecessary();
    _out.write((char) c);
  }


  @Override
  public ResponseWriter cloneWithWriter(Writer writer)
  {
    try
    {
      return new XhtmlResponseWriter(writer, getContentType(),
                                     getCharacterEncoding());
    }
    catch (UnsupportedEncodingException e)
    {
      // this can't happen;  the character encoding should already
      // be legal.
      assert(false);
      throw new IllegalStateException();
    }
  }

  //
  // Private methods
  //

  private void _startElementImpl(String name) throws IOException
  {
    // close any previously stated element, if necessary
    _closeStartIfNecessary();

    // note that we started a non-skipped element
    _pushOutputtedElement(name);

    Writer out = _out;
    out.write('<');
    out.write(name);
    _closeStart = true;

  }


  /**
   * Writes the value of an object
   */
  private void _writeValue(
    Class<?>    valueClass,
    Object      value,
    boolean     isAttribute
    ) throws IOException
  {
    assert(valueClass != _CHAR_ARRAY_CLASS) :
           "Character arrays not supported as HTML attributes";

    if (valueClass == _INTEGER_CLASS)
    {
      // Integers never need to be escaped - and
      // we can cache common instances.
      _out.write(IntegerUtils.getString((Integer) value));

      return;
    }

    String stringValue = value.toString();
      
    if (isAttribute)
    {
      XMLEscapes.writeAttribute(_out, stringValue);
    }
    else
    {
      XMLEscapes.writeText(_out, stringValue);
    }
  }


  private void _closeStartIfNecessary() throws IOException
  {
    _markPendingElements();

    if (_closeStart)
    {
      _out.write('>');
      _closeStart = false;
    }
  }


  /**
   * Flushes out any pending element, celaring the pending
   * entry.
   */
  private void _outputPendingElements() throws IOException
  {
    String pendingElement = _pendingElement;

    if (pendingElement != null)
    {
      // we clear the pending element BEFORE calling
      // startElementImpl to prevent _startElementImpl's indirect call
      // to _markPendingElements from pushing our element onto
      // the skipped stack, imbalancing the stack
      _pendingElement = null;

      // start the pending element
      _startElementImpl(pendingElement);
    }
  }

  /**
   * If an element is pending, push it onto the stack of skipped
   * elements because it doesn't have any attributes
   */
  private void _markPendingElements()
  {
    String pendingElement = _pendingElement;
    if (pendingElement != null)
    {
      _pushSkippedElement();
      _pendingElement = null;
    }
  }


  /**
   * Retrieves the name of the last output element.  If it is null,
   * that element was skipped and thus its end tag should be suppressed
   * as well
   */
  private String _popSkippedElement()
  {
    int size = _skippedElements.size();
    if (size == 0)
      return null;

    return _skippedElements.remove(size - 1);
  }

  /**
   * Marks the skipped element so that the output of its
   * end tag can also be suppressed
   */
  private void _pushSkippedElement()
  {
    _skippedElements.add(null);
  }


  /**
   * Marks that we have outputted a real element so that the ordering of
   * the outputted and skipped elements can be maintained.  This
   * also aids debuggin by ensuring that the element being ended matches
   * the actual ouputted name.
   */
  private void _pushOutputtedElement(
    String name
    )
  {
    _skippedElements.add(name);
  }

  private boolean     _closeStart;
  private boolean     _dontEscape;

  private Writer       _out;
  private String       _encoding;

  // holds an element that will only be started if it has attributes
  private String      _pendingElement;
  
  // number of CDATA sections started
  private int         _cdataCount;

  // stack of skipped and unskipped elements used to determine when
  // to suppress the end tag of a skipped element
  private final ArrayList<String> _skippedElements = new ArrayList<String>(20);


  private static final Class<?> _CHAR_ARRAY_CLASS = (new char[0]).getClass();
  private static final Class<?> _BOOLEAN_CLASS = Boolean.class;
  private static final Class<?> _INTEGER_CLASS = Integer.class;

  static private final TrinidadLogger _LOG = TrinidadLogger.createTrinidadLogger(XhtmlResponseWriter.class);

}