;;; factor-mode.el --- Major mode for editing Factor programs. -*- lexical-binding: t -*-

;; Copyright (C) 2013 Erik Charlebois
;; Copyright (C) 2008, 2009, 2010 Jose Antonio Ortega Ruiz
;; See https://factorcode.org/license.txt for BSD license.

;; Maintainer: Erik Charlebois <erikcharlebois@gmail.com>
;; Author: Jose Antonio Ortega Ruiz <jao@gnu.org>
;; Keywords: languages, factor
;; Start date: Tue Dec 02, 2008 21:32

;;; Commentary:

;; A major mode for editing Factor programs. It provides indenting and
;; font-lock support.


;;; Code:

(require 'thingatpt)
(require 'font-lock)
(require 'ring)
(require 'fuel-base)
(require 'factor-smie)

;;; Customization:

;;;###autoload
(defgroup factor nil
  "Major mode for Factor source code."
  :group 'languages)

(defcustom factor-cycling-no-ask nil
  "Whether to never create source/doc/tests file when cycling."
  :type 'boolean
  :group 'factor)

(defcustom factor-cycle-always-ask-p t
  "Whether to always ask for file creation when cycling to a
source/docs/tests file. When set to false, you'll be asked only once."
  :type 'boolean
  :group 'factor)

(defcustom factor-comment-column 32
  "Indentation column of comments."
  :type 'integer
  :safe 'integerp
  :group 'factor)

(defcustom factor-mode-use-fuel t
  "Whether to use the full FUEL facilities in factor mode.

Set this variable to nil if you just want to use Emacs as the
external editor of your Factor environment, e.g., by putting
these lines in your .emacs:

  (add-to-list 'load-path \"/path/to/factor/misc/fuel\")
  (setq factor-mode-use-fuel nil)
  (require 'factor-mode)
"
  :type 'boolean
  :group 'factor)


;;; Faces:

;;;###autoload
(defgroup factor-faces nil
  "Faces used by factor-mode."
  :group 'factor
  :group 'faces)

(defface factor-font-lock-constructor '((t (:inherit font-lock-type-face)))
  "Factor for constructor words."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-constant '((t (:inherit font-lock-constant-face)))
  "Face for constant and literal values."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-number '((t (:inherit font-lock-constant-face)))
  "Face for integer and floating-point constants."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-ratio '((t (:inherit font-lock-constant-face)))
  "Face for ratio constants."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-parsing-word '((t (:inherit font-lock-keyword-face)))
  "parsing words"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-setter-word
  '((t (:inherit font-lock-function-name-face)))
  "setter words (>>foo)"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-getter-word
  '((t (:inherit font-lock-function-name-face)))
  "getter words (foo>>)"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-string '((t (:inherit font-lock-string-face)))
  "strings"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-symbol '((t (:inherit font-lock-variable-name-face)))
  "name of symbol being defined"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-type-name '((t (:inherit font-lock-type-face)))
  "type names"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-vocabulary-name
  '((t (:inherit font-lock-constant-face)))
  "vocabulary names"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-word
  '((t (:inherit font-lock-function-name-face)))
  "Face for the word, generic or method being defined."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-invalid-syntax
  '((t (:inherit font-lock-warning-face)))
  "syntactically invalid constructs"
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-comment '((t (:inherit font-lock-comment-face)))
  "Face for Factor comments."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-stack-effect '((t :inherit font-lock-comment-face))
  "Face for Factor stack effect declarations."
  :group 'factor-faces
  :group 'faces)

(defface factor-font-lock-type-in-stack-effect '((t :inherit font-lock-comment-face
                                                    :bold t))
  "Face for Factor types in stack effect declarations."
  :group 'factor-faces
  :group 'faces)


;;; Thing-at-point:

(defun factor-beginning-of-symbol ()
  "Move point to the beginning of the current symbol."
  (skip-syntax-backward "w_()\""))

(defun factor-end-of-symbol ()
  "Move point to the end of the current symbol."
  (skip-syntax-forward "w_()\""))

(put 'factor-symbol 'end-op 'factor-end-of-symbol)
(put 'factor-symbol 'beginning-op 'factor-beginning-of-symbol)

(defun factor-symbol-at-point ()
  (let ((thing (thing-at-point 'factor-symbol t)))
    (and (> (length thing) 0) thing)))


;;; Regexps galore:

