[neomutt] Add keybind to reply based on mailto: link in the body

config/neomutt/extract-reply.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+
+set -euo pipefail
+
+text="$(cat)"
+
+# Extract only the text/html part of the multipart email
+# TODO parse actual encoding instead of defaulting to iso-8859-1
+mailto="$(printf "%s" "$text" \
+    | awk '
+        boundary {
+            if ($0 ~ boundary) {
+                boundary = "";
+                next
+            }
+            print $0
+        }
+
+        /Content-Type: text\/html;/ {
+            boundary=line
+        }
+
+        {
+            line=$0
+        }' \
+    | qprint -d \
+    | iconv -f iso-8859-1 -t utf-8 \
+    | grep -Eo '<a href="mailto:.*?</a>')"
+
+to="$(printf "%s" "$mailto" | sed -En 's/.*mailto:(.*?)\?subject=.*/\1/p')"
+subject="$(printf "%s" "$mailto" | sed -En 's/.*\?subject=(.*?)" .*/\1/p')"
+# TODO extract original To: to emulate use_envelope_from
+
+datadir="${XDG_DATA_HOME:-"$HOME/.local/share"}/neomutt"
+mkdir -p "$datadir"
+
+format_str="unmy_hdr To: Subject:
+my_hdr To: \"%s\"
+my_hdr Subject: \"%s\"
+echo \`rm \"%s\"\`"
+
+printf "$format_str" "$to" "$subject" "$datadir/info.rc" > "$datadir/info.rc"

config/neomutt/keys.rc

@@ -55,6 +55,13 @@ bind pager gh   display-toggle-weed
 bind pager ge   extract-keys
 
 macro pager gu "<pipe-message> urlscan <enter>"
+# Answer emails with a reply address in the body
+# https://unix.stackexchange.com/a/586010/248368
+macro pager gr "<pipe-message> ~/.config/neomutt/extract-reply.sh <enter>\
+                <enter-command>source ~/.local/share/neomutt/info.rc <enter>\
+                <mail><enter><enter><enter>"
+# Use a hook to reset sender and subject just after creating the reply
+send-hook . 'unmy_hdr To: Subject:'
 
 ##########
 # ATTACH #