lib/path: add scanPaths

lib/path.nix

@@ -1,5 +1,6 @@
 # Portions of this file are sourced from
 # https://github.com/linyinfeng/dotfiles/tree/b618b0fd16fb9c79ab7199ed51c4c0f98a392cea/lib
+# https://github.com/spikespaz/bird-nix-lib/blob/3f44018dde966a00193081470f85a59458916986/lib/scaffold.nix
 {
   inputs,
   lib,
@@ -36,7 +37,35 @@ let
     lib.listToAttrs (flattenTree' "" tree);
 
   buildModuleList = dir: lib.attrValues (flattenTree (rakeLeaves dir));
+
+  scanPaths =
+    path: keep:
+    let
+      inherit (lib) types;
+      pred =
+        if keep == null then
+          (_: _: true)
+        else if types.singleLineStr.check keep then
+          (name: _: !(name == keep))
+        else if lib.isFunction keep then
+          keep
+        else if (types.listOf types.singleLineStr).check keep then
+          (name: _: !(builtins.elem name keep))
+        else
+          throw "importDir predicate should be a string, function, or list of strings";
+      isNix =
+        name: type:
+        (type == "regular" && lib.hasSuffix ".nix" name)
+        || (lib.pathIsRegularFile "${path}/${name}/default.nix");
+      pred' = name: type: (isNix name type) && (pred name type);
+    in
+    map (name: path + "/${name}") (builtins.attrNames (lib.filterAttrs pred' (builtins.readDir path)));
 in
 {
-  inherit rakeLeaves flattenTree buildModuleList;
+  inherit
+    rakeLeaves
+    flattenTree
+    buildModuleList
+    scanPaths
+    ;
 }