{ pkgs, lib, system, commons, ... }:
let
  # upstream distro images
  upstreamImagesJSON = lib.importJSON ./upstream.json;
  upstreamImages = lib.mapAttrs (name: src: pkgs.fetchurl src) upstreamImagesJSON.${system};
  templates = (import ./templates.nix) { inherit pkgs lib system commons; };
  customs = (import ./customs.nix) { inherit pkgs lib system commons upstreamImages templates; };
  mergeUpstreamAndCustomImages =
    name: upstreamImage:
      let
        customImages = lib.optionalAttrs (lib.hasAttr "${name}" customs) customs.${name};
      in
      customImages // { upstream = upstreamImage; };

  images = lib.mapAttrs mergeUpstreamAndCustomImages upstreamImages;
in images // { inherit templates; }