nix: add modular nixos and home-manager configuration loading

spec/channel.nix

@@ -0,0 +1,15 @@
+{ inputs, ... }: with inputs; with nixpkgs.lib; let
+  mapInputs = fn: map fn (lists.remove "self" (attrNames inputs));
+  channelPath = "/etc/nix/channels";
+in {
+  nix = {
+    nixPath = mapInputs (i: "${i}=${channelPath}/${i}");
+    registry = listToAttrs
+      (mapInputs (name: {
+        inherit name;
+        value = {flake = inputs.${name};};
+      }));
+  };
+
+  systemd.tmpfiles.rules = mapInputs (i: "L+ ${channelPath}/${i}     - - - - ${inputs.${i}.outPath}");
+}

spec/constant.nix

@@ -0,0 +1,7 @@
+{
+  i18n.defaultLocale = "en_GB.UTF-8";
+  time.timeZone = "Asia/Hong_Kong";
+  environment.etc.nixos.source = "/nix/persist/config";
+  nix.settings.experimental-features = [ "nix-command" "flakes" ];
+  system.stateVersion = "23.11";
+}

spec/default.nix

@@ -0,0 +1,29 @@
+{ inputs, ... }: with inputs; with nixpkgs.lib; {
+  flake.nixosConfigurations = (lists.foldr (name: spec: spec // {
+    ${name} = nixpkgs.lib.nixosSystem {
+      system = "x86_64-linux";
+      specialArgs = inputs // { inherit inputs; };
+      modules = [
+        ../faucet
+        ../home/profile.nix
+        ../home/user.nix
+        ./constant.nix
+        ./channel.nix
+        impermanence.nixosModules.impermanence
+        home-manager.nixosModules.home-manager
+        {
+          home-manager.useGlobalPkgs = true;
+          home-manager.useUserPackages = true;
+        }
+        lanzaboote.nixosModules.lanzaboote
+
+        ./${name}
+        { networking.hostName = name; }
+      ];
+    };
+  }) { }) (pipe ./. [
+    builtins.readDir
+    (filterAttrs (n: ty: ty == "directory" && builtins.pathExists ./${n}/default.nix))
+    (mapAttrsToList (n: _: n))
+  ]);
+}