;;; rainbow-delimiters.el --- Color nested parentheses, brackets, and braces according to their depth.

;; Copyright (C) 2010-2011 Jeremy L. Rayman.
;; Author: Jeremy L. Rayman <jeremy.rayman@gmail.com>
;; Maintainer: Jeremy L. Rayman <jeremy.rayman@gmail.com>
;; Created: 2010-09-02
;; Version: 1.3
;; Keywords: faces, convenience, lisp, matching, tools, rainbow, rainbow parentheses, rainbow parens
;; EmacsWiki: http://www.emacswiki.org/emacs/RainbowDelimiters
;; URL: http://www.emacswiki.org/emacs/download/rainbow-delimiters.el

;; This program 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.

;; This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.


;;; Commentary:

;; This is a "rainbow parentheses" mode which includes support for
;; parens "()", brackets "[]", and braces "{}". It conveys nesting depth
;; by using a different color for each successive nested set of
;; delimiters. It highlights all statements at a given level using the
;; same color - if several statements are all at the same depth, they
;; will all be the same color.
;;
;; Great care has been taken to make this mode FAST. You should see no
;; discernible change in scrolling or editing speed while using it,
;; even with delimiter-rich languages like Clojure, Lisp, and Scheme.
;;
;; The ultimate goal for the mode is to be useful with a wide variety
;; of programming languages with optional semantics catered to each.
;;
;; Default colors are subtle, with the philosophy that it's better to
;; avoid being visually intrusive. Color schemes are always a matter of
;; taste.  If you take the time to design a new color scheme, please
;; share it (a plain-text list of colors is fine) on the EmacsWiki page!
;; URL: http://www.emacswiki.org/emacs/RainbowDelimiters


;;; Installation:

;; 1. Place rainbow-delimiters.el on your emacs load-path.
;;
;; 2. Compile the file (necessary for speed):
;; M-x byte-compile-file <location of rainbow-delimiters.el>
;;
;; 3. Add the following to your dot-emacs/init file:
;; (require 'rainbow-delimiters)
;;
;; 4. Add hooks for modes where you want it enabled, for example:
;; (add-hook 'clojure-mode-hook 'rainbow-delimiters-mode)
;;
;; - To activate rainbow-delimiters mode temporarily in a buffer:
;; M-x rainbow-delimiters-mode
;;
;; 5. When using a dark background, if delimiter colors seem washed out
;;   you may need to add the following to your dot-emacs and restart:
;; (setq-default 'frame-background-mode 'dark)
;;
;; This is because Emacs can guess frame-background-mode incorrectly,
;; causing rainbow-delimiters to use its light color scheme on dark
;; backgrounds.
;;
;; The light/dark color schemes differ only in their brightness level.

;;; Customization:

;; To customize various options, including the color scheme:
;; M-x customize-group rainbow-delimiters
;;
;; color-theme.el users:
;; If you use the color-theme package, you can specify custom colors
;; by adding the appropriate faces to your theme.
;; - Faces take the form of:
;;   'rainbow-delimiters-depth-#-face' with # being the depth.
;;   Depth begins at 1, the outermost color.
;;   Faces exist for depths 1-9.
;; - The unmatched delimiter face (normally colored red) is:
;;   'rainbow-delimiters-unmatched-face'


;;; Change Log:

;; 1.0 - Initial release.
;; 1.1 - Stop tracking each delimiter's depth independently.
;;       This had lead to confusing results when viewing clojure
;;       code. Instead, just color based on current nesting inside
;;       all delimiters combined.
;;     - Added 'all-delimiters' faces to apply a color scheme to
;;       all delimiters at once. Other faces inherit from this group.
;; 1.1.1 - Change color scheme to a lighter, more subtle style.
;; 1.1.2: (2011-03-25)
;;  - Add an unmatched-delimiter face and correct problem with
;;    coloring of text following unmatched closing delims.
;; 1.2: (2011-03-28)
;;  - Unify delimiter faces: all delimiter types now use the same depth
;;    faces, of form 'rainbow-delimiters-depth-#-face'.
;; 1.2.1: (2011-03-29)
;;  - Conform to ELPA conventions.
;; 1.3: (2011-05-24)
;;  - Add separate light and dark color schemes.
;;  - Checkboxes to enable/disable highlighting for each delimiter type.
;;  - Improvements to Customize interface.
;;  - Infinite depth support by cycling through defined faces repeatedly.
;;  - Documentation changes.

