(use-package 'cl-ppcre)
(use-package 'trivia)

(defun 06/parse-input-direct (input)
  (mapcar #'parse-integer (split "," (car input))))

(defun 06/parse-input (input-file)
  (06/parse-input-direct (get-file-lines input-file)))

(defun 06/one-iter (parsed-input)
  (let* ((new 0)
         (new-map (mapcar (lambda (x) (if (> x 0) (- x 1) (progn (incf new) 6))) parsed-input)))
    (append new-map (make-list new :initial-element 8))))

(defun 06/part-a (parsed-input)
  (loop for i from 1 upto 80
        do (setf parsed-input (06/one-iter parsed-input)))
  (list-length parsed-input))

(defun 06/another-iter (arr new)
  (loop for i from 8 downto 0
        for n = (aref arr i)
        do (if (zerop i)
               (progn
                 (setf (aref new 8) n)
                 (incf (aref new 6) n))
               (setf (aref new (1- i)) n))))

(defun 06/part-b (parsed-input)
  (let ((initial (make-array 9 :initial-element 0))
        (new (make-array 9)))
    (dolist (i parsed-input) (incf (aref initial i)))
    (loop for x below 256
          do (progn (06/another-iter initial new)
                    (rotatef initial new)))
    (apply #'+ (loop for x below 9
                     collect (aref initial x)))))