mu4e-view.el

;;; mu4e-view.el -- part of mu4e, the mu mail user agent
;;
;; Copyright (C) 2011-2012 Dirk-Jan C. Binnema

;; Author: Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
;; Maintainer: Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>

;; 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:

;; In this file we define mu4e-view-mode (+ helper functions), which is used for
;; viewing e-mail messages

;;; Code:
(require 'mu4e-utils)    ;; utility functions
(require 'mu4e-vars)
(require 'mu4e-mark)
(require 'mu4e-proc)
(require 'mu4e-compose)
(require 'mu4e-actions)

;; we prefer the improved fill-region
(require 'filladapt nil 'noerror)
(require 'comint)

;; the message view
(defgroup mu4e-view nil
  "Settings for the message view."
  :group 'mu4e)

(defcustom mu4e-view-fields
  '(:from :to  :cc :subject :flags :date :maildir :attachments)
  "Header fields to display in the message view buffer. For the
complete list of available headers, see `mu4e-header-names'."
  :type (list 'symbol)
  :group 'mu4e-view)

(defcustom mu4e-view-date-format "%c"
  "Date format to use in the message view, in the format of
  `format-time-string'."
  :type 'string
  :group 'mu4e-view)

(defcustom mu4e-view-show-addresses t
  "Whether to show e-mail addresses for contacts in address-fields,
  if names are available as well (note that the e-mail addresses
  are still available as a tooltip."
  :type 'boolean
  :group 'mu4e-view)

(defcustom mu4e-view-wrap-lines nil
  "Whether to automatically wrap lines in the body of messages when
viewing them. Note that wrapping does not work well with all
messages, but you can always toggle between wrapped/unwrapped
display with `mu4e-view-toggle-wrap-lines (default keybinding: <w>)."
  :group 'mu4e-view)

(defcustom mu4e-view-wrap-lines nil
  "Whether to automatically wrap lines in the body of messages when
viewing them. Note that wrapping does not work well with all
messages, but you can always toggle between wrapped/unwrapped
display with `mu4e-view-toggle-wrap-lines (default keybinding: <w>)."
  :group 'mu4e-view)


(defcustom mu4e-view-hide-cited nil
  "Whether to automatically hide cited parts of messages (as
determined by the presence of '> ' at the beginning of the
line). Note that you can always toggle between hidden/unhidden
display with `mu4e-view-toggle-hide-cited (default keybinding:
<w>)."
  :group 'mu4e-view)


(defvar mu4e-view-actions
  '( ("capture message" ?c mu4e-action-capture-message)
     ("view as pdf"     ?p mu4e-action-view-as-pdf))
  "List of actions to perform on messages in view mode. The actions
are of the form:
   (NAME SHORTCUT FUNC)
where:
* NAME is the name of the action (e.g. \"Count lines\")
* SHORTCUT is a one-character shortcut to call this action
* FUNC is a function which receives a message plist as an argument.")

(defvar mu4e-view-attachment-actions
  '( ("open-with" ?w mu4e-view-open-attachment-with)
     ("in-emacs"  ?e mu4e-view-open-attachment-emacs)
     ("pipe"      ?| mu4e-view-pipe-attachment))
  "List of actions to perform on message attachments. The actions
are of the form:
   (NAME SHORTCUT FUNC)
where:
    * NAME is the name of the action (e.g. \"Count lines\")
    * SHORTCUT is a one-character shortcut to call this action
    * FUNC is a function which receives two arguments: the message
      plist and the attachment number.")
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


;; some buffer-local variables
(defvar mu4e~view-headers-buffer nil
  "*internal* Headers buffer connected to this view.")

(defvar mu4e~view-lines-wrapped nil "*internal* Whether lines are wrapped.")
(defvar mu4e~view-cited-hidden nil "*internal* Whether cited lines are hidden.")


