;;; octave.el --- editing octave source files under emacs  -*- lexical-binding: t; -*-

;; Copyright (C) 1997-2025 Free Software Foundation, Inc.

;; Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at>
;;	   John Eaton <jwe@octave.org>
;; Maintainer: emacs-devel@gnu.org
;; Keywords: languages

;; 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:

;; This package provides Emacs support for Octave.  It defines a major
;; mode for editing Octave code and contains code for interacting with
;; an inferior Octave process using comint.

;; See the documentation of `octave-mode' and `run-octave' for further
;; information on usage and customization.

;;; Code:
(require 'comint)

(defgroup octave nil
  "Editing Octave code."
  :link '(custom-manual "(octave-mode)Top")
  :link '(url-link "https://www.gnu.org/s/octave")
  :link '(custom-group-link :tag "Font Lock Faces group" font-lock-faces)
  :group 'languages)

(define-obsolete-function-alias 'octave-submit-bug-report
  'report-emacs-bug "24.4")

(define-abbrev-table 'octave-abbrev-table nil
  "Abbrev table for Octave's reserved words.
Used in `octave-mode' and `inferior-octave-mode' buffers.")

(defvar octave-comment-char ?#
  "Character to start an Octave comment.")

(defvar octave-comment-start (char-to-string octave-comment-char)
  "Octave-specific `comment-start' (which see).")

(defvar octave-comment-start-skip "\\(^\\|\\S<\\)\\(?:%!\\|\\s<+\\)\\s-*"
  "Octave-specific `comment-start-skip' (which see).")

(defvar octave-function-header-regexp
  (concat "^\\s-*\\_<\\(function\\)\\_>"
	  "\\([^=;(\n]*=[ \t]*\\|[ \t]*\\)\\(\\(?:\\w\\|\\s_\\)+\\)\\_>")
  "Regexp to match an Octave function header.
The string `function' and its name are given by the first and third
parenthetical grouping.")


(defvar-keymap octave-mode-map
  :doc "Keymap used in Octave mode."
  "M-."         #'octave-find-definition
  "C-M-j"       #'octave-indent-new-comment-line
  "C-c C-p"     #'octave-previous-code-line
  "C-c C-n"     #'octave-next-code-line
  "C-c C-a"     #'octave-beginning-of-line
  "C-c C-e"     #'octave-end-of-line
  "<remap> <down-list>" #'smie-down-list
  "C-c C-M-h"   #'octave-mark-block
  "C-c ]"       #'smie-close-block
  "C-c /"       #'smie-close-block
  "C-c ;"       #'octave-update-function-file-comment
  "C-h d"       #'octave-help
  "C-h a"       #'octave-lookfor
  "C-c C-l"     #'octave-source-file
  "C-c C-f"     #'octave-insert-defun
  "C-c C-i l"   #'octave-send-line
  "C-c C-i b"   #'octave-send-block
  "C-c C-i f"   #'octave-send-defun
  "C-c C-i r"   #'octave-send-region
  "C-c C-i a"   #'octave-send-buffer
  "C-c C-i s"   #'octave-show-process-buffer
  "C-c C-i q"   #'octave-hide-process-buffer
  "C-c C-i k"   #'octave-kill-process
  "C-c C-i C-l" #'octave-send-line
  "C-c C-i C-b" #'octave-send-block
  "C-c C-i C-f" #'octave-send-defun
  "C-c C-i C-r" #'octave-send-region
  "C-c C-i C-a" #'octave-send-buffer
  "C-c C-i C-s" #'octave-show-process-buffer
  "C-c C-i C-q" #'octave-hide-process-buffer
  "C-c C-i C-k" #'octave-kill-process)

(easy-menu-define octave-mode-menu octave-mode-map
  "Menu for Octave mode."
  '("Octave"
    ["Split Line at Point"          octave-indent-new-comment-line t]
    ["Previous Code Line"           octave-previous-code-line t]
    ["Next Code Line"               octave-next-code-line t]
    ["Begin of Line"                octave-beginning-of-line t]
    ["End of Line"                  octave-end-of-line t]
    ["Mark Block"                   octave-mark-block t]
    ["Close Block"                  smie-close-block t]
    "---"
    ["Start Octave Process"         run-octave t]
    ["Documentation Lookup"         info-lookup-symbol t]
    ["Help on Function"             octave-help t]
    ["Search help"                  octave-lookfor t]
    ["Find Function Definition"     octave-find-definition t]
    ["Insert Function"              octave-insert-defun t]
    ["Update Function File Comment" octave-update-function-file-comment t]
    "---"
    ["Function Syntax Hints" (eldoc-mode 'toggle)
     :style toggle :selected (bound-and-true-p eldoc-mode)
     :help "Display function signatures after typing `SPC' or `('"]
    ["Delimiter Matching"           show-paren-mode
     :style toggle :selected show-paren-mode
     :help "Highlight matched pairs such as `if ... end'"
     :visible (fboundp 'smie--matching-block-data)]
    ["Auto Fill"                    auto-fill-mode
     :style toggle :selected auto-fill-function
     :help "Automatic line breaking"]
    ["Electric Layout"              electric-layout-mode
     :style toggle :selected electric-layout-mode
     :help "Automatically insert newlines around some chars"]
    "---"
    ("Debug"
     ["Send Current Line"       octave-send-line t]
     ["Send Current Block"      octave-send-block t]
     ["Send Current Function"   octave-send-defun t]
     ["Send Region"             octave-send-region t]
     ["Send Buffer"             octave-send-buffer t]
     ["Source Current File"     octave-source-file t]
     ["Show Process Buffer"     octave-show-process-buffer t]
     ["Hide Process Buffer"     octave-hide-process-buffer t]
     ["Kill Process"            octave-kill-process t])
    "---"
    ["Octave Mode Manual"       (info "(octave-mode)Top") t]
    ["Customize Octave"         (customize-group 'octave) t]
    ["Submit Bug Report"        report-emacs-bug t]))

(defvar octave-mode-syntax-table
  (let ((table (make-syntax-table)))
    (modify-syntax-entry ?\r " "  table)
    (modify-syntax-entry ?+ "."   table)
    (modify-syntax-entry ?- "."   table)
    (modify-syntax-entry ?= "."   table)
    (modify-syntax-entry ?* "."   table)
    (modify-syntax-entry ?/ "."   table)
    (modify-syntax-entry ?> "."   table)
    (modify-syntax-entry ?< "."   table)
    (modify-syntax-entry ?& "."   table)
    (modify-syntax-entry ?| "."   table)
    (modify-syntax-entry ?! "."   table)
    (modify-syntax-entry ?\\ "."  table)
    (modify-syntax-entry ?\' "."  table)
    (modify-syntax-entry ?\` "."  table)
    (modify-syntax-entry ?. "."   table)
    (modify-syntax-entry ?\" "\"" table)
    (modify-syntax-entry ?_ "_"   table)
    ;; The "b" flag only applies to the second letter of the comstart and
    ;; the first letter of the comend, i.e. a "4b" below would be ineffective.
    ;; If we try to put `b' on the single-line comments, we get a similar
    ;; problem where the % and # chars appear as first chars of the 2-char
    ;; comend, so the multi-line ender is also turned into style-b.
    ;; So we need the new "c" comment style.
    (modify-syntax-entry ?\% "< 13"  table)
    (modify-syntax-entry ?\# "< 13"  table)
    (modify-syntax-entry ?\{ "(} 2c"  table)
    (modify-syntax-entry ?\} "){ 4c"  table)
    (modify-syntax-entry ?\n ">"  table)
    table)
  "Syntax table in use in `octave-mode' buffers.")

(defcustom octave-font-lock-texinfo-comment t
  "Control whether to highlight the texinfo comment block."
  :type 'boolean
  :version "24.4")

(defcustom octave-blink-matching-block t
  "Control the blinking of matching Octave block keywords.
Non-nil means show matching begin of block when inserting a space,
newline or semicolon after an else or end keyword."
  :type 'boolean)

(defcustom octave-block-offset 2
  "Extra indentation applied to statements in Octave block structures."
  :type 'integer
  :safe #'integerp)

(defvar octave-block-comment-start
  (concat (make-string 2 octave-comment-char) " ")
  "String to insert to start a new Octave comment on an empty line.")

(defcustom octave-continuation-offset 4
  "Extra indentation applied to Octave continuation lines."
  :type 'integer)

(eval-and-compile
  (defconst octave-continuation-marker-regexp "\\\\\\|\\.\\.\\."))

(defvar octave-continuation-regexp
  (concat "[^#%\n]*\\(" octave-continuation-marker-regexp
          "\\)\\s-*\\(\\s<.*\\)?$"))

(defconst octave-continuation-string "..."
  "Character string used for Octave continuation lines.
Joins current line with following line, except within
double-quoted strings, where `octave-string-continuation-marker'
is used instead.")

(defconst octave-string-continuation-marker "\\"
  "Line continuation marker for double-quoted Octave strings.
Non-string statements use `octave-continuation-string'.")

(defvar octave-mode-imenu-generic-expression
  (list
   ;; Functions
   (list nil octave-function-header-regexp 3))
  "Imenu expression for Octave mode.  See `imenu-generic-expression'.")

