/* 
    * Copyright (c) 2007, Fraunhofer-Gesellschaft
    * All rights reserved.
    * 
    * Redistribution and use in source and binary forms, with or without
    * modification, are permitted provided that the following conditions are
    * met:
    * 
    * (1) Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the disclaimer at the end.
   *     Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in
   *     the documentation and/or other materials provided with the
   *     distribution.
   * 
   * (2) Neither the name of Fraunhofer nor the names of its
   *     contributors may be used to endorse or promote products derived
   *     from this software without specific prior written permission.
   * 
   * DISCLAIMER
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *  
   */
  package org.ogf.graap.wsag.server.actions.impl;
  
  import java.io.BufferedWriter;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.text.MessageFormat;
  import java.util.Date;
  import java.util.Properties;
  
  import org.apache.log4j.Logger;
  import org.apache.velocity.Template;
  import org.apache.velocity.VelocityContext;
  import org.apache.velocity.app.Velocity;
  import org.apache.velocity.exception.ResourceNotFoundException;
  import org.apache.xmlbeans.XmlDateTime;
  import org.ogf.graap.wsag.api.logging.LogMessage;
  
  /**
   * Default implementation to load files from the classpath an process these files as Velocity templates.
   * Additional parameters can be specified, which can be used in the Velocity macros defined in the file.
   * 
   * @author owaeld
   * 
   */
  public class FileTemplate
  {
  
      private static final Logger LOG = Logger.getLogger( FileTemplate.class );
  
      /**
       * Velocity properties filename. Applications may provide a custom properties file in order to overwrite
       * default configuration. If this file does not exist in the classpath the default velocity configuration
       * is used.
       */
      public static final String VELOCITY_PROPERTIES_FILE = "/wsag4j-velocity.properties";
  
      /**
       * Default velocity properties filename.
       */
      public static final String VELOCITY_PROPERTIES_FILE_DEFAULT = "/wsag4j-velocity.properties.default";
  
      private VelocityContext context;
  
      private Template template;
  
      static
      {
          Properties properties = new Properties();
  
          try
          {
              //
              // try to load user provided velocity properties if available in the classpath, otherwise use
              // default properties
              //
              InputStream in = FileTemplate.class.getResourceAsStream( VELOCITY_PROPERTIES_FILE );
              if ( in == null )
              {
                  in = FileTemplate.class.getResourceAsStream( VELOCITY_PROPERTIES_FILE_DEFAULT );
              }
  
              properties.load( in );
  
              //
             // set Velocity log4j logger name
             //
             properties.setProperty( "runtime.log.logsystem.log4j.logger", FileTemplate.class.getName() );
 
         }
         catch ( Exception e )
         {
             String message = "Failed to load velocity properties file [{0}]. Reason: {1}";
             LOG.error( LogMessage.getMessage( message, VELOCITY_PROPERTIES_FILE, e.getMessage() ) );
             LOG.error( "Resource loockup in WSAG4J classpath disabled." );
             LOG.debug( e );
         }
 
         try
         {
             Velocity.init( properties );
         }
         catch ( Exception e )
         {
             LOG.error( "Failed to initialize velocity template engine.", e );
             LOG.error( "Resource loockup in WSAG4J classpath disabled." );
         }
 
     }
 
     /**
      * Creates a new file template for the given file name. The file with the specified name is resolved from
      * the classpath.
      * 
      * @param filename
      *            the file name
      */
     public FileTemplate( String filename )
     {
         try
         {
             this.context = new VelocityContext();
 
             String currDate = XmlDateTime.Factory.newValue( new Date() ).getStringValue();
             addParameter( "currentTime", currDate );
 
             //
             // avoid escaping all the XPath expression
             //
             addParameter( "this", "$this" );
 
             template = Velocity.getTemplate( filename );
         }
         catch ( ResourceNotFoundException e )
         {
             LOG.error( MessageFormat.format( "error loading template file [{0}]", filename ) );
             LOG.error( e.getMessage() );
         }
         catch ( Exception e )
         {
             LOG.error( MessageFormat.format( "error processing template file [{0}]", filename ) );
             LOG.error( e.getMessage() );
         }
     }
 
     /**
      * Adds a new parameter to the Velocity context. Parameters can be accessed in the template by its key.
      * 
      * @param key
      *            the parameter name
      * 
      * @param value
      *            the parameter value
      */
     public void addParameter( String key, Object value )
     {
         context.put( key, value );
     }
 
     /**
      * Processes the file template as Velocity template.
      * 
      * @param out
      *            the {@link OutputStream} where the result is written to
      */
     public void processTemplate( OutputStream out )
     {
         try
         {
             BufferedWriter writer = new BufferedWriter( new OutputStreamWriter( out ) );
 
             if ( template != null )
             {
                 template.merge( context, writer );
             }
 
             writer.flush();
             writer.close();
         }
         catch ( Exception ex )
         {
             LOG.error( "error processing output for template:" );
             LOG.error( ex.getMessage() );
         }
     }
 }