(ql:quickload :qtools)
 (ql:quickload :cells)
 (ql:quickload :qtcore)
 (ql:quickload :qtgui)
 
 (cl:defpackage :tipcalc.models
   (:use :cl :cells)
   (:export
     service-rating tip-calc tax-calc item bill meal-expense-calculator
     rating rate cost tip tax kind item subtotal subtotal total))
 
 (in-package :tipcalc.models)
 
 (defmodel service-rating ()
           ((rating :cell t :accessor rating :initarg :rating :initform (c-in :normal))
            (rate   :cell t :accessor rate   :initform (c? (case (rating self)
                                                             (:normal 0.18)
                                                             (:excellent 0.25)
                                                             (:poor 0.15))))))
 
 (defmodel tip-calc ()
           ((cost :cell t :accessor cost :initarg :cost :initform (c-in 0))
            (rate :cell t :accessor rate :initarg :rate :initform (c-in 0.18))
            (tip  :cell t :accessor tip  :initform (c? (* (cost self)
                                                          (rate self))))))
 
 (defmodel tax-calc ()
           ((cost :cell t :accessor cost :initarg :cost :initform (c-in 0))
            (rate :cell t :accessor rate :initarg :rate :initform (c-in 0.18))
            (tax  :cell t :accessor tax  :initform (c? (* (cost self)
                                                          (rate self))))))
 
 (defmodel item ()
           ((kind :cell t :accessor kind :initarg :kind :initform (c-in :food))
            (cost :cell t :accessor cost :initarg :cost :initform (c-in 0))))
 
 (defmodel bill ()
           ((items :accessor items :initarg :items :initform (c-in nil))
            (cost  :accessor cost  :initform (c? (apply #'+
                                                        (loop for item in (items self)
                                                              collect (cost item)))))))
 
 (defmodel meal-expense-calculator ()
           ((subtotal :accessor subtotal :initarg :subtotal :initform (c-in 0))
            (tax      :accessor tax      :initarg :tax      :initform (c-in 0.08))
            (tip      :accessor tip      :initarg :tip      :initform (c-in 0))
            (total    :accessor total    :initform (c? (+   (subtotal self)     
                                                            (* (tax-rate self)
                                                               (subtotal self))
                                                            (tip self))))))
 
 (defpackage tipcalc
   (:use :cl+qt :tipcalc.models))
 (in-package :tipcalc)
 (in-readtable :qtools)
 
 (define-widget main-window (QWidget) ())
 
 (define-subwidget (main-window cost-widg) (q+:make-qlineedit main-window)
   (setf (q+:placeholder-text cost-widg) "Meal Cost?"))
 
 (define-subwidget (main-window rate-widg) (q+:make-qlineedit main-window)
   (setf (q+:placeholder-text rate-widg) "Tip Rate?"))
 
 (define-subwidget (main-window tip-widg) (q+:make-qlineedit main-window)
   (setf (q+:placeholder-text tip-widg) "Tip . . ."))
 
 (define-subwidget (main-window layout) (q+:make-qhboxlayout main-window)
   (q+:add-widget layout cost-widg)
   (q+:add-widget layout rate-widg)
   (q+:add-widget layout tip-widg))
 
 (defparameter *tip-calc* (make-instance 'tip-calc))
 (cells:defobserver tip  ((self tip-calc))
                    ; I want this to run:
                    ; EITHER When the old value is not bound
                    ; OR     When the old value is not equal to the new value
                    (when (or (not old-value-boundp) (/= new-value old-value))
                      (setf (q+:text)
                          (format nil "~a" new-value))))
 
 
 (defun main ()
   (with-main-window (window (make-instance 'main-window))))