maxwell/custom/modules/nixpkgs.nix

{ config, lib, ... }:

let
  nixpkgs = config.nixpkgs.source;

  conf = "${toString ../..}/configuration.nix";

  rebuild = self: super:
    { nixos-rebuild = super.nixos-rebuild.overrideAttrs (old:
      { postInstall = old.postInstall +
        ''
          sed -i "$target" \
            -e '/^export PATH/ a \
              export NIX_PATH="nixpkgs=${nixpkgs}:nixos-config=${conf}"' \
            -e 's/remoteSudo=/remoteSudo=1/' \
            -e 's/-A system/-A system --no-out-link/'
        '';
      });
    };

in

{

  options.nixpkgs.source = lib.mkOption
    { type = lib.types.path;
      description = "Nixpkgs sources";
    };

  config =
    { nixpkgs.overlays = [ rebuild ];
      nix.nixPath =
        [ "nixpkgs=/run/current-system/nixpkgs"
          "nixos-config=${conf}"
        ];
      system.extraSystemBuilderCmds = "ln -s ${nixpkgs} $out/nixpkgs";
    };

}