def before
path = env[Grape::Http::Headers::PATH_INFO].dup
path.sub!(mount_path, '') if mounted_path?(path)
if prefix && path.index(prefix) == 0
path.sub!(prefix, '')
path = Grape::Router.normalize_path(path)
end
pieces = path.split('/')
potential_version = pieces[1]
return unless potential_version =~ options[:pattern]
throw :error, status: 404, message: '404 API Version Not Found' if options[:versions] && !options[:versions].find { |v| v.to_s == potential_version }
env[Grape::Env::API_VERSION] = potential_version
end