/**
    *    Copyright 2011 meltmedia
    *
    *    Licensed 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.xchain.namespaces.sax;
  
  import org.apache.commons.jxpath.JXPathContext;
  
  import org.xchain.Command;
  import org.xchain.annotations.Attribute;
  import org.xchain.annotations.AttributeType;
  import org.xchain.annotations.Element;
  import org.xchain.framework.net.UrlFactory;
  
  import java.net.URL;
  
  import java.io.OutputStream;
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.Writer;
  
  import javax.xml.transform.dom.DOMResult;
  import javax.xml.transform.sax.SAXResult;
  import javax.xml.transform.stream.StreamResult;
  import javax.xml.transform.Result;
  
  import org.xml.sax.ContentHandler;
  
  import org.w3c.dom.Node;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * <p>The &lt;sax:result/&gt; command adds result objects to a pipeline.  This command can add several types of results, based on the attributes
   * defined on the command.  To write output to a system id, add the system-id attribute to the command:</p>
   *
   * <code class="source">
   * &lt;sax:pipeline xmlns:sax="http://www.xchain.org/sax/1.0"&gt;
   *   ...
   *   &lt;sax:result system-id="'file:/some/path'"&gt;
   * &lt;/sax:pipeline&gt;
   * </code>
   *
   * <p>To write output to a file path, add the path attribute:</p>
   *
   * <code class="source">
   * &lt;sax:pipeline xmlns:sax="http://www.xchain.org/sax/1.0"&gt;
   *   ...
   *   &lt;sax:result path="'/some/path'"&gt;
   * &lt;/sax:pipeline&gt;
   * </code>
   *
   * <p>To write output to an object in the context, add the select attribute:</p>
   *
   * <code class="source">
   * &lt;sax:pipeline xmlns:sax="http://www.xchain.org/sax/1.0"&gt;
   *   ...
   *   &lt;sax:result select="$result"&gt;
   * &lt;/sax:pipeline&gt;
   * </code>
   *
   * <p>The value of the select attribute must resovle to one of:</p>
   * <ul>
   *   <li>javax.xml.transform.Result</li>
   *   <li>org.xml.sax.ContentHandler</li>
   *   <li>org.w3c.dom.Node</li>
   *   <li>java.io.OutputStream</li>
   *   <li>java.io.Writer</li>
   *   <li>java.io.File</li>
   * </ul>
   *
   * @author Mike Moulton
   * @author Christian Trimble
   * @author Devon Tackett
   * @author Jason Rose
   * @author Josh Kennedy
   */
  @Element(localName = "result")
  public abstract class ResultCommand implements Command {
    public static Logger log = LoggerFactory.getLogger(ResultCommand.class);
  
    /**
     * <p>DEPRICATED: Use system-id instead.  The system id to send the output to.</p>
     * @param context the JXPathContext to evaluate against.
     */
    @Attribute(localName = "systemId", type = AttributeType.JXPATH_VALUE)
    public abstract String getSystemIdDepricated(JXPathContext context)
     throws Exception;
 
   /**
    * <p>Returns true if the systemId attribute has been set.</p>
    * @return true if the systemId attribute has been set, false otherwise.
    */
   public abstract boolean hasSystemIdDepricated();
 
   /**
    * <p>The system id to send output to.</p>
    * @param context the JXPathContext to evaluate against.
    */
   @Attribute(localName="system-id", type = AttributeType.JXPATH_VALUE)
   public abstract String getSystemId(JXPathContext context)
     throws Exception;
 
   /**
    * <p>Returns true if the system-id attribute has been set.</p>
    * @return true if the system-id attribute has been set, false otherwise.
    */
   public abstract boolean hasSystemId();
 
   /**
    * <p>The file path to send output to.</p>
    * @param context the JXPathContext to evaluate against.
    */
   @Attribute(localName = "path", type = AttributeType.JXPATH_VALUE)
   public abstract String getPath(JXPathContext context)
     throws Exception;
 
   /**
    * <p>Returns true if the path attribute has been set.</p>
    * @return true if the path attribute has been set, false otherwise.
    */
   public abstract boolean hasPath();
 
