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

  images = lib.mapAttrs mergeUpstreamImageAndTemplates upstreamImages;
in images // { inherit customs; }