CairoHacks.env <- new.env()
CairoHacks.env$device_set_up <- FALSE
CairoHacks.env$current_page <- 0

##' Make a bookmark for a PDF for later saving to the pdf with
##' \code{write.pdf.bookmarks}
##'
##' 
##' @title make.bookmark
##' @param text Text of bookmark to create
##' @param level Optional bookmark level which defaults to 1. This
##' enables you to have headings and sub-headings and so forth, simply
##' by increasing the number passed.
##' @param page Optional page number to write the bookmark to. If you
##' are using a Cairo device, this is automatically set for you to be
##' the page which you are currently writing to.
##' @return list of bookmarks to be passed to write.bookmarks or
##' further calls to save.bookmark
##' @author Don Armstrong <don@@donarmstrong.com>
##' @export
##' @examples
##' CairoPDF(file="example.pdf",onefile=TRUE)
##' plot(y~x,data.frame(x=1:5,y=1:5))
##' bookmarks <- make.pdf.bookmark("First plot")
##' plot(y~x,data.frame(x=1:5,y=1:5))
##' bookmarks <- bookmarks + make.pdf.bookmark("Second plot")
##' dev.off()
##' write.pdf.bookmarks(file="example.pdf",bookmarks)
make.pdf.bookmark <- function(text,level=1,page=NULL) {
    if (!CairoHacks.env$device_set_up) {
        Cairo.onSave(device = grDevices::dev.cur(),
                     onSave=function(device,page){
                         ch <- getNamespace("CairoHacks")
                         print(ls(envir=ch))
                         assign("current_page",
                                page,
                                envir=ch[["CairoHacks.env"]])
                     })
        CairoHacks.env$device_set_up <- TRUE
    }
    if (missing(page)|| is.null(page)) {
        page <- CairoHacks.env$current_page
    }
    p <- structure(list(
        bookmarks=list(
            list(text=text,
                 level=level,
                 page=page))
        ), class = c("CairoHacks_bookmark"))
    return(p)
}
##' Add additional bookmarks to a bookmark
##'
##' Given a bookmarks object created with make.pdf.bookmark, add more
##' bookmarks to it.
##' @title + CairoHacks_bookmark
##' @param b1 An object of class CairoHacks_bookmark.
##' @param b2 An object of class CairoHacks_bookmark
##' @export
##' @method + CairoHacks_bookmark
##' @author Don Armstrong <don@@donarmstrong.com>
"+.CairoHacks_bookmark" <- function(b1,b2) {
    b1[["bookmarks"]] <-
        c(b1[["bookmarks"]],
          b2[["bookmarks"]])
    b1
}
##' Write saved bookmarks to the PDF file which was generated
##'
##' Given a set of bookmarks generated with make.pdf.bookmark, write
##' them out to a PDF file using pdftk.
##' @title write.pdf.bookmarks
##' @param file file name of pdf which was saved to disk
##' @param bookmarks list of bookmarks
##' @return list of bookmarks
##' @author Don Armstrong <don@@donarmstrong.com>
##' @export
write.pdf.bookmarks <- function(file,bookmarks) {
    pdf.bookmarks <- ""
    print(bookmarks[["bookmarks"]])
    for (bookmark in 1:length(bookmarks[["bookmarks"]])) {
        pdf.bookmarks <-
            paste0(pdf.bookmarks,
                   "BookmarkBegin\n",
                   "BookmarkTitle: ",bookmarks[["bookmarks"]][[bookmark]][["text"]],"\n",
                   "BookmarkLevel: ",bookmarks[["bookmarks"]][[bookmark]][["level"]],"\n",
                   "BookmarkPageNumber: ",bookmarks[["bookmarks"]][[bookmark]][["page"]],"\n")
    }
    temp.pdf <- tempfile(pattern=basename(file))
    temp.pdf.info <- tempfile(pattern=paste0(basename(file),"info_utf8"))
    cat(file=temp.pdf.info,pdf.bookmarks)
    system2("pdftk",c(file,'update_info_utf8',temp.pdf.info,'output',temp.pdf))
    if (file.exists(temp.pdf)) {
        file.rename(temp.pdf,file)
    } else {
        stop("unable to properly create bookmarks")
    }
    invisible(bookmarks)
}