;;; erblisp.el --- 
;; Time-stamp: <2007-11-23 11:30:08 deego>
;; Copyright (C) 2002 D. Goel
;; Emacs Lisp Archive entry
;; Filename: erblisp.el
;; Package: erblisp
;; Author: D. Goel <deego@gnufans.org>
;; Version: 0.0DEV
;; URL:  http://www.emacswiki.org/cgi-bin/wiki.pl?ErBot
 

 
;; This file is NOT (yet) part of GNU Emacs.
 
;; This is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3, or (at your option)
;; any later version.
 
;; This is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
 

;; See also:


(defvar erblisp-version "0.0dev")

;;==========================================
;;; Code:

(defgroup erblisp nil 
  "The group erblisp"
   :group 'applications)
(defcustom erblisp-before-load-hooks nil "" :group 'erblisp)
(defcustom erblisp-after-load-hooks nil "" :group 'erblisp)
(run-hooks 'erblisp-before-load-hooks)


(defun erblisp-process-msg (msg &optional proc nick tgt)
  "MSG is either a string or a tree.. If it is a tree, it looks
something like 
   '(foo bar (bar foo))

This command sandboxes the message and then processes it.."

  (if (stringp msg)
      (setq msg (erbn-read msg)))
  (format "%s" (eval (erblisp-sandbox-fuzzy msg))))

(defun erblisp-sandbox-quoted-maybe (expr)
  "sandboxes the whole expression even if it starts with a quote."
  (cond
   ((and (listp expr)
	 (equal (first expr) 'quote))
    (cons 'quote
	  (mapcar 'erblisp-sandbox (cdr expr))))
   (t (erblisp-sandbox expr))))


(defun erblisp-sandbox-quoted (expr)
  "Assumes that the expression will result in a quoted thingy and
tries to make sure that we sandbox that whole quoted thing.. "
  (cond
   ((and (listp expr)
	 (equal (first expr) 'quote))
    (cons 'quote
	  (mapcar 'erblisp-sandbox (cdr expr))))
   ((listp expr)
    (list 'erblisp-sandbox-quoted (erblisp-sandbox expr)))
   ;; just an atom 
   (t (erblisp-sandbox expr))))


(defvar erblisp-allowed-words
  '(nil t 
	;; Also consider:
	;; &rest
	;; &optional
	
	)
  "You should add &rest and &optional to this list. 
We WON'T do this by default since this could lead to exploits if you
*happen* to have bound these keywords to weird stuff like 
\(setq &rest (shell-command \"rm -rf /\")) in your .emacs."
)

(defvar erblisp-max-list-length 2000
  "If non-numeric, we will skip this check."
  )

(defun erblisp-safe-length-args-p (list so-far len)
  (let ((cur list)
	stack)
    (while (and cur
		(<= so-far len))
      (if (consp (car cur))
	  (progn (setq cur (car cur))
		 (when (consp (cdr cur))
		   (push (cdr cur) stack)))
	(setq cur (cdr cur)))
      (unless cur
	(setq cur (pop stack)))
      (setq so-far (1+ so-far)))
    (if (<= so-far len)
	t
      nil)))

(defmacro erblisp-check-args (&rest args)
  "All we do in this macro we remove some bindings for things like
&rest, etc, things that do not have values but got passed to us --
this occurs when a user attempts to use &rest in his function
definitions -- see `erblisp-allowed-words'.  

All the arguments to this macro should have been in their evalled form
and hence constants already, so we do not bother protecting against
multiple evaluations here -- evaluating a constant causes no harm.
All we do in this macro we remove some bindings for things like &rest,
etc, things that are not defined, but passed on here in any case."
  `(erblisp-check-args-nascent 
    ,@(remove-if 
       #'(lambda (arg) (and
			(symbolp arg) 
			(not (boundp arg)))) 
       args)))



(defun erblisp-check-args-nascent (&rest args)
  (if (or 
       (not (numberp erblisp-max-list-length))
       (erblisp-safe-length-args-p args 0 erblisp-max-list-length))
      t
    (error "encountered overlong expression, ignoring") nil))




