<?php

namespace Badcow\DNS\Rdata;

use Badcow\DNS\Parser\Tokens;

class NSEC implements RdataInterface
{
	use RdataTrait;

	const TYPE = 'NSEC';
	const TYPE_CODE = 47;

	/**
	 * The Next Domain field contains the next owner name (in the canonical
	 * ordering of the zone) that has authoritative data or contains a
	 * delegation point NS RR set.
	 * {@link https://tools.ietf.org/html/rfc4034#section-4.1.1}.
	 *
	 * @var string
	 */
	private $nextDomainName;

	/** @var array */
	private $types = [];


	/**
	 * @return string
	 */
	public function getNextDomainName(): string
	{
		return $this->nextDomainName;
	}


	/**
	 * @param string $nextDomainName
	 */
	public function setNextDomainName(string $nextDomainName): void
	{
		$this->nextDomainName = $nextDomainName;
	}


	/**
	 * @param string $type
	 */
	public function addType(string $type): void
	{
		$this->types[] = $type;
	}


	/**
	 * Clears the types from the RDATA.
	 */
	public function clearTypes(): void
	{
		$this->types = [];
	}


	/**
	 * @return array
	 */
	public function getTypes(): array
	{
		return $this->types;
	}


	/**
	 * {@inheritdoc}
	 */
	public function toText(): string
	{
		return sprintf(
		    '%s %s',
		    $this->nextDomainName,
		    implode(' ', $this->types)
		);
	}


	/**
	 * {@inheritdoc}
	 *
	 * @throws UnsupportedTypeException
	 */
	public function toWire(): string
	{
		return self::encodeName($this->nextDomainName).self::renderBitmap($this->types);
	}


	/**
	 * {@inheritdoc}
	 */
	public static function fromText(string $text): RdataInterface
	{
		$iterator = new \ArrayIterator(explode(Tokens::SPACE, $text));
		$nsec = new self();
		$nsec->setNextDomainName($iterator->current());
		$iterator->next();
		while ($iterator->valid()) {
		    $nsec->addType($iterator->current());
		    $iterator->next();
		}

		return $nsec;
	}


	/**
	 * {@inheritdoc}
	 *
	 * @throws UnsupportedTypeException
	 */
	public static function fromWire(string $rdata, int &$offset = 0, ?int $rdLength = null): RdataInterface
	{
		$nsec = new self();
		$nsec->setNextDomainName(self::decodeName($rdata, $offset));
		$types = self::parseBitmap($rdata, $offset);
		array_map([$nsec, 'addType'], $types);

		return $nsec;
	}


	/**
	 * @param string $rdata
	 * @param int    $offset
	 *
	 * @return string[]
	 *
	 * @throws UnsupportedTypeException
	 * @throws DecodeException
	 */
	public static function parseBitmap(string $rdata, int &$offset): array
	{
		$bytes = unpack('C*', $rdata, $offset);

		if (!is_array($bytes)) {
		    throw new DecodeException(static::TYPE, $rdata);
		}

		$types = [];

		while (count($bytes) > 0) {
		    $mask = '';
		    $window = array_shift($bytes);
		    $len = array_shift($bytes);
		    for ($i = 0; $i < $len; ++$i) {
		        $mask .= str_pad(decbin(array_shift($bytes)), 8, '0', STR_PAD_LEFT);
		    }
		    $offset = 0;
		    while (false !== $pos = strpos($mask, '1', $offset)) {
		        $types[] = Types::getName((int) $window * 256 + $pos);
		        $offset = $pos + 1;
		    }
		}

		return $types;
	}


	/**
	 * @param string[] $types
	 *
	 * @return string
	 *
	 * @throws UnsupportedTypeException
	 */
	public static function renderBitmap(array $types): string
	{
		$blocks = [];

		foreach ($types as $type) {
		    $int = Types::getTypeCode($type);
		    $window = $int >> 8;
		    $int = $int & 0b11111111;
		    $mod = $int % 8;
		    $mask = $blocks[$window] ?? str_repeat("\0", 32);
		    $byteNum = ($int - $mod) / 8;
		    $byte = ord($mask[$byteNum]) | (128 >> $mod);
		    $mask[$byteNum] = chr($byte);
		    $blocks[$window] = $mask;
		}

		$encoded = '';
		foreach ($blocks as $n => $mask) {
		    $mask = rtrim($mask, "\0");
		    $encoded .= chr($n).chr(strlen($mask)).$mask;
		}

		return $encoded;
	}
}
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