export back-ends: Apply line break changes

[org-mode.git] / contrib / lisp / org-md.el

;;; org-md.el --- Markdown Back-End for Org Export Engine

;; Copyright (C) 2012  Free Software Foundation, Inc.

;; Author: Nicolas Goaziou <n.goaziou@gmail.com>
;; Keywords: org, wp, tex

;; 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 library implements a Markdown back-end (vanilla flavour) for
;; Org exporter, based on `e-html'.
;;
;; It provides two commands for export, depending on the desired
;; output: `org-md-export-as-markdown' (temporary buffer) and
;; `org-md-export-to-markdown' ("md" file).

;;; Code:

(require 'org-e-html)


\f
;;; User-Configurable Variables

(defgroup org-export-md nil
  "Options specific to Markdown export back-end."
  :tag "Org Markdown"
  :group 'org-export
  :version "24.2")

(defcustom org-md-headline-style 'atx
  "Style used to format headlines.
This variable can be set to either `atx' or `setext'."
  :group 'org-export-md
  :type '(choice
          (const :tag "Use \"atx\" style" atx)
          (const :tag "Use \"Setext\" style" setext)))


\f
;;; Define Back-End

(org-export-define-derived-backend md e-html
  :export-block ("MD" "MARKDOWN")
  :filters-alist ((:filter-parse-tree . org-md-separate-elements))
  :menu-entry
  (?m "Export to Markdown"
      ((?M "To temporary buffer"
           (lambda (s v b) (org-md-export-as-markdown s v)))
       (?m "To file" (lambda (s v b) (org-md-export-to-markdown s v)))
       (?o "To file and open"
           (lambda (s v b) (org-open-file (org-md-export-to-markdown s v))))))
  :translate-alist ((bold . org-md-bold)
                    (code . org-md-verbatim)
                    (example-block . org-md-example-block)
                    (footnote-definition . ignore)
                    (footnote-reference . ignore)
                    (headline . org-md-headline)
                    (horizontal-rule . org-md-horizontal-rule)
                    (inline-src-block . org-md-verbatim)
                    (italic . org-md-italic)
                    (item . org-md-item)
                    (line-break . org-md-line-break)
                    (link . org-md-link)
                    (paragraph . org-md-paragraph)
                    (plain-list . org-md-plain-list)
                    (plain-text . org-md-plain-text)
                    (quote-block . org-md-quote-block)
                    (quote-section . org-md-example-block)
                    (section . org-md-section)
                    (src-block . org-md-example-block)
                    (template . org-md-template)
                    (verbatim . org-md-verbatim)))


\f
;;; Filters

(defun org-md-separate-elements (tree backend info)
  "Make sure elements are separated by at least one blank line.

TREE is the parse tree being exported.  BACKEND is the export
back-end used.  INFO is a plist used as a communication channel.

Assume BACKEND is `md'."
  (org-element-map
   tree org-element-all-elements
   (lambda (elem)
     (unless (eq (org-element-type elem) 'org-data)
       (org-element-put-property
        elem :post-blank
        (let ((post-blank (org-element-property :post-blank elem)))
          (if (not post-blank) 1 (max 1 post-blank)))))))
  ;; Return updated tree.
  tree)


\f
;;; Transcode Functions

;;;; Bold

(defun org-md-bold (bold contents info)
  "Transcode BOLD object into Markdown format.
CONTENTS is the text within bold markup.  INFO is a plist used as
a communication channel."
  (format "**%s**" contents))


;;;; Code and Verbatim

(defun org-md-verbatim (verbatim contents info)
  "Transcode VERBATIM object into Markdown format.
CONTENTS is nil.  INFO is a plist used as a communication
channel."
  (let ((value (org-element-property :value verbatim)))
    (format (cond ((not (string-match "`" value)) "`%s`")
                  ((or (string-match "\\``" value)
                       (string-match "`\\'" value))
                   "`` %s ``")
                  (t "``%s``"))
            value)))


;;;; Example Block and Src Block

(defun org-md-example-block (example-block contents info)
  "Transcode EXAMPLE-BLOCK element into Markdown format.
CONTENTS is nil.  INFO is a plist used as a communication
channel."
  (replace-regexp-in-string
   "^" "    "
   (org-remove-indentation
    (org-element-property :value example-block))))


