;;; org-mu4e -- Support for links to mu4e messages/queries from within org-mode, -*- lexical-binding: t -*-
;;; and for writing message in org-mode, sending them as rich-text
;;
;; Copyright (C) 2012-2016 Dirk-Jan C. Binnema

;; Author: Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
;; Maintainer: Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
;; Keywords: outlines, hypermedia, calendar, mail
;; Version: 0.0

;; This file is not 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:

;;; Code:

;; This should support org-mode versions 6.x. 7.x

;; the 'noerror is just to make sure bytecompilations does not break...
;; FIXME: find a better solution
(require 'org nil 'noerror)
(require 'org-exp nil 'noerror)

(defvar org-export-skip-text-before-1st-heading)
(defvar org-export-htmlize-output-type)
(defvar org-export-preserve-breaks)
(defvar org-export-with-LaTeX-fragments)

(require 'mu4e)

(defgroup org-mu4e nil
  "Settings for the org-mode related functionality in mu4e."
  :group 'mu4e
  :group 'org) 

(defcustom org-mu4e-link-desc-func
  (lambda (msg) (or (plist-get msg :subject) "No subject"))
  "Function that takes a msg and returns a string for the
description part of an org-mode link.

Example usage:

  (defun my-link-descr (msg)
    (let ((subject (or (plist-get msg :subject)
                       \"No subject\"))
          (date (or (format-time-string mu4e-headers-date-format
                    (mu4e-msg-field msg :date))
                    \"No date\")))
      (concat subject \" \" date)))

  (setq org-mu4e-link-desc-func 'my-link-descr)"
  :type 'function
  :group 'org-mu4e)

(defun org-mu4e-store-link ()
  "Store a link to a mu4e query or message."
  (cond
    ;; storing links to queries
    ((eq major-mode 'mu4e-headers-mode)
      (let* ((query (mu4e-last-query))
	      desc link)
	(org-store-link-props :type "mu4e" :query query)
	(setq
	  desc (concat "mu4e:query:" query)
	  link desc)
	(org-add-link-props :link link :description desc)
	link))
      ;; storing links to messages
    ((eq major-mode 'mu4e-view-mode)
      (let* ((msg  (mu4e-message-at-point))
	     (msgid   (or (plist-get msg :message-id) "<none>"))
	     link)
       (org-store-link-props :type "mu4e" :link link
			     :message-id msgid)
       (setq link (concat "mu4e:msgid:" msgid))
       (org-add-link-props :link link
			   :description (funcall org-mu4e-link-desc-func msg))
       link))))

(org-add-link-type "mu4e" 'org-mu4e-open)
(add-hook 'org-store-link-functions 'org-mu4e-store-link)

(defun org-mu4e-open (path)
  "Open the mu4e message (for paths starting with 'msgid:') or run
the query (for paths starting with 'query:')."
  (require 'mu4e)
  (cond
    ((string-match "^msgid:\\(.+\\)" path)
      (mu4e-view-message-with-message-id (match-string 1 path)))
    ((string-match "^query:\\(.+\\)" path)
      (mu4e-headers-search (match-string 1 path) current-prefix-arg))
    (t (mu4e-error "mu4e: unrecognized link type '%s'" path))))




;;; editing with org-mode ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; below, some functions for the org->html conversion
;; based on / inspired by Eric Schulte's org-mime.el
;; Homepage: http://orgmode.org/worg/org-contrib/org-mime.php
;;
;; EXPERIMENTAL
(defun org~mu4e-mime-file (ext path id)
  "Create a file for an attachment."
  (format (concat "<#part type=\"%s\" filename=\"%s\" "
	    "disposition=inline id=\"<%s>\">\n<#/part>\n")
    ext path id))

(defun org~mu4e-mime-multipart (plain html &optional images)
  "Create a multipart/alternative with text/plain and text/html alternatives.
If the html portion of the message includes images, wrap the html
and images in a multipart/related part."
  (concat "<#multipart type=alternative><#part type=text/plain>"
    plain
    (when images "<#multipart type=related>")
    "<#part type=text/html>"
    html
    images
    (when images "<#/multipart>\n")
    "<#/multipart>\n"))

(defun org~mu4e-mime-replace-images (str current-file)
  "Replace images in html files with cid links."
  (let (html-images)
    (cons
     (replace-regexp-in-string ;; replace images in html
      "src=\"\\([^\"]+\\)\""
      (lambda (text)
        (format
         "src=\"cid:%s\""
         (let* ((url (and (string-match "src=\"\\([^\"]+\\)\"" text)
                          (match-string 1 text)))
                (path (expand-file-name
                       url (file-name-directory current-file)))
                (ext (file-name-extension path))
                (id (replace-regexp-in-string "[\/\\\\]" "_" path)))
           (cl-pushnew (org~mu4e-mime-file
			  (concat "image/" ext) path id)
                       html-images
                       :test 'equal)
           id)))
      str)
     html-images)))