;; Utility regexp used by other regexps to match a Factor symbol name
(setq-local symbol-nc "\\(?:\\sw\\|\\s_\\|`\\|\"\\|\\s(\\|\\s)\\|\\s\\\\)+")
(setq-local symbol (format "\\(%s\\)" symbol-nc))
(setq-local c-symbol-nc "\\(?:\\sw\\|\\s_\\|\\[\\|\\]\\)+")
(setq-local c-symbol (format "\\(%s\\)" c-symbol-nc))
(setq-local ws+ "[ \n\t]+")
(setq-local symbols-to-semicolon "\\([^;\t]*\\)\\(;\\)")

(defun one-symbol (content)
  (concat "\\_<\\(" content "\\)\\_>"))

(defun syntax-begin (content)
  (one-symbol (concat (regexp-opt content) ":")))

(defun syntax-and-1-symbol (prefixes)
  (concat (syntax-begin prefixes) ws+ symbol))

(defun syntax-and-2-symbols (prefixes)
  (concat (syntax-and-1-symbol prefixes) ws+ symbol))

;; Used to font-lock stack effect declarations with may be nested.
(defun factor-match-brackets (limit)
  (let ((start (point)))
    (when (re-search-forward "[ \n]([ \n]" limit t)
      (backward-char 2)
      (let ((bracket-start (point)))
        (when (condition-case nil
                  (progn (forward-sexp) 't)
                ('scan-error nil))
          (let ((bracket-stop (point)))
            (goto-char bracket-start)
            (re-search-forward "\\(.\\|\n\\)+" bracket-stop 'mv)))))))

;; Excludes parsing words that are handled by other regexps
(defconst factor-parsing-words
  '(":" "::" ";" ":>" "&:" "<<" "<PRIVATE" ">>"
    "ABOUT:" "ARTICLE:"
    "B"
    "CONSULT:" "call-next-method"
    "FOREIGN-ATOMIC-TYPE:" "FOREIGN-ENUM-TYPE:" "FOREIGN-RECORD-TYPE:" "FUNCTION-ALIAS:"
    ";FUNCTOR>"
    "GIR:"
    "initial:" "IMPLEMENT-STRUCTS:"
    "MATH:"
    "METHOD:"
    "PRIVATE>" "PROTOCOL:"
    "read-only"
    "STRING:" "SYNTAX:"
    "VARIANT:"))

(defconst factor-parsing-words-regex
  (format "\\(?:^\\| \\)%s" (regexp-opt factor-parsing-words 'symbols)))

(defconst factor-constant-words
  '("f" "t"))

(defconst factor-constant-words-regex
  (regexp-opt factor-constant-words 'symbols))

(defconst factor-bracer-words
  '("B" "BV" "C" "CS" "HEX" "H" "HS" "S" "T" "V" "W" "flags"))

(defconst factor-brace-words-regex
  (format "%s{" (regexp-opt factor-bracer-words t)))

(defconst factor-declaration-words
  '("deprecated"
    "final"
    "flushable"
    "foldable"
    "inline"
    "parsing"
    "recursive"
    "delimiter"))

(defconst factor-declaration-words-regex
  (regexp-opt factor-declaration-words 'symbols))

(defconst factor-integer-regex
  (one-symbol "-?\\(?:0[xob][0-9a-fA-F][0-9a-fA-F,]*\\|[0-9][0-9,]*\\)"))

(defconst factor-raw-float-regex
  "[0-9]*\\.[0-9]*\\([eEpP][+-]?[0-9]+\\)?")

(defconst factor-float-regex
  (format "\\_<-?%s\\_>" factor-raw-float-regex))

(defconst factor-number-regex
  (format "\\([0-9]+\\|%s\\)" factor-raw-float-regex))

(defconst factor-ratio-regex
  (format "\\_<[+-]?%s/-?%s\\_>" factor-number-regex factor-number-regex))

(defconst factor-bad-string-regex
  "\\_<\"[^>]\\([^\"\n]\\|\\\\\"\\)*\n")

(defconst factor-word-definition-regex
  (concat
   (one-symbol (regexp-opt
                '(":" "::" "GENERIC:" "GENERIC#:" "DEFER:" "HOOK:"
                  "IDENTITY-MEMO:" "MACRO:" "MACRO::" "MATH:" "MEMO:" "MEMO::"
                  "POSTPONE:" "PRIMITIVE:" "SYNTAX:" "TYPED:" "TYPED::")))
   ws+ symbol))

