#lang curly-fn racket

(require "scripts/aoc.rkt")

;; solution for day 8

(struct insn [type arg] #:transparent)

;; helper functions here

(define (part1 input)
  (define (execute pc acc [seen (mutable-set)])
    (if (set-member? seen pc)
      acc
      (let ([in (list-ref input pc)])
        (set-add! seen pc)
        (match (insn-type in)
          ["nop" (execute (add1 pc) acc seen)]
          ["jmp" (execute (+ pc (insn-arg in)) acc seen)]
          ["acc" (execute (add1 pc) (+ acc (insn-arg in)) seen)]
          [x (error "not shonks" x)]))))
  (execute 0 0))

(define (part2 input)
  (define (execute-actual input)
    (define (execute pc acc [seen (mutable-set)])
      (if (>= pc (length input))
        acc
        (let ([in (list-ref input pc)])
          (set-add! seen pc)
          (match (insn-type in)
            ["nop" (execute (add1 pc) acc seen)]
            ["jmp" (execute (+ pc (insn-arg in)) acc seen)]
            ["acc" (execute (add1 pc) (+ acc (insn-arg in)) seen)]
            [x (error "not shonks" x)]))))
    (execute 0 0))

  (define target-pc (length input))
  (for ([in (in-list input)] [i (in-naturals)] #:unless (string=? "acc" (insn-type in)))
    (define new-type (if (string=? (insn-type in) "jmp") "nop" "jmp"))
    (define new-insn (insn new-type (insn-arg in)))
    ;; aaaa
    (define vec (vector-copy (list->vector input)))
    (vector-set! vec i new-insn)
    (define new-prg (vector->list vec))
    (with-handlers ([exn? (lambda (x) (answer 8 2 (execute-actual new-prg)))])
      (part1 new-prg))))

(module+ test
  (require rackunit)
  ;; tests here
  (displayln "no tests :("))

(module+ main
  (define input
    (for/list ([line (in-list (file->lines "inputs/8"))])
      (match (string-split line)
        [(list a b) (insn a (string->number b))]
        [x (error "not shonks" x)])))
  ;; part 1
  (answer 8 1 (part1 input))

  ;; part 2
  (answer 8 2 (part2 input))

  (displayln "meow"))