XslMultipageStylesheetCapture.java

/*
 * Copyright (C) 2011 Laurent Caillette
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program 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 General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.novelang.rendering.multipage;

import java.util.Map;

import com.google.common.base.Preconditions;
import org.apache.xml.utils.MutableAttrListImpl;
import org.xml.sax.Attributes;
import org.xml.sax.EntityResolver;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;

import org.novelang.outfit.xml.NamespaceAwareness;
import org.novelang.outfit.xml.SaxPipeline;
import org.novelang.outfit.xml.SaxRecorder;
import org.novelang.outfit.xml.XmlNamespaces;

/**
 * Captures the XML document inside a <{@value #MULTIPAGE_STYLESHEET_LOCALNAME}> element
 * (inside the "{@value org.novelang.outfit.xml.XmlNamespaces#XSL_META_NAMESPACE_URI}" namespace)
 * as a standalone XML document.
 * The purpose is to use it as a stylesheet afterwards.
 *
 * @author Laurent Caillette
 */
public abstract class XslMultipageStylesheetCapture extends SaxPipeline.Stage {

  private SaxRecorder documentBuilder = null ;

  /**
   * TODO use this one.
   */
  private final EntityResolver entityResolver ;


  /**
   * Override to do something with freshly-parsed stylesheet like saving it somewhere.
   */
  protected abstract void onStylesheetDocumentBuilt( SaxRecorder.Player stylesheetPlayer ) ;


  protected XslMultipageStylesheetCapture( final EntityResolver entityResolver ) {
    this.entityResolver = Preconditions.checkNotNull( entityResolver ) ;
  }

  private boolean insideNestedStylesheet() {
    return documentBuilder != null ;
  }

// ==================
// NamespaceAwareness
// ==================

  private final NamespaceAwareness namespaceAwareness =
      new NamespaceAwareness( XmlNamespaces.XSL_META_NAMESPACE_URI ) ;

  private NamespaceAwareness getNamespaceAwareness() {
    return namespaceAwareness ;
  }

  private static final String MULTIPAGE_STYLESHEET_LOCALNAME = "multipage" ;

  private boolean isNestedStylesheetRootElement( final String uri, final String localName ) {
    return getNamespaceAwareness().isMetaPrefix( uri )
        && MULTIPAGE_STYLESHEET_LOCALNAME.equals( localName ) ;
  }

  private String getXsltPrefixMapping() {
    return getNamespaceAwareness().getPrefixMappings().inverse()
        .get( XmlNamespaces.XSL_NAMESPACE_URI ) ;
  }


// ==============
// ContentHandler
// ==============

  @Override
  public void startElement(
      final String uri,
      final String localName,
      final String qName,
      final Attributes attributes
  ) throws SAXException {
    if( isNestedStylesheetRootElement( uri, localName ) ) {
      if( documentBuilder == null ) {
        documentBuilder = new SaxRecorder() ;
        documentBuilder.setDocumentLocator( getDocumentLocator() ) ;
//        documentBuilder.setEntityResolver( entityResolver ) ;
        documentBuilder.startDocument() ;
        for( final Map.Entry< String, String > prefixMapping
            : getNamespaceAwareness().getPrefixMappings().entrySet()
        ) {
          documentBuilder.startPrefixMapping( prefixMapping.getKey(), prefixMapping.getValue() ) ;
        }
      } else {
        getNamespaceAwareness().throwException( "Not allowed: nested " +
            getNamespaceAwareness().getNamespacePrefix() + ":" + MULTIPAGE_STYLESHEET_LOCALNAME ) ;
      }
    }
    if( documentBuilder != null ) {
      if( isNestedStylesheetRootElement( uri, localName ) ) {

        final AttributesImpl attributesWithVersion = new MutableAttrListImpl( attributes ) ;
        // String uri, String localName, String qName, String type, String value
        attributesWithVersion.addAttribute( "", "version", "version", "", "1.0" ) ;

        documentBuilder.startElement(
            XmlNamespaces.XSL_NAMESPACE_URI,
            "stylesheet",
            getXsltPrefixMapping() + ":" + "stylesheet",
            attributesWithVersion
        ) ;
      } else {
        documentBuilder.startElement( uri, localName, qName, attributes ) ;
      }
    }
    if( ! insideNestedStylesheet() ) {
      super.startElement( uri, localName, qName, attributes ) ;
    }

