use strict;
use warnings;
use DBI;

package foosball;

sub db_connect {
	my $dbh = DBI->connect("dbi:Pg:dbname=foosball;host=127.0.0.1", "foosball", "cleanrun", {AutoCommit => 0});
	$dbh->{RaiseError} = 1;
	return $dbh;
}

sub find_single_rating {
	my ($dbh, $username, $limit) = @_;
	my ($age, $rating, $rd) = $dbh->selectrow_array('SELECT EXTRACT(EPOCH FROM (CURRENT_TIMESTAMP-ratetime)), rating, rd FROM single_rating WHERE username=? '.$limit.' ORDER BY ratetime DESC LIMIT 1',
		undef, $username);
	$rd = apply_aging($rd, $age / 86400.0);

	if (!defined($rating)) {
		$rating = 1500;
		$rd = 350;
	}

	return ($rating, $rd);
}

sub find_double_rating {
	my ($dbh, $username, $limit) = @_;
	my ($age, $rating, $rd) = $dbh->selectrow_array('SELECT EXTRACT(EPOCH FROM (CURRENT_TIMESTAMP-ratetime)), rating, rd FROM double_rating WHERE username=? '.$limit.'ORDER BY ratetime DESC LIMIT 1',
		undef, $username);
	$rd = apply_aging($rd, $age / 86400.0);
	
	if (!defined($rating)) {
		$rating = 1500;
		$rd = 350;
	}

	return ($rating, $rd);
}

sub combine_ratings {
	my ($rating1, $rd1, $rating2, $rd2) = @_;

	my $rating_team = 0.5 * ($rating1 + $rating2);
	my $rd_team = sqrt($rd1 * $rd1 + $rd2 * $rd2) / sqrt(2.0);
	return ($rating_team, $rd_team);
}

sub create_user_if_not_exists {
	my ($dbh, $username) = @_;
	my $count = $dbh->selectrow_array('SELECT count(*) FROM users WHERE username=?',
		undef, $username);
	return if ($count > 0);
	$dbh->do('INSERT INTO users (username) VALUES (?)',
		undef, $username);
	$dbh->do('INSERT INTO single_rating (username,ratetime,rating,rd) VALUES (?,CURRENT_TIMESTAMP,1500.0,350.0)',
		undef, $username);
	$dbh->do('INSERT INTO double_rating (username,ratetime,rating,rd) VALUES (?,CURRENT_TIMESTAMP,1500.0,350.0)',
		undef, $username);
	return $dbh;
}

# c=8 => RD=50 moves to RD=350 over approx. five years
our $c = 8;

sub apply_aging {
	my ($rd, $age) = @_;
	$rd = sqrt($rd*$rd + $c * $c * ($age / 86400.0));
	$rd = 350.0 if ($rd > 350.0);
	return $rd;
}

sub calc_rating {
	my ($rating1, $rd1, $rating2, $rd2, $score1, $score2) = @_;
	my $result = `/srv/foosball.sesse.net/foosrank $rating1 $rd1 $rating2 $rd2 $score1 $score2`;
	chomp $result;
	my ($newr1, $newrd1) = split / /, $result;

	$newrd1 = 30.0 if ($newrd1 < 30.0);

	return ($newr1, $newrd1);
}

1;
