chore: initial commit

lib/overlay/default.nix

@@ -0,0 +1,43 @@
+{ core-inputs
+, user-inputs
+, snowfall-lib
+}:
+
+let
+  inherit (core-inputs.nixpkgs.lib) assertMsg;
+
+  user-overlays-root = snowfall-lib.fs.get-file "overlays";
+in
+{
+  overlay = {
+    # Create a flake-utils-plus overlays builder.
+    # Type: Attrs -> Attrs -> [(a -> b -> c)]
+    # Usage: create-overlays { src = ./my-overlays; overlay-package-namespace = "my-packages"; }
+    #   result: (channels: [ ... ])
+    create-overlays =
+      { src ? user-overlays-root
+      , overlay-package-namespace ? null
+      , extra-overlays ? [ ]
+      }: channels:
+      let
+        user-overlays = snowfall-lib.fs.get-default-nix-files-recursive src;
+        create-overlay = overlay: import overlay (user-inputs // { inherit channels; });
+        user-packages-overlay = final: prev:
+          let
+            user-packages = snowfall-lib.package.create-packages {
+              channels = channels;
+            };
+            user-packages-without-default = builtins.removeAttrs
+              (user-packages) [ "default" ];
+          in
+          if overlay-package-namespace == null then
+            user-packages-without-default
+          else
+            {
+              ${overlay-package-namespace} = user-packages-without-default;
+            };
+        overlays = [ user-packages-overlay ] ++ extra-overlays ++ (builtins.map create-overlay user-overlays);
+      in
+      overlays;
+  };
+}