i3blocks: add optional dependencies for scripts

pkgs/applications/window-managers/i3/blocks-gaps.nix

@@ -1,5 +1,16 @@
-{ fetchFromGitHub, stdenv }:
+{ fetchFromGitHub, stdenv, perl, makeWrapper
+, iproute, acpi, sysstat, alsaUtils
+, scripts ? [ "bandwidth" "battery" "cpu_usage" "disk" "iface"
+              "load_average" "memory" "volume" "wifi" ]
+}:
 
+with stdenv.lib;
+
+let
+  perlscripts = [ "battery" "cpu_usage" "openvpn" "temperature" ];
+  contains_any = l1: l2: 0 < length( intersectLists l1 l2 );
+
+in
 stdenv.mkDerivation rec {
   name = "i3blocks-gaps-${version}";
   version = "1.4";
@@ -14,6 +25,22 @@ stdenv.mkDerivation rec {
   makeFlags = "all";
   installFlags = "PREFIX=\${out} VERSION=${version}";
 
+  buildInputs = optional (contains_any scripts perlscripts) perl;
+  nativeBuildInputs = [ makeWrapper ];
+
+  postFixup = ''
+    wrapProgram $out/libexec/i3blocks/bandwidth \
+      --prefix PATH : ${makeBinPath (optional (elem "bandwidth" scripts) iproute)}
+    wrapProgram $out/libexec/i3blocks/battery \
+      --prefix PATH : ${makeBinPath (optional (elem "battery" scripts) acpi)}
+    wrapProgram $out/libexec/i3blocks/cpu_usage \
+      --prefix PATH : ${makeBinPath (optional (elem "cpu_usage" scripts) sysstat)}
+    wrapProgram $out/libexec/i3blocks/iface \
+      --prefix PATH : ${makeBinPath (optional (elem "iface" scripts) iproute)}
+    wrapProgram $out/libexec/i3blocks/volume \
+      --prefix PATH : ${makeBinPath (optional (elem "volume" scripts) alsaUtils)}
+  '';
+
   meta = with stdenv.lib; {
     description = "A flexible scheduler for your i3bar blocks -- this is a fork to use with i3-gaps";
     homepage = https://github.com/Airblader/i3blocks-gaps;