class FileMigration extends Migration {
  public function __construct() {
    // Always call the parent constructor first for basic setup
    parent::__construct();

    // Provide a basic description of what this migration does
    $this->description = t('Migrate Files.');
    
    $query = db_select('Drupal_Files', 'f');
    $query->addField('f', 'AttachmentID');
    $query->addField('f', 'NodeAliasPath');
    $query->addField('f', 'AttachmentMimeType');
    $query->addField('f', 'AttachmentExtension');
    $query->addField('f', 'Caption');
    $query->condition('f.AttachmentExtension', array('.jpg', '.png'));
    
    
    // Create a MigrateSource object, which manages retrieving the input data.
    $this->source = new MigrateSourceSQL($query, $query->getFields(), null, array('map_joinable' => false));  

    // Set up our destination - terms in the category vocabulary
    $this->destination = new MigrateDestinationMedia('image', array('preserve_files' => TRUE));

    $this->map = new MigrateSQLMap($this->machineName,
      array(
        'AttachmentID' => array('type' => 'int',
                         'unsigned' => TRUE,
                         'not null' => TRUE,
                         'description' => 'Kentico Attachment ID',
                        )
      ),
      MigrateDestinationMedia::getKeySchema()
    );
    
    $this->addFieldMapping('filename', 'AttachmentName');
    $this->addFieldMapping('filemime', 'AttachmentMimeType');
    $this->addFieldMapping('uri', 'NodeAliasPath');
    $this->addFieldMapping('status')->defaultValue(1);
    $this->addFieldMapping('field_caption', 'Caption');
    
  }
  
}