; program i/o

; this works, but not using a proper protocol can make it lock up
; pretty easily. 

; next plan: how to do something like  this: 

; [HOST] uds <-> program <-> ssh channel <-> program <-> uds [HOST]

; i.o. to connect two program that ordinarily communicate with
; uds using a secure channel, so authentication is offloaded to unix
; file permissions/login for uds, and ssh identication/encryption for
; the internet channel.

; maybe the first problem to solve is really an object channel over
; ssh between two guile instances.

(define (make-program pid read write) (cons pid (cons read write)))
(define (program-read-port program)   (cadr program))
(define (program-write-port program) (cddr program))
(define (program-pid program) (car program))
(define (program-wait program) (waitpid (program-pid program)))


(define (open-program . program-lst)
  (define (read-port  pair) (car pair))
  (define (write-port pair) (cdr pair))

  ;; create pipes
  (let ((request (pipe))  ;; us -> program
	(reply   (pipe))) ;; program -> us

    ;; fork
    (let ((child-pid (primitive-fork)))
      (if (zero? child-pid)

	(begin ;; child
	  (dup->fdes (read-port request) 0) ;; connect stdin
	  (dup->fdes (write-port reply) 1)  ;; connect stdout
	  (apply execlp program-lst))

	(begin ;; parent
	  (setvbuf (write-port request) _IONBF) ;; turn off buffering
	  (make-program child-pid
			(read-port reply)
			(write-port request)))))))

; TEST

; (define bash (program-connect "bash" "bash"))

; (define (bash-write command)
;   (let ((port (program-write-port bash)))
;     (with-output-to-port port 
;       (lambda ()
; 	(display command)
; 	(newline)))))

; (define (bash-read)
;   (read-line (program-read-port bash)))
  


;; scheme channel, client-server model
;; SERVER = unix domain server