{ sources ? import ./nix/sources.nix # do // { nixpkgs = ...; }
, nixos-config ? <nixos-config>
}:

let
  eval = import (sources.nixpkgs + "/nixos/lib/eval-config.nix") {
    system = builtins.currentSystem;
    modules = [ nixos-config ];
    specialArgs = { inherit sources; };
  };

  system = eval.config.system.build.toplevel;

  inherit (eval) pkgs;

  action = name: pkgs.writeShellScriptBin name ''
    ${pkgs.nix}/bin/nix-env -p /nix/var/nix/profiles/system --set ${system}
    # NIXOS_INSTALL_BOOTLOADER=1
    ${system}/bin/switch-to-configuration ${name}
  '';
in
pkgs.symlinkJoin {
  name = "switch-to-configuration";
  paths = [
    (action "boot")
    (action "switch")
  ];
}