fix Nix code and flakes

default.nix

@@ -3,33 +3,4 @@ let
   version = "dev";
   pkgs = import <nixpkgs> {};
 
-in with pkgs; stdenv.mkDerivation {
-  pname = "qdng";
-  inherit version;
-
-  src = builtins.filterSource (path: type: path != ".git" && path != "result" && path != "build") ./.;
-
-  configureFlags = [
-    "--enable-openmp"
-    "--with-blas=-lblas"
-    "--with-lapack=-llapack"
-    "--disable-gccopt"
-  ];
-
-  enableParallelBuilding = true;
-
-  preConfigure = ''
-    ./genbs
-  '';
-
-  buildInputs = [ fftw protobuf blas lapack
-                  bzip2 zlib libxml2 flex bison ];
-  nativeBuildInputs = [ automake autoconf libtool gfortran ];
-
-  meta = with lib; {
-    description = "Quantum dynamics program package";
-    platforms = platforms.linux;
-    maintainer = [ maintainers.markuskowa ];
-    license = licenses.unfree;
-  };
-}
+in pkgs.callPackage ./package.nix { protobuf = pkgs.protobuf3_21; }

flake.nix

@@ -0,0 +1,18 @@
+{
+  description = "Quantum dynamics program package";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-23.11";
+  };
+
+  outputs = { self, nixpkgs }: {
+
+    packages.x86_64-linux = let
+      pkgs = nixpkgs.legacyPackages.x86_64-linux;
+      inherit (pkgs) lib callPackage;
+    in {
+      qdng = callPackage ./package.nix { protobuf = pkgs.protobuf3_21; };
+      default = self.packages.x86_64-linux.qdng;
+    };
+  };
+}

package.nix

@@ -0,0 +1,36 @@
+{ lib, stdenv, fetchurl, requireFile, gfortran, fftw, protobuf
+, blas, lapack
+, automake, autoconf, libtool, zlib, bzip2, libxml2, flex, bison
+} :
+
+stdenv.mkDerivation rec {
+  pname = "qdng";
+  version = "1.0.0";
+
+  src = builtins.filterSource (path: type: path != ".git" && path != "result" && path != "build") ./.;
+
+  configureFlags = [
+    "--enable-openmp"
+    "--with-blas=-lblas"
+    "--with-lapack=-llapack"
+    "--disable-gccopt"
+  ];
+
+  enableParallelBuilding = true;
+
+  preConfigure = ''
+    ./genbs
+  '';
+
+  buildInputs = [ fftw protobuf blas lapack
+                  bzip2 zlib libxml2 flex bison ];
+  nativeBuildInputs = [ automake autoconf libtool gfortran ];
+
+  meta = with lib; {
+    description = "Quantum dynamics program package";
+    platforms = platforms.linux;
+    maintainer = [ maintainers.markuskowa ];
+    license = licenses.gpl3Only;
+  };
+}
+