<?php
namespace TYPO3\CMS\Core\Mail;

/**
 * RFC 822 Email address list validation Utility
 *
 * PHP versions 4 and 5
 *
 * LICENSE:
 *
 * Copyright (c) 2001-2010, Richard Heyes
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * o Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * o Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * o The names of the authors may not be used to endorse or promote
 * products derived from this software without specific prior written
 * permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @category Mail
 * @package Mail
 * @author Richard Heyes <richard@phpguru.org>
 * @author Chuck Hagenbuch <chuck@horde.org
 * @copyright 2001-2010 Richard Heyes
 * @license http://opensource.org/licenses/bsd-license.php New BSD License
 * @link http://pear.php.net/package/Mail/
 */
/**
 * RFC 822 Email address list validation Utility
 *
 * What is it?
 *
 * This class will take an address string, and parse it into it's consituent
 * parts, be that either addresses, groups, or combinations. Nested groups
 * are not supported. The structure it returns is pretty straight forward,
 * and is similar to that provided by the imap_rfc822_parse_adrlist(). Use
 * print_r() to view the structure.
 *
 * How do I use it?
 *
 * $address_string = 'My Group: "Richard" <richard@localhost> (A comment), ted@example.com (Ted Bloggs), Barney;';
 * $structure = Mail_RFC822::parseAddressList($address_string, 'example.com', TRUE)
 * print_r($structure);
 *
 * @author Richard Heyes <richard@phpguru.org>
 * @author Chuck Hagenbuch <chuck@horde.org>
 * @version $Revision: 294749 $
 * @license BSD
 * @package Mail
 */
class Rfc822AddressesParser {

	/**
	 * The address being parsed by the RFC822 object.
	 *
	 * @var string $address
	 */
	private $address = '';

	/**
	 * The default domain to use for unqualified addresses.
	 *
	 * @var string $default_domain
	 */
	private $default_domain = 'localhost';

	/**
	 * Whether or not to validate atoms for non-ascii characters.
	 *
	 * @var boolean $validate
	 */
	private $validate = TRUE;

	/**
	 * The array of raw addresses built up as we parse.
	 *
	 * @var array $addresses
	 */
	private $addresses = array();

	/**
	 * The final array of parsed address information that we build up.
	 *
	 * @var array $structure
	 */
	private $structure = array();

	/**
	 * The current error message, if any.
	 *
	 * @var string $error
	 */
	private $error = NULL;

	/**
	 * An internal counter/pointer.
	 *
	 * @var integer $index
	 */
	private $index = NULL;

	/**
	 * The number of groups that have been found in the address list.
	 *
	 * @var integer $num_groups
	 * @access public
	 */
	private $num_groups = 0;

	/**
	 * A limit after which processing stops
	 *
	 * @var int $limit
	 */
	private $limit = NULL;

	/**
	 * Sets up the object.
	 *
	 * @access public
	 * @param string  $address		 The address(es) to validate.
	 * @param string  $default_domain  Default domain/host etc. If not supplied, will be set to localhost.
	 * @param boolean $validate		Whether to validate atoms. Turn this off if you need to run addresses through before encoding the personal names, for instance.
	 */
	public function __construct($address = NULL, $default_domain = NULL, $validate = NULL, $limit = NULL) {
		if (isset($address)) {
			$this->address = $address;
		}
		if (isset($default_domain)) {
			$this->default_domain = $default_domain;
		}
		if (isset($validate)) {
			$this->validate = $validate;
		}
		if (isset($limit)) {
			$this->limit = $limit;
		}
	}

