(in-package :lisp-on-lines)

(define-layered-function display-using-description (description object component)
;  (:argument-precedence-order )
  (:method-combination wrapping-standard)
  (:documentation
   "Render the object in component, 
    using DESCRIPTION, which is an occurence, an attribute, or something else entirely."))

(define-layered-method
    display-using-description (d o c)
    (<:as-html "default :" o))

(defmethod find-layer-for-type (type)
  type)


(define-layered-function display (component object &rest args)
  (:documentation
   "Displays OBJECT in COMPONENT."))

(define-layered-method display ((component t) (object t)
				&rest properties
				&key type (line #'line-in)
				&allow-other-keys)
  " The default display dispatch method

  DISPLAY takes two required arguments, 
  COMPONENT : The component to display FROM (not neccesarily 'in')
  OBJECT : The 'thing' we want to display... in this case it's the component

  DISPLAY also takes keywords arguments which modify the DESCRIPTION,
  that is to say the parameters that come together to create the output.

The default display calls out via FUNCALL-WITH-LAYERS to tche DISPLAY-USING-DESCRIPTION method."

  (let* ((description (find-occurence object)))

    (if description
	(dletf (((description.type description) type)
		((attributes description) (or
					   (attributes description)
					   (list-slots object))))
	  ;; apply the default line to the description
	  (funcall-with-description
	   description
	   (funcall line object)
	   ;; apply the passed in arguments and call display-using-description
	   #'(lambda ()		 
	       (funcall-with-description
		description
		properties
		#'display-using-description description object component))))
	(error "no description for ~A" object))))

;;;;; Macros


(defun funcall-with-description (description properties function &rest args)
  
  (if description
      (dletf* (((description.type description) (or
						(getf properties :type)
						(description.type description)))
	    
	       ((description.layers description) (append 
							 (description.layers description)
							 (getf properties :layers)))
	       ((description.properties description) (append (description.properties description) properties)))
	(funcall-with-layers 
	 (description.layers description)
	 #'(lambda ()
	     (contextl::funcall-with-special-initargs
	      (list (cons description properties))
	      #'(lambda ()
		  (apply function args))))))
      (apply function args)))



(defmacro with-description ((description &rest properties) &body body)
  `(funcall-with-description ,description (if ',(cdr properties)
					       (list ,@properties)
					       ,(car properties))
    #'(lambda ()
	,@body)))

(define-layered-function find-do-attributes (desc))

(define-layered-method find-do-attributes ((description description))

  (loop
     :for att
     :in (attributes description)
     :collect (let ((default (find (car (ensure-list att))
				   (default-attributes description)
				   :key #'car)))
		(or default att))))

(defmacro do-attributes ((var description &optional (attributes `(find-do-attributes ,description))) &body body)
  (with-unique-names (att properties type)
    `(dolist* (,att  ,attributes)
       (let* ((,att (ensure-list ,att))
	      (,properties (rest ,att))
	      (,type (getf ,properties :type))
	      (,var (let ((a (find-attribute ,description (first ,att))))
		      (if ,type
			  (apply #'make-attribute :name (first ,att) :type ,type ,properties)
			  (if a a (make-attribute :name (first ,att) :slot-name (first ,att)))))))
	 (funcall-with-description ,var ,properties
				   #'(lambda ()
				       ,@body))))))

(defmacro with-component ((component) &body body)
  `(let ((self ,component))
    (declare (ignorable self))
    (flet ((display* (thing &rest args)
	     (apply #'display ,component thing args))
	   (display-attribute (attribute obj &optional props)
	     (if props
		 (funcall-with-description
		  attribute props
		  #'display-using-description attribute obj ,component)
		 (display-using-description attribute obj ,component))))
      (declare (ignorable #'display* #'display-attribute))
      ,@body)))

(defmacro defdisplay (&body body)
  (loop with in-layerp = (eq (car body) :in-layer)
	with layer = (if in-layerp (cadr body) 't)
	for tail on (if in-layerp (cddr body) body)
	until (listp (car tail))
	collect (car tail) into qualifiers
	finally
	(when (member :in-layer qualifiers)
	  (error "Incorrect occurrence of :in-layer in defdisplay. Must occur before qualifiers."))
	(return
	  (destructuring-bind (description &optional object component) (car tail) 
	    (with-unique-names (d c)
	      (let (standard-description-p)
		`(define-layered-method
		  display-using-description
		  :in-layer ,layer
		  ,@qualifiers

		  ,@(unless object
			    (setf object description)
			    (setf description d)
			    nil)
		  (,(cond
		     ((listp description)
		      (setf d (car description))
		      description)
		     (t
		      (setf d description)
		      (setf standard-description-p t)
		      `(,d description)))
		   ,object
		   ,(cond
		     ((null component)
		      `(,c component))
		     ((listp component)
		      (setf c (car component))
		      component)
		     (t
		      (setf c component)
		      `(,c component))))
		  (with-component (,c)  
			 ,@(cdr tail)))))))))