;;; mu4e-message.el -- part of mu4e, the mu mail user agent
;;
;; Copyright (C) 2012-2016 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:

;; Functions to get data from mu4e-message plist structure

;;; Code:
(eval-when-compile (byte-compile-disable-warning 'cl-functions))

(require 'mu4e-vars)
(require 'mu4e-utils)

(require 'cl)
(require 'html2text)


(defcustom mu4e-html2text-command
  (if (fboundp 'shr-insert-document) 'mu4e-shr2text 'html2text)
  
  "Either a shell command or a function that converts from html to plain text.

If it is a shell-command, the command reads html from standard
input and outputs plain text on standard output. If you use the
htmltext program, it's recommended you use \"html2text -utf8
-width 72\". Alternatives are the python-based html2markdown, w3m
and on MacOS you may want to use textutil.

It can also be a function, which takes the current buffer in html
as input, and transforms it into html (like the `html2text'
function).

In both cases, the output is expected to be in UTF-8 encoding.

Newer emacs has the shr renderer, and when its available,
conversion defaults `mu4e-shr2text'; otherwise, the default is
emacs' built-in `html2text' function."
  :type '(choice string function)
  :group 'mu4e-view)

(defcustom mu4e-view-prefer-html nil
  "Whether to base the body display on the html-version.
If the e-mail message has no html-version the plain-text version
is always used."
  :type 'boolean
  :group 'mu4e-view)

(defcustom mu4e-view-html-plaintext-ratio-heuristic 5
  "Ratio between the length of the html and the plain text part
below which mu4e will consider the plain text part to be 'This
messages requires html' text bodies."
  :type 'integer
  :group 'mu4e-view)


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defsubst mu4e-message-field-raw (msg field)
  "Retrieve FIELD from message plist MSG.
FIELD is one of :from, :to, :cc, :bcc, :subject, :data,
:message-id, :path, :maildir, :priority, :attachments,
:references, :in-reply-to, :body-txt, :body-html

Returns `nil' if the field does not exist.

A message plist looks something like:
\(:docid 32461
 :from ((\"Nikola Tesla\" . \"niko@example.com\"))
 :to ((\"Thomas Edison\" . \"tom@example.com\"))
 :cc ((\"Rupert The Monkey\" . \"rupert@example.com\"))
 :subject \"RE: what about the 50K?\"
 :date (20369 17624 0)
 :size 4337
 :message-id \"6BDC23465F79238C8233AB82D81EE81AF0114E4E74@123213.mail.example.com\"
 :path  \"/home/tom/Maildir/INBOX/cur/133443243973_1.10027.atlas:2,S\"
 :maildir \"/INBOX\"
 :priority normal
 :flags (seen)
 :attachments
     ((:index 2 :name \"photo.jpg\" :mime-type \"image/jpeg\" :size 147331)
      (:index 3 :name \"book.pdf\" :mime-type \"application/pdf\" :size 192220))
 :references  (\"6BDC23465F79238C8384574032D81EE81AF0114E4E74@123213.mail.example.com\"
 \"6BDC23465F79238203498230942D81EE81AF0114E4E74@123213.mail.example.com\")
 :in-reply-to \"6BDC23465F79238203498230942D81EE81AF0114E4E74@123213.mail.example.com\"
 :body-txt \"Hi Tom, ...\"
\)).
Some notes on the format:
- The address fields are lists of pairs (NAME . EMAIL), where NAME can be nil.
- The date is in format emacs uses in `current-time'
- Attachments are a list of elements with fields :index (the number of
  the MIME-part), :name (the file name, if any), :mime-type (the
  MIME-type, if any) and :size (the size in bytes, if any).
- Messages in the Headers view come from the database and do not have
  :attachments, :body-txt or :body-html fields. Message in the
  Message view use the actual message file, and do include these fields."
  ;; after all this documentation, the spectacular implementation
  (if msg
    (plist-get msg field)
    (mu4e-error "message must be non-nil")))

(defsubst mu4e-message-field (msg field)
  "Retrieve FIELD from message plist MSG.
Like `mu4e-message-field-nil', but will sanitize `nil' values:
- all string field except body-txt/body-html: nil -> \"\"
- numeric fields + dates                    : nil -> 0
- all others                                : return the value
Thus, function will return nil for empty lists, non-existing body-txt or body-html."
  (let ((val (mu4e-message-field-raw msg field)))
    (cond
      (val
	val)   ;; non-nil -> just return it
      ((member field '(:subject :message-id :path :maildir :in-reply-to))
	"")    ;; string fields except body-txt, body-html: nil -> ""
      ((member field '(:body-html :body-txt))
	val)
      ((member field '(:docid :size))
	0)     ;; numeric type: nil -> 0
      (t
	val)))) ;; otherwise, just return nil

(defsubst mu4e-message-has-field (msg field)
  "Return t if MSG contains FIELD, nil otherwise."
  (plist-member msg field))

(defsubst mu4e-message-at-point (&optional noerror)
  "Get the message s-expression for the message at point in either
the headers buffer or the view buffer, or nil if there is no such
message. If optional NOERROR is non-nil, do not raise an error when
there is no message at point."
  (let ((msg (or (get-text-property (point) 'msg) mu4e~view-msg)))
    (if msg
      msg
      (unless noerror (mu4e-warn "No message at point")))))

