let
  lib = import <nixpkgs/lib>;

  validateStorageEntry = name: entry:
    let
      _ =
        if builtins.isAttrs entry then
          null
        else
          throw "config/storage.nix entry '${name}' must be an attrset.";
      __ =
        if entry ? path && builtins.isString entry.path && entry.path != "" then
          null
        else
          throw "config/storage.nix entry '${name}' must define path as a non-empty string.";
      ___ =
        if entry ? source && builtins.isString entry.source && entry.source != "" then
          null
        else
          throw "config/storage.nix entry '${name}' must define source as a non-empty string.";
      ____ =
        if entry ? type && builtins.isString entry.type && entry.type != "" then
          null
        else
          throw "config/storage.nix entry '${name}' must define type as a non-empty string.";
      _____ =
        if entry ? options && builtins.isList entry.options then
          null
        else
          throw "config/storage.nix entry '${name}' must define options as a list.";
      ______ =
        if lib.all builtins.isString entry.options then
          null
        else
          throw "config/storage.nix entry '${name}' options must be a list of strings.";
      _______ =
        if !(entry ? extra) || builtins.isAttrs entry.extra then
          null
        else
          throw "config/storage.nix entry '${name}' field extra must be an attrset when present.";
    in
      entry;

  getStorageConfig = config:
    let
      _ =
        if builtins.isAttrs config then
          null
        else
          throw "config/storage.nix must evaluate to an attrset.";
      __ = lib.mapAttrs validateStorageEntry config;
    in
      config;
in
rec {
  inherit getStorageConfig validateStorageEntry;
}