;;;; Headline

(defun org-md-headline (headline contents info)
  "Transcode HEADLINE element into Markdown format.
CONTENTS is the headline contents.  INFO is a plist used as
a communication channel."
  (unless (org-element-property :footnote-section-p headline)
    (let* ((level (org-export-get-relative-level headline info))
           (title (org-export-data (org-element-property :title headline) info))
           (todo (and (plist-get info :with-todo-keywords)
                      (let ((todo (org-element-property :todo-keyword
                                                        headline)))
                        (and todo (concat (org-export-data todo info) " ")))))
           (tags (and (plist-get info :with-tags)
                      (let ((tag-list (org-export-get-tags headline info)))
                        (and tag-list
                             (format "     :%s:"
                                     (mapconcat 'identity tag-list ":"))))))
           (priority
            (and (plist-get info :with-priority)
                 (let ((char (org-element-property :priority headline)))
                   (and char (format "[#%c] " char)))))
           ;; Headline text without tags.
           (heading (concat todo priority title)))
      (cond
       ;; Cannot create an headline.  Fall-back to a list.
       ((or (org-export-low-level-p headline info)
            (not (memq org-md-headline-style '(atx setext)))
            (and (eq org-md-headline-style 'atx) (> level 6))
            (and (eq org-md-headline-style 'setext) (> level 2)))
        (let ((bullet
               (if (not (org-export-numbered-headline-p headline info)) "-"
                 (concat (number-to-string
                          (car (last (org-export-get-headline-number
                                      headline info))))
                         "."))))
          (concat bullet (make-string (- 4 (length bullet)) ? ) heading tags
                  "\n\n"
                  (and contents
                       (replace-regexp-in-string "^" "    " contents)))))
       ;; Use "Setext" style.
       ((eq org-md-headline-style 'setext)
        (concat heading tags "\n"
                (make-string (length heading) (if (= level 1) ?= ?-))
                "\n\n"
                contents))
       ;; Use "atx" style.
       (t (concat (make-string level ?#) " " heading tags "\n\n" contents))))))


;;;; Horizontal Rule

(defun org-md-horizontal-rule (horizontal-rule contents info)
  "Transcode HORIZONTAL-RULE element into Markdown format.
CONTENTS is the horizontal rule contents.  INFO is a plist used
as a communication channel."
  "---")


;;;; Italic

(defun org-md-italic (italic contents info)
  "Transcode ITALIC object into Markdown format.
CONTENTS is the text within italic markup.  INFO is a plist used
as a communication channel."
  (format "*%s*" contents))


;;;; Item

(defun org-md-item (item contents info)
  "Transcode ITEM element into Markdown format.
CONTENTS is the item contents.  INFO is a plist used as
a communication channel."
  (let* ((type (org-element-property :type (org-export-get-parent item)))
         (struct (org-element-property :structure item))
         (bullet (if (not (eq type 'ordered)) "-"
                   (concat (number-to-string
                            (car (last (org-list-get-item-number
                                        (org-element-property :begin item)
                                        struct
                                        (org-list-prevs-alist struct)
                                        (org-list-parents-alist struct)))))
                           "."))))
    (concat bullet
            (make-string (- 4 (length bullet)) ? )
            (case (org-element-property :checkbox item)
              (on "[X] ")
              (trans "[-] ")
              (off "[ ] "))
            (let ((tag (org-element-property :tag item)))
              (and tag (format "**%s:** "(org-export-data tag info))))
            (org-trim (replace-regexp-in-string "^" "    " contents)))))


;;;; Line Break

(defun org-md-line-break (line-break contents info)
  "Transcode LINE-BREAK object into Markdown format.
CONTENTS is nil.  INFO is a plist used as a communication
channel."
  "  \n")


;;;; Link

(defun org-md-link (link contents info)
  "Transcode LINE-BREAK object into Markdown format.
CONTENTS is the link's description.  INFO is a plist used as
a communication channel."
  (let ((--link-org-files-as-html-maybe
         (function
          (lambda (raw-path info)
            ;; Treat links to `file.org' as links to `file.html', if
            ;; needed.  See `org-e-html-link-org-files-as-html'.
            (cond
             ((and org-e-html-link-org-files-as-html
                   (string= ".org"
                            (downcase (file-name-extension raw-path "."))))
              (concat (file-name-sans-extension raw-path) "."
                      (plist-get info :html-extension)))
             (t raw-path)))))
        (type (org-element-property :type link)))
    (cond ((member type '("custom-id" "id"))
           (let ((destination (org-export-resolve-id-link link info)))
             (if (stringp destination)  ; External file.
                 (let ((path (funcall --link-org-files-as-html-maybe
                                      destination info)))
                   (if (not contents) (format "<%s>" path)
                     (format "[%s](%s)" contents path)))
               (concat
                (and contents (concat contents " "))
                (format "(%s)"
                        (format (org-export-translate "See section %s" :html info)
                                (mapconcat 'number-to-string
                                           (org-export-get-headline-number
                                            destination info)
                                           ".")))))))
          ((org-export-inline-image-p link org-e-html-inline-image-rules)
           (let ((path (let ((raw-path (org-element-property :path link)))
                         (if (not (file-name-absolute-p raw-path)) raw-path
                           (expand-file-name raw-path)))))
             (format "![%s](%s)"
                     (let ((caption (org-export-get-caption
                                     (org-export-get-parent-element link))))
                       (when caption (org-export-data caption info)))
                     path)))
          ((string= type "coderef")
           (let ((ref (org-element-property :path link)))
             (format (org-export-get-coderef-format ref contents)
                     (org-export-resolve-coderef ref info))))
          ((equal type "radio")
           (let ((destination (org-export-resolve-radio-link link info)))
             (org-export-data (org-element-contents destination) info)))
          ((equal type "fuzzy")
           (let ((destination (org-export-resolve-fuzzy-link link info)))
             ;; Ignore invisible "#+TARGET: path".
             (unless (eq (org-element-type destination) 'keyword)
               (if (org-string-nw-p contents) contents
                 (when destination
                   (let ((number (org-export-get-ordinal destination info)))
                     (when number
                       (if (atom number) (number-to-string number)
                         (mapconcat 'number-to-string number ".")))))))))
          (t (let* ((raw-path (org-element-property :path link))
                    (path (cond
                           ((member type '("http" "https" "ftp"))
                            (concat type ":" raw-path))
                           ((equal type "file")
                            ;; Treat links to ".org" files as ".html",
                            ;; if needed.
                            (setq raw-path
                                  (funcall --link-org-files-as-html-maybe
                                           raw-path info))
                            ;; If file path is absolute, prepend it
                            ;; with protocol component - "file://".
                            (if (not (file-name-absolute-p raw-path)) raw-path
                              (concat "file://" (expand-file-name raw-path))))
                           (t raw-path))))
               (if (not contents) (format "<%s>" path)
                 (format "[%s](%s)" contents path)))))))


