From d88eb390b82759f563895bd688e229af841c0819 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Wed, 7 May 2014 21:59:54 -0400
Subject: [PATCH] WIP

---
 minimart/core.rkt | 211 ++++++++++++++++++++++------------------------
 1 file changed, 102 insertions(+), 109 deletions(-)

diff --git a/minimart/core.rkt b/minimart/core.rkt
index 26fcb00..aa17a55 100644
--- a/minimart/core.rkt
+++ b/minimart/core.rkt
@@ -6,6 +6,8 @@
 (require "functional-queue.rkt")
 (require (only-in web-server/private/util exn->string))
 
+(require rackunit) ;; TODO: split out
+
 (provide (struct-out route)
 	 (struct-out routing-update)
 	 (struct-out message)
@@ -19,9 +21,6 @@
 	 spawn
 	 send
 	 feedback
-	 co-route
-	 route-accepts?
-	 intersect-routes
 	 spawn-world
 	 deliver-event
 	 transition-bind
@@ -32,10 +31,25 @@
 (define pid-stack (make-parameter '()))
 (define log-events-and-actions? (make-parameter #f))
 
-(struct route (subscription? pattern meta-level level) #:prefab)
+;; A Gestalt is a (gestalt (Listof (Vectorof (Pairof Matcher
+;; Matcher)))), representing the total interests of a process or group
+;; of processes. The outer list has a present entry for each active
+;; metalevel, starting with metalevel 0 in the car. The vectors each
+;; have an entry for each active observer level at their metalevel.
+;; The innermost pairs have cars holding matchers representing active
+;; subscriptions, and cdrs representing active advertisements.
+;;
+;;    "... a few standardised subsystems, identical from citizen to
+;;     citizen. Two of these were channels for incoming data — one for
+;;     gestalt, and one for linear, the two primary modalities of all
+;;     Konishi citizens, distant descendants of vision and hearing."
+;;      -- Greg Egan, "Diaspora"
+;;         http://gregegan.customer.netspace.net.au/DIASPORA/01/Orphanogenesis.html
+;;
+(struct gestalt (metalevels) #:prefab)
 
 ;; Events
-(struct routing-update (routes) #:prefab)
+(struct routing-update (gestalt) #:prefab)
 (struct message (body meta-level feedback?) #:prefab)
 
 ;; Actions (in addition to Events)
@@ -43,72 +57,75 @@
 (struct quit () #:prefab)
 
 ;; Actors and Configurations
-(struct process (routes behavior state) #:transparent)
-(struct world (next-pid event-queue process-table downward-routes process-actions) #:transparent)
+(struct process (gestalt behavior state) #:transparent)
+(struct world (next-pid event-queue process-table downward-gestalt process-actions) #:transparent)
 
 ;; Behavior : maybe event * state -> transition
 (struct transition (state actions) #:transparent)
 
-;; Process table maps to these; idea is to avoid redundant signalling
-;; of routing-updates where possible
-(struct trigger-guard (process downward-routes) #:transparent)
+;; TODO: Reintroduce "trigger-guard" from the naive implementation
+;; perhaps. "Process table maps to these; idea is to avoid redundant
+;; signalling of routing-updates where possible"
 
-(define (drop-route r)
-  (match-define (route s? p ml l) r)
-  (and (positive? ml) (route s? p (- ml 1) l)))
+(define (drop-gestalt g)
+  (match-define (gestalt metalevels) g)
+  (gestalt (if (null? metalevels) '() (cdr metalevels))))
 
-(define (lift-route r)
-  (match-define (route s? p ml l) r)
-  (route s? p (+ ml 1) l))
+(define (lift-gestalt g)
+  (gestalt (cons '#() (gestalt-metalevels g))))
 
-(define (sub p #:meta-level [ml 0] #:level [l 0]) (route #t p ml l))
-(define (pub p #:meta-level [ml 0] #:level [l 0]) (route #f p ml l))
+(define (simple-gestalt subs advs level metalevel)
+  (define leaf (cons subs advs))
+  (define vec (make-vector (+ level 1) (cons #f #f)))
+  (vector-set! vec level leaf)
+  (let loop ((n metalevel) (acc (list vec)))
+    (if (zero? n)
+	(gestalt acc)
+	(loop (- n 1) (cons '#() acc)))))
 
