;;; reftex-parse.el --- parser functions for RefTeX  -*- lexical-binding: t; -*-

;; Copyright (C) 1997-2022 Free Software Foundation, Inc.

;; Author: Carsten Dominik <dominik@science.uva.nl>
;; Maintainer: auctex-devel@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 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 <https://www.gnu.org/licenses/>.

;;; Commentary:

;;; Code:

(eval-when-compile (require 'cl-lib))

(require 'reftex)

(defmacro reftex-with-special-syntax (&rest body)
  `(let ((saved-syntax (syntax-table)))
     (unwind-protect
         (progn
           (set-syntax-table reftex-syntax-table)
           (let ((case-fold-search nil))
             ,@body))
       (set-syntax-table saved-syntax))))

;;;###autoload
(defun reftex-parse-one ()
  "Re-parse this file."
  (interactive)
  (let ((reftex-enable-partial-scans t))
    (reftex-access-scan-info '(4))))

;;;###autoload
(defun reftex-parse-all ()
  "Re-parse entire document."
  (interactive)
  (reftex-access-scan-info '(16)))

(defvar reftex--index-tags)

;;;###autoload
(defun reftex-do-parse (rescan &optional file)
  "Do a document rescan.
When allowed, do only a partial scan from FILE."

  ;; Normalize the rescan argument
  (setq rescan (cond ((eq rescan t) t)
                     ((eq rescan 1) 1)
                     ((equal rescan '(4)) t)
                     ((equal rescan '(16)) 1)
                     (t 1)))

  ;; Partial scans only when allowed
  (unless reftex-enable-partial-scans
    (setq rescan 1))

  ;; Do the scanning.

  (let* ((old-list (symbol-value reftex-docstruct-symbol))
         (master (reftex-TeX-master-file))
         (true-master (file-truename master))
         (master-dir (file-name-as-directory (file-name-directory master)))
         (file (or file (buffer-file-name)))
         (true-file (file-truename file))
         (bibview-cache (assq 'bibview-cache old-list))
         (reftex--index-tags (cdr (assq 'index-tags old-list)))
         from-file appendix docstruct tmp)

    ;; Make sure replacement is really an option here
    (when (and (eq rescan t)
               (not (and (member (list 'bof file) old-list)
                         (member (list 'eof file) old-list))))
      ;; Scan whole document because no such file section exists
      (setq rescan 1))
    (when (string= true-file true-master)
      ;; Scan whole document because this file is the master
      (setq rescan 1))

    ;; From which file do we start?
    (setq from-file
          (cond ((eq rescan t) (or file master))
                ((eq rescan 1) master)
                (t (error "This should not happen (reftex-do-parse)"))))

    ;; Reset index-tags if we scan everything
    (if (equal rescan 1) (setq reftex--index-tags nil))

    ;; Find active toc entry and initialize section-numbers
    (setq reftex-active-toc (reftex-last-assoc-before-elt
                             'toc (list 'bof from-file) old-list)
          appendix (reftex-last-assoc-before-elt
                    'appendix (list 'bof from-file) old-list))

    (reftex-init-section-numbers reftex-active-toc appendix)

    (if (eq rescan 1)
        (message "Scanning entire document...")
      (message "Scanning document from %s..." from-file))

    (reftex-with-special-syntax
     (save-window-excursion
       (save-excursion
         (unwind-protect
             (setq docstruct
                   (reftex-parse-from-file
                    from-file docstruct master-dir))
           (reftex-kill-temporary-buffers)))))

    (message "Scanning document... done")

    ;; Turn the list around.
    (setq docstruct (nreverse docstruct))

    ;; Set or insert
    (setq docstruct (reftex-replace-label-list-segment
                     old-list docstruct (eq rescan 1)))

    ;; Add all missing information
    (unless (assq 'label-numbers docstruct)
      (push (cons 'label-numbers nil) docstruct))
    (unless (assq 'master-dir docstruct)
      (push (cons 'master-dir master-dir) docstruct))
    (unless (assq 'bibview-cache docstruct)
      (push (cons 'bibview-cache (cdr bibview-cache)) docstruct))
    (let* ((bof1 (memq (assq 'bof docstruct) docstruct))
           (bof2 (assq 'bof (cdr bof1)))
           (is-multi (not (not (and bof1 bof2))))
           (entry (or (assq 'is-multi docstruct)
                      (car (push (list 'is-multi is-multi) docstruct)))))
      (setcdr entry (cons is-multi nil)))
    (and reftex--index-tags
         (setq reftex--index-tags (sort reftex--index-tags #'string<)))
    (let ((index-tag-cell (assq 'index-tags docstruct)))
      (if index-tag-cell
          (setcdr index-tag-cell reftex--index-tags)
        (push (cons 'index-tags reftex--index-tags) docstruct)))
    (unless (assq 'xr docstruct)
      (let* ((allxr (reftex-all-assq 'xr-doc docstruct))
             (alist (mapcar
                     (lambda (x)
                       (if (setq tmp (reftex-locate-file (nth 2 x) "tex"
                                                         master-dir))
                           (cons (nth 1 x) tmp)
                         (message "Can't find external document %s"
                                  (nth 2 x))
                         nil))
                     allxr))
             (alist (delq nil alist))
             (allprefix (delq nil (mapcar #'car alist)))
             (regexp (if allprefix
                         (concat "\\`\\("
                                 (mapconcat #'identity allprefix "\\|")
                                 "\\)")
                       "\\\\\\\\\\\\")))   ; this will never match
        (push (list 'xr alist regexp) docstruct)))

