nixos-config/system/update-lib.nix

nixos-rebuild:
let
  pkgs = import <nixpkgs> {};
  inherit (import ../common/lib.nix) writeHaskellScript get-niv-path home-manager gcRetentionDays;
  configPath = "/etc/nixos";
  update-system = writeHaskellScript {
      name = "update-system";
      bins = [ get-niv-path nixos-rebuild ];
    }
    ''
    getNivPath = readTrim . get_niv_path "${configPath}/nix/sources.nix"

    getNivAssign name = tag <$> getNivPath name
        where tag str = ["-I", [i|#{name}=#{str :: LBS.ByteString}|] ]

    main = do
        paths <- fmap concat . mapM getNivAssign $ ["nixpkgs", "unstable", "home-manager"]
        nixos_rebuild (paths ++ ["switch"])
    '';
  system-maintenance = writeHaskellScript
    { name = "system-maintenance"; bins = [ pkgs.nix pkgs.git update-system ];} ''
    main = do
      git "-C" "${configPath}" "pull"
      update_system
      nix_collect_garbage "--delete-older-than" "${toString gcRetentionDays}d"
      nix "optimise-store"
  '';
in
{
  inherit update-system system-maintenance;
}