(defun mu4e-view-message-with-msgid (msgid)
  "View message with MSGID. This is meant for external programs
wanting to show specific messages - for example, `mu4e-org'."
  (mu4e~proc-view msgid))

(defun mu4e-view-message-text (msg)
  "Return the message to display (as a string), based on the MSG
plist."
  (concat
    (mapconcat
      (lambda (field)
	(let ((fieldname (cdr (assoc field mu4e-header-names)))
	       (fieldval (plist-get msg field)))
	  (case field
	    (:subject  (mu4e~view-construct-header fieldname fieldval))
	    (:path     (mu4e~view-construct-header fieldname fieldval))
	    (:maildir  (mu4e~view-construct-header fieldname fieldval))
	    (:flags    (mu4e~view-construct-header fieldname
			 (if fieldval (format "%S" fieldval) "")))
	    ;; contact fields
	    (:to       (mu4e~view-construct-contacts msg field))
	    (:from     (mu4e~view-construct-contacts msg field))
	    (:cc       (mu4e~view-construct-contacts msg field))
	    (:bcc      (mu4e~view-construct-contacts msg field))

	    ;; if we (`user-mail-address' are the From, show To, otherwise,
	    ;; show From
	    (:from-or-to
	      (let* ((from (plist-get msg :from))
		      (from (and from (cdar from))))
		(if (and from (string-match mu4e-user-mail-address-regexp from))
		  (mu4e~view-construct-contacts msg :to)
		  (mu4e~view-construct-contacts msg :from))))
	    ;; date
	    (:date
	      (let ((datestr
		      (when fieldval (format-time-string mu4e-view-date-format
				       fieldval))))
		(if datestr (mu4e~view-construct-header fieldname datestr) "")))
	    ;; size
	    (:size
	      (let* (size (mu4e-view-size msg)
		      (sizestr (when size (format "%d bytes" size))))
		(if sizestr (mu4e~view-construct-header fieldname sizestr))))
	    ;; attachments
	    (:attachments (mu4e~view-construct-attachments msg))
	    (t               (error "Unsupported field: %S" field)))))
      mu4e-view-fields "")
    "\n"
    (mu4e-body-text msg)))


(defun mu4e-view (msg headersbuf &optional refresh)
  "Display the message MSG in a new buffer, and keep in sync with HDRSBUF.
'In sync' here means that moving to the next/previous message in
the the message view affects HDRSBUF, as does marking etc.

REFRESH is for re-showing an already existing message.

As a side-effect, a message that is being viewed loses its 'unread'
marking if it still had that."
  (let ((buf (get-buffer-create mu4e~view-buffer-name)))
    (with-current-buffer buf
      (mu4e-view-mode)
      (let ((inhibit-read-only t))
	(setq ;; buffer local
	  mu4e~view-msg msg
	  mu4e~view-headers-buffer headersbuf
	  mu4e~view-buffer buf)

	(erase-buffer)
	(insert (mu4e-view-message-text msg))

	(switch-to-buffer buf)
	(goto-char (point-min))

	(mu4e~view-fontify-cited)
	(mu4e~view-fontify-footer)
	(mu4e~view-make-urls-clickable)

	(unless refresh
	  ;; if we're showing the message for the first time, use the values of
	  ;; user-settable variables `mu4e~view-wrap-lines' and
	  ;; `mu4e~view-hide-cited' to determine whether we should wrap/hide
	  (when mu4e~view-lines-wrapped (mu4e~view-wrap-lines))
	  (when mu4e~view-cited-hidden  (mu4e~view-hide-cited))
	  ;; no use in trying to set flags again
	  (mu4e~view-mark-as-read-maybe))))))


(defun mu4e~view-construct-header (key val &optional dont-propertize-val)
    "Return header KEY with value VAL if VAL is non-nil. If
DONT-PROPERTIZE-VAL is non-nil, do not add text-properties to VAL."
    (if val
      (with-temp-buffer
	(insert (propertize key 'face 'mu4e-view-header-key-face) ": "
	  (if dont-propertize-val
	    val
	    (propertize val 'face 'mu4e-view-header-value-face)) "\n")
	;; temporarily set the fill column <margin> positions to the right, so
	;; we can indent following lines with positions
	(let*((margin 1) (fill-column (- fill-column margin)))
	  (fill-region (point-min) (point-max))
	  (goto-char (point-min))
	  (while (and (zerop (forward-line 1)) (not (looking-at "^$")))
	    (indent-to-column margin)))
	(buffer-string))
      ""))

(defun mu4e~view-construct-contacts (msg field)
  "Add a header for a contact field (ie., :to, :from, :cc, :bcc)."
  (let* ((lst (plist-get msg field))
	  (fieldname (cdr (assoc field mu4e-header-names)))
	  (contacts
	    (and lst
	      (mapconcat
		(lambda(c)
		  (let ((name (car c)) (email (cdr c)))
		    (propertize
		      (if name
			(if mu4e-view-show-addresses
			  (format "%s <%s>" name email)
			  (format "%s" name))
			(format "%s" email))
		      'help-echo email)))
		lst ", "))))
    (if contacts
      (mu4e~view-construct-header fieldname contacts)
      "")))


