package org.apache.maven.shared.utils.xml;
   
   /*
    * 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.
   */
  
  import org.apache.maven.shared.utils.xml.pull.XmlPullParserException;
  import org.xml.sax.Attributes;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  import org.xml.sax.helpers.DefaultHandler;
  
  import javax.annotation.Nonnull;
  import javax.annotation.WillClose;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.io.UnsupportedEncodingException;
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * @author Kristian Rosenvold
   */
  public class Xpp3DomBuilder
  {
      private static final boolean DEFAULT_TRIM = true;
  
      /**
       * @param reader {@link Reader}
       * @return the built dom.
       * @throws XmlPullParserException in case of an error.
       */
      public static Xpp3Dom build( @WillClose @Nonnull Reader reader )
          throws XmlPullParserException
      {
          return build( reader, DEFAULT_TRIM );
      }
  
      /**
       * @param is {@link InputStream}
       * @param encoding The encoding.
       * @return the built dom.
       * @throws XmlPullParserException in case of an error.
       */
      public static Xpp3Dom build( @WillClose InputStream is, @Nonnull String encoding )
          throws XmlPullParserException
      {
          return build( is, encoding, DEFAULT_TRIM );
      }
  
      /**
       * @param is {@link InputStream}
       * @param encoding The encoding.
       * @param trim true/false.
       * @return the built dom.
       * @throws XmlPullParserException in case of an error.
       */
      public static Xpp3Dom build( @WillClose InputStream is, @Nonnull String encoding, boolean trim )
          throws XmlPullParserException
      {
          try
          {
              Reader reader = new InputStreamReader( is, encoding );
              return build( reader, trim );
          }
          catch ( UnsupportedEncodingException e )
          {
              throw new RuntimeException( e );
          }
      }
  
      /**
       * @param reader {@link Reader}
       * @param trim true/false
       * @return the built dom
       * @throws XmlPullParserException in case of an error
       */
      public static Xpp3Dom build( @WillClose Reader in, boolean trim )
          throws XmlPullParserException
      {
         try ( Reader reader = in )  
         {
             DocHandler docHandler = parseSax( new InputSource( reader ), trim );
             reader.close();
             return docHandler.result;
         }
         catch ( final IOException e )
         {
             throw new XmlPullParserException( e );
         }
     }
 
     private static DocHandler parseSax( @Nonnull InputSource inputSource, boolean trim )
         throws XmlPullParserException
     {
         try
         {
             DocHandler ch = new DocHandler( trim );
             XMLReader parser = createXmlReader();
             parser.setContentHandler( ch );
             parser.parse( inputSource );
             return ch;
         }
         catch ( IOException e )
         {
             throw new XmlPullParserException( e );
         }
         catch ( SAXException e )
         {
             throw new XmlPullParserException( e );
         }
     }
 
 
     private static XMLReader createXmlReader()
         throws SAXException
     {
         XMLReader comSunXmlReader = instantiate( "com.sun.org.apache.xerces.internal.parsers.SAXParser" );
         if ( comSunXmlReader != null )
         {
             return comSunXmlReader;
         }
 
         String key = "org.xml.sax.driver";
         String oldParser = System.getProperty( key );
         System.clearProperty( key ); // There's a "slight" problem with this an parallel maven: It does not work ;)
 
         try
         {
             return org.xml.sax.helpers.XMLReaderFactory.createXMLReader();
         }
         finally
         {
             if ( oldParser != null )
             {
                 System.setProperty( key, oldParser );
             }
         }
 
     }
 
     private static XMLReader instantiate( String s )
     {
         try
         {
             Class<?> aClass = Thread.currentThread().getContextClassLoader().loadClass( s );
             return (XMLReader) aClass.newInstance();
         }
         catch ( ClassNotFoundException e )
         {
             return  null;
         }
         catch ( InstantiationException e )
         {
             return  null;
         }
         catch ( IllegalAccessException e )
         {
             return  null;
         }
     }
 
 
     private static class DocHandler
         extends DefaultHandler
     {
         private final List<Xpp3Dom> elemStack = new ArrayList<Xpp3Dom>();
 
         private final List<StringBuilder> values = new ArrayList<StringBuilder>();
 
         Xpp3Dom result = null;
 
         private final boolean trim;
 
         private boolean spacePreserve = false;
 
         DocHandler( boolean trim )
         {
             this.trim = trim;
         }
 
         @Override
         public void startElement( String uri, String localName, String qName, Attributes attributes )
             throws SAXException
         {
             spacePreserve = false;
             Xpp3Dom child = new Xpp3Dom( localName );
 
             attachToParent( child );
             pushOnStack( child );
 
             // Todo: Detecting tags that close immediately seem to be impossible in sax ?
             // http://stackoverflow.com/questions/12968390/detecting-self-closing-tags-in-sax
             values.add( new StringBuilder() );
 
             int size = attributes.getLength();
             for ( int i = 0; i < size; i++ )
             {
                 String name = attributes.getQName( i );
                 String value = attributes.getValue( i );
                 child.setAttribute( name, value );
                 spacePreserve = spacePreserve || ( "xml:space".equals( name ) && "preserve".equals( value ) );
             }
         }
 
         private boolean pushOnStack( Xpp3Dom child )
         {
             return elemStack.add( child );
         }
 
         private void attachToParent( Xpp3Dom child )
         {
             int depth = elemStack.size();
             if ( depth > 0 )
             {
                 elemStack.get( depth - 1 ).addChild( child );
             }
         }
 
         private Xpp3Dom pop()
         {
             int depth = elemStack.size() - 1;
             return elemStack.remove( depth );
         }
 
         @Override
         public void endElement( String uri, String localName, String qName )
             throws SAXException
         {
             int depth = elemStack.size() - 1;
 
             Xpp3Dom element = pop();
 
             /* this Object could be null if it is a singleton tag */
             Object accumulatedValue = values.remove( depth );
 
             if ( element.getChildCount() == 0 )
             {
                 if ( accumulatedValue == null )
                 {
                     element.setValue( "" ); // null in xpp3dom, but we don't do that around here
                 }
                 else
                 {
                     element.setValue( accumulatedValue.toString() );
                 }
             }
 
             if ( depth == 0 )
             {
                 result = element;
             }
         }
 
         @Override
         public void characters( char[] ch, int start, int length )
             throws SAXException
         {
             String text = new String( ch, start, length );
             appendToTopValue( ( trim && !spacePreserve ) ? text.trim() : text );
         }
 
         private void appendToTopValue( String toAppend )
         {
             // noinspection MismatchedQueryAndUpdateOfStringBuilder
             StringBuilder stringBuilder = values.get( values.size() - 1 );
             stringBuilder.append( toAppend );
         }
     }
 
 }