class Aws::S3::Plugins::ExpressSessionAuth::Handler

def call(context)
  context[:s3_express_endpoint] = true if s3_express_endpoint?(context)
  # if s3 express auth, use new credentials and sign additional header
  if context[:auth_scheme]['name'] == 'sigv4-s3express' &&
     !context.config.disable_s3_express_session_auth
    bucket = context.params[:bucket]
    credentials_provider = context.config.express_credentials_provider
    credentials = credentials_provider.express_credentials_for(bucket)
    context[:sigv4_credentials] = credentials # Sign will use this
  end
  with_metric(credentials) { @handler.call(context) }
end

def s3_express_endpoint?(context)
  context[:endpoint_properties]['backend'] == 'S3Express'
end

def with_metric(credentials, &block)
  return block.call unless credentials
  Aws::Plugins::UserAgent.metric('S3_EXPRESS_BUCKET', &block)
end