(in-package #:monparser)

(defstruct parsing
  tree
  left)

(defstruct failure
  place
  message)

(defun new (tree)
  (lambda (input &key lazy)
    (declare (ignore lazy))
    (make-parsing :tree tree :left input)))

(defun bind (parser f)
  (lambda (input &key lazy)
    (let ((r (funcall parser input)))
      (cond ((parsing-p r)
             (if lazy
               (lambda (ignored-input &key lazy)
                 (declare (ignore ignored-input))
                 (funcall (funcall f (parsing-tree r) input)
                          (parsing-left r)
                          :lazy lazy))
               (funcall (funcall f (parsing-tree r) input)
                        (parsing-left r))))
            ((failure-p r)
             r)
            (t (error (format nil "Invalid return value: ~a" r)))))))