open Pdfutil

(* We allow \n in titles. *)
let rec split_toc_title_inner a = function
  | '\\'::'n'::r -> rev a :: split_toc_title_inner [] r
  | x::xs -> split_toc_title_inner (x::a) xs
  | [] -> [rev a]

let split_toc_title = split_toc_title_inner []

(* Cpdftype codepoints from a font and UTF8 *)
let of_utf8 f t =
     Pdftext.codepoints_of_utf8 t
  |> option_map (Pdftext.charcode_extractor_of_font_real f)
  |> map char_of_int

(* Cpdftype codepoints from a font and PDFDocEndoding string *)
let of_pdfdocencoding f t =
  of_utf8 f (Pdftext.utf8_of_pdfdocstring t)

(* Typeset a table of contents with given font, font size and title. Mediabox
   (and CropBox) copied from first page of existing PDF. Margin of 50pts inside
   CropBox. Font size of title twice body font size. Null page labels added for
   TOC, others bumped up and so preserved. *)
let typeset_table_of_contents ~font ~fontsize ~title pdf =
  let marks = Pdfmarks.read_bookmarks pdf in
  if marks = [] then (Printf.eprintf "No bookmarks, not making table of contents\n%!"; pdf) else
  let f, fs = (Pdftext.StandardFont (font, Pdftext.WinAnsiEncoding), fontsize) in
  let big = (Pdftext.StandardFont (font, Pdftext.WinAnsiEncoding), fontsize *. 2.) in
  let firstpage = hd (Pdfpage.pages_of_pagetree pdf) in
  let firstpage_papersize, pmaxx, pmaxy =
    let width, height, xmax, ymax =
      match Pdf.parse_rectangle firstpage.Pdfpage.mediabox with
        xmin, ymin, xmax, ymax -> xmax -. xmin, ymax -. ymin, xmax, ymax
    in
      Pdfpaper.make Pdfunits.PdfPoint width height, xmax, ymax
  in
  let firstpage_cropbox =
    match Pdf.lookup_direct pdf "/CropBox" firstpage.Pdfpage.rest with
    | Some r -> Some (Pdf.parse_rectangle r)
    | None -> None
  in
  let labels = Pdfpagelabels.read pdf in
  let lines =
    let refnums = Pdf.page_reference_numbers pdf in
    let fastrefnums = hashtable_of_dictionary (combine refnums (indx refnums)) in
    map
      (fun mark ->
         let label =
           let pnum = Pdfpage.pagenumber_of_target ~fastrefnums pdf mark.Pdfmarks.target in
             try Pdfpagelabels.pagelabeltext_of_pagenumber pnum labels with Not_found -> string_of_int pnum
         in
           [Cpdftype.BeginDest mark.Pdfmarks.target;
            Cpdftype.HGlue {Cpdftype.glen = float mark.Pdfmarks.level *. fontsize *. 2.; Cpdftype.gstretch = 0.};
            Cpdftype.Text (of_pdfdocencoding f mark.Pdfmarks.text);
            Cpdftype.HGlue {Cpdftype.glen = 100.; Cpdftype.gstretch = 0.};
            Cpdftype.Text (of_pdfdocencoding f label);
            Cpdftype.EndDest;
            Cpdftype.NewLine])
      (Pdfmarks.read_bookmarks pdf)
  in
  let toc_pages =
    let title =
      flatten
        (map
          (fun l -> [Cpdftype.Text l; Cpdftype.NewLine])
          (split_toc_title (of_utf8 f title)))
    in
    let lm, rm, tm, bm =
      match firstpage_cropbox with
      | None -> (50., 50., 50., 50.)
      | Some (cminx, cminy, cmaxx, cmaxy) ->
          (cminx +. 50., (pmaxx -. cmaxx) +. 50., cminy +. 50., (pmaxy -. cmaxy) +. 50.)
    in
      Cpdftype.typeset lm rm tm bm firstpage_papersize pdf
        ([Cpdftype.Font big] @ title @
          [Cpdftype.VGlue {glen = fontsize *. 2.; gstretch = 0.};
           Cpdftype.Font (f, fs)] @ flatten lines)
  in
  let toc_pages =
    match firstpage_cropbox with
    | Some (a, b, c, d) ->
        let rect =
          Pdf.Array [Pdf.Real a; Pdf.Real b; Pdf.Real c; Pdf.Real d]
        in
          map
            (fun p -> {p with Pdfpage.rest = Pdf.add_dict_entry p.Pdfpage.rest "/CropBox" rect})
            toc_pages
    | None -> toc_pages
  in
  let original_pages = Pdfpage.pages_of_pagetree pdf in
  let toc_pages_len = length toc_pages in
  let changes = map (fun n -> (n, n + toc_pages_len)) (indx original_pages) in
  let pdf = Pdfpage.change_pages ~changes true pdf (toc_pages @ original_pages) in
  let label =
    {Pdfpagelabels.labelstyle = NoLabelPrefixOnly;
     Pdfpagelabels.labelprefix = None;
     Pdfpagelabels.startpage = 1;
     Pdfpagelabels.startvalue = 1}
  in
  let labels' = label::map (fun l -> {l with Pdfpagelabels.startpage = l.Pdfpagelabels.startpage + toc_pages_len}) labels in
    Pdfpagelabels.write pdf labels';
    pdf