From af7351e6c33e891344724968f88f3f62d0f3275c Mon Sep 17 00:00:00 2001
From: Kévin Le Gouguec <kevin.legouguec@gmail.com>
Date: Tue, 3 Nov 2020 18:29:44 +0100
Subject: Jot down POC code to retrieve a Message-ID from a URL

Retrieved from:
<https://lists.gnu.org/archive/html/emacs-devel/2020-09/msg02212.html>

(Aka <87eeml80oi.fsf@gmail.com>)
---
 itches/emacs/development.org | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'itches/emacs/development.org')

diff --git a/itches/emacs/development.org b/itches/emacs/development.org
index a1fe3f2..a3e05da 100644
--- a/itches/emacs/development.org
+++ b/itches/emacs/development.org
@@ -46,6 +46,23 @@ trick, e.g.
       &submit=Search!
       &idxname=$LIST
   #+end_example
+  ⇒
+  #+begin_src elisp
+  (defun mhonarc-to-messageid (url)
+    "Retrieve the Message-ID from an article archived on MHonArc."
+    (interactive
+     (list
+      (let* ((default (or (thing-at-point-url-at-point)
+                          (and (derived-mode-p 'eww-mode)
+                               (shr-url-at-point nil))))
+             (prompt (if default
+                         (format "URL? (%s) " default)
+                       "URL? ")))
+        (read-string prompt nil nil default))))
+    (with-current-buffer (url-retrieve-synchronously url)
+      (search-forward-regexp "^<!--X-Message-Id: \\(.+\\) -->$")
+      (message (xml-substitute-numeric-entities (match-string 1)))))
+  #+end_src
 - public-inbox: trivial
 *** TODO HTTP archive → Message-ID
 - <https://lists.gnu.org>: cf. =X-Message-Id= comment in HTML
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