;;; easy-mmode.el --- easy definition for major and minor modes.

;; Copyright (C) 1997,2000  Free Software Foundation, Inc.

;; Author:  Georges Brun-Cottan <Georges.Brun-Cottan@inria.fr>
;; Maintainer:  Stefan Monnier <monnier@gnu.org>

;; 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., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; Minor modes are useful and common.  This package makes defining a
;; minor mode easy, by focusing on the writing of the minor mode
;; functionalities themselves.  Moreover, this package enforces a
;; conventional naming of user interface primitives, making things
;; natural for the minor-mode end-users.

;; For each mode, easy-mmode defines the following:
;; <mode>      : The minor mode predicate. A buffer-local variable.
;; <mode>-map  : The keymap possibly associated to <mode>.
;; <mode>-hook : The hook run at the end of the toggle function.
;;       see `define-minor-mode' documentation
;;
;; eval
;;  (pp (macroexpand '(define-minor-mode <your-mode> <doc>)))
;; to check the result before using it.

;; The order in which minor modes are installed is important.  Keymap
;; lookup proceeds down minor-mode-map-alist, and the order there
;; tends to be the reverse of the order in which the modes were
;; installed.  Perhaps there should be a feature to let you specify
;; orderings.

;; Additionally to `define-minor-mode', the package provides convenient
;; ways to define keymaps, and other helper functions for major and minor modes.

;;; Code:

(defmacro easy-mmode-define-toggle (mode &optional doc &rest body)
  "Define a one arg toggle mode MODE function and associated hooks.
MODE is the so defined function that toggles the mode.
optional DOC is its associated documentation.
BODY is executed after the toggling and before running MODE-hook."
  (let* ((mode-name (symbol-name mode))
	 (hook (intern (concat mode-name "-hook")))
	 (hook-on (intern (concat mode-name "-on-hook")))
	 (hook-off (intern (concat mode-name "-off-hook")))
	 (toggle-doc (or doc
			 (format "With no argument, toggle %s.
With universal prefix ARG turn mode on.
With zero or negative ARG turn mode off.
\\{%s}" mode-name (concat mode-name "-map")))))
    `(progn
       (defcustom ,hook  nil
	 ,(format "Hook called at the end of function `%s'." mode-name)
	 :type 'hook)

       (defun ,mode (&optional arg)
	 ,toggle-doc
	 (interactive "P")
	 (setq ,mode
	       (if arg
		   (> (prefix-numeric-value arg) 0)
		 (not ,mode)))
	 ,@body
	 ;; The on/off hooks are here for backward compatibility.
	 (run-hooks ',hook (if ,mode ',hook-on ',hook-off))
	 ;; Return the new setting.
	 (if (interactive-p)
	     (message ,(format "%s %%sabled"
			       (replace-regexp-in-string
				"-Mode" " mode"
				(capitalize (symbol-name mode)) t))
		      (if ,mode "en" "dis")))
	 ,mode))))

;;;###autoload
(defalias 'easy-mmode-define-minor-mode 'define-minor-mode)
;;;###autoload
(defmacro define-minor-mode (mode doc &optional init-value lighter keymap &rest body)
  "Define a new minor mode MODE.
This function defines the associated control variable, keymap,
toggle command, and hooks (see `easy-mmode-define-toggle').

DOC is the documentation for the mode toggle command.
Optional INIT-VALUE is the initial value of the mode's variable.
  By default, the variable is made buffer-local.  This can be overridden
  by specifying an initial value of (global . INIT-VALUE).
Optional LIGHTER is displayed in the modeline when the mode is on.
Optional KEYMAP is the default (defvar) keymap bound to the mode keymap.
If it is a list, it is passed to `easy-mmode-define-keymap'
in order to build a valid keymap.
BODY contains code that will be executed each time the mode is (dis)activated.
It will be executed after any toggling but before running the hooks."
  (let* ((mode-name (symbol-name mode))
	 (globalp nil)
	 (keymap-sym (intern (concat mode-name "-map")))
	 (keymap-doc (format "Keymap for `%s'." mode-name)))
    ;; Check if the mode should be global.
    (when (and (consp init-value) (eq (car init-value) 'global))
      (setq init-value (cdr init-value) globalp t))

    `(progn
       ;; Define the variable to enable or disable the mode.
       ,(if globalp
	    `(defcustom ,mode ,init-value ,(format "Toggle %s.
Setting this variable directly does not take effect;
use either \\[customize] or the function `%s'." mode mode)
	       :set (lambda (symbol value) (funcall symbol (or value 0)))
	       :initialize 'custom-initialize-default
	       :type 'boolean)
	  `(progn
	     (defvar ,mode ,init-value ,(format "Non-nil if mode is enabled.
Use the function `%s' to change this variable." mode))
	     (make-variable-buffer-local ',mode)))

