{stdenv, fetchFromGitHub, ocamlPackages, fontschumachermisc, xset, makeWrapper, ncurses
, enableX11 ? true}:

let inherit (ocamlPackages) ocaml lablgtk; in

stdenv.mkDerivation (rec {

  pname = "unison";
  version = "2.51.2";
  src = fetchFromGitHub {
    owner = "bcpierce00";
    repo = "unison";
    rev = "v${version}";
    sha256 = "1bykiyc0dc5pkw8x370qkg2kygq9pq7yqzsgczd3y13b6ivm4sdq";
  };

  buildInputs = [ ocaml makeWrapper ncurses ];

  preBuild = (if enableX11 then ''
    sed -i "s|\(OCAMLOPT=.*\)$|\1 -I $(echo "${lablgtk}"/lib/ocaml/*/site-lib/lablgtk2)|" src/Makefile.OCaml
  '' else "") + ''
  echo -e '\ninstall:\n\tcp $(FSMONITOR)$(EXEC_EXT) $(INSTALLDIR)' >> src/fsmonitor/linux/Makefile
  '';

  makeFlags = [
    "INSTALLDIR=$(out)/bin/"
    "UISTYLE=${if enableX11 then "gtk2" else "text"}"
  ] ++ stdenv.lib.optional (!ocaml.nativeCompilers) "NATIVE=false";

  patches = [
    # NOTE: Only needed until Unison 2.51.3 is released!
    ./4.08-compatibility.patch
    ./lablgtk.patch
  ];

  preInstall = "mkdir -p $out/bin";

  postInstall = if enableX11 then ''
    for i in $(cd $out/bin && ls); do
      wrapProgram $out/bin/$i \
        --run "[ -n \"\$DISPLAY\" ] && (${xset}/bin/xset q | grep -q \"${fontschumachermisc}\" || ${xset}/bin/xset +fp \"${fontschumachermisc}/lib/X11/fonts/misc\")"
    done
  '' else "";

  dontStrip = !ocaml.nativeCompilers;

  meta = {
    homepage = https://www.cis.upenn.edu/~bcpierce/unison/;
    description = "Bidirectional file synchronizer";
    license = stdenv.lib.licenses.gpl3Plus;
    maintainers = with stdenv.lib.maintainers; [viric];
    platforms = with stdenv.lib.platforms; unix;
  };

})