	/**
	 * Starts the whole process. The address must either be set here
	 * or when creating the object. One or the other.
	 *
	 * @access public
	 * @param string  $address		 The address(es) to validate.
	 * @param string  $default_domain  Default domain/host etc.
	 * @param boolean $nest_groups	 Whether to return the structure with groups nested for easier viewing.
	 * @param boolean $validate		Whether to validate atoms. Turn this off if you need to run addresses through before encoding the personal names, for instance.
	 * @return array A structured array of addresses.
	 */
	public function parseAddressList($address = NULL, $default_domain = NULL, $validate = NULL, $limit = NULL) {
		if (isset($address)) {
			$this->address = $address;
		}
		if (isset($default_domain)) {
			$this->default_domain = $default_domain;
		}
		if (isset($validate)) {
			$this->validate = $validate;
		}
		if (isset($limit)) {
			$this->limit = $limit;
		}
		$this->structure = array();
		$this->addresses = array();
		$this->error = NULL;
		$this->index = NULL;
		// Unfold any long lines in $this->address.
		$this->address = preg_replace('/\\r?\\n/', '
', $this->address);
		$this->address = preg_replace('/\\r\\n(\\t| )+/', ' ', $this->address);
		while ($this->address = $this->_splitAddresses($this->address)) {

		}
		if ($this->address === FALSE || isset($this->error)) {
			throw new \InvalidArgumentException($this->error, 1294681466);
		}
		// Validate each address individually.  If we encounter an invalid
		// address, stop iterating and return an error immediately.
		foreach ($this->addresses as $address) {
			$valid = $this->_validateAddress($address);
			if ($valid === FALSE || isset($this->error)) {
				throw new \InvalidArgumentException($this->error, 1294681467);
			}
			$this->structure = array_merge($this->structure, $valid);
		}
		return $this->structure;
	}

	/**
	 * Splits an address into separate addresses.
	 *
	 * @access private
	 * @param string $address The addresses to split.
	 * @return boolean Success or failure.
	 */
	protected function _splitAddresses($address) {
		if (!empty($this->limit) && count($this->addresses) == $this->limit) {
			return '';
		}
		if ($this->_isGroup($address) && !isset($this->error)) {
			$split_char = ';';
			$is_group = TRUE;
		} elseif (!isset($this->error)) {
			$split_char = ',';
			$is_group = FALSE;
		} elseif (isset($this->error)) {
			return FALSE;
		}
		// Split the string based on the above ten or so lines.
		$parts = explode($split_char, $address);
		$string = $this->_splitCheck($parts, $split_char);
		// If a group...
		if ($is_group) {
			// If $string does not contain a colon outside of
			// brackets/quotes etc then something's fubar.
			// First check there's a colon at all:
			if (strpos($string, ':') === FALSE) {
				$this->error = 'Invalid address: ' . $string;
				return FALSE;
			}
			// Now check it's outside of brackets/quotes:
			if (!$this->_splitCheck(explode(':', $string), ':')) {
				return FALSE;
			}
			// We must have a group at this point, so increase the counter:
			$this->num_groups++;
		}
		// $string now contains the first full address/group.
		// Add to the addresses array.
		$this->addresses[] = array(
			'address' => trim($string),
			'group' => $is_group
		);
		// Remove the now stored address from the initial line, the +1
		// is to account for the explode character.
		$address = trim(substr($address, strlen($string) + 1));
		// If the next char is a comma and this was a group, then
		// there are more addresses, otherwise, if there are any more
		// chars, then there is another address.
		if ($is_group && $address[0] === ',') {
			$address = trim(substr($address, 1));
			return $address;
		} elseif (strlen($address) > 0) {
			return $address;
		} else {
			return '';
		}
	}

	/**
	 * Checks for a group at the start of the string.
	 *
	 * @access private
	 * @param string $address The address to check.
	 * @return boolean Whether or not there is a group at the start of the string.
	 */
	protected function _isGroup($address) {
		// First comma not in quotes, angles or escaped:
		$parts = explode(',', $address);
		$string = $this->_splitCheck($parts, ',');
		// Now we have the first address, we can reliably check for a
		// group by searching for a colon that's not escaped or in
		// quotes or angle brackets.
		if (count(($parts = explode(':', $string))) > 1) {
			$string2 = $this->_splitCheck($parts, ':');
			return $string2 !== $string;
		} else {
			return FALSE;
		}
	}

