(defun get-message (room-id message-id)
  (cl-json:decode-json-from-string
   (status-200-or-lose
     (drakma:http-request (make-url "/_matrix/client/unstable/rooms/" room-id
                                    "/event/" message-id)
                          :additional-headers `(("Authorization" . ,*bearer*))))))

(snakes:defgenerator context-generator (room-id first-message-id &key (limit 100))
  (let ((message-id first-message-id))
    (block main-loop
      (loop
         (let ((messages (get-messages-from-context room-id message-id :limit limit)))
           (format *debug-io* "Got ~d items from ~a~%" (length messages) message-id)
           (if (null messages)
               (let ((last-message (get-message room-id message-id)))
                 (if (and (string= (cdrassoc :type last-message) "m.room.member")
                          (cdrassoc :replaces--state last-message))
                     (setf message-id (cdrassoc :replaces--state last-message))
                     (return-from main-loop)))
               (progn
                 (dolist (event (reverse messages))
                   (snakes:yield event))
                 (setf message-id (cdrassoc :event--id (first messages))))))))))