(defun mu4e~view-open-save-attach-func (msg attachnum is-open)
  "Return a function that offers to save attachment NUM. If IS-OPEN
is nil, and otherwise open it."
  (lexical-let ((msg msg) (attachnum attachnum) (is-open is-open))
    (lambda ()
      (interactive)
      (if is-open
	(mu4e-view-open-attachment msg attachnum)
	(mu4e-view-save-attachment msg attachnum)))))

;; note -- attachments have an index which is needed for the backend, which does
;; not necessarily follow 1,2,3,4 etc.
(defun mu4e~view-construct-attachments (msg)
  "Display attachment information; the field looks like something like:
   	:attachments ((:index 4 :name \"test123.doc\"
                       :mime-type \"application/msword\" :size 1234))."
  (let* ((id 0)
	  (attstr
	   (mapconcat
	     (lambda (att)
	       (let ( (index (plist-get att :index))
		      (name (plist-get att :name))
		      (size (plist-get att :size))
		      (map (make-sparse-keymap)))
		 (incf id)
		 (define-key map [mouse-2]
		   (mu4e~view-open-save-attach-func msg id nil))
		 (define-key map [?\r]
		   (mu4e~view-open-save-attach-func msg id nil))
		 (define-key map [S-mouse-2]
		   (mu4e~view-open-save-attach-func msg id t))
		 (define-key map (kbd "<S-return>")
		   (mu4e~view-open-save-attach-func msg id t))
		 (concat
		   (propertize (format "[%d]" id) 'face 'mu4e-view-attach-number-face)
		   (propertize name 'face 'mu4e-view-link-face
		     'keymap map 'mouse-face 'highlight)
		   (when (and size (> size 0))
		     (concat (format "(%s)"
			       (propertize (mu4e-display-size size)
				 'face 'mu4e-view-header-key-face)))))))
	     (plist-get msg :attachments) ", ")))
    (unless (zerop id)
      (mu4e~view-construct-header (format "Attachments(%d)" id) attstr t))))


(defvar mu4e-view-mode-map nil
  "Keymap for \"*mu4e-view*\" buffers.")
(unless mu4e-view-mode-map

  (setq mu4e-view-mode-map
    (let ((map (make-sparse-keymap)))

      (define-key map "q" 'mu4e-view-kill-buffer-and-window)

      ;; note, 'z' is by-default bound to 'bury-buffer'
      ;; but that's not very useful in this case
      (define-key map "z" 'mu4e-view-kill-buffer-and-window)

      (define-key map "s" 'mu4e-headers-search)

      (define-key map "b" 'mu4e-headers-search-bookmark)
      (define-key map "B" 'mu4e-headers-search-bookmark-edit-first)

      (define-key map "%" 'mu4e-view-mark-matches)
      (define-key map "t" 'mu4e-view-mark-subthread)
      (define-key map "T" 'mu4e-view-mark-thread)

      (define-key map "j" 'mu4e~headers-jump-to-maildir)

      (define-key map "g" 'mu4e-view-go-to-url)

      (define-key map "F" 'mu4e-compose-forward)
      (define-key map "R" 'mu4e-compose-reply)
      (define-key map "C" 'mu4e-compose-new)
      (define-key map "E" 'mu4e-compose-edit)

      (define-key map "." 'mu4e-view-raw-message)
      (define-key map "|" 'mu4e-view-pipe)
      (define-key map "a" 'mu4e-view-action)

      ;; intra-message navigation
      (define-key map (kbd "SPC") 'scroll-up)
      (define-key map (kbd "<home>")
	#'(lambda () (interactive) (goto-char (point-min))))
      (define-key map (kbd "<end>")
	#'(lambda () (interactive) (goto-char (point-max))))
      (define-key map (kbd "RET")
	#'(lambda () (interactive) (scroll-up 1)))
      (define-key map (kbd "<backspace>")
	#'(lambda () (interactive) (scroll-up -1)))

