#!/usr/bin/guile -s
!#

(add-to-load-path (format #f "~a/2024" (getcwd)))
;(add-to-load-path (format #f "~a/.." (dirname (current-filename))))

(use-modules
 (aoc-utils)
 (srfi srfi-1)
 (srfi srfi-9)
 (srfi srfi-64)
 (ice-9 regex)
 (ice-9 getopt-long))

(define (xmas? lst)
  (or (equal? lst '(#\X #\M #\A #\S))
      (equal? lst '(#\S #\A #\M #\X))))

(define (check-south matrix x y)
  (let ((to-check (list (matrix-ref matrix x y)
                        (matrix-ref matrix x (+ 1 y))
                        (matrix-ref matrix x (+ 2 y))
                        (matrix-ref matrix x (+ 3 y)))))
    (xmas? to-check)))

(define (check-east matrix x y)
  (let ((to-check (list (matrix-ref matrix x y)
                        (matrix-ref matrix (+ 1 x) y)
                        (matrix-ref matrix (+ 2 x) y)
                        (matrix-ref matrix (+ 3 x) y))))
    (xmas? to-check)))

(define (check-south-east matrix x y)
  (let ((to-check (list (matrix-ref matrix x y)
                        (matrix-ref matrix (+ 1 x) (+ 1 y))
                        (matrix-ref matrix (+ 2 x) (+ 2 y))
                        (matrix-ref matrix (+ 3 x) (+ 3 y)))))
    (xmas? to-check)))

(define (check-south-west matrix x y)
  (let ((to-check (list (matrix-ref matrix x y)
                        (matrix-ref matrix (- x 1) (+ 1 y))
                        (matrix-ref matrix (- x 2) (+ 2 y))
                        (matrix-ref matrix (- x 3) (+ 3 y)))))
    (xmas? to-check)))

(define (part1 matrix)
  (let ((retval 0))
    (do ((x 0 (1+ x)))
        ((> x (1- (matrix-width matrix))))
      (do ((y 0 (1+ y)))
          ((> y (1- (matrix-height matrix))))
        (if (check-south matrix x y)
            (set! retval (1+ retval)))
        (if (check-east matrix x y)
            (set! retval (1+ retval)))
        (if (check-south-east matrix x y)
            (set! retval (1+ retval)))
        (if (check-south-west matrix x y)
            (set! retval (1+ retval)))))
    retval))

;; Part 2

(define (x-mas? lst1 lst2)
  (or (and (equal? lst1 '(#\M #\A #\S))
           (equal? lst2 '(#\M #\A #\S)))

      (and (equal? lst1 '(#\S #\A #\M))
           (equal? lst2 '(#\S #\A #\M)))

      (and (equal? lst1 '(#\S #\A #\M))
           (equal? lst2 '(#\M #\A #\S)))

      (and (equal? lst1 '(#\M #\A #\S))
           (equal? lst2 '(#\S #\A #\M)))))

(define (check-cross matrix x y)
  (let ((diagonal1 (list (matrix-ref matrix (- x 1) (- y 1))
                         (matrix-ref matrix x y)
                         (matrix-ref matrix (+ x 1) (+ y 1))))
        (diagonal2 (list (matrix-ref matrix (+ x 1) (- y 1))
                         (matrix-ref matrix x y)
                         (matrix-ref matrix (- x 1) (+ y 1)))))
    (x-mas? diagonal1 diagonal2)))

(define (part2 matrix)
  (let ((retval 0))
    (do ((x 0 (1+ x)))
        ((> x (1- (matrix-width matrix))))
      (do ((y 0 (1+ y)))
          ((> y (1- (matrix-height matrix))))
        (if (equal? (matrix-ref matrix x y) #\A)
            (if (check-cross matrix x y)
                (set! retval (1+ retval))))))
    retval))

(define option-spec
  '((help (single-char #\h) (value #f))
    (test (single-char #\t) (value #f))))

(define (help)
  (display "main.scm [options] [FILE]
-h, --help   Display this help.
-t, --test   Run test suite
"))

(define (run-parts filename)
  (let ((input (make-matrix (file->matrix filename))))
    (display "Part1: ")
    (display (part1 input))
    (newline)
    (display "Part2: ")
    (display (part2 input))
    (newline)))

(define (main)
  (let* ((options (getopt-long (command-line) option-spec))
         (help-wanted? (option-ref options 'help #f))
         (test-wanted? (option-ref options 'test #f))
         (files (option-ref options '() '())))
    (cond (help-wanted? (help))
          (test-wanted? (run-tests))
          ((= (length files) 1) (run-parts (car files)))
          (else (help)))))

(main)