;; (setq lexical-binding t)

;; (dbus--annotate-arg '(:array :int32) '(1 2 3))
;; ;=> ((:array :int32 1 :int32 2 :int32 3))

;; (dbus--annotate-arg '(:array (:dict-entry :string :int32)) '(("a" . 1) ("b" . 2)))
;; ;=> ((:array (:dict-entry :string "a" :int32 1) (:dict-entry :string "b" :int32 2)))

;; (dbus--annotate-arg '(:struct :object-path (:array :signature) :string)
;;                     '("path" ("sig") "password"))
;; ;=> ((:struct :object-path "path" (:array :signature "sig") :string "password"))

(defun dbus--annotate-arg (type arg)
  (pcase type
    ((and basic (or :byte :boolean :int16 :uint16 :int32 :uint32
		    :double :string :object-path :signature :unix-fd))
     (list basic arg))
    (`(:array ,elttype)
     (list (cons :array (apply #'nconc
			       (mapcar (lambda (subarg)
					 (dbus--annotate-arg elttype subarg))
				       arg)))))
    (`(,(and symbol (or :variant :struct)) . ,memtypes)
     (list (cons symbol (apply #'nconc
			       (cl-mapcar
				(lambda (memtype subarg)
				  (dbus--annotate-arg memtype subarg))
				memtypes arg)))))
    (`(:dict-entry ,keytype ,valtype)
     (list (cons :dict-entry (nconc (dbus--annotate-arg keytype (car arg))
			      (dbus--annotate-arg valtype (cdr arg))))))
    (_ (error "Unknown type specification: %S" type))))