;;; gnus-html.el --- Quoted-Printable functions

;; Copyright (C) 2010  Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Keywords: html, web

;; 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:

;; The idea is to provide a simple, fast and pretty minimal way to
;; render HTML (including links and images) in a buffer, based on an
;; external HTML renderer (i.e., w3m).

;;; Code:

(defcustom gnus-html-cache-directory (nnheader-concat gnus-directory "html-cache/")
  "Where Gnus will cache images it downloads from the web."
  :group 'gnus-art
  :type 'directory)

(defcustom gnus-html-cache-size 500000000
  "The size of the Gnus image cache."
  :group 'gnus-art
  :type 'integer)

;;;###autoload
(defun gnus-article-html (handle)
  (let ((article-buffer (current-buffer)))
    (save-restriction
      (narrow-to-region (1- (point)) (point))
      (save-excursion
	(set-buffer (car handle))
	(call-process-region (point-min) (point-max)
			     "w3m" 
			     nil article-buffer nil
			     "-halfdump"
			     "-T" "text/html"))
      (gnus-html-wash-tags))))

(defun gnus-html-wash-tags ()
  (let (tag parameters string start end images)
    ;;(subst-char-in-region (point-min) (point-max) ?_ ? )
    (goto-char (point-min))
    (while (re-search-forward "<\\([^ />]+\\)\\([^>]*\\)>" nil t)
      (setq tag (match-string 1)
	    parameters (match-string 2)
	    start (match-beginning 0))
      (delete-region start (point))
      (when (search-forward (concat "</" tag ">"))
	(delete-region (match-beginning 0) (match-end 0)))
      (setq end (point))
      (cond
       ;; Fetch and insert a picture.
       ((equal tag "img_alt")
	(when (string-match "src=\"\\([^\"]+\\)" parameters)
	  (setq parameters (match-string 1 parameters))
	  (when (or (null mm-w3m-safe-url-regexp)
		    (string-match mm-w3m-safe-url-regexp parameters))
	    (let ((file (gnus-html-image-id parameters)))
	      (if (file-exists-p file)
		  ;; It's already cached, so just insert it.
		  (progn
		    (put-image (create-image file) (point))
		    ;; Delete the ALT text.
		    (delete-region start end))
		;; We don't have it, so schedule it for fetching
		;; asynchronously.
		(push (list parameters
			    (set-marker (make-marker) start)
			    (point-marker))
		      images))))))
       ;; Add a link.
       ((equal tag "a")
	(when (string-match "href=\"\\([^\"]+\\)" parameters)
	  (setq parameters (match-string 1 parameters))
	  (gnus-article-add-button start end
				   'browse-url parameters)
	  (let ((overlay (gnus-make-overlay start end)))
	    (gnus-overlay-put overlay 'evaporate t)
	    (gnus-overlay-put overlay 'gnus-button-url parameters)
	    (when gnus-article-mouse-face
	      (gnus-overlay-put overlay 'mouse-face gnus-article-mouse-face)))))
       ;; Whatever.  Just ignore the tag.
       (t
	))
      (goto-char start))
    (when images
      (gnus-html-schedule-image-fetching (current-buffer) images))))

(defun gnus-html-schedule-image-fetching (buffer images)
  (let* ((url (caar images))
	 (process (start-process
		   "images" nil "curl"
		   "-s" "--create-dirs"
		   "-o" (gnus-html-image-id url)
		   url)))
    (set-process-sentinel process 'gnus-html-curl-sentinel)
    (set-process-plist process (list 'images images
				     'buffer buffer))))

(defun gnus-html-image-id (url)
  (expand-file-name (sha1 url) gnus-html-cache-directory))

(defun gnus-html-curl-sentinel (process event)
  (when (string-match "finished" event)
    (let* ((images (getf (process-plist process) 'images))
	   (buffer (getf (process-plist process) 'buffer))
	   (spec (pop images))
	   (file (gnus-html-image-id (car spec))))
      (when (file-exists-p file)
	(save-excursion
	  (set-buffer buffer)
	  (let ((buffer-read-only nil))
	    (delete-region (cadr spec) (caddr spec))
	    (put-image (create-image file) (cadr spec)))))
      (when images
	(gnus-html-schedule-image-fetching buffer images)))))

(defun gnus-html-prune-cache ()
  (let ((total-size 0)
	files)
    (dolist (file (directory-files gnus-html-cache-directory t nil t))
      (let ((attributes (file-attributes file)))
	(unless (nth 0 attributes)
	  (incf total-size (nth 7 attributes))
	  (push (list (time-to-seconds (nth 5 attributes))
		      (nth 7 attributes) file)
		files))))
    (when (> total-size gnus-html-cache-size)
      (setq files (sort files (lambda (f1 f2)
				(< (car f1) (car f2)))))
      (dolist (file files)
	(when (> total-size gnus-html-cache-size)
	  (decf total-size (cadr file))
	  (delete-file (nth 2 file)))))))

;;; gnus-html.el ends here