;;; TODO:

;; - Add support for independent depth tracking for each delimiter type,
;;   for users of C-like languages.
;; - Add Python support - highlighting parens according to indentation level.
;; - Add support for nested tags (XML, HTML)
;; - Set up proper example color-theme.el themes for rainbow-delimiters mode.
;; - Intelligent support for other languages: Ruby, et al.

;;; Issues:

;; - Rainbow-delimiters mode does not appear to change the color of
;;   delimiters when Org-mode is also enabled.
;; - Some Emacs versions don't set frame-background-mode to dark automatically,
;;   causing users of dark backgrounds to receive the wrong set of colors.
;;   See step number 5 in the Installation section.


;;; Code:

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


;;; Customize interface:

(defgroup rainbow-delimiters nil
  "Color nested parentheses, brackets, and braces according to their depth."
  :prefix "rainbow-delimiters-"
  :link '(url-link :tag "Website for rainbow-delimiters (EmacsWiki)"
                   "http://www.emacswiki.org/emacs/RainbowDelimiters")
  :group 'applications)

(defgroup rainbow-delimiters-faces nil
  "Faces for each successively nested pair of delimiters.

Colors repeatedly cycle through when nesting depth exceeds innermost defined face."
  :tag "Color Scheme"
  :group 'rainbow-delimiters
  :link '(custom-group-link "rainbow-delimiters")
  :link '(custom-group-link :tag "Toggle Delimiters" "rainbow-delimiters-toggle-delimiter-highlighting")
  :prefix 'rainbow-delimiters-faces-)

;; Choose which delimiters you wish to highlight in your preferred language:

(defgroup rainbow-delimiters-toggle-delimiter-highlighting nil
  "Choose which delimiters this mode should colorize."
  :tag "Toggle Delimiters"
  :group 'rainbow-delimiters
  :link '(custom-group-link "rainbow-delimiters")
  :link '(custom-group-link :tag "Color Scheme" "rainbow-delimiters-faces"))

(defcustom rainbow-delimiters-highlight-parens-p t
  "Enable highlighting of nested parentheses -- ().

Non-nil (default) enables highlighting of parentheses.
Nil disables parentheses highlighting."
  :tag "Highlight Parentheses?"
  :type 'boolean
  :group 'rainbow-delimiters-toggle-delimiter-highlighting)

(defcustom rainbow-delimiters-highlight-brackets-p t
  "Enable highlighting of nested brackets -- [].

Non-nil (default) enables highlighting of brackets.
Nil disables bracket highlighting."
  :tag "Highlight Brackets?"
  :type 'boolean
  :group 'rainbow-delimiters-toggle-delimiter-highlighting)

(defcustom rainbow-delimiters-highlight-braces-p t
  "Enable highlighting of nested braces -- {}.

Non-nil (default) enables highlighting of braces.
Nil disables brace highlighting."
  :tag "Highlight Braces?"
  :type 'boolean
  :group 'rainbow-delimiters-toggle-delimiter-highlighting)


;;; Faces:

;; Unmatched delimiter face:
(defface rainbow-delimiters-unmatched-face
  '((((background light)) (:foreground "#DD090B"))
    (((background dark)) (:foreground "#88090B")))
  "Face to color unmatched closing delimiters with."
  :group 'rainbow-delimiters-faces)


;; NOTE: The use of repetitious definitions for depth faces is temporary.
;; Once the emacs 24 color theme support comes in, this will be reevaluated.

;; Faces for colorizing delimiters at each level:
(defface rainbow-delimiters-depth-1-face
  '((((background light)) (:foreground "grey55"))
    (((background dark)) (:foreground "grey55")))
  "Nested delimiters face, depth 1 - the outermost pair."
  :tag "Rainbow Delimiters Depth 1 Face -- OUTERMOST"
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-2-face
  '((((background light)) (:foreground "#6e7e94"))
    (((background dark)) (:foreground "#93a8c6")))
  "Nested delimiters face, depth 2."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-3-face
  '((((background light)) (:foreground "#84847a"))
    (((background dark)) (:foreground "#b0b1a3")))
  "Nested delimiters face, depth 3."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-4-face
  '((((background light)) (:foreground "#718472"))
    (((background dark)) (:foreground "#97b098")))
  "Nested delimiters face, depth 4."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-5-face
  '((((background light)) (:foreground "#828ea2"))
    (((background dark)) (:foreground "#aebed8")))
  "Nested delimiters face, depth 5."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-6-face
  '((((background light)) (:foreground "#848486"))
    (((background dark)) (:foreground "#b0b0b3")))
  "Nested delimiters face, depth 6."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-7-face
  '((((background light)) (:foreground "#6c7e6c"))
    (((background dark)) (:foreground "#90a890")))
  "Nested delimiters face, depth 7."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-8-face
  '((((background light)) (:foreground "#7988a3"))
    (((background dark)) (:foreground "#a2b6da")))
  "Nested delimiters face, depth 8."
  :group 'rainbow-delimiters-faces)

