utils: create utility functions to ease repetition

`reqImport` in particular, is useful for easily importing an entire
directory of nix files into an attribute set.

configurations/default.nix

@@ -1,22 +1,12 @@
-{ nix, nixpkgs, flake, ... }:
+{ nix, nixpkgs, flake, utils, ... }:
 let
-  inherit (builtins)
+  inherit (utils)
-    isAttrs
+    reqImport
-    readDir
+    vimport
-    ;
-
-  inherit (nixpkgs.lib)
-    filterAttrs
-    hasSuffix
-    mapAttrs'
-    nameValuePair
-    removeSuffix
     ;
 
 
-  configs = let
+  config = self:
-    configs' = let
-      config = this:
     nixpkgs.lib.nixosSystem rec {
       system = "x86_64-linux";
 
@@ -24,14 +14,16 @@ let
         core = ../profiles/core.nix;
 
         global = {
+          _module.args.utils = utils;
+
           system.configurationRevision = flake.rev;
 
-              networking.hostName = "${this}";
+          networking.hostName = self;
 
           nix.package = nix.defaultPackage."${system}";
         };
 
-            local = ./. + "/${this}.nix";
+        local = vimport ./. "${self}.nix";
 
       in
         [
@@ -41,32 +33,5 @@ let
         ];
 
     };
-
-      dot = readDir ./.;
-
 in
-      mapAttrs'
+  reqImport { dir = ./.; _import = config; }
-        (
-          name: value:
-            if
-              name != "default.nix"
-              && hasSuffix ".nix" name
-              && value == "regular"
-
-            then let
-              name' = removeSuffix ".nix" name;
-            in
-              nameValuePair (name') (config name')
-
-            else
-              nameValuePair ("") (null)
-        )
-        dot;
-
-    removeInvalid =
-      filterAttrs (_: value: isAttrs value);
-  in
-    removeInvalid configs';
-
-in
-configs

flake.nix

@@ -9,6 +9,7 @@
         configs = import ./configurations {
           inherit nix nixpkgs;
           flake = self;
+          utils = import ./lib/utils.nix { lib = nixpkgs.lib; };
         };
 
       in

lib/utils.nix

@@ -1,2 +1,51 @@
-{ ... }:
+{ lib, ... }:
-{}
+let
+  inherit (builtins)
+    attrNames
+    isAttrs
+    readDir
+    ;
+
+
+  inherit (lib)
+    filterAttrs
+    hasSuffix
+    mapAttrs'
+    nameValuePair
+    removeSuffix
+    ;
+
+in
+rec {
+  # mapFilterAttrs ::
+  #   (name -> value -> bool )
+  #   (name -> value -> { name = any; value = any; })
+  #   attrs
+  mapFilterAttrs = seive: f: attrs:
+    filterAttrs seive (mapAttrs' f attrs);
+
+  vimport = path: name: import (path + "/${name}");
+
+  reqImport = {
+    dir,
+    _import ? base: vimport dir (base + ".nix")
+  }:
+    mapFilterAttrs
+      (_: v: v != null)
+      (
+        n: v:
+          if
+            n != "default.nix"
+            && hasSuffix ".nix" n
+            && v == "regular"
+
+          then let
+            name = removeSuffix ".nix" n;
+          in
+            nameValuePair (name) (_import name)
+
+          else
+            nameValuePair ("") (null)
+      )
+      (readDir dir);
+}