;;;; A program to poke at conditions and restarts with — see conditions.org.
;;;;
;;;; It loops instead of exiting, so `flan dev conditions-play.flan` can attach
;;;; and you can redefine `probe` and `run-once` from Emacs while it runs. The
;;;; socket written here is only a fallback; the daemon overrides it.
(import agent "vendor:agent")

(defstruct AssetMissing [id i32])
(defstruct Corrupt     [id i32])

;;; Handlers cannot see the establishing function's locals yet, so anything a
;;; handler accumulates into has to be a global.
(defvar seen  i64)
(defvar ticks i64)

;;; Two frames under the restart-case, so a transfer has something to cross.
(defn probe [n i32] i32
  (signal (AssetMissing {.id n}))
  100)

(defn middle [n i32] i32
  (defer (set ticks (+ ticks 1)))      ; runs on the way out, transfer or not
  (+ (probe n) 1))

;;; The shape spec-conditions.md §1 uses: a restart-case in value position,
;;; whose fall-through has to produce the type too.
(defn fetch [n i32] i32
  (restart-case (middle n)
    (use-placeholder [] -1)
    (retry           [] 7)))

(defn run-once [] ()
  (print (fetch 1)) (println "")

  (handler-bind [(AssetMissing [c] (set seen (+ seen (i64 (.id c)))))]
    (print (fetch 2)) (println ""))

  (handler-bind [(AssetMissing [c] (invoke-restart 'use-placeholder))]
    (print (fetch 3)) (println ""))

  (print seen) (println "")
  (print ticks) (println ""))

(defn main [] i32
  (agent/start "/tmp/flan-conditions.sock")
  (run-once)
  (while (= (agent/wait 200) 0) 0)
  (run-once)
  (while (= (agent/wait 200) 0) 0)
  (run-once)
  0)