(defcustom octave-mode-hook nil
  "Hook to be run when Octave mode is started."
  :type 'hook)

(defcustom octave-send-show-buffer t
  "Non-nil means display `inferior-octave-buffer' after sending to it."
  :type 'boolean)

(defcustom octave-send-line-auto-forward t
  "Control auto-forward after sending to the inferior Octave process.
Non-nil means always go to the next Octave code line after sending."
  :type 'boolean)

(defcustom octave-send-echo-input t
  "Non-nil means echo input sent to the inferior Octave process."
  :type 'boolean)


;;; SMIE indentation

(require 'smie)

(let-when-compile
    ((operator-table
      ;; Use '__operators__' in Octave REPL to get a full list?
      '((assoc ";" "\n") (assoc ",") ;The doc says they have equal precedence!?
        (right "=" "+=" "-=" "*=" "/=")
        (assoc "&&") (assoc "||") ; The doc claims they have equal precedence!?
        (assoc "&") (assoc "|") ; The doc claims they have equal precedence!?
        (nonassoc "<" "<=" "==" ">=" ">" "!=" "~=")
        (nonassoc ":")                  ;No idea what this is.
        (assoc "+" "-")
        (assoc "*" "/" "\\" ".\\" ".*" "./")
        (nonassoc "'" ".'")
        (nonassoc "++" "--" "!" "~")    ;And unary "+" and "-".
        (right "^" "**" ".^" ".**")
        ;; It's not really an operator, but for indentation purposes it
        ;; could be convenient to treat it as one.
        (assoc "...")))

     (matchedrules
      ;; We can't distinguish the first element in a sequence with
      ;; precedence grammars, so we can't distinguish the condition
      ;; of the `if' from the subsequent body, for example.
      ;; This has to be done later in the indentation rules.
      '(("try" exp "catch" exp "end_try_catch")
        ("unwind_protect" exp
         "unwind_protect_cleanup" exp "end_unwind_protect")
        ("for" exp "endfor")
        ("parfor" exp "endparfor")
        ("while" exp "endwhile")
        ("if" exp "endif")
        ("if" exp "else" exp "endif")
        ("if" exp "elseif" exp "else" exp "endif")
        ("if" exp "elseif" exp "elseif" exp "else" exp "endif")
        ("switch" exp "case" exp "endswitch")
        ("switch" exp "case" exp "otherwise" exp "endswitch")
        ("switch" exp "case" exp "case" exp "otherwise" exp "endswitch")
        ("function" exp "endfunction")
        ("enumeration" exp "endenumeration")
        ("events" exp "endevents")
        ("methods" exp "endmethods")
        ("properties" exp "endproperties")
        ("classdef" exp "endclassdef")
        ("spmd" exp "endspmd")
        ))

     (bnf-table
      `((atom)
        ;; FIXME: We don't parse these declarations correctly since
        ;; SMIE *really* likes to parse "a b = 2 c" as "(a b) = (2 c)".
        ;; IOW to do it right, we'd need to change octave-smie-*ward-token
        ;; so that the spaces between vars in var-decls are lexed as
        ;; something like ",".
        ;; Doesn't seem worth the trouble/slowdown for now.
        ;; We could hack smie-rules so as to work around the bad parse,
        ;; but even that doesn't seem worth the trouble.
        (var-decls (atom "=" atom)) ;; (var-decls "," var-decls)
        (single-exp (atom "=" atom))
        (exp (exp "\n" exp)
             ;; We need to mention at least one of the operators in this part
             ;; of the grammar: if the BNF and the operator table have
             ;; no overlap, SMIE can't know how they relate.
             (exp ";" exp)
             ("do" exp "until" single-exp)
             ,@matchedrules
           ;; For every rule that ends in "endfoo", add a corresponding
           ;; rule which uses "end" instead.
           ,@(mapcar (lambda (rule) (nconc (butlast rule) '("end")))
                     matchedrules)
           ("global" var-decls) ("persistent" var-decls)
           ;; These aren't super-important, but having them here
           ;; makes it easier to extract all keywords.
           ("break") ("continue") ("return")
           ;; The following rules do not correspond to valid code AFAIK,
           ;; but they lead to a grammar that degrades more gracefully
           ;; on incomplete/incorrect code.  It also helps us in
           ;; computing octave--block-offset-keywords.
           ("try" exp "end") ("unwind_protect" exp "end")
           )
      ;; (fundesc (atom "=" atom))
      )))

(defconst octave-smie-grammar
  (eval-when-compile
    (smie-prec2->grammar
     (smie-merge-prec2s
      (smie-bnf->prec2 bnf-table '((assoc "\n" ";")))
      (smie-precs->prec2 operator-table)))))

(defconst octave-operator-regexp
  (eval-when-compile
    (regexp-opt (remove "\n" (apply #'append
                                    (mapcar #'cdr operator-table)))))))

;; Tokenizing needs to be refined so that ";;" is treated as two
;; tokens and also so as to recognize the \n separator (and
;; corresponding continuation lines).

(defun octave-smie--funcall-p ()
  "Return non-nil if we're in an expression context.  Move point."
  (looking-at "[ \t]*("))

(defun octave-smie--end-index-p ()
  (let ((ppss (syntax-ppss)))
    (and (nth 1 ppss)
         (memq (char-after (nth 1 ppss)) '(?\( ?\[ ?\{)))))

(defun octave-smie--in-parens-p ()
  (let ((ppss (syntax-ppss)))
    (and (nth 1 ppss)
         (eq ?\( (char-after (nth 1 ppss))))))

(defun octave-smie-backward-token ()
  (let ((pos (point)))
    (forward-comment (- (point)))
    (cond
     ((and (not (eq (char-before) ?\;)) ;Coalesce ";" and "\n".
           (> pos (line-end-position))
           (if (looking-back octave-continuation-marker-regexp (- (point) 3))
               (progn
                 (goto-char (match-beginning 0))
                 (forward-comment (- (point)))
                 nil)
             t)
           (not (octave-smie--in-parens-p)))
      (skip-chars-forward " \t")
      ;; Why bother distinguishing \n and ;?
      ";") ;;"\n"
     ((and (looking-back octave-operator-regexp (- (point) 3) 'greedy)
           ;; Don't mistake a string quote for a transpose.
           (not (looking-back "\\s\"" (1- (point)))))
      (goto-char (match-beginning 0))
      (match-string-no-properties 0))
     (t
      (let ((tok (smie-default-backward-token)))
        (cond
         ((equal tok "enumeration")
          (if (save-excursion (smie-default-forward-token)
                              (octave-smie--funcall-p))
              "enumeration (function)"
            tok))
         ((equal tok "end") (if (octave-smie--end-index-p) "end (index)" tok))
         (t tok)))))))

(defun octave-smie-forward-token ()
  (skip-chars-forward " \t")
  (when (looking-at (eval-when-compile
                      (concat "\\(" octave-continuation-marker-regexp
                              "\\)[ \t]*\\($\\|[%#]\\)")))
    (goto-char (match-end 1))
    (forward-comment 1))
  (cond
   ((and (looking-at "[%#\n]")
         (not (or (save-excursion (skip-chars-backward " \t")
                                  ;; Only add implicit ; when needed.
                                  (or (bolp) (eq (char-before) ?\;)))
                  (octave-smie--in-parens-p))))
    (if (eolp) (forward-char 1) (forward-comment 1))
    ;; Why bother distinguishing \n and ;?
    ";") ;;"\n"
   ((progn (forward-comment (point-max)) nil))
   ((looking-at ";[ \t]*\\($\\|[%#]\\)")
    ;; Combine the ; with the subsequent \n.
    (goto-char (match-beginning 1))
    (forward-comment 1)
    ";")
   ((and (looking-at octave-operator-regexp)
         ;; Don't mistake a string quote for a transpose.
         (not (looking-at "\\s\"")))
    (goto-char (match-end 0))
    (match-string-no-properties 0))
   (t
    (let ((tok (smie-default-forward-token)))
      (cond
       ((equal tok "enumeration")
        (if (octave-smie--funcall-p)
            "enumeration (function)"
          tok))
       ((equal tok "end") (if (octave-smie--end-index-p) "end (index)" tok))
       (t tok))))))

(defconst octave--block-offset-keywords
  (let* ((end-prec (nth 1 (assoc "end" octave-smie-grammar)))
         (end-matchers
          (delq nil
                (mapcar (lambda (x) (if (eq end-prec (nth 2 x)) (car x)))
                        octave-smie-grammar))))
    ;; Not sure if it would harm to keep "switch", but the previous code
    ;; excluded it, presumably because there shouldn't be any code on
    ;; the lines between "switch" and "case".
    (delete "switch" end-matchers)))

(defun octave-smie-rules (kind token)
  (pcase (cons kind token)
    ;; We could set smie-indent-basic instead, but that would have two
    ;; disadvantages:
    ;; - changes to octave-block-offset wouldn't take effect immediately.
    ;; - edebug wouldn't show the use of this variable.
    ('(:elem . basic) octave-block-offset)
    (`(:list-intro . ,(or "global" "persistent")) t)
    ;; Since "case" is in the same BNF rules as switch..end, SMIE by default
    ;; aligns it with "switch".
    ('(:before . "case") (if (not (smie-rule-sibling-p)) octave-block-offset))
    ('(:after . ";")
     (if (apply #'smie-rule-parent-p octave--block-offset-keywords)
         (smie-rule-parent octave-block-offset)
       ;; For (invalid) code between switch and case.
       ;; (if (smie-rule-parent-p "switch") 4)
       nil))
    ('(:after . "=") (smie-rule-parent octave-block-offset))))

(defun octave-indent-comment ()
  "A function for `smie-indent-functions' (which see)."
  (save-excursion
    (back-to-indentation)
    (cond
     ((octave-in-string-or-comment-p) nil)
     ((looking-at-p "\\(\\s<\\)\\1\\{2,\\}")
      0)
     ;; Exclude %{, %} and %!.
     ((and (looking-at-p "\\s<\\(?:[^{}!]\\|$\\)")
           (not (looking-at-p "\\(\\s<\\)\\1")))
      (comment-choose-indent)))))


(defvar octave-reserved-words
  (delq nil
        (mapcar (lambda (x)
                  (setq x (car x))
                  (and (stringp x) (string-match "\\`[[:alpha:]]" x) x))
                octave-smie-grammar))
  "Reserved words in Octave.")

