✨ (modules/flake) improve library loading and implement system class module mappings

modules/flake/arguments.nix

@@ -1,50 +1,10 @@
 {
-  lib,
-  inputs,
   config,
   ...
 }:
-let
-  ## Recursive loading of libraries, similar to snowfall lib.
-  ## Logical flow: read files => merge all file outputs to single attr. set
-  ## The directory in question is flake-root => lib
-  ## The directory structure is:
-  ## lib/
-  ##   => libname
-  ##     => default.nix
-  ##   => libname2
-  ##     => default.nix
-  ##
-  ## The structure of multiple libs is simply for organization and the attrs. of all default.nix files should still be merged
-  ## into a single set.
-  loadLibs = directory:
-    builtins.foldl' (acc: name:
-      let
-        path = "${directory}/${name}";
-        isDir = (builtins.getAttr name (builtins.readDir directory)) == "directory";
-      in
-        if isDir then
-          lib.mergeAttrs acc (loadLibs path)
-        else if name == "default.nix" then
-          lib.mergeAttrs acc (import path { inherit lib; })
-        else
-          acc
-    ) {} (builtins.attrNames (builtins.readDir directory));
-in
 {
-  # Overwrite and add new arguments to all flake modules.
+  # Apply some useful module arguments.
   _module.args = {
     namespace = config.flake.namespace;
-
-    puzzlelib = loadLibs ../../lib;
-
-    # Initialize nixpkgs instance with custom overlays.
-    pkgs = import inputs.nixpkgs {
-      overlays = [
-        (final: prev: {
-          # Todo: actually append overlays from "/overlays/overlay-name/default.nix" files.
-        })
-      ];
-    };
   };
 }

modules/flake/default.nix

@@ -1,9 +1,14 @@
 {
   imports = [
-    # Automagically imports overlays from "/overlays/overlay-name" and applies them to pkgs.
-    # Also applies some other useful arguments, like namespace, to all flake modules.
+    # Applies some useful arguments, like namespace, to all flake modules.
     ./arguments.nix
 
+    # Automagically imports libs from "/lib/lib-name" and applies them to the `lib.${namespace}` or `puzzlevision.lib` module argument.
+    ./lib.nix
+
+    # Recursively imports overlays from "/overlays/overlay-name" and applies them to the `pkgs` or `puzzlevision.pkgs` module argument.
+    # ./overlays.nix
+
     # Automagically imports systems from "/systems/arch-classname/system-name".
     ./systems.nix
   ];

modules/flake/lib.nix

@@ -0,0 +1,54 @@
+{
+  lib,
+  puzzlelib,
+  ...
+}:
+let
+  # Utility function to read a directory and return its contents.
+  readDirectory = directory: builtins.readDir directory;
+
+  # Utility function to handle each filesystem entity (file or directory).
+  filesystemEntityToAttrSet = directory: importArgs: name: type:
+    if type == "directory" then
+      dirToAttrSet "${directory}/${name}" importArgs
+    else if name == "default.nix" then
+      import "${directory}/${name}" importArgs
+    else
+      {};
+
+  filesystemEntityToList = directory: name: type:
+    if type == "directory" then
+      dirToModuleList "${directory}/${name}"
+    else if name == "default.nix" then
+      [ "${directory}/${name}" ]
+    else
+      [];
+
+  dirToModuleList = directory:
+    let
+      readDir = readDirectory directory;
+    in
+      builtins.foldl' (acc: name:
+        acc ++ (filesystemEntityToList directory name (builtins.getAttr name readDir))
+      ) [] (builtins.attrNames readDir);
+
+  # Utility function to recursively load modules from a directory.
+  dirToAttrSet = directory: importArgs:
+    let
+      # Read provided directory only once at the very start and save the result.
+      readDir = readDirectory directory;
+    in
+      # Iterate over the attr names of a readDir operation.
+      builtins.foldl' (acc: name:
+        # Merge outputs of handling a filesystem entity (file or directory) into accumulator.
+        # Files return attribute sets with their resulting expressions, directories return the result of multiple file handling operations.
+        acc // (filesystemEntityToAttrSet directory importArgs name (builtins.getAttr name readDir))
+      ) {} (builtins.attrNames readDir);
+in
+{
+  # Add lib.${namespace} attribute to module arguments, for easy access.
+  # Additionally, pass on dirToAttrSet method on lib.${namespace} for reusability in other modules.
+  _module.args = {
+    puzzlelib = dirToAttrSet ../../lib { inherit lib puzzlelib; } // { inherit dirToAttrSet dirToModuleList filesystemEntityToList filesystemEntityToAttrSet; };
+  };
+}

modules/flake/systems.nix

@@ -1,6 +1,8 @@
 {
+  lib,
   inputs,
   namespace,
+  puzzlelib,
   ...
 }:
 {
@@ -12,19 +14,16 @@
 
     shared = {
       specialArgs = {
-        inherit namespace;
+        inherit namespace puzzlelib;
       };
     };
 
     perClass = class: {
       modules = [
-        # Import modules based on current classname.
-        ../${class}
-
-        (inputs.nixpkgs.lib.optionals (class == "nixos") [
+        (lib.optionals (class == "nixos") [
           inputs.home-manager.nixosModules.default
         ])
-      ];
+      ] ++ (puzzlelib.dirToModuleList ../${class}); # Import modules based on current classname.
     };
   };
 }