lib: _: rec {
  my = import ./my.nix lib;

  dns = import ./dns.nix;

  isEven = number:
    assert (builtins.isInt number) || (builtins.isFloat number);
      builtins.div number 2 == 0;

  isOdd = !isEven;

  pow = base: exponent:
    assert (builtins.isInt base) && (builtins.isInt exponent);
    assert exponent > 0;
      builtins.foldl' (x: _: x * base) 1 (builtins.genList (_: _) exponent);

  mapListToAttrs = f: xs:
    builtins.listToAttrs (map (name: {
        name =
          if builtins.isList name
          then builtins.elemAt name (builtins.length name - 1)
          else name;
        value = f name;
      })
      xs);

  mkTcpMem = min: ini: max:
    assert min <= ini && ini <= max;
      lib.concatMapStrings (x: toString x + " ") (map (pow 2) [min ini max]);

  # TODO Move these to the NGINX module.
  nginxInternalOnly = ''
    if ($internal != 1) {
      return 403;
    }
    access_log off;
  '';
  nginxAppendHead = text: ''
    sub_filter '</head>' '${lib.concatStrings text}</head>';
    sub_filter_once on;
  '';
  htmlPlausibleScript = {
    domain ? "$host",
    src ? "https://plausible.shire.net/js/script.js",
  }: ''<script defer data-domain="${domain}" src="${src}"></script>'';
}