;; kwcall.el --- Keyword-index `funcall' -*- lexical-binding: t -*-

;; Author: Philip Kaludercic <philip.kaludercic@fau.de>
;; Version: $Id: kwcall.el,v 1.1 2023/03/20 20:34:58 oj14ozun Exp $

;;; Commentary

;; Some functions in Emacs Lisp have too many argument, due to
;; historical circumstances (eg. `quail-define-package') that make
;; them difficult to invoke.  This is a little and brittle hack to
;; convert optional arguments into keyword arguments.

;;; Code:

;; Example function:
(defun foo (one two three)
  (list three two one))

;; The trick:
(defun kwcall (fn &rest keys)
  "Call FN with indexed parameter names KEYS."
  (unless (symbolp fn)
    (error "Expected %S to be a symbol" fn))
  (let* ((arglist (help-function-arglist fn t)) args)
    (unless (listp arglist)
      (error "Failed to get determine arglist"))
    (when (memq '&rest arglist)
      (error ":funcall is not compatible with varargs"))
    (dolist (arg arglist)
      (push (plist-get keys (intern (format ":%s" arg)))
            args))
    (apply fn (nreverse args))))

;; Example invocation:
(kwcall #'foo :three 3 :one 'I :two "two") ;;=> (3 "two" I)