Added make-js-handler macro.

ChangeLog.rst

@@ -2,6 +2,12 @@
  ChangeLog
 ===========
 
+0.4.0
+=====
+
+* Added function ``make-js-handler``, which allows easily create custom
+  even handlers with Lisp and JS code parts.
+
 0.3.0
 =====
 

src/weblocks-parenscript.lisp

@@ -1,4 +1,3 @@
-(in-package :cl-user)
 (defpackage weblocks-parenscript
   (:use :cl)
   (:import-from #:weblocks/dependencies
@@ -9,12 +8,14 @@
   (:import-from #:weblocks/utils/misc
                 #:md5)
   (:import-from #:parenscript
+                #:chain
                 #:ps
                 #:ps*)
 
   (:export
    #:make-dependency
-   #:make-dependency*))
+   #:make-dependency*
+   #:make-js-handler))
 (in-package weblocks-parenscript)
 
 
@@ -48,3 +49,96 @@ a real filename."
   (make-instance 'parenscript-dependency
                  :type :js
                  :js (ps* parenscript-code)))
+
+
+(defun make-js-code-for-handler (js-code action-code)
+  "Returns Parenscript code, ready to be translated into JavaScript.
+
+   The code from `js-code` will be wrapped into a function which is called
+   immediately with implicit arguments.
+
+   This result is suitable to be used inline as value for HTML attributes like
+   onChange, onClick, etc.
+
+   Args:
+       js-code (list of conses):
+           Parenscript code, returning an object.
+           This object will be passed to the Lisp part of the handler
+           as keyword arguments.
+       action-code (string):
+           A symbol used as a placeholder for the action's id string.
+
+   Returns:
+       Sexps with Parenscript code.
+"
+  `(chain
+    (lambda (,@(car js-code))
+      (let* ((args (progn ,@(cdr js-code)))
+             (args-type (typeof args)))
+        (cond
+          ((equal args-type
+                  "object")
+           (initiate-action-with-args ,action-code "" args "POST"))
+          (t (chain console (error (+ "Arguments, to be passed to the action should be an object, not "
+                                       args-type)))))
+        parenscript:false))
+    (apply this
+           arguments)))
+
+
+(defmacro make-js-handler (&key lisp-code js-code)
+  "Creates a Weblocks action and returns JavaScript code, which can be used as onChange, onClick, etc. handler.
+
+   Args:
+       lisp-code (list-of-conses):
+           First list item should be action's lambda list.
+           Other list items are wrapped into implicit progn.
+       js-code (list of conses):
+           Parenscript code, returning an object.
+           This object will be passed to the Lisp part of the handler
+           as keyword arguments.
+
+   Returns (string):
+       Result is suitable to be used inline as value for HTML attributes like
+       onChange, onClick, etc.
+
+   Handler must be build from two parts JS and Lisp.
+
+   JavaScript part should be written in Parenscript and return
+   an objects. This object will be passed to the backend as
+   keyword arguments for the action, defined by Lisp part of the handler.
+
+   The code from `js-code` will be wrapped into a function which is called
+   immediately with implicit arguments.
+
+   Here is a real world example. This code processes updates of a text
+   in the HTML input. This way you can make a suggest or on fly value validation:
+
+   (:input :value url
+           :name \"url\"
+           :type \"text\"
+           :onchange
+           (weblocks-parenscript:make-js-handler
+            :lisp-code ((&key url)
+                        (update-url (branches widget)
+                                    url))
+            :js-code ((event)
+                      ;; This will pass new URL value
+                      ;; to the backend:
+                      (parenscript:create
+                       :url (@ event target value)))))
+"
+  (unless lisp-code
+    (error "Set the lisp code."))
+  (unless js-code
+    (error "Set the JS code."))
+  (unless (and (consp js-code)
+               (consp (car js-code)))
+    (error "JS code should be a list of forms"))
+
+  (alexandria:with-gensyms (action-code)
+    `(let* ((,action-code (weblocks/actions::function-or-action->action
+                           (lambda ,(car lisp-code)
+                             ,@(cdr lisp-code)))))
+       (ps* (make-js-code-for-handler ',js-code
+                                      ,action-code)))))