/*
    *  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.directory.api.ldap.model.schema.syntaxCheckers;
  
  
  import org.apache.directory.api.ldap.model.constants.SchemaConstants;
  import org.apache.directory.api.ldap.model.schema.SyntaxChecker;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * A SyntaxChecker which verifies that a value is a Jpeg according to RFC 4517.
   * 
   * The JFIF (Jpeg File Interchange Format) specify that a jpeg image starts with
   * the following bytes :
   * 0xFF 0xD8 (SOI, Start Of Image)
   * 0xFF 0xE0 (App0 for JFIF) or 0xDD 0xE1 (App1 for Exif)
   * 0xNN 0xNN (Header length)
   * "JFIF\0" (JFIF string with an ending \0)
   * some other bytes which are related to the image.
   * 
   * We will check for those 11 bytes, except the length.
   * 
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  @SuppressWarnings("serial")
  public class JpegSyntaxChecker extends SyntaxChecker
  {
      /** A logger for this class */
      private static final Logger LOG = LoggerFactory.getLogger( JpegSyntaxChecker.class );
  
      /**
       * Creates a new instance of JpegSyntaxChecker.
       */
      public JpegSyntaxChecker()
      {
          super( SchemaConstants.JPEG_SYNTAX );
      }
  
  
      /**
       * {@inheritDoc}
       */
      public boolean isValidSyntax( Object value )
      {
          if ( value == null )
          {
              LOG.debug( "Syntax invalid for 'null'" );
              return false;
          }
  
          // The value must be a byte array
          if ( !( value instanceof byte[] ) )
          {
              LOG.debug( "Syntax invalid for '{}'", value );
              return false;
          }
  
          byte[] bytes = ( byte[] ) value;
  
          // The header must be at least 11 bytes long
          if ( bytes.length < 11 )
          {
              LOG.debug( "Syntax invalid for '{}'", value );
              return false;
          }
  
          if ( ( bytes[0] == ( byte ) 0x00FF ) // SOI
              && ( bytes[1] == ( byte ) 0x00D8 )
              && ( bytes[2] == ( byte ) 0x00FF ) ) // APP0 or APP1
          {
              if ( bytes[3] == (byte)0x00E0 )
              {
                  // JFIF format
                  if ( ( bytes[6] == 'J' ) // JFIF
                      && ( bytes[7] == 'F' ) // JFIF
                      && ( bytes[8] == 'I' ) // JFIF
                      && ( bytes[9] == 'F' )
                      && ( bytes[10] == 0x00 ) ) // \0
                  {
                      LOG.debug( "Syntax valid for '{}'", value );
                     return true;
                 }
             }
             else if ( bytes[3] == (byte)0x00E1 )
             {
                 // Exif format
                 if ( ( bytes[6] == 'E' )   // Exif
                     && ( bytes[7] == 'x' ) // Exif
                     && ( bytes[8] == 'i' ) // Exif
                     && ( bytes[9] == 'f' ) // Exif
                     && ( bytes[10] == 0x00 ) ) // \0
                 {
                     LOG.debug( "Syntax valid for '{}'", value );
                     return true;
                 }
             }
         }
 
         LOG.debug( "Syntax invalid for '{}'", value );
         return false;
     }
 }