From 460e6a8d32b845fbebd51d0f07485ec349083abd Mon Sep 17 00:00:00 2001
From: SqrtMinusOne <thexcloud@gmail.com>
Date: Sat, 2 Jul 2022 14:55:58 +0300
Subject: [PATCH] feat(mail): move signature when necessary

---
 .emacs.d/mail.el | 38 +++++++++++++++++++++++
 Mail.org         | 80 +++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 117 insertions(+), 1 deletion(-)

diff --git a/.emacs.d/mail.el b/.emacs.d/mail.el
index 1d9676c..d905ea1 100644
--- a/.emacs.d/mail.el
+++ b/.emacs.d/mail.el
@@ -93,3 +93,41 @@
         (CMS
          (sign)
          (encrypt))))
+
+(setq my/message-signature-on-top '("@etu.ru"))
+
+(defun my/message-insert-signature-need-on-top ()
+  (let ((parts (split-string
+                (string-join
+                 (list
+                  (message-fetch-field "to")
+                  (message-fetch-field "cc")
+                  (message-fetch-field "bcc"))
+                 ", ")
+                ", ")))
+    (and
+     (seq-some
+      (lambda (rule)
+        (seq-some
+         (lambda (part)
+           (string-match-p rule part))
+         parts))
+      my/message-signature-on-top)
+     t)))
+
+(defun my/message-maybe-fix-signature (&rest _)
+  (when (my/message-insert-signature-need-on-top)
+    (save-excursion
+      (goto-char (point-min))
+      (when (re-search-forward message-signature-separator nil t)
+        (move-beginning-of-line 0)
+        (kill-region (point) (point-max)))
+      (message-goto-body)
+      (when (re-search-forward (rx "sign=pgpmime") nil t)
+        (forward-line))
+      (insert (current-kill 0))
+      (insert "\n\n")
+      (set-buffer-modified-p nil))))
+
+(with-eval-after-load 'notmuch-mua
+  (advice-add #'notmuch-mua-reply :after #'my/message-maybe-fix-signature))
diff --git a/Mail.org b/Mail.org
index d70cb32..ec73c58 100644
--- a/Mail.org
+++ b/Mail.org
@@ -450,7 +450,8 @@ Finally the proper notmuch settings:
             (lambda () (display-line-numbers-mode 0))))
 #+end_src
 
-The file to which this is tangled is read in the init.el.
+The file is read in =init.el=.
+
 ** Saved filters and keybindings
 I want to have the saved filters available in both notmuch interface as as keybindings. So a bit more of abusing org tables.
 
@@ -543,6 +544,83 @@ And the following does the same for my general.el definer:
          (sign)
          (encrypt))))
 #+end_src
+** Tuning signature
+By default, =message.el= inserts the signature at the bottom of the message, like this:
+
+#+begin_example
+<message text>
+
+Person <person@mail.org> writes:
+
+> Stuff
+
+--
+Yours,
+me
+#+end_example
+
+This creates issues with certain email clients. For instance, MS Exchange often just cuts the text at =Person <person@mail.org>....=, so there's no way to see the signature from the UI.
+
+What's more, MS Exchange, Gmail and other such clients add the signature before the quotation block, like that:
+
+#+begin_example
+<message text>
+
+--
+Yours,
+me
+
+Person <person@mail.org> writes:
+
+> Stuff
+#+end_example
+
+So here I modifiy the citation function to insert the signature like in the second example for certain cases.
+
+FIrst, determine whether it is necessary to do so:
+#+begin_src emacs-lisp
+(setq my/message-signature-on-top '("@etu.ru"))
+
+(defun my/message-insert-signature-need-on-top ()
+  (let ((parts (split-string
+                (string-join
+                 (list
+                  (message-fetch-field "to")
+                  (message-fetch-field "cc")
+                  (message-fetch-field "bcc"))
+                 ", ")
+                ", ")))
+    (and
+     (seq-some
+      (lambda (rule)
+        (seq-some
+         (lambda (part)
+           (string-match-p rule part))
+         parts))
+      my/message-signature-on-top)
+     t)))
+#+end_src
+
+Then advice the =notmuch-mua-reply= function:
+#+begin_src emacs-lisp
+(defun my/message-maybe-fix-signature (&rest _)
+  (when (my/message-insert-signature-need-on-top)
+    (save-excursion
+      (goto-char (point-min))
+      (when (re-search-forward message-signature-separator nil t)
+        (move-beginning-of-line 0)
+        (kill-region (point) (point-max)))
+      (message-goto-body)
+      (when (re-search-forward (rx "sign=pgpmime") nil t)
+        (forward-line))
+      (insert (current-kill 0))
+      (insert "\n\n")
+      (set-buffer-modified-p nil))))
+
+(with-eval-after-load 'notmuch-mua
+  (advice-add #'notmuch-mua-reply :after #'my/message-maybe-fix-signature))
+#+end_src
+
 * mailcap
 mailcap file is a file which defines how to read to different MIME types. Notmuch also uses it, so why not keep it here.