    (set reftex-docstruct-symbol docstruct)
    (put reftex-docstruct-symbol 'modified t)))

;;;###autoload
(defun reftex-everything-regexp ()
  (if reftex-support-index
      reftex-everything-regexp
    reftex-everything-regexp-no-index))

;; NB this is a global autoload - see reftex.el.
;;;###autoload
(defun reftex-all-document-files (&optional relative)
  "Return a list of all files belonging to the current document.
When RELATIVE is non-nil, give file names relative to directory
of master file."
  (let* ((all (symbol-value reftex-docstruct-symbol))
         (master-dir (file-name-directory (reftex-TeX-master-file)))
         (re (concat "\\`" (regexp-quote master-dir)))
        file-list tmp file)
    (while (setq tmp (assoc 'bof all))
      (setq file (nth 1 tmp)
            all (cdr (memq tmp all)))
      (and relative
           (string-match re file)
           (setq file (substring file (match-end 0))))
      (push file file-list))
    (nreverse file-list)))

;; Bound in the caller, reftex-do-parse.
(defun reftex-parse-from-file (file docstruct master-dir)
  "Scan the buffer for labels and save them in a list."
  (let ((regexp (reftex-everything-regexp))
        (bound 0)
        file-found tmp include-file
        (level 1)
        (highest-level 100)
        toc-entry index-entry next-buf buf)

    (catch 'exit
      (setq file-found (reftex-locate-file file "tex" master-dir))
      (if (and (not file-found)
               (setq buf (find-buffer-visiting file)))
          (setq file-found (buffer-file-name buf)))

      (unless file-found
        (push (list 'file-error file) docstruct)
        (throw 'exit nil))

      (save-excursion

        (message "Scanning file %s" file)
        (set-buffer
         (setq next-buf
               (reftex-get-file-buffer-force
                file-found
                (not (eq t reftex-keep-temporary-buffers)))))

        ;; Begin of file mark
        (setq file (buffer-file-name))
        (push (list 'bof file) docstruct)

        (reftex-with-special-syntax
         (save-excursion
           (save-restriction
             (widen)
             (goto-char 1)

             (while (re-search-forward regexp nil t)

               (cond

                ((match-end 1)
                 ;; It is a label
		 (when (or (null reftex-label-ignored-macros-and-environments)
			   ;; \label{} defs should always be honored,
			   ;; just no keyval style [label=foo] defs.
			   (string-equal "\\label{" (substring (reftex-match-string 0) 0 7))
                           (if (and (fboundp 'TeX-current-macro)
                                    (fboundp 'LaTeX-current-environment))
                               (not (or (member (save-match-data (TeX-current-macro))
                                                reftex-label-ignored-macros-and-environments)
                                        (member (save-match-data (LaTeX-current-environment))
                                                reftex-label-ignored-macros-and-environments)))
                             t))
		   (push (reftex-label-info (reftex-match-string 1) file bound)
			 docstruct)))

                ((match-end 3)
                 ;; It is a section

		 ;; Use the beginning as bound and not the end
		 ;; (i.e. (point)) because the section command might
		 ;; be the start of the current environment to be
		 ;; found by `reftex-label-info'.
                 (setq bound (match-beginning 0))
		 ;; The section regexp matches a character at the end
		 ;; we are not interested in.  Especially if it is the
		 ;; backslash of a following macro we want to find in
		 ;; the next parsing iteration.
		 (when (eq (char-before) ?\\) (backward-char))
                 ;; Insert in List
                 (setq toc-entry (funcall reftex-section-info-function file))
                 (when (and toc-entry
                            (eq ;; Either both are t or both are nil.
                             (= (char-after bound) ?%)
                             (string-suffix-p ".dtx" file)))
                   ;; It can happen that section info returns nil
                   (setq level (nth 5 toc-entry))
                   (setq highest-level (min highest-level level))
                   (if (= level highest-level)
                       (message
                        "Scanning %s %s ..."
                        (car (rassoc level reftex-section-levels-all))
                        (nth 6 toc-entry)))

                   (push toc-entry docstruct)
                   (setq reftex-active-toc toc-entry)))

                ((match-end 7)
                 ;; It's an include or input
                 (setq include-file (reftex-match-string 7))
                 ;; Test if this file should be ignored
                 (unless (delq nil (mapcar
                                    (lambda (x) (string-match x include-file))
                                    reftex-no-include-regexps))
                   ;; Parse it
                   (setq docstruct
                         (reftex-parse-from-file
                          include-file
                          docstruct master-dir))))

                ((match-end 9)
                 ;; Appendix starts here
                 (reftex-init-section-numbers nil t)
                 (push (cons 'appendix t) docstruct))

