restructuring

lib/xlib/default.nix

@@ -0,0 +1,66 @@
+# Pure host library: no module system involved.
+#
+# Aggregates the four concerns a host record is built from:
+#   device.nix   identity + capability flags from the device type
+#   dirs.nix     well-known paths, derived from username
+#   helpers.nix  pure helper functions shared by modules
+#
+# `mkXlib` is called in flake-level code (configurations/default.nix) and
+# handed to every module as the `xlib` argument via lib/mkSystem.nix, so
+# modules read plain `xlib.*` values instead of `config.xlib.*` and nothing in
+# xlib can be overridden per host — the host record is the only place to
+# change it.
+{
+  lib,
+  ...
+}:
+let
+  inherit (import ./device.nix { inherit lib; })
+    devices
+    mkDevice
+    ;
+
+  # dirs.nix is itself a function of `username`, not an attrset.
+  mkDirs = import ./dirs.nix;
+
+  helpers = (import ./helpers.nix { inherit lib; });
+in
+{
+  inherit
+    devices
+    helpers
+    mkDevice
+    mkDirs
+    ;
+
+  # Full host record: identity + capability flags + well-known paths +
+  # shared helpers.
+  mkXlib =
+    {
+      hostname,
+      type,
+      username ? "oqyude",
+    }:
+    let
+      device = mkDevice {
+        inherit
+          hostname
+          type
+          username
+          ;
+      };
+    in
+    {
+      device = {
+        inherit
+          hostname
+          type
+          username
+          ;
+      };
+      isDesktop = device.isDesktop;
+      isHeadless = device.isHeadless;
+      dirs = mkDirs username;
+      inherit helpers;
+    };
+}