{
  stdenv,
  lib,
  fetchFromGitHub,
  unstableGitUpdater,

  # Docs cause an immense increase in build time, up to 2 additional hours
  withDocs ? false,
  dosbox,
  mesa,
  ghostscript,

  # GUI tools aren't ported to non-MS platforms, building them usually just wastes time
  withGUI ? stdenv.hostPlatform.isWindows,
}:

stdenv.mkDerivation (finalAttrs: {
  pname = "${finalAttrs.passthru.prettyName}-unwrapped";
  # nixpkgs-update: no auto update
  version = "0-unstable-2025-11-15";

  src = fetchFromGitHub {
    owner = "open-watcom";
    repo = "open-watcom-v2";
    rev = "fe2ddbd2e5833a85d9ccd3937b304f3f41e44f98";
    hash = "sha256-jv7d5DopGZDnVFQX/t0D9cZSTwgMvcb4kqCnLJSWmNI=";
  };

  postPatch = ''
    patchShebangs *.sh
  ''
  # Patch references to current time & date into SOURCE_DATE_EPOCH-respecting ones
  + ''
    substituteInPlace bld/wipfc/configure \
      --replace-fail '`date ' '`date -ud "@$SOURCE_DATE_EPOCH" '

    substituteInPlace bld/watcom/h/banner.h \
      --replace-fail '__DATE__' "\"$(date -ud "@$SOURCE_DATE_EPOCH" +'%b %d %Y')\"" \
      --replace-fail '__TIME__' "\"$(date -ud "@$SOURCE_DATE_EPOCH" +'%T')\""

    substituteInPlace build/makeinit \
      --replace-fail '$+$(%__CYEAR__)$-' "$(date -ud "@$SOURCE_DATE_EPOCH" +'%Y')"
  ''
  # (SDL? DOSBox?) needs OpenGL now, and that doesn't seem to play nicely anymore with the dummy driver
  + ''
    substituteInPlace build/mif/wgmlcmd.mif \
      --replace-fail 'SDL_VIDEODRIVER=dummy' 'SDL_VIDEODRIVER=offscreen'
  ''
  + lib.optionalString (!stdenv.hostPlatform.isDarwin) ''
    substituteInPlace build/mif/local.mif \
      --replace-fail '-static' ""
  '';

  nativeBuildInputs = lib.optionals withDocs [
    dosbox # running prebuilt WGML tool to create docs
    ghostscript
    mesa.llvmpipeHook # DOSBox doesn't seem to launch without OpenGL available, even on SDL dummy platform
  ];

  configurePhase = ''
    runHook preConfigure

    export OWROOT=$(realpath $PWD)
    export OWTOOLS=${
      if stdenv.cc.isClang then
        "CLANG"
      else if stdenv.cc.isGNU then
        "GCC"
      else
        throw "Don't know what compiler ID to use for ${stdenv.cc.name} in open-watcom-v2 build"
    }
    export OWDOCBUILD=${if withDocs then "1" else "0"}
    export OWGHOSTSCRIPTPATH=${lib.optionalString withDocs "${lib.makeBinPath [ ghostscript ]}"}
    export OWGUINOBUILD=${if withGUI then "0" else "1"}
    export OWNOBUILD=
    export OWDISTRBUILD=0
    export OWDOSBOX=${lib.getExe dosbox}
    export OWVERBOSE=0
    export OWRELROOT=$out

    source cmnvars.sh

    runHook postConfigure
  '';

  buildPhase = ''
    runHook preBuild

    ./build.sh build

    runHook postBuild
  '';

  installPhase = ''
    runHook preInstall

    ./build.sh cprel

    runHook postInstall
  '';

  # Stripping breaks many tools
  dontStrip = true;

  passthru = {
    prettyName = "open-watcom-v2";
    updateScript = unstableGitUpdater {
      url = "https://github.com/open-watcom/open-watcom-v2.git";
      # no numerical releases, monthly "YYYY-MM-DD-Build" tags and daily "Current-build", "Last-CI-build" & "Coverity-scan" retagging
      hardcodeZeroVersion = true;
    };
  };

  meta = {
    description = "V2 fork of the Open Watcom suite of compilers and tools";
    longDescription = ''
      A fork of Open Watcom: A C/C++/Fortran compiler and assembler suite
      targeting a multitude of architectures (x86, IA-32, Alpha AXP, MIPS,
      PowerPC) and operating systems (DOS, OS/2, Windows, Linux).

      Main differences from Open Watcom 1.9:

      - New two-phase build system - Open Watcom can be built by the host's
        native C/C++ compiler or by itself
      - Code generator properly initializes pointers by DLL symbol addresses
      - DOS tools now support long file names (LFN) if appropriate LFN driver
        is loaded by DOS
      - Open Watcom is ported to 64-bit hosts (Win64, Linux x64)
      - Librarian supports x64 CPU object modules and libraries
      - RDOS 32-bit C run-time compact memory model libraries are fixed
      - Resource compiler and Resource editors support Win64 executables
      - Open Watcom text editor is now self-contained, it can be used as
        standalone tool without any requirements for any additional files or
        configuration
      - Broken C++ compiler pre-compiled header template support is fixed
      - Many C++ compiler crashes are fixed
      - Debugger has no length limit for any used environment variable
    ''
    + lib.optionalString (!withDocs) ''

      The documentation has been excluded from this build for build time reasons. It can be found here:
      https://github.com/open-watcom/open-watcom-v2/wiki/Open-Watcom-Documentation
    '';
    homepage = "https://open-watcom.github.io";
    license = lib.licenses.watcom;
    platforms = with lib.platforms; windows ++ unix;
    badPlatforms = lib.platforms.riscv ++ [
      "powerpc64-linux"
      "powerpc64le-linux"
      "mips64el-linux"
    ];
    maintainers = with lib.maintainers; [ OPNA2608 ];
  };
})