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

;; Copyright (C) 2022

;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.

(use-modules (srfi srfi-1)
             (ice-9 match)
             (advent-of-code))

(define (all-different? list)
  (match list
    (() '())
    ((_) #t)
    ((head . tail) (if (member head tail)
                       #f
                       (all-different? tail)))))

(define (solution input marker-length)
  (let loop ((position 0))
    (let ((marker (take (drop input position) marker-length)))      
      (if (all-different? marker)
          (+ position marker-length)
          (loop (+ position 1))))))

(should-equal (all-different? '(a b c d)) #t)
(should-equal (all-different? '(a a b c)) #f)
(should-equal 7 (solution (string->list "mjqjpqmgbljsphdztnvjfqwrcgsmlb") 4))
(should-equal 5 (solution (string->list "bvwbjplbgvbhsrlpgdmjqwftvncz") 4))
(should-equal 6 (solution (string->list "nppdvjthqldpwncqszvftbrmjlhg") 4))
(should-equal 10 (solution (string->list "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg") 4))
(should-equal 11 (solution (string->list "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw") 4))
(should-equal 1794 (solution (string->list (read-file "input.txt")) 4))