package MAC;

use strict;
use warnings;

use Carp;

sub new
  {
  #constructor. Takes 1 argument besides the Class name, a MAC address separated by colons(:)
  # returns an object ref
  my($class, $mac) = @_;
  my $self = bless([], $class);
  @{$self} = split(':', $mac);
  unless($#{$self} == 5)
    {
    carp "failure to create MAC Object: address not composed of 6 bytes";
    return;
    }
  my $c = 0;
  foreach my $byte (@{$self})
    {
    #check for proper input values
    unless($byte =~ /[0-9a-fA-F]{2}/)
      {
      carp "failure creating MAC Object: invalid address";
      return;
      }
    #convert it to decimal, borrowed straight from the source of Data::Translate
    $byte = ord(unpack("A",  pack("H*", $byte)));
    @{$self}[$c] = $byte;
    $c++;
    }
  return $self;
  }

sub showdec
  {
  #takes no arguments. returns the mac address in decimal format, mostly for reference
  my $self = shift;
  return join(":", @{$self});
  }

sub showhex
  {
  #takes no arguments. returns the mac address in hexadecimal format
  my $self = shift;
  return $self->_dectohex;
  }

sub increase
  {
  #increases the mac address by argument. returns the newly increased address in hexadecimal format
  my($self, $increase) = @_;
  unless($increase =~ /^\d+$/)
    {
    carp "argument to \'increase\' must be a positive integer";
    return;
    }
  $$self[5] += $increase;
  for(my $c = 5; $c >= 1; $c--)
    {
    while($$self[$c] > 255)
      {
      $$self[$c] -= 256;
      $$self[$c - 1] += 1;
      }
    }
  return $self->_dectohex;
  }

sub decrease
  {
  #decreases the mac address by argument. returns the newly decreased address in hexadecimal format
  my($self, $decrease) = @_;
  unless($decrease =~ /^\d+$/)
    {
    carp "argument to \'decrease\' must be a positive integer";
    return;
    }
  $$self[5] -= $decrease;
  for(my $c = 5; $c >= 1; $c--)
    {
    while($$self[$c] < 0)
      {
      $$self[$c] += 256;
      $$self[$c - 1] -= 1;
      }
    }
  return $self->_dectohex;
  }


sub _dectohex
  {
  my $self = shift;
  my @hexmac;
  my $c = 0;
  foreach my $byte (@{$self})
    {
    #convert to hex, this also borrowed (almost) straight from Data::Translate
    $hexmac[$c] = sprintf("%02X", $byte);
    $c++;
    }
  return join(":", @hexmac);
  }
  1;

##</code><code>##

use strict;
use warnings;

use MAC;

my $mac = MAC->new('10:BE:AF:1C:06:1F');

print $mac->showdec . "\n";
print $mac->showhex . "\n";

print $mac->increase(10) . "\n";
print $mac->increase(65536) . "\n";

print $mac->decrease(256) . "\n";
print $mac->decrease(16777216) . "\n";