;;;; util.lisp -- some utilities 

(in-package :oneliners.api)

(defun plist-find (indicator plist &key (test 'eq) (key 'identity))
  (loop for (ind val . more) on plist by #'cddr
        when (funcall test indicator (funcall key ind))
          return val))

(defmacro with-plist ((&rest keys) plist &rest body)
  (let ((the-plist (gensym)))
    `(let ((,the-plist ,plist))
       (let
           ,(loop for key in keys
                  collect `(,key (plist-find (symbol-name ',key)
                                             ,the-plist
                                             :test #'string-equal
                                             :key #'symbol-name)))
         ,@body))))


(defclass queue-buffer ()
  ((front :initform (list))  
   (back :initform (list))   
   (size :initform 0)
   (capacity :initarg capacity)))

(defun make-qb (capacity)
  (make-instance 'queue-buffer :capacity capacity))

(defun qb-empty-p (q)
  (zerop (slot-value q 'size)))

(defun qb-full-p (q)
  (= (slot-value q 'size) (slot-value q 'capacity)))

(defun enqueue-qb (q x)
  (when (qb-full-p q) (dequeue-qb q))
  (with-slots (size back) q
    (push x back)
    (incf size)))

(defun dequeue-qb (q &optional default)
  (with-slots (front back size) q
    (cond
      ((plusp size) 
       (when (null front)
         (setf front (nreverse back)
               back nil))
       (decf size)
       (pop front))

      (t  default))))

(defun qb-look (q)
  "get a list of the queue, but don't remove items from it"
  (with-slots (front back) q
    (nconc (copy-seq front)
           (reverse back))))