      ;; navigation between messages
      (define-key map "p" 'mu4e~view-prev-header)
      (define-key map "n" 'mu4e~view-next-header)
      ;; the same
      (define-key map (kbd "<M-down>") 'mu4e~view-next-header)
      (define-key map (kbd "<M-up>") 'mu4e~view-prev-header)

      ;; switching to view mode (if it's visible)
      (define-key map "y" 'mu4e-select-other-view)

      ;; attachments
      (define-key map "e" 'mu4e-view-save-attachment)
      (define-key map "o" 'mu4e-view-open-attachment)
      (define-key map "A" 'mu4e-view-attachment-action)

      ;; marking/unmarking
      (define-key map (kbd "<backspace>") 'mu4e-mark-for-trash)
      (define-key map "d" 'mu4e-view-mark-for-trash)

      (define-key map (kbd "<delete>") 'mu4e-view-mark-for-delete)
      (define-key map (kbd "<deletechar>") 'mu4e-mark-for-delete)
      (define-key map "D" 'mu4e-view-mark-for-delete)
      (define-key map "m" 'mu4e-view-mark-for-move)

      ;; misc
      (define-key map "w" 'mu4e-view-toggle-wrap-lines)
      (define-key map "h" 'mu4e-view-toggle-hide-cited)

      (define-key map "r" 'mu4e-view-refresh)

      ;; next 3 only warn user when attempt in the message view
      (define-key map "u" 'mu4e-view-unmark)
      (define-key map "U" 'mu4e-view-unmark-all)
      (define-key map "x" 'mu4e-view-marked-execute)

      (define-key map "$" 'mu4e-show-log)
      (define-key map "H" 'mu4e-display-manual)

      ;; menu
      (define-key map [menu-bar] (make-sparse-keymap))
      (let ((menumap (make-sparse-keymap "View")))
	(define-key map [menu-bar headers] (cons "View" menumap))

	(define-key menumap [quit-buffer]
	  '("Quit view" . mu4e-view-kill-buffer-and-window))
	(define-key menumap [display-help] '("Help" . mu4e-display-manual))

	(define-key menumap [sepa0] '("--"))
	(define-key menumap [wrap-lines]
	  '("Toggle wrap lines" . mu4e-view-toggle-wrap-lines))
	(define-key menumap [hide-cited]
	  '("Toggle hide cited" . mu4e-view-toggle-hide-cited))
	(define-key menumap [raw-view]
	  '("View raw message" . mu4e-view-raw-message))
	(define-key menumap [pipe]
	  '("Pipe through shell" . mu4e-view-pipe))
	;; (define-key menumap [inspect]
	;;   '("Inspect with guile" . mu4e-inspect-message))

	(define-key menumap [sepa8] '("--"))
	(define-key menumap [open-att]
	  '("Open attachment" . mu4e-view-open-attachment))
	(define-key menumap [extract-att]
	  '("Extract attachment" . mu4e-view-save-attachment))
	(define-key menumap [goto-url]
	  '("Visit URL" . mu4e-view-go-to-url))

	(define-key menumap [sepa1] '("--"))
	(define-key menumap [mark-delete]
	  '("Mark for deletion" . mu4e-view-mark-for-delete))
	(define-key menumap [mark-trash]
	  '("Mark for trash" .  mu4e-view-mark-for-trash))
	(define-key menumap [mark-move]
	  '("Mark for move" . mu4e-view-mark-for-move))

	(define-key menumap [sepa2] '("--"))
	(define-key menumap [compose-new]  '("Compose new" . mu4e-compose-new))
	(define-key menumap [forward]  '("Forward" . mu4e-compose-forward))
	(define-key menumap [reply]  '("Reply" . mu4e-compose-reply))
	(define-key menumap [sepa3] '("--"))

	(define-key menumap [search]  '("Search" . mu4e-headers-search))
	(define-key menumap [jump]  '("Jump to maildir" . mu4e~headers-jump-to-maildir))

	(define-key menumap [sepa4] '("--"))
	(define-key menumap [next]  '("Next" . mu4e~view-next-header))
	(define-key menumap [previous]  '("Previous" . mu4e~view-prev-header)))
      map)))

(fset 'mu4e-view-mode-map mu4e-view-mode-map)


(define-derived-mode mu4e-view-mode special-mode "mu4e:view"
  "Major mode for viewing an e-mail message in mu4e.
\\{mu4e-view-mode-map}."
  (use-local-map mu4e-view-mode-map)

