{ inputs
, lib

, defaultExtraArgs
, defaultNixConf

, ...
}:

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 = {
      # The main desktop.
      ni = {
        systems = [ "x86_64-linux" ];
        formats = null;
        overlays = [
          # Neovim nightly!
          inputs.neovim-nightly-overlay.overlays.default

          # Emacs unstable version!
          inputs.emacs-overlay.overlays.default

          # Helix master!
          inputs.helix-editor.overlays.default

          # Access to NUR.
          inputs.nur.overlay
        ];
        modules = [
          inputs.nur.nixosModules.nur
        ];
      };

      # A remote server.
      plover = {
        systems = [ "x86_64-linux" ];
        formats = null;
        domain = "foodogsquared.one";
        deploy = {
          hostname = "plover.foodogsquared.one";
          auto-rollback = true;
          magic-rollback = true;
        };
      };

      # TODO: Remove extra newlines that are here for whatever reason.
      #{{{
      void = {
        systems = [ "x86_64-linux" ];
        formats = [ "vm" ];
      };
      #}}}

      # The barely customized non-graphical installer.
      bootstrap = {
        systems = [ "aarch64-linux" "x86_64-linux" ];
        formats = [ "install-iso" ];
        nixpkgs-branch = "nixos-unstable-small";
      };

      # The barely customized graphical installer.
      graphical-installer = {
        systems = [ "aarch64-linux" "x86_64-linux" ];
        formats = [ "install-iso" ];
      };

      # The WSL system (that is yet to be used).
      winnowing = {
        systems = [ "x86_64-linux" ];
        formats = null;
        overlays = [
          inputs.neovim-nightly-overlay.overlays.default
        ];
        modules = [
          # Well, well, well...
          inputs.nixos-wsl.nixosModules.default
        ];
      };
    };

    # Only use imports as minimally as possible with the absolute
    # requirements of a host. On second thought, only on flakes with
    # optional NixOS modules.
    sharedModules =
      # Append with our custom NixOS modules from the modules folder.
      import ../../modules/nixos { inherit lib; isInternal = true; }

      # Then, make the most with the modules from the flake inputs. Take
      # note importing some modules such as home-manager are as part of the
      # declarative host config so be sure to check out
      # `hostSpecificModule` function as well as the declarative host setup.
      ++ [
        inputs.nix-index-database.nixosModules.nix-index
        inputs.sops-nix.nixosModules.sops
        inputs.disko.nixosModules.disko

        defaultNixConf
        defaultNixOSConfig
      ];
  };

  flake = {
    # Listing my public NixOS modules if anyone cares.
    nixosModules.default = import ../../modules/nixos { inherit lib; };
  };
}