-(define (spawn behavior state [initial-routes '()]) (process initial-routes behavior state))
+(define (gestalt-empty) (gestalt '()))
+
+(define (gestalt-union g1 g2)
+  (define (zu sa1 sa2)
+    (cons (matcher-union (car sa1) (car sa2))
+	  (matcher-union (cdr sa1) (cdr sa2))))
+  (define (yu ls1 ls2)
+    (define vl1 (vector-length ls1))
+    (define vl2 (vector-length ls2))
+    (define one-bigger? (> vl1 vl2))
+    (define maxlen (max vl1 vl2))
+    (define minlen (min vl1 vl2))
+    (define result (make-vector maxlen #f))
+    (for ((i (in-range 0 minlen)))
+      (vector-set! result i (zu (vector-ref ls1 i) (vector-ref ls2 i))))
+    (for ((i (in-range minlen maxlen)))
+      (vector-set! result i (vector-ref (if one-bigger? vl1 vl2) i)))
+    result)
+  (define (xu mls1 mls2)
+    (match* (mls1 mls2)
+      [('() mls) mls]
+      [(mls '()) mls]
+      [((cons m1 mls1) (cons m2 mls2)) (cons (yu m1 m2) (xu mls1 mls2))]))
+  (gestalt (xu (gestalt-metalevels g1)
+	       (gestalt-metalevels g2))))
+
+(check-equal? (simple-gestalt 'a 'b 0 0)
+	      (gestalt (list (vector (cons 'a 'b)))))
+(check-equal? (simple-gestalt 'a 'b 2 2)
+	      (gestalt (list '#() '#() (vector (cons #f #f)
+					       (cons #f #f)
+					       (cons 'a 'b)))))
+
+(define (sub p #:meta-level [ml 0] #:level [l 0]) (simple-gestalt (pattern->matcher #t p) #f l ml))
+(define (pub p #:meta-level [ml 0] #:level [l 0]) (simple-gestalt #f (pattern->matcher #t p) l ml))
+
+(define (spawn behavior state [gestalt (gestalt-empty)]) (process gestalt behavior state))
 (define (send body #:meta-level [ml 0]) (message body ml #f))
 (define (feedback body #:meta-level [ml 0]) (message body ml #t))
 
-(define (drop-routes rs) (filter-map drop-route rs))
-(define (lift-routes rs) (map lift-route rs))
-
-(define (co-route r #:level [level-override #f])
-  (match-define (route sub? pat ml l) r)
-  (route (not sub?) pat ml (or level-override l)))
-
-(define (route-accepts? r m)
-  (and (= (message-meta-level m) (route-meta-level r))
-       (equal? (message-feedback? m) (not (route-subscription? r)))
-       (intersect? (message-body m) (route-pattern r))))
-
-(define (intersect-routes rs1 rs2)
-  (let loop1 ((rs1 rs1)
-	      (acc '()))
-    (match rs1
-      ['() (reverse acc)]
-      [(cons r1 rs1)
-       (let loop2 ((rs2 rs2)
-		   (acc acc))
-	 (match rs2
-	   ['() (loop1 rs1 acc)]
-	   [(cons r2 rs2)
-	    (if (and (equal? (route-subscription? r1) (not (route-subscription? r2)))
-		     (= (route-meta-level r1) (route-meta-level r2))
-		     (< (route-level r1) (route-level r2)))
-		(intersect (route-pattern r1) (route-pattern r2)
-			   (lambda (rr) (loop2 rs2 (cons (struct-copy route r1 [pattern rr]) acc)))
-			   (lambda () (loop2 rs2 acc)))
-		(loop2 rs2 acc))]))])))
-
-(define (filter-event e rs)
-  (match e
-    [(routing-update e-rs)
-     (routing-update (intersect-routes e-rs rs))]
-    [(? message? m)
-     (if (ormap (lambda (r) (route-accepts? r m)) rs) e #f)]))
-
 (define (spawn-world . boot-actions)
   (spawn world-handle-event
-	 (enqueue-actions (world 0 (make-queue) (hash) '() (make-queue))
+	 (enqueue-actions (world 0 (make-queue) (hash) (gestalt-empty) (make-queue))
 			  -1
 			  boot-actions)))
 
@@ -163,19 +180,9 @@
 						(if (world? new-state)
 						    "#<world>"
 						    new-state)))
-				    (struct-copy process p [state new-state]))
-				  values)))
+				    (struct-copy process p [state new-state])))))
        (enqueue-actions w pid new-actions))]))
 