(defconst factor-method-definition-regex
  (syntax-and-2-symbols '("M" "M:" "BEFORE" "AFTER")))

;; [parsing-word] [vocab-word]
(defconst factor-vocab-ref-regex
  (syntax-and-1-symbol '("IN" "USE" "QUALIFIED")))

(defconst factor-using-lines-regex
  (concat (syntax-begin '("USING")) ws+ symbols-to-semicolon))

;; [parsing-word] [symbol-word]
(defconst factor-symbol-definition-regex
  (syntax-and-1-symbol
   '("&" "CONSTANT" "DESTRUCTOR" "EBNF" "FORGET" "FUNCTOR"
     "GAME" "GLSL-PROGRAM" "GLSL-SHADER"
     "HELP" "LIBRARY" "MAIN" "MAIN-WINDOW" "SLOT" "STRING"
     "SYMBOL" "VAR")))

;; [parsing-word] [symbol-word]* ;
(defconst factor-symbols-lines-regex
  (concat (syntax-begin '("SYMBOLS")) ws+ symbols-to-semicolon))

(defconst factor-types-lines-regex
  (concat
   (syntax-begin '("INTERSECTION" "SINGLETONS" "SPECIALIZED-ARRAYS"))
   ws+ symbols-to-semicolon))

;; [parsing-word] [type-word]
(defconst factor-type-definition-regex
  (syntax-and-1-symbol
   '("COM-INTERFACE" "C-TYPE" "MIXIN"
     "GLSL-SHADER-FILE"
     "SINGLETON" "SPECIALIZED-ARRAY" "SPECIALIZED-VECTOR"
     "TUPLE-ARRAY")))

(defconst factor-constructor-regex
  (one-symbol "<[^ >]+>"))

(defconst factor-getter-regex
  (one-symbol (concat symbol-nc ">>")))

(defconst factor-setter-regex
  (one-symbol (format ">>%s\\|%s<<" symbol-nc symbol-nc)))

(defconst factor-stack-effect-regex
  "\\( ( [^)]* )\\)\\|\\( (( [^)]* ))\\)")

(defconst factor-use-line-regex "^USE: +\\(.*\\)$")

(defconst factor-current-vocab-regex "^IN: +\\([^ \r\n\f]+\\)")

(defconst factor-sub-vocab-regex "^<\\([^ \n]+\\) *$")

(defconst factor-definition-start-regex
  (format "^\\(%s:\\) " (regexp-opt (append factor-no-indent-def-starts
                                            factor-indent-def-starts))))

(defconst factor-single-liner-regex
  (regexp-opt '("ABOUT:"
                "ALIAS:"
                "CONSTANT:" "C-GLOBAL:" "C-TYPE:"
                "DEFER:" "DESTRUCTOR:"
                "FORGET:"
                "GAME:" "GENERIC:" "GENERIC#:"
                "HOOK:"
                "IN:" "INSTANCE:"
                "LIBRARY:"
                "MAIN:" "MATH:" "MIXIN:"
                "NAN:"
                "POSTPONE:" "PRIVATE>" "<PRIVATE"
                "QUALIFIED-WITH:" "QUALIFIED:"
                "RENAME:"
                "SINGLETON:" "SLOT:" "SPECIALIZED-ARRAY:"
                "TYPEDEF:"
                "REUSE:" "USE:")))

(defconst factor-begin-of-def-regex
  (format "^USING: \\|\\(%s\\)\\|\\(^%s .*\\)"
          factor-definition-start-regex
          factor-single-liner-regex))

(defconst factor-definition-end-regex
  (format "\\(^\\| +\\);\\( *%s\\)*\\($\\| +\\)"
          factor-declaration-words-regex))

(defconst factor-end-of-def-regex
  (format "^.*%s\\|^%s .*"
          factor-definition-end-regex
          factor-single-liner-regex))

(defconst factor-word-signature-regex
  (format ":[^ ]* \\([^ ]+\\)\\(%s\\)*" factor-stack-effect-regex))

(defconst factor-defun-signature-regex
  (format "\\(%s\\|%s\\)"
          factor-word-signature-regex
          "M[^:]*: [^ ]+ [^ ]+"))

(defconst factor-typedef-regex
  (syntax-and-2-symbols '("TYPEDEF" "INSTANCE")))

