rcube_imap_generic.php
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rcube_imap_generic.php
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	<?php

	/**
	+-----------------------------------------------------------------------+
	\| This file is part of the Roundcube Webmail client \|
	\| \|
	\| Copyright (C) The Roundcube Dev Team \|
	\| Copyright (C) Kolab Systems AG \|
	\| \|
	\| Licensed under the GNU General Public License version 3 or \|
	\| any later version with exceptions for skins & plugins. \|
	\| See the README file for a full license statement. \|
	\| \|
	\| PURPOSE: \|
	\| Provide alternative IMAP library that doesn't rely on the standard \|
	\| C-Client based version. This allows to function regardless \|
	\| of whether or not the PHP build it's running on has IMAP \|
	\| functionality built-in. \|
	\| \|
	\| Based on Iloha IMAP Library. See http://ilohamail.org/ for details \|
	+-----------------------------------------------------------------------+
	\| Author: Aleksander Machniak <alec@alec.pl> \|
	\| Author: Ryo Chijiiwa <Ryo@IlohaMail.org> \|
	+-----------------------------------------------------------------------+
	*/

	/**
	* PHP based wrapper class to connect to an IMAP server
	*
	* @package Framework
	* @subpackage Storage
	*/
	class rcube_imap_generic
	{
	public $error;
	public $errornum;
	public $result;
	public $resultcode;
	public $selected;
	public $data = [];
	public $flags = [
	'SEEN' => '\\Seen',
	'DELETED' => '\\Deleted',
	'ANSWERED' => '\\Answered',
	'DRAFT' => '\\Draft',
	'FLAGGED' => '\\Flagged',
	'FORWARDED' => '$Forwarded',
	'MDNSENT' => '$MDNSent',
	'' => '\\',
	];

	protected $fp;
	protected $host;
	protected $user;
	protected $cmd_tag;
	protected $cmd_num = 0;
	protected $resourceid;
	protected $extensions_enabled;
	protected $prefs = [];
	protected $logged = false;
	protected $capability = [];
	protected $capability_read = false;
	protected $debug = false;
	protected $debug_handler = false;

	const ERROR_OK = 0;
	const ERROR_NO = -1;
	const ERROR_BAD = -2;
	const ERROR_BYE = -3;
	const ERROR_UNKNOWN = -4;
	const ERROR_COMMAND = -5;
	const ERROR_READONLY = -6;

	const COMMAND_NORESPONSE = 1;
	const COMMAND_CAPABILITY = 2;
	const COMMAND_LASTLINE = 4;
	const COMMAND_ANONYMIZED = 8;

	const DEBUG_LINE_LENGTH = 4098; // 4KB + 2B for \r\n


	/**
	* Send simple (one line) command to the connection stream
	*
	* @param string $string Command string
	* @param bool $endln True if CRLF need to be added at the end of command
	* @param bool $anonymized Don't write the given data to log but a placeholder
	*
	* @param int Number of bytes sent, False on error
	*/
	protected function putLine($string, $endln = true, $anonymized = false)
	{
	if (!$this->fp) {
	return false;
	}

	if ($this->debug) {
	// anonymize the sent command for logging
	$cut = $endln ? 2 : 0;
	if ($anonymized && preg_match('/^(A\d+ (?:[A-Z]+ )+)(.+)/', $string, $m)) {
	$log = $m[1] . sprintf('****** [%d]', strlen($m[2]) - $cut);
	}
	else if ($anonymized) {
	$log = sprintf('****** [%d]', strlen($string) - $cut);
	}
	else {
	$log = rtrim($string);
	}

	$this->debug('C: ' . $log);
	}

	if ($endln) {
	$string .= "\r\n";
	}

	$res = fwrite($this->fp, $string);

	if ($res === false) {
	$this->closeSocket();
	}

	return $res;
	}

	/**
	* Send command to the connection stream with Command Continuation
	* Requests (RFC3501 7.5) and LITERAL+ (RFC2088) and LITERAL- (RFC7888) support.
	*
	* @param string $string Command string
	* @param bool $endln True if CRLF need to be added at the end of command
	* @param bool $anonymized Don't write the given data to log but a placeholder
	*
	* @return int\|bool Number of bytes sent, False on error
	*/
	protected function putLineC($string, $endln = true, $anonymized = false)
	{
	if (!$this->fp) {
	return false;
	}

	if ($endln) {
	$string .= "\r\n";
	}

	$res = 0;
	if ($parts = preg_split('/(\{[0-9]+\}\r\n)/m', $string, -1, PREG_SPLIT_DELIM_CAPTURE)) {
	for ($i = 0, $cnt = count($parts); $i < $cnt; $i++) {
	if ($i + 1 < $cnt && preg_match('/^\{([0-9]+)\}\r\n$/', $parts[$i+1], $matches)) {
	// LITERAL+/LITERAL- support
	$literal_plus = false;
	if (
	!empty($this->prefs['literal+'])
	\|\| (!empty($this->prefs['literal-']) && $matches[1] <= 4096)
	) {
	$parts[$i+1] = sprintf("{%d+}\r\n", $matches[1]);
	$literal_plus = true;
	}

