(in-package #:input)

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

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

(defun prefix? (target input)
  (string= target
           (data input)
           :start2 (cursor input)
           :end2 (min (+ (cursor input) (length target))
                      (length (data input)))))

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

(defun advance (input &optional (amount 1))
  (make-instance 'input
                 :data (data input)
                 :file (file input)
                 :cursor (1+ (cursor input))))

(defun from-string (str)
  (make-instance 'input :data str))

(defun from-file (filename)
  (make-instance 'input :file filename :data (str:read-file filename)))

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