big refactoring

lib/mkSystem.nix

@@ -2,26 +2,28 @@
   inputs,
   ...
 }:
+# Builds a NixOS system from a host record.
+#
+# `xlib` is the pure host value (lib/xlib.nix `mkXlib`) built in
+# configurations/default.nix. It is handed to every module as the `xlib`
+# argument, so modules read plain `xlib.*` data instead of `config.xlib.*`
+# and the host record stays the single source of truth.
 {
-  deviceType,
-  hostname ? null,
+  xlib,
   modules ? [ ],
   system ? "x86_64-linux",
+  ...
 }:
 let
   lib = inputs.nixpkgs.lib;
 in
 lib.nixosSystem {
-  inherit system;
-  modules = modules ++ [
-    {
-      xlib.device = {
-        type = deviceType;
-      }
-      // lib.optionalAttrs (hostname != null) { inherit hostname; };
-    }
-  ];
+  inherit
+    system
+    modules
+    ;
   specialArgs = {
-    inherit deviceType inputs;
+    inherit inputs;
+    inherit xlib;
   };
 }

lib/xlib.nix

@@ -2,9 +2,49 @@
   lib,
   ...
 }:
-# Shared pure helper functions for module definitions.
-# Injected into every module via `xlib.helpers` (see options.nix).
+# Pure host library: no module system involved.
+#
+# `mkXlib` derives everything a host needs to know about itself (identity,
+# well-known paths, capability flags, shared helpers) from a single record.
+# It is built 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.
 let
+  # Every supported device type and its capabilities. Single source of truth:
+  # replaces the old `lib.types.enum` in modules/options.nix and the
+  # hand-written type lists in modules/default.nix and home/home.nix.
+  devices = {
+    minimal = {
+      desktop = false;
+      headless = false;
+    };
+    primary = {
+      desktop = true;
+      headless = false;
+    };
+    secondary = {
+      desktop = true;
+      headless = false;
+    };
+    server = {
+      desktop = false;
+      headless = true;
+    };
+    vds = {
+      desktop = false;
+      headless = true;
+    };
+    wsl = {
+      desktop = false;
+      headless = true;
+    };
+    termux = {
+      desktop = false;
+      headless = true;
+    };
+  };
+
   # tmpfiles rule: "type dir mode user group -"
   mkTmpfile =
     type: dir: mode: user: group:
@@ -138,16 +178,85 @@ let
       name = targetPath;
       value.source = config.lib.file.mkOutOfStoreSymlink "${sourcePath}";
     }) paths;
+
+  helpers = {
+    inherit
+      mkTmpfile
+      mkTmpDirs
+      mkBindMount
+      mkSystemdBind
+      mkServiceStorage
+      mkNtfsMount
+      mkExfatMount
+      mkSymlinks
+      ;
+  };
+
+  # Well-known paths. Everything derives from `username`, which is why the
+  # whole set can be computed outside the module system.
+  mkDirs =
+    username:
+    let
+      user-home = "/home/${username}";
+      wsl-home = "/mnt/c/Users/${username}";
+      server-home = "${user-home}/External";
+      services-mnt-folder = "/mnt/services";
+    in
+    {
+      inherit
+        user-home
+        wsl-home
+        server-home
+        services-mnt-folder
+        ;
+
+      user-storage = "${user-home}/Storage";
+      wsl-storage = "${wsl-home}/Storage";
+      server-credentials = "${server-home}/Credentials/server";
+      storage = "${server-home}/Storage";
+      calibre-library = "${server-home}/Books-Library";
+      services-folder = "${server-home}/Services";
+      services-nodes-folder = "${services-mnt-folder}/nodes";
+      postgresql-folder = "${services-mnt-folder}/postgresql";
+      music-library = "${user-home}/Music";
+
+      archive-drive = "/mnt/archive";
+      lamet-drive = "/mnt/lamet";
+      mobile-drive = "/mnt/mobile";
+      therima-drive = "/mnt/therima";
+      vetymae-drive = "/mnt/vetymae";
+      soptur-drive = "/mnt/soptur";
+    };
+
+  mkXlib =
+    {
+      hostname,
+      type,
+      username ? "oqyude",
+    }:
+    let
+      # Unknown device type fails here, at flake level, with the valid list.
+      capabilities = devices.${type} or (throw "xlib: unknown device type '${type}', expected one of ${lib.concatStringsSep ", " (builtins.attrNames devices)}");
+    in
+    {
+      device = {
+        inherit
+          hostname
+          type
+          username
+          ;
+      };
+      isDesktop = capabilities.desktop;
+      isHeadless = capabilities.headless;
+      dirs = mkDirs username;
+      inherit helpers;
+    };
 in
 {
   inherit
-    mkTmpfile
-    mkTmpDirs
-    mkBindMount
-    mkSystemdBind
-    mkServiceStorage
-    mkNtfsMount
-    mkExfatMount
-    mkSymlinks
+    devices
+    helpers
+    mkDirs
+    mkXlib
     ;
 }