feat(nix): reorganize nix flake for modularity and flexibility

assets/pkg/nix/lidm.nix

@@ -0,0 +1,26 @@
+{ config, pkgs, ...}: pkgs.stdenv.mkDerivation rec {
+    pname = "lidm";
+    version = config.version;
+    src = config.src;
+
+    nativeBuildInputs = with pkgs; [
+        gcc
+        gnumake
+        linux-pam
+    ];
+
+    makeFlags = [
+        "DESTDIR=$(out)"
+        "PREFIX="
+    ];
+
+    installPhase = ''
+        make install DESTDIR=$out PREFIX=
+        mkdir -p $out/etc/systemd/system/
+        make install-service-systemd DESTDIR=$out PREFIX=
+    '';
+
+    fixupPhase = ''
+        rm -rf $out/etc
+    '';
+}

flake.nix

@@ -18,29 +18,10 @@
           builtins.match "VERSION[[:blank:]]*=[[:space:]]*([^\n]*)\n.*" (builtins.readFile ./Makefile)
         ) 0;
 
-        lidm = (
-          pkgs.stdenv.mkDerivation {
-            pname = name;
-            version = version;
-
-            src = ./.;
-
-            nativeBuildInputs = with pkgs; [
-              gcc
-              gnumake
-              linux-pam
-            ];
-
-            makeFlags = [
-              "DESTDIR=$(out)"
-              "PREFIX="
-            ];
-
-            fixupPhase = ''
-              rm -rf $out/etc
-            '';
-          }
-        );
+        lidm = pkgs.callPackage assets/pkg/nix/lidm.nix {
+          inherit pkgs;
+          config = { inherit version; src = ./.; };
+        };
       in
       rec {
         defaultApp = flake-utils.lib.mkApp { drv = defaultPackage; };