(defface rainbow-delimiters-depth-9-face
  '((((background light)) (:foreground "#758881"))
    (((background dark)) (:foreground "#9cb6ad")))
  "Nested delimiters face, depth 9."
  :group 'rainbow-delimiters-faces)

;;; Faces 10+:
;; NOTE: Currently unused. Additional faces for depths 9+ can be added on request.

(defconst rainbow-delimiters-max-face-count 9
  "Number of faces defined for highlighting delimiter levels.

Determines depth at which to cycle through faces again.")

;;; Face utility functions

;; inlining this function for speed:
;; see: http://www.gnu.org/s/emacs/manual/html_node/elisp/Compilation-Tips.html
;; this will cause problems with debugging. To debug, change defsubst -> defun.
(defsubst rainbow-delimiters-depth-face (depth)
  "Return face-name for DEPTH as a string 'rainbow-delimiters-depth-DEPTH-face'.
DEPTH is the number of nested levels deep for the delimiter being colorized.

Returns a face namestring the of form 'rainbow-delimiters-depth-DEPTH-face',
e.g. 'rainbow-delimiters-depth-1-face'."
  (concat "rainbow-delimiters-depth-"
          (number-to-string
           (or
            ;; Our nesting depth has a face defined for it.
            (and (< depth rainbow-delimiters-max-face-count)
                 depth)
            ;; Deeper than # of defined faces; cycle back through to beginning.
            (let ((cycled-depth (mod depth rainbow-delimiters-max-face-count)))
              (if (/= cycled-depth 0)
                  ;; Return face # that corresponds to current nesting level.
                  (mod depth rainbow-delimiters-max-face-count)
                ;; Special case: depth divides evenly into max, correct face # is max.
                rainbow-delimiters-max-face-count))))
          "-face"))


;;; Nesting level

;; syntax-table: used with parse-partial-sexp for determining current depth.
(defvar rainbow-delimiters-delim-syntax-table
  (let ((table (copy-syntax-table emacs-lisp-mode-syntax-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)
    table)
  "Syntax table for recognizing all supported delimiter types.")

(defun rainbow-delimiters-depth (point)
  "Return # of nested levels of parens, brackets, braces POINT is inside of."
  (save-excursion
      (beginning-of-defun)
      (let ((depth
             (with-syntax-table rainbow-delimiters-delim-syntax-table
               (car (parse-partial-sexp (point) point)))))
        (if (>= depth 0)
            depth
          0)))) ; ignore negative depths created by unmatched closing parens.


;;; Text properties

;; inlining this function for speed:
;; see: http://www.gnu.org/s/emacs/manual/html_node/elisp/Compilation-Tips.html
;; this will cause problems with debugging. To debug, change defsubst -> defun.
(defsubst rainbow-delimiters-propertize-delimiter (point depth)
  "Colorize delimiter at POINT according to DEPTH.

POINT is the point of character to propertize.
DEPTH is the nested delimiter depth at POINT, which determines the face to use.

Sets text properties:
`font-lock-face' to the corresponding delimiter face.
`rear-nonsticky' to prevent color from bleeding into subsequent characters typed by the user."
  (with-silent-modifications
    (let ((delim-face (if (<= depth 0)
                          "rainbow-delimiters-unmatched-face"
                        (rainbow-delimiters-depth-face depth))))
      ;; (when (eq depth -1) (message "Unmatched delimiter at char %s." point))
      (add-text-properties point (1+ point)
                           `(font-lock-face ,delim-face
                             rear-nonsticky t)))))


(defun rainbow-delimiters-unpropertize-delimiter (point)
  "Remove text properties set by rainbow-delimiters mode from char at POINT."
  (with-silent-modifications
    (remove-text-properties point (1+ point)
                            '(font-lock-face nil
                              rear-nonsticky nil))))


(defun rainbow-delimiters-char-ineligible-p (point)
  "Return t if char at POINT should be skipped, e.g. if inside a comment.

