/**
 * 双射类
 * 在给定自然数空间一对一完全映射，可逆运算，不可猜解
 * @author liuxu
 *
 */
class Bijective
{
	static private $defaultPrime = '85310501873';//请使用个位为"3"、"7"、"9"的质数

	static public function getRandPrime()
	{
		return self::getMinPrime(rand(100000,900000)*100000+rand(100000,900000));
	}

	static public function getMinPrime($min)
	{
		$number = $min;
		while(true)
		{
			if(self::isPrime($number)) break;
			$number++;
		}

		return $number;
	}

	static public function isPrime($number)
	{
		$sqrt = intval(bcsqrt($number,0));
		for($i=2;$i<=$sqrt;$i++)
		{
			if(bcmod($number,$i)==='0')
			{
				return false;
			}
		}

		return true;
	}

	static public function mod($number,$len=10)
	{
		return bcmod(bcmul($number,self::$defaultPrime,0),bcpow(10,$len,0));
	}

	static public function loop($number,$len=8)
	{

		$min = $prev = $number;
		for($i=1;;$i++)
		{
			$next = self::mod($prev,$len);
			if($next==$number) break;
			$min = min($min,$next);
			$prev = $next;
		}

		$offset = ( $min % $i ) + 1;
		for($j=0;$j<$offset;$j++)
		{
			$number = self::mod($number,$len);
		}

		return $number;
	}

	static public function insanity($number,$len=10)
	{
		$number = self::mod($number,$len);
		$number = str_pad($number,$len,'0',STR_PAD_LEFT);

		$numberList = str_split($number,6);
		foreach($numberList as $key=>$value)
		{
			$numberList[$key] = str_pad(self::loop($value,strlen($value)),strlen($value),'0',STR_PAD_LEFT);
		}

		$number = implode('',$numberList);

		return $number;
	}

}