;;; org-download.el --- Image drag-and-drop for Emacs org-mode

;; Copyright (C) 2014 Free Software Foundation, Inc.

;; Author: Oleh Krehel
;; Keywords: images, screenshots, download
;; Homepage: http://orgmode.org

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:
;;
;; This extension facilitates moving images from point A to point B.
;;
;; Point A (the source) can be:
;; 1. An image inside your browser that you can drag to Emacs.
;; 2. An image on your file system that you can drag to Emacs.
;; 3. A local or remote image address in kill-ring.
;;    Use the `org-download-yank' command for this.
;;    Remember that you can use "0 w" in `dired' to get an address.
;; 4. An screenshot taken using `gnome-screenshot' or `scrot' or `gm'.
;;    Use the `org-download-screenshot' command for this.
;;    Customize the backend with  `org-download-screenshot-method'.
;;
;; Point B (the target) is an Emacs `org-mode' buffer where the inline
;; link will be inserted.  Several customization options will determine
;; where exactly on the file system the file will be stored.
;;
;; They are:
;; `org-download-method':
;; a. 'attach => use `org-mode' attachment machinery
;; b. 'directory => construct the directory in two stages:
;;    1. first part of the folder name is:
;;       * either "." (current folder)
;;       * or `org-download-image-dir' (if it's not nil).
;;         `org-download-image-dir' becomes buffer-local when set,
;;         so each file can customize this value, e.g with:
;;         # -*- mode: Org; org-download-image-dir: ~/Pictures/foo; -*-
;;    2. second part is:
;;       * `org-download-heading-lvl' is nil => ""
;;       * `org-download-heading-lvl' is n => the name of current
;;         heading with level n. Level count starts with 0,
;;         i.e. * is 0, ** is 1, *** is 2 etc.
;;         `org-download-heading-lvl' becomes buffer-local when set,
;;         so each file can customize this value, e.g with:
;;         # -*- mode: Org; org-download-heading-lvl: nil; -*-
;;
;; `org-download-timestamp':
;; optionally add a timestamp to the file name.
;;
;; Customize `org-download-backend' to choose between `url-retrieve'
;; (the default) or `wget' or `curl'.
;;
;;; Code:
\f

(eval-when-compile
  (require 'cl))
(require 'url-parse)
(require 'url-http)

(defgroup org-download nil
  "Image drag-and-drop for org-mode."
  :group 'org
  :prefix "org-download-")

(defcustom org-download-method 'directory
  "The way images should be stored."
  :type '(choice
          (const :tag "Directory" directory)
          (const :tag "Attachment" attach))
  :group 'org-download)

(defcustom org-download-image-dir nil
  "If set, images will be stored in this directory instead of \".\".
See `org-download--dir-1' for more info."
  :type '(choice
          (const :tag "Default" nil)
          (string :tag "Directory"))
  :group 'org-download)
(make-variable-buffer-local 'org-download-image-dir)

(defcustom org-download-heading-lvl 0
  "Heading level to be used in `org-download--dir-2'."
  :group 'org-download)
(make-variable-buffer-local 'org-download-heading-lvl)

(defcustom org-download-backend t
  "Method to use for downloading."
  :type '(choice
          (const :tag "wget" "wget \"%s\" -O \"%s\"")
          (const :tag "curl" "curl \"%s\" -o \"%s\"")
          (const :tag "url-retrieve" t))
  :group 'org-download)

(defcustom org-download-timestamp "_%Y-%m-%d_%H:%M:%S"
  "This `format-time-string'-style string will be appended to the file name.
Set this to \"\" if you don't want time stamps."
  :type 'string
  :group 'org-download)

(defcustom org-download-screenshot-method "gnome-screenshot -a -f %s"
  "The tool to capture screenshots."
  :type '(choice
          (const :tag "gnome-screenshot" "gnome-screenshot -a -f %s")
          (const :tag "scrot" "scrot -s %s")
          (const :tag "gm" "gm import %s"))
  :group 'org-download)

(defcustom org-download-image-width 0
  "When non-zero add #+attr_html: :width tag to the image."
  :type 'integer
  :group 'org-download)

(defun org-download-get-heading (lvl)
  "Return the heading of the current entry's LVL level parent."
  (save-excursion
    (let ((cur-lvl (org-current-level)))
      (unless (= cur-lvl 1)
        (org-up-heading-all (- (1- (org-current-level)) lvl)))
      (substring-no-properties
       (org-get-heading)))))

(defun org-download--dir-1 ()
  "Return the first part of the directory path for `org-download--dir'.
It's `org-download-image-dir', unless it's nil.  Then it's \".\"."
  (or org-download-image-dir "."))

(defun org-download--dir-2 ()
  "Return the second part of the directory path for `org-download--dir'.
Unless `org-download-heading-lvl' is nil, it's the name of the current
`org-download-heading-lvl'-leveled heading.  Otherwise it's \"\"."
  (and org-download-heading-lvl
       (org-download-get-heading
        org-download-heading-lvl)))

(defun org-download--dir ()
  "Return the directory path for image storage.

The path is composed from `org-download--dir-1' and `org-download--dir-2'.
The directory is created if it didn't exist before."
  (let* ((part1 (org-download--dir-1))
         (part2 (org-download--dir-2))
         (dir (if part2
                  (format "%s/%s" part1 part2)
                part1)))
    (unless (file-exists-p dir)
      (make-directory dir t))
    dir))

(defun org-download--fullname (link)
  "Return the file name where LINK will be saved to.