(defconst factor-rename-regex
  (concat (syntax-and-2-symbols '("RENAME")) ws+ "\\(=>\\)" ws+ symbol))

(defconst factor-from/exclude-regex
  (concat (syntax-begin '("FROM" "EXCLUDE")) ws+
          symbol ws+
          "\\(=>\\)" ws+ symbols-to-semicolon))

(defconst factor-predicate-regex
  (concat (syntax-begin '("PREDICATE")) ws+ symbol ws+ "\\(<\\)" ws+ symbol))

(defconst factor-alien-function-regex
  (concat (syntax-begin '("CALLBACK"
                          "FUNCTION"
                          "GL-CALLBACK"
                          "GL-FUNCTION"
                          "X-FUNCTION"))
          ws+ symbol
          ws+ symbol ws+))

;; Regexp from hell that puts every type name in the first group,
;; names and brackets in the second and third.
(defconst factor-function-params-regex
  (format "\\(?:%s%s\\(%s,?\\(?:%s)\\)?\\)\\|\\([()]\\)\\)" c-symbol ws+ c-symbol-nc ws+))

(defconst factor-function-alias-regex
  (concat (syntax-begin '("FUNCTION-ALIAS"))
          ws+ symbol
          ws+ symbol
          ws+ symbol ws+))

(defconst factor-group-name-to-face
  #s(hash-table test equal data
                ("C" 'factor-font-lock-comment
                 "CO" 'factor-font-lock-constructor
                 "CT" 'factor-font-lock-constant
                 "P" 'factor-font-lock-parsing-word
                 "V" 'factor-font-lock-vocabulary-name
                 "T" 'factor-font-lock-type-name
                 "N" 'factor-font-lock-number
                 "W" 'factor-font-lock-word)))

(defun factor-group-name-to-face (group-name)
  (gethash group-name factor-group-name-to-face))

(defun factor-groups-to-font-lock (groups)
  (let ((i 0))
    (mapcar (lambda (x)
              (setq i (1+ i))
              (list i (factor-group-name-to-face x)))
            groups)))

(defun factor-syntax (regex groups)
  (append (list regex) (factor-groups-to-font-lock groups)))


;;; Font lock:

(defconst factor-font-lock-keywords
  `(
    ,(factor-syntax factor-brace-words-regex '("P"))
    ,(factor-syntax factor-vocab-ref-regex '("P" "V"))
    ,(factor-syntax factor-using-lines-regex '("P" "V" "P"))
    ,(factor-syntax factor-symbols-lines-regex '("P" "W" "P"))
    ,(factor-syntax factor-from/exclude-regex '("P" "V" "P" "W" "P"))
    ,(factor-syntax (syntax-and-2-symbols '("C")) '("P" "W" "T"))
    ,(factor-syntax factor-symbol-definition-regex '("P" "W"))
    ,(factor-syntax factor-typedef-regex '("P" "T" "T"))
    ,(factor-syntax (syntax-and-2-symbols '("C-GLOBAL")) '("P" "T" "W"))
    ,(factor-syntax (syntax-and-2-symbols '("QUALIFIED-WITH")) '("P" "V" "W"))
    ,(factor-syntax factor-rename-regex '("P" "W" "V" "P" "W"))
    ,(factor-syntax factor-declaration-words-regex '("C"))
    ,(factor-syntax factor-word-definition-regex '("P" "W"))
    ,(factor-syntax (syntax-and-2-symbols '("ALIAS")) '("P" "W" "W"))
    ,(factor-syntax (syntax-and-2-symbols '("HINTS" "LOG")) '("P" "W" ""))
    ,(factor-syntax (syntax-and-1-symbol '("ALIEN" "CHAR" "COLOR" "NAN" "HEXCOLOR")) '("P" "CT"))
    ,(factor-syntax factor-types-lines-regex '("P" "T"))

    (,factor-float-regex . 'factor-font-lock-number)
    (,factor-ratio-regex . 'factor-font-lock-ratio)
    ,(factor-syntax factor-type-definition-regex '("P" "T"))
    ,(factor-syntax factor-method-definition-regex '("P" "T" "W"))