   /**
    * <p>The object to send output to.</p>
    * @param context the JXPathContext to evaluate against.
    */
   @Attribute(localName = "select", type = AttributeType.JXPATH_SELECT_SINGLE_NODE)
   public abstract Object getSelect(JXPathContext context)
     throws Exception;
 
   /**
    * <p>Returns true if the select attribute has been set.</p>
    * @return true if the select attribute has been set, false otherwise.
    */
   public abstract boolean hasSelect();
 
   /**
    * <p>Returns the result for the select attribute.</p>
    * @param context the JXPathContext to evaluate against.
    * @return the correct result object for the type of object selected from the context.
    */
   public Result createResultForSelect(JXPathContext context)
     throws Exception
   {
     Object object = getSelect(context);
 
     if( object == null ) {
       throw new IllegalArgumentException("The selected object cannot be null.");
     }
     // if the object is a result, then use it.
     else if( object instanceof Result ) {
       return (Result) object;
     }
 
     // if the object is a stream, then create a stream source.
     else if( object instanceof OutputStream ) {
       return new StreamResult((OutputStream) object);
     } else if( object instanceof Writer ) {
       return new StreamResult((Writer) object);
     } else if( object instanceof File ) {
       return new StreamResult((File) object);
     }
 
     // if the object is a content handler, then create a sax result.
     else if( object instanceof ContentHandler ) {
       return new SAXResult((ContentHandler) object);
     }
 
     // if the result is a node, then create a dom result.
     else if( object instanceof Node ) {
       return new DOMResult((Node) object);
     }
 
     // we do not how to make a result for this object, so bail out.
     else {
       throw new IllegalArgumentException("The selected result object (" + object.getClass().getName() + ") is not a result object nor is it an output stream.");
     }
   }
 
   /**
    * <p>Returns the Result object for the system-id attribute.</p>
    * @param context the JXPathContext to evaluate against.
    * @return a stream result for the system id.
    */
   public Result createResultForSystemId(JXPathContext context)
     throws Exception
   {
     // set the system id.
     //String systemId = getSystemId(context);
     String systemId = null;
     if( hasSystemId() ) {
       systemId = getSystemId(context);
     }
     else {
       systemId = getSystemIdDepricated(context);
     }
 
     // create a result object for the system id.
     URL url = UrlFactory.getInstance().newUrl(systemId);
 
     // create an output stream for this url.
     OutputStream out = url.openConnection().getOutputStream();
 
     // create a stream result for the output stream.
     StreamResult streamResult = new StreamResult();
     streamResult.setSystemId(systemId);
     streamResult.setOutputStream(out);
 
     return streamResult;
   }
 
   /**
    * <p>Returns the Result object for the path attribute.</p>
    * @param context the JXPathContext to evaluate against.
    * @return a stream result for the path specified.
    */
   public Result createResultForPath(JXPathContext context)
     throws Exception
   {
     // set the system id.
     String path = getPath(context);
 
     // get the file object for the path.
     File file = new File(path);
 
     // create the directories leading up to the path.
     File parentFile = file.getParentFile();
     if( !parentFile.exists() ) {
       parentFile.mkdirs();
     }
 
     // make sure that the file also exists.
     file.createNewFile();
 
     // create an output stream for this url.
     OutputStream out = new FileOutputStream(file);
 
     // create a stream result for the output stream.
     StreamResult streamResult = new StreamResult();
     streamResult.setSystemId(file.toURL().toExternalForm());
     streamResult.setOutputStream(out);
 
     return streamResult;
   }
 
   /**
    * <p>Builds the result object for this element and sets it on the current sax pipeline configuration.</p>
    */
   public boolean execute(JXPathContext context)
     throws Exception
   {
     Result result = null;
 
     if( hasSelect() ) {
       result = createResultForSelect(context);
     } else if( hasSystemId() || hasSystemIdDepricated() ) {
       result = createResultForSystemId(context);
     } else if( hasPath() ) {
       result = createResultForPath(context);
     } else {
       throw new IllegalStateException("The system-id, path or select attribute must be set for the result tag.");
     }
 
     // set the result in the pipeline config's composite stage.
     PipelineCommand.getPipelineConfig().getCompositeStage().setResult(result);
 
     return false;
   }
 }