config: update and refactor NixOS baseline config

configs/flake-parts/nixos.nix

@@ -7,75 +7,6 @@
 , ...
 }:
 
-let
-  # The shared configuration for the entire list of hosts for this cluster.
-  # Take note to only set as minimal configuration as possible since we're
-  # also using this with the stable version of nixpkgs.
-  defaultNixOSConfig = { options, config, lib, pkgs, ... }: {
-    # Initialize some of the XDG base directories ourselves since it is
-    # used by NIX_PROFILES to properly link some of them.
-    environment.sessionVariables = {
-      XDG_CACHE_HOME = "$HOME/.cache";
-      XDG_CONFIG_HOME = "$HOME/.config";
-      XDG_DATA_HOME = "$HOME/.local/share";
-      XDG_STATE_HOME = "$HOME/.local/state";
-    };
-
-    _module.args = defaultExtraArgs;
-
-    # Find Nix files with these! Even if nix-index is already enabled, it
-    # is better to make it explicit.
-    programs.command-not-found.enable = false;
-    programs.nix-index.enable = true;
-
-    # BOOOOOOOOOOOOO! Somebody give me a tomato!
-    services.xserver.excludePackages = with pkgs; [ xterm ];
-
-    # Append with the default time servers. It is becoming more unresponsive as
-    # of 2023-10-28.
-    networking.timeServers = [
-      "europe.pool.ntp.org"
-      "asia.pool.ntp.org"
-      "time.cloudflare.com"
-    ] ++ options.networking.timeServers.default;
-
-    # Disable channel state files. This shouldn't break any existing
-    # programs as long as we manage them NIX_PATH ourselves.
-    nix.channel.enable = lib.mkDefault false;
-
-    # Set several paths for the traditional channels.
-    nix.nixPath = lib.mkIf config.nix.channel.enable
-      (lib.mapAttrsToList
-        (name: source:
-          let
-            name' = if (name == "self") then "config" else name;
-          in
-          "${name'}=${source}")
-        inputs
-      ++ [
-        "/nix/var/nix/profiles/per-user/root/channels"
-      ]);
-
-    # Please clean your temporary crap.
-    boot.tmp.cleanOnBoot = lib.mkDefault true;
-
-    # We live in a Unicode world and dominantly English in technical fields so we'll
-    # have to go with it.
-    i18n.defaultLocale = lib.mkDefault "en_US.UTF-8";
-
-    # Enabling some things for sops.
-    programs.gnupg.agent = lib.mkDefault {
-      enable = true;
-      enableSSHSupport = true;
-    };
-    services.openssh.enable = lib.mkDefault true;
-
-    # It's following the 'nixpkgs' flake input which should be in unstable
-    # branches. Not to mention, most of the system configurations should
-    # have this attribute set explicitly by default.
-    system.stateVersion = lib.mkDefault "23.11";
-  };
-in
 {
   setups.nixos = {
     configs = {
@@ -165,7 +96,75 @@ in
         inputs.disko.nixosModules.disko
 
         defaultNixConf
-        defaultNixOSConfig
+
+        # The default shared configuration for the entire list of hosts for
+        # this cluster. Take note to only set as minimal configuration as
+        # possible since we're also using this with the stable version of
+        # nixpkgs.
+        ({ options, config, lib, pkgs, ... }: {
+          # Initialize some of the XDG base directories ourselves since it is
+          # used by NIX_PROFILES to properly link some of them.
+          environment.sessionVariables = {
+            XDG_CACHE_HOME = "$HOME/.cache";
+            XDG_CONFIG_HOME = "$HOME/.config";
+            XDG_DATA_HOME = "$HOME/.local/share";
+            XDG_STATE_HOME = "$HOME/.local/state";
+          };
+
+          _module.args = defaultExtraArgs;
+
+          # Find Nix files with these! Even if nix-index is already enabled, it
+          # is better to make it explicit.
+          programs.command-not-found.enable = false;
+          programs.nix-index.enable = true;
+
+          # BOOOOOOOOOOOOO! Somebody give me a tomato!
+          services.xserver.excludePackages = with pkgs; [ xterm ];
+
+          # Append with the default time servers. It is becoming more unresponsive as
+          # of 2023-10-28.
+          networking.timeServers = [
+            "europe.pool.ntp.org"
+            "asia.pool.ntp.org"
+            "time.cloudflare.com"
+          ] ++ options.networking.timeServers.default;
+
+          # Disable channel state files. This shouldn't break any existing
+          # programs as long as we manage them NIX_PATH ourselves.
+          nix.channel.enable = lib.mkDefault false;
+
+          # Set several paths for the traditional channels.
+          nix.nixPath = lib.mkIf config.nix.channel.enable
+            (lib.mapAttrsToList
+              (name: source:
+                let
+                  name' = if (name == "self") then "config" else name;
+                in
+                "${name'}=${source}")
+              inputs
+            ++ [
+              "/nix/var/nix/profiles/per-user/root/channels"
+            ]);
+
+          # Please clean your temporary crap.
+          boot.tmp.cleanOnBoot = lib.mkDefault true;
+
+          # We live in a Unicode world and dominantly English in technical fields so we'll
+          # have to go with it.
+          i18n.defaultLocale = lib.mkDefault "en_US.UTF-8";
+
+          # Enabling some things for sops.
+          programs.gnupg.agent = lib.mkDefault {
+            enable = true;
+            enableSSHSupport = true;
+          };
+          services.openssh.enable = lib.mkDefault true;
+
+          # It's following the 'nixpkgs' flake input which should be in unstable
+          # branches. Not to mention, most of the system configurations should
+          # have this attribute set explicitly by default.
+          system.stateVersion = lib.mkDefault "23.11";
+        })
       ];
   };