gistfile1.el

(defvar concerto-default-username (format "%s@%s" (user-login-name) (system-name)))

(defvar concerto-username nil)

(defvar concerto-broadcast-buffer-name "*concerto*")

(defun concerto-init-broadcast-buffer (connection buffer)
  (with-current-buffer buffer
    (message "Joining concerto as %s" concerto-username)
    (setq buffer-read-only t)
    (pop-to-buffer (current-buffer))))

(defun concerto-broadcast-buffer (&optional noprompt)
  "Return the broadcast buffer, create if necessary."
  (let ((buffer (get-buffer concerto-broadcast-buffer-name)))
    (or (if (buffer-live-p buffer) buffer)
        (let ((connection (get-process nrepl-connection-buffer)))
          (concerto-init-broadcast-buffer connection (get-buffer-create concerto-broadcast-buffer-name))))))

(defun concerto-broadcast-handler (buffer)
  (lexical-let ((buffer buffer))
    (lambda (response)
      ((nrepl-dbind-response response (username broadcast)
         (message "%s: %s" username broadcast))))))


(defun concerto-join-handler (buffer)
  (nrepl-make-response-handler buffer
                               nil
                               nil
                               (lambda (buffer err)
                                 (message (format "%s" err)))
                               (lambda (buffer)
                                 (message "Joined!"))))

(defun concerto-join ()
    (nrepl-send-request (list "op" "join"
                              "username" concerto-username)
                        (concerto-init-broadcast-buffer-handler concerto-concerto-buffer)))

;;;###autoload
(defun concerto (username)
  (interactive (list (read-string "Username: " concerto-default-username nil concerto-default-username)))
  (setq concerto-username username)
  (concerto-join))