;;;; A program that stops, for driving the break loop from an editor.
;;;;
;;;; It errors on its first frame, with nothing having handled the condition,
;;;; so [flan dev] meets a program that is already stopped — which is the state
;;;; an editor has to cope with, and the one that is hardest to arrange on
;;;; purpose later. Two restarts are on offer and they return different values,
;;;; so the transcript says which one was chosen.
;;;;
;;;; After resuming it keeps polling, because the claim worth testing is that
;;;; everything else still works on either side of a break.
(import agent "vendor:agent")

(defstruct Missing [id i32])

(defn fetch [n i32] i32
  (restart-case
    (do (error (Missing {.id n})) 0)
    (use-placeholder [] -1)
    (retry           [] 7)))

(defvar ticks i64)

(defn step [] i64
  (set ticks (+ ticks 1))
  ticks)

;;; A division under a restart-case, called from the editor rather than from
;;; main. It is here for the *other* condition the runtime builds by hand:
;;; ArithError's three fields are a C struct in flan_rt.c and a defstruct in
;;; the prelude, and the break loop's render now reads them field by field,
;;; padding and all. A layout that drifted would show the op in `lhs'.
;;; The operands are parameters so nothing constant-folds the division away.
(defn divide [a i64  b i64] i64
  (restart-case
    (/ a b)
    (use-zero [] 0)))

(defn main [] i32
  (agent/start "/tmp/flan-dev-break-fallback.sock")
  (print (fetch 1)) (println "")
  (dotimes [i 4000]
    (agent/wait 5)
    (set ticks (step)))
  0)