;; Jess code to keep track of the currently firing rule
;;
;; This code may be useful in building simple explanation systems
;;
;; This code installs a user function to act as a listener to
;; DEFRULE_FIRED JessEvents. It sets a global variable,
;; ?*current-rule-name*, to be the string representation of the firing
;; rule's name. ***This variable's value is only "current" within the
;; code of a defrule***
;;
;; Written September 2002 by Michael Stiber, from example code in the
;; Jess documentation, section 4.10.1

;; Example of use to automatically set creating rule for asserted facts:
;; (deftemplate afact 
;;    (slot a)
;;    (slot support (default-dynamic (get-current-rule-name))))

(import jess.JessEvent)
(import jess.JessEventAdapter)

(defglobal ?*current-rule-name* = "")

; Sometimes, a function is needed
(deffunction get-current-rule-name () ?*current-rule-name*)

; This is the function we want to install to handle DEFRULE_FIRED events.
; JessEvent.getObject() returns the object of interest in an event, which
; in this case is an Activation. Activation.getRule() returns the active
; Rule, and Rule.getName() returns the rule's name as a String.
(deffunction set-current-rule-name (?evt)
  (if (eq (get-member JessEvent DEFRULE_FIRED) (get ?evt type)) then
    (bind ?*current-rule-name* 
	  (call (call (call ?evt getObject) getRule) getName))))

; We add the function using JessEventAdapter
(call (engine) addJessListener 
      (new JessEventAdapter set-current-rule-name (engine)))

; We make sure that DEFRULE_FIRED events will be produced by setting that
; bit in Rete.eventMask
(set (engine) eventMask 
     (bit-or (get (engine) eventMask) 
	     (get-member JessEvent DEFRULE_FIRED)))