;;~ title    "Contrast with a similar listing"
;;~ author   "lacuna"
;;~ version  1
;;~ mode     automation
;;~ flavor   pink
;;~ id       contrast-with-similar
;;~ touches  ()
;;~ summary  "How does this listing differ from a near-twin in the shop."

;; How does this listing differ from a near-twin in the shop.
;;
;; Local Sakura runs over one listing's context. precondition_fetch
;; pulls the listing record, sakura/decide produces the summary or
;; comparison, type-trap on the output, then announce.

(cart 'contrast-with-similar
  '((author    . "lacuna")
    (version   . 1)
    (read-only . #t)))

(define (start ctx)
  (let ((id (ctx-get 'listing-id ctx)))
    (if (null? id)
        (escalate 'missing-listing-id null)
        (next 'fetch ctx))))

(define (fetch ctx)
  (let ((id (ctx-get 'listing-id ctx)))
    (act 'etsy/listing (list id) 'invoke)))

(define (invoke ctx)
  (let ((listing (ctx-result ctx)))
    (cond
      ((null? listing)              (escalate 'no-data null))
      ((eq? listing 'rate-limited)  (after 30 'fetch ctx))
      (else (act 'sakura/decide
                 (list 'task 'contrast-with-similar listing)
                 '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))
      (else                       (next 'announce (ctx-set 'output r ctx))))))

(define (announce ctx) (done))