abstract class PDF (val fileName:String){
  import SPDF._

  def document: ValDocument
//  lazy val document = _document

  def open:PDF = new PDF(fileName) {
    def document = documentPDF(fileName)
  }

  lazy val documentInfo = document ∘ (_.getDocumentInformation)
  lazy val documentCatalog = document ∘ (_.getDocumentCatalog)
  lazy val numberOfPages = document ∘ (_.getNumberOfPages)
  lazy val title = documentInfo.toOption ∘ (_.getTitle()) | "Unknow"
  lazy val allPages = documentCatalog ∘ (_.getAllPages())

  def close:PDF = {
    val d = document
    new PDF(fileName) {
      def document:ValDocument = document flatMap closePDF
    }
  }

  def getPage(o:PDOutlineItem):Int =
    document.doOrElse((d) => getPage(o.findDestinationPage(d)))(-1)

  def getPage(p:PDPage):Int = allPages.toOption ∘ (_.indexOf(p)) | -1
}