                ((match-end 10)
                 ;; Index entry
                 (when reftex-support-index
                   (setq index-entry (reftex-index-info file))
                   (when index-entry
                     (cl-pushnew (nth 1 index-entry) reftex--index-tags :test #'equal)
                     (push index-entry docstruct))))

                ((match-end 11)
                 ;; A macro with label
                 (save-excursion
                   (let* ((mac (reftex-match-string 11))
                          (label (progn (goto-char (match-end 11))
                                        (save-match-data
                                          (reftex-no-props
                                           (reftex-nth-arg-wrapper
                                            mac)))))
                          (typekey (nth 1 (assoc mac reftex-env-or-mac-alist)))
                          (entry (progn (if typekey
                                            ;; A typing macro
                                            (goto-char (match-end 0))
                                          ;; A neutral macro
                                          (goto-char (match-end 11))
                                          (reftex-move-over-touching-args))
                                        (reftex-label-info
                                         label file bound nil nil))))
                     (push entry docstruct))))
                (t (error "This should not happen (reftex-parse-from-file)")))
               )

             ;; Find bibliography statement
             (when (setq tmp (reftex-locate-bibliography-files master-dir))
               (push (cons 'bib tmp) docstruct))

             (goto-char 1)
             (when (re-search-forward
                    "\\(\\`\\|[\n\r]\\)[ \t]*\\\\begin{thebibliography}" nil t)
               (push (cons 'thebib file) docstruct))

             ;; Find external document specifications
             (goto-char 1)
             (while (re-search-forward "[\n\r][ \t]*\\\\externaldocument\\(\\[\\([^]]*\\)\\]\\)?{\\([^}]+\\)}" nil t)
               (push (list 'xr-doc (reftex-match-string 2)
                           (reftex-match-string 3))
                     docstruct))

             ;; End of file mark
             (push (list 'eof file) docstruct)))))

      ;; Kill the scanned buffer
      (reftex-kill-temporary-buffers next-buf))

    ;; Return the list
    docstruct))

(defun reftex-using-biblatex-p ()
  "Return non-nil if we are using biblatex rather than bibtex."
  (if (boundp 'TeX-active-styles)
      ;; the sophisticated AUCTeX way
      (member "biblatex" TeX-active-styles)
    ;; poor-man's check...
    (save-excursion
      (re-search-forward "^[^%\n]*?\\\\usepackage.*{biblatex}" nil t))))

;;;###autoload
(defun reftex-locate-bibliography-files (master-dir &optional files)
  "Scan buffer for bibliography macros and return file list."
  (unless files
    (save-excursion
      (goto-char (point-min))
      ;; when biblatex is used, multiple \bibliography or
      ;; \addbibresource macros are allowed.  With plain bibtex, only
      ;; the first is used.
      (let ((using-biblatex (reftex-using-biblatex-p))
	    (again t))
	(while (and again
		    (re-search-forward
		     (concat
		      ;;           "\\(\\`\\|[\n\r]\\)[^%]*\\\\\\("
		      "\\(^\\)[^%\n\r]*\\\\\\("
		      (mapconcat #'identity reftex-bibliography-commands "\\|")
		      "\\)\\(\\[.+?\\]\\)?{[ \t]*\\([^}]+\\)")
		     nil t))
	  (setq files
		(append files
			(split-string (reftex-match-string 4)
				      "[ \t\n\r]*,[ \t\n\r]*")))
	  (unless using-biblatex
	    (setq again nil))))))
  (when files
    (setq files
          (mapcar
           (lambda (x)
             (if (or (member x reftex-bibfile-ignore-list)
                     (delq nil (mapcar (lambda (re) (string-match re x))
                                       reftex-bibfile-ignore-regexps)))
                 ;; excluded file
                 nil
               ;; find the file
               (reftex-locate-file x "bib" master-dir)))
           files))
    (delq nil files)))

(defun reftex-replace-label-list-segment (old insert &optional entirely)
  "Replace the segment in OLD which corresponds to INSERT.
Works with side effects, directly changes old.
If ENTIRELY is t, just return INSERT.
This function also makes sure the old toc markers do not point anywhere."

  (cond
   (entirely
    (reftex-silence-toc-markers old (length old))
    insert)
   (t (let* ((new old)
             (file (nth 1 (car insert)))
             (eof-list (member (list 'eof file) old))
             (bof-list (member (list 'bof file) old))
             n)
        (if (not (and bof-list eof-list))
            (error "Cannot splice")
          ;; Splice
          (reftex-silence-toc-markers bof-list (- (length bof-list)
                                                  (length eof-list)))
          (setq n (- (length old) (length bof-list)))
          (setcdr (nthcdr n new) (cdr insert))
          (setcdr (nthcdr (1- (length new)) new) (cdr eof-list)))
        new))))