(defvar octave-font-lock-keywords
  (list
   ;; Fontify all builtin keywords.
   (cons (concat "\\_<" (regexp-opt octave-reserved-words) "\\_>")
         'font-lock-keyword-face)
   ;; Note: 'end' also serves as the last index in an indexing expression,
   ;; and 'enumerate' is also a function.
   ;; Ref: https://www.mathworks.com/help/matlab/ref/end.html
   ;; Ref: https://www.mathworks.com/help/matlab/ref/enumeration.html
   (list (lambda (limit)
           (while (re-search-forward "\\_<en\\(?:d\\|umeratio\\(n\\)\\)\\_>"
                                     limit 'move)
             (let ((beg (match-beginning 0))
                   (end (match-end 0)))
               (unless (octave-in-string-or-comment-p)
                 (when (if (match-end 1)
                           (octave-smie--funcall-p)
                         (octave-smie--end-index-p))
                   (put-text-property beg end 'face nil)))))
           nil))
   ;; Fontify all operators.
   (cons octave-operator-regexp 'font-lock-builtin-face)
   ;; Fontify all function declarations.
   (list octave-function-header-regexp
         '(1 font-lock-keyword-face)
         '(3 font-lock-function-name-face nil t)))
  "Additional Octave expressions to highlight.")

(defun octave-syntax-propertize-function (start end)
  (goto-char start)
  (octave-syntax-propertize-sqs end)
  (funcall (syntax-propertize-rules
            ("\\\\" (0 (when (eq (nth 3 (save-excursion
                                          (syntax-ppss (match-beginning 0))))
                                 ?\")
                         (string-to-syntax "\\"))))
            ;; Try to distinguish the string-quotes from the transpose-quotes.
            ("\\(?:^\\|[[({,; ]\\)\\('\\)"
             (1 (prog1 "\"'" (octave-syntax-propertize-sqs end)))))
           (point) end))

(defun octave-syntax-propertize-sqs (end)
  "Propertize the content/end of single-quote strings."
  (when (eq (nth 3 (syntax-ppss)) ?\')
    ;; A '..' string.
    (when (re-search-forward
           "\\(?:\\=\\|[^']\\)\\(?:''\\)*\\('\\)\\($\\|[^']\\)" end 'move)
      (goto-char (match-beginning 2))
      (when (eq (char-before (match-beginning 1)) ?\\)
        ;; Backslash cannot escape a single quote.
        (put-text-property (1- (match-beginning 1)) (match-beginning 1)
                           'syntax-table (string-to-syntax ".")))
      (put-text-property (match-beginning 1) (match-end 1)
                         'syntax-table (string-to-syntax "\"'")))))

(defvar electric-layout-rules)

;; FIXME: cc-mode.el also adds an entry for .m files, mapping them to
;; objc-mode.  We here rely on the fact that loaddefs.el is filled in
;; alphabetical order, so cc-mode.el comes before octave-mode.el, which lets
;; our entry come first!
;;;###autoload (add-to-list 'auto-mode-alist '("\\.m\\'" . octave-maybe-mode))

;;;###autoload
(defun octave-maybe-mode ()
  "Select `octave-mode' if the current buffer seems to hold Octave code."
  (if (save-excursion
        (with-syntax-table octave-mode-syntax-table
          (goto-char (point-min))
          (forward-comment (point-max))
          ;; FIXME: What about Octave files which don't start with "function"?
          (looking-at "function")))
      (octave-mode)
    (let ((x (rassq 'octave-maybe-mode auto-mode-alist)))
      (when x
        (let ((auto-mode-alist (remove x auto-mode-alist)))
          (set-auto-mode))))))

;;;###autoload
(define-derived-mode octave-mode prog-mode "Octave"
  "Major mode for editing Octave code.

Octave is a high-level language, primarily intended for numerical
computations.  It provides a convenient command line interface
for solving linear and nonlinear problems numerically.  Function
definitions can also be stored in files and used in batch mode.

See Info node `(octave-mode) Using Octave Mode' for more details.

Key bindings:
\\{octave-mode-map}"
  :abbrev-table octave-abbrev-table
  :group 'octave

  (smie-setup octave-smie-grammar #'octave-smie-rules
              :forward-token  #'octave-smie-forward-token
              :backward-token #'octave-smie-backward-token)
  (setq-local smie-indent-basic 'octave-block-offset)
  (add-hook 'smie-indent-functions #'octave-indent-comment nil t)

  (setq-local smie-blink-matching-triggers
              (cons ?\; smie-blink-matching-triggers))
  (unless octave-blink-matching-block
    (remove-hook 'post-self-insert-hook #'smie-blink-matching-open 'local))

  (setq-local electric-indent-chars
              (cons ?\; electric-indent-chars))
  ;; IIUC matlab-mode takes the opposite approach: it makes RET insert
  ;; a ";" at those places where it's correct (i.e. outside of parens).
  (setq-local electric-layout-rules '((?\; . after)))

  (setq-local comment-use-syntax t)
  (setq-local comment-start octave-comment-start)
  (setq-local comment-end "")
  (setq-local comment-start-skip octave-comment-start-skip)
  (setq-local comment-add 1)

  (setq-local parse-sexp-ignore-comments t)
  (setq-local paragraph-start (concat "\\s-*$\\|" page-delimiter))
  (setq-local paragraph-separate paragraph-start)
  (setq-local paragraph-ignore-fill-prefix t)
  (setq-local fill-paragraph-function 'octave-fill-paragraph)

  (setq-local fill-nobreak-predicate
              (lambda () (eq (octave-in-string-p) ?')))
  (add-function :around (local 'comment-line-break-function)
                #'octave--indent-new-comment-line)

  (setq font-lock-defaults '(octave-font-lock-keywords))

  (setq-local syntax-propertize-function #'octave-syntax-propertize-function)

  (setq-local imenu-generic-expression octave-mode-imenu-generic-expression)
  (setq-local imenu-case-fold-search nil)

  (setq-local add-log-current-defun-function #'octave-add-log-current-defun)

  (add-hook 'completion-at-point-functions 'octave-completion-at-point nil t)
  (add-hook 'before-save-hook 'octave-sync-function-file-names nil t)
  (setq-local beginning-of-defun-function 'octave-beginning-of-defun)
  (and octave-font-lock-texinfo-comment (octave-font-lock-texinfo-comment))
  (add-hook 'eldoc-documentation-functions 'octave-eldoc-function nil t))


(defcustom inferior-octave-program "octave"
  "Program invoked by `inferior-octave'."
  :type 'string)

(defcustom inferior-octave-buffer "*Inferior Octave*"
  "Name of buffer for running an inferior Octave process."
  :type 'string)

(defcustom inferior-octave-prompt
  ;; For Octave >= 3.8, default is always 'octave', see
  ;; https://hg.savannah.gnu.org/hgweb/octave/rev/708173343c50
  "\\(?:^octave\\(?:.bin\\|.exe\\)?\\(?:-[.0-9]+\\)?\\(?::[0-9]+\\)?\\|^debug\\|^\\)>+ "
  "Regexp to match prompts for the inferior Octave process."
  :type 'regexp)

(defcustom inferior-octave-prompt-read-only comint-prompt-read-only
  "If non-nil, the Octave prompt is read only.
See `comint-prompt-read-only' for details."
  :type 'boolean
  :version "24.4")

(defcustom inferior-octave-startup-file
  (let ((n (file-name-nondirectory inferior-octave-program)))
    (locate-user-emacs-file (format "init_%s.m" n) (format ".emacs-%s" n)))
  "Name of the inferior Octave startup file.
The contents of this file are sent to the inferior Octave process on
startup."
  :type '(choice (const :tag "None" nil) file)
  :version "24.4")

(defcustom inferior-octave-startup-args '("-i" "--no-line-editing")
  "List of command line arguments for the inferior Octave process.
For example, for suppressing the startup message and using `traditional'
mode, include \"-q\" and \"--traditional\"."
  :type '(repeat string)
  :version "24.4")

