+# Copyright (C) 2015 all contributors <meta@public-inbox.org>
+# License: AGPLv3 or later (https://www.gnu.org/licenses/agpl-3.0.txt)
+package PublicInbox::ExtMsg;
+use strict;
+use warnings;
+use URI::Escape qw(uri_escape_utf8);
+use PublicInbox::Hval;
+use PublicInbox::MID qw/mid_compress mid2path/;
+
+sub ext_msg {
+ my ($ctx) = @_;
+ my $pi_config = $ctx->{pi_config};
+ my $listname = $ctx->{listname};
+ my $mid = $ctx->{mid};
+ my $cmid = mid_compress($mid);
+
+ eval { require PublicInbox::Search };
+ my $have_xap = $@ ? 0 : 1;
+ my @nox;
+
+ foreach my $k (keys %$pi_config) {
+ $k =~ /\Apublicinbox\.([A-Z0-9a-z-]+)\.url\z/ or next;
+ my $list = $1;
+ next if $list eq $listname;
+
+ my $git_dir = $pi_config->{"publicinbox.$list.mainrepo"};
+ defined $git_dir or next;
+
+ my $url = $pi_config->{"publicinbox.$list.url"};
+ defined $url or next;
+
+ $url =~ s!/+\z!!;
+
+ # try to find the URL with Xapian to avoid forking
+ if ($have_xap) {
+ my $doc_id = eval {
+ my $s = PublicInbox::Search->new($git_dir);
+ $s->find_unique_doc_id('mid', $cmid);
+ };
+ if ($@) {
+ # xapian not configured for this repo
+ } else {
+ # maybe we found it!
+ return r302($url, $cmid) if (defined $doc_id);
+
+ # no point in trying the fork fallback if we
+ # know Xapian is up-to-date but missing the
+ # message in the current repo
+ next;
+ }
+ }
+
+ # queue up for forking after we've tried Xapian on all of them
+ push @nox, { git_dir => $git_dir, url => $url };
+ }
+
+ # Xapian not installed or configured for some repos
+ my $path = "HEAD:" . mid2path($cmid);
+
+ foreach my $n (@nox) {
+ my @cmd = ('git', "--git-dir=$n->{git_dir}", 'cat-file',
+ '-t', $path);
+ my $pid = open my $fh, '-|';
+ defined $pid or die "fork failed: $!\n";
+
+ if ($pid == 0) {
+ open STDERR, '>', '/dev/null'; # ignore errors
+ exec @cmd or die "exec failed: $!\n";
+ } else {
+ my $type = eval { local $/; <$fh> };
+ close $fh;
+ if ($? == 0 && $type eq "blob\n") {
+ return r302($n->{url}, $cmid);
+ }
+ }
+ }
+
+ # Fall back to external repos
+
+ [404, ['Content-Type'=>'text/plain'], ['Not found']];
+}
+
+# Redirect to another public-inbox which is mapped by $pi_config
+sub r302 {
+ my ($url, $mid) = @_;
+ $url .= '/' . uri_escape_utf8($mid) . '/';
+ [ 302,
+ [ 'Location' => $url, 'Content-Type' => 'text/plain' ],
+ [ "Redirecting to\n$url\n" ] ]
+}
+
+1;