[RFC PATCH v2] gnus: Add piem-gnus-mid-to-thread

[Xinglu Chen <public@yoctocell.xyz>]

Inserts a string of the whole thread in mbox format.
---
Changes from v1

- Add safety check for major mode and message id before trying to generate
the mbox file
- Escape "^From" in the body to prevent ambiguity

 piem-gnus.el | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/piem-gnus.el b/piem-gnus.el
index 5f10be8..828ce1f 100644
--- a/piem-gnus.el
+++ b/piem-gnus.el
@@ -55,8 +55,38 @@
             (match-string 1 mid)
           mid)))))
 
-;; If there is an easy way to generate an mbox for a thread in Gnus, a
-;; function for `piem-mid-to-thread-functions' should be defined.
+(defun piem-gnus-mid-to-thread (mid)
+  (when (and (derived-mode-p 'gnus-summary-mode)
+	     (string-equal (substring
+			    (mail-header-id (gnus-summary-article-header))
+			    1 -1)	; Remove "<" and ">"
+			   mid))
+    (save-excursion
+      ;; Cursor has to be at the root of the thread
+      (gnus-summary-refer-parent-article most-positive-fixnum)
+      (let ((articles (gnus-summary-articles-in-thread))
+	    message
+	    ;; Just show raw message
+	    (gnus-have-all-headers t)
+	    gnus-article-prepare-hook
+	    gnus-article-decode-hook
+	    gnus-display-mime-function
+	    gnus-break-pages)
+	(mapc (lambda (article)
+		(gnus-summary-display-article article)
+		(push (format
+		       "From mboxrd@z Thu Jan  1 00:00:00 1970\n%s\n"
+		       (replace-regexp-in-string ; From-munge
+			"^From "
+			"^>From "
+			(with-current-buffer gnus-article-buffer
+			  (buffer-substring-no-properties
+			   (point-min)
+			   (point-max)))))
+		      message))
+	      articles)
+	(lambda ()
+	  (insert (apply #'concat (nreverse message))))))))
 
 (defun piem-gnus-am-ready-mbox ()
   "Return a function that inserts an am-ready mbox.
@@ -97,10 +127,12 @@ the mode if ARG is omitted or nil."
       (progn
         (add-hook 'piem-am-ready-mbox-functions #'piem-gnus-am-ready-mbox)
         (add-hook 'piem-get-inbox-functions #'piem-gnus-get-inbox)
-        (add-hook 'piem-get-mid-functions #'piem-gnus-get-mid))
+        (add-hook 'piem-get-mid-functions #'piem-gnus-get-mid)
+	(add-hook 'piem-mid-to-thread-functions #'piem-gnus-mid-to-thread))
     (remove-hook 'piem-am-ready-mbox-functions #'piem-gnus-am-ready-mbox)
     (remove-hook 'piem-get-inbox-functions #'piem-gnus-get-inbox)
-    (remove-hook 'piem-get-mid-functions #'piem-gnus-get-mid)))
+    (remove-hook 'piem-get-mid-functions #'piem-gnus-get-mid)
+    (remove-hook 'piem-mid-to-thread-functions #'piem-gnus-mid-to-thread)))
 
 ;;; piem-gnus.el ends here
 (provide 'piem-gnus)

base-commit: 57f802b2a43ac64c28a5a9ddb9da0afaf910975e
-- 
2.29.2