(defpackage #:s11-cffi
  (:use #:common-lisp #:cffi))

;; private CFFI symbols I need
(eval-when (:compile-toplevel :load-toplevel :execute)
  (import '(cffi::foreign-typedef cffi::define-type-spec-parser
	    cffi::parse-type cffi::unparse cffi::unparse-type
	    cffi::expand-type-to-foreign-dyn)))
;; I also use cffi::name, but decided leaving that fully qualified
;; would reduce confusion.

(in-package #:s11-cffi)

(defclass foreign-in-out-argument (foreign-typedef)
  ((pointee-type :initarg :pointee-type :reader pointee-type))
  (:documentation "TODO"))

(define-type-spec-parser in-out (pointee-type)
  (make-instance 'foreign-in-out-argument
		 :name 'in-out :actual-type (parse-type ':pointer)
		 :pointee-type (parse-type pointee-type)))

(defmethod unparse (name (type foreign-in-out-argument))
  (list name (unparse-type (pointee-type type))))

(defvar .in-out-sink.)
(setf (documentation '.in-out-sink. 'variable)
      "List of in-out output arguments collected by
       call-with-in-out-arguments.")

(defmethod expand-type-to-foreign-dyn
    (value-form var-form body (type foreign-in-out-argument))
  (let ((pointee-type
	  (list 'quote (unparse-type (pointee-type type)))))
    `(with-foreign-object (,var-form ,pointee-type)
       (setf (mem-ref ,var-form ,pointee-type) ,value-form)
       ,@body
       (push (mem-ref ,var-form ,pointee-type) .in-out-sink.))))

(defun call-with-in-out-arguments (thunk)
  "Call thunk, collecting any in-out arguments in foreign
functions called therein, appending them in order to the primary
result."
  (let ((.in-out-sink. '()))
    (multiple-value-call #'values
      (values (funcall thunk))
      (values-list .in-out-sink.))))