    ;; Highlights tuple and struct definitions. The TUPLE/STRUCT
    ;; parsing word, class name and optional parent classes are
    ;; matched in three groups. Then the text up until the end of the
    ;; definition that is terminated with ";" is searched for words
    ;; that are slot names which are highlighted with the face
    ;; factor-font-lock-symbol.
    (,(format
       "\\(%s:\\)[ \n]+%s\\(?:[ \n]+\\(<\\)[ \n]+%s\\)?"
       (regexp-opt '("BUILTIN"
                     "ENUM"
                     "ERROR"
                     "PROTOCOL"
                     "STRUCT"
                     "TUPLE"
                     "UNIFORM-TUPLE"
                     "UNION"
                     "UNION-STRUCT"
                     "VERTEX-FORMAT"))
       symbol
       symbol)
     (1 'factor-font-lock-parsing-word)
     (2 'factor-font-lock-type-name)
     (3 'factor-font-lock-parsing-word nil t)
     (4 'factor-font-lock-type-name nil t)
     ;; This allows three different slot styles:
     ;; 1) foo 2) { foo initial: 123 } 3) { foo initial: { 123 } }
     (,(format
        "{%s%s[^}]+}%s}\\|{%s%s[^}]+}\\|%s"
        ws+ symbol ws+
        ws+ symbol
        symbol)
      (factor-find-end-of-def)
      nil
      (1 'factor-font-lock-symbol nil t)
      (2 'factor-font-lock-symbol nil t)
      (3 'factor-font-lock-symbol nil t)))
    ,(factor-syntax factor-predicate-regex '("P" "T" "P" "T"))
    ;; Highlights alien function definitions. Types in stack effect
    ;; declarations are given a bold face.
    (,factor-alien-function-regex
     (1 'factor-font-lock-parsing-word)
     (2 'factor-font-lock-type-name)
     (3 'factor-font-lock-word)
     (,factor-function-params-regex
      (factor-find-ending-bracket)
      nil
      (1 'factor-font-lock-type-in-stack-effect nil t)
      (2 'factor-font-lock-stack-effect nil t)
      (3 'factor-font-lock-stack-effect nil t)))

    ;; Almost identical to the previous one, but for function aliases.
    (,factor-function-alias-regex
     (1 'factor-font-lock-parsing-word)
     (2 'factor-font-lock-word)
     (3 'factor-font-lock-type-name)
     (4 'factor-font-lock-word)
     (,factor-function-params-regex
      (factor-find-ending-bracket)
      nil
      (1 'factor-font-lock-type-in-stack-effect nil t)
      (2 'factor-font-lock-stack-effect nil t)
      (3 'factor-font-lock-stack-effect nil t)))
    ,(factor-syntax factor-integer-regex '("N"))
    (factor-match-brackets . 'factor-font-lock-stack-effect)
    ,(factor-syntax factor-constructor-regex '("CO"))
    (,factor-setter-regex . 'factor-font-lock-setter-word)
    (,factor-getter-regex . 'factor-font-lock-getter-word)
    (,factor-bad-string-regex . 'factor-font-lock-invalid-syntax)
    ("\\_<\\(P\\|SBUF\\|DLL\\)\"" 1 'factor-font-lock-parsing-word)
    (,factor-constant-words-regex . 'factor-font-lock-constant)
    ,(factor-syntax factor-parsing-words-regex '("P"))
    (,"\t" . 'whitespace-highlight-face)))

;; Handling of multi-line constructs
(defun factor-font-lock-extend-region ()
  (eval-when-compile (defvar font-lock-beg) (defvar font-lock-end))
  (save-excursion
    (goto-char font-lock-beg)
    (let ((found (or (re-search-backward "\n\n" nil t) (point-min))))
      (goto-char font-lock-end)
      (when (re-search-forward "\n\n" nil t)
        (beginning-of-line)
        (setq font-lock-end (point)))
      (setq font-lock-beg found))))

;;; Source code analysis:

(defsubst factor-brackets-depth ()
  (nth 0 (syntax-ppss)))

(defsubst factor-brackets-start ()
  (nth 1 (syntax-ppss)))

(defsubst factor-beginning-of-defun (&optional times)
  (re-search-backward factor-begin-of-def-regex nil t times))

(defsubst factor-end-of-defun ()
  (re-search-forward factor-end-of-def-regex nil t))

(defsubst factor-end-of-defun-pos ()
  (save-excursion
    (re-search-forward factor-end-of-def-regex nil t)
    (point)))

(defun factor-on-vocab ()
  "t if point is on a vocab name. We just piggyback on
  font-lock's pretty accurate information."
  (eq (get-char-property (point) 'face) 'factor-font-lock-vocabulary-name))

