;;; register.el --- register commands for Emacs.

;; Copyright (C) 1985, 1993, 1994 Free Software Foundation, Inc.

;; Maintainer: FSF
;; Keywords: internal

;; 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:

;; This package of functions emulates and somewhat extends the venerable
;; TECO's `register' feature, which permits you to save various useful
;; pieces of buffer state to named variables.  The entry points are
;; documented in the Emacs user's manual.

;;; Code:

(defvar register-alist nil
  "Alist of elements (NAME . CONTENTS), one for each Emacs register.
NAME is a character (a number).  CONTENTS is a string, number,
frame configuration, mark or list.
A list of strings represents a rectangle.
A list of the form (file . NAME) represents the file named NAME.
A list of the form (file-query NAME POSITION) represents position POSITION
 in the file named NAME, but query before visiting it.")

(defun get-register (reg)
  "Return contents of Emacs register named REG, or nil if none."
  (cdr (assq reg register-alist)))

(defun set-register (register value)
  "Set contents of Emacs register named REGISTER to VALUE.  Returns VALUE.
See the documentation of the variable `register-alist' for possible VALUE."
  (let ((aelt (assq register register-alist)))
    (if aelt
	(setcdr aelt value)
      (setq aelt (cons register value))
      (setq register-alist (cons aelt register-alist)))
    value))

(defun point-to-register (register &optional arg)
  "Store current location of point in register REGISTER.
With prefix argument, store current frame configuration.
Use \\[jump-to-register] to go to that location or restore that configuration.
Argument is a character, naming the register."
  (interactive "cPoint to register: \nP")
  (set-register register
		(if arg (current-frame-configuration) (point-marker))))

(defun window-configuration-to-register (register &optional arg)
  "Store the window configuration of the selected frame in register REGISTER.
Use \\[jump-to-register] to restore the configuration.
Argument is a character, naming the register."
  (interactive "cWindow configuration to register: \nP")
  (set-register register (current-window-configuration)))

(defun frame-configuration-to-register (register &optional arg)
  "Store the window configuration of all frames in register REGISTER.
Use \\[jump-to-register] to restore the configuration.
Argument is a character, naming the register."
  (interactive "cFrame configuration to register: \nP")
  (set-register register (current-frame-configuration)))

(defalias 'register-to-point 'jump-to-register)
(defun jump-to-register (register &optional delete)
  "Move point to location stored in a register.
If the register contains a file name, find that file.
 \(To put a file name in a register, you must use `set-register'.)
If the register contains a window configuration (one frame) or a frame
configuration (all frames), restore that frame or all frames accordingly.
First argument is a character, naming the register.
Optional second arg non-nil (interactively, prefix argument) says to
delete any existing frames that the frame configuration doesn't mention.
\(Otherwise, these frames are iconified.)"
  (interactive "cJump to register: \nP")
  (let ((val (get-register register)))
    (cond
     ((and (fboundp 'frame-configuration-p)
	   (frame-configuration-p val))
      (set-frame-configuration val (not delete)))
     ((window-configuration-p val)
      (set-window-configuration val))
     ((markerp val)
      (or (marker-buffer val)
	  (error "That register's buffer no longer exists"))
      (switch-to-buffer (marker-buffer val))
      (goto-char val))
     ((and (consp val) (eq (car val) 'file))
      (find-file (cdr val)))
     ((and (consp val) (eq (car val) 'file-query))
      (or (find-buffer-visiting (nth 1 val))
	  (y-or-n-p (format "Visit file %s again? " (nth 1 val)))
	  (error "Register access aborted"))
      (find-file (nth 1 val))
      (goto-char (nth 2 val)))
     (t
      (error "Register doesn't contain a buffer position or configuration")))))

;; Turn markers into file-query references when a buffer is killed.
(defun register-swap-out ()
  (and buffer-file-name
       (let ((tail register-alist))
	 (while tail
	   (and (markerp (cdr (car tail)))
		(eq (marker-buffer (cdr (car tail))) (current-buffer))
		(setcdr (car tail)
			(list 'file-query
			      buffer-file-name
			      (marker-position (cdr (car tail))))))
	   (setq tail (cdr tail))))))

(add-hook 'kill-buffer-hook 'register-swap-out)

