<?php

namespace Badcow\DNS\Rdata;

use Badcow\DNS\Validator;

/**
 * @see https://tools.ietf.org/html/rfc1035#section-3.3.12
 */
class PTR extends CNAME
{
	const TYPE = 'PTR';
	const TYPE_CODE = 12;

	/**
	 * Expands an IPv6 address to its full, non-shorthand representation.
	 *
	 * E.g. 2001:db8:9a::42 -> 2001:0db8:009a:0000:0000:0000:0000:0042
	 *
	 * @param string $ip IPv6 address
	 *
	 * @throws \InvalidArgumentException
	 *
	 * @return string
	 */
	public static function expandIpv6(string $ip): string
	{
		if (!Validator::ipv6($ip)) {
		    throw new \InvalidArgumentException(sprintf('"%s" is not a valid IPv6 address.', $ip));
		}

		if (false === $packed = inet_pton($ip)) {
		    throw new \InvalidArgumentException(sprintf('"%s" is not a valid IPv6 address.', $ip));
		}

		$hex = unpack('H*hex', $packed);

		return implode(':', str_split($hex['hex'], 4));
	}


	/**
	 * This function will expand in incomplete IPv6 address.
	 * An incomplete IPv6 address is of the form `2001:db8:ff:abcd`
	 * i.e. one where there is less than eight hextets.
	 *
	 * @param string $ip IPv6 address
	 *
	 * @return string Expanded incomplete IPv6 address
	 */
	public static function expandIncompleteIpv6(string $ip): string
	{
		$hextets = array_map(function ($hextet) {
		    return str_pad($hextet, 4, '0', STR_PAD_LEFT);
		}, explode(':', $ip));

		return implode(':', $hextets);
	}


	/**
	 * Takes a valid IPv6 address and contracts it
	 * to its shorter version.
	 *
	 * E.g.: 2001:0000:0000:acad:0000:0000:0000:0001 -> 2001:0:0:acad::1
	 *
	 * Note: If there is more than one set of consecutive hextets, the function
	 * will favour the larger of the sets. If both sets of zeroes are the same
	 * the first will be favoured in the omission of zeroes.
	 *
	 * E.g.: 2001:0000:0000:ab80:2390:0000:0000:000a -> 2001:0:0:ab80:2390::a
	 *
	 * @param string $ip IPv6 address
	 *
	 * @throws \InvalidArgumentException
	 *
	 * @return string Contracted IPv6 address
	 */
	public static function contractIpv6(string $ip): string
	{
		$packed = inet_pton($ip);

		if (!Validator::ipv6($ip) || false === $packed) {
		    throw new \InvalidArgumentException(sprintf('"%s" is not a valid IPv6 address.', $ip));
		}

		$unpacked = inet_ntop($packed);

		if (false === $unpacked) {
		    throw new \InvalidArgumentException(sprintf('"%s" could not be contracted.', $ip));
		}

		return $unpacked;
	}


	/**
	 * Creates a reverse IPv4 address.
	 *
	 * E.g. 192.168.1.213 -> 213.1.168.192.in-addr.arpa.
	 *
	 * @param string $ip Valid IPv4 address
	 *
	 * @return string Reversed IP address appended with ".in-addr.arpa."
	 */
	public static function reverseIpv4(string $ip): string
	{
		$octets = array_reverse(explode('.', $ip));

		return implode('.', $octets).'.in-addr.arpa.';
	}


	/**
	 * Creates a reverse IPv6 address.
	 *
	 * E.g. 2001:db8::567:89ab -> b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
	 *
	 * @param string $ip           A full or partial IPv6 address
	 * @param bool   $appendSuffix Whether or not to append ".ip6.arpa.' suffix.
	 *
	 * @return string The reversed address appended with ".ip6.arpa."
	 */
	public static function reverseIpv6(string $ip, bool $appendSuffix = true): string
	{
		try {
		    $ip = self::expandIpv6($ip);
		} catch (\InvalidArgumentException $e) {
		    $ip = self::expandIncompleteIpv6($ip);
		}

		$ip = str_replace(':', '', $ip);
		$ip = strrev($ip);
		$ip = implode('.', str_split($ip));
		$ip .= $appendSuffix ? '.ip6.arpa.' : '';

		return $ip;
	}
}
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