       ;; Define the minor-mode keymap.
       ,(when keymap
	  `(defvar ,keymap-sym
	     (cond ((and ,keymap (keymapp ,keymap))
		    ,keymap)
		   ((listp ,keymap)
		    (easy-mmode-define-keymap ,keymap))
		   (t (error "Invalid keymap %S" ,keymap)))
	     ,keymap-doc))

       ;; Define the toggle and the hooks.
       (easy-mmode-define-toggle ,mode ,doc ,@body)
       (add-minor-mode ',mode ,lighter
		       (if (boundp ',keymap-sym) (symbol-value ',keymap-sym)))
       
       ;; If the mode is global, call the function according to the default.
       ,(if globalp `(if ,mode (,mode 1))))))

;;;
;;; easy-mmode-defmap
;;;

(if (fboundp 'set-keymap-parents)
    (defalias 'easy-mmode-set-keymap-parents 'set-keymap-parents)
  (defun easy-mmode-set-keymap-parents (m parents)
    (set-keymap-parent
     m
     (cond
      ((not (consp parents)) parents)
      ((not (cdr parents)) (car parents))
      (t (let ((m (copy-keymap (pop parents))))
	   (easy-mmode-set-keymap-parents m parents)
	   m))))))

(defun easy-mmode-define-keymap (bs &optional name m args)
  "Return a keymap built from bindings BS.
BS must be a list of (KEY . BINDING) where
KEY and BINDINGS are suited as for define-key.
optional NAME is passed to `make-sparse-keymap'.
optional map M can be used to modify an existing map.
ARGS is a list of additional arguments."
  (let (inherit dense suppress)
    (while args
      (let ((key (pop args))
	    (val (pop args)))
	(cond
	 ((eq key :dense) (setq dense val))
	 ((eq key :inherit) (setq inherit val))
	 ((eq key :group) )
	 ;;((eq key :suppress) (setq suppress val))
	 (t (message "Unknown argument %s in defmap" key)))))
    (unless (keymapp m)
      (setq bs (append m bs))
      (setq m (if dense (make-keymap name) (make-sparse-keymap name))))
    (dolist (b bs)
      (let ((keys (car b))
	    (binding (cdr b)))
	(dolist (key (if (consp keys) keys (list keys)))
	  (cond
	   ((symbolp key)
	    (substitute-key-definition key binding m global-map))
	   ((null binding)
	    (unless (keymapp (lookup-key m key)) (define-key m key binding)))
	   ((let ((o (lookup-key m key)))
	      (or (null o) (numberp o) (eq o 'undefined)))
	    (define-key m key binding))))))
    (cond
     ((keymapp inherit) (set-keymap-parent m inherit))
     ((consp inherit) (easy-mmode-set-keymap-parents m inherit)))
    m))

;;;###autoload
(defmacro easy-mmode-defmap (m bs doc &rest args)
  `(progn
     (autoload 'easy-mmode-define-keymap "easy-mmode")
     (defconst ,m
       (easy-mmode-define-keymap ,bs nil (if (boundp ',m) ,m) ,(cons 'list args))
       ,doc)))


;;;
;;; easy-mmode-defsyntax
;;;

(defun easy-mmode-define-syntax (css args)
  (let ((st (make-syntax-table (cadr (memq :copy args)))))
    (dolist (cs css)
      (let ((char (car cs))
	    (syntax (cdr cs)))
	(if (sequencep char)
	    (mapcar (lambda (c) (modify-syntax-entry c syntax st)) char)
	  (modify-syntax-entry char syntax st))))
    st))

;;;###autoload
(defmacro easy-mmode-defsyntax (st css doc &rest args)
  `(progn
     (autoload 'easy-mmode-define-syntax "easy-mmode")
     (defconst ,st (easy-mmode-define-syntax ,css ,(cons 'list args)) doc)))



;;;
;;; A "macro-only" reimplementation of define-derived-mode.
;;;

;;;###autoload
(defmacro define-derived-mode (child parent name &optional docstring &rest body)
  "Create a new mode as a variant of an existing mode.

The arguments to this command are as follow:

CHILD:     the name of the command for the derived mode.
PARENT:    the name of the command for the parent mode (e.g. `text-mode').
NAME:      a string which will appear in the status line (e.g. \"Hypertext\")
DOCSTRING: an optional documentation string--if you do not supply one,
           the function will attempt to invent something useful.
BODY:      forms to execute just before running the
           hooks for the new mode.

Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:

  (define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\")

You could then make new key bindings for `LaTeX-thesis-mode-map'
without changing regular LaTeX mode.  In this example, BODY is empty,
and DOCSTRING is generated by default.

On a more complicated level, the following command uses `sgml-mode' as
the parent, and then sets the variable `case-fold-search' to nil:

  (define-derived-mode article-mode sgml-mode \"Article\"
    \"Major mode for editing technical articles.\"
    (setq case-fold-search nil))

Note that if the documentation string had been left out, it would have
been generated automatically, with a reference to the keymap."