;;;###autoload
(defun reftex-section-info (file)
  "Return a section entry for the current match.
Careful: This function expects the `match-data' to still be in
place!"
  (let* ((marker (set-marker (make-marker) (1- (match-beginning 3))))
         (macro (reftex-match-string 3))
         (prefix (save-match-data
                   (if (string-match "begin{\\([^}]+\\)}" macro)
                       (match-string 1 macro))))
         (level-exp (cdr (assoc macro reftex-section-levels-all)))
         (level (if (symbolp level-exp)
                    (save-match-data (funcall level-exp))
                  level-exp))
         (star (= ?* (char-after (match-end 3))))
         (unnumbered (or star (< level 0)))
         (level (abs level))
         (section-number (reftex-section-number level unnumbered))
         (text1 (save-match-data
                  (save-excursion
                    (reftex-context-substring prefix))))
         (literal (buffer-substring-no-properties
                   (1- (match-beginning 3))
                   (min (point-max) (+ (match-end 0) (length text1) 1))))
         ;; Literal can be too short since text1 too short. No big problem.
         (text (reftex-nicify-text text1)))

    ;; Add section number and indentation
    (setq text
          (concat
           (make-string (* reftex-level-indent level) ?\ )
           (if (nth 1 reftex-label-menu-flags) ; section number flag
               (concat section-number " "))
           (if prefix (concat (capitalize prefix) ": ") "")
           text))
    (list 'toc "toc" text file marker level section-number
          literal (marker-position marker))))

;;;###autoload
(defun reftex-ensure-index-support (&optional abort)
  "When index support is turned off, ask to turn it on and
set the current prefix argument so that `reftex-access-scan-info'
will rescan the entire document."
  (cond
   (reftex-support-index t)
   ((y-or-n-p "Turn on index support and rescan entire document? ")
    (setq reftex-support-index 'demanded
          current-prefix-arg '(16)))
   (t (if abort
          (error "No index support")
        (message "No index support")
        (ding)
        (sit-for 1)))))

;;;###autoload
(defun reftex-index-info-safe (file)
  (reftex-with-special-syntax
   (reftex-index-info file)))

(defvar test-dummy)
;;;###autoload
(defun reftex-index-info (file)
  "Return an index entry for the current match.
Careful: This function expects the `match-data' to still be in
place!"
  (catch 'exit
    (let* ((macro (reftex-match-string 10))
           (bom (match-beginning 10))
           (boa (match-end 10))
           (entry (or (assoc macro reftex-index-macro-alist)
                      (throw 'exit nil)))
           (exclude (nth 3 entry))
           ;; The following is a test if this match should be excluded
           (test-dummy (and (fboundp exclude)
                            (funcall exclude)
                            (throw 'exit nil)))
           (itag (nth 1 entry))
           (prefix (nth 2 entry))
           (index-tag
            (cond ((stringp itag) itag)
                  ((integerp itag)
                   (progn (goto-char boa)
                          (or (reftex-nth-arg itag (nth 6 entry)) "idx")))
                  (t "idx")))
           (arg (or (progn (goto-char boa)
                           (reftex-nth-arg (nth 5 entry) (nth 6 entry)))
                    ""))
           (end-of-args (progn (goto-char boa)
                               (reftex-move-over-touching-args)
                               (point)))
           (end-of-context (progn (skip-chars-forward "^ \t\n\r") (point)))
           (begin-of-context
            (progn (goto-char bom)
                   (skip-chars-backward "^ \t\r\n")
                   (point)))
           (context (buffer-substring-no-properties
                     begin-of-context end-of-context))
           (key-end (if (string-match reftex-index-key-end-re arg)
                        (1+ (match-beginning 0))))
           (rawkey (substring arg 0 key-end))

           (key (if prefix (concat prefix rawkey) rawkey))
           (sortkey (downcase key))
           (showkey (mapconcat #'identity
                               (split-string key reftex-index-level-re)
                               " ! ")))
      (goto-char end-of-args)
      ;;       0        1       2      3   4   5  6      7       8      9
      (list 'index index-tag context file bom arg key showkey sortkey key-end))))

;;;###autoload
(defun reftex-short-context (env parse &optional bound derive)
  "Get about one line of useful context for the label definition at point."

  (if (consp parse)
      (setq parse (if derive (cdr parse) (car parse))))

  (reftex-nicify-text

   (cond

    ((null parse)
     (save-excursion
       (reftex-context-substring)))

    ((eq parse t)
     (if (string= env "section")
         ;; special treatment for section labels
         (save-excursion
           (if (and (re-search-backward reftex-section-or-include-regexp
                                        (point-min) t)
                    (match-end 2))
               (progn
                 (goto-char (match-end 0))
                 (reftex-context-substring))
             (if reftex-active-toc
                 (progn
                   (string-match "{\\([^}]*\\)" (nth 7 reftex-active-toc))
                   (match-string 1 (nth 7 reftex-active-toc)))
               "SECTION HEADING NOT FOUND")))
       (save-excursion
         (goto-char reftex-default-context-position)
         (unless (eq (string-to-char env) ?\\)
           (reftex-move-over-touching-args))
         (reftex-context-substring))))

    ((stringp parse)
     (save-excursion
       (if (re-search-backward parse bound t)
           (progn
             (goto-char (match-end 0))
             (reftex-context-substring))
         "NO MATCH FOR CONTEXT REGEXP")))

    ((integerp parse)
     (or (save-excursion
           (goto-char reftex-default-context-position)
           (reftex-nth-arg
            parse
            (nth 6 (assoc env reftex-env-or-mac-alist))))
         ""))

    ((fboundp parse)
     ;; A hook function.  Call it.
     (save-excursion
       (condition-case error-var
           (funcall parse env)
         (error (format "HOOK ERROR: %s" (cdr error-var))))))
    (t
     "INVALID VALUE OF PARSE"))))

;;;###autoload
(defun reftex-where-am-I ()
  "Return the docstruct entry above point.
Actually returns a cons cell in which the cdr is a flag indicating
if the information is exact (t) or approximate (nil)."