(defun factor-find-end-of-def (&rest foo)
  (save-excursion
    (re-search-forward "[ \n];" nil t)
    (1- (point))))

(defun factor-find-ending-bracket (&rest foo)
  (save-excursion
    (re-search-forward "[ \n]\)" nil t)
    (point)))

(defun factor-beginning-of-body ()
  (let ((p (point)))
    (and (factor-beginning-of-defun)
         (re-search-forward factor-defun-signature-regex p t)
         (not (re-search-forward factor-end-of-def-regex p t)))))

(defun factor-beginning-of-sexp ()
  (if (> (factor-brackets-depth) 0)
      (goto-char (factor-brackets-start))
    (factor-beginning-of-body)))

(defsubst factor-beginning-of-sexp-pos ()
  (save-excursion (factor-beginning-of-sexp) (point)))


;;; USING/IN:

(defvar-local factor-current-vocab-function 'factor-find-vocab-name)

(defsubst factor-current-vocab ()
  (funcall factor-current-vocab-function))

(defun factor-find-in ()
  (save-excursion
    (beginning-of-line)
    (if (re-search-backward factor-current-vocab-regex nil t)
        (match-string-no-properties 1)
      (when (re-search-forward factor-current-vocab-regex nil t)
        (match-string-no-properties 1)))))

(defun factor-in-private? ()
  "t if point is withing a PRIVATE-block, nil otherwise."
  (save-excursion
    (when (re-search-backward "\\_<<?PRIVATE>?\\_>" nil t)
      (string= (match-string-no-properties 0) "<PRIVATE"))))

(defun factor-find-vocab-name ()
  "Name of the vocab with possible .private suffix"
  (concat (factor-find-in) (if (factor-in-private?) ".private" "")))


(defvar-local factor-usings-function 'factor-find-usings)

(defsubst factor-usings ()
  (funcall factor-usings-function))

(defun factor-file-has-private ()
  (save-excursion
    (goto-char (point-min))
    (and (re-search-forward "\\_<<PRIVATE\\_>" nil t)
         (re-search-forward "\\_<PRIVATE>\\_>" nil t))))

(defun factor-find-usings (&optional no-private)
  "Lists all vocabs used by the vocab."
  (save-excursion
    (let ((usings))
      (goto-char (point-max))
      (while (re-search-backward factor-using-lines-regex nil t)
        (dolist (u (split-string (match-string-no-properties 2) nil t))
          (push u usings)))
      (when (and (not no-private) (factor-file-has-private))
        (goto-char (point-max))
        (push (concat (factor-find-in) ".private") usings))
      usings)))


;;; Buffer cycling:

(defconst factor-cycle-endings
  '(".factor" "-tests.factor" "-docs.factor"))

(defvar factor-cycle-ring
  (let ((ring (make-ring (length factor-cycle-endings))))
    (dolist (e factor-cycle-endings ring)
      (ring-insert ring e))
    ring))

(defconst factor-cycle-basename-regex
  (format "\\(.+?\\)\\(%s\\)$" (regexp-opt factor-cycle-endings)))

(defun factor-cycle-split (basename)
  (when (string-match factor-cycle-basename-regex basename)
    (cons (match-string 1 basename) (match-string 2 basename))))

(defun factor-cycle-next (file skip)
  (let* ((dir (file-name-directory file))
         (basename (file-name-nondirectory file))
         (p/s (factor-cycle-split basename))
         (prefix (car p/s))
         (ring factor-cycle-ring)
         (idx (or (ring-member ring (cdr p/s)) 0))
         (len (ring-size ring))
         (i 1)
         (result nil))
    (while (and (< i len) (not result))
      (let* ((suffix (ring-ref ring (+ i idx)))
             (path (expand-file-name (concat prefix suffix) dir)))
        (when (or (file-exists-p path)
                  (and (not skip)
                       (not (member suffix factor-cycling-no-ask))
                       (y-or-n-p (format "Create %s? " path))))
          (setq result path))
        (when (and (not factor-cycle-always-ask-p)
                   (not (member suffix factor-cycling-no-ask)))
          (setq factor-cycling-no-ask
                (cons name factor-cycling-no-ask))))
      (setq i (1+ i)))
    result))

