{
  config,
  lib,
  pkgs,
  ...
}:
let
  cfg = config.personal.nix;
in
{
  options.personal.nix = {
    enable = lib.mkEnableOption "nix configuration";
    gc.enable = lib.mkEnableOption "garbage collection";
  };

  config = lib.mkIf cfg.enable (
    lib.mkMerge [
      {
        nixpkgs = {
          config.allowUnfree = true;
          flake = lib.mkDefault {
            setNixPath = false;
            setFlakeRegistry = false;
          };
        };
        nix = {
          package = pkgs.lix;
          settings = {
            auto-optimise-store = true;
            experimental-features = [
              "nix-command"
              "flakes"
              "recursive-nix"
            ];
            substituters = [
              "https://devenv.cachix.org/"
              "https://nix-community.cachix.org/"
            ];
            trusted-public-keys = [
              "devenv.cachix.org-1:w1cLUi8dv3hnoSPGAuibQv+f9TZLr6cv/Hm9XgU50cw="
              "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
            ];
          };
          extraOptions = ''
            !include secrets.conf
          '';
          registry.my-nixpkgs = {
            from = {
              type = "indirect";
              id = "my-nixpkgs";
            };
            to = {
              type = "github";
              owner = "qaristote";
              repo = "my-nixpkgs";
            };
          };
        };
      }

      (lib.mkIf cfg.gc.enable {
        nix.gc = {
          automatic = true;
          dates = "daily";
          options = "--delete-old";
        };
        systemd.services = {
          nix-gc = {
            after = [ "nixos-upgrade.service" ];
            personal.monitor = true;
          };
          nix-gc-remove-dead-roots = {
            enable = cfg.gc.enable;
            description = "Remove dead symlinks in /nix/var/nix/gcroots";
            serviceConfig.Type = "oneshot";
            script = "find /nix/var/nix/gcroots -xtype l -delete";
            before = [ "nix-gc.service" ];
            wantedBy = [ "nix-gc.service" ];
            personal.monitor = true;
          };
          nix-gc-remove-old-hm-gens =
            let
              user = config.personal.user;
            in
            {
              enable = user.enable && user.homeManager.enable;
              description = "Remove old Home Manager generations for user ${user.name}";
              serviceConfig.Type = "oneshot";
              script = "${pkgs.nix}/bin/nix-env --profile /home/${user.name}/.local/state/nix/profiles/home-manager --delete-generations old";
              before = [ "nix-gc.service" ];
              wantedBy = [ "nix-gc.service" ];
              personal.monitor = true;
            };
        };
      })
    ]
  );
}