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#lang racket
(require "../lib/utils.rkt")
(require "../lib/obj.rkt")
(define (read-input)
(call-with-input-file "input"
(λ (fp)
(list->vector (get-lines fp)))))
(define schema (read-input))
(define (char-at line col)
(string-ref (vector-ref schema line) col))
(define height (vector-length schema))
(define width (string-length (vector-ref schema 0)))
(define make-num (obj-maker 'line 'col 'value 'length))
(define (scan-nums)
(define nums '())
(let loop ((i 0))
(if (>= i height)
(void)
(let ()
(let loop ((j 0))
(define curline (vector-ref schema i))
(if (>= j width)
(void)
(let ()
(define next 1)
(define (find-next)
(if (or (>= (+ j next) 140)
(not (char-numeric? (char-at i (+ j next)))))
(void)
(let ()
(set! next (+ 1 next))
(find-next))))
(if (char-numeric? (char-at i j))
(let ()
(find-next)
(define value (string->number (substring curline j (+ j next))))
(set! nums (cons (make-num i j value next) nums)))
(void))
(loop (+ j next)))))
(loop (+ 1 i)))))
(reverse nums))
(define nums (scan-nums))
(define (is-symbol? c)
(and (not (char-numeric? c))
(not (char=? #\. c))))
(define (collect-adjacent num)
(define left
(if (= 0 (num 'col))
'()
(list (char-at (num 'line) (- (num 'col) 1)))))
(define right
(if (= width (+ (num 'col) (num 'length)))
'()
(list (char-at (num 'line) (+ (num 'col) (num 'length))))))
(define up
(if (= 0 (num 'line))
'()
(string->list
(substring (vector-ref schema (- (num 'line) 1))
(max 0 (- (num 'col) 1))
(min width (+ (num 'col) (num 'length) 1))))))
(define down
(if (= (- height 1) (num 'line))
'()
(string->list
(substring (vector-ref schema (+ (num 'line) 1))
(max 0 (- (num 'col) 1))
(min width (+ (num 'col) (num 'length) 1))))))
(append left right up down))
(define (is-part-num? num)
(findf is-symbol? (collect-adjacent num)))
(apply + (map (λ (x) (x 'value))
(filter is-part-num? nums)))
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