exercise: Clock
version: 1
plan: 57
subs: new time add_minutes subtract_minutes
tests: |-
  foreach (@{$C_DATA->{cases}}) {
    foreach (@{$_->{cases}}) {
      if ($_->{property} eq 'create') {
        is Clock->new($_->{input})->time, $_->{expected}, $_->{description};
      }

      elsif ($_->{property} eq 'add' || $_->{property} eq 'subtract') {
        my $clock = Clock->new({
          hour   => $_->{input}{hour},
          minute => $_->{input}{minute},
        });
        if ($_->{property} eq 'subtract') { $clock->subtract_minutes($_->{input}{value}) }
        elsif ($_->{property} eq 'add'  ) { $clock->add_minutes(     $_->{input}{value}) }
        is $clock->time, $_->{expected}, $_->{description};
      }

      elsif ($_->{property} eq 'equal') {
        ok $_->{expected} ==
          (Clock->new($_->{input}{clock1})->time eq Clock->new($_->{input}{clock2})->time), $_->{description};
      }
    }
  }

  is Clock->new({hour => 0, minute => 0})->add_minutes(65)->time, '01:05', 'add_minutes method can be chained';
  is Clock->new({hour => 0, minute => 0})->subtract_minutes(65)->time, '22:55', 'subtract_minutes method can be chained';
  
stub: |-
  sub new {
    my ($class, $attributes) = @_;
    return bless $attributes, $class;
  }

  sub time {
    my ($self) = @_;
  }

  sub add_minutes {
    my ($self, $amount) = @_;
  }

  sub subtract_minutes {
    my ($self, $amount) = @_;
  }
example: |-
  use POSIX;

  sub new {
    my ($class, $attributes) = @_;
    my $self = {
      hour   => $attributes->{hour} || 0,
      minute => $attributes->{minute} || 0,
    };
    return bless($self, $class)->BUILD;
  }

  sub time {
    my ($self) = @_;
    return sprintf '%02d:%02d', $self->{hour}, $self->{minute};
  }

  sub add_minutes {
    my ($self, $amount) = @_;
    $self->{minute} += $amount;
    return $self->BUILD;
  }

  sub subtract_minutes {
    my ($self, $amount) = @_;
    return $self->add_minutes(-$amount);
  }

  sub BUILD {
    my ($self) = @_;
    $self->{hour} = ( $self->{hour} + floor($self->{minute} / 60) ) % 24;
    $self->{minute} %= 60;
    return $self;
  }