lib: let
  inherit (builtins) splitVersion head fromJSON readFile mapAttrs map listToAttrs foldl' attrNames;
  inherit (lib) unique;
  ncVersions = ["29" "30" "31"];

  getMajorVersion = version: head (splitVersion version);

  readJSON = path: fromJSON (readFile path);

  getVersionData = data: {
    inherit (data) url version;
    sha256 = data.hash;
  };
  getByNcVersion = ncVersion: mapAttrs (app: data: {"${getMajorVersion data.version}" = getVersionData data;}) (readJSON ./${ncVersion}.json);

  byNcVersion = map getByNcVersion ncVersions;
  mergeVersions = a: b: let
    allApps = unique (attrNames a ++ attrNames b);
    mergeApp = app: (a.${app} or {}) // (b.${app} or {});
  in
    listToAttrs (map (app: {
        name = app;
        value = mergeApp app;
      })
      allApps);
in
  foldl' (acc: apps: mergeVersions acc apps) {} byNcVersion