#| -*-Scheme-*-

Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
    1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
    2017, 2018, 2019 Massachusetts Institute of Technology

This file is part of MIT/GNU Scheme.

MIT/GNU Scheme 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 of the License, or (at
your option) any later version.

MIT/GNU Scheme 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 MIT/GNU Scheme; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301,
USA.

|#

;;;; Group Operations

;;; These high-performance ops deal directly with groups and indices
;;; for speed and the least consing.  Since indices are not in general
;;; valid across modifications to the group, they can only be used in
;;; limited ways.  To save an index across a modification, it must be
;;; consed into a permanent mark.

(declare (usual-integrations string-allocate))

;;;; Extractions

(define (group-extract-string group start end)
  (let ((text (group-text group))
	(gap-start (group-gap-start group))
	(string (string-allocate (fix:- end start))))
    (cond ((fix:<= end gap-start)
	   (%substring-move! text start end string 0))
	  ((fix:>= start gap-start)
	   (%substring-move! text
			     (fix:+ start (group-gap-length group))
			     (fix:+ end (group-gap-length group))
			     string
			     0))
	  (else
	   (%substring-move! text start gap-start string 0)
	   (%substring-move! text
			     (group-gap-end group)
			     (fix:+ end (group-gap-length group))
			     string
			     (fix:- gap-start start))))
    string))

(define (group-copy-substring! group start end string start*)
  (let ((text (group-text group))
	(gap-start (group-gap-start group)))
    (cond ((fix:<= end gap-start)
	   (%substring-move! text start end string start*))
	  ((fix:>= start gap-start)
	   (%substring-move! text
			     (fix:+ start (group-gap-length group))
			     (fix:+ end (group-gap-length group))
			     string
			     start*))
	  (else
	   (%substring-move! text start gap-start string start*)
	   (%substring-move! text
			     (group-gap-end group)
			     (fix:+ end (group-gap-length group))
			     string
			     (fix:+ start* (fix:- gap-start start)))))))

(define (group-left-char group index)
  (string-ref (group-text group)
	      (fix:- (group-index->position-integrable group index #f) 1)))

(define (group-right-char group index)
  (string-ref (group-text group)
	      (group-index->position-integrable group index #t)))

(define (group-extract-and-delete-string! group start end)
  (let ((string (group-extract-string group start end)))
    (group-delete! group start end)
    string))

;;;; Insertion

(define (group-insert-char! group index char)
  (group-insert-chars! group index char 1))

(define (group-insert-chars! group index char n)
  (if (fix:< n 0)
      (error:bad-range-argument n 'GROUP-INSERT-CHARS!))
  (let ((interrupt-mask (set-interrupt-enables! interrupt-mask/gc-ok)))
    (prepare-gap-for-insert! group index n)
    (substring-fill! (group-text group) index (fix:+ index n) char)
    (finish-group-insert! group index n)
    (set-interrupt-enables! interrupt-mask)
    unspecific))

(define (group-insert-string! group index string)
  (group-insert-substring! group index string 0 (string-length string)))

(define (group-insert-substring! group index string start end)
  (let ((interrupt-mask (set-interrupt-enables! interrupt-mask/gc-ok)))
    (let ((n (fix:- end start)))
      (prepare-gap-for-insert! group index n)
      (%substring-move! string start end (group-text group) index)
      (finish-group-insert! group index n))
    (set-interrupt-enables! interrupt-mask)
    unspecific))

(define (prepare-gap-for-insert! group new-start n)
  (if (or (group-read-only? group)
	  (and (group-text-properties group)
	       (text-not-insertable? group new-start)))
      (barf-if-read-only))
  (if (not (group-modified? group)) (check-first-group-modification group))
  (cond ((fix:< (group-gap-length group) n)
	 (grow-group! group new-start n))
	((fix:< new-start (group-gap-start group))
	 (let ((new-end (fix:+ new-start (group-gap-length group))))
	   (%substring-move! (group-text group)
			     new-start
			     (group-gap-start group)
			     (group-text group)
			     new-end)
	   (set-group-gap-start! group new-start)
	   (set-group-gap-end! group new-end)))
	((fix:> new-start (group-gap-start group))
	 (let ((new-end (fix:+ new-start (group-gap-length group))))
	   (%substring-move! (group-text group)
			     (group-gap-end group)
			     new-end
			     (group-text group)
			     (group-gap-start group))
	   (set-group-gap-start! group new-start)
	   (set-group-gap-end! group new-end)))))

