(ql:quickload '(fiveam str arrows transducers))

(defpackage #:day04
  (:use #:cl #:fiveam)
  (:local-nicknames (#:t #:transducers)))

(in-package #:day04)

(defparameter eg-input "Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11")

(defun matching-numbers (line)
  (destructuring-bind (_card winners haves)
      (uiop:split-string line :separator '(#\: #\|))
    (declare (ignorable _card))
    (intersection
     (mapcar #'parse-integer
             (str:split " " winners :omit-nulls t))
     (mapcar #'parse-integer
             (str:split " " haves :omit-nulls t)))))

(defun solver1 (lines)
  (t:transduce
   (t:comp
    (t:filter-map #'matching-numbers)
    (t:map #'length)
    (t:map #'1-)
    (t:map (lambda (n) (expt 2 n))))
   #'+
   lines))

(defun solver1c (lines)
  (arrows:->>
   (mapcar #'matching-numbers lines)
   (remove-if #'null)
   (mapcar #'length)
   (mapcar #'1-)
   (mapcar (lambda (n) (expt 2 n)))
   (apply #'+)))

(defun solver2 (lines)
  (let* ((line-count (length lines))
         (stash (make-hash-table :size line-count)))
    (loop
      for line in lines
      for i from 0
      for matches = (length (matching-numbers line))
      do (incf (gethash i stash 0))
         (dotimes (j matches)
           (when (< (+ i j 1) line-count)
             (incf (gethash (+ i j 1) stash 0)
                   (gethash i stash))))
      sum (gethash i stash 0))))

(test solutions
  (is (= 13 (solver1 (uiop:split-string eg-input :separator '(#\Newline)))))
  (is (= 13 (solver1c (uiop:split-string eg-input :separator '(#\Newline)))))
  (is (= 18619 (solver1 #p"input")))
  (is (= 18619 (solver1c (uiop:read-file-lines "input"))))
  (is (= 30 (solver2 (uiop:split-string eg-input :separator '(#\Newline)))))
  (is (= 8063216 (solver2 (uiop:read-file-lines "input")))))