feat: auto import modules and simplify configs

lib/mkHost.nix

@@ -7,19 +7,23 @@
 name:
 {
   system,
-  users ? [ ],
+  user ? null,
 }:
 
 let
   hostConfig = ../hosts/${name}/configuration.nix;
   hostHWConfig = ../hosts/${name}/hardware-configuration.nix;
   hasHWConfig = builtins.pathExists hostHWConfig;
+  hasUser = user != null;
 
-  userNixosConfigs = map (user: ../users/${user}/nixos.nix) (
-    builtins.filter (user: builtins.pathExists ../users/${user}/nixos.nix) users
-  );
+  userKeys = if hasUser then import ../users/${user}/keys.nix else { };
 
-  userHMConfigs = nixpkgs.lib.genAttrs users (user: import ../users/${user}/home-manager.nix);
+  # auto-import all nixos modules and profiles
+  nixosModuleList = builtins.attrValues inputs.self.nixosModules;
+  nixosProfileList = builtins.attrValues inputs.self.nixosProfiles;
+
+  # auto-import all home-manager modules
+  hmModuleList = builtins.attrValues inputs.self.homeManagerModules;
 
 in
 nixpkgs.lib.nixosSystem {
@@ -33,16 +37,23 @@ nixpkgs.lib.nixosSystem {
     hostConfig
   ]
   ++ nixpkgs.lib.optional hasHWConfig hostHWConfig
-  ++ userNixosConfigs
+  ++ nixosModuleList
+  ++ nixosProfileList
+  ++ nixpkgs.lib.optional (
+    hasUser && builtins.pathExists ../users/${user}/nixos.nix
+  ) ../users/${user}/nixos.nix
   ++ [
     inputs.home-manager.nixosModules.home-manager
     {
       home-manager.useGlobalPkgs = true;
       home-manager.useUserPackages = true;
       home-manager.backupFileExtension = "backup";
-      home-manager.users = userHMConfigs;
+      home-manager.users = nixpkgs.lib.mkIf hasUser {
+        ${user} = import ../users/${user}/home-manager.nix;
+      };
+      home-manager.sharedModules = hmModuleList;
       home-manager.extraSpecialArgs = { inherit inputs; };
     }
   ];
-  specialArgs = { inherit inputs; };
+  specialArgs = { inherit inputs userKeys; };
 }