  (let* ((child-name (symbol-name child))
	 (map (intern (concat child-name "-map")))
	 (syntax (intern (concat child-name "-syntax-table")))
	 (abbrev (intern (concat child-name "-abbrev-table")))
	 (hook (intern (concat child-name "-hook"))))
	 
    (when (and docstring (not (stringp docstring)))
      ;; DOCSTRING is really the first command and there's no docstring
      (push docstring body)
      (setq docstring nil))

    (unless (stringp docstring)
      ;; Use a default docstring.
      (setq docstring
	    (format "Major mode derived from `%s' by `define-derived-mode'.
Inherits all of the parent's attributes, but has its own keymap,
abbrev table and syntax table:

  `%s', `%s' and `%s'

which more-or-less shadow %s's corresponding tables."
		    parent map syntax abbrev parent)))

    (unless (string-match (regexp-quote (symbol-name hook)) docstring)
      ;; Make sure the docstring mentions the mode's hook
      (setq docstring
	    (concat docstring
		    (unless (eq parent 'fundamental-mode)
		      (concat
		       "\nAdditionally to any hooks its parent mode "
		       (if (string-match (regexp-quote (format "`%s'" parent))
					 docstring) nil
			 (format "`%s' " parent))
		       "might have run),"))
		    (format "\nThis mode runs `%s' just before exiting." hook))))

    (unless (string-match "\\\\[{[]" docstring)
      ;; And don't forget to put the mode's keymap
      (setq docstring (concat docstring "\n\\{" (symbol-name map) "}")))

    `(progn
       (defvar ,map (make-sparse-keymap))
       (defvar ,syntax (make-char-table 'syntax-table nil))
       (defvar ,abbrev (progn (define-abbrev-table ',abbrev nil) ,abbrev))
     
       (defun ,child ()
	 ,docstring
	 (interactive)
					; Run the parent.
	 (combine-run-hooks

	  (,parent)
					; Identify special modes.
	  (put ',child 'special (get ',parent 'special))
					; Identify the child mode.
	  (setq major-mode ',child)
	  (setq mode-name ,name)
					; Set up maps and tables.
	  (unless (keymap-parent ,map)
	    (set-keymap-parent ,map (current-local-map)))
	  (let ((parent (char-table-parent ,syntax)))
	    (unless (and parent (not (eq parent (standard-syntax-table))))
	      (set-char-table-parent ,syntax (syntax-table))))
	  (when local-abbrev-table
	    (mapatoms
	     (lambda (symbol)
	       (or (intern-soft (symbol-name symbol) ,abbrev)
		   (define-abbrev ,abbrev (symbol-name symbol)
		     (symbol-value symbol) (symbol-function symbol))))
	     local-abbrev-table))
       
	  (use-local-map ,map)
	  (set-syntax-table ,syntax)
	  (setq local-abbrev-table ,abbrev)
					; Splice in the body (if any).
	  ,@body)
					; Run the hooks, if any.
	 (run-hooks ',hook)))))


;;;
;;; easy-mmode-define-navigation
;;;

(defmacro easy-mmode-define-navigation (base re &optional name endfun)
  "Define BASE-next and BASE-prev to navigate in the buffer.
RE determines the places the commands should move point to.
NAME should describe the entities matched by RE and is used to build
  the docstrings of the two functions.
BASE-next also tries to make sure that the whole entry is visible by
  searching for its end (by calling ENDFUN if provided or by looking for
  the next entry) and recentering if necessary.
ENDFUN should return the end position (with or without moving point)."
  (let* ((base-name (symbol-name base))
	 (prev-sym (intern (concat base-name "-prev")))
	 (next-sym (intern (concat base-name "-next"))))
    (unless name (setq name (symbol-name base-name)))
    `(progn
       (defun ,next-sym (&optional count)
	 ,(format "Go to the next COUNT'th %s." name)
	 (interactive)
	 (unless count (setq count 1))
	 (if (< count 0) (,prev-sym (- count))
	   (if (looking-at ,re) (incf count))
	   (unless (re-search-forward ,re nil t count)
	     (error ,(format "No next %s" name)))
	   (goto-char (match-beginning 0))
	   (when (eq (current-buffer) (window-buffer (selected-window)))
	     (let ((endpt (or (save-excursion
				,(if endfun `(,endfun)
				   `(re-search-forward ,re nil t 2)))
			      (point-max))))
	       (unless (<= endpt (window-end)) (recenter))))))
       (defun ,prev-sym (&optional count)
	 ,(format "Go to the previous COUNT'th %s" (or name base-name))
	 (interactive)
	 (unless count (setq count 1))
	 (if (< count 0) (,next-sym (- count))
	   (unless (re-search-backward ,re nil t count)
	     (error ,(format "No previous %s" name))))))))

(provide 'easy-mmode)

;;; easy-mmode.el ends here