{
  lib,
  stdenv,
  fetchFromGitHub,
  haskellPackages,
  ghc,
  makeWrapper,
  glibcLocales,
  # Optional: build only specific languages (comma-separated, e.g., "Eng,Swe,Ger")
  languages ? null,
  # Optional: build mode - "present", "alltenses", or "both"
  mode ? "both",
}:

let
  # Build the language flag if languages are specified
  langFlag = if languages != null then "--langs=${languages}" else "";

  # Build the mode flags
  modeFlags =
    if mode == "present" then
      "present"
    else if mode == "alltenses" then
      "alltenses"
    else
      ""; # both is default
in

stdenv.mkDerivation rec {
  pname = "gf-rgl";
  version = "20250812";

  src = fetchFromGitHub {
    owner = "GrammaticalFramework";
    repo = "gf-rgl";
    rev = version;
    hash = "sha256-rqN5MV/XxChXC+Vs4aLIhRtyPQZNk0LQZ2TCdbd6wUw=";
  };

  nativeBuildInputs = [
    haskellPackages.gf
    ghc
    makeWrapper
    glibcLocales
  ];

  # Disable parallel building as the GF build process isn't parallel-safe
  enableParallelBuilding = false;

  configurePhase = ''
    runHook preConfigure

    export LOCALE_ARCHIVE=${glibcLocales}/lib/locale/locale-archive
    export LANG=C.UTF-8
    export LC_ALL=C.UTF-8

    # The RGL uses Setup.hs to build
    # We need to point it to the gf executable
    export GF=${haskellPackages.gf}/bin/gf

    # Make sure GF can find its own libraries
    export GF_LIB_PATH=${haskellPackages.gf}/share/gf

    echo "Using GF: $GF"
    echo "GF version: $($GF --version || echo 'unknown')"

    runHook postConfigure
  '';

  buildPhase = ''
    runHook preBuild

    # Build using the Haskell setup script
    # This compiles all the GF grammar files
    echo "Building GF-RGL with options: ${modeFlags} ${langFlag}"

    runghc Setup.hs build ${modeFlags} ${langFlag} --gf=${haskellPackages.gf}/bin/gf --verbose

    runHook postBuild
  '';

  installPhase = ''
    runHook preInstall

    # Install to the output directory
    mkdir -p $out/share/gf

    # Copy the compiled files
    echo "Installing to $out/share/gf"
    runghc Setup.hs copy ${modeFlags} --dest=$out/share/gf

    # Create a setup hook so other derivations can find this
    mkdir -p $out/nix-support
    cat > $out/nix-support/setup-hook << EOF
    export GF_LIB_PATH="\''${GF_LIB_PATH:+\''${GF_LIB_PATH}:}$out/share/gf"
    EOF

    runHook postInstall
  '';

  # The RGL is architecture-independent (it's just compiled grammar files)
  # but we keep it architecture-specific for now to be safe
  # preferLocalBuild = true;

  meta = with lib; {
    description = "Grammatical Framework's Resource Grammar Library (RGL)";
    longDescription = ''
      The GF Resource Grammar Library is the standard library for Grammatical
      Framework. It covers the morphology and basic syntax of over 30 languages.

      This package includes compiled grammar modules (.gfo files) that can be
      imported and used in GF applications.

      Supported languages include: English, Swedish, German, French, Spanish,
      Italian, Dutch, Finnish, Russian, Bulgarian, Catalan, Danish, Norwegian,
      Polish, Romanian, Afrikaans, Amharic, Arabic, Basque, Chinese, Estonian,
      Greek, Hebrew, Hindi, Japanese, Korean, Latvian, Maltese, Mongolian,
      Nepali, Persian, Punjabi, Sindhi, Somali, Thai, Turkish, Urdu, and more.
    '';
    homepage = "https://www.grammaticalframework.org/";
    license = with licenses; [
      lgpl3Plus
      bsd3
    ];
    maintainers = with maintainers; [ ];
    platforms = platforms.unix;
    # Note: This may take a while to build (30+ minutes for all languages)
    # Consider using binary caches or building with specific languages only
  };
}