	/**
	 * A common function that will check an exploded string.
	 *
	 * @access private
	 * @param array $parts The exloded string.
	 * @param string $char  The char that was exploded on.
	 * @return mixed False if the string contains unclosed quotes/brackets, or the string on success.
	 */
	protected function _splitCheck($parts, $char) {
		$string = $parts[0];
		$partsCounter = count($parts);
		for ($i = 0; $i < $partsCounter; $i++) {
			if ($this->_hasUnclosedQuotes($string) || $this->_hasUnclosedBrackets($string, '<>') || $this->_hasUnclosedBrackets($string, '[]') || $this->_hasUnclosedBrackets($string, '()') || substr($string, -1) == '\\') {
				if (isset($parts[$i + 1])) {
					$string = $string . $char . $parts[($i + 1)];
				} else {
					$this->error = 'Invalid address spec. Unclosed bracket or quotes';
					return FALSE;
				}
			} else {
				$this->index = $i;
				break;
			}
		}
		return $string;
	}

	/**
	 * Checks if a string has unclosed quotes or not.
	 *
	 * @access private
	 * @param string $string  The string to check.
	 * @return boolean  TRUE if there are unclosed quotes inside the string,
	 */
	protected function _hasUnclosedQuotes($string) {
		$string = trim($string);
		$iMax = strlen($string);
		$in_quote = FALSE;
		$i = ($slashes = 0);
		for (; $i < $iMax; ++$i) {
			switch ($string[$i]) {
				case '\\':
					++$slashes;
					break;
				case '"':
					if ($slashes % 2 == 0) {
						$in_quote = !$in_quote;
					}
				default:
					$slashes = 0;
			}
		}
		return $in_quote;
	}

	/**
	 * Checks if a string has an unclosed brackets or not. IMPORTANT:
	 * This function handles both angle brackets and square brackets;
	 *
	 * @access private
	 * @param string $string The string to check.
	 * @param string $chars  The characters to check for.
	 * @return boolean TRUE if there are unclosed brackets inside the string, FALSE otherwise.
	 */
	protected function _hasUnclosedBrackets($string, $chars) {
		$num_angle_start = substr_count($string, $chars[0]);
		$num_angle_end = substr_count($string, $chars[1]);
		$this->_hasUnclosedBracketsSub($string, $num_angle_start, $chars[0]);
		$this->_hasUnclosedBracketsSub($string, $num_angle_end, $chars[1]);
		if ($num_angle_start < $num_angle_end) {
			$this->error = 'Invalid address spec. Unmatched quote or bracket (' . $chars . ')';
			return FALSE;
		} else {
			return $num_angle_start > $num_angle_end;
		}
	}

	/**
	 * Sub function that is used only by hasUnclosedBrackets().
	 *
	 * @access private
	 * @param string $string The string to check.
	 * @param integer &$num	The number of occurrences.
	 * @param string $char   The character to count.
	 * @return integer The number of occurrences of $char in $string, adjusted for backslashes.
	 */
	protected function _hasUnclosedBracketsSub($string, &$num, $char) {
		$parts = explode($char, $string);
		$partsCounter = count($parts);
		for ($i = 0; $i < $partsCounter; $i++) {
			if (substr($parts[$i], -1) == '\\' || $this->_hasUnclosedQuotes($parts[$i])) {
				$num--;
			}
			if (isset($parts[$i + 1])) {
				$parts[$i + 1] = $parts[$i] . $char . $parts[($i + 1)];
			}
		}
		return $num;
	}

