;; gnuserv asynchronous extensions
;; it should be compatible with previous versions for non-extensions

(defvar gnuserv-async-clients '())

(defun gnuserv-delayed-eval (form)
  "Evaluate form, but don't return result to client.
This can be used to implement asynchronous communication: 
The code executed needs to grab the value of the top of the
`gnuserv-current-client' stack and send the value back later 
using (gnuserv-write-to-client client value).
"
  (push gnuserv-current-client 
	gnuserv-async-clients)
  (eval form)
  (setq gnuserv-current-client nil))


(defun gnuserv-async-reply (client form)
  (if (member client gnuserv-async-clients)
      (progn
	(set 'gnuserv-async-clients
	     (remove client gnuserv-async-clients))
	(gnuserv-write-to-client client form))
      (error (format 
	      "Client ID %d is not in gnuserv-async-clients."
	      client))))

(defun gnuserv-reply (value)
  "Send reply to current client if `gnuserv-current-client' is non-nil."
  (if gnuserv-current-client
      (gnuserv-write-to-client gnuserv-current-client 
			       value)))

(defun gnuserv-eval (form)
  "Evaluate form and send back to current client. (see gnuserv-reply)."
  (let ((value (eval form)))
    (gnuserv-reply value)))

(defun gnuserv-write-eval (form)
  "Like gnuserv-eval, but using write semantics. (lisp channel)."
  (let ((value (eval form)))
    (gnuserv-reply (pp-to-string value))))


; (gnuserv-async-reply (gnuserv-async-last-client) 'done)
; (gnuserv-async-reply 4 123)
; (gnuserv-start)
; (gnuserv-write-to-client 4 123)
; gnuserv-async-clients



;; some hacks
(defvar gnuserv-async-edits '())
(defun gnuserv-async ()
  (gnuserv-delayed-eval nil))    ; side effect: gnuserv-eval won't send reply  


(defun gnuserv-async-edit (text)
  (gnuserv-async)
  (let ((buffer 
	 (find-file 
	  (tempfile "async-edit"))))  ; we'll put it in a temp file for safety
    (push (cons buffer (car gnuserv-async-clients))
	  gnuserv-async-edits)
    (insert text)))


(defun fix-unicode-char (x)
  (if (> x 127) 64 x))

(defun fix-unicode-string (str)
  (apply 'string 
	 (mapcar 'fix-unicode-char
		 (string-to-list str))))

(defun gnuserv-async-edit-reply () (interactive)
  (let ((async-edit 
	 (assoc (current-buffer) gnuserv-async-edits)))

    (let ((text (buffer-string)))

      (kill-this-buffer)
      (gnuserv-async-reply 
       (cdr async-edit)
       (pp-to-string               ;; so output can be read to string
	(fix-unicode-string        ;; weird crashes without this...
	 text))))))

; (gnuserv-async-edit-reply)
; gnuserv-async-clients