  (make-local-variable 'mu4e~view-headers-buffer)
  (make-local-variable 'mu4e~view-msg)
  (make-local-variable 'mu4e~view-link-map)

  (make-local-variable 'mu4e~view-lines-wrapped)
  (make-local-variable 'mu4e~view-cited-hidden)

  (setq buffer-undo-list t) ;; don't record undo info

  ;; autopair mode gives error when pressing RET
  ;; turn it off
  (when (boundp 'autopair-dont-activate)
    (setq autopair-dont-activate t))

  ;; filladapt is much better than the built-in filling
  ;; esp. with '>' cited parts
  (when (fboundp 'filladapt-mode)
    (filladapt-mode))
  (setq truncate-lines t))


;; we mark messages are as read when we leave the message; i.e., when skipping
;; to the next/previous one, or leaving the view buffer altogether.

(defun mu4e~view-mark-as-read-maybe ()
  "Clear the current message's New/Unread status and set it to
Seen; if the message is not New/Unread, do nothing."
  (when mu4e~view-msg
    (let ((flags (plist-get mu4e~view-msg :flags))
	   (docid (plist-get mu4e~view-msg :docid)))
      ;; is it a new message?
      (when (or (member 'unread flags) (member 'new flags))
	(mu4e~proc-move docid nil "+S-u-N")))))

(defun mu4e~view-fontify-cited ()
  "Colorize message content based on the citation level."
  (save-excursion
    (let ((more-lines t))
      (goto-char (point-min))
      (while more-lines
	;; Get the citation level at point -- i.e., the number of '>'
	;; prefixes, starting with 0 for 'no citation'
	(beginning-of-line 1)
	(let* ((text (re-search-forward "[[:word:]]" (line-end-position 1) t 1))
		(level (or (and text
			     (how-many ">" (line-beginning-position 1) text)) 0))
		(face
		  (cond
		    ((= 0 level) nil) ;; don't do anything
		    ((= 1 level) 'mu4e-cited-1-face)
		    ((= 2 level) 'mu4e-cited-2-face)
		    ((= 3 level) 'mu4e-cited-3-face)
		    ((= 4 level) 'mu4e-cited-4-face)
		    (t           nil))))
	  (when face
	    (add-text-properties (line-beginning-position 1)
	      (line-end-position 1) `(face ,face))))
	(setq more-lines
	  (and (= 0 (forward-line 1))
	    ;; we need to add this weird check below; it seems in some cases
	    ;; `forward-line' continues to return 0, even when at the end, which
	    ;; would lead to an infinite loop
	    (not (= (point-max) (line-end-position)))))))))

(defun mu4e~view-fontify-footer ()
  "Give the message footers a distinctive color."
  (let ((inhibit-read-only t))
    (save-excursion
      ;; give the footer a different color...
      (goto-char (point-min))
      (let ((p (search-forward "\n-- \n" nil t)))
	(when p
	  (add-text-properties p (point-max) '(face mu4e-footer-face)))))))

(defvar mu4e~view-link-map nil
  "*internal* A map of some number->url so we can jump to url by number.")

(defconst mu4e~view-url-regexp
  "\\(https?://[-+a-zA-Z0-9.?_$%/+&#@!~,:;=/()]+\\)"
  "*internal* regexp that matches URLs; match-string 1 will contain
  the matched URL, if any.")

(defun mu4e~view-browse-url-func (url)
  "Return a function that executes `browse-url' with URL."
  (lexical-let ((url url))
    (lambda ()
      (interactive)
      (browse-url url))))


;; this is fairly simplistic...
(defun mu4e~view-make-urls-clickable ()
  "Turn things that look like URLs into clickable things, and
number them so they can be opened using `mu4e-view-go-to-url'."
  (let ((num 0))
    (save-excursion
      (setq mu4e~view-link-map ;; buffer local
	(make-hash-table :size 32 :rehash-size 2 :weakness nil))
      (goto-char (point-min))
      (while (re-search-forward mu4e~view-url-regexp nil t)
	(let ((url (match-string 0))
	       (map (make-sparse-keymap)))
	  (define-key map [mouse-2] (mu4e~view-browse-url-func url))
	  (define-key map [?\r] (mu4e~view-browse-url-func url))
	  (puthash (incf num) url mu4e~view-link-map)
	  (add-text-properties 0 (length url)
	    `(face mu4e-view-link-face
	       mouse-face highlight
	       keymap ,map) url)
	  (replace-match (concat url
			   (propertize (format "[%d]" num)
			     'face 'mu4e-view-url-number-face))))))))