(define (finish-group-insert! group index n)
  (set-group-gap-start! group (fix:+ index n))
  (set-group-gap-length! group (fix:- (group-gap-length group) n))
  (if (group-start-changes-index group)
      (begin
	(if (fix:< index (group-start-changes-index group))
	    (set-group-start-changes-index! group index))
	(set-group-end-changes-index!
	 group
	 (if (fix:> index (group-end-changes-index group))
	     (fix:+ index n)
	     (fix:+ (group-end-changes-index group) n))))
      (begin
	(set-group-start-changes-index! group index)
	(set-group-end-changes-index! group (fix:+ index n))))
  (do ((marks (group-marks group) (system-pair-cdr marks)))
      ((null? marks))
    (if (and (system-pair-car marks)
	     (or (fix:> (mark-index (system-pair-car marks)) index)
		 (and (fix:= (mark-index (system-pair-car marks)) index)
		      (mark-left-inserting? (system-pair-car marks)))))
	(set-mark-index! (system-pair-car marks)
			 (fix:+ (mark-index (system-pair-car marks)) n))))
  (set-group-modified-tick! group (fix:+ (group-modified-tick group) 1))
  (undo-record-insertion! group index (fix:+ index n))
  ;; The MODIFIED? bit must be set *after* the undo recording.
  (set-group-modified?! group #t)
  (if (group-text-properties group)
      (update-intervals-for-insertion! group index n)))

;;;; Deletion

(define (group-delete-left-char! group index)
  (group-delete! group (fix:- index 1) index))

(define (group-delete-right-char! group index)
  (group-delete! group index (fix:+ index 1)))

(define (group-delete! group start end)
  (if (not (and (fix:>= end 0) (fix:<= end (group-length group))))
      (error:bad-range-argument end 'GROUP-DELETE!))
  (if (not (and (fix:>= start 0) (fix:<= start end)))
      (error:bad-range-argument start 'GROUP-DELETE!))
  (if (not (fix:= start end))
      (let ((interrupt-mask (set-interrupt-enables! interrupt-mask/gc-ok)))
	(let ((text (group-text group))
	      (gap-length (group-gap-length group)))
	  (if (or (group-read-only? group)
		  (and (group-text-properties group)
		       (text-not-deleteable? group start end)))
	      (barf-if-read-only))
	  (if (not (group-modified? group))
	      (check-first-group-modification group))
	  ;; Guarantee that the gap is between START and END.  This is
	  ;; best done before the undo recording.
	  (cond ((fix:< (group-gap-start group) start)
		 (%substring-move! text
				   (group-gap-end group)
				   (fix:+ start gap-length)
				   text
				   (group-gap-start group)))
		((fix:> (group-gap-start group) end)
		 (%substring-move! text
				   end
				   (group-gap-start group)
				   text
				   (fix:+ end gap-length))))
	  ;; The undo recording must occur *before* the deletion.
	  (undo-record-deletion! group start end)
	  (let ((gap-end (fix:+ end gap-length)))
	    (set-group-gap-start! group start)
	    (set-group-gap-end! group gap-end)
	    (set-group-gap-length! group (fix:- gap-end start))
	    (if (and (group-shrink-length group)
		     (fix:<= (fix:- (string-length text)
				    (fix:- gap-end start))
			     (group-shrink-length group)))
		(shrink-group! group))))
	(let ((n (fix:- end start)))
	  (if (group-start-changes-index group)
	      (begin
		(if (fix:< start (group-start-changes-index group))
		    (set-group-start-changes-index! group start))
		(set-group-end-changes-index!
		 group
		 (if (fix:>= end (group-end-changes-index group))
		     start
		     (fix:- (group-end-changes-index group) n))))
	      (begin
		(set-group-start-changes-index! group start)
		(set-group-end-changes-index! group start)))
	  (do ((marks (group-marks group) (system-pair-cdr marks)))
	      ((null? marks))
	    (cond ((or (not (system-pair-car marks))
		       (fix:<= (mark-index (system-pair-car marks)) start))
		   unspecific)
		  ((fix:<= (mark-index (system-pair-car marks)) end)
		   (set-mark-index! (system-pair-car marks) start))
		  (else
		   (set-mark-index!
		    (system-pair-car marks)
		    (fix:- (mark-index (system-pair-car marks)) n))))))
	(set-group-modified-tick! group (fix:+ (group-modified-tick group) 1))
	;; The MODIFIED? bit must be set *after* the undo recording.
	(set-group-modified?! group #t)
	(if (group-text-properties group)
	    (update-intervals-for-deletion! group start end))
	(set-interrupt-enables! interrupt-mask)
	unspecific)))

;;;; Replacement

(define (group-replace-char! group index char)
  (if (not (and (fix:>= index 0) (fix:< index (group-length group))))
      (error:bad-range-argument index 'GROUP-REPLACE-CHAR!))
  (let ((interrupt-mask (set-interrupt-enables! interrupt-mask/gc-ok))
	(end-index (fix:+ index 1)))
    (prepare-gap-for-replace! group index end-index)
    (string-set! (group-text group)
		 (group-index->position-integrable group index #t)
		 char)
    (finish-group-replace! group index end-index)
    (set-interrupt-enables! interrupt-mask)
    unspecific))

(define (group-replace-string! group index string)
  (group-replace-substring! group index string 0 (string-length string)))

(define (group-replace-substring! group index string start end)
  (if (fix:< start end)
      (let ((interrupt-mask (set-interrupt-enables! interrupt-mask/gc-ok))
	    (end-index (fix:+ index (fix:- end start))))
	(if (not (and (fix:>= index 0)
		      (fix:<= end-index (group-length group))))
	    (error:bad-range-argument index 'GROUP-REPLACE-SUBSTRING!))
	(prepare-gap-for-replace! group index end-index)
	(%substring-move! string start end
			  (group-text group)
			  (group-index->position-integrable group index #t))
	(finish-group-replace! group index end-index)
	(set-interrupt-enables! interrupt-mask)
	unspecific)))

