{ lib
, stdenv
, fetchFromGitHub
, runCommand
, libtool
, cmake
, zlib
, bzip2
, enableRexx ? stdenv.isLinux, regina
}:
let
  herculesCpu =
    if stdenv.hostPlatform.isx86 then "x86"
    else stdenv.hostPlatform.qemuArch;
  herculesBits = if stdenv.hostPlatform.is32bit then "32" else "64";

  herculesLibDir =
    if stdenv.hostPlatform.isx86 then "lib"
    else "lib/${herculesCpu}";

  mkExtPkg = depName: attrFn: (stdenv.mkDerivation {
    pname = "hercules-${depName}";

    postPatch = ''
      patchShebangs build
      sed -i build \
        -e "s%_tool=.*$%_tool=${cmake}/bin/cmake%" \
        -e "s/CPUS=.*$/CPUS=$NIX_BUILD_CORES/"
    '';

    dontUseCmakeConfigure = true;

    buildPhase = ''
      mkdir ../build $out
      # In source builds are not allowed.
      cd ../build
      ../source/build \
        --pkgname ${depName} \
        --cpu ${herculesCpu} \
        --arch ${herculesBits} \
        --install "$out"
    '';

    nativeBuildInputs = [ cmake ];

    enableParallelBuilding = true;

    meta = with lib; {
      description = "Hercules ${depName} library";
      license = lib.licenses.free; # Mixture of Public Domain, ICU (MIT compatible) and others
      maintainers = with maintainers; [ anna328p vifino ];
    };
  }).overrideAttrs (default: attrFn default);


  crypto = mkExtPkg "crypto" (default: {
    version = "1.0.0";
    src = fetchFromGitHub {
      owner = "SDL-Hercules-390";
      repo = "crypto";
      rev = "a5096e5dd79f46b568806240c0824cd8cb2fcda2";
      hash = "sha256-VWjM8WxPMynyW49Z8U/r6SsF7u7Xbk7Dd0gR35lIw28=";
    };
  });

  decNumber = mkExtPkg "decNumber" (default: {
    version = "3.68.0";
    src = fetchFromGitHub {
      owner = "SDL-Hercules-390";
      repo = "decNumber";
      rev = "3aa2f4531b5fcbd0478ecbaf72ccc47079c67280";
      hash = "sha256-PfPhnYUSIw1sYiGRM3iHRTbHHbQ+sK7oO12pH/yt+MQ=";
    };
  });

  softFloat = mkExtPkg "SoftFloat" (default: {
    version = "3.5.0";
    src = fetchFromGitHub {
      owner = "SDL-Hercules-390";
      repo = "SoftFloat";
      rev = "4b0c326008e174610969c92e69178939ed80653d";
      hash = "sha256-DEIT5Xk6IqUXCIGD2Wj0h9xPOR0Mid2Das7aKMQMDaM=";
    };
  });

  telnet = mkExtPkg "telnet" (default: {
    version = "1.0.0";
    src = fetchFromGitHub {
      owner = "SDL-Hercules-390";
      repo = "telnet";
      rev = "729f0b688c1426018112c1e509f207fb5f266efa";
      hash = "sha256-ED0Cl+VcK6yl59ShgJBZKy25oAFC8eji36pNLwMxTM0=";
    };
  });

  extpkgs = runCommand "hercules-extpkgs" {} ''
    OUTINC="$out/include"
    OUTLIB="$out/${herculesLibDir}"
    mkdir -p "$OUTINC" "$OUTLIB"
    for dep in "${crypto}" "${decNumber}" "${softFloat}" "${telnet}"; do
      ln -s $dep/include/* "$OUTINC"
      ln -s $dep/${herculesLibDir}/* "$OUTLIB"
    done
  '';
in
stdenv.mkDerivation rec {
  pname = "hercules";
  version = "4.6";

  src = fetchFromGitHub {
    owner = "SDL-Hercules-390";
    repo = "hyperion";
    rev = "Release_${version}";
    hash = "sha256-ZhMTun6tmTsmIiFPTRFudwRXzWydrih61RsLyv0p24U=";
  };

  postPatch = ''
    patchShebangs _dynamic_version
  '';

  nativeBuildInputs = [ libtool ];
  buildInputs = [
    (lib.getOutput "lib" libtool)
    zlib
    bzip2
    extpkgs
  ] ++ lib.optionals enableRexx [
    regina
  ];

  configureFlags = [
    "--enable-extpkgs=${extpkgs}"
    "--without-included-ltdl"
    "--enable-ipv6"
    "--enable-cckd-bzip2"
    "--enable-het-bzip2"
  ] ++ lib.optionals enableRexx [
    "--enable-regina-rexx"
  ];

  meta = with lib; {
    homepage = "https://sdl-hercules-390.github.io/html/";
    description = "IBM mainframe emulator";
    longDescription = ''
      Hercules is an open source software implementation of the mainframe
      System/370 and ESA/390 architectures, in addition to the latest 64-bit
      z/Architecture. Hercules runs under Linux, Windows, Solaris, FreeBSD, and
      Mac OS X.
    '';
    license = licenses.qpl;
    maintainers = with maintainers; [ anna328p vifino ];
  };
}