let
  lib = import <nixpkgs/lib>;

  ensureStoreName = name:
    if builtins.match "^[A-Za-z_][A-Za-z0-9_-]*$" name != null then
      name
    else
      throw "config/web.nix store name '${name}' is invalid. Use letters, numbers, '_' or '-', starting with a letter or '_' .";

  validateStore = name: store:
    let
      _ = ensureStoreName name;
      __ =
        if builtins.isAttrs store then
          null
        else
          throw "config/web.nix stores.${name} must be an attrset.";
      ___ =
        if store ? root && builtins.isPath store.root then
          null
        else
          throw "config/web.nix stores.${name}.root must be a Nix path.";
    in
      store;

  getStores = webConfig:
    let
      stores =
        if builtins.isAttrs webConfig && webConfig ? stores && builtins.isAttrs webConfig.stores then
          webConfig.stores
        else
          throw "config/web.nix must define stores as an attrset.";

      _ = lib.mapAttrs validateStore stores;
    in
      stores;
in
rec {
  inherit getStores;
}