#!/usr/bin/env perl

##
## Author......: See docs/credits.txt
## License.....: MIT
##

use strict;
use warnings;

use Digest::SHA qw (sha256);

sub module_constraints { [[0, 256], [16, 16], [-1, -1], [-1, -1], [-1, -1]] }

sub module_generate_hash
{
  my $word = shift;
  my $salt = shift;

  my $digest = sha256 ($salt . $word);

  for (my $i = 0; $i < 10000; $i++)
  {
    $digest = sha256 ($digest);
  }

  my $hash = sprintf ("%s*%s", unpack ("H*", $digest), $salt);

  return $hash;
}

sub module_verify_hash
{
  my $line = shift;

  my $idx = index ($line, ':');

  return unless $idx >= 0;

  my $hash = substr ($line, 0, $idx);
  my $word = substr ($line, $idx + 1);

  my ($digest, $salt) = split '\*', $hash;

  return unless defined $digest;
  return unless defined $salt;

  my $word_packed = pack_if_HEX_notation ($word);

  my $new_hash = module_generate_hash ($word_packed, $salt);

  return ($new_hash, $word);
}

1;