#!/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)
  (match (filesystem-change-evt file (λ () #f))
    [#f
      (displayln "error watching file...")
      (sleep 1)]
    [chg-evt
      (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)))