;;; mh-acros.el --- Macros used in MH-E

;; Copyright (C) 2004 Free Software Foundation, Inc.

;; Author: Satyaki Das <satyaki@theforce.stanford.edu>
;; Maintainer: Bill Wohler <wohler@newt.com>
;; Keywords: mail
;; See: mh-e.el

;; This file is part of GNU Emacs.

;; GNU Emacs 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 2, or (at your option)
;; any later version.

;; GNU Emacs 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., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;; This file contains macros that would normally be in mh-utils.el except that
;; their presence there would cause a dependency loop with mh-customize.el.
;; This file must always be included like this:
;;
;;   (eval-when-compile (require 'mh-acros))
;;
;; It is so named with a silent "m" so that it is compiled first. Otherwise,
;; "make recompile" in Emacs 21.4 fails.

;;; Change Log:

;;; Code:

(require 'cl)
(require 'advice)

;; The Emacs coding conventions require that the cl package not be required at
;; runtime. However, the cl package in versions of Emacs prior to 21.4 left cl
;; routines in their macro expansions. Use mh-require-cl to provide the cl
;; routines in the best way possible.
(defmacro mh-require-cl ()
  "Macro to load \"cl\" if needed.
Some versions of \"cl\" produce code for the expansion of
\(setf (gethash ...) ...) that uses functions in \"cl\" at run
time. This macro recognizes that and loads \"cl\" where
appropriate."
  (if (eq (car (macroexpand '(setf (gethash foo bar) baz))) 'cl-puthash)
      `(require 'cl)
    `(eval-when-compile (require 'cl))))

;; Macros to generate correct code for different emacs variants

(defmacro mh-do-in-gnu-emacs (&rest body)
  "Execute BODY if in GNU Emacs."
  (unless (featurep 'xemacs) `(progn ,@body)))
(put 'mh-do-in-gnu-emacs 'lisp-indent-hook 'defun)

(defmacro mh-do-in-xemacs (&rest body)
  "Execute BODY if in GNU Emacs."
  (when (featurep 'xemacs) `(progn ,@body)))
(put 'mh-do-in-xemacs 'lisp-indent-hook 'defun)

(defmacro mh-funcall-if-exists (function &rest args)
  "Call FUNCTION with ARGS as parameters if it exists."
  (when (fboundp function)
    `(when (fboundp ',function)
       (funcall ',function ,@args))))

(defmacro mh-make-local-hook (hook)
  "Make HOOK local if needed.
XEmacs and versions of GNU Emacs before 21.1 require
`make-local-hook' to be called."
  (when (and (fboundp 'make-local-hook)
             (not (get 'make-local-hook 'byte-obsolete-info)))
    `(make-local-hook ,hook)))

(defmacro mh-mark-active-p (check-transient-mark-mode-flag)
  "A macro that expands into appropriate code in XEmacs and nil in GNU Emacs.
In GNU Emacs if CHECK-TRANSIENT-MARK-MODE-FLAG is non-nil then
check if variable `transient-mark-mode' is active."
  (cond ((featurep 'xemacs)             ;XEmacs
         `(and (boundp 'zmacs-regions) zmacs-regions (region-active-p)))
        ((not check-transient-mark-mode-flag) ;GNU Emacs
         `(and (boundp 'mark-active) mark-active))
        (t                              ;GNU Emacs
         `(and (boundp 'transient-mark-mode) transient-mark-mode
               (boundp 'mark-active) mark-active))))

(defmacro mh-defstruct (name-spec &rest fields)
  "Replacement for `defstruct' from the \"cl\" package.
The `defstruct' in the \"cl\" library produces compiler warnings,
and generates code that uses functions present in \"cl\" at
run-time. This is a partial replacement, that avoids these
issues.

NAME-SPEC declares the name of the structure, while FIELDS
describes the various structure fields. Lookup `defstruct' for
more details."
  (let* ((struct-name (if (atom name-spec) name-spec (car name-spec)))
         (conc-name (or (and (consp name-spec)
                             (cadr (assoc :conc-name (cdr name-spec))))
                        (format "%s-" struct-name)))
         (predicate (intern (format "%s-p" struct-name)))
         (constructor (or (and (consp name-spec)
                               (cadr (assoc :constructor (cdr name-spec))))
                          (intern (format "make-%s" struct-name))))
         (field-names (mapcar #'(lambda (x) (if (atom x) x (car x))) fields))
         (field-init-forms (mapcar #'(lambda (x) (and (consp x) (cadr x)))
                                   fields))
         (struct (gensym "S"))
         (x (gensym "X"))
         (y (gensym "Y")))
    `(progn
       (defun* ,constructor (&key ,@(mapcar* #'(lambda (x y) (list x y))
                                             field-names field-init-forms))
         (list (quote ,struct-name) ,@field-names))
       (defun ,predicate (arg)
         (and (consp arg) (eq (car arg) (quote ,struct-name))))
       ,@(loop for x from 1
               for y in field-names
               collect `(defmacro ,(intern (format "%s%s" conc-name y)) (z)
                          (list 'nth ,x z)))
       (quote ,struct-name))))

(defadvice require (around mh-prefer-el activate)
  "Modify `require' to load uncompiled MH-E files."
  (or (featurep (ad-get-arg 0))
      (and (string-match "^mh-" (symbol-name (ad-get-arg 0)))
           (load (format "%s.el" (ad-get-arg 0)) t t))
      ad-do-it))

(defmacro mh-assoc-ignore-case (key alist)
  "Check if KEY is present in ALIST while ignoring case to do the comparison.
Compatibility macro for Emacs versions that lack `assoc-string',
introduced in Emacs 22."
  (if (fboundp 'assoc-string)
      `(assoc-string ,key ,alist t)
    `(assoc-ignore-case ,key ,alist)))

(provide 'mh-acros)

;; Local Variables:
;; no-byte-compile: t
;; indent-tabs-mode: nil
;; sentence-end-double-space: nil
;; End:

;; arch-tag: b383b49a-494f-4ed0-a30a-cb6d5d2da4ff
;;; mh-acros.el ends here