;; lib/prolog/tests/programs/member.sx — member/2 generator.

(define pl-mb-test-count 0)
(define pl-mb-test-pass 0)
(define pl-mb-test-fail 0)
(define pl-mb-test-failures (list))

(define
  pl-mb-test!
  (fn
    (name got expected)
    (begin
      (set! pl-mb-test-count (+ pl-mb-test-count 1))
      (if
        (= got expected)
        (set! pl-mb-test-pass (+ pl-mb-test-pass 1))
        (begin
          (set! pl-mb-test-fail (+ pl-mb-test-fail 1))
          (append!
            pl-mb-test-failures
            (str name "\n    expected: " expected "\n    got:      " got)))))))

(define
  pl-mb-goal
  (fn
    (src env)
    (pl-instantiate (nth (first (pl-parse (str "g :- " src "."))) 2) env)))

(define pl-mb-prog-src "member(X, [X|_]). member(X, [_|T]) :- member(X, T).")

(define pl-mb-db (pl-mk-db))
(pl-db-load! pl-mb-db (pl-parse pl-mb-prog-src))

(pl-mb-test!
  "member(2, [1, 2, 3]) succeeds"
  (pl-solve-once!
    pl-mb-db
    (pl-mb-goal "member(2, [1, 2, 3])" {})
    (pl-mk-trail))
  true)

(pl-mb-test!
  "member(4, [1, 2, 3]) fails"
  (pl-solve-once!
    pl-mb-db
    (pl-mb-goal "member(4, [1, 2, 3])" {})
    (pl-mk-trail))
  false)

(pl-mb-test!
  "member(X, []) fails"
  (pl-solve-once!
    pl-mb-db
    (pl-mb-goal "member(X, [])" {})
    (pl-mk-trail))
  false)

(pl-mb-test!
  "member(X, [a, b, c]) generates 3 solutions"
  (pl-solve-count!
    pl-mb-db
    (pl-mb-goal "member(X, [a, b, c])" {})
    (pl-mk-trail))
  3)

(define pl-mb-env-1 {})
(define pl-mb-goal-1 (pl-mb-goal "member(X, [11, 22, 33])" pl-mb-env-1))
(pl-solve-once! pl-mb-db pl-mb-goal-1 (pl-mk-trail))

(pl-mb-test!
  "member(X, [11, 22, 33]) first solution X = 11"
  (pl-num-val (pl-walk-deep (dict-get pl-mb-env-1 "X")))
  11)

(pl-mb-test!
  "member(2, [1, 2, 3, 2, 1]) matches twice on backtrack"
  (pl-solve-count!
    pl-mb-db
    (pl-mb-goal "member(2, [1, 2, 3, 2, 1])" {})
    (pl-mk-trail))
  2)

(pl-mb-test!
  "member with unbound list cell unifies"
  (pl-solve-once!
    pl-mb-db
    (pl-mb-goal "member(a, [X, b, c])" {})
    (pl-mk-trail))
  true)

(define pl-member-tests-run! (fn () {:failed pl-mb-test-fail :passed pl-mb-test-pass :total pl-mb-test-count :failures pl-mb-test-failures}))