  (let ((docstruct (symbol-value reftex-docstruct-symbol))
        (cnt 0) rtn rtn-if-no-other
        found)
    (save-excursion
      (while (not rtn)
        (cl-incf cnt)
        (setq found (re-search-backward (reftex-everything-regexp) nil t))
        (setq rtn
              (cond
               ((not found)
                ;; no match
                (or
                 (car (member (list 'bof (buffer-file-name)) docstruct))
                 (not (setq cnt 2))
                 (assq 'bof docstruct)  ;; for safety reasons
                 'corrupted))
               ((match-end 1)
                ;; Label
                (assoc (reftex-match-string 1)
                       (symbol-value reftex-docstruct-symbol)))
               ((match-end 3)
                ;; Section
                (goto-char (1- (match-beginning 3)))
                (let* ((list (member (list 'bof (buffer-file-name))
                                     docstruct))
                       (endelt (car (member (list 'eof (buffer-file-name))
                                            list)))
                       rtn1)
                  (while (and list (not (eq endelt (car list))))
                    (if (and (eq (car (car list)) 'toc)
                             (string= (buffer-file-name)
                                      (nth 3 (car list))))
                        (cond
                         ((equal (point)
                                 (or (and (markerp (nth 4 (car list)))
                                          (marker-position (nth 4 (car list))))
                                     (nth 8 (car list))))
                          ;; Fits with marker position or recorded position
                          (setq rtn1 (car list) list nil))
                         ((looking-at (reftex-make-regexp-allow-for-ctrl-m
                                       (nth 7 (car list))))
                          ;; Same title: remember, but keep looking
                          (setq rtn-if-no-other (car list)))))
                    (pop list))
                  rtn1))
               ((match-end 7)
                ;; Input or include...
                (car
                 (member (list 'eof (reftex-locate-file
                                     (reftex-match-string 7) "tex"
                                     (cdr (assq 'master-dir docstruct))))
                         docstruct)))
               ((match-end 9)
                (assq 'appendix (symbol-value reftex-docstruct-symbol)))
               ((match-end 10)
                ;; Index entry
                (when reftex-support-index
                  (let* ((index-info (save-excursion
                                       (reftex-index-info-safe nil)))
                         (list (member (list 'bof (buffer-file-name))
                                       docstruct))
                         (endelt (car (member (list 'eof (buffer-file-name))
                                              list)))
                         dist last-dist last (n 0))
                    ;; Check all index entries with equal text
                    (while (and list (not (eq endelt (car list))))
                      (when (and (eq (car (car list)) 'index)
                                 (string= (nth 2 index-info)
                                          (nth 2 (car list))))
                        (cl-incf n)
                        (setq dist (abs (- (point) (nth 4 (car list)))))
                        (if (or (not last-dist) (< dist last-dist))
                            (setq last-dist dist last (car list))))
                      (setq list (cdr list)))
                    ;; We are sure if we have only one, or a zero distance
                    (cond ((or (= n 1) (equal dist 0)) last)
                          ((> n 1) (setq cnt 2) last)
                          (t nil)))))
               ((match-end 11)
                (save-excursion
                  (goto-char (match-end 11))
                  (assoc (reftex-no-props
                          (reftex-nth-arg-wrapper
                           (reftex-match-string 11)))
                         (symbol-value reftex-docstruct-symbol))))
               (t
                (error "This should not happen (reftex-where-am-I)"))))))
    ;; Check if there was only a by-name match for the section.
    (when (and (not rtn) rtn-if-no-other)
      (setq rtn rtn-if-no-other
            cnt 2))
    (cons rtn (eq cnt 1))))

;;;###autoload
(defun reftex-notice-new (&optional n force)
  "Hook to handshake with RefTeX after something new has been inserted."
  ;; Add a new entry to the docstruct list.  If it is a section, renumber
  ;; the following sections.
  ;; FIXME:  Put in a WHAT parameter and search backward until one is found.
  ;; When N is given, go back that many matches of reftex-everything-regexp
  ;; When FORCE is non-nil, also insert if `reftex-where-am-I' was uncertain.
  (condition-case nil
      (catch 'exit
        (unless reftex-mode (throw 'exit nil))
        (reftex-access-scan-info)
        (let* ((docstruct (symbol-value reftex-docstruct-symbol))
               here-I-am appendix tail entry star level
               section-number context)

     (save-excursion
       (when (re-search-backward (reftex-everything-regexp) nil t (or n 1))

         ;; Find where we are
         (setq here-I-am (reftex-where-am-I))
         (or here-I-am (throw 'exit nil))
         (unless (or force (cdr here-I-am)) (throw 'exit nil))
         (setq tail (memq (car here-I-am) docstruct))
         (or tail (throw 'exit nil))
         (setq reftex-active-toc (reftex-last-assoc-before-elt
                                  'toc (car here-I-am) docstruct)
               appendix (reftex-last-assoc-before-elt
                         'appendix (car here-I-am) docstruct))