(defun factor-visit-other-file (&optional create)
  "Cycle between code, tests and docs factor files.
With prefix, non-existing files will be created."
  (interactive "P")
  (let ((file (factor-cycle-next (buffer-file-name) (not create))))
    (unless file (error "No other file found"))
    (find-file file)
    (unless (file-exists-p file)
      (set-buffer-modified-p t)
      (save-buffer))))


;;; imenu tags

;; TODO Handle the plural words (SINGLETONS:, SYMBOLS:, etc)
(defvar factor-imenu-generic-expression
  `((nil
     ,(concat "^\\s-*"
              (regexp-opt '(":" "::" "ALIAS:" "BUILTIN:" "C:" "CONSTANT:" "ERROR:"
                            "GENERIC:" "GENERIC#:" "HOOK:" "INTERSECTION:" "MATH:"
                            "MIXIN:" "PREDICATE:" "PRIMITIVE:" "SINGLETON:" "SLOT:"
                            "SYMBOL:" "SYNTAX:" "TUPLE:" "UNION:" "LOG:" "C-TYPE:" "ENUM:"
                            "STRUCT:" "FUNCTION-ALIAS:"))
              "\\s-+\\(\\(?:\\s_\\|\\sw\\|\\s\\\\)+\\)")
     1)
    ("Methods"
     ,(concat "^\\s-*"
              (regexp-opt '("M:" "M::"))
              "\\s-+\\(\\(?:\\s_\\|\\sw|\\s\\\\)+\\s-+\\(?:\\s_\\|\\sw|\\s\\\\)+\\)")
     1)
    (nil
     ,(concat "^\\s-*"
              (regexp-opt '("FUNCTION:" "TYPEDEF:"))
              "\\s-+\\(?:\\(?:\\s_\\|\\sw\\|\\s\\\\)+\\s-+\\)\\(\\(?:\\s_\\|\\sw\\|\\s\\\\)+\\)")
     1))
  "Imenu generic expression for factor-mode. See `imenu-generic-expression'.")


;;; factor-mode:

(defvar factor-mode-syntax-table (fuel-syntax-table))

(defun factor-setup-buffer-font-lock ()
  (setq-local comment-start "! ")
  (setq-local comment-end "")
  (setq-local comment-column factor-comment-column)
  (setq-local comment-start-skip "!+ *")
  (setq-local parse-sexp-ignore-comments t)
  (setq-local parse-sexp-lookup-properties t)
  (setq-local font-lock-defaults '(factor-font-lock-keywords))
  ;; Some syntactic constructs are often split over multiple lines so
  ;; we need to setup multiline font-lock.
  (setq-local font-lock-multiline t)
  (add-hook 'font-lock-extend-region-functions 'factor-font-lock-extend-region)
  (setq-local syntax-propertize-function 'factor-syntax-propertize))

(defun factor-font-lock-string (str)
  "Fontify STR as if it was Factor code."
  (with-temp-buffer
    (set-syntax-table factor-mode-syntax-table)
    (factor-setup-buffer-font-lock)
    (insert str)
    (let ((font-lock-verbose nil))
      (font-lock-fontify-buffer))
    (buffer-string)))

(defun factor-syntax-propertize (start end)
  (funcall
   (syntax-propertize-rules
    ("\\(^\\| \\|\t\\)\\(!\\|#!\\)\\($\\| \\|\t\\)" (2 "<   ")))
   start end))

;;;###autoload
(define-derived-mode factor-mode prog-mode "Factor"
  "A mode for editing programs written in the Factor programming language.
\\{factor-mode-map}"
  (factor-setup-buffer-font-lock)
  (define-key factor-mode-map [remap ff-get-other-file]
    'factor-visit-other-file)

  (setq-local electric-indent-chars
              (append '(?\] ?\} ?\n) electric-indent-chars))

  ;; No tabs for you!!
  (setq-local indent-tabs-mode nil)

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

  (setq-local beginning-of-defun-function 'factor-beginning-of-defun)
  (setq-local end-of-defun-function 'factor-end-of-defun)
  ;; Load fuel-mode too if factor-mode-use-fuel is t.
  (when factor-mode-use-fuel (require 'fuel-mode) (fuel-mode)))

;;;###autoload
(add-to-list 'auto-mode-alist '("\\.factor\\'" . factor-mode))

;;;###autoload
(add-to-list 'interpreter-mode-alist '("factor" . factor-mode))


(provide 'factor-mode)

;;; factor-mode.el ends here