# 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))