	/**
	 * Function to begin checking the address.
	 *
	 * @access private
	 * @param string $address The address to validate.
	 * @return mixed False on failure, or a structured array of address information on success.
	 */
	protected function _validateAddress($address) {
		$is_group = FALSE;
		$addresses = array();
		if ($address['group']) {
			$is_group = TRUE;
			// Get the group part of the name
			$parts = explode(':', $address['address']);
			$groupname = $this->_splitCheck($parts, ':');
			$structure = array();
			// And validate the group part of the name.
			if (!$this->_validatePhrase($groupname)) {
				$this->error = 'Group name did not validate.';
				return FALSE;
			}
			$address['address'] = ltrim(substr($address['address'], strlen($groupname . ':')));
		}
		// If a group then split on comma and put into an array.
		// Otherwise, Just put the whole address in an array.
		if ($is_group) {
			while (strlen($address['address']) > 0) {
				$parts = explode(',', $address['address']);
				$addresses[] = $this->_splitCheck($parts, ',');
				$address['address'] = trim(substr($address['address'], strlen(end($addresses) . ',')));
			}
		} else {
			$addresses[] = $address['address'];
		}
		// Check that $addresses is set, if address like this:
		// Groupname:;
		// Then errors were appearing.
		if (!count($addresses)) {
			$this->error = 'Empty group.';
			return FALSE;
		}
		// Trim the whitespace from all of the address strings.
		array_map('trim', $addresses);
		// Validate each mailbox.
		// Format could be one of: name <geezer@domain.com>
		//                         geezer@domain.com
		//                         geezer
		// ... or any other format valid by RFC 822.
		$addressesCount = count($addresses);
		for ($i = 0; $i < $addressesCount; $i++) {
			if (!$this->validateMailbox($addresses[$i])) {
				if (empty($this->error)) {
					$this->error = 'Validation failed for: ' . $addresses[$i];
				}
				return FALSE;
			}
		}
		if ($is_group) {
			$structure = array_merge($structure, $addresses);
		} else {
			$structure = $addresses;
		}
		return $structure;
	}

	/**
	 * Function to validate a phrase.
	 *
	 * @access private
	 * @param string $phrase The phrase to check.
	 * @return boolean Success or failure.
	 */
	protected function _validatePhrase($phrase) {
		// Splits on one or more Tab or space.
		$parts = preg_split('/[ \\x09]+/', $phrase, -1, PREG_SPLIT_NO_EMPTY);
		$phrase_parts = array();
		while (count($parts) > 0) {
			$phrase_parts[] = $this->_splitCheck($parts, ' ');
			for ($i = 0; $i < $this->index + 1; $i++) {
				array_shift($parts);
			}
		}
		foreach ($phrase_parts as $part) {
			// If quoted string:
			if ($part[0] === '"') {
				if (!$this->_validateQuotedString($part)) {
					return FALSE;
				}
				continue;
			}
			// Otherwise it's an atom:
			if (!$this->_validateAtom($part)) {
				return FALSE;
			}
		}
		return TRUE;
	}

	/**
	 * Function to validate an atom which from rfc822 is:
	 * atom = 1*<any CHAR except specials, SPACE and CTLs>
	 *
	 * If validation ($this->validate) has been turned off, then
	 * validateAtom() doesn't actually check anything. This is so that you
	 * can split a list of addresses up before encoding personal names
	 * (umlauts, etc.), for example.
	 *
	 * @access private
	 * @param string $atom The string to check.
	 * @return boolean Success or failure.
	 */
	protected function _validateAtom($atom) {
		if (!$this->validate) {
			// Validation has been turned off; assume the atom is okay.
			return TRUE;
		}
		// Check for any char from ASCII 0 - ASCII 127
		if (!preg_match('/^[\\x00-\\x7E]+$/i', $atom, $matches)) {
			return FALSE;
		}
		// Check for specials:
		if (preg_match('/[][()<>@,;\\:". ]/', $atom)) {
			return FALSE;
		}
		// Check for control characters (ASCII 0-31):
		if (preg_match('/[\\x00-\\x1F]+/', $atom)) {
			return FALSE;
		}
		return TRUE;
	}

	/**
	 * Function to validate quoted string, which is:
	 * quoted-string = <"> *(qtext/quoted-pair) <">
	 *
	 * @access private
	 * @param string $qstring The string to check
	 * @return boolean Success or failure.
	 */
	protected function _validateQuotedString($qstring) {
		// Leading and trailing "
		$qstring = substr($qstring, 1, -1);
		// Perform check, removing quoted characters first.
		return !preg_match('/[\\x0D\\\\"]/', preg_replace('/\\\\./', '', $qstring));
	}

