{ lib, stdenv, fetchFromGitHub, fetchpatch, python3Packages }:

stdenv.mkDerivation rec {
  pname = "facedetect";
  version = "0.1";

  src = fetchFromGitHub {
    owner = "wavexx";
    repo = "facedetect";
    rev = "v${version}";
    sha256 = "0mddh71cjbsngpvjli406ndi2x613y39ydgb8bi4z1jp063865sd";
  };

  patches = [
    (fetchpatch {
      name = "python3-support.patch";
      url = "https://gitlab.com/wavexx/facedetect/-/commit/8037d4406eb76dd5c106819f72c3562f8b255b5b.patch";
      sha256 = "1752k37pbkigiwglx99ba9360ahzzrrb65a8d77k3xs4c3bcmk2p";
    })
  ];

  buildInputs = [ python3Packages.python python3Packages.wrapPython ];
  pythonPath = [ python3Packages.numpy python3Packages.opencv4 ];

  dontConfigure = true;

  postPatch = ''
    substituteInPlace facedetect \
      --replace /usr/share/opencv "${python3Packages.opencv4}/share/opencv4"
  '';

  installPhase = ''
    install -v -m644 -D README.rst $out/share/doc/${pname}-${version}/README.rst
    install -v -m755 -D facedetect $out/bin/facedetect
    wrapPythonPrograms
  '';

  meta = with lib; {
    homepage = "https://www.thregr.org/~wavexx/software/facedetect/";
    description = "A simple face detector for batch processing";
    license = licenses.gpl2Plus;
    platforms = platforms.all;
    maintainers = [ maintainers.rycee ];
    mainProgram = "facedetect";
  };
}