         ;; Initialize section numbers
         (if (eq (car (car here-I-am)) 'appendix)
             (reftex-init-section-numbers nil t)
           (reftex-init-section-numbers reftex-active-toc appendix))

         ;; Match the section command
         (when (re-search-forward (reftex-everything-regexp) nil t)
           (cond
            ((match-end 1)
             (push (reftex-label-info (reftex-match-string 1) buffer-file-name)
                   (cdr tail)))

            ((match-end 3)
             (setq star (= ?* (char-after (match-end 3)))
                   entry (reftex-section-info (buffer-file-name))
                   level (nth 5 entry))
             ;; Insert the section info
             (push entry (cdr tail))

             ;; We are done unless we use section numbers
             (unless (nth 1 reftex-label-menu-flags) (throw 'exit nil))

             ;; Update the remaining toc items
             (setq tail (cdr tail))
             (while (and (setq tail (memq (assq 'toc (cdr tail)) tail))
                         (setq entry (car tail))
                         (>= (nth 5 entry) level))
               (setq star (string-search "*" (nth 6 entry))
                     context (nth 2 entry)
                     section-number
                     (reftex-section-number (nth 5 entry) star))
               (when (string-match "\\`\\([ \t]*\\)\\([.0-9A-Z]+\\)\\(.*\\)"
                                   context)
                 (when (and (not appendix)
                            (>= (string-to-char (match-string 2)) ?A))
                   ;; Just entered the appendix.  Get out.
                   (throw 'exit nil))

                 ;; Change the section number.
                 (setf (nth 2 entry)
                       (concat (match-string 1 context)
                               section-number
                               (match-string 3 context))))))
            ((match-end 10)
             ;; Index entry
             (and reftex-support-index
                  (setq entry (reftex-index-info-safe buffer-file-name))
                  ;; FIXME: (add-to-list 'reftex--index-tags (nth 1 index-entry))
                  (push entry (cdr tail))))))))))

    (error nil))
  )

(defsubst reftex-move-to-previous-arg (&optional bound)
  "Assuming that we are in front of a macro argument,
move backward to the closing parenthesis of the previous argument.
This function understands the splitting of macros over several lines
in TeX."
  (cond
   ;; Just to be quick:
   ((memq (preceding-char) '(?\] ?\})))
   ;; Do a search
   ((and reftex-allow-detached-macro-args
         (re-search-backward
          "[]}][ \t]*[\n\r]?\\([ \t]*%[^\n\r]*[\n\r]\\)*[ \t]*\\=" bound t))
    (goto-char (1+ (match-beginning 0)))
    t)
   (t nil)))

;;;###autoload
(defun reftex-what-macro-safe (which &optional bound)
  "Call `reftex-what-macro' with special syntax table."
  (reftex-with-special-syntax
   (reftex-what-macro which bound)))

;;;###autoload
(defun reftex-what-macro (which &optional bound)
  "Find out if point is within the arguments of any TeX-macro.
The return value is either (\"\\macro\" . (point)) or a list of them.

If WHICH is nil, immediately return nil.
If WHICH is 1, return innermost enclosing macro.
If WHICH is t, return list of all macros enclosing point.
If WHICH is a list of macros, look only for those macros and return the
  name of the first macro in this list found to enclose point.
If the optional BOUND is an integer, bound backwards directed
  searches to this point.  If it is nil, limit to nearest \\section -
  like statement.

This function is pretty stable, but can be fooled if the text contains
things like \\macro{aa}{bb} where \\macro is defined to take only one
argument.  As RefTeX cannot know this, the string \"bb\" would still be
considered an argument of macro \\macro."
  (unless reftex-section-regexp (reftex-compile-variables))
  (catch 'exit
    (if (null which) (throw 'exit nil))
    (let ((bound (or bound (save-excursion (re-search-backward
                                            reftex-section-regexp nil 1)
                                           (point))))
          pos cmd-list cmd cnt cnt-opt entry)
      (save-restriction
        (save-excursion
          (narrow-to-region (max (point-min) bound) (point-max))
          ;; move back out of the current parenthesis
          (while (condition-case nil
                     (let ((forward-sexp-function nil))
                       (up-list -1) t)
                   (error nil))
            (setq cnt 1 cnt-opt 0)
            ;; move back over any touching sexps
            (while (and (reftex-move-to-previous-arg bound)
                        (condition-case nil
                            (let ((forward-sexp-function nil))
                              (backward-sexp) t)
                          (error nil)))
              (if (eq (following-char) ?\[) (cl-incf cnt-opt))
              (cl-incf cnt))
            (setq pos (point))
            (when (and (or (= (following-char) ?\[)
                           (= (following-char) ?\{))
                       (re-search-backward "\\\\[*a-zA-Z]+\\=" nil t))
              (setq cmd (reftex-match-string 0))
              (when (looking-at "\\\\begin{[^}]*}")
                (setq cmd (reftex-match-string 0)
                      cnt (1- cnt)))
              ;; This does ignore optional arguments.  Very hard to fix.
              (when (setq entry (assoc cmd reftex-env-or-mac-alist))
                (if (> cnt (or (nth 4 entry) 100))
                    (setq cmd nil)))
              (cond
               ((null cmd))
               ((eq t which)
                (push (cons cmd (point)) cmd-list))
               ((or (eq 1 which) (member cmd which))
                (throw 'exit (cons cmd (point))))))
            (goto-char pos)))
        (nreverse cmd-list)))))

;;;###autoload
(defun reftex-what-environment (which &optional bound)
  "Find out if point is inside a LaTeX environment.
The return value is (e.g.) either (\"equation\" . (point)) or a list of
them.

