<?php
/**
 * Class to validate and to work with IPv6 addresses
 *
 * @package Requests
 * @subpackage Utilities
 */

/**
 * Class to validate and to work with IPv6 addresses
 *
 * This was originally based on the PEAR class of the same name, but has been
 * entirely rewritten.
 *
 * @package Requests
 * @subpackage Utilities
 */
class Requests_IPv6 {
	/**
	 * Uncompresses an IPv6 address
	 *
	 * RFC 4291 allows you to compress consecutive zero pieces in an address to
	 * '::'. This method expects a valid IPv6 address and expands the '::' to
	 * the required number of zero pieces.
	 *
	 * Example:  FF01::101   ->  FF01:0:0:0:0:0:0:101
	 *           ::1         ->  0:0:0:0:0:0:0:1
	 *
	 * @author Alexander Merz <alexander.merz@web.de>
	 * @author elfrink at introweb dot nl
	 * @author Josh Peck <jmp at joshpeck dot org>
	 * @copyright 2003-2005 The PHP Group
	 * @license http://www.opensource.org/licenses/bsd-license.php
	 * @param string $ip An IPv6 address
	 * @return string The uncompressed IPv6 address
	 */
	public static function uncompress( $ip ) {
		if ( substr_count( $ip, '::' ) !== 1 ) {
			return $ip;
		}

		list($ip1, $ip2) = explode( '::', $ip );
		$c1 = ( '' == $ip1 ) ? -1 : substr_count( $ip1, ':' );
		$c2 = ( '' == $ip2 ) ? -1 : substr_count( $ip2, ':' );

		if ( strpos( $ip2, '.' ) !== false ) {
			$c2++;
		}
		// ::
		if ( -1 === $c1 && -1 === $c2 ) {
			$ip = '0:0:0:0:0:0:0:0';
		} // ::xxx
		elseif ( -1 === $c1 ) {
			$fill = str_repeat( '0:', 7 - $c2 );
			$ip = str_replace( '::', $fill, $ip );
		} // xxx::
		elseif ( -1 === $c2 ) {
			$fill = str_repeat( ':0', 7 - $c1 );
			$ip = str_replace( '::', $fill, $ip );
		} // xxx::xxx
		else {
			$fill = ':' . str_repeat( '0:', 6 - $c2 - $c1 );
			$ip = str_replace( '::', $fill, $ip );
		}
		return $ip;
	}

	/**
	 * Compresses an IPv6 address
	 *
	 * RFC 4291 allows you to compress consecutive zero pieces in an address to
	 * '::'. This method expects a valid IPv6 address and compresses consecutive
	 * zero pieces to '::'.
	 *
	 * Example:  FF01:0:0:0:0:0:0:101   ->  FF01::101
	 *           0:0:0:0:0:0:0:1        ->  ::1
	 *
	 * @see uncompress()
	 * @param string $ip An IPv6 address
	 * @return string The compressed IPv6 address
	 */
	public static function compress( $ip ) {
		// Prepare the IP to be compressed
		$ip = self::uncompress( $ip );
		$ip_parts = self::split_v6_v4( $ip );

		// Replace all leading zeros
		$ip_parts[0] = preg_replace( '/(^|:)0+([0-9])/', '\1\2', $ip_parts[0] );

		// Find bunches of zeros
		if ( preg_match_all( '/(?:^|:)(?:0(?::|$))+/', $ip_parts[0], $matches, PREG_OFFSET_CAPTURE ) ) {
			$max = 0;
			$pos = null;
			foreach ( $matches[0] as $match ) {
				if ( strlen( $match[0] ) > $max ) {
					$max = strlen( $match[0] );
					$pos = $match[1];
				}
			}

			$ip_parts[0] = substr_replace( $ip_parts[0], '::', $pos, $max );
		}

		if ( '' !== $ip_parts[1] ) {
			return implode( ':', $ip_parts );
		} else {
			return $ip_parts[0];
		}
	}

	/**
	 * Splits an IPv6 address into the IPv6 and IPv4 representation parts
	 *
	 * RFC 4291 allows you to represent the last two parts of an IPv6 address
	 * using the standard IPv4 representation
	 *
	 * Example:  0:0:0:0:0:0:13.1.68.3
	 *           0:0:0:0:0:FFFF:129.144.52.38
	 *
	 * @param string $ip An IPv6 address
	 * @return string[] [0] contains the IPv6 represented part, and [1] the IPv4 represented part
	 */
	protected static function split_v6_v4( $ip ) {
		if ( strpos( $ip, '.' ) !== false ) {
			$pos = strrpos( $ip, ':' );
			$ipv6_part = substr( $ip, 0, $pos );
			$ipv4_part = substr( $ip, $pos + 1 );
			return array( $ipv6_part, $ipv4_part );
		} else {
			return array( $ip, '' );
		}
	}

	/**
	 * Checks an IPv6 address
	 *
	 * Checks if the given IP is a valid IPv6 address
	 *
	 * @param string $ip An IPv6 address
	 * @return bool true if $ip is a valid IPv6 address
	 */
	public static function check_ipv6( $ip ) {
		$ip = self::uncompress( $ip );
		list($ipv6, $ipv4) = self::split_v6_v4( $ip );
		$ipv6 = explode( ':', $ipv6 );
		$ipv4 = explode( '.', $ipv4 );
		if ( count( $ipv6 ) === 8 && count( $ipv4 ) === 1 || count( $ipv6 ) === 6 && count( $ipv4 ) === 4 ) {
			foreach ( $ipv6 as $ipv6_part ) {
				// The section can't be empty
				if ( '' === $ipv6_part ) {
					return false;
				}

				// Nor can it be over four characters
				if ( strlen( $ipv6_part ) > 4 ) {
					return false;
				}

				// Remove leading zeros (this is safe because of the above)
				$ipv6_part = ltrim( $ipv6_part, '0' );
				if ( '' === $ipv6_part ) {
					$ipv6_part = '0';
				}

				// Check the value is valid
				$value = hexdec( $ipv6_part );
				if ( dechex( $value ) !== strtolower( $ipv6_part ) || $value < 0 || $value > 0xFFFF ) {
					return false;
				}
			}
			if ( count( $ipv4 ) === 4 ) {
				foreach ( $ipv4 as $ipv4_part ) {
					$value = (int) $ipv4_part;
					if ( (string) $value !== $ipv4_part || $value < 0 || $value > 0xFF ) {
						return false;
					}
				}
			}
			return true;
		} else {
			return false;
		}
	}
}
