;;; https://adventofcode.com/2022/day/4

;; so, just read two intervals.
;; intervals , separated, two numbers - separated.
;; so. ugh. have a parsing function. maybe ask how to better parse
;; then to calculate "total inclusion" - can go both ways, so 4 checks

(setq test-line "2-4,6-8")
(setq test-line "2-8,3-7")

(require 'cl-ppcre)
;; (cl-ppcre:split "(\\ )" line :with-registers-p nil)
(setq intervals (mapcar #'parse-integer (cl-ppcre:split "(,|-)" test-line)))

(defun line-to-nums (line)
  (mapcar #'parse-integer (cl-ppcre:split "(,|-)" line)))

(defun first-includes-second (l1 r1 l2 r2)
  (and (<= l1 l2) (>= r1 r2)))

(first-includes-second 2 8 3 7)
(first-includes-second 3 8 3 7)
(first-includes-second 4 8 3 7)

(defun first-or-last-includes-another (l1 r1 l2 r2)
  (or (first-includes-second l1 r1 l2 r2)
      (first-includes-second l2 r2 l1 r1)))

(with-open-file (in-file "day4-test-input.txt")
  (let ((running-count 0))
    (loop
      for line = (read-line in-file nil nil)
      while line
      do (if (apply #'first-or-last-includes-another (line-to-nums line))
             (incf running-count 1))
      finally (return running-count))))

(defun count-full-interlaps (filename)
  (with-open-file (in-file filename)
  (let ((running-count 0))
    (loop
      for line = (read-line in-file nil nil)
      while line
      do (if (apply #'first-or-last-includes-another (line-to-nums line))
             (incf running-count 1))
      finally (return running-count)))))

(count-full-interlaps "day4-test-input.txt")
(count-full-interlaps "day4-input.txt")

;; next part - count intervals that "overlap at all", even if by single point
;; could count 'not overlapping' - should be very easy
;; and count total, and deduct

(defun count-any-overlap (filename)
  (with-open-file (in-file filename)
  (let ((running-count-non-overlap 0)
        (total-count 0))
    (loop
      for line = (read-line in-file nil nil)
      while line
      do (let ((nums (line-to-nums line)))
           (if (or (< (second nums) (third nums))
                   (< (fourth nums) (first nums)))
               (incf running-count-non-overlap 1))
           (incf total-count 1)
           )
      finally (return (- total-count running-count-non-overlap))))))

(count-any-overlap "day4-test-input.txt")
(count-any-overlap "day4-input.txt")