(defun erblisp-sandbox (expr)
  ""
  (cond
   ;; first condition
   ((null expr) nil)
   ;; second condition
   ((listp expr)
    (when (erblisp-check-args expr)
      (let ((fir (first expr)))
	(cond
	 ((listp fir)
	  (cons (erblisp-sandbox fir)
		(mapcar 'erblisp-sandbox (cdr expr))))
	 ((equal (format "%S" fir) "quote")
	  ;; if quoted, it is fine...
	  expr)
	 (t (cons 
	     (if (or (equal 0 (string-match "fs-" (format "%S" fir)))
		     (member fir erblisp-allowed-words))
		 fir
	       (intern (concat "fs-" (format "%S" fir))))
	     (mapcar 'erblisp-sandbox (cdr expr))))))))

   ;; final condition.. --> when the expr is an atom..  It should be a
   ;; a constant..  or an allowed atom.. allowed == prefixed with fs-
   (t (cond
       ((and (symbolp expr) 
	     (equal 0 (string-match "fs-" (format "%s" expr))))
	expr)
       ((equal expr t) expr)
       ((member expr erblisp-allowed-words) expr)
       ((symbolp expr)
	;;(boundp (intern (concat "fs-" (format "%S" expr)))))
	(intern (concat "fs-" (format "%s" expr))))
       ;; other symbol
       ;;((symbolp expr) (list 'quote expr))
       ;; a number or string now..
       ;; this actually happens when they feed byte-compiled code to
       ;; the bot, like:
       ;;, (funcall #[nil "\300\207" [1] 1])    
       ((not (or (symbolp expr) (numberp expr) (stringp expr)))
	(error "%s %s" "Should not reach here.  Quantum Tunnelling! "
	       "What are you trying to feed me? Byte-compiled code? Vectors?"  ))
       (t expr)))
   ))

(defun erblisp-sandbox-fuzzy (expr)
  "Sandboxes a message.. Ensures that the functions are all fs-
and the arguments are NOT variable-names... This one sandboxes
preferably by quoting unless fs-symbol is bound.."
  (cond 

   ;; first condition
   ((null expr) nil)
   
   ;; second condition
   ((listp expr) 
    (let ((fir (first expr)))
      (cond
       ((listp fir)
	(cons (erblisp-sandbox-fuzzy fir))
	(mapcar 'erblisp-sandbox-fuzzy (cdr expr)))
       ((equal (format "%S" fir) "quote")
	;; if quoted, it is fine...
	expr)
       (t (cons 
	   (if (equal 0 (string-match "fs-" (format "%S" fir)))
	       fir
	     (intern (concat "fs-" (format "%S" fir))))
	   (mapcar 'erblisp-sandbox-fuzzy (cdr expr)))))))
   

   ;; final condition.. --> when the expr is an atom..  It should be a
   ;; a constant..  or an allowed atom.. allowed == prefixed with fs-
   (t (cond
       ((and (symbolp expr) 
	     (equal 0 (string-match "fs-" (format "%s" expr))))
	expr)
       ((and (symbolp expr)
	     (or
	      (boundp (intern (concat "fs-" (format "%S" expr))))
	      (fboundp (intern (concat "fs-" (format "%S" expr))))
	     ))
	(intern (concat "fs-" (format "%s" expr))))
       ;; other symbol
       ((symbolp expr) (list 'quote expr))
       ;; a number or string now..

       ((not (or (symbolp expr) (numberp expr) (stringp expr)))
	(error "Should not reach here.  Fuzzy tunnels!"))
       (t expr)))
   ))




(defun erblisp-sandbox-full(expr &optional midstream)
  "
This will ensure that anything rigt after parens is sandboxed by a
fs- prefix.  And anything else is either a symbol , or a string,
but not a variable...  viz: quoted ...else converted into one. 

midstream is in internal variable..."
  (cond
   ((null expr) nil)
   ((listp expr)
    (let* ((fir (first expr)))
      (if (eql fir 'quote)
	  expr
	(cons (erblisp-sandbox-full fir)
	      (mapcar '(lambda (arg)
			 (erblisp-sandbox-full arg t))
		      (cdr expr))))))  
   ;; now we know that expr is a non-nil atom...
   (midstream
    (if (stringp expr) expr
      (list 'quote expr)))



   ;; midstream is untrue... expr is thus an atom at the beginning..
   (t
    (if (equal 0 (string-match "fs-" (format "%s" expr)))
	expr (intern (concat "fs-" (format "%s" expr)))))))

(provide 'erblisp)
(run-hooks 'erblisp-after-load-hooks)



;;; erblisp.el ends here