(in-package #:mazes)

(defclass distances ()
  ((root :initarg :root :accessor root-cell)
   (cells :initarg :cells :initform (make-hash-table) :accessor distance-cells))
  (:documentation "Keeps track of the distance of each cell from the given root cell."))

(defmethod initialize-instance :after ((d distances) &key)
  (setf (gethash (root-cell d) (distance-cells d)) 0))

(defgeneric set-distance (distance &key)
  (:documentation "Set the distance of the given cell from the root cell"))

(defmethod set-distance ((d distances) &key cell distance)
  (let ((cells (distance-cells d)))
    (setf (gethash cell cells) distance)))

(defgeneric distance-all-cells (distances)
  (:documentation "Return a list of cells with their respective distance from root"))

(defmethod distance-all-cells ((d distances))
  (get-hash-keys (distance-cells d)))

(defun make-distance (root)
  (make-instance 'distances :root root))