;(defun number-to-register (arg char)
;  "Store a number in a register.
;Two args, NUMBER and REGISTER (a character, naming the register).
;If NUMBER is nil, digits in the buffer following point are read
;to get the number to store.
;Interactively, NUMBER is the prefix arg (none means nil)."
;  (interactive "P\ncNumber to register: ")
;  (set-register char 
;		(if arg
;		    (prefix-numeric-value arg)
;		  (if (looking-at "[0-9][0-9]*")
;		      (save-excursion
;		       (save-restriction
;			(narrow-to-region (point)
;					  (progn (skip-chars-forward "0-9")
;						 (point)))
;			(goto-char (point-min))
;			(read (current-buffer))))
;		    0))))

;(defun increment-register (arg char)
;  "Add NUMBER to the contents of register REGISTER.
;Interactively, NUMBER is the prefix arg (none means nil)." 
;  (interactive "p\ncNumber to register: ")
;  (or (integerp (get-register char))
;      (error "Register does not contain a number"))
;  (set-register char (+ arg (get-register char))))

(defun view-register (register)
  "Display what is contained in register named REGISTER.
The Lisp value REGISTER is a character."
  (interactive "cView register: ")
  (let ((val (get-register register)))
    (if (null val)
	(message "Register %s is empty" (single-key-description register))
      (with-output-to-temp-buffer "*Output*"
	(princ "Register ")
	(princ (single-key-description register))
	(princ " contains ")
	(cond
	 ((integerp val)
	  (princ val))

	 ((markerp val)
	  (let ((buf (marker-buffer val)))
	    (if (null buf)
		(princ "a marker in no buffer")
	      (princ "a buffer position:\nbuffer ")
	      (princ (buffer-name buf))
	      (princ ", position ")
	      (princ (marker-position val)))))

	 ((window-configuration-p val)
	  (princ "a window configuration."))

	 ((frame-configuration-p val)
	  (princ "a frame configuration."))

	 ((and (consp val) (eq (car val) 'file))
	  (princ "the file ")
	  (prin1 (cdr val))
	  (princ "."))

	 ((consp val)
	  (princ "the rectangle:\n")
	  (while val
	    (princ (car val))
	    (terpri)
	    (setq val (cdr val))))

	 ((stringp val)
	  (princ "the text:\n")
	  (princ val))

	 (t
	  (princ "Garbage:\n")
	  (prin1 val)))))))

(defun insert-register (register &optional arg)
  "Insert contents of register REGISTER.  (REGISTER is a character.)
Normally puts point before and mark after the inserted text.
If optional second arg is non-nil, puts mark before and point after.
Interactively, second arg is non-nil if prefix arg is supplied."
  (interactive "*cInsert register: \nP")
  (push-mark)
  (let ((val (get-register register)))
    (cond
     ((consp val)
      (insert-rectangle val))
     ((stringp val)
      (insert val))
     ((integerp val)
      (princ val (current-buffer)))
     ((and (markerp val) (marker-position val))
      (princ (marker-position val) (current-buffer)))
     (t
      (error "Register does not contain text"))))
  (if (not arg) (exchange-point-and-mark)))

(defun copy-to-register (register start end &optional delete-flag)
  "Copy region into register REGISTER.  With prefix arg, delete as well.
Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
START and END are buffer positions indicating what to copy."
  (interactive "cCopy to register: \nr\nP")
  (set-register register (buffer-substring start end))
  (if delete-flag (delete-region start end)))

(defun append-to-register (register start end &optional delete-flag)
  "Append region to text in register REGISTER.
With prefix arg, delete as well.
Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
START and END are buffer positions indicating what to append."
  (interactive "cAppend to register: \nr\nP")
  (or (stringp (get-register register))
      (error "Register does not contain text"))
  (set-register register (concat (get-register register)
			    (buffer-substring start end)))
  (if delete-flag (delete-region start end)))

(defun prepend-to-register (register start end &optional delete-flag)
  "Prepend region to text in register REGISTER.
With prefix arg, delete as well.
Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
START and END are buffer positions indicating what to prepend."
  (interactive "cPrepend to register: \nr\nP")
  (or (stringp (get-register register))
      (error "Register does not contain text"))
  (set-register register (concat (buffer-substring start end)
			    (get-register register)))
  (if delete-flag (delete-region start end)))

(defun copy-rectangle-to-register (register start end &optional delete-flag)
  "Copy rectangular region into register REGISTER.
With prefix arg, delete as well.
Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
START and END are buffer positions giving two corners of rectangle."
  (interactive "cCopy rectangle to register: \nr\nP")
  (set-register register
		(if delete-flag
		    (delete-extract-rectangle start end)
		  (extract-rectangle start end))))

;;; register.el ends here