(define-obsolete-variable-alias 'inferior-octave-startup-hook
  'inferior-octave-mode-hook "24.4")

(defcustom inferior-octave-mode-hook nil
  "Hook to be run when Inferior Octave mode is started."
  :type 'hook)

(defcustom inferior-octave-error-regexp-alist
  '(("error:\\s-*\\(.*?\\) at line \\([0-9]+\\), column \\([0-9]+\\)"
     1 2 3 2 1)
    ("warning:\\s-*\\([^:\n]+\\):.*at line \\([0-9]+\\), column \\([0-9]+\\)"
     1 2 3 1 1))
  "Value for `compilation-error-regexp-alist' in inferior octave."
  :version "24.4"
  :type '(repeat (choice (symbol :tag "Predefined symbol")
                         (sexp :tag "Error specification"))))

(defvar inferior-octave-compilation-font-lock-keywords
  '(("\\_<PASS\\_>" . compilation-info-face)
    ("\\_<FAIL\\_>" . compilation-error-face)
    ("\\_<\\(warning\\):" 1 compilation-warning-face)
    ("\\_<\\(error\\):" 1 compilation-error-face)
    ("^\\s-*!!!!!.*\\|^.*failed$" . compilation-error-face))
  "Value for `compilation-mode-font-lock-keywords' in inferior octave.")

(defvar inferior-octave-process nil)

(defvar inferior-octave-mode-map
  (let ((map (make-sparse-keymap)))
    (set-keymap-parent map comint-mode-map)
    (define-key map "\M-." 'octave-find-definition)
    (define-key map "\t" 'completion-at-point)
    (define-key map "\C-hd" 'octave-help)
    (define-key map "\C-ha" 'octave-lookfor)
    ;; Same as in `shell-mode'.
    (define-key map "\M-?" 'comint-dynamic-list-filename-completions)
    (define-key map "\C-c\C-l" 'inferior-octave-dynamic-list-input-ring)
    (define-key map [menu-bar inout list-history]
      '("List Input History" . inferior-octave-dynamic-list-input-ring))
    map)
  "Keymap used in Inferior Octave mode.")

(defvar inferior-octave-mode-syntax-table
  (let ((table (make-syntax-table octave-mode-syntax-table)))
    table)
  "Syntax table in use in `inferior-octave-mode' buffers.")

(defvar inferior-octave-font-lock-keywords
  (list
   (cons inferior-octave-prompt 'font-lock-type-face))
  ;; Could certainly do more font locking in inferior Octave ...
  "Additional expressions to highlight in Inferior Octave mode.")

(defvar inferior-octave-output-list nil)
(defvar inferior-octave-output-string nil)
(defvar inferior-octave-receive-in-progress nil)

(defvar inferior-octave-dynamic-complete-functions
  '(inferior-octave-completion-at-point comint-filename-completion)
  "List of functions called to perform completion for inferior Octave.
This variable is used to initialize `comint-dynamic-complete-functions'
in the Inferior Octave buffer.")

(defvar info-lookup-mode)
(defvar compilation-error-regexp-alist)
(defvar compilation-mode-font-lock-keywords)

(declare-function compilation-forget-errors "compile" ())

(defun inferior-octave-process-live-p ()
  (process-live-p inferior-octave-process))

(define-derived-mode inferior-octave-mode comint-mode "Inferior Octave"
  "Major mode for interacting with an inferior Octave process.

See Info node `(octave-mode) Running Octave from Within Emacs' for more
details.

Key bindings:
\\{inferior-octave-mode-map}"
  :abbrev-table octave-abbrev-table
  :group 'octave

  (setq comint-prompt-regexp inferior-octave-prompt)

  (setq-local comment-use-syntax t)
  (setq-local comment-start octave-comment-start)
  (setq-local comment-end "")
  (setq comment-column 32)
  (setq-local comment-start-skip octave-comment-start-skip)

  (setq font-lock-defaults '(inferior-octave-font-lock-keywords nil nil))

  (setq-local info-lookup-mode 'octave-mode)
  (add-hook 'eldoc-documentation-functions 'octave-eldoc-function nil t)

  (setq-local comint-input-ring-file-name
              (or (getenv "OCTAVE_HISTFILE") "~/.octave_hist"))
  (setq-local comint-input-ring-size
              (string-to-number (or (getenv "OCTAVE_HISTSIZE") "1024")))
  (comint-read-input-ring t)
  (setq-local comint-dynamic-complete-functions
              inferior-octave-dynamic-complete-functions)
  (setq-local comint-prompt-read-only inferior-octave-prompt-read-only)
  (add-hook 'comint-input-filter-functions
            'inferior-octave-directory-tracker nil t)
  ;; http://thread.gmane.org/gmane.comp.gnu.octave.general/48572 [dead link]
  (add-hook 'window-configuration-change-hook
            'inferior-octave-track-window-width-change nil t)
  (setq-local compilation-error-regexp-alist inferior-octave-error-regexp-alist)
  (setq-local compilation-mode-font-lock-keywords
              inferior-octave-compilation-font-lock-keywords)
  (compilation-shell-minor-mode 1)
  (compilation-forget-errors))

;;;###autoload
(defun inferior-octave (&optional arg)
  "Run an inferior Octave process, I/O via `inferior-octave-buffer'.
This buffer is put in Inferior Octave mode.  See `inferior-octave-mode'.

Unless ARG is non-nil, switches to this buffer.

The elements of the list `inferior-octave-startup-args' are sent as
command line arguments to the inferior Octave process on startup.

Additional commands to be executed on startup can be provided either in
the file specified by `inferior-octave-startup-file' or by the default
startup file, `~/.emacs-octave'."
  (interactive "P")
  (let ((buffer (get-buffer-create inferior-octave-buffer)))
    (unless arg
      (pop-to-buffer buffer))
    (unless (comint-check-proc buffer)
      (with-current-buffer buffer
        (inferior-octave-startup)
        (inferior-octave-mode)))
    buffer))

;;;###autoload
(defalias 'run-octave 'inferior-octave)

(defun inferior-octave-startup ()
  "Start an inferior Octave process."
  (let ((proc (comint-exec-1
               (substring inferior-octave-buffer 1 -1)
               inferior-octave-buffer
               inferior-octave-program
               (append
                inferior-octave-startup-args
                ;; --no-gui is introduced in Octave > 3.7
                (and (not (member "--no-gui" inferior-octave-startup-args))
                     (zerop (process-file inferior-octave-program
                                          nil nil nil "--no-gui" "--help"))
                     '("--no-gui"))))))
    (set-process-filter proc 'inferior-octave-output-digest)
    (setq inferior-octave-process proc
          inferior-octave-output-list nil
          inferior-octave-output-string nil
          inferior-octave-receive-in-progress t)

    ;; This may look complicated ... However, we need to make sure that
    ;; we additional startup code only AFTER Octave is ready (otherwise,
    ;; output may be mixed up).  Hence, we need to digest the Octave
    ;; output to see when it issues a prompt.
    (while inferior-octave-receive-in-progress
      (unless (inferior-octave-process-live-p)
        ;; Spit out the error messages.
        (when inferior-octave-output-list
          (princ (concat (mapconcat 'identity inferior-octave-output-list "\n")
                         "\n")
                 (process-mark inferior-octave-process)))
        (error "Process `%s' died" inferior-octave-process))
      (accept-process-output inferior-octave-process))
    (goto-char (point-max))
    (set-marker (process-mark proc) (point))
    (insert-before-markers
     (concat
      (if (not (bobp)) "\n")
      (if inferior-octave-output-list
          (concat (mapconcat
                   'identity inferior-octave-output-list "\n")
                  "\n"))))

    ;; An empty secondary prompt, as e.g. obtained by '--braindead',
    ;; means trouble.
    (inferior-octave-send-list-and-digest (list "PS2\n"))
    (when (string-match "\\(PS2\\|ans\\) = *$"
                        (car inferior-octave-output-list))
      (inferior-octave-send-list-and-digest (list "PS2 ('> ');\n")))

    (inferior-octave-send-list-and-digest
     (list "disp (getenv ('OCTAVE_SRCDIR'))\n"))
    (process-put proc 'octave-srcdir
                 (unless (equal (car inferior-octave-output-list) "")
                   (car inferior-octave-output-list)))

    ;; O.K., now we are ready for the Inferior Octave startup commands.
    (inferior-octave-send-list-and-digest
     (list "more off;\n"
           (unless (equal inferior-octave-output-string ">> ")
             ;; See https://hg.savannah.gnu.org/hgweb/octave/rev/708173343c50
             "PS1 ('octave> ');\n")
           (when (and inferior-octave-startup-file
                      (file-exists-p inferior-octave-startup-file))
             (format "source ('%s');\n" inferior-octave-startup-file))))
    (when inferior-octave-output-list
      (insert-before-markers
       (mapconcat 'identity inferior-octave-output-list "\n")))