-(define (step-children w)
-  (let-values (((w step-taken?)
-		(for/fold ([w w] [step-taken? #f]) (((pid g) (in-hash (world-process-table w))))
-		  (match-define (trigger-guard p _) g)
-		  (define t (deliver-event #f pid p))
-		  (values (apply-transition pid t w)
-			  (or step-taken? (transition? t))))))
-    (and step-taken? (transition w '()))))
-
 (define (transition-bind k t0)
   (match-define (transition state0 actions0) t0)
   (match-define (transition state1 actions1) (k state0))
@@ -196,56 +203,37 @@
 		(dispatch-event e w))
               '()))
 
-(define (transform-process pid w fp frs)
-  (match (hash-ref (world-process-table w) pid)
+(define (transform-process pid w fp)
+  (define pt (world-process-actions w))
+  (match (hash-ref pt pid)
     [#f w]
-    [(trigger-guard p downward-rs)
-     (struct-copy world w
-       [process-table (hash-set (world-process-table w)
-				pid
-				(trigger-guard (fp p) (frs downward-rs)))])]))
+    [p (struct-copy world w [process-table (hash-set pt pid (fp p))])]))
 
 (define (enqueue-event e w)
   (struct-copy world w [event-queue (enqueue (world-event-queue w) e)]))
 
-(define (upward-routes-change-ignorable? pid w rs)
-  (match (hash-ref (world-process-table w) pid)
-    [#f #t]
-    [(trigger-guard p _) (equal? (process-routes p) rs)]))
-
 (define ((perform-action pid a) w)
   (match a
     [(? process? new-p)
      (let* ((new-pid (world-next-pid w))
 	    (w (struct-copy world w [next-pid (+ new-pid 1)]))
 	    (w (struct-copy world w [process-table
-				     (hash-set (world-process-table w)
-					       new-pid
-					       (trigger-guard new-p '()))])))
+				     (hash-set (world-process-table w) new-pid new-p)])))
        (log-info "Spawned process ~a ~v ~v" new-pid (process-behavior new-p) (process-state new-p))
        (issue-routing-update w))]
     [(quit)
      (when (hash-has-key? (world-process-table w) pid) (log-info "Process ~a terminating" pid))
      (let* ((w (struct-copy world w [process-table (hash-remove (world-process-table w) pid)])))
        (issue-routing-update w))]
-    [(routing-update routes)
-     (if (upward-routes-change-ignorable? pid w routes)
-	 (transition w '())
-	 (let* ((w (transform-process pid w
-				      (lambda (p) (struct-copy process p [routes routes]))
-				      values)))
-	   (issue-routing-update w)))]
+    [(routing-update gestalt)
+     (let* ((w (transform-process pid w
+				  (lambda (p) (struct-copy process p [gestalt gestalt])))))
+       (issue-routing-update w))]
     [(message body meta-level feedback?)
      (if (zero? meta-level)
 	 (transition (enqueue-event a w) '())
 	 (transition w (message body (- meta-level 1) feedback?)))]))
 
-(define (aggregate-routes base w)
-  (apply append
-	 base
-	 (for/list ((g (in-hash-values (world-process-table w))))
-	   (process-routes (trigger-guard-process g)))))
-
 (define (issue-local-routing-update w)
   (enqueue-event (routing-update (aggregate-routes (world-downward-routes w) w)) w))
 
@@ -254,18 +242,23 @@
               (routing-update (drop-routes (aggregate-routes '() w)))))
 
 (define (dispatch-event e w)
-  (for/fold ([w w]) (((pid g) (in-hash (world-process-table w))))
-    (match-define (trigger-guard p old-downward-rs) g)
-    (define e1 (filter-event e (process-routes p)))
-    (match e1
-      [#f w]
-      [(routing-update new-downward-rs)
-       (if (equal? old-downward-rs new-downward-rs)
-	   w
-	   (transform-process pid (apply-transition pid (deliver-event e1 pid p) w)
-			      values
-			      (lambda (old-rs) new-downward-rs)))]
-      [_ (apply-transition pid (deliver-event e1 pid p) w)])))
+  ...)
+
+;; TODO: need explicit indication from a transitioning child as to
+;; whether it is inert or not. If not, it should be explicitly
+;; scheduled for the next round. The current system of just asking
+;; everyone doesn't scale.
+;;
+;; This is the "schedule" rule of the calculus.
+;;
+(define (step-children w)
+  (let-values (((w step-taken?)
+		(for/fold ([w w] [step-taken? #f]) (((pid g) (in-hash (world-process-table w))))
+		  (match-define (trigger-guard p _) g)
+		  (define t (deliver-event #f pid p))
+		  (values (apply-transition pid t w)
+			  (or step-taken? (transition? t))))))
+    (and step-taken? (transition w '()))))
 
 (define (world-handle-event e w)
   (if (or e (not (quiescent? w)))