{ stdenv
, lib
, fetchFromGitHub
, unstableGitUpdater
, dosbox

# Docs cause an immense increase in build time, up to 2 additional hours
, withDocs ? false
, ghostscript
, withGUI ? false
}:

stdenv.mkDerivation rec {
  pname = "${passthru.prettyName}-unwrapped";
  version = "unstable-2022-08-02";

  src = fetchFromGitHub {
    owner = "open-watcom";
    repo = "open-watcom-v2";
    rev = "4bdb73995b871982dd106838296903701ded29c2";
    sha256 = "sha256-Ay/f+gnj8EklN8T/uP0a+Zji6HEHAoPLdkrSTQaC9Rs=";
  };

  postPatch = ''
    patchShebangs *.sh

    for dateSource in cmnvars.sh bld/wipfc/configure; do
      substituteInPlace $dateSource \
        --replace '`date ' '`date -ud "@$SOURCE_DATE_EPOCH" '
    done

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

    substituteInPlace build/makeinit \
      --replace '%__CYEAR__' '%OWCYEAR'
  '' + lib.optionalString (!stdenv.hostPlatform.isDarwin) ''
    substituteInPlace build/mif/local.mif \
      --replace '-static' ""
  '';

  nativeBuildInputs = [ dosbox ]
    ++ lib.optional withDocs ghostscript;

  configurePhase = ''
    runHook preConfigure

    export OWROOT=$(realpath $PWD)
    export OWTOOLS=${if stdenv.cc.isClang then "CLANG" else "GCC"}
    export OWDOCBUILD=${if withDocs then "1" else "0"}
    export OWGHOSTSCRIPTPATH=${lib.optionalString withDocs "${ghostscript}/bin"}
    export OWGUINOBUILD=${if withGUI then "0" else "1"}
    export OWNOBUILD=
    export OWDISTRBUILD=0
    export OWDOSBOX=${dosbox}/bin/dosbox
    export OWVERBOSE=0
    export OWRELROOT=$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";
    };
  };

  meta = with lib; {
    description = "The 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 = licenses.watcom;
    platforms = [ "x86_64-linux" "i686-linux" "x86_64-darwin" "x86_64-windows" "i686-windows" ];
    maintainers = with maintainers; [ OPNA2608 ];
  };
}