- my $mail = Mail::Internet->new(\*STDIN);
- $mail->head->get("message-id") =~ /^<(.*)>$/; # get message-id
- return $1;
+ my $mid = undef;
+ my @headers = ();
+
+ while (<STDIN>) { # collect header lines in @headers
+ push(@headers, $_);
+ last if $_ =~ /^$/;
+ }
+ my $head = Mail::Header->new(\@headers);
+ $mid = $head->get("message-id") or undef;
+
+ if ($mid) { # Message-ID header found
+ $mid =~ /^<(.*)>$/; # extract message id
+ $mid = $1;
+ } else { # Message-ID header not found, synthesize a message id
+ # based on SHA1, as notmuch would do. See:
+ # https://git.notmuchmail.org/git/notmuch/blob/HEAD:/lib/sha1.c
+ my $sha = Digest::SHA->new(1);
+ $sha->add($_) foreach(@headers);
+ $sha->addfile(\*STDIN);
+ $mid = 'notmuch-sha1-' . $sha->hexdigest;
+ }
+
+ return $mid;