	/**
	 * Function to validate a mailbox, which is:
	 * mailbox =   addr-spec		 ; simple address
	 * phrase route-addr ; name and route-addr
	 *
	 * @access public
	 * @param string &$mailbox The string to check.
	 * @return boolean Success or failure.
	 */
	protected function validateMailbox(&$mailbox) {
		// A couple of defaults.
		$phrase = '';
		$comment = '';
		$comments = array();
		// Catch any RFC822 comments and store them separately.
		$_mailbox = $mailbox;
		while (strlen(trim($_mailbox)) > 0) {
			$parts = explode('(', $_mailbox);
			$before_comment = $this->_splitCheck($parts, '(');
			if ($before_comment != $_mailbox) {
				// First char should be a (.
				$comment = substr(str_replace($before_comment, '', $_mailbox), 1);
				$parts = explode(')', $comment);
				$comment = $this->_splitCheck($parts, ')');
				$comments[] = $comment;
				// +2 is for the brackets
				$_mailbox = substr($_mailbox, strpos($_mailbox, ('(' . $comment)) + strlen($comment) + 2);
			} else {
				break;
			}
		}
		foreach ($comments as $comment) {
			$mailbox = str_replace('(' . $comment . ')', '', $mailbox);
		}
		$mailbox = trim($mailbox);
		// Check for name + route-addr
		if (substr($mailbox, -1) === '>' && $mailbox[0] !== '<') {
			$parts = explode('<', $mailbox);
			$name = $this->_splitCheck($parts, '<');
			$phrase = trim($name);
			$route_addr = trim(substr($mailbox, strlen($name . '<'), -1));
			if ($this->_validatePhrase($phrase) === FALSE || ($route_addr = $this->_validateRouteAddr($route_addr)) === FALSE) {
				return FALSE;
			}
		} else {
			// First snip angle brackets if present.
			if ($mailbox[0] === '<' && substr($mailbox, -1) === '>') {
				$addr_spec = substr($mailbox, 1, -1);
			} else {
				$addr_spec = $mailbox;
			}
			if (($addr_spec = $this->_validateAddrSpec($addr_spec)) === FALSE) {
				return FALSE;
			}
		}
		// Construct the object that will be returned.
		$mbox = new \stdClass();
		// Add the phrase (even if empty) and comments
		$mbox->personal = $phrase;
		$mbox->comment = isset($comments) ? $comments : array();
		if (isset($route_addr)) {
			$mbox->mailbox = $route_addr['local_part'];
			$mbox->host = $route_addr['domain'];
			$route_addr['adl'] !== '' ? ($mbox->adl = $route_addr['adl']) : '';
		} else {
			$mbox->mailbox = $addr_spec['local_part'];
			$mbox->host = $addr_spec['domain'];
		}
		$mailbox = $mbox;
		return TRUE;
	}

	/**
	 * This function validates a route-addr which is:
	 * route-addr = "<" [route] addr-spec ">"
	 *
	 * Angle brackets have already been removed at the point of
	 * getting to this function.
	 *
	 * @access private
	 * @param string $route_addr The string to check.
	 * @return mixed False on failure, or an array containing validated address/route information on success.
	 */
	protected function _validateRouteAddr($route_addr) {
		// Check for colon.
		if (strpos($route_addr, ':') !== FALSE) {
			$parts = explode(':', $route_addr);
			$route = $this->_splitCheck($parts, ':');
		} else {
			$route = $route_addr;
		}
		// If $route is same as $route_addr then the colon was in
		// quotes or brackets or, of course, non existent.
		if ($route === $route_addr) {
			unset($route);
			$addr_spec = $route_addr;
			if (($addr_spec = $this->_validateAddrSpec($addr_spec)) === FALSE) {
				return FALSE;
			}
		} else {
			// Validate route part.
			if (($route = $this->_validateRoute($route)) === FALSE) {
				return FALSE;
			}
			$addr_spec = substr($route_addr, strlen($route . ':'));
			// Validate addr-spec part.
			if (($addr_spec = $this->_validateAddrSpec($addr_spec)) === FALSE) {
				return FALSE;
			}
		}
		if (isset($route)) {
			$return['adl'] = $route;
		} else {
			$return['adl'] = '';
		}
		$return = array_merge($return, $addr_spec);
		return $return;
	}

