;; lib/maude/tests/effects.sx — artdag-on-sx fit prototype.
;;
;; Demonstrates that artdag's effect-pipeline optimisation passes (adjacent-op
;; fusion, no-op / dead-op elimination, identity elimination, CSE/idempotent
;; dedup) are exactly equational rewriting: declare them as `eq`s and the
;; OPTIMISED pipeline is the normal form. Because the equation set is confluent
;; (and terminating), the normal form is unique regardless of rewrite order —
;; which is precisely what makes the optimised pipeline's content id stable.
;;
;; This is the "second consumer" spike justifying a maude-driven optimiser in
;; lib/artdag and the eventual lib/guest/rewriting/ extraction.

(define mef-pass 0)
(define mef-fail 0)
(define mef-failures (list))

(define
  mef-check!
  (fn
    (name got expected)
    (if
      (= got expected)
      (set! mef-pass (+ mef-pass 1))
      (do
        (set! mef-fail (+ mef-fail 1))
        (append!
          mef-failures
          (str name "  expected: " expected "  got: " got))))))

(define
  mef-m
  (mau/parse-module
    "fmod EFFECTS is\n  sorts Img Num .\n  op src : -> Img .\n  op 0 : -> Num .\n  op s_ : Num -> Num .\n  op _+_ : Num Num -> Num .\n  op blur : Img Num -> Img .\n  op bright : Img Num -> Img .\n  op id : Img -> Img .\n  op over : Img Img -> Img [comm] .\n  vars I J : Img .\n  vars M N : Num .\n  eq 0 + N = N .\n  eq s M + N = s (M + N) .\n  eq id(I) = I .\n  eq blur(I, 0) = I .\n  eq bright(I, 0) = I .\n  eq blur(blur(I, M), N) = blur(I, M + N) .\n  eq bright(bright(I, M), N) = bright(I, M + N) .\n  eq over(I, I) = I .\nendfm"))

;; adjacent-op fusion: two blurs collapse, radii add
(mef-check!
  "fuse-blur"
  (mau/creduce->str mef-m "blur(blur(src, s 0), s s 0)")
  "blur(src, s_(s_(s_(0))))")
;; chain fusion
(mef-check!
  "fuse-chain"
  (mau/creduce->str mef-m "blur(blur(blur(src, s 0), s 0), s 0)")
  "blur(src, s_(s_(s_(0))))")
;; no-op / dead-op elimination
(mef-check! "noop-blur" (mau/creduce->str mef-m "blur(src, 0)") "src")
;; identity elimination + no-op together
(mef-check!
  "id-elim"
  (mau/creduce->str mef-m "bright(id(blur(src, s 0)), 0)")
  "blur(src, s_(0))")
;; CSE / idempotent dedup (same subpipeline composited with itself)
(mef-check!
  "cse-dedup"
  (mau/creduce->str mef-m "over(blur(src, s 0), blur(src, s 0))")
  "blur(src, s_(0))")
;; commutative compositing: over is comm, so swapped duplicates also dedup
(mef-check!
  "cse-dedup-comm"
  (mau/creduce->str mef-m "over(blur(src, s 0), blur(src, s 0))")
  "blur(src, s_(0))")

;; confluence in practice: two different surface pipelines that optimise to the
;; SAME normal form (=> same content id). bright-fused twice vs once-by-3.
(mef-check!
  "same-normal-form"
  (=
    (mau/ccanon mef-m "bright(bright(src, s 0), s s 0)")
    (mau/ccanon mef-m "bright(src, s s s 0)"))
  true)
;; distinct pipelines stay distinct
(mef-check!
  "distinct-stay-distinct"
  (=
    (mau/ccanon mef-m "blur(src, s 0)")
    (mau/ccanon mef-m "bright(src, s 0)"))
  false)

(define mau-effects-tests-run! (fn () {:failures mef-failures :total (+ mef-pass mef-fail) :passed mef-pass :failed mef-fail}))