Using function passing face non-interactively

[carlmarcos]

I have the following function that works well in an interactive way.  What 
changes are needed to make the function works non-interactively as well?

(defun laxy-descface (facenm)
  "Describe the typeface properties of face name FACENM."

  (interactive
   (list
    (let* ( (cseq '("mode-line" "mode-line-inactive" "text-property")) )
      (completing-read "Face_property: " cseq nil t "text-property"))))

  (pcase facenm
    ("text-property"
        (describe-face (get-text-property (point) 'face)))
    ("mode-line"
        (describe-face (intern facenm)))
    ("mode-line-inactive"
        (describe-face (intern facenm)))))