package Zonemaster::Engine::Nameserver::Cache::RedisCache;

use v5.16.0;
use warnings;

use version; our $VERSION = version->declare("v1.0.0");

use Class::Accessor "antlers";
use Time::HiRes qw[gettimeofday tv_interval];
use List::Util qw( min );

use Zonemaster::LDNS::Packet;
use Zonemaster::Engine::Packet;
use Zonemaster::Engine::Profile;

use base qw( Zonemaster::Engine::Nameserver::Cache );

eval {
    use Data::MessagePack;
    use Redis;
};

if ( $@ ) {
    die "Can't use the Redis cache. Make sure the Data::MessagePack and Redis modules are installed.\n";
}

my $redis;
my $config;
our $object_cache = \%Zonemaster::Engine::Nameserver::Cache::object_cache;

my $REDIS_EXPIRE_DEFAULT = 300; # seconds

has 'redis' => ( is => 'ro' );
has 'config' => ( is => 'ro' );

my $mp = Data::MessagePack->new();

sub new {
    my $proto = shift;
    my $params = shift;
    $params->{address} = $params->{address}->ip;
    if ( exists $object_cache->{ $params->{address} } ) {
        Zonemaster::Engine->logger->add( CACHE_FETCHED => { ip => $params->{address} } );
        return $object_cache->{ $params->{address} };
    } else {
        if (! defined $redis) {
            my $redis_config = Zonemaster::Engine::Profile->effective->get( q{cache} )->{'redis'};
            $redis = Redis->new(server => $redis_config->{server});
            $config = $redis_config;
        }
        $params->{redis} //= $redis;
        $params->{data} //= {};
        $params->{config} //= $config;
        $config->{expire} //= $REDIS_EXPIRE_DEFAULT;
        my $class = ref $proto || $proto;
        my $obj = Class::Accessor::new( $class, $params );

        Zonemaster::Engine->logger->add( CACHE_CREATED => { ip => $params->{address} } );
        $object_cache->{ $params->{address} } = $obj;

        return $obj;
    }
}

sub set_key {
    my ( $self, $hash, $packet ) = @_;
    my $key = "ns:" . $self->address . ":" . $hash;

    # Never cache with answer, NXDOMAIN or NODATA longer than this.
    my $redis_expire = $self->{config}->{expire};

    # If no response or response without answer or SOA in authority,
    # cache this many seconds (e.g. SERVFAIL or REFUSED).
    my $ttl_no_response = 1200;

    my $ttl;

    $self->data->{$hash} = $packet;
    if ( defined $packet ) {
        my $msg = $mp->pack({
            data       => $packet->data,
            answerfrom => $packet->answerfrom,
            timestamp  => $packet->timestamp,
            querytime  => $packet->querytime,
        });
        if ( $packet->answer ) {
            my @rr = $packet->answer;
            $ttl = min( map { $_->ttl } @rr );
        }
        elsif ( $packet->authority ) {
            my @rr = $packet->authority;
            foreach my $r (@rr) {
                if ( $r->type eq 'SOA' ) {
                    $ttl = $r->ttl;
                    last;
                }
            }
        }

        if ( defined( $ttl ) ) {
            $ttl = $ttl < $redis_expire ? $ttl : $redis_expire;
        } else {
            $ttl = $ttl_no_response;
        }

        # Redis requires cache time to be greater than 0 to be stored.
        return if $ttl == 0;
        $self->redis->set( $key, $msg, 'EX', $ttl );
    } else {
        $self->redis->set( $key, '', 'EX', $ttl_no_response );
    }
}

sub get_key {
    my ( $self, $hash ) = @_;
    my $key = "ns:" . $self->address . ":" . $hash;

    if ( exists $self->data->{$hash} ) {
        Zonemaster::Engine->logger->add( MEMORY_CACHE_HIT => { hash => $hash } );
        return ( 1, $self->data->{$hash} );
    } elsif ( $self->redis->exists($key) ) {
        my $fetch_start_time = [ gettimeofday ];
        my $data = $self->redis->get( $key );
        Zonemaster::Engine->logger->add( REDIS_CACHE_HIT => { key => $key } );
        if ( not length($data) ) {
            $self->data->{$hash} = undef;
        } else {
            my $msg = $mp->unpack( $data );
            my $packet = Zonemaster::Engine::Packet->new({ packet => Zonemaster::LDNS::Packet->new_from_wireformat($msg->{data}) });
            $packet->answerfrom( $msg->{answerfrom} );
            $packet->timestamp( $msg->{timestamp} );
            $packet->querytime( $msg->{querytime} );

            $self->data->{$hash} = $packet;
        }
        return ( 1, $self->data->{$hash} );
    }
    Zonemaster::Engine->logger->add( CACHE_MISS => { key => $key } );
    return ( 0, undef )
}

1;

=head1 NAME

Zonemaster::Engine::Nameserver::Cache::RedisCache - global shared caches for nameserver objects

=head1 SYNOPSIS

    This is a global caching layer.

=head1 ATTRIBUTES

Subclass of L<Zonemaster::Engine::Nameserver::Cache>.

=head1 CLASS METHODS

=over

=item new

Construct a new Cache object.

=item set_key($idx, $packet)

Store C<$packet> with key C<$idx>.

=item get_key($idx)

Retrieve C<$packet> (data) at key C<$idx>.

=back

Cache time is the shortest time of TTL in the DNS packet
and cache.redis.expire in the profile. Default value of
cache.redis.expire is 300 seconds.

If there is no TTL value to be used in the DNS packet
(e.g. SERVFAIL or no response), then cache time is fixed
to 1200 seconds instead.

=cut