	$bytes = $this->putLine($parts[$i].$parts[$i+1], false, $anonymized);
	if ($bytes === false) {
	return false;
	}

	$res += $bytes;

	// don't wait if server supports LITERAL+ capability
	if (!$literal_plus) {
	$line = $this->readLine(1000);
	// handle error in command
	if (!isset($line[0]) \|\| $line[0] != '+') {
	return false;
	}
	}

	$i++;
	}
	else {
	$bytes = $this->putLine($parts[$i], false, $anonymized);
	if ($bytes === false) {
	return false;
	}

	$res += $bytes;
	}
	}
	}

	return $res;
	}

	/**
	* Reads line from the connection stream
	*
	* @param int $size Buffer size
	*
	* @return string Line of text response
	*/
	protected function readLine($size = 1024)
	{
	$line = '';

	if (!$size) {
	$size = 1024;
	}

	do {
	if ($this->eof()) {
	return $line;
	}

	$buffer = fgets($this->fp, $size);

	if ($buffer === false) {
	$this->closeSocket();
	break;
	}

	if ($this->debug) {
	$this->debug('S: '. rtrim($buffer));
	}

	$line .= $buffer;
	}
	while (substr($buffer, -1) != "\n");

	return $line;
	}

	/**
	* Reads a line of data from the connection stream including all
	* string continuation literals.
	*
	* @param int $size Buffer size
	*
	* @return string Line of text response
	*/
	protected function readFullLine($size = 1024)
	{
	$line = $this->readLine($size);

	// include all string literals untile the real end of "line"
	while (preg_match('/\{([0-9]+)\}\r\n$/', $line, $m)) {
	$bytes = $m[1];
	$out = '';

	while (strlen($out) < $bytes) {
	$out = $this->readBytes($bytes);
	if ($out === '') {
	break;
	}

	$line .= $out;
	}

	$line .= $this->readLine($size);
	}

	return $line;
	}

	/**
	* Reads more data from the connection stream when provided
	* data contain string literal
	*
	* @param string $line Response text
	* @param bool $escape Enables escaping
	*
	* @return string Line of text response
	*/
	protected function multLine($line, $escape = false)
	{
	$line = rtrim($line);
	if (preg_match('/\{([0-9]+)\}$/', $line, $m)) {
	$out = '';
	$str = substr($line, 0, -strlen($m[0]));
	$bytes = $m[1];

	while (strlen($out) < $bytes) {
	$line = $this->readBytes($bytes);
	if ($line === '') {
	break;
	}

	$out .= $line;
	}

	$line = $str . ($escape ? $this->escape($out) : $out);
	}

	return $line;
	}

	/**
	* Reads specified number of bytes from the connection stream
	*
	* @param int $bytes Number of bytes to get
	*
	* @return string Response text
	*/
	protected function readBytes($bytes)
	{
	$data = '';
	$len = 0;

	while ($len < $bytes && !$this->eof()) {
	$d = fread($this->fp, $bytes-$len);
	if ($this->debug) {
	$this->debug('S: '. $d);
	}
	$data .= $d;
	$data_len = strlen($data);
	if ($len == $data_len) {
	break; // nothing was read -> exit to avoid apache lockups
	}
	$len = $data_len;
	}

	return $data;
	}

	/**
	* Reads complete response to the IMAP command
	*
	* @param array $untagged Will be filled with untagged response lines
	*
	* @return string Response text
	*/
	protected function readReply(&$untagged = null)
	{
	while (true) {
	$line = trim($this->readLine(1024));
	// store untagged response lines
	if (isset($line[0]) && $line[0] == '*') {
	$untagged[] = $line;
	}
	else {
	break;
	}
	}

	if ($untagged) {
	$untagged = implode("\n", $untagged);
	}

	return $line;
	}

	/**
	* Response parser.
	*
	* @param string $string Response text
	* @param string $err_prefix Error message prefix
	*
	* @return int Response status
	*/
	protected function parseResult($string, $err_prefix = '')
	{
	if (preg_match('/^[a-z0-9]+ (OK\|NO\|BAD\|BYE)(.)$/i', trim($string), $matches)) {
	$res = strtoupper($matches[1]);
	$str = trim($matches[2]);

	if ($res == 'OK') {
	$this->errornum = self::ERROR_OK;
	}
	else if ($res == 'NO') {
	$this->errornum = self::ERROR_NO;
	}
	else if ($res == 'BAD') {
	$this->errornum = self::ERROR_BAD;
	}
	else if ($res == 'BYE') {
	$this->closeSocket();
	$this->errornum = self::ERROR_BYE;
	}

	if ($str) {
	$str = trim($str);
	// get response string and code (RFC5530)
	if (preg_match("/^\[([a-z-]+)\]/i", $str, $m)) {
	$this->resultcode = strtoupper($m[1]);
	$str = trim(substr($str, strlen($m[1]) + 2));
	}
	else {
	$this->resultcode = null;
	// parse response for [APPENDUID 1204196876 3456]
	if (preg_match("/^\[APPENDUID [0-9]+ ([0-9]+)\]/i", $str, $m)) {
	$this->data['APPENDUID'] = $m[1];
	}
	// parse response for [COPYUID 1204196876 3456:3457 123:124]
	else if (preg_match("/^\[COPYUID [0-9]+ ([0-9,:]+) ([0-9,:]+)\]/i", $str, $m)) {
	$this->data['COPYUID'] = [$m[1], $m[2]];
	}
	}

