rename /cerulean -> /nix

nix/nixos/nixpkgs.nix

@@ -0,0 +1,95 @@
+# Copyright 2025-2026 _cry64 (Emile Clark-Boman)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+{
+  base,
+  lib,
+  system,
+  config,
+  contextName,
+  ...
+}: let
+  inherit
+    (builtins)
+    mapAttrs
+    ;
+
+  cfg = config.nixpkgs.channels;
+in {
+  options.nixpkgs.channels = lib.mkOption {
+    type = lib.types.attrs;
+    default = {};
+    description = "Declare package repositories";
+    example = {
+      "npkgs" = {
+        source = "inputs.nixpkgs";
+        system = "x86-64-linux";
+        config = {
+          allowUnfree = true;
+          allowBroken = false;
+        };
+      };
+      "upkgs" = {
+        source = "inputs.nixpkgs-unstable";
+        system = "x86-64-linux";
+        config = {
+          allowUnfree = false;
+          allowBroken = true;
+        };
+      };
+    };
+  };
+
+  config = let
+    repos =
+      cfg
+      |> (xs: removeAttrs xs ["base"])
+      |> mapAttrs (
+        name: args:
+          lib.mkForce (
+            assert args ? source
+            || abort ''
+              `nixpkgs.channels.${name}` missing required attribute "source"
+            '';
+              import args.source ({inherit system;} // (removeAttrs args ["source"]))
+          )
+      );
+
+    basePkgs = cfg.base or {};
+  in {
+    # NOTE: _module.args is a special option that allows us to
+    # NOTE: set extend specialArgs from inside the modules.
+    # WARNING: pkgs is a reserved specialArg
+    _module.args = removeAttrs repos ["pkgs" "base"];
+
+    nixpkgs = let
+      nixpkgsConfig = {
+        config = lib.mkForce (basePkgs.config or {});
+        overlays = lib.mkForce (basePkgs.overlays or []);
+      };
+
+      nixpkgsHostsConfig =
+        nixpkgsConfig
+        // {
+          flake.source = lib.mkForce base;
+        };
+
+      nixpkgsHomesConfig = lib.mkIf (!config.home-manager.useGlobalPkgs) nixpkgsConfig;
+    in
+      if contextName == "hosts"
+      then nixpkgsHostsConfig
+      else if contextName == "homes"
+      then nixpkgsHomesConfig
+      else {};
+  };
+}