# generic builder for Emacs packages

{
  lib,
  stdenv,
  emacs,
  texinfo,
  writeText,
  gcc,
  ...
}:

let
  inherit (lib) optionalAttrs getLib;
  handledArgs = [
    "buildInputs"
    "packageRequires"
    "meta"
  ];

  setupHook = writeText "setup-hook.sh" ''
    source ${./emacs-funcs.sh}

    if [[ ! -v emacsHookDone ]]; then
      emacsHookDone=1

      # If this is for a wrapper derivation, emacs and the dependencies are all
      # run-time dependencies. If this is for precompiling packages into bytecode,
      # emacs is a compile-time dependency of the package.
      addEnvHooks "$hostOffset" addEmacsVars
      addEnvHooks "$targetOffset" addEmacsVars
    fi
  '';

in

{
  pname,
  version,
  buildInputs ? [ ],
  packageRequires ? [ ],
  meta ? { },
  ...
}@args:

stdenv.mkDerivation (
  finalAttrs:
  (
    {
      name = "emacs-${pname}-${finalAttrs.version}";

      unpackCmd = ''
        case "$curSrc" in
          *.el)
            # keep original source filename without the hash
            local filename=$(basename "$curSrc")
            filename="''${filename:33}"
            cp $curSrc $filename
            chmod +w $filename
            sourceRoot="."
            ;;
          *)
            _defaultUnpack "$curSrc"
            ;;
        esac
      '';

      buildInputs = [
        emacs
        texinfo
      ] ++ packageRequires ++ buildInputs;
      propagatedBuildInputs = packageRequires;
      propagatedUserEnvPkgs = packageRequires;

      inherit setupHook;

      doCheck = false;

      meta =
        {
          broken = false;
          platforms = emacs.meta.platforms;
        }
        // optionalAttrs ((args.src.meta.homepage or "") != "") { homepage = args.src.meta.homepage; }
        // meta;
    }

    // optionalAttrs (emacs.withNativeCompilation or false) {

      LIBRARY_PATH = "${getLib stdenv.cc.libc}/lib";

      nativeBuildInputs = [ gcc ];

      addEmacsNativeLoadPath = true;

      postInstall = ''
        # Besides adding the output directory to the native load path, make sure
        # the current package's elisp files are in the load path, otherwise
        # (require 'file-b) from file-a.el in the same package will fail.
        mkdir -p $out/share/emacs/native-lisp
        source ${./emacs-funcs.sh}
        addEmacsVars "$out"

        find $out/share/emacs -type f -name '*.el' -print0 \
          | xargs -0 -I {} -n 1 -P $NIX_BUILD_CORES sh -c \
              "emacs --batch --eval '(setq large-file-warning-threshold nil)' -f batch-native-compile {} || true"
      '';
    }

    // removeAttrs args handledArgs
  )
)