Returns t if char at point meets one of the following conditions:
- Inside a string.
- Inside a comment.
- Is an escaped char, e.g. ?\)"
  (let ((parse-state (save-excursion
                       (beginning-of-defun)
                       ;; (point) is at beg-of-defun; point is the char location
                       (parse-partial-sexp (point) point))))
    (or
     (nth 3 parse-state)                ; inside string?
     (nth 4 parse-state)                ; inside comment?
     (and (eq (char-before point) ?\\)  ; escaped char, e.g. ?\) - not counted
          (and (not (eq (char-before (1- point)) ?\\)) ; special-case: ignore ?\\
               (eq (char-before (1- point)) ?\?))))))
;; NOTE: standard char read syntax '?)' is not tested for because emacs manual
;; states punctuation such as delimiters should _always_ use escaped '?\)' form.


(defsubst rainbow-delimiters-apply-color (delim depth point)
  "Apply color for DEPTH to DELIM at POINT following user settings.

DELIM is a string specifying delimiter type.
DEPTH is the delimiter depth, or corresponding face # if colors are repeating.
POINT is location of character (delimiter) to be colorized."
  (and
   ;; Ensure user has enabled highlighting of this delimiter type.
   (symbol-value (intern-soft
                  (concat "rainbow-delimiters-highlight-" delim "s-p")))
   (rainbow-delimiters-propertize-delimiter point
                                            depth)))


;;; JIT-Lock functionality

;; Used to skip delimiter-by-delimiter `rainbow-delimiters-propertize-region'.
(defvar rainbow-delimiters-delim-regex "\\(\(\\|\)\\|\\[\\|\\]\\|\{\\|\}\\)"
  "Regex matching all opening and closing delimiters we intend to colorize.")

;; main function called by jit-lock:
(defun rainbow-delimiters-propertize-region (start end)
  "Colorize delimiters in region between START and END.

Used by jit-lock for dynamic highlighting."
  (save-excursion
    (goto-char start)
    ;; START can be anywhere in buffer; begin depth counts from values at START.
    (let ((depth (rainbow-delimiters-depth start)))
      (while (and (< (point) end)
                  (re-search-forward rainbow-delimiters-delim-regex end t))
        (backward-char) ; re-search-forward places point after delim; go back.
        (unless (rainbow-delimiters-char-ineligible-p (point))
          (let ((delim (char-after (point))))
            (cond ((eq ?\( delim)       ; (
                   (setq depth (1+ depth))
                   (rainbow-delimiters-apply-color "paren" depth (point)))
                  ((eq ?\) delim)       ; )
                   (rainbow-delimiters-apply-color "paren" depth (point))
                   (setq depth (or (and (<= depth 0) 0) ; unmatched paren
                                   (1- depth))))
                  ((eq ?\[ delim)       ; [
                   (setq depth (1+ depth))
                   (rainbow-delimiters-apply-color "bracket" depth (point)))
                  ((eq ?\] delim)       ; ]
                   (rainbow-delimiters-apply-color "bracket" depth (point))
                   (setq depth (or (and (<= depth 0) 0) ; unmatched bracket
                                   (1- depth))))
                  ((eq ?\{ delim)       ; {
                   (setq depth (1+ depth))
                   (rainbow-delimiters-apply-color "brace" depth (point)))
                  ((eq ?\} delim)       ; }
                   (rainbow-delimiters-apply-color "brace" depth (point))
                   (setq depth (or (and (<= depth 0) 0) ; unmatched brace
                                   (1- depth)))))))
        ;; move past delimiter so re-search-forward doesn't pick it up again
        (forward-char)))))

(defun rainbow-delimiters-unpropertize-region (start end)
  "Remove mode faces from delimiters in region between START and END."
  (save-excursion
    (goto-char start)
    (while (and (< (point) end)
                (re-search-forward rainbow-delimiters-delim-regex end t))
      ;; re-search-forward places point 1 further than the delim matched:
      (rainbow-delimiters-unpropertize-delimiter (1- (point))))))


;;; Minor mode:

;;;###autoload
(define-minor-mode rainbow-delimiters-mode
  "Color nested parentheses, brackets, and braces according to their depth."
  nil "" nil ; No modeline lighter - it's already obvious when the mode is on.
  (if (not rainbow-delimiters-mode)
      (progn
        (jit-lock-unregister 'rainbow-delimiters-propertize-region)
        (rainbow-delimiters-unpropertize-region (point-min) (1- (point-max))))
    (jit-lock-register 'rainbow-delimiters-propertize-region t)))


(provide 'rainbow-delimiters)

;;; rainbow-delimiters.el ends here.