use strict;
use warnings;

package Sport::Analytics::SRS;

return 1; # madule returns true for successfull load

sub new {
    my ($class, %params) = @_;

    # parameter validation here. die on failure.

    # Test for PDL
    $params{havePDL} = eval {
        require 'PDL';
        PDL->import ();
        1;
    };

    return bless \%params, $class;
}


sub srs_full_matrix {
    my ($self, %options) = @_;

    die "The module PDL must be available for srs_full_matrix use."
        if !$self->{havePDL};

    $options{epsilon} ||= 0.001;
    $options{maxiter} ||= 1000000;
    $self->{srs} = $self->{mov}->copy ();

    my $oldsrs = $self->{srs}->copy ();
    my $delta  = 10.0;
    my $iter   = 0;

    while ($delta > $options{epsilon} and $iter < $options{maxiter}) {
        my $wt   = 1.0 / sumover ($self->{played});
        my $prod = $self->{srs} x $self->{played};
        my $sos  = $wt * $prod;
        $self->{srs} = $self->{mov} + $sos;
        $delta = max (abs ($self->{srs} - $oldsrs));
        $oldsrs = $self->{srs}->copy ();
        $iter++;
    }

    print "iter  = $iter\n"                if $options{debug};
    print "epsilon  = $options{epsilon}\n" if $options{debug};
    printf "delta = %7.4f\n", $delta if $options{debug};
    my $offset = sum ($self->{srs});
    $self->{srs} -= ($offset / $self->{mov}->nelem);
    return $self->{srs}->slice (":,(0)");
}


sub loadData {
    my ($self, $games) = @_;
    for (@$games) {
        my ($visitor, $visit_score, $home_team, $home_score) = split "\,", $_;
        my $diff = $home_score - $visit_score;
        $self->{team}{$visitor}{games_played}++;
        $self->{team}{$home_team}{games_played}++;
        $self->{team}{$visitor}{points} -= $diff;
        $self->{team}{$home_team}{points} += $diff;
        push @{$self->{team}{$visitor}{played}},   $home_team;
        push @{$self->{team}{$home_team}{played}}, $visitor;
    }
    my $total_team = scalar keys %{$self->{team}};

    $self->{played} = zeroes ($total_team, $total_team);
    $self->{mov} = zeroes ($total_team);
    my $ii = 0;
    for (sort keys %{$self->{team}}) {
        my $team_diff =
            $self->{team}{$_}{points} / $self->{team}{$_}{games_played};
        $self->{team_map}{$_} = $ii;
        $self->{mov}->set ($ii, $team_diff);
        $ii++;
    }

    for (keys %{$self->{team}}) {
        my $i = $self->{team_map}{$_};
        for my $opp (@{$self->{team}{$_}{played}}) {
            my $j = $self->{team_map}{$opp};
            my $a = $self->{played}->at ($i, $j);
            $a++;
            $self->{played}->set ($i, $j, $a);
        }
    }
}