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<?php
function str_last_char(string $s): string
{
	$len = strlen($s);
	return $len ? $s[$len-1] : '';
}

function get_tbs_solution()
{
	if ($solution = GWF_Session::get('tbs_revival_solution'))
	{
		return $solution;
	}
	$solution = GWF_Random::randomKey(16);
	GWF_Session::set('tbs_revival_solution', $solution);
	return $solution;
}

function check_tbs_solution(string $answer)
{
	$solution = get_tbs_solution();
	return strcasecmp($answer, $solution) === 0;
}

define('TBS_CHARSET', 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz');
define('SPACE', '+');
define('IGNORE', ' ');

function get_tbs_diff(string $a, string $b): int
{
	$a = strtolower($a);
	$b = strtolower($b);
	$a = preg_replace('/[^a-z]/', '', $a);
	$b = preg_replace('/[^a-z]/', '', $b);
	$la = strlen($a);
	$lb = strlen($b);
	$min = min([$la, $lb]);
	$diff = 0;
	for ($i = 0; $i < $min; $i++)
	{
		$ca = $a[$i];
		$cb = $b[$i];
		$oa = ord($ca);
		$ob = ord($cb);
		$d1 = abs(strpos(TBS_CHARSET, $ca) - strpos(TBS_CHARSET, $cb));
		$d2 = abs(strpos(TBS_CHARSET, $ca) - strrpos(TBS_CHARSET, $cb));
		$d = min([$d1, $d2]);
		$diff += $d;
	}
	$diff += abs($la - $lb);
	return $diff;
}

function get_tbs_message()
{
	$message = require_once 'secret_message.php';
	$message = trim($message); '';
	$user = GWF_User::getStaticOrGuest();
	if (!$user->isGuest())
	{
		$message = $user->displayUsername() . ", " . $message;
		$solution = get_tbs_solution();
		$message .= 'Solution: ' . $solution;
	}
	return $message;
}

function tbs_encode(string $message, array $carry): array
{
	if ($encoded = GWF_Session::get('tbs_revival_encoded'))
	{
// 		return $encoded;
	}
	$encoded = encode($message, $carry);
	$encoded[0] = tbs_herringed($encoded[0]);
	GWF_Session::set('tbs_revival_encoded', $encoded);
	return $encoded;
}

function tbs_herringed(string $encoded): string
{
	$encoded = preg_replace('/ ([0-9])/', '*$1', $encoded);
	$encoded = preg_replace('/   /', ' / ', $encoded);
	$encoded = preg_replace_callback('/ /', function(array $match){
		return rand(0, 1) ? ' ' : '^';
	}, $encoded);
// 	$encoded = preg_replace('/\\^ /', '^0', $encoded);
// 	$encoded = preg_replace('/\\+ /', '+1', $encoded);
	return $encoded;
}

function _next_word(string $word, string $message, int $i): string
{
	$message = substr($message, $i);
	$matches = null;
	preg_match('/(\w+[^\w]*)/', $message, $matches);
	return $matches[1];
}

function _carry_can_encode(string $carry, string $in)
{
	return ctype_alpha($carry);
}

function _input_is_literal(string $in): bool
{
	return !ctype_alpha($in);
}

### Carrier
### Secret
###-4  04
function _next_char(string $in, string $carry, string $prev, string &$out): bool
{
   	$encodable = false;
   	
   	if ($in === ' ')
   	{
   		$out .= SPACE;
   		$encodable = true;
   	}
   	elseif (_input_is_literal($in))
   	{
   		$out .= $in;
   		$encodable = true;
   	}
   	elseif (!_carry_can_encode($carry, $in))
   	{
   		$out .= IGNORE;
   	}
   	else
   	{
   		# Encodable?
		$diff = get_tbs_diff($in, $carry);
		$encodable = $diff < 9;
		if ($encodable)
		{
			if (strcasecmp($in, $carry) < 0)
			{
				if ($prev !== ' ')
				{
					$out .= IGNORE;
					return false;
				}
				else
				{
					$outpos = strlen($out);
					$out[$outpos - 1] = '-';
				}
			}
		}
		if ($encodable)
		{
			$out .= $diff;
		}
		else
		{
			$out .= IGNORE;
		}
   	}
	return $encodable;
}

function decode(array $carry, string $encoded): string
{
	# @TODO implement ;)
}

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