If WHICH is nil, immediately return nil.
If WHICH is 1, return innermost enclosing environment.
If WHICH is t, return list of all environments enclosing point.
If WHICH is a list of environments, look only for those environments and
  return the name of the first environment in this list found to enclose
  point.

If the optional BOUND is an integer, bound backwards directed searches to
this point.  If it is nil, limit to nearest \\section - like statement."
  (unless reftex-section-regexp (reftex-compile-variables))
  (catch 'exit
    (save-excursion
      (if (null which) (throw 'exit nil))
      (let ((bound (or bound (save-excursion (re-search-backward
                                              reftex-section-regexp nil 1)
                                             (point))))
            env-list end-list env)
        (while (re-search-backward "\\\\\\(begin\\|end\\){\\([^}]+\\)}"
                                   bound t)
          (setq env (buffer-substring-no-properties
                     (match-beginning 2) (match-end 2)))
          (cond
           ((string= (match-string 1) "end")
            (push env end-list))
           ((equal env (car end-list))
            (setq end-list (cdr end-list)))
           ((eq t which)
            (push (cons env (point)) env-list))
           ((or (eq 1 which) (member env which))
            (throw 'exit (cons env (point))))))
        (nreverse env-list)))))

;;;###autoload
(defun reftex-what-special-env (which &optional bound)
  "Run the special environment parsers and return the matches.

The return value is (e.g.) either (\"my-parser-function\" . (point))
or a list of them.

If WHICH is nil, immediately return nil.
If WHICH is 1, return innermost enclosing environment.
If WHICH is t, return list of all environments enclosing point.
If WHICH is a list of environments, look only for those environments and
  return the name of the first environment in this list found to enclose
  point."
  (unless reftex-section-regexp (reftex-compile-variables))
  (catch 'exit
    (save-excursion
      (if (null reftex-special-env-parsers) (throw 'exit nil))
      (if (null which) (throw 'exit nil))
      (let ((bound (or bound (save-excursion (re-search-backward
                                              reftex-section-regexp nil 1)
                                             (point))))
            (fun-list (if (listp which)
                          (mapcar (lambda (x) (if (memq x which) x nil))
                                  reftex-special-env-parsers)
                        reftex-special-env-parsers))
            specials rtn)
        ;; Call all functions
        (setq specials (mapcar
                        (lambda (fun)
                          (save-excursion
                            (setq rtn (and fun (funcall fun bound)))
                            (if rtn (cons (symbol-name fun) rtn) nil)))
                        fun-list))
        ;; Delete the non-matches
        (setq specials (delq nil specials))
        ;; Sort
        (setq specials (sort specials (lambda (a b) (> (cdr a) (cdr b)))))
        (if (eq which t)
            specials
          (car specials))))))

(defsubst reftex-move-to-next-arg (&optional _ignore)
  "Assuming that we are at the end of a macro name or a macro argument,
move forward to the opening parenthesis of the next argument.
This function understands the splitting of macros over several lines
in TeX."
  (cond
   ;; Just to be quick:
   ((memq (following-char) '(?\[ ?\{)))
   ;; Do a search
   ((and reftex-allow-detached-macro-args
         (looking-at "[ \t]*[\n\r]?\\([ \t]*%[^\n\r]*[\n\r]\\)*[ \t]*[[{]"))
    (goto-char (1- (match-end 0)))
    t)
   (t nil)))

(defun reftex-nth-arg-wrapper (key)
  (let ((entry (assoc key reftex-env-or-mac-alist)))
    (reftex-nth-arg (nth 5 entry) (nth 6 entry))))

;;;###autoload
(defun reftex-nth-arg (n &optional opt-args)
  "Return the Nth following {} or [] parentheses content.
OPT-ARGS is a list of argument numbers which are optional."

  ;; If we are sitting at a macro start, skip to end of macro name.
  (and (eq (following-char) ?\\) (skip-chars-forward "a-zA-Z*\\\\"))

  (if (= n 1000)
      ;; Special case:  Skip all touching arguments
      (progn
        (reftex-move-over-touching-args)
        (reftex-context-substring))

    ;; Do the real thing.
    (let ((cnt 1))

      (when (reftex-move-to-next-arg)

        (while (< cnt n)
          (while (and (member cnt opt-args)
                      (eq (following-char) ?\{))
            (cl-incf cnt))
          (when (< cnt n)
            (unless (and (condition-case nil
                             (or (forward-list 1) t)
                           (error nil))
                         (reftex-move-to-next-arg)
                         (cl-incf cnt))
              (setq cnt 1000))))

