#| -*-Scheme-*-

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    2017, 2018, 2019 Massachusetts Institute of Technology

This file is part of MIT/GNU Scheme.

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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
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WITHOUT ANY WARRANTY; without even the implied warranty of
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General Public License for more details.

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|#

;;;; Pascal Mode

(declare (usual-integrations))

(define-command pascal-mode
  "Enter Pascal mode."
  ()
  (lambda ()
    (set-current-major-mode! (ref-mode-object pascal))))

(define-major-mode pascal fundamental "Pascal"
  "Major mode specialized for editing Pascal code.

\\{pascal}"
  (lambda (buffer)
    (local-set-variable! syntax-table pascal-mode:syntax-table buffer)
    (local-set-variable! syntax-ignore-comments-backwards #t buffer)
    (local-set-variable! indent-line-procedure
			 (ref-command pascal-indent-line)
			 buffer)
    (local-set-variable! comment-column 32 buffer)
    (local-set-variable! comment-locator-hook pascal-comment-locate buffer)
    (local-set-variable! comment-indent-hook pascal-comment-indentation buffer)
    (local-set-variable! comment-start "(* " buffer)
    (local-set-variable! comment-end " *)" buffer)
    (standard-alternate-paragraph-style! buffer)
    (local-set-variable! local-abbrev-table
			 (ref-variable pascal-mode-abbrev-table buffer)
			 buffer)
    (event-distributor/invoke! (ref-variable pascal-mode-hook buffer) buffer)))

(define pascal-mode:syntax-table (make-char-syntax-table))
(set-char-syntax! pascal-mode:syntax-table #\( "()1 ")
(set-char-syntax! pascal-mode:syntax-table #\) ")( 4")
(set-char-syntax! pascal-mode:syntax-table #\[ "(]  ")
(set-char-syntax! pascal-mode:syntax-table #\] ")[  ")
(set-char-syntax! pascal-mode:syntax-table #\{ "<   ")
(set-char-syntax! pascal-mode:syntax-table #\} ">   ")
(set-char-syntax! pascal-mode:syntax-table #\' "\"   ")
(set-char-syntax! pascal-mode:syntax-table #\$ "\"   ")
(set-char-syntax! pascal-mode:syntax-table #\* "_ 23")
(set-char-syntax! pascal-mode:syntax-table #\. "_   ")
(set-char-syntax! pascal-mode:syntax-table #\^ "_   ")
(set-char-syntax! pascal-mode:syntax-table #\@ "'   ")
(set-char-syntax! pascal-mode:syntax-table #\% "    ")
(set-char-syntax! pascal-mode:syntax-table #\" "    ")
(set-char-syntax! pascal-mode:syntax-table #\\ "    ")

(define (pascal-comment-locate mark)
  (if (re-search-forward "\\((\\*\\|{\\)[ \t]*" mark (line-end mark 0))
      (cons (re-match-start 0) (re-match-end 0))))

(define (pascal-comment-indentation mark)
  (let ((start (horizontal-space-start mark)))
    (if (line-start? start)
	(indentation-of-previous-non-blank-line mark)
	(max (1+ (mark-column start))
	     (ref-variable comment-column)))))

(define-key 'pascal #\c-\( 'pascal-shift-left)
(define-key 'pascal #\c-\) 'pascal-shift-right)
(define-key 'pascal #\rubout 'backward-delete-char-untabify)
(define-key 'pascal #\tab 'pascal-indent-line)

(define-command pascal-indent-line
  "Indents the current line for Pascal code."
  ()
  (lambda ()
    (let ((point (current-point)))
      (let ((indentation (calculate-pascal-indentation point)))
	(cond ((not (= indentation (current-indentation point)))
	       (change-indentation indentation point))
	      ((line-start? (horizontal-space-start point))
	       (set-current-point! (horizontal-space-end point))))))))

(define-command pascal-shift-right
  "Shift the current line right by Pascal Shift Increment.
With an argument, shifts right that many times."
  "p"
  (lambda (argument)
    (if (not (zero? argument))
	(let ((mark (line-start (current-point) 0)))
	  (change-indentation (+ (current-indentation mark)
				 (* argument
				    (ref-variable pascal-shift-increment)))
			      mark)))))

(define-command pascal-shift-left
  "Shift the current line left by Pascal Shift Increment.
With an argument, shifts left that many times."
  "p"
  (lambda (argument)
    (if (not (zero? argument))
	(let ((mark (line-start (current-point) 0)))
	  (change-indentation (- (current-indentation mark)
				 (* argument
				    (ref-variable pascal-shift-increment)))
			      mark)))))

(define (calculate-pascal-indentation mark)
  (let ((def-start
	  (let ((nb (find-previous-non-blank-line mark)))
	    (if (not nb)
		(group-start mark)
		(let ((start (backward-one-paragraph nb)))
		  (if (not start)
		      (group-start mark)
		      (line-start start 1)))))))
    (define (find-statement-start mark)
      (let ((start (find-previous-non-blank-line mark)))
	(cond ((not start) #f)
	      ((mark< start def-start) def-start)
	      (else
	       (let ((container
		      (parse-state-containing-sexp
		       (parse-partial-sexp def-start start))))
		 (if container
		     (find-statement-start start)
		     start))))))
    (let ((state (parse-partial-sexp def-start (line-start mark 0))))
      (let ((container (parse-state-containing-sexp state))
	    (last-sexp (parse-state-last-sexp state)))
	(if container
	    ;; Inside some parenthesized expression or arglist.
	    (if (mark> (line-end container 0) last-sexp)
		;; Indent first line under opening paren.
		(mark-column (horizontal-space-end (mark1+ container)))
		;; Indent subsequent line under previous line.
		(indentation-of-previous-non-blank-line mark))
	    (let ((start (find-statement-start mark)))
	      (if (not start)
		  0
		  (let ((start (horizontal-space-end start)))
		    (let ((indentation (mark-column start)))
		      (if (and (ref-variable pascal-indentation-keywords)
			       (re-match-forward
				(ref-variable pascal-indentation-keywords)
				start))
			  (+ indentation
			     (ref-variable pascal-shift-increment))
			  indentation))))))))))