PRMigration

class PRMigration extends Migration {
  public function __construct() {
    parent::__construct();
    $this->map = new MigrateSQLMap($this->machineName,
        array(
          'id' => array(
            'type' => 'int',
            'not null' => TRUE,
            'description' => 'Press Release ID',
          )
        ),
        MigrateDestinationNode::getKeySchema()
      );

    $query = Database::getConnection('default', 'secondary')
             ->select('releases', 'r')
             ->fields('r', array('id', 'title', 'released_at', 'synopsis', 'body',
                 'never_post', 'position', 'writer', 'created_by', 'updated_by',
                 'created_at', 'updated_at', 'subtitle', 'contact_id',
                 'version', 'deleted_at'));

    $source_fields = array(
      'links' => t('Related links'),
      'source_images' => t('Image assets attached ot this press release.'),
    );
    $this->source = new MigrateSourceSQL($query, $source_fields, NULL, array('map_joinable' => FALSE));
    // Using the default Node destination class.
    $this->destination = new MigrateDestinationNode('press_release');

    ///////////////////////////////////////////////////////
    // Mapped fields
    ///////////////////////////////////////////////////////
    $file_args = MigrateFileFieldHandler::arguments(NULL, 'file_blob', FILE_EXISTS_RENAME);
    $this->addFieldMapping('field_image', 'source_images')
         ->arguments($file_args);

  }
  public function prepareRow($row) {
    // Pull in the associated images for this release.
    $source_db = Database::getConnection('default', 'secondary');
    $query = $source_db
             ->select('assets', 'a')
             ->fields('a', array('id', 'filename', 'content_type', 'alt', 'caption',
                 'photo_credit', 'size', 'height', 'width', 'parent_id', 'thumbnail',
                 'db_file_id', 'created_by', 'updated_by', 'created_at', 'updated_at'));
    $query->innerJoin('db_files', 'dbf', 'a.db_file_id = dbf.id');
    $query->addField('dbf', 'data');
    $query->leftJoin('assignments', 'assign', 'a.id = assign.asset_id');
    $query->condition('assign.category_type', 'Release', '=');
    $query->condition('assign.category_id', $row->id, '=');
    $results = $query->execute();

    $images = array();

    foreach ($results as $row) {
      $image_information = array(
        'path' => $row->filename,
        'alt' => $row->alt,
        'title' => $row->caption,
      );
      $images[] = drupal_json_encode($image_information);

    }

    $row->source_images = $images;
    return TRUE;
  }
}

class PRAssetMigration extends Migration {
  public function __construct() {
    parent::__construct();

    $this->map = new MigrateSQLMap($this->machineName,
        array(
          'id' => array(
            'type' => 'int',
            'not null' => TRUE,
            'description' => 'Asset ID',
          )
        ),
        MigrateDestinationNode::getKeySchema()
      );

    // Select all the fields from the 'assets' table, and join it with the related 'data' field in db_files.
    $source_db = Database::getConnection('default', 'secondary');
    $query = $source_db
             ->select('assets', 'a')
             ->fields('a', array('id', 'filename', 'content_type', 'alt', 'caption',
                 'photo_credit', 'size', 'height', 'width', 'parent_id', 'thumbnail',
                 'db_file_id', 'created_by', 'updated_by', 'created_at', 'updated_at'));
    $query->innerJoin('db_files', 'dbf', 'a.db_file_id = dbf.id');
    $query->addField('dbf', 'data');
    $count_query = $source_db->select('assets', 'a');
    $count_query->addExpression('COUNT(id)', 'cnt');

    // User the simplified count query so it doesn't have to do the join to get the count.
    $this->source = new MigrateSourceSQL($query, array(), $count_query, array('map_joinable' => FALSE));
    $this->destination = new MigrateDestinationFile(MigrateDestinationFile::options(FALSE, NULL, NULL, NULL, FALSE, TRUE));

    ///////////////////////////////////////////////////////
    // Mapped fields
    ///////////////////////////////////////////////////////
    $this->addSimpleMappings(array());

    $this->addFieldMapping('contents', 'data');
    $this->addFieldMapping('filename', 'filename')
         ->dedupe('file_managed', 'filename');
    $this->addFieldMapping('filemime', 'content_type');
    // Since we don't care about the history of the source files, use updated_at instead of created_at.
    $this->addFieldMapping('timestamp', 'updated_at');


    ///////////////////////////////////////////////////////
    // Unmapped Source fields
    ///////////////////////////////////////////////////////
    $this->addUnmigratedSources(array('db_file_id', 'created_by', 'updated_by', 'created_at'));

    ///////////////////////////////////////////////////////
    // Unmapped destination fields
    ///////////////////////////////////////////////////////
    $this->addUnmigratedDestinations(array('uri', 'path', 'uid'));


  }
}