(in-package #:monparser)

(defclass parser-input ()
  ((cursor :initarg :cursor :accessor input-cursor :initform 0)
   (data :initarg :data :reader input-data :initform nil)))

(defun has-data? (input)
  (< (input-cursor input) (length (input-data input))))

(defun peek (input)
  (char (input-data input)
        (input-cursor input)))

(defun advance (input)
  (make-instance 'parser-input
                 :data (input-data input)
                 :cursor (+ (input-cursor input) 1)))

(defun cursor-distance (input1 input2)
  (- (input-cursor input1) (input-cursor input2)))

(defun line-and-column (input)
  (let ((line 1) (column 1))
    (dotimes (i (input-cursor input))
      (let ((c (char (input-data input) i)))
        (case c
          (#\Newline
           (incf line)
           (setf column 1))
          (t (incf column)))))
    (values line column)))