#!/usr/bin/env racket
#lang racket

(require racket/rerequire racket/runtime-path)

(define (reinvoke file)
  (displayln "invoking module")
  (define p (build-path file))
  (dynamic-rerequire p)
  (dynamic-require (list 'submod p 'main) #f)
  (displayln "invocation complete"))

(define (watch-forever file)
  (sleep 0.2)
  (define chg-evt (filesystem-change-evt file (lambda ()
                                                (displayln "error watching file...")
                                                (sleep 1) (watch-forever file))))
  (define runner (thread (lambda () (reinvoke file))))

  (define (handle-break _)
    (cond
      [(sync/timeout 0 runner)
       (displayln "exiting")
       (exit)]
      [else
       (displayln "killing module")
       (kill-thread runner)
       (filesystem-change-evt-cancel chg-evt)]))

  (with-handlers ([exn:break? handle-break])
    (sync chg-evt)
    (kill-thread runner))
  (watch-forever file))

(define-runtime-path aoc "aoc.rkt")
(command-line
  #:program "watch"
  #:args (day)
  (displayln "warming up")
  (dynamic-require aoc #f)
  (displayln "ready to go!")
  (watch-forever (format "~a.rkt" day)))