;;;; cl-scopes/core/actor - basic actor definitions

(defpackage :scopes/core/actor
  (:use :common-lisp)
  (:local-nicknames (:util :scopes/util))
  (:export #:actor #:become #:create #:send
           #:echo #:inc #:lgi
           #:calculator #:plus #:minus #:show))

(in-package :scopes/core/actor)

;;;; basic message and actor implementations

(defclass message ()
  ((content :reader content :initarg :content :initform nil)
   (customer :reader customer :initarg :customer :initform nil)))

(defun message (content &optional customer)
  (make-instance 'message :content content :customer customer))

(defclass actor ()
  ((behavior :accessor behavior :initarg :behavior :initform #'no-op)))

(defgeneric deliver (ac msg)
  (:method ((ac actor) msg) 
    (funcall (behavior ac) ac msg)))
 
;;;; the core (Hewitt) actor API

(defun become (ac bhv)
  (setf (behavior ac) bhv))

(defun create (bhv &optional (cls 'actor))
  (make-instance cls :behavior bhv))

(defun send (addr content &key customer)
  (let ((ac addr) (msg (message content customer))) 
    (deliver ac msg)))

;;;; predefined behaviors

(defun no-op (ac msg))

(defun lgi (ac msg)
  (util:lgi (content msg)))

(defun echo (ac msg)
  (send (customer msg) msg))

;;;; example behavior: calculator

(defun calculator (&optional (val 0))
  #'(lambda (ac msg)
      (destructuring-bind (fn &optional param) (content msg)
        (funcall fn ac msg val param))))

(defun plus (ac msg val param)
  (become ac (calculator (+ val param)))) 
(defun minus (ac msg val param)
  (become ac (calculator (- val param)))) 
(defun show (ac msg val param)
  (send (customer msg) val))