    ;; And finally, everything is back to normal.
    (set-process-filter proc 'comint-output-filter)
    ;; Just in case, to be sure a cd in the startup file won't have
    ;; detrimental effects.
    (with-demoted-errors "Octave resync error: %S"
      (inferior-octave-resync-dirs))
    ;; Generate a proper prompt, which is critical to
    ;; `comint-history-isearch-backward-regexp'.  Bug#14433.
    (comint-send-string proc "\n")))

(defun inferior-octave-completion-table ()
  (completion-table-with-cache
   (lambda (command)
     (inferior-octave-send-list-and-digest
      (list (format "completion_matches ('%s');\n" command)))
     (delete-consecutive-dups
      (sort inferior-octave-output-list 'string-lessp)))))

(defun inferior-octave-completion-at-point ()
  "Return the data to complete the Octave symbol at point."
  ;; https://debbugs.gnu.org/14300
  (unless (string-search "/" (or (comint--match-partial-filename) ""))
    (let ((beg (save-excursion
                 (skip-syntax-backward "w_" (comint-line-beginning-position))
                 (point)))
          (end (point)))
      (when (and beg (> end beg))
        (list beg end (completion-table-in-turn
                       (inferior-octave-completion-table)
                       'comint-completion-file-name-table))))))

(defun inferior-octave-dynamic-list-input-ring ()
  "List the buffer's input history in a help buffer."
  ;; We cannot use `comint-dynamic-list-input-ring', because it replaces
  ;; "completion" by "history reference" ...
  (interactive)
  (if (or (not (ring-p comint-input-ring))
          (ring-empty-p comint-input-ring))
      (message "No history")
    (let ((history nil)
          (history-buffer " *Input History*")
          (index (1- (ring-length comint-input-ring)))
          (conf (current-window-configuration)))
      ;; We have to build up a list ourselves from the ring vector.
      (while (>= index 0)
        (setq history (cons (ring-ref comint-input-ring index) history)
              index (1- index)))
      ;; Change "completion" to "history reference"
      ;; to make the display accurate.
      (with-output-to-temp-buffer history-buffer
        (display-completion-list history)
        (set-buffer history-buffer))
      (message "Hit space to flush")
      (let ((ch (read-event)))
        (if (eq ch ?\ )
            (set-window-configuration conf)
          (push ch unread-command-events))))))

(defun inferior-octave-output-digest (_proc string)
  "Special output filter for the inferior Octave process.
Save all output between newlines into `inferior-octave-output-list', and
the rest to `inferior-octave-output-string'."
  (setq string (concat inferior-octave-output-string string))
  (while (string-match "\n" string)
    (setq inferior-octave-output-list
	  (append inferior-octave-output-list
		  (list (substring string 0 (match-beginning 0))))
	  string (substring string (match-end 0))))
  (if (string-match inferior-octave-prompt string)
      (setq inferior-octave-receive-in-progress nil))
  (setq inferior-octave-output-string string))

(defun inferior-octave-check-process ()
  (or (inferior-octave-process-live-p)
      (error (substitute-command-keys
              "No inferior octave process running. Type \\[run-octave]"))))

(defun inferior-octave-send-list-and-digest (list)
  "Send LIST to the inferior Octave process and digest the output.
The elements of LIST have to be strings and are sent one by one.  All
output is passed to the filter `inferior-octave-output-digest'."
  (inferior-octave-check-process)
  (let* ((proc inferior-octave-process)
	 (filter (process-filter proc))
	 string)
    (set-process-filter proc 'inferior-octave-output-digest)
    (setq inferior-octave-output-list nil)
    (unwind-protect
	(while (setq string (car list))
	  (setq inferior-octave-output-string nil
		inferior-octave-receive-in-progress t)
	  (comint-send-string proc string)
	  (while inferior-octave-receive-in-progress
	    (accept-process-output proc))
	  (setq list (cdr list)))
      (set-process-filter proc filter))))

(defvar-local inferior-octave-directory-tracker-resync nil)

(defun inferior-octave-directory-tracker (string)
  "Tracks `cd' commands issued to the inferior Octave process.
Use \\[inferior-octave-resync-dirs] to resync if Emacs gets confused."
  (when inferior-octave-directory-tracker-resync
    (or (inferior-octave-resync-dirs 'noerror)
        (setq inferior-octave-directory-tracker-resync nil)))
  (cond
   ((string-match "^[ \t]*cd[ \t;]*$" string)
    (cd "~"))
   ((string-match "^[ \t]*cd[ \t]+\\([^ \t\n;]*\\)[ \t\n;]*" string)
    (condition-case err
        (cd (match-string 1 string))
      (error (setq inferior-octave-directory-tracker-resync t)
             (message "%s: `%s'"
                      (error-message-string err)
                      (match-string 1 string)))))))

(defun inferior-octave-resync-dirs (&optional noerror)
  "Resync the buffer's idea of the current directory.
This command queries the inferior Octave process about its current
directory and makes this the current buffer's default directory."
  (interactive)
  (inferior-octave-send-list-and-digest '("disp (pwd ())\n"))
  (condition-case err
      (progn
        (cd (car inferior-octave-output-list))
        t)
    (error (unless noerror (signal (car err) (cdr err))))))

(defcustom inferior-octave-minimal-columns 80
  "The minimal column width for the inferior Octave process."
  :type 'integer
  :version "24.4")

(defvar inferior-octave-last-column-width nil)

(defun inferior-octave-track-window-width-change ()
  ;; http://thread.gmane.org/gmane.comp.gnu.octave.general/48572 [dead link]
  (let ((width (max inferior-octave-minimal-columns (window-width))))
    (unless (eq inferior-octave-last-column-width width)
      (setq-local inferior-octave-last-column-width width)
      (when (inferior-octave-process-live-p)
        (inferior-octave-send-list-and-digest
         (list (format "putenv ('COLUMNS', '%s');\n" width)))))))


;;; Miscellaneous useful functions

(defun octave-in-comment-p ()
  "Return non-nil if point is inside an Octave comment."
  (nth 4 (syntax-ppss)))

(defun octave-in-string-p ()
  "Return non-nil if point is inside an Octave string."
  (nth 3 (syntax-ppss)))

(defun octave-in-string-or-comment-p ()
  "Return non-nil if point is inside an Octave string or comment."
  (nth 8 (syntax-ppss)))

(defun octave-looking-at-kw (regexp)
  "Like `looking-at', but set `case-fold-search' nil first."
  (let ((case-fold-search nil))
    (looking-at regexp)))

(defun octave-maybe-insert-continuation-string ()
  (declare (obsolete nil "28.1"))
  (unless (or (octave-in-comment-p)
              (save-excursion
                (beginning-of-line)
                (looking-at octave-continuation-regexp)))
    (delete-horizontal-space)
    (insert (concat " " octave-continuation-string))))

(defun octave-completing-read ()
  (let ((def (or (thing-at-point 'symbol)
                 (save-excursion
                   (skip-syntax-backward "-(")
                   (thing-at-point 'symbol)))))
    (completing-read (format-prompt "Function" def)
                     (inferior-octave-completion-table)
                     nil nil nil nil def)))

(defun octave-goto-function-definition (fn)
  "Go to the function definition of FN in current buffer."
  (let ((search
         (lambda (re sub)
           (let ((orig (point)) found)
             (goto-char (point-min))
             (while (and (not found) (re-search-forward re nil t))
               (when (and (equal (match-string sub) fn)
                          (not (nth 8 (syntax-ppss))))
                 (setq found t)))
             (unless found (goto-char orig))
             found))))
    (pcase (and buffer-file-name (file-name-extension buffer-file-name))
      ("cc" (funcall search
                     "\\_<DEFUN\\(?:_DLD\\)?\\s-*(\\s-*\\(\\(?:\\sw\\|\\s_\\)+\\)" 1))
      (_ (funcall search octave-function-header-regexp 3)))))

(defun octave-function-file-p ()
  "Return non-nil if the first token is \"function\".
The value is (START END NAME-START NAME-END) of the function."
  (save-excursion
    (goto-char (point-min))
    (when (equal (funcall smie-forward-token-function) "function")
      (forward-word-strictly -1)
      (let* ((start (point))
             (end (progn (forward-sexp 1) (point)))
             (name (when (progn
                           (goto-char start)
                           (re-search-forward octave-function-header-regexp
                                              end t))
                     (list (match-beginning 3) (match-end 3)))))
        (cons start (cons end name))))))

;; Like forward-comment but stop at non-comment blank
(defun octave-skip-comment-forward (limit)
  (let ((ppss (syntax-ppss)))
    (if (nth 4 ppss)
        (goto-char (nth 8 ppss))
      (goto-char (or (comment-search-forward limit t) (point)))))
  (while (and (< (point) limit) (looking-at-p "\\s<"))
    (forward-comment 1)))

;;; First non-copyright comment block
(defun octave-function-file-comment ()
  "Beginning and end positions of the function file comment."
  (save-excursion
    (goto-char (point-min))
    ;; Copyright block: octave/libinterp/parse-tree/lex.ll around line 1634
    (while (save-excursion
             (when (comment-search-forward (point-max) t)
               (when (eq (char-after) ?\{) ; case of block comment
                 (forward-char 1))
               (skip-syntax-forward "-")
               (let ((case-fold-search t))
                 (looking-at-p "\\(?:copyright\\|author\\)\\_>"))))
      (octave-skip-comment-forward (point-max)))
    (let ((beg (comment-search-forward (point-max) t)))
      (when beg
        (goto-char beg)
        (octave-skip-comment-forward (point-max))
        (list beg (point))))))