(defun mu4e~view-wrap-lines ()
  "Wrap lines in the message body."
  (save-excursion
    (let ((inhibit-read-only t))
      (goto-char (point-min))
      (when (search-forward "\n\n") ;; search for the message body
	(fill-region (point) (point-max)))
      (setq mu4e~view-lines-wrapped t))))

(defun mu4e~view-hide-cited ()
  "Toggle hiding of cited lines in the message body."
  (save-excursion
    (let ((inhibit-read-only t))
      (goto-char (point-min))
      (flush-lines "^[:blank:]*>")
      (setq mu4e~view-cited-hidden t))))

(defun mu4e~view-headers-move (lines)
  "Move point LINES lines forward (if LINES is positive) or
backward (if LINES is negative). If this succeeds, return the new
docid. Otherwise, return nil."
  (when (buffer-live-p mu4e~view-headers-buffer)
    (with-current-buffer mu4e~view-headers-buffer
      (mu4e~headers-move lines))))

(defun mu4e~view-next-header()(interactive)(mu4e~view-headers-move 1))
(defun mu4e~view-prev-header()(interactive)(mu4e~view-headers-move -1))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; Interactive functions


(defun mu4e-view-toggle-wrap-lines ()
  "Toggle line wrap in the message body."
  (interactive)
  (if mu4e~view-lines-wrapped
    (mu4e-view-refresh)
    (mu4e~view-wrap-lines)))

(defun mu4e-view-toggle-hide-cited ()
  "Toggle hiding of cited lines in the message body."
  (interactive)
  (if mu4e~view-cited-hidden
    (mu4e-view-refresh)
    (mu4e~view-hide-cited)))

(defun mu4e-view-refresh ()
  "Redisplay the current message, without wrapped lines or hidden
citations."
  (interactive)
  (mu4e-view mu4e~view-msg mu4e~view-headers-buffer t)
  (setq
    mu4e~view-lines-wrapped nil
    mu4e~view-cited-hidden nil))

(defun mu4e-view-kill-buffer-and-window ()
  "Quit the message view and return to the headers."
  (interactive)
  (when (buffer-live-p mu4e~view-buffer)
    (with-current-buffer mu4e~view-buffer
      (if (fboundp 'window-parent) ;; window-parent is an emacs24ism
	(if (window-parent)
	  (kill-buffer-and-window)
	  (kill-buffer))
	;; emacs23 hack: trial and error
	(condition-case nil
	  (kill-buffer-and-window)
	  (kill-buffer))))))

(defun mu4e-view-action (&optional msg)
  "Ask user for some action to apply on MSG (or message-at-point,
if nil), then do it. The actions are specified in
`mu4e-view-actions'."
  (interactive)
  (let* ((msg (or msg (mu4e-message-at-point t)))
	  (actionfunc (mu4e-read-option "Action: " mu4e-view-actions)))
    (funcall actionfunc msg)))

(defun mu4e-view-mark-matches ()
    "Ask user for a kind of mark (move, delete etc.), a field to
match and a regular expression to match with. Then, mark all
matching messages with that mark."
  (interactive)
  (when (buffer-live-p mu4e~view-headers-buffer)
    (with-current-buffer mu4e~view-headers-buffer
      (mu4e-headers-mark-matches))))

(defun mu4e-view-mark-thread ()
  "Ask user for a kind of mark (move, delete etc.), and apply it to
all messages in the thread at point in the headers view."
  (interactive)
  (when (buffer-live-p mu4e~view-headers-buffer)
    (with-current-buffer mu4e~view-headers-buffer
      (mu4e-headers-mark-thread))))

(defun mu4e-view-mark-subthread ()
  "Ask user for a kind of mark (move, delete etc.), and apply it to
all messages in the thread at point in the headers view."
  (interactive)
  (when (buffer-live-p mu4e~view-headers-buffer)
    (with-current-buffer mu4e~view-headers-buffer
      (mu4e-headers-mark-subthread))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; attachment handling
(defun mu4e~view-get-attach-num (prompt msg)
  "Ask the user with PROMPT for an attachment number for MSG, and
  ensure it is valid. The number is [1..n] for attachments
  [0..(n-1)] in the message."
  (let* ((attlist (plist-get msg :attachments))
	  (count (length attlist)))
    (when (zerop count) (error "No attachments for this message"))
    (if (= count 1)
      (read-number (mu4e-format "%s: " prompt) 1)
      (read-number (mu4e-format "%s (1-%d): " prompt count)))))

