;;; autoconf.el --- mode for editing Autoconf configure.ac files

;; Copyright (C) 2000-2017 Free Software Foundation, Inc.

;; Author: Dave Love <fx@gnu.org>
;; Keywords: languages

;; 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Provides fairly minimal font-lock, imenu and indentation support
;; for editing configure.ac files.  Only Autoconf syntax is processed.
;; There is no attempt to deal with shell text -- probably that will
;; always lose.

;; This is specialized for configure.ac files.  It doesn't inherit the
;; general M4 stuff from M4 mode.

;; There is also an autoconf-mode.el in existence.  That appears to be
;; for editing the Autoconf M4 source, rather than configure.ac files.

;;; Code:

(require 'info-look)

(defvar autoconf-mode-map (make-sparse-keymap))

(defvar autoconf-mode-hook nil
  "Hook run by `autoconf-mode'.")

(defconst autoconf-definition-regexp
  "A\\(?:H_TEMPLATE\\|C_\\(?:SUBST\\|DEFINE\\(?:_UNQUOTED\\)?\\)\\)(\\[*\\(\\(?:\\sw\\|\\s_\\)+\\)\\]*")

(defvar autoconf-font-lock-keywords
  `(("\\_<A[CHMS]_\\(?:\\sw\\|\\s_\\)+" . font-lock-keyword-face)
    (,autoconf-definition-regexp
     1 font-lock-function-name-face)
    ;; Are any other M4 keywords really appropriate for configure.ac,
    ;; given that we do `dnl'?
    ("changequote" . font-lock-keyword-face)))

(defvar autoconf-mode-syntax-table
  (let ((table (make-syntax-table)))
    (modify-syntax-entry ?\" "." table)
    (modify-syntax-entry ?\n ">" table)
    (modify-syntax-entry ?# "<" table)
    table))

(defvar autoconf-imenu-generic-expression
  (list (list nil autoconf-definition-regexp 1)))

;; It's not clear how best to implement this.
(defun autoconf-current-defun-function ()
  "Function to use for `add-log-current-defun-function' in Autoconf mode.
This version looks back for an AC_DEFINE or AC_SUBST.  It will stop
searching backwards at another AC_... command."
  (save-excursion
    (skip-syntax-forward "w_" (line-end-position))
    (if (re-search-backward autoconf-definition-regexp
                            (save-excursion (beginning-of-defun) (point))
                            t)
        (match-string-no-properties 1))))

(info-lookup-maybe-add-help
 :mode 'autoconf-mode
 :regexp "A[CM]_[_A-Z0-9]+"
 :doc-spec '(;; Autoconf Macro Index entries are without an "AC_" prefix,
	     ;; but with "AH_" or "AU_" for those.  So add "AC_" if there
	     ;; isn't already an "A._".
             ("(autoconf)Autoconf Macro Index"
              (lambda (item)
                (if (string-match "^A._" item) item (concat "AC_" item)))
	      "^[ \t]+-+ \\(Macro\\|Variable\\): .*\\<" "\\>")
             ;; M4 Macro Index entries are without "AS_" prefixes, and
             ;; mostly without "m4_" prefixes.  "dnl" is an exception, not
             ;; wanting any prefix.  So AS_ is added back to upper-case
             ;; names (if needed), m4_ to others which don't already an m4_.
             ("(autoconf)M4 Macro Index"
              (lambda (item)
                (let ((case-fold-search nil))
                  (cond ((or (string-equal item "dnl")
                             (string-match "^m4_" item)
                             ;; Autoconf 2.62 index includes some macros
                             ;; (e.g., AS_HELP_STRING), so avoid prefixing.
                             (string-match "^AS_" item))
                         item)
                        ((string-match "^[A-Z0-9_]+$" item)
                         (concat "AS_" item))
                        (t
                         (concat "m4_" item)))))
	      "^[ \t]+-+ Macro: .*\\<" "\\>")
             ;; Autotest Macro Index entries are without "AT_".
             ("(autoconf)Autotest Macro Index" "AT_"
	      "^[ \t]+-+ Macro: .*\\<" "\\>")
	     ;; This is for older versions (probably pre autoconf 2.5x):
	     ("(autoconf)Macro Index" "AC_"
	      "^[ \t]+-+ \\(Macro\\|Variable\\): .*\\<" "\\>")
	     ;; Automake has index entries for its notes on various autoconf
	     ;; macros (eg. AC_PROG_CC).  Ensure this is after the autoconf
	     ;; index, so as to prefer the autoconf docs.
	     ("(automake)Macro and Variable Index" nil
	      "^[ \t]*['`‘]" "['’]"))
 ;; Autoconf symbols are M4 macros.  Thus use M4's parser.
 :parse-rule 'ignore
 :other-modes '(m4-mode))

;;;###autoload
(define-derived-mode autoconf-mode prog-mode "Autoconf"
  "Major mode for editing Autoconf configure.ac files."
  (setq-local parens-require-spaces nil) ; for M4 arg lists
  (setq-local defun-prompt-regexp "^[ \t]*A[CM]_\\(\\sw\\|\\s_\\)+")
  (setq-local comment-start "dnl ")
  ;; We want to avoid matching "dnl" in other text.
  (setq-local comment-start-skip "\\(?:\\(\\W\\|^\\)dnl\\|#\\) +")
  (setq-local syntax-propertize-function
	      (syntax-propertize-rules ("\\<dnl\\>" (0 "<"))))
  (setq-local font-lock-defaults
	      `(autoconf-font-lock-keywords nil nil))
  (setq-local imenu-generic-expression autoconf-imenu-generic-expression)
  (setq-local indent-line-function #'indent-relative)
  (setq-local add-log-current-defun-function
	      #'autoconf-current-defun-function))

(provide 'autoconf-mode)
(provide 'autoconf)

;;; autoconf.el ends here