(defvar *part1* "inputs/day06-part1")
(defvar *part1-test* "inputs/day06-part1-test")

(defstruct move x y direction)

(defstruct guard direction x y (moves (make-hash-table :test 'equalp)))

(defun convert-direction (g)
  (case g
    (^ 'up)
    (> 'right)
    (< 'left)
    (v 'down)))


(defun find-guard (map)
  (destructuring-bind (rows cols) (array-dimensions map)
    (loop for j from 0 below rows
          do (loop for i from 0 below cols
                   for v = (aref  map j i)
                   when (not (or (eql '|.| v) (eql '|#| v)))
                     do (return-from find-guard (make-guard :direction (convert-direction v) :x i :y j ))))))

(defun turn-guard (guard)
  (case (guard-direction guard)
    (UP (setf (guard-direction guard) 'RIGHT))
    (DOWN (setf (guard-direction guard) 'LEFT))
    (LEFT (setf (guard-direction guard) 'UP))
    (RIGHT (setf (guard-direction guard) 'DOWN))))

(defun on-map (map x y)
  (destructuring-bind (rows cols) (array-dimensions map)
    (and (>= x 0) (>= y 0)
         (< y rows) (< x cols))))

(defun mark-guard (map guard)
  (setf (aref map (guard-y guard) (guard-x guard)) 'X))

(defun next-pos (guard)
  (case (guard-direction guard)
    (UP (list (guard-x guard) (1- (guard-y guard))))
    (DOWN (list (guard-x guard) (1+ (guard-y guard))))
    (LEFT (list (1- (guard-x guard)) (guard-y guard)))
    (RIGHT (list (1+ (guard-x guard)) (guard-y guard)))))

(defun move-guard (map guard)
  (destructuring-bind (x y) (next-pos guard)
    (if (on-map map x y)
        (if (eql '|#| (aref map y x))
            (turn-guard guard)
            (progn (setf (guard-x guard) x)
                   (setf (guard-y guard) y))) 
        (setf (guard-direction guard) nil))))

(defun run-p1 (file) 
  (let* ((map (list-to-2d-array (read-file file #'to-symbols)))
         (guard (find-guard map)))
    (mark-guard map guard)
    (loop while (guard-direction guard)
          do (mark-guard map guard)
          do (move-guard map guard))
    (destructuring-bind (rows cols) (array-dimensions map)
      (loop for y from 0 below rows sum (loop for x from 0 below cols count (eql (aref map y x) 'X))))))

(defun save-move (guard move)
  (setf (gethash move (guard-moves guard)) t))

(defun reset-moves (guard)
  (setf (guard-moves guard) nil))

(defun is-loop (x y map original-guard)
  ;; can only set new blocks in blank spaces
  (unless (eql '|.| (aref map y x)) (return-from is-loop nil))
  (let ((guard (copy-guard original-guard)))
    ;; save the initial guard position
    (save-move guard (make-move :x (guard-x guard) :y (guard-y guard) :direction (guard-direction guard)))
    ;; set the "new" block
    (setf (aref map y x) '|#|)
    ;; loop and check for guard loops
    (let ((result
            (loop
              while (move-guard map guard)
              for move = (make-move :x (guard-x guard) :y (guard-y guard) :direction (guard-direction guard))
              ;; if we have seen the move before, then it is a loop
              if (gethash move (guard-moves guard))
                return t
              else
                do (save-move guard move)
              finally
                 (return nil))))

      ;; reset initial position
      (setf (aref map y x) '|.|)
      (clrhash (guard-moves guard))
      result)))


(defun run-p2 (file) 
  (let* ((map (list-to-2d-array (read-file file #'to-symbols)))
         (guard (find-guard map)))
    
    (destructuring-bind (rows cols) (array-dimensions map)
      (loop for y from 0 below rows
            sum (loop for x from 0 below cols
                      count (is-loop x y map guard)))
      )))

(defun p1-process-line (line)
  (mapcar #'parse-integer (str:words line)))

(defun line-direction-p (line)
  "make sure the line always goes in the same direction"
  (loop for x in line
        for y in (cdr line)
        count (> x y) into dec
        count (< x y) into inc
        when (and (> dec 0 ) (> inc 0)) return nil
        when (= x y) return nil
        finally (return t)))

(defun line-in-range-p (line)
  "makes sure the delta is within 3"
  (loop for x in line
        for y in (cdr line)
        for delta = (abs (- x y))
        when (or (> delta 3) )
          return nil 
        finally (return t)))

(defun test-line-p (line)
  (and (line-in-range-p line) (line-direction-p line)))

(defun run-p1 (file) 
  (let ((data (read-file file #'p1-process-line)))
    (apply #'+ (mapcar (lambda (line) (if (test-line-p line) 1 0)) data))))

(defun test-line-p2 (line)
  (or (test-line-p (cdr line))
      (test-line-p (cdr (reverse line)))
  (loop for back on line
        collect (car back) into front
        when (test-line-p (concatenate 'list front (cddr back)))
          return t
        finally (return nil)
  )))

(defun run-p2 (file) 
  (let ((data (read-file file #'p1-process-line)))
    (loop for line in data
          count (test-line-p2 line))))