import: switch to URL-safe Base64 for Message-IDs

Hexdigests are too long and shorter Message-IDs are easier
to deal with.

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index 4c007b61..77e74c13 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -401,7 +401,16 @@ sub atfork_child {
 
 sub digest2mid ($) {
         my ($dig) = @_;
-        $dig->clone->hexdigest . '@localhost';
+        my $b64 = $dig->clone->b64digest;
+        # Make our own URLs nicer:
+        # See "Base 64 Encoding with URL and Filename Safe Alphabet" in RFC4648
+        $b64 =~ tr!+/=!-_!d;
+
+        # We can make this more meaningful with a date prefix or other things,
+        # but this is only needed for crap that fails to generate a Message-ID
+        # or reuses one.  In other words, it's usually spammers who hit this
+        # so they don't deserve nice Message-IDs :P
+        $b64 . '@localhost';
 }
 
 1;