Date::Biorhythm - a biorhythm calculator

  biorhythm --birthday=1994-10-09

  use Date::Biorhythm;
  my $bio = Date::Biorhythm->new({
    birthday => Date::Calc::Object->new(0, 1970, 1, 1),
    name     => 'Unix',
  });

  my $i = 0;
  my $limit = 365;
  $bio->day(Date::Calc::Object->today);
  while ($i < $limit) {
    print $bio->value('emotional'), "\n";
    $bio->next;
    $i++;
  }

package Date::Biorhythm;

use strict;
use warnings;

use Moose;
use Date::Calc::Object qw(:all);
use Math::Trig;

our $VERSION = '2.2';

our $WAVELENGTH = {
  emotional    => 28,
  intellectual => 33,
  physical     => 23,
};

our $SECONDARY_CYCLES = {
  mastery => 1,
  passion => 1,
  wisdom  => 1,
};

has 'name' => (
  is  => 'rw',
);

has 'birthday' => (
  isa => 'Date::Calc::Object',
  is  => 'rw',
);

has 'day' => (
  isa => 'Date::Calc::Object',
  is  => 'rw',
);

has '__cache' => (
  is  => 'ro',
);

# initializer for constructor
sub BUILD {
  my $self   = shift;
  my $params = shift;

  die "birtday => REQUIRED!" if not defined $params->{birthday};

  $self->{__cache} = {
    emotional    => [],
    intellectual => [],
    physical     => [],
  };
}

# finalizer for destructor
sub DEMOLISH { }

# what day in the cycle are we in?
sub index {
  my ($self, $cycle) = @_;
  my $diff  = $self->day - $self->birthday;
  my $days  = abs($diff);
  return $days % $WAVELENGTH->{$cycle};
}

# return the current amplitude of the cycle as a value between -1 and 1
sub value {
  my ($self, $cycle) = @_;
  my $day   = $self->index($cycle);
  if (exists($SECONDARY_CYCLES->{$cycle})) {
    if ($cycle eq 'mastery') {
      return ($self->value('intellectual') + $self->value('physical'))     / 2;
    } elsif ($cycle eq 'passion') {
      return ($self->value('physical')     + $self->value('emotional'))    / 2;
    } elsif ($cycle eq 'wisdom') {
      return ($self->value('emotional')    + $self->value('intellectual')) / 2;
    }
  } else {
    if (exists($self->{__cache}{$cycle}[$day])) {
      return $self->{__cache}{$cycle}[$day];
    } else {
      return $self->{__cache}{$cycle}[$day] = 
        sin(pi * 2 * ($day / $WAVELENGTH->{$cycle}));
    }
  }
}

# go to the next day
sub next {
  my ($self) = @_;
  $self->{day}++;
}

# go to the previous day
sub prev {
  my ($self) = @_;
  $self->{day}--;
}

1;

__END__