	/**
	 * Function to validate a route, which is:
	 * route = 1#("@" domain) ":"
	 *
	 * @access private
	 * @param string $route The string to check.
	 * @return mixed False on failure, or the validated $route on success.
	 */
	protected function _validateRoute($route) {
		// Split on comma.
		$domains = explode(',', trim($route));
		foreach ($domains as $domain) {
			$domain = str_replace('@', '', trim($domain));
			if (!$this->_validateDomain($domain)) {
				return FALSE;
			}
		}
		return $route;
	}

	/**
	 * Function to validate a domain, though this is not quite what
	 * you expect of a strict internet domain.
	 *
	 * domain = sub-domain *("." sub-domain)
	 *
	 * @access private
	 * @param string $domain The string to check.
	 * @return mixed False on failure, or the validated domain on success.
	 */
	protected function _validateDomain($domain) {
		// Note the different use of $subdomains and $sub_domains
		$subdomains = explode('.', $domain);
		while (count($subdomains) > 0) {
			$sub_domains[] = $this->_splitCheck($subdomains, '.');
			for ($i = 0; $i < $this->index + 1; $i++) {
				array_shift($subdomains);
			}
		}
		foreach ($sub_domains as $sub_domain) {
			if (!$this->_validateSubdomain(trim($sub_domain))) {
				return FALSE;
			}
		}
		// Managed to get here, so return input.
		return $domain;
	}

	/**
	 * Function to validate a subdomain:
	 * subdomain = domain-ref / domain-literal
	 *
	 * @access private
	 * @param string $subdomain The string to check.
	 * @return boolean Success or failure.
	 */
	protected function _validateSubdomain($subdomain) {
		if (preg_match('|^\\[(.*)]$|', $subdomain, $arr)) {
			if (!$this->_validateDliteral($arr[1])) {
				return FALSE;
			}
		} else {
			if (!$this->_validateAtom($subdomain)) {
				return FALSE;
			}
		}
		// Got here, so return successful.
		return TRUE;
	}

	/**
	 * Function to validate a domain literal:
	 * domain-literal =  "[" *(dtext / quoted-pair) "]"
	 *
	 * @access private
	 * @param string $dliteral The string to check.
	 * @return boolean Success or failure.
	 */
	protected function _validateDliteral($dliteral) {
		return !preg_match('/(.)[][\\x0D\\\\]/', $dliteral, $matches) && $matches[1] != '\\';
	}

	/**
	 * Function to validate an addr-spec.
	 *
	 * addr-spec = local-part "@" domain
	 *
	 * @access private
	 * @param string $addr_spec The string to check.
	 * @return mixed False on failure, or the validated addr-spec on success.
	 */
	protected function _validateAddrSpec($addr_spec) {
		$addr_spec = trim($addr_spec);
		// Split on @ sign if there is one.
		if (strpos($addr_spec, '@') !== FALSE) {
			$parts = explode('@', $addr_spec);
			$local_part = $this->_splitCheck($parts, '@');
			$domain = substr($addr_spec, strlen($local_part . '@'));
		} else {
			$local_part = $addr_spec;
			$domain = $this->default_domain;
		}
		if (($local_part = $this->_validateLocalPart($local_part)) === FALSE) {
			return FALSE;
		}
		if (($domain = $this->_validateDomain($domain)) === FALSE) {
			return FALSE;
		}
		// Got here so return successful.
		return array('local_part' => $local_part, 'domain' => $domain);
	}

	/**
	 * Function to validate the local part of an address:
	 * local-part = word *("." word)
	 *
	 * @access private
	 * @param string $local_part
	 * @return mixed False on failure, or the validated local part on success.
	 */
	protected function _validateLocalPart($local_part) {
		$parts = explode('.', $local_part);
		$words = array();
		// Split the local_part into words.
		while (count($parts) > 0) {
			$words[] = $this->_splitCheck($parts, '.');
			for ($i = 0; $i < $this->index + 1; $i++) {
				array_shift($parts);
			}
		}
		// Validate each word.
		foreach ($words as $word) {
			// If this word contains an unquoted space, it is invalid. (6.2.4)
			if (strpos($word, ' ') && $word[0] !== '"') {
				return FALSE;
			}
			if ($this->_validatePhrase(trim($word)) === FALSE) {
				return FALSE;
			}
		}
		// Managed to get here, so return the input.
		return $local_part;
	}

}
