(* The program should be able to read a PPM in raw or plain format,
   with any valid Maxval. The output will be a grayscale raw PPM with
   Maxval=255.

   Compile with "myatscc bitmap_read_ppm_task_program.dats", which
   should give you a program named "bitmap_read_ppm_task_program". *)

(*

##myatsccdef=\
patscc -std=gnu2x -g -O2 -DATS_MEMALLOC_LIBC \
  -o $fname($1) $1 \
  bitmap{,_{{read,write}_ppm,grayscale}}_task.{s,d}ats

*)

#include "share/atspre_staload.hats"

staload "bitmap_task.sats"
staload "bitmap_read_ppm_task.sats"
staload "bitmap_write_ppm_task.sats"
staload "bitmap_grayscale_task.sats"

staload _ = "bitmap_task.dats"
staload _ = "bitmap_read_ppm_task.dats"
staload _ = "bitmap_write_ppm_task.dats"
staload _ = "bitmap_grayscale_task.dats"

implement
main0 (argc, argv) =
  let
    val args = listize_argc_argv (argc, argv)
    val nargs = length args

    val inpf =
      if nargs < 2 then
        stdin_ref
      else if args[1] = "-" then
        stdin_ref
      else
        fileref_open_exn (args[1], file_mode_r)
    val pix_opt = pixmap_read_ppm<rgb24> inpf
    val () = fileref_close inpf
  in
    case+ pix_opt of
    | ~ None_vt () =>
      begin
        free args;
        println! ("For some reason, I failed to read the image.");
        exit 1
      end
    | ~ Some_vt @(pfgc1 | pix1) =>
      let
        val @(pfgc2 | pix2) = pixmap_convert<rgb24,gray8> pix1
        val () = free (pfgc1 | pix1)
        val @(pfgc3 | pix3) = pixmap_convert<gray8,rgb24> pix2
        val () = free (pfgc2 | pix2)

        val outf =
          if nargs < 3 then
            stdout_ref
          else if args[2] = "-" then
            stdout_ref
          else
            fileref_open_exn (args[2], file_mode_w)
        val success = pixmap_write_ppm<rgb24> (outf, pix3)
        val () = fileref_close outf

        val () = free (pfgc3 | pix3)
      in
        free args;
        if ~success then
          begin
            println! ("For some reason, ",
                      "I failed to write a new image.");
            exit 2
          end
      end
  end