package Rss2Html::FeedList;
use warnings;
use strict;
use Moose;
use namespace::autoclean;
use DBI;
use Rss2Html::Feed;
use POSIX qw(strftime);

with 'MooseX::Log::Log4perl';


has 'dbh' => (
    is => 'ro',
    writer => '_set_dbh',
);

sub BUILD {
    my ($self, $args) = @_;
    my $dbh = DBI->connect("dbi:Pg:dbname=rss2html", "", "");
    $self->_set_dbh($dbh);
}

sub feeds {
    my ($self) = @_;
    my $dbh = $self->dbh;

    no autovivification qw(fetch);

    my $feeds_sql = $dbh->selectall_arrayref("select * from feeds where active and url is not null", { Slice => {} });
    my @feeds;
    for (@$feeds_sql) {
	push @feeds, Rss2Html::Feed->new(%$_, dbh => $dbh);
    }
    return \@feeds;
}

sub update_adaptive {
    my ($self) = @_;
    my $dbh = $self->dbh;
    my $start = time();

    no autovivification qw(fetch);

    $dbh->begin_work;

    my $feeds = $self->feeds;
    my $seconds_per_week = 86400 * 7;
    for my $feed (@$feeds) {
        $feed->{title} //= "-";
	#print "<p>feed: $feed->{id} $feed->{title}<br/>\n";
	$self->log->info("feed: $feed->{id} $feed->{title}");
	my $now = time();
        my $run_time = $now - $start;
	my $update_time = $now - $feed->{last_update};
        $self->log->info(strftime("%Y-%m-%d %a %H:%M:%S", localtime($feed->{last_update})), " .. ",
                  strftime("%Y-%m-%d %a %H:%M:%S", localtime($now)), ": $update_time seconds");
	#print "\t", "update_time: $update_time<br/>\n";

        # We are guaranteed to have all items which were issued in the last
        # int($feed->{expire} / 7) weeks since we expire only those not seen for
        # more than $feed->{expire} days. Some feeds keep some items for a long
        # time while removing others quite quickly, so statistics for older
        # items may be severely skewed and are not safe to use.
        my $interval = int($feed->{expire} / 7) * 7 * 86400;

        # We measure those weeks backwards from the last update.
        # If we measured from now we would almost always miss the update from
        # exactly 4 weeks ago (one cycle we are too early, the next we are too
        # late).
	my $start = $feed->{last_update} - $interval;
	my $items = $dbh->selectall_arrayref("select * from items where feed_id=? and issued >= ? order by issued",
	                                     { Slice => {} },
					     $feed->{id}, $start,
					    );
	my $first_issued = $items->[0]{issued} // $start;
	my $total_time = $now - $first_issued;
	my $updates_in_interval = 0;
	for my $item (@$items) {
	    my $t = $item->{issued};
	    my $dt1 = $now - $t;
	    my $dt2 = $dt1 % $seconds_per_week;
	    if ($dt2 < $update_time) {
		$updates_in_interval++;
                $self->log->info("found $item->{id} ", strftime("%Y-%m-%d %a %H:%M:%S", localtime($t)));
	    }
	}
        $self->log->info("updates_in_interval: $updates_in_interval");
	$updates_in_interval *= $seconds_per_week / $total_time;  # normalize to one week
        $self->log->info("updates_in_interval: $updates_in_interval");
	$updates_in_interval += $update_time / $seconds_per_week; # add one update per week
        $self->log->info("updates_in_interval: $updates_in_interval");
	#print "\t", "updates_in_interval: $updates_in_interval<br/>\n";
        if ($updates_in_interval > 0.5) {
	    $self->log->info($feed->{url});
	    $self->log->info("need to update " . $feed->{url});
	    $feed->update;
        }
    }
    $dbh->commit;

    $self->log->info("update done");
}


sub cleanup {
    my ($self) = @_;
    my $dbh = $self->dbh;

    my $now = time();
    my $feeds = $dbh->selectall_arrayref("select * from feeds", { Slice => {} });

    for my $feed (@$feeds) {
        my $expire_days = $feed->{expire} // 30;
        my $seen_limit = $now - $expire_days * 86400;
        my $rc = $dbh->do("delete from items where feed_id=? and seen < ?", {}, $feed->{id}, $seen_limit);
        $self->log->info("cleanup of feed $feed->{id} (limit $seen_limit) returned $rc");

        # mark all but the last 100 entries as old, so they aren't shown by default.
        $dbh->do("update items set old=1
                  where id in (select id from items
                               where feed_id=? and (old is null or old != 1)
                               order by issued desc offset 100)",
                 {},
                 $feed->{id});

    }
    # XXX - this shouldn't be necessary anymore, since PostgreSQL enforces foreign key constraints.
    my $rc = $dbh->do("delete from read where not exists (select id from items where id=item_id)");
    $self->log->info("cleanup of read items returned $rc");
}


#---
__PACKAGE__->meta->make_immutable;
1;
# vim: tw=132