(defun octave-sync-function-file-names ()
  "Ensure function name agree with function file name.
See Info node `(octave)Function Files'."
  (interactive)
  (when buffer-file-name
    (pcase-let ((`(,start ,_end ,name-start ,name-end)
                 (octave-function-file-p)))
      (when (and start name-start)
        (let* ((func (buffer-substring name-start name-end))
               (file (file-name-sans-extension
                      (file-name-nondirectory buffer-file-name)))
               (help-form (format-message "\
a: Use function name `%s'
b: Use file name `%s'
q: Don't fix\n" func file))
               (c (unless (equal file func)
                    (save-window-excursion
                      (help-form-show)
                      (read-char-choice
                       "Which name to use? (a/b/q) " '(?a ?b ?q))))))
          (pcase c
            (?a (let ((newname (expand-file-name
                                (concat func (file-name-extension
                                              buffer-file-name t)))))
                  (when (or (not (file-exists-p newname))
                            (yes-or-no-p
                             (format "Target file %s exists; proceed? " newname)))
                    (when (file-exists-p buffer-file-name)
                      (rename-file buffer-file-name newname t))
                    (set-visited-file-name newname))))
            (?b (save-excursion
                  (goto-char name-start)
                  (delete-region name-start name-end)
                  (insert file)))))))))

(defun octave-update-function-file-comment (beg end)
  "Query replace function names in function file comment."
  (interactive
   (progn
     (barf-if-buffer-read-only)
     (if (use-region-p)
         (list (region-beginning) (region-end))
       (or (octave-function-file-comment)
           (error "No function file comment found")))))
  (save-excursion
    (let* ((bounds (or (octave-function-file-p)
                       (error "Not in a function file buffer")))
           (func (if (cddr bounds)
                     (apply #'buffer-substring (cddr bounds))
                   (error "Function name not found")))
           (old-func (progn
                       (goto-char beg)
                       (when (re-search-forward
                              "[=}]\\s-*\\(\\(?:\\sw\\|\\s_\\)+\\)\\_>"
                              (min (line-end-position 4) end)
                              t)
                         (match-string 1))))
           (old-func (read-string (format-prompt "Name to replace" old-func)
                                  nil nil old-func)))
      (if (and func old-func (not (equal func old-func)))
          (perform-replace old-func func 'query
                           nil 'delimited nil nil beg end)
        (message "Function names match")))))

(defface octave-function-comment-block
  '((t (:inherit font-lock-doc-face)))
  "Face used to highlight function comment block.")

(eval-when-compile (require 'texinfo))
;; Undo the effects of texinfo loading tex-mode loading compile.
(declare-function compilation-forget-errors "compile" ())

(defun octave-font-lock-texinfo-comment ()
  (let ((kws
         (eval-when-compile
           (delq nil (mapcar
                      (lambda (kw)
                        (if (numberp (nth 1 kw))
                            `(,(nth 0 kw) ,(nth 1 kw) ,(nth 2 kw) prepend)
                          (message "Ignoring Texinfo highlight: %S" kw)))
                      texinfo-font-lock-keywords)))))
    (font-lock-add-keywords
     nil
     `((,(lambda (limit)
           (while (and (< (point) limit)
                       (search-forward "-*- texinfo -*-" limit t)
                       (octave-in-comment-p))
             (let ((beg (nth 8 (syntax-ppss)))
                   (end (progn
                          (octave-skip-comment-forward (point-max))
                          (point))))
               (put-text-property beg end 'font-lock-multiline t)
               (font-lock-prepend-text-property
                beg end 'face 'octave-function-comment-block)
               (dolist (kw kws)
                 (goto-char beg)
                 (while (re-search-forward (car kw) end 'move)
                   (font-lock-apply-highlight (cdr kw))))))
           nil)))
     'append)))


;;; Indentation

(defun octave-indent-new-comment-line (&optional soft)
  "Break Octave line at point, continuing comment if within one.
Insert `octave-continuation-string' before breaking the line
unless inside a list.  If within a double-quoted string, insert
`octave-string-continuation-marker' instead.  Signal an error if
within a single-quoted string."
  (interactive)
  (funcall comment-line-break-function soft))

(defun octave--indent-new-comment-line (orig &rest args)
  (pcase (syntax-ppss)
    ((app ppss-string-terminator ?\')
     (user-error "Cannot split a single-quoted string"))
    ((app ppss-string-terminator ?\")
     (insert octave-string-continuation-marker))
    ((pred (not ppss-comment-depth))
     (delete-horizontal-space)
     (unless (octave-smie--in-parens-p)
       (insert " " octave-continuation-string))))
  (apply orig args)
  (indent-according-to-mode))

(define-obsolete-function-alias
  'octave-indent-defun 'prog-indent-sexp "24.4")


;;; Motion
(defun octave-next-code-line (&optional arg)
  "Move ARG lines of Octave code forward (backward if ARG is negative).
Skips past all empty and comment lines.  Default for ARG is 1.

On success, return 0.  Otherwise, go as far as possible and return -1."
  (interactive "p")
  (or arg (setq arg 1))
  (beginning-of-line)
  (let ((n 0)
	(inc (if (> arg 0) 1 -1)))
    (while (and (/= arg 0) (= n 0))
      (setq n (forward-line inc))
      (while (and (= n 0)
		  (looking-at "\\s-*\\($\\|\\s<\\)"))
	(setq n (forward-line inc)))
      (setq arg (- arg inc)))
    n))

(defun octave-previous-code-line (&optional arg)
  "Move ARG lines of Octave code backward (forward if ARG is negative).
Skips past all empty and comment lines.  Default for ARG is 1.

On success, return 0.  Otherwise, go as far as possible and return -1."
  (interactive "p")
  (or arg (setq arg 1))
  (octave-next-code-line (- arg)))

(defun octave-beginning-of-line ()
  "Move point to beginning of current Octave line.
If on an empty or comment line, go to the beginning of that line.
Otherwise, move backward to the beginning of the first Octave code line
which is not inside a continuation statement, i.e., which does not
follow a code line ending with `...' or is inside an open
parenthesis list."
  (interactive)
  (beginning-of-line)
  (unless (looking-at "\\s-*\\($\\|\\s<\\)")
    (while (or (when (cadr (syntax-ppss))
                 (goto-char (cadr (syntax-ppss)))
                 (beginning-of-line)
                 t)
               (and (or (looking-at "\\s-*\\($\\|\\s<\\)")
                        (save-excursion
                          (if (zerop (octave-previous-code-line))
                              (looking-at octave-continuation-regexp))))
                    (zerop (forward-line -1)))))))

(defun octave-end-of-line ()
  "Move point to end of current Octave line.
If on an empty or comment line, go to the end of that line.
Otherwise, move forward to the end of the first Octave code line which
does not end with `...' or is inside an open parenthesis list."
  (interactive)
  (end-of-line)
  (unless (save-excursion
            (beginning-of-line)
            (looking-at "\\s-*\\($\\|\\s<\\)"))
    (while (or (when (cadr (syntax-ppss))
                 (condition-case nil
                     (progn
                       (up-list 1)
                       (end-of-line)
                       t)
                   (error nil)))
               (and (save-excursion
                      (beginning-of-line)
                      (or (looking-at "\\s-*\\($\\|\\s<\\)")
                          (looking-at octave-continuation-regexp)))
                    (zerop (forward-line 1)))))
    (end-of-line)))

(defun octave-mark-block ()
  "Put point at the beginning of this Octave block, mark at the end.
The block marked is the one that contains point or follows point."
  (interactive)
  (if (and (looking-at "\\sw\\|\\s_")
           (looking-back "\\sw\\|\\s_" (1- (point))))
      (skip-syntax-forward "w_"))
  (unless (or (looking-at "\\s(")
              (save-excursion
                (let* ((token (funcall smie-forward-token-function))
                       (level (assoc token smie-grammar)))
                  (and level (not (numberp (cadr level)))))))
    (backward-up-list 1))
  (mark-sexp))

(defun octave-beginning-of-defun (&optional arg)
  "Octave-specific `beginning-of-defun-function' (which see)."
  (or arg (setq arg 1))
  ;; Move out of strings or comments.
  (when (octave-in-string-or-comment-p)
    (goto-char (octave-in-string-or-comment-p)))
  (letrec ((orig (point))
           (toplevel (lambda (pos)
                       (condition-case nil
                           (progn
                             (backward-up-list 1)
                             (funcall toplevel (point)))
                         (scan-error pos)))))
    (goto-char (funcall toplevel (point)))
    (when (and (> arg 0) (/= orig (point)))
      (setq arg (1- arg)))
    (forward-sexp (- arg))
    (and (< arg 0) (forward-sexp -1))
    (/= orig (point))))