(defsubst mu4e-message-field-at-point (field)
  "Get the field FIELD from the message at point.
This is equivalent to:
  (mu4e-message-field (mu4e-message-at-point) FIELD)."
  (mu4e-message-field (mu4e-message-at-point) field))

(defun mu4e-message-body-text (msg)
  "Get the body in text form for this message.
This is either :body-txt, or if not available, :body-html converted
to text, using `mu4e-html2text-command' is non-nil, it will use
that. Normally, thiss function prefers the text part, but this can
be changed by setting `mu4e-view-prefer-html'."
  (let* ((txt (mu4e-message-field msg :body-txt))
	  (html (mu4e-message-field msg :body-html))
	  (body
	    (cond
	      ;; does it look like some text? ie., if the text part is more than
          ;; mu4e-view-html-plaintext-ratio-heuristic times shorter than the
          ;; html part, it should't be used
          ;; This is an heuristic to guard against 'This messages requires
          ;; html' text bodies.
	      ((and (> (* mu4e-view-html-plaintext-ratio-heuristic
                      (length txt)) (length html))
		 ;; use html if it's prefered, unless there is no html
		 (or (not mu4e-view-prefer-html) (not html)))
		txt)
	      ;; otherwise, it there some html?
	      (html
		(with-temp-buffer
		  (insert html)
		  (cond
		    ((stringp mu4e-html2text-command)
		      (let* ((tmp-file (mu4e-make-temp-file "html")))
			(write-region (point-min) (point-max) tmp-file)
			(erase-buffer)
			(call-process-shell-command mu4e-html2text-command tmp-file t t)
			(delete-file tmp-file)))
		    ((functionp mu4e-html2text-command)
		      (funcall mu4e-html2text-command))
		    (t (mu4e-error "Invalid `mu4e-html2text-command'")))
		  (buffer-string))
                )
	      (t ;; otherwise, an empty body
		""))))
    ;; and finally, remove some crap from the remaining string; it seems
    ;; esp. outlook lies about its encoding (ie., it says 'iso-8859-1' but
    ;; really it's 'windows-1252'), thus giving us these funky chars. here, we
    ;; either remove them, or replace with 'what-was-meant' (heuristically)
    (with-temp-buffer
      (insert body)
      (goto-char (point-min))
      (while (re-search-forward "[
 ’]" nil t)
	(replace-match
	  (cond
	    ((string= (match-string 0) "’") "'")
	    (t		                       ""))))
      (buffer-string))))

(defun mu4e-message-contact-field-matches (msg cfield rx)
  "Checks whether any of the of the contacts in field
CFIELD (either :to, :from, :cc or :bcc, or a list of those) of
msg MSG matches (with their name or e-mail address) regular
expressions RX. If there is a match, return non-nil; otherwise
return nil. RX can also be a list of regular expressions, in
which case any of those are tried for a match."
  (if (and cfield (listp cfield))
    (or (mu4e-message-contact-field-matches msg (car cfield) rx)
      (mu4e-message-contact-field-matches msg (cdr cfield) rx))
    (when cfield
      (if (listp rx)
	;; if rx is a list, try each one of them for a match
	(find-if
	  (lambda (a-rx) (mu4e-message-contact-field-matches msg cfield a-rx))
	  rx)
	;; not a list, check the rx
	(find-if
	  (lambda (ct)
	    (let ((name (car ct)) (email (cdr ct)))
	      (or
		(and name  (string-match rx name))
		(and email (string-match rx email)))))
	  (mu4e-message-field msg cfield))))))

(defun mu4e-message-contact-field-matches-me (msg cfield)
  "Checks whether any of the of the contacts in field
CFIELD (either :to, :from, :cc or :bcc) of msg MSG matches *me*,
that is, any of the e-mail address in
`mu4e-user-mail-address-list'. Returns the contact cell that
matched, or nil."
  (find-if
    (lambda (cc-cell)
      (member-if
	(lambda (addr)
	  (string= (downcase addr) (downcase (cdr cc-cell))))
	mu4e-user-mail-address-list))
    (mu4e-message-field msg cfield)))

(defsubst mu4e-message-part-field  (msgpart field)
  "Get some field in a message part; a part would look something like:
  (:index 2 :name \"photo.jpg\" :mime-type \"image/jpeg\" :size 147331)."
  (plist-get msgpart field))

;; backward compatibility ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defalias 'mu4e-msg-field 'mu4e-message-field)
(defalias 'mu4e-body-text 'mu4e-message-body-text) ;; backward compatibility

(defun mu4e-field-at-point (field)
  "Get FIELD (a symbol, see `mu4e-header-info') for the message at
point in eiter the headers buffer or the view buffer."
  (plist-get (mu4e-message-at-point) field))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


(defun mu4e-shr2text ()
  "Html to text using the shr engine; this can be used in
`mu4e-html2text-command' in a new enough emacs. Based on code by
Titus von der Malsburg."
  (interactive)
  (let ((dom (libxml-parse-html-region (point-min) (point-max)))
	 ;; When HTML emails contain references to remote images,
	 ;; retrieving these images leaks information. For example,
	 ;; the sender can see when I openend the email and from which
	 ;; computer (IP address). For this reason, it is preferrable
	 ;; to not retrieve images.
	 ;; See this discussion on mu-discuss:
	 ;; https://groups.google.com/forum/#!topic/mu-discuss/gr1cwNNZnXo
	 (shr-inhibit-images t))
    (erase-buffer)
    (shr-insert-document dom)
    (goto-char (point-min))))

(provide 'mu4e-message)