refactor(dotfiles): split registry helpers

src/dotfiles/registry/definition-module.nix

@@ -0,0 +1,66 @@
+{ lib }:
+let
+  checkType = lib.types.submodule {
+    options = {
+      assertion = lib.mkOption {
+        type = lib.types.functionTo lib.types.bool;
+        description = ''
+          Predicate run against this registry's flattened collected entries.
+        '';
+      };
+
+      message = lib.mkOption {
+        type = lib.types.str;
+        description = ''
+          Error message shown when this registry validation check fails.
+        '';
+      };
+    };
+  };
+
+  predicates = {
+    uniqueValue =
+      value: entries: builtins.length (lib.unique (map value entries)) == builtins.length entries;
+  };
+
+  registryLib = lib // {
+    registry = (lib.registry or { }) // {
+      inherit predicates;
+    };
+  };
+
+  registryDefinitionModule = {
+    options = {
+      type = lib.mkOption {
+        type = lib.types.raw;
+        description = ''
+          NixOS option type for one registry entry.
+        '';
+      };
+
+      replicate = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = ''
+          Whether collected entries are merged and published under every host key.
+        '';
+      };
+
+      checks = lib.mkOption {
+        type = lib.types.listOf checkType;
+        default = [ ];
+        description = ''
+          Validation checks for this registry's flattened collected entries.
+        '';
+      };
+    };
+  };
+in
+{
+  inherit
+    checkType
+    predicates
+    registryDefinitionModule
+    registryLib
+    ;
+}