;;;; Paragraph

(defun org-md-paragraph (paragraph contents info)
  "Transcode PARAGRAPH element into Markdown format.
CONTENTS is the paragraph contents.  INFO is a plist used as
a communication channel."
  (let ((first-object (car (org-element-contents paragraph))))
    ;; If paragraph starts with a #, protect it.
    (if (and (stringp first-object) (string-match "\\`#" first-object))
        (replace-regexp-in-string "\\`#" "\\#" contents nil t)
      contents)))


;;;; Plain List

(defun org-md-plain-list (plain-list contents info)
  "Transcode PLAIN-LIST element into Markdown format.
CONTENTS is the plain-list contents.  INFO is a plist used as
a communication channel."
  contents)


;;;; Plain Text

(defun org-md-plain-text (text info)
  "Transcode a TEXT string into Markdown format.
TEXT is the string to transcode.  INFO is a plist holding
contextual information."
  (when (plist-get info :with-smart-quotes)
    (setq text (org-export-activate-smart-quotes text :html info)))
  ;; Protect ambiguous #.  This will protect # at the beginning of
  ;; a line, but not at the beginning of a paragraph.  See
  ;; `org-md-paragraph'.
  (setq text (replace-regexp-in-string "\n#" "\n\\\\#" text))
  ;; Protect ambiguous !
  (setq text (replace-regexp-in-string "\\(!\\)\\[" "\\\\!" text nil nil 1))
  ;; Protect `, *, _ and \
  (setq text (replace-regexp-in-string "[`*_\\]" "\\\\\\&" text))
  ;; Handle special strings, if required.
  (when (plist-get info :with-special-strings)
    (setq text (org-e-html-convert-special-strings text)))
  ;; Handle break preservation, if required.
  (when (plist-get info :preserve-breaks)
    (setq text (replace-regexp-in-string "[ \t]*\n" "  \n" text)))
  ;; Return value.
  text)


;;;; Quote Block

(defun org-md-quote-block (quote-block contents info)
  "Transcode QUOTE-BLOCK element into Markdown format.
CONTENTS is the quote-block contents.  INFO is a plist used as
a communication channel."
  (replace-regexp-in-string
   "^" "> "
   (replace-regexp-in-string "\n\\'" "" contents)))


;;;; Section

(defun org-md-section (section contents info)
  "Transcode SECTION element into Markdown format.
CONTENTS is the section contents.  INFO is a plist used as
a communication channel."
  contents)


;;;; Template

(defun org-md-template (contents info)
  "Return complete document string after Markdown conversion.
CONTENTS is the transcoded contents string.  INFO is a plist used
as a communication channel."
  contents)


\f
;;; Interactive function

;;;###autoload
(defun org-md-export-as-markdown (&optional subtreep visible-only)
  "Export current buffer to a text buffer.

If narrowing is active in the current buffer, only export its
narrowed part.

If a region is active, export that region.

When optional argument SUBTREEP is non-nil, export the sub-tree
at point, extracting information from the headline properties
first.

When optional argument VISIBLE-ONLY is non-nil, don't export
contents of hidden elements.

Export is done in a buffer named \"*Org MD Export*\", which will
be displayed when `org-export-show-temporary-export-buffer' is
non-nil."
  (interactive)
  (let ((outbuf (org-export-to-buffer
                 'md "*Org MD Export*" subtreep visible-only)))
    (with-current-buffer outbuf (text-mode))
    (when org-export-show-temporary-export-buffer
      (switch-to-buffer-other-window outbuf))))


;;;###autoload
(defun org-md-export-to-markdown (&optional subtreep visible-only)
  "Export current buffer to a Markdown file.

If narrowing is active in the current buffer, only export its
narrowed part.

If a region is active, export that region.

When optional argument SUBTREEP is non-nil, export the sub-tree
at point, extracting information from the headline properties
first.

When optional argument VISIBLE-ONLY is non-nil, don't export
contents of hidden elements.

Return output file's name."
  (interactive)
  (let ((outfile (org-export-output-file-name ".md" subtreep)))
    (org-export-to-file 'md outfile subtreep visible-only)))


(provide 'org-md)
;;; org-md.el ends here