(define (prepare-gap-for-replace! group start end)
  (if (or (group-read-only? group)
	  (and (group-text-properties group)
	       (text-not-replaceable? group start end)))
      (barf-if-read-only))
  (if (not (group-modified? group))
      (check-first-group-modification group))
  (if (and (fix:< start (group-gap-start group))
	   (fix:< (group-gap-start group) end))
      (let ((new-end (fix:+ end (group-gap-length group))))
	(%substring-move! (group-text group)
			  (group-gap-end group)
			  new-end
			  (group-text group)
			  (group-gap-start group))
	(set-group-gap-start! group end)
	(set-group-gap-end! group new-end)))
  (undo-record-replacement! group start end))

(define (finish-group-replace! group start end)
  (if (group-start-changes-index group)
      (begin
	(if (fix:< start (group-start-changes-index group))
	    (set-group-start-changes-index! group start))
	(if (fix:> end (group-end-changes-index group))
	    (set-group-end-changes-index! group end)))
      (begin
	(set-group-start-changes-index! group start)
	(set-group-end-changes-index! group end)))
  (set-group-modified-tick! group (fix:+ (group-modified-tick group) 1))
  ;; The MODIFIED? bit must be set *after* the undo recording.
  (set-group-modified?! group #t)
  (if (group-text-properties group)
      (update-intervals-for-replacement! group start end)))

;;;; Resizing

(define (grow-group! group new-gap-start n)
  (let ((text (group-text group))
	(gap-start (group-gap-start group))
	(gap-end (group-gap-end group))
	(realloc-factor (group-reallocation-factor group)))
    (let ((text-length (string-length text))
	  (gap-delta (- new-gap-start gap-start)))
      (let ((n-chars (- text-length (group-gap-length group))))
	(let ((new-text-length
	       (let ((minimum-text-length (+ n-chars n)))
		 (let loop ((length (if (= text-length 0) 1 text-length)))
		   (let ((length (ceiling (* length realloc-factor))))
		     (if (< length minimum-text-length)
			 (loop length)
			 length))))))
	  (let ((new-text (allocate-buffer-storage new-text-length))
		(new-gap-length (- new-text-length n-chars)))
	    (let ((new-gap-end (+ new-gap-start new-gap-length)))
	      (cond ((= gap-delta 0)
		     (%substring-move! text 0 gap-start new-text 0)
		     (%substring-move! text gap-end text-length
				       new-text new-gap-end))
		    ((< gap-delta 0)
		     (%substring-move! text 0 new-gap-start new-text 0)
		     (%substring-move! text new-gap-start gap-start
				       new-text new-gap-end)
		     (%substring-move! text gap-end text-length
				       new-text (- new-gap-end gap-delta)))
		    (else
		     (let ((ngsp (+ gap-end gap-delta)))
		       (%substring-move! text 0 gap-start new-text 0)
		       (%substring-move! text gap-end ngsp new-text gap-start)
		       (%substring-move! text ngsp text-length
					 new-text new-gap-end))))
	      (set-group-text! group new-text)
	      (set-group-gap-start! group new-gap-start)
	      (set-group-gap-end! group new-gap-end)
	      (set-group-gap-length! group new-gap-length))))))
    (memoize-shrink-length! group realloc-factor)))

(define (shrink-group! group)
  (let ((text (group-text group))
	(gap-start (group-gap-start group))
	(gap-length (group-gap-length group))
	(realloc-factor (group-reallocation-factor group)))
    (let ((text-length (string-length text)))
      (let ((n-chars (- text-length gap-length)))
	(let ((new-text-length
	       (if (= n-chars 0)
		   0
		   (let loop ((length text-length))
		     (let ((length (floor (/ length realloc-factor))))
		       (let ((sl
			      (compute-shrink-length length realloc-factor)))
			 (if (< sl n-chars)
			     length
			     (loop length)))))))
	      (gap-end (group-gap-end group)))
	  (let ((new-text (allocate-buffer-storage new-text-length))
		(delta (- text-length new-text-length)))
	    (let ((new-gap-end (- gap-end delta)))
	      (%substring-move! text 0 gap-start new-text 0)
	      (%substring-move! text gap-end text-length new-text new-gap-end)
	      (set-group-gap-end! group new-gap-end)
	      (set-group-gap-length! group (- gap-length delta)))
	    (set-group-text! group new-text)))))
    (memoize-shrink-length! group realloc-factor)))

(define (memoize-shrink-length! group realloc-factor)
  (set-group-shrink-length!
   group
   (compute-shrink-length (string-length (group-text group)) realloc-factor)))

(define (compute-shrink-length length realloc-factor)
  (floor (/ (floor (/ length realloc-factor)) realloc-factor)))

(define (group-reallocation-factor group)
  ;; We assume the result satisfies (LAMBDA (G) (AND (REAL? G) (> G 1)))
  (inexact->exact (ref-variable buffer-reallocation-factor group)))