  }

  @Override
  public void endElement(
      final String uri,
      final String localName,
      final String qName
  ) throws SAXException {
    // Remain symmetrical with startElement, evaluate this before changing documentBuilder.
    final boolean wasInsideNestedStylesheet = insideNestedStylesheet() ;

    if( documentBuilder != null ) {
      if( isNestedStylesheetRootElement( uri, localName ) ) {
        documentBuilder.endElement(
            XmlNamespaces.XSL_NAMESPACE_URI,
            "stylesheet",
            getXsltPrefixMapping() + ":" + "stylesheet"
        ) ;
      } else {
        documentBuilder.endElement( uri, localName, qName ) ;
      }
      if( isNestedStylesheetRootElement( uri, localName ) ) {
        documentBuilder.endDocument() ;
        onStylesheetDocumentBuilt( documentBuilder.getPlayer() ) ;
        documentBuilder = null ;
      }
    }
    if( !wasInsideNestedStylesheet ) {
      super.endElement( uri, localName, qName ) ;
    }
  }


  @Override
  public void setDocumentLocator( final Locator locator ) {
    super.setDocumentLocator( locator ) ;
    namespaceAwareness.setDocumentLocator( getDocumentLocator() ) ;
    if( documentBuilder != null ) {
      documentBuilder.setDocumentLocator( getDocumentLocator() ) ;
    }
  }

  @Override
  public void startPrefixMapping( final String prefix, final String uri ) throws SAXException {
    namespaceAwareness.startPrefixMapping( prefix, uri ) ;
    if( documentBuilder != null ) {
      documentBuilder.startPrefixMapping( prefix, uri ) ;
    }
    if( ! insideNestedStylesheet() ) {
      super.startPrefixMapping( prefix, uri ) ;
    }
  }

  @Override
  public void endPrefixMapping( final String prefix ) throws SAXException {
    namespaceAwareness.endPrefixMapping( prefix ) ;
    if( documentBuilder != null ) {
      documentBuilder.endPrefixMapping( prefix ) ;
    }
    if( ! insideNestedStylesheet() ) {
      super.endPrefixMapping( prefix ) ;
    }
  }

  @Override
  public void characters(
      final char[] characters,
      final int start,
      final int length
  ) throws SAXException {
    if( documentBuilder != null ) {
      documentBuilder.characters( characters, start, length ) ;
    }
    if( ! insideNestedStylesheet() ) {
      super.characters( characters, start, length ) ;
    }
  }

  @Override
  public void ignorableWhitespace(
      final char[] characters,
      final int start,
      final int length
  ) throws SAXException {
    if( documentBuilder != null ) {
      documentBuilder.ignorableWhitespace( characters, start, length ) ;
    }
    if( ! insideNestedStylesheet() ) {
      super.ignorableWhitespace( characters, start, length ) ;
    }
  }

  @Override
  public void processingInstruction(
      final String target,
      final String data
  ) throws SAXException {
    if( documentBuilder != null ) {
      documentBuilder.processingInstruction( target, data ) ;
    }
    if( ! insideNestedStylesheet() ) {
      super.processingInstruction( target, data ) ;
    }

  }

  @Override
  public void skippedEntity( final String name ) throws SAXException {
    if( documentBuilder != null ) {
      documentBuilder.skippedEntity( name ) ;
    }
    if( ! insideNestedStylesheet() ) {
      super.skippedEntity( name ) ;
    }
  }
}