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#lang racket
(require advent-of-code
threading
fancy-app
data/collection)
(define (relative-rock-coordinates rock)
(for*/hash ([(row y) (in-indexed (reverse rock))] [(_col x) (in-indexed row)])
(values (cons x y) #true)))
(define rock-shapes
(~> (open-input-file "./2022/day-17/rock-shapes")
port->string
(string-split "\n\n")
(map (λ~> (string-split _ "\n") (map string->list _) relative-rock-coordinates) _)))
(define gusts
(~> (fetch-aoc-input (find-session) 2022 17 #:cache #true)
string-trim
string->list
(map (match-lambda
[#\> 1]
[#\< -1])
_)))
(define (place-new-rock rock elevation)
(for/hash ([(posn _) (in-hash rock)])
(match-define (cons x y) posn)
(values (cons (+ x 3) (+ y elevation 4)) #true)))
(define (gust-move rock wind cave)
(define moved-rock
(for/hash ([(posn _) (in-hash rock)])
(match-define (cons x y) posn)
(define posn* (cons (+ x wind) y))
(if (hash-has-key? cave posn) (values 'collision #t) (values posn* #t))))
(if (hash-has-key? moved-rock 'collision) rock moved-rock))
(for/fold ([cave (hash)]
[falling-rock #f]
[top-of-rocks 0]
[rock-cycle (cycle rock-shapes)]
[rock-number 0]
#:result top-of-rocks)
(#:break (> rock-number 2022) [gust (in-cycle gusts)])
(cond
[(not falling-rock)
(values cave
(~> (first rock-cycle) (place-new-rock top-of-rocks) (gust-move gust cave))
top-of-rocks
(rest rock-cycle)
(add1 rock-number))]))
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