class Grape::ErrorFormatter::Json

def ensure_utf8(message)
  return message unless message.respond_to? :encode
  message.encode('UTF-8', invalid: :replace, undef: :replace)
end

def format_structured_message(structured_message)
  ::Grape::Json.dump(structured_message)
end

def wrap_message(message)
  # Use +is_a?+ rather than +case/when+ here. +case/when Hash+ matches via
  # +Module#===+, a C-level real-class check that ignores delegation, so a
  # +SimpleDelegator+ wrapping a Hash (e.g. the +OutputBuilder+ returned by
  # +Grape::Entity#serializable_hash+ when an error is presented via an entity)
  # would fall through and be wrapped in a spurious +{ error: ... }+ envelope.
  # +is_a?+ is forwarded by the delegator to the wrapped Hash, so it matches.
  return message if message.is_a?(Hash)
  return message.as_json if message.is_a?(Exceptions::ValidationErrors)
  { error: ensure_utf8(message) }
end