It's affected by `org-download-timestamp' and `org-download--dir'."
  (let ((filename
         (file-name-nondirectory
          (car (url-path-and-query
                (url-generic-parse-url link)))))
        (dir (org-download--dir)))
    (format "%s/%s%s.%s"
            dir
            (file-name-sans-extension filename)
            (format-time-string org-download-timestamp)
            (file-name-extension filename))))

(defun org-download--image (link filename)
  "Save LINK to FILENAME asynchronously and show inline images in current buffer."
  (when (string-match "^file://\\(.*\\)" link)
    (setq link (url-unhex-string (match-string 1 link))))
  (cond ((file-exists-p link)
         (org-download--image/command "cp \"%s\" \"%s\"" link filename))
        ((eq org-download-backend t)
         (org-download--image/url-retrieve link filename))
        (t
         (org-download--image/command org-download-backend link filename))))

(defun org-download--image/command (command link filename)
  "Using COMMAND, save LINK to FILENAME.
COMMAND is a format-style string with two slots for LINK and FILENAME."
  (require 'async)
  (async-start
   `(lambda() (shell-command
          ,(format command link
                   (expand-file-name filename))))
   (lexical-let ((cur-buf (current-buffer)))
     (lambda(x)
       (with-current-buffer cur-buf
         (org-display-inline-images))))))

(defun org-download--image/url-retrieve (link filename)
  "Save LINK to FILENAME using `url-retrieve'."
  (url-retrieve
   link
   (lambda (status filename buffer)
     ;; Write current buffer to FILENAME
     ;; and update inline images in BUFFER
     (let ((err (plist-get status :error)))
       (if err (error
                "\"%s\" %s" link
                (downcase (nth 2 (assq (nth 2 err) url-http-codes))))))
     (delete-region
      (point-min)
      (progn
        (re-search-forward "\n\n" nil 'move)
        (point)))
     (let ((coding-system-for-write 'no-conversion))
       (write-region nil nil filename nil nil nil 'confirm))
     (with-current-buffer buffer
       (org-display-inline-images)))
   (list
    (expand-file-name filename)
    (current-buffer))
   nil t))

(defun org-download-yank ()
  "Call `org-download-image' with current kill."
  (interactive)
  (org-download-image (current-kill 0)))

(defun org-download-screenshot ()
  "Capture screenshot and insert the resulting file.
The screenshot tool is determined by `org-download-screenshot-method'."
  (interactive)
  (let ((link "/tmp/screenshot.png"))
    (shell-command (format org-download-screenshot-method link))
    (org-download-image link)))

(defun org-download-image (link)
  "Save image at address LINK to `org-download--dir'."
  (interactive "sUrl: ")
  (let ((filename
         (if (eq org-download-method 'attach)
             (let ((org-download-image-dir (progn (require 'org-attach)
                                                  (org-attach-dir t)))
                   org-download-heading-lvl)
               (org-download--fullname link))
           (org-download--fullname link))))
    (when (image-type-from-file-name filename)
      (org-download--image link filename)
      (when (eq org-download-method 'attach)
        (org-attach-attach filename nil 'none))
      (if (looking-back "^[ \t]+")
          (delete-region (match-beginning 0) (match-end 0))
        (newline))
      (insert (format "#+DOWNLOADED: %s @ %s\n%s [[%s]]"
                      link
                      (format-time-string "%Y-%m-%d %H:%M:%S")
                      (if (= org-download-image-width 0)
                          ""
                        (format "#+attr_html: :width %dpx\n" org-download-image-width))
                      filename))
      (org-display-inline-images))))

(defun org-download--at-comment-p ()
  "Check if current line begins with #+DOWLOADED:."
  (save-excursion
    (move-beginning-of-line nil)
    (looking-at "#\\+DOWNLOADED:")))

(defun org-download-delete ()
  "Delete inline image link on current line, and the file that it points to."
  (interactive)
  (cond ((org-download--at-comment-p)
         (delete-region (line-beginning-position)
                        (line-end-position))
         (org-download--delete (line-beginning-position)
                               nil
                               1))
        ((region-active-p)
         (org-download--delete (region-beginning)
                               (region-end))
         (delete-region (region-beginning)
                        (region-end)))

        (t (org-download--delete (line-beginning-position)
                                 (line-end-position)))))

(defun org-download--delete (beg end &optional times)
  "Delete inline image links and the files they point to between BEG and END.

When TIMES isn't nil, delete only TIMES links."
  (unless times
    (setq times most-positive-fixnum))
  (save-excursion
    (goto-char beg)
    (while (and (>= (decf times) 0)
                (re-search-forward "\\[\\[\\([^]]*\\)\\]\\]" end t))
      (let ((str (match-string-no-properties 1)))
        (delete-region (match-beginning 0)
                       (match-end 0))
        (when (file-exists-p str)
          (delete-file str))))))

(defun org-download-dnd (uri action)
  "When in `org-mode' and URI points to image, download it.
Otherwise, pass URI and ACTION back to dnd dispatch."
  (if (eq major-mode 'org-mode)
      ;; probably shouldn't redirect
      (unless (org-download-image uri)
        (message "not an image URL"))
    ;; redirect to someone else
    (let ((dnd-protocol-alist
           (rassq-delete-all
            'org-download-dnd
            (copy-alist dnd-protocol-alist))))
      (dnd-handle-one-url nil action uri))))

(defun org-download-enable ()
  "Enable org-download."
  (unless (eq (cdr (assoc "^\\(https?\\|ftp\\|file\\|nfs\\)://" dnd-protocol-alist))
              'org-download-dnd)
    (setq dnd-protocol-alist
          `(("^\\(https?\\|ftp\\|file\\|nfs\\)://" . org-download-dnd) ,@dnd-protocol-alist))))

(defun org-download-disable ()
  "Disable org-download."
  (rassq-delete-all 'org-download-dnd dnd-protocol-alist))

(org-download-enable)

(provide 'org-download)

;;; org-download.el ends here