feat(home): add cosmic module

home/modules/cosmic/default.nix

@@ -0,0 +1,53 @@
+{ config, lib, ... }:
+
+# Based on:
+# https://github.com/tristanbeedell/home-manager/tree/efa4d272f6c2b14d4a3b67b0b1e4b38ae46e5588/modules/programs/cosmic
+
+let
+  cfg = config.programs.cosmic;
+
+  ron = import ./ron.nix { inherit lib; };
+in
+{
+  imports = [ ./settings.nix ];
+
+  options.programs.cosmic = {
+    enable = lib.mkEnableOption "COSMIC Desktop";
+    settings = lib.mkOption {
+      default = { };
+      type = lib.types.submodule {
+        freeformType = lib.types.submodule {
+          freeformType = lib.types.attrsOf lib.types.anything;
+        };
+      };
+      description = ''
+        An attrset of explicit settings for COSMIC apps, using their full config path.
+      '';
+      example = lib.literalExpression ''
+        {
+          "com.system76.CosmicPanel.Dock".v1 = {
+            opacity = 0.8;
+          };
+        };
+      '';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    xdg.configFile = lib.concatMapAttrs (
+      component:
+      lib.concatMapAttrs (
+        version:
+        lib.concatMapAttrs (
+          option: value:
+          lib.optionalAttrs (value != null) {
+            "cosmic/${component}/${version}/${option}" = {
+              enable = true;
+              text = ron.serialise value;
+            };
+          }
+        )
+      )
+    ) cfg.settings;
+  };
+}