(defun octave-fill-paragraph (&optional _arg)
  "Fill paragraph of Octave code, handling Octave comments."
  ;; FIXME: difference with generic fill-paragraph:
  ;; - code lines are only split, never joined.
  ;; - \n that end comments are never removed.
  ;; - insert continuation marker when splitting code lines.
  (interactive "P")
  (save-excursion
    (let ((end (progn (forward-paragraph) (copy-marker (point) t)))
          (beg (progn
                 (forward-paragraph -1)
                 (skip-chars-forward " \t\n")
                 (beginning-of-line)
                 (point)))
          (cfc (current-fill-column))
          comment-prefix)
      (goto-char beg)
      (while (< (point) end)
        (condition-case nil
            (indent-according-to-mode)
          (error nil))
        (move-to-column cfc)
        ;; First check whether we need to combine non-empty comment lines
        (if (and (< (current-column) cfc)
                 (octave-in-comment-p)
                 (not (save-excursion
                        (beginning-of-line)
                        (looking-at "^\\s-*\\s<+\\s-*$"))))
            ;; This is a nonempty comment line which does not extend
            ;; past the fill column.  If it is followed by a nonempty
            ;; comment line with the same comment prefix, try to
            ;; combine them, and repeat this until either we reach the
            ;; fill-column or there is nothing more to combine.
            (progn
              ;; Get the comment prefix
              (save-excursion
                (beginning-of-line)
                (while (and (re-search-forward "\\s<+")
                            (not (octave-in-comment-p))))
                (setq comment-prefix (match-string 0)))
              ;; And keep combining ...
              (while (and (< (current-column) cfc)
                          (save-excursion
                            (forward-line 1)
                            (and (looking-at
                                  (concat "^\\s-*"
                                          comment-prefix
                                          "\\S<"))
                                 (not (looking-at
                                       (concat "^\\s-*"
                                               comment-prefix
                                               "\\s-*$"))))))
                (delete-char 1)
                (re-search-forward comment-prefix)
                (delete-region (match-beginning 0) (match-end 0))
                (fixup-whitespace)
                (move-to-column cfc))))
        ;; We might also try to combine continued code lines>  Perhaps
        ;; some other time ...
        (skip-chars-forward "^ \t\n")
        (delete-horizontal-space)
        (if (or (< (current-column) cfc)
                (and (= (current-column) cfc) (eolp)))
            (forward-line 1)
          (if (not (eolp)) (insert " "))
          (or (funcall normal-auto-fill-function)
              (forward-line 1))))
      t)))

(defun octave-completion-at-point ()
  "Find the text to complete and the corresponding table."
  (let* ((beg (save-excursion (skip-syntax-backward "w_") (point)))
         (end (point)))
    (if (< beg (point))
        ;; Extend region past point, if applicable.
        (save-excursion (skip-syntax-forward "w_")
                        (setq end (point))))
    (when (> end beg)
      (list beg end (or (and (inferior-octave-process-live-p)
                             (inferior-octave-completion-table))
                        octave-reserved-words)))))

(defun octave-add-log-current-defun ()
  "A function for `add-log-current-defun-function' (which see)."
  (save-excursion
    (end-of-line)
    (and (beginning-of-defun)
         (re-search-forward octave-function-header-regexp
                            (line-end-position) t)
         (match-string 3))))


;;; Electric characters && friends
(define-skeleton octave-insert-defun
  "Insert an Octave function skeleton.
Prompt for the function's name, arguments and return values (to be
entered without parens)."
  (let* ((defname (file-name-sans-extension (buffer-name)))
         (name (read-string (format-prompt "Function name" defname)
                            nil nil defname))
         (args (read-string "Arguments: "))
         (vals (read-string "Return values: ")))
    (format "%s%s (%s)"
            (cond
             ((string-equal vals "") vals)
             ((string-match "[ ,]" vals) (concat "[" vals "] = "))
             (t (concat vals " = ")))
            name
            args))
  \n octave-block-comment-start "usage: " str \n
  octave-block-comment-start '(delete-horizontal-space) \n
  octave-block-comment-start '(delete-horizontal-space) \n
  "function " > str \n
  _ \n
  "endfunction" > \n)

;;; Communication with the inferior Octave process
(defun octave-kill-process ()
  "Kill inferior Octave process and its buffer."
  (interactive)
  (when (and (buffer-live-p (get-buffer inferior-octave-buffer))
             (or (yes-or-no-p (format "Kill %S and its buffer? "
                                      inferior-octave-process))
                 (user-error "Aborted")))
    (when (inferior-octave-process-live-p)
      (set-process-query-on-exit-flag inferior-octave-process nil)
      (process-send-string inferior-octave-process "quit;\n")
      (accept-process-output inferior-octave-process))
    (kill-buffer inferior-octave-buffer)))

(defun octave-show-process-buffer ()
  "Make sure that `inferior-octave-buffer' is displayed."
  (interactive)
  (if (get-buffer inferior-octave-buffer)
      (display-buffer inferior-octave-buffer)
    (message "No buffer named %s" inferior-octave-buffer)))

(defun octave-hide-process-buffer ()
  "Delete all windows that display `inferior-octave-buffer'."
  (interactive)
  (if (get-buffer inferior-octave-buffer)
      (delete-windows-on inferior-octave-buffer)
    (message "No buffer named %s" inferior-octave-buffer)))

(defun octave-source-file (file)
  "Execute FILE in the inferior Octave process.
This is done using Octave's source function.  FILE defaults to
current buffer file unless called with a prefix arg \\[universal-argument]."
  (interactive (list (or (and (not current-prefix-arg) buffer-file-name)
                         (read-file-name "File: " nil nil t))))
  (or (stringp file)
      (signal 'wrong-type-argument (list 'stringp file)))
  (inferior-octave t)
  (with-current-buffer inferior-octave-buffer
    (comint-send-string inferior-octave-process
                        (format "source '%s'\n" file))))

(defun octave-send-region (beg end)
  "Send current region to the inferior Octave process."
  (interactive "r")
  (inferior-octave t)
  (let ((proc inferior-octave-process)
        (string (buffer-substring-no-properties beg end)))
    (with-current-buffer inferior-octave-buffer
      ;; https://lists.gnu.org/r/emacs-devel/2013-10/msg00095.html
      (compilation-forget-errors)
      (insert-before-markers string "\n")
      (comint-send-string proc (concat string "\n")))
    (deactivate-mark))
  (if octave-send-show-buffer
      (display-buffer inferior-octave-buffer)))

(defun octave-send-buffer ()
  "Send current buffer to the inferior Octave process."
  (interactive)
  (octave-send-region (point-min) (point-max)))

(defun octave-send-block ()
  "Send current Octave block to the inferior Octave process."
  (interactive)
  (save-excursion
    (octave-mark-block)
    (octave-send-region (point) (mark))))

(defun octave-send-defun ()
  "Send current Octave function to the inferior Octave process."
  (interactive)
  (save-excursion
    (mark-defun)
    (octave-send-region (point) (mark))))

(defun octave-send-line (&optional arg)
  "Send current Octave code line to the inferior Octave process.
With positive prefix ARG, send that many lines.
If `octave-send-line-auto-forward' is non-nil, go to the next unsent
code line."
  (interactive "P")
  (or arg (setq arg 1))
  (if (> arg 0)
      (let (beg end)
	(beginning-of-line)
	(setq beg (point))
	(octave-next-code-line (- arg 1))
	(end-of-line)
	(setq end (point))
	(if octave-send-line-auto-forward
	    (octave-next-code-line 1))
	(octave-send-region beg end))))

(defun octave-eval-print-last-sexp ()
  "Evaluate Octave sexp before point and print value into current buffer."
  (interactive)
  (inferior-octave t)
  (let ((standard-output (current-buffer))
	(print-escape-newlines nil)
	(opoint (point)))
    (terpri)
    (prin1
     (save-excursion
       (forward-sexp -1)
       (inferior-octave-send-list-and-digest
	(list (concat (buffer-substring-no-properties (point) opoint)
		      "\n")))
       (mapconcat 'identity inferior-octave-output-list "\n")))
    (terpri)))



(defcustom octave-eldoc-message-style 'auto
  "Octave eldoc message style: auto, oneline, multiline."
  :type '(choice (const :tag "Automatic" auto)
                 (const :tag "One Line" oneline)
                 (const :tag "Multi Line" multiline))
  :version "24.4")

;; (FN SIGNATURE1 SIGNATURE2 ...)
(defvar octave-eldoc-cache nil)

(defun octave-eldoc-function-signatures (fn)
  (unless (equal fn (car octave-eldoc-cache))
    (while-no-input
      (inferior-octave-send-list-and-digest
       (list (format "print_usage ('%s');\n" fn))))
    (let (result)
      (dolist (line inferior-octave-output-list)
        ;; The help output has changed a few times in GNU Octave.
        ;; Earlier versions output "usage: " before the function signature.
        ;; After deprecating the usage function, and up until GNU Octave 4.0.3,
        ;; the output looks like this:
        ;; -- Mapping Function: abs (Z).
        ;; After GNU Octave 4.2.0, the output is less verbose and it looks like
        ;; this:
        ;; -- abs (Z)
        ;; The following regexp matches these three formats.
        ;; The "usage: " alternative matches the symbol, because a call to
        ;; print_usage with a non-existent function (e.g., print_usage ('A'))
        ;; would output:
        ;; error: print_usage: 'A' not found
        ;; and we wouldn't like to match anything in this case.
        ;; See bug #36459.
        (when (string-match
               "\\s-*\\(?:--[^:]+:\\|\\_<usage:\\|--\\)\\s-*\\(.*\\)$"
               line)
          (push (match-string 1 line) result)))
      (setq octave-eldoc-cache
            (cons (substring-no-properties fn)
                  (nreverse result)))))
  (cdr octave-eldoc-cache))