(defun org~mu4e-mime-convert-to-html ()
  "Convert the current body to html."
  (unless (fboundp 'org-export-string)
    (mu4e-error "require function 'org-export-string not found."))
  (unless (executable-find "dvipng")
    (mu4e-error "Required program dvipng not found"))
  (let* ((begin
	     (save-excursion
	       (goto-char (point-min))
	       (search-forward mail-header-separator)))
	    (end (point-max))
	    (raw-body (buffer-substring begin end))
	    (tmp-file (make-temp-name (expand-file-name "mail"
					temporary-file-directory)))
	    (body (org-export-string raw-body 'org
		    (file-name-directory tmp-file)))
	    ;; because we probably don't want to skip part of our mail
	    (org-export-skip-text-before-1st-heading nil)
	    ;; because we probably don't want to export a huge style file
	    (org-export-htmlize-output-type 'inline-css)
	    ;; makes the replies with ">"s look nicer
	    (org-export-preserve-breaks t)
	    ;; dvipng for inline latex because MathJax doesn't work in mail
	    (org-export-with-LaTeX-fragments 'dvipng)
	    ;; to hold attachments for inline html images
	    (html-and-images
	      (org~mu4e-mime-replace-images
		(org-export-string raw-body 'html
		  (file-name-directory tmp-file))
		tmp-file))
	    (html-images (cdr html-and-images))
	    (html (car html-and-images)))
      (delete-region begin end)
      (save-excursion
	(goto-char begin)
	(newline)
	(insert (org~mu4e-mime-multipart
		  body html (mapconcat 'identity html-images "\n")))))) 

;; next some functions to make the org/mu4e-compose-mode switch as smooth as
;; possible.
(defun org~mu4e-mime-decorate-headers ()
  "Make the headers visually distinctive (org-mode)."
  (save-excursion
    (goto-char (point-min))
    (let* ((eoh (when (search-forward mail-header-separator)
		  (match-end 0)))
	    (olay (make-overlay (point-min) eoh)))
      (when olay
	(overlay-put olay 'face 'font-lock-comment-face)))))

(defun org~mu4e-mime-undecorate-headers ()
  "Don't make the headers visually distinctive.
\(well, mu4e-compose-mode will take care of that)."
  (save-excursion
    (goto-char (point-min))
    (let* ((eoh (when (search-forward mail-header-separator)
		  (match-end 0))))
      (remove-overlays (point-min) eoh))))

(defvar org-mu4e-convert-to-html nil
  "Whether to do automatic org-mode => html conversion when sending messages.")

(defun org~mu4e-mime-convert-to-html-maybe ()
  "Convert to html if `org-mu4e-convert-to-html' is non-nil.
This function is called when sending a message (from
`message-send-hook') and, if non-nil, will send the message as
the rich-text version of the what is assumed to be an org-mode
body."
  (when org-mu4e-convert-to-html
    (mu4e-message "Converting to html")
    (org~mu4e-mime-convert-to-html)))
 
(defun org~mu4e-mime-switch-headers-or-body ()
  "Switch the buffer to either mu4e-compose-mode (when in headers)
or org-mode (when in the body)."
  (interactive)
  (let* ((sepapoint
	   (save-excursion
	     (goto-char (point-min))
	     (search-forward-regexp mail-header-separator nil t))))
    ;; only do stuff when the sepapoint exist; note that after sending the
    ;; message, this function maybe called on a message with the sepapoint
    ;; stripped. This is why we don't use `message-point-in-header'.
    (when sepapoint
      (cond
	;; we're in the body, but in mu4e-compose-mode?
	;; if so, switch to org-mode
	((and (> (point) sepapoint) (eq major-mode 'mu4e-compose-mode))
	  (org-mode)
	  (add-hook 'before-save-hook
	    (lambda ()
	      (mu4e-error "Switch to mu4e-compose-mode (M-m) before saving."))
	    nil t)
	  (org~mu4e-mime-decorate-headers)
	  (local-set-key (kbd "M-m")
	    (lambda (keyseq)
	      (interactive "kEnter mu4e-compose-mode key sequence: ")
	      (let ((func (lookup-key mu4e-compose-mode-map keyseq)))
		(if func (funcall func) (insert keyseq))))))
	;; we're in the headers, but in org-mode?
	;; if so, switch to mu4e-compose-mode
	((and (<= (point) sepapoint) (eq major-mode 'org-mode))
      	  (org~mu4e-mime-undecorate-headers)
	  (mu4e-compose-mode)
	  (add-hook 'message-send-hook 'org~mu4e-mime-convert-to-html-maybe nil t)))
      ;; and add the hook
      (add-hook 'post-command-hook 'org~mu4e-mime-switch-headers-or-body t t))))


(defun org-mu4e-compose-org-mode ()
  "Pseudo-Minor mode for mu4e-compose-mode, to edit the message
body using org-mode."
  (interactive)
  (unless (member major-mode '(org-mode mu4e-compose-mode))
    (mu4e-error "Need org-mode or mu4e-compose-mode"))
  ;; we can check if we're already in org-mu4e-compose-mode by checking if the
  ;; post-command-hook is set; hackish...but a buffer-local variable does not
  ;; seem to survive buffer switching
  (if (not (member 'org~mu4e-mime-switch-headers-or-body post-command-hook))
    (progn
      (org~mu4e-mime-switch-headers-or-body)
      (mu4e-message
	(concat
	  "org-mu4e-compose-org-mode enabled; "
	  "press M-m before issuing message-mode commands")))
    (progn ;; otherwise, remove crap
      (remove-hook 'post-command-hook 'org~mu4e-mime-switch-headers-or-body t)
      (org~mu4e-mime-undecorate-headers) ;; shut off org-mode stuff
      (mu4e-compose-mode)
      (message "org-mu4e-compose-org-mode disabled"))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(provide 'org-mu4e)

;;; org-mu4e.el ends here