;; Message mode
;; This is common to Gnus, mu4e, notmuch, etc.
(require 'init-smtpmail)

(setq user-full-name "Pierre Neidhardt"
      mm-default-directory "~/temp"     ; Where to save attachments.
      ;; Don't keep sent e-mail buffer.  (Also see mu4e-conversation-kill-buffer-on-exit.)
      message-kill-buffer-on-exit t
      message-send-mail-function 'smtpmail-send-it
      ;; The following is only useful for sending mail with msmtp?
      mail-specify-envelope-from t
      mail-envelope-from 'header)

;; TODO: Use the following to automatically set the From: field when replying.
;; Might not be necessary.
;; message-alternative-emails

;; Sign messages by default.  TODO: Which method?
(add-hook 'message-setup-hook 'mml-secure-sign-pgpmime)
;; (add-hook 'message-setup-hook 'mml-secure-message-sign-pgpmime)

;; Also crypt to self so that we can read sent e-mails.
(setq mml-secure-openpgp-encrypt-to-self t)

(defun message-recipients ()
  "Return a list of all recipients in the message, looking at TO, CC and BCC.

Each recipient is in the format of `mail-extract-address-components'."
  (mapcan (lambda (header)
            (let ((header-value (message-fetch-field header)))
              (and
               header-value
               (mail-extract-address-components header-value t))))
          '("To" "Cc" "Bcc")))

(defvar ambrevar/trust-threshold '(marignal full ultimate))
(defun ambrevar/trusted-addresses ()
  "Return the list of trusted email addresses in the PGP keyring.
Trust is defined as per `ambrevar/trust-threshold'."
  (let (valid-addresses)
    (dolist (key (epg-list-keys (epg-make-context epa-protocol)) valid-addresses)
      (dolist (user-id (epg-key-user-id-list key))
        (when (memq (epg-user-id-validity user-id) '(marginal full ultimate))
          (push (cadr (mail-extract-address-components (epg-user-id-string user-id)))
                valid-addresses))))))

(defun message-sign-encrypt-if-all-keys-trusted ()
  "Add MML tag to encrypt message when there is a key for each recipient.

Consider adding this function to `message-send-hook' to
systematically send encrypted emails when possible."
  (let* ((recipients (message-recipients))
         (untrusted-recipients (seq-difference recipients (ambrevar/trusted-addresses))))
    (if untrusted-recipients
        (warn "Not encrypting because of untrusted %s" untrusted-recipients)
      (mml-secure-message-sign-encrypt))))

;; TODO: Test and report upstream (Emacs + Notmuch).
(add-hook 'message-send-hook #'message-sign-encrypt-if-all-keys-trusted)

;; Fix replying to GitHub.  TODO: Test!
(defun ambrevar/message-alter-bogus-github-recipients (addrcell)
  "Discard @reply.github.com mail addresses.
ADDRCELL is a cons cell where the car is the mail address and the
cdr is the complete address (full name and mail address)."
  (unless (string-match (rx "@reply.github.com" string-end)
                        (cdr addrcell))
    addrcell))
(setq message-alter-recipients-function 'ambrevar/message-alter-bogus-github-recipients)

(defvar ambrevar/mu4e-compose-fortune-p nil
  "Whether or not to include a fortune in the signature.")
(defun ambrevar/mu4e-add-signature-and-maybe-fortune ()
  "Insert signature using `user-full-name'.
A fortune is appended if `ambrevar/mu4e-compose-fortune-p' is non-nil."
  (require 'functions) ; For `call-process-to-string'.
  (setq mu4e-compose-signature
        (concat
         user-full-name "\n"
         "https://ambrevar.xyz/"
         (when (and ambrevar/mu4e-compose-fortune-p
                    (executable-find "fortune"))
           (concat "\n\n"
                   (ambrevar/call-process-to-string "fortune" "-s"))))))
(add-hook 'message-setup-hook 'ambrevar/mu4e-add-signature-and-maybe-fortune)

(defun ambrevar/mu4e-select-dictionary ()
  "Set dictionary according to the LANGUAGE property of the first
\"To:\" recipient found in the Org contacts file."
  (interactive)
  (let ((addresses (mapcar 'cadr (message-recipients)))
        address-lang-map)
    (setq address-lang-map
          (cl-loop for contact in (org-contacts-filter)
                   ;; The contact name is always the car of the assoc-list
                   ;; returned by `org-contacts-filter'.
                   for language = (cdr (assoc-string "LANGUAGE" (nth 2 contact)))
                   ;; Build the list of the user email addresses.
                   for email-list = (org-contacts-split-property
                                     (or (cdr (assoc-string org-contacts-email-property
                                                            (nth 2 contact))) ""))
                   if (and email-list language)
                   ;; Build an alist of (EMAIL . LANGUAGE).
                   nconc (cl-loop for email in email-list
                                  collect (cons (downcase email) language))))
    (while addresses
      (if (not (assoc (car addresses) address-lang-map))
          (setq addresses (cdr addresses))
        (ispell-change-dictionary (cdr (assoc (car addresses) address-lang-map)))
        (setq addresses nil)))))
(add-hook 'message-setup-hook 'ambrevar/mu4e-select-dictionary)

;; Because it's to tempting to send an e-mail riddled with typos...
(add-hook 'message-setup-hook 'flyspell-mode)


(provide 'init-message)