(defun mu4e~view-get-attach (msg attnum)
  "Return the attachment plist in MSG corresponding to attachment
number ATTNUM."
  (let ((attlist (plist-get msg :attachments)))
    (nth (- attnum 1) attlist)))

(defun mu4e-view-save-attachment (&optional msg attnum)
  "Save attachment number ATTNUM (or ask if nil) from MSG (or
message-at-point if nil) to disk."
  (interactive)
  (unless mu4e-attachment-dir
    (error "`mu4e-attachment-dir' is not set"))
  (let* ((msg (or msg (mu4e-message-at-point)))
	  (attnum (or attnum
		    (mu4e~view-get-attach-num "Attachment to save" msg)))
	  (att (mu4e~view-get-attach msg attnum))
	  (path (concat mu4e-attachment-dir "/" (plist-get att :name)))
	  (index (plist-get att :index))
	  (retry t))
    (while retry
      (setq path (expand-file-name (read-string
				     (mu4e-format "Save as ") path)))
      (setq retry
	(and (file-exists-p path)
	  (not (y-or-n-p (mu4e-format "Overwrite '%s'?"))))))
    (mu4e~proc-extract
      'save (plist-get msg :docid) index path)))


(defun mu4e-view-open-attachment (&optional msg attnum)
  "Open attachment number ATTNUM (or ask if nil) from MSG (or
message-at-point if nil)."
  (interactive)
  (let* ((msg (or msg (mu4e-message-at-point)))
	  (attnum (or attnum
		    (mu4e~view-get-attach-num "Attachment to open" msg)))
	  (att (mu4e~view-get-attach msg attnum))
	  (index (plist-get att :index)))
    (mu4e~proc-extract 'open (plist-get msg :docid) index)))


(defun mu4e~temp-action (docid index what &optional param)
  "Open attachment INDEX for message with DOCID, and invoke
ACTION."
  (interactive)
  (mu4e~proc-extract 'temp docid index nil what param))

(defvar mu4e~view-open-with-hist nil
  "History list for the open-with argument.")

(defun mu4e-view-open-attachment-with (msg attachnum &optional cmd)
  "Open MSG's attachment ATTACHNUM with CMD; if CMD is nil, ask
user for it."
  (interactive)
  (let* ((att (mu4e~view-get-attach msg attachnum))
	  (cmd (or cmd
		 (read-string
		   (mu4e-format "Shell command to open it with: ")
		   nil 'mu4e~view-open-with-hist)))
	  (index (plist-get att :index)))
    (mu4e~temp-action (plist-get msg :docid) index "open-with" cmd)))

(defvar mu4e~view-pipe-hist nil
  "History list for the pipe argument.")

(defun mu4e-view-pipe-attachment (msg attachnum &optional pipecmd)
  "Feed MSG's attachment ATTACHNUM through pipe PIPECMD; if
PIPECMD is nil, ask user for it."
  (interactive)
  (let* ((att (mu4e~view-get-attach msg attachnum))
	  (pipecmd (or pipecmd
		     (read-string
		       (mu4e-format "Pipe: ")
		       nil
		       'mu4e~view-pipe-hist)))
	  (index (plist-get att :index)))
    (mu4e~temp-action (plist-get msg :docid) index "pipe" pipecmd)))


(defun mu4e-view-open-attachment-emacs (msg attachnum)
  "Open MSG's attachment ATTACHNUM in the current emacs instance."
  (interactive)
  (let* ((att (mu4e~view-get-attach msg attachnum))
	  (index (plist-get att :index)))
    (mu4e~temp-action (plist-get msg :docid) index "emacs")))


(defun mu4e-view-attachment-action (&optional msg)
  "Ask user what to do with attachments in MSG (or nil to use
message-at-point, then do it. The actions are specified in
`mu4e-view-attachment-actions'."
  (interactive)
  (let* ((msg (or msg (mu4e-message-at-point t)))
	  (actionfunc (mu4e-read-option
			"Action on attachment: "
			mu4e-view-attachment-actions))
	  (attnum (mu4e~view-get-attach-num "Which attachment" msg)))
    (when (and actionfunc attnum)
      (funcall actionfunc msg attnum))))


