define yukari's monitors

modules/home-manager/default.nix

@@ -1,6 +1,3 @@
-# Add your reusable home-manager modules to this directory, on their own file (https://nixos.wiki/wiki/Module).
-# These should be stuff you would like to share with others, not your personal configurations.
 {
-  # List your module files here
-  # my-module = import ./my-module.nix;
+  monitors = import ./monitors.nix;
 }

modules/home-manager/monitors.nix

@@ -0,0 +1,59 @@
+{
+  lib,
+  config,
+  ...
+}: let
+  inherit (lib) mkOption types;
+in {
+  options.monitors = mkOption {
+    type = types.listOf (
+      types.submodule {
+        options = {
+          name = mkOption {
+            type = types.str;
+            example = "DP-1";
+          };
+          primary = mkOption {
+            type = types.bool;
+            default = false;
+          };
+          width = mkOption {
+            type = types.int;
+            example = 1920;
+          };
+          height = mkOption {
+            type = types.int;
+            example = 1080;
+          };
+          refreshRate = mkOption {
+            type = types.int;
+            default = 60;
+          };
+          position = mkOption {
+            type = types.str;
+            default = "auto";
+          };
+          enabled = mkOption {
+            type = types.bool;
+            default = true;
+          };
+          workspace = mkOption {
+            type = types.nullOr types.str;
+            default = null;
+          };
+        };
+      }
+    );
+    default = [];
+  };
+  config = {
+    assertions = [
+      {
+        assertion =
+          ((lib.length config.monitors) != 0)
+          -> ((lib.length (lib.filter (m: m.primary) config.monitors)) == 1);
+        message = "Exactly one monitor must be set to primary.";
+      }
+    ];
+  };
+}