;;~ title    "L0 · summarize a listing"
;;~ author   "lacuna"
;;~ version  1
;;~ mode     automation
;;~ flavor   pink
;;~ id       l0-listing-summary
;;~ touches  ()
;;~ summary  "One-sentence summary of a listing."

;; One-sentence summary of a listing.
;;
;; On-device Sakura. Architect-shape: act 'sakura/decide with a
;; named result handler that type-traps the output. Output must be
;; a non-empty string within length bounds; garbled -> escalate.
;; This is the third star: never claim a thought she didn't have.

(cart 'l0-listing-summary
  '((author    . "lacuna")
    (version   . 1)
    (read-only . #t)))

(define (start ctx)
  (let ((seed (ctx-get 'seed-text ctx)))
    (if (null? seed)
        (escalate 'missing-seed null)
        (next 'invoke-sakura ctx))))

(define (invoke-sakura ctx)
  (let ((seed (ctx-get 'seed-text ctx)))
    (act 'sakura/decide
         (list 'task 'listing-summary seed)
         'check-result)))

(define (check-result ctx)
  (let ((r (ctx-result ctx)))
    (cond
      ((null? r)                          (escalate 'sakura-empty null))
      ((not (string? r))                  (escalate 'sakura-garbled null))
      ((< (string-length r) 1)           (escalate 'sakura-empty null))
      ((> (string-length r) 280)         (escalate 'output-too-long r))
      (else                               (next 'announce (ctx-set 'output r ctx))))))

(define (announce ctx) (done))