;; handler-function to handle the response we get from the server when we
;; want to do something with one of the attachments.
(defun mu4e~view-temp-handler (path what param)
  "Handler function for doing things with temp files (ie.,
attachments) in response to a (mu4e~proc-extract 'temp ... )."
  (cond
    ((string= what "open-with")
      ;; 'param' will be the program to open-with
      (start-process "*mu4e-open-with-proc*" "*mu4e-open-with*" param path))
    ((string= what "pipe")
      ;; 'param' will be the pipe command, path the infile for this
      (mu4e-process-file-through-pipe path
	(shell-quote-argument param)))
    ((string= what "emacs")
      (find-file path)
      ;; make the buffer read-only since it usually does not make
	;; sense to edit the temp buffer; use C-x C-q if you insist...
      (setq buffer-read-only t))
      (t (error "Unsupported action %S" what))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;; marking
(defun mu4e~view-mark-set (mark)
  "Set mark on the current messages."
  (unless (buffer-live-p mu4e~view-headers-buffer)
    (error "No headers buffer available"))
  (let ((docid (mu4e-msg-field mu4e~view-msg :docid)))
    (with-current-buffer mu4e~view-headers-buffer
      (if (eq mark 'move)
	(mu4e-mark-for-move-set)
	(mu4e-mark-at-point mark)))))


(defun mu4e~split-view-p ()
  "Return t if we're in split-view, nil otherwise."
  (member mu4e-split-view '(horizontal vertical)))

(defun mu4e-view-unmark-all ()
  "If we're in split-view, unmark all messages. Otherwise, warn
user that unmarking only works in the header list."
  (interactive)
  (if (mu4e~split-view-p)
    (mu4e-mark-unmark-all)
    (mu4e-message "Unmarking needs to be done in the header list view")))

(defun mu4e-view-unmark ()
  "If we're in split-view, unmark message at point. Otherwise, warn
user that unmarking only works in the header list."
  (interactive)
  (if (mu4e~split-view-p)
    (mu4e~view-mark-set 'unmark)
    (mu4e-message "Unmarking needs to be done in the header list view")))

(defun mu4e-view-mark-for-move ()
  "Mark the current message for moving."
  (interactive)
  (mu4e~view-mark-set 'move)
  (mu4e~view-next-header))

(defun mu4e-view-mark-for-trash ()
  "Mark the current message for moving to the trash folder."
  (interactive)
  (mu4e~view-mark-set 'trash)
  (mu4e~view-next-header))

(defun mu4e-view-mark-for-delete ()
  "Mark the current message for deletion."
  (interactive)
  (mu4e~view-mark-set 'delete)
  (mu4e~view-next-header))

(defun mu4e-view-marked-execute ()
  "If we're in split-view, execute the marks. Otherwise, warn user
that execution can only take place in n the header list."
  (interactive)
  (if (mu4e~split-view-p)
    (with-current-buffer mu4e~view-headers-buffer
      (mu4e-mark-execute-all))
    (mu4e-message "Execution needs to be done in the header list view")))

(defun mu4e-view-go-to-url (num)
  "Go to a numbered url."
  (interactive "n[mu4e] Go to url with number: ")
  (let ((url (gethash num mu4e~view-link-map)))
    (unless url (error "Invalid number for URL"))
    (browse-url url)))

(defconst mu4e~view-raw-buffer-name "*mu4e-raw-view*"
  "*internal* Name for the raw message view buffer")

(defun mu4e-view-raw-message ()
  "Display the raw contents of message at point in a new buffer."
  (interactive)
  (let ((path (mu4e-field-at-point :path))
	 (buf (get-buffer-create mu4e~view-raw-buffer-name)))
    (unless (and path (file-readable-p path))
      (error "Not a readable file: %S" path))
    (with-current-buffer buf
      (let ((inhibit-read-only t))
	(erase-buffer)
	(insert-file-contents path)
	(view-mode)
	(goto-char (point-min))))
    (switch-to-buffer buf)))

(defun mu4e-view-pipe (cmd)
  "Pipe the message at point through shell command CMD, and display
the results."
  (interactive "sShell command: ")
  (let ((path (mu4e-field-at-point :path)))
    (mu4e-process-file-through-pipe path cmd)))

(provide 'mu4e-view)