guix-jupyter-kernel: Use 'serve-kernels'.

* guix-jupyter-kernel.scm (heartbeat-handler, start-kernel): Remove.
(general-handler): Adjust prototype to match what 'serve-kernels'
expects.
<top level>: Use 'serve-kernels'.

guix-jupyter-kernel.scm

@@ -84,21 +84,17 @@ acts as a proxy to an actual kernel."
 ;; Handlers.
 ;;
 
-(define (heartbeat-handler kernel)
-  (let ((message (zmq-message-receive-bytevector (kernel-heartbeat kernel)
-                                                 (zmq-msg-init))))
-    (zmq-message-send-bytevector (kernel-heartbeat kernel) message))
-  (heartbeat-handler kernel))
-
-
-(define (general-handler kernel containers count)
-  (let* ((message (read-message kernel))
-         (handler (dispatch (message-type message))))
-    (pub-busy kernel message)
-    (let-values (((containers count)
-                  (handler kernel message containers count)))
-      (pub-idle kernel message)
-      (general-handler kernel containers count))))
+(define (general-handler kernel kind message state)
+  "Handle MESSAGE, which was sent by KERNEL, a client of ours, on KIND (one
+of 'kernel-shell', 'kernel-stdin', etc.)"
+  (match state
+    ((containers count)
+     (let ((handler (dispatch (message-type message))))
+       (pub-busy kernel message)
+       (let-values (((containers count)
+                     (handler kernel message containers count)))
+         (pub-idle kernel message)
+         (list containers count))))))
 
 ;; Unknown request type, ignore it.
 (define (ignore-request kernel message containers count)
@@ -287,12 +283,6 @@ MESSAGE."
                    %namespaces 1
                    exec)))
 
-(define (start-kernel pid kernel)
-  (let ((default-container (alist->vhash
-                            `(("default" .
-                               ,(new-container-connect "default" pid))))))
-    (general-handler kernel default-container 0)))
-
 
 (define (exit-handler kernel)
   (lambda _
@@ -304,5 +294,11 @@ MESSAGE."
                 connection-file->kernel)))
   (sigaction SIGTERM (exit-handler kernel))
   (sigaction SIGINT  (exit-handler kernel))
-  (start-kernel (start-container kernel "default" '())
-                kernel))
+
+  (let* ((pid        (start-container kernel "default" '()))
+         (containers (vhash-cons "default"
+                                 (new-container-connect "default" pid)
+                                 vlist-null)))
+   (serve-kernels (list kernel)
+                  general-handler
+                  (list containers 0))))