class Aws::SSOCredentials

def read_cached_token
  cached_token = Json.load(File.read(sso_cache_file))
  # validation
  unless cached_token['accessToken'] && cached_token['expiresAt']
    raise ArgumentError, 'Missing required field(s)'
  end
  expires_at = DateTime.parse(cached_token['expiresAt'])
  if expires_at < DateTime.now
    raise ArgumentError, 'Cached SSO Token is expired.'
  end
  cached_token
rescue Errno::ENOENT, Aws::Json::ParseError, ArgumentError
  raise Errors::InvalidSSOCredentials, SSO_LOGIN_GUIDANCE
end