(defun octave-eldoc-function (&rest _ignored)
  "A function for `eldoc-documentation-functions' (which see)."
  (when (inferior-octave-process-live-p)
    (let* ((ppss (syntax-ppss))
           (paren-pos (cadr ppss))
           (fn (save-excursion
                 (if (and paren-pos
                          ;; PAREN-POS must be after the prompt.
                          (or (not (eq (get-buffer-process (current-buffer))
                                       inferior-octave-process))
                              (< (process-mark inferior-octave-process)
                                 paren-pos))
                          (eq (char-after paren-pos) ?\())
                     (goto-char paren-pos)
                   (setq paren-pos nil))
                 (when (or (< (skip-syntax-backward "-") 0) paren-pos)
                   (thing-at-point 'symbol))))
           (sigs (and fn (octave-eldoc-function-signatures fn)))
           (oneline (mapconcat 'identity sigs
                               (propertize " | " 'face 'warning)))
           (multiline (mapconcat (lambda (s) (concat "-- " s)) sigs "\n")))
      ;;
      ;; Return the value according to style.
      (pcase octave-eldoc-message-style
        ('auto (if (< (length oneline) (window-width (minibuffer-window)))
                   oneline
                 multiline))
        ('oneline oneline)
        ('multiline multiline)))))

(defcustom octave-help-buffer "*Octave Help*"
  "Buffer name for `octave-help'."
  :type 'string
  :version "24.4")

;; Used in a mode derived from help-mode.
(declare-function help-button-action "help-mode" (button))

(define-button-type 'octave-help-file
  'follow-link t
  'action #'help-button-action
  'help-function 'octave-find-definition)

(define-button-type 'octave-help-function
  'follow-link t
  'action (lambda (b) (octave-help (button-label b))))

(defvar octave-help-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map "\M-."  'octave-find-definition)
    (define-key map "\C-hd" 'octave-help)
    (define-key map "\C-ha" 'octave-lookfor)
    map))

(define-derived-mode octave-help-mode help-mode "OctHelp"
  "Major mode for displaying Octave documentation."
  :abbrev-table nil
  :syntax-table octave-mode-syntax-table
  (eval-and-compile (require 'help-mode))
  ;; Don't highlight `EXAMPLE' as elisp symbols by using a regexp that
  ;; can never match.
  (setq-local help-xref-symbol-regexp regexp-unmatchable))

(defun octave-help (fn)
  "Display the documentation of FN."
  (interactive (list (octave-completing-read)))
  (inferior-octave-send-list-and-digest
   (list (format "help ('%s');\n" fn)))
  (let ((lines inferior-octave-output-list)
        (inhibit-read-only t))
    (when (string-match "error: \\(.*\\)$" (car lines))
      (error "%s" (match-string 1 (car lines))))
    (with-help-window octave-help-buffer
      (princ (mapconcat 'identity lines "\n"))
      (with-current-buffer octave-help-buffer
        ;; Bound to t so that `help-buffer' returns current buffer for
        ;; `help-setup-xref'.
        (let ((help-xref-following t))
          (help-setup-xref (list 'octave-help fn)
                           (called-interactively-p 'interactive)))
        ;; Note: can be turned off by suppress_verbose_help_message.
        ;;
        ;; Remove boring trailing text: Additional help for built-in functions
        ;; and operators ...
        (goto-char (point-max))
        (when (search-backward "\n\n\n" nil t)
          (goto-char (match-beginning 0))
          (delete-region (point) (point-max)))
        ;; File name highlight
        (goto-char (point-min))
        (when (re-search-forward "from the file \\(.*\\)$"
                                 (line-end-position)
                                 t)
          (let* ((file (match-string 1))
                 (dir (file-name-directory
                       (directory-file-name (file-name-directory file)))))
            (replace-match "" nil nil nil 1)
            (insert (substitute-quotes "`"))
            ;; Include the parent directory which may be regarded as
            ;; the category for the FN.
            (help-insert-xref-button (file-relative-name file dir)
                                     'octave-help-file fn)
            (insert (substitute-quotes "'"))))
        ;; Make 'See also' clickable.
        (with-syntax-table octave-mode-syntax-table
          (when (re-search-forward "^\\s-*See also:" nil t)
            (let ((end (save-excursion (re-search-forward "^\\s-*$" nil t))))
              (while (re-search-forward
                      "\\s-*\\([^,\n]+?\\)\\s-*\\(?:[,]\\|[.]?$\\)" end t)
                (make-text-button (match-beginning 1) (match-end 1)
                                  :type 'octave-help-function)))))
        (octave-help-mode)))))

(defun octave-lookfor (str &optional all)
  "Search for the string STR in all function help strings.
If ALL is non-nil search the entire help string else only search the first
sentence."
  (interactive "sSearch for: \nP")
  (inferior-octave-send-list-and-digest
   (list (format "lookfor (%s'%s');\n"
                 (if all "'-all', " "")
                 str)))
  (let ((lines inferior-octave-output-list))
    (when (and (stringp (car lines))
               (string-match "error: \\(.*\\)$" (car lines)))
      (error "%s" (match-string 1 (car lines))))
    (with-help-window octave-help-buffer
      (with-current-buffer octave-help-buffer
        (if lines
            (insert (mapconcat 'identity lines "\n"))
          (insert (format "Nothing found for \"%s\".\n" str)))
        ;; Bound to t so that `help-buffer' returns current buffer for
        ;; `help-setup-xref'.
        (let ((help-xref-following t))
          (help-setup-xref (list 'octave-lookfor str all)
                           (called-interactively-p 'interactive)))
        (goto-char (point-min))
        (when lines
          (while (re-search-forward "^\\([^[:blank:]]+\\) " nil 'noerror)
            (make-text-button (match-beginning 1) (match-end 1)
                              :type 'octave-help-function)))
        (unless all
          (goto-char (point-max))
          (insert "\nRetry with ")
          (insert-text-button "'-all'"
                              'follow-link t
                              'action (lambda (_b)
                                        (octave-lookfor str '-all)))
          (insert ".\n"))
        (octave-help-mode)))))

(defcustom octave-source-directories nil
  "A list of directories for Octave sources.
If the environment variable OCTAVE_SRCDIR is set, it is searched first."
  :type '(repeat directory)
  :version "24.4")

(defun octave-source-directories ()
  (let ((srcdir (or (and inferior-octave-process
                         (process-get inferior-octave-process 'octave-srcdir))
                    (getenv "OCTAVE_SRCDIR"))))
    (if srcdir
        (cons srcdir octave-source-directories)
      octave-source-directories)))

(defvar octave-find-definition-filename-function
  #'octave-find-definition-default-filename)

(defun octave-find-definition-default-filename (name)
  "Default value for `octave-find-definition-filename-function'."
  (pcase (file-name-extension name)
    ("oct"
     (octave-find-definition-default-filename
      (concat "libinterp/dldfcn/"
              (file-name-sans-extension (file-name-nondirectory name))
              ".cc")))
    ("cc"
     (let ((file (or (locate-file name (octave-source-directories))
                     (locate-file (file-name-nondirectory name)
                                  (octave-source-directories)))))
       (or (and file (file-exists-p file))
           (error "File `%s' not found" name))
       file))
    ("mex"
     (if (yes-or-no-p (format-message "File `%s' may be binary; open? "
				      (file-name-nondirectory name)))
         name
       (user-error "Aborted")))
    (_ name)))

(declare-function xref-push-marker-stack "xref" (&optional m))

(defun octave-find-definition (fn)
  "Find the definition of FN.
Functions implemented in C++ can be found if
variable `octave-source-directories' is set correctly."
  (interactive (list (octave-completing-read)))
  (require 'xref)
  (let ((orig (point)))
    (if (and (derived-mode-p 'octave-mode)
             (octave-goto-function-definition fn))
        (xref-push-marker-stack (copy-marker orig))
      (inferior-octave-send-list-and-digest
       ;; help NAME is more verbose
       (list (format "\
if iskeyword('%s') disp('`%s'' is a keyword') else which('%s') endif\n"
                     fn fn fn)))
      (let (line file)
        ;; Skip garbage lines such as
        ;;     warning: fmincg.m: possible Matlab-style ....
        (while (and (not file) (consp inferior-octave-output-list))
          (setq line (pop inferior-octave-output-list))
          (when (string-match "from the file \\(.*\\)$" line)
            (setq file (match-string 1 line))))
        (if (not file)
            (user-error "%s" (or line (format-message "`%s' not found" fn)))
          (xref-push-marker-stack)
          (setq file (funcall octave-find-definition-filename-function file))
          (when file
            (find-file file)
            (octave-goto-function-definition fn)))))))

(provide 'octave)
;;; octave.el ends here
