#!perl

use strict;

my(@santa);
my($total,$x,$y,$found,$old);
my(%gift);
my($name, $name2, $email, $email2);

while(<>) {
  chomp;
  m/::/ && push(@santa, $_);
}

my $mail     = "/usr/lib/sendmail -t -oi -odq";
my $mailfrom = "kris.kringle\@north.pole";
my $subject  = "Your Kris Kringle Recipient";

## Give everyone a present from a random person:
$total=0; srand;
for $y (@santa) {
  $found=0;
  $total++;
  while (!$found) {
    $x = $santa[rand @santa];
    $y eq $x && next; ## No presents to self!
    

    ## What if the only person left is yourself? This solves that:
    if ($total == @santa && !$gift{$y}) { 
      ## Switch with another!
      $old = $gift{$x};
      $gift{$x}=$y;
      $gift{$y}=$old;
      last;
    }

    $gift{$x} && next; ## No more than one present per person
    $gift{$x}=$y; $found++;
  }
}

## Now we send out the email:
for $y (@santa) {
  ($name, $email)   = split(/::/, $y);
  ($name2, $email2) = split(/::/, $gift{$y});

  open(MAIL, "|$mail $email") || die "Could not open $mail: $!\n";
  print MAIL <<"NORTHPOLE";
From: $mailfrom
To: "$name" <$email>
Subject: $subject

$subject is: $name2 ($email2)

K.K.

Please do NOT reply! 'I' am a program:
NORTHPOLE

  open(SELF, $0) || die "Could not open $0: $!\n";
  while(<SELF>) { print MAIL; }
  close(SELF) || die "Could not close $0: $!\n";
  close(MAIL) || die "Could not close $0: $!\n";
}
exit;