        (while (and (memq cnt opt-args)
                    (eq (following-char) ?\{))
          (cl-incf cnt)))
      (if (and (= n cnt)
               (> (skip-chars-forward "{[") 0))
          (reftex-context-substring)
        nil))))

;;;###autoload
(defun reftex-move-over-touching-args ()
  (condition-case nil
      (while (memq (following-char) '(?\[ ?\{))
        (forward-list 1))
    (error nil)))

(defun reftex-context-substring (&optional to-end)
  "Return up to 150 chars from point.
When point is just after a { or [, limit string to matching parenthesis."
  (cond
   (to-end
    ;; Environment - find next \end
    (buffer-substring-no-properties
     (point)
     (min (+ (point) 150)
          (save-match-data
            ;; FIXME: This is not perfect
            (if (re-search-forward "\\\\end{" nil t)
                (match-beginning 0)
              (point-max))))))
   ((memq (preceding-char) '(?\{ ?\[))
    ;; Inside a list - get only the list.
    (buffer-substring-no-properties
     (point)
     (min (+ (point) 150)
          (point-max)
          (condition-case nil
              (let ((forward-sexp-function nil)) ;Unneeded fanciness.
                (up-list 1)
                (1- (point)))
            (error (point-max))))))
   (t
    ;; no list - just grab 150 characters
    (buffer-substring-no-properties (point)
                                    (min (+ (point) 150) (point-max))))))

;; Variable holding the vector with section numbers
(defvar reftex-section-numbers (make-vector reftex-max-section-depth 0))

;;;###autoload
(defun reftex-init-section-numbers (&optional toc-entry appendix)
  "Initialize section numbers with zeros or with what is found in the TOC-ENTRY."
  (let* ((level  (or (nth 5 toc-entry) -1))
         (numbers (nreverse (split-string (or (nth 6 toc-entry) "") "\\.")))
         (depth (1- (length reftex-section-numbers)))
         (i depth) number-string)
    (while (>= i 0)
      (if (> i level)
          (aset reftex-section-numbers i 0)
        (setq number-string (or (car numbers) "0"))
        (if (string-match "\\`[A-Z]\\'" number-string)
            (aset reftex-section-numbers i
                  (- (string-to-char number-string) ?A -1))
            (aset reftex-section-numbers i (string-to-number number-string)))
        (pop numbers))
      (cl-decf i)))
  (put 'reftex-section-numbers 'appendix appendix))

;;;###autoload
(defun reftex-section-number (&optional level star)
  "Return a string with the current section number.
When LEVEL is non-nil, increase section numbers on that level."
  (let* ((depth (1- (length reftex-section-numbers))) idx n (string "")
         (appendix (get 'reftex-section-numbers 'appendix))
         (partspecial (and (not reftex-part-resets-chapter)
                           (equal level 0))))
    ;; partspecial means, this is a part statement.
    ;; Parts do not reset the chapter counter, and the part number is
    ;; not included in the numbering of other sectioning levels.
    (when level
      (when (and (> level -1) (not star))
        (aset reftex-section-numbers
              level (1+ (aref reftex-section-numbers level))))
      (setq idx (1+ level))
      (when (not star)
        (while (<= idx depth)
          (if (or (not partspecial)
                  (not (= idx 1)))
              (aset reftex-section-numbers idx 0))
          (cl-incf idx))))
    (if partspecial
        (setq string (concat "Part " (reftex-roman-number
                                      (aref reftex-section-numbers 0))))
      (setq idx (if reftex-part-resets-chapter 0 1))
      (while (<= idx depth)
        (setq n (aref reftex-section-numbers idx))
        (if (not (and partspecial (not (equal string ""))))
            (setq string (concat string (if (not (string= string "")) "." "")
                                 (int-to-string n))))
        (cl-incf idx))
      (save-match-data
        (if (string-match "\\`\\([@0]\\.\\)+" string)
            (setq string (replace-match "" nil nil string)))
        (if (string-match "\\(\\.0\\)+\\'" string)
            (setq string (replace-match "" nil nil string)))
        (if (and appendix
                 (string-match "\\`[0-9]+" string))
            (setq string
                  (concat
                   (char-to-string
                    (1- (+ ?A (string-to-number (match-string 0 string)))))
                   (substring string (match-end 0))))))
      (if star
          (concat (make-string (1- (length string)) ?\ ) "*")
        string))))

(defun reftex-roman-number (n)
  "Return as a string the roman number equal to N."
  (let ((nrest n)
        (string "")
        (list '((1000 . "M") ( 900 . "CM") ( 500 . "D") ( 400 . "CD")
                ( 100 . "C") (  90 . "XC") (  50 . "L") (  40 . "XL")
                (  10 . "X") (   9 . "IX") (   5 . "V") (   4 . "IV")
                (   1 . "I")))
        listel i s)
    (while (>= nrest 1)
      (setq listel (pop list)
            i (car listel)
            s (cdr listel))
      (while (>= nrest i)
        (setq string (concat string s)
              nrest (- nrest i))))
    string))

(provide 'reftex-parse)

;;; reftex-parse.el ends here

;; Local Variables:
;; generated-autoload-file: "reftex-loaddefs.el"
;; End:
