stefan-kolb/nucleus

module Nucleus
  module API
    module Middleware
      # Nucleus::Middleware::RequestId, a rack compatible middleware class, assigns the 'HTTP_X_REQUEST_ID'
      # to the current Thread or generates a request ID in the form of
      # a UUID of no request ID was delivered in the request header.
      # The 'X-Request-ID' will also be included in the response header.
      #
      # @author Cedric Roeck (cedric.roeck@gmail.com)
      # @since 0.1.0
      class RequestId
        def initialize(app)
          @app = app
        end

        def call(env)
          # fetch the ID
          Thread.current[:nucleus_request_id] = env['HTTP_X_REQUEST_ID'] || SecureRandom.uuid
          # make sure there is a request id assigned
          env['HTTP_X_REQUEST_ID'] = Thread.current[:nucleus_request_id]
          # execute call
          status, headers, body = @app.call(env)
          # assign ID to response headers
          headers = headers.deep_dup if headers.frozen?
          headers['X-Request-ID'] ||= Thread.current[:nucleus_request_id]
          [status, headers, body]
        end
      end
    end
  end
end