	$this->result = $str;

	if ($this->errornum != self::ERROR_OK) {
	$this->error = $err_prefix ? $err_prefix.$str : $str;
	}
	}

	return $this->errornum;
	}

	return self::ERROR_UNKNOWN;
	}

	/**
	* Checks connection stream state.
	*
	* @return bool True if connection is closed
	*/
	protected function eof()
	{
	if (!$this->fp) {
	return true;
	}

	// If a connection opened by fsockopen() wasn't closed
	// by the server, feof() will hang.
	$start = microtime(true);

	if (feof($this->fp) \|\|
	($this->prefs['timeout'] && (microtime(true) - $start > $this->prefs['timeout']))
	) {
	$this->closeSocket();
	return true;
	}

	return false;
	}

	/**
	* Closes connection stream.
	*/
	protected function closeSocket()
	{
	if ($this->fp) {
	fclose($this->fp);
	$this->fp = null;
	}
	}

	/**
	* Error code/message setter.
	*/
	protected function setError($code, $msg = '')
	{
	$this->errornum = $code;
	$this->error = $msg;

	return $code;
	}

	/**
	* Checks response status.
	* Checks if command response line starts with specified prefix (or * BYE/BAD)
	*
	* @param string $string Response text
	* @param string $match Prefix to match with (case-sensitive)
	* @param bool $error Enables BYE/BAD checking
	* @param bool $nonempty Enables empty response checking
	*
	* @return bool True any check is true or connection is closed.
	*/
	protected function startsWith($string, $match, $error = false, $nonempty = false)
	{
	if (!$this->fp) {
	return true;
	}

	if (strncmp($string, $match, strlen($match)) == 0) {
	return true;
	}

	if ($error && preg_match('/^\* (BYE\|BAD) /i', $string, $m)) {
	if (strtoupper($m[1]) == 'BYE') {
	$this->closeSocket();
	}
	return true;
	}

	if ($nonempty && !strlen($string)) {
	return true;
	}

	return false;
	}

	/**
	* Capabilities checker
	*/
	protected function hasCapability($name)
	{
	if (empty($this->capability) \|\| empty($name)) {
	return false;
	}

	if (in_array($name, $this->capability)) {
	return true;
	}
	else if (strpos($name, '=')) {
	return false;
	}

	$result = [];
	foreach ($this->capability as $cap) {
	$entry = explode('=', $cap);
	if ($entry[0] == $name) {
	$result[] = $entry[1];
	}
	}

	return $result ?: false;
	}

	/**
	* Capabilities checker
	*
	* @param string $name Capability name
	*
	* @return mixed Capability values array for key=value pairs, true/false for others
	*/
	public function getCapability($name)
	{
	$result = $this->hasCapability($name);

	if (!empty($result)) {
	return $result;
	}
	else if ($this->capability_read) {
	return false;
	}

	// get capabilities (only once) because initial
	// optional CAPABILITY response may differ
	$result = $this->execute('CAPABILITY');

	if ($result[0] == self::ERROR_OK) {
	$this->parseCapability($result[1]);
	}

	$this->capability_read = true;

	return $this->hasCapability($name);
	}

	/**
	* Clears detected server capabilities
	*/
	public function clearCapability()
	{
	$this->capability = [];
	$this->capability_read = false;
	}

	/**
	* DIGEST-MD5/CRAM-MD5/PLAIN Authentication
	*
	* @param string $user Username
	* @param string $pass Password
	* @param string $type Authentication type (PLAIN/CRAM-MD5/DIGEST-MD5)
	*
	* @return resource\|int Connection resource on success, error code on error
	*/
	protected function authenticate($user, $pass, $type = 'PLAIN')
	{
	if ($type == 'CRAM-MD5' \|\| $type == 'DIGEST-MD5') {
	if ($type == 'DIGEST-MD5' && !class_exists('Auth_SASL')) {
	return $this->setError(self::ERROR_BYE,
	"The Auth_SASL package is required for DIGEST-MD5 authentication");
	}

	$this->putLine($this->nextTag() . " AUTHENTICATE $type");
	$line = trim($this->readReply());

	if ($line[0] == '+') {
	$challenge = substr($line, 2);
	}
	else {
	return $this->parseResult($line);
	}

	if ($type == 'CRAM-MD5') {
	// RFC2195: CRAM-MD5
	$ipad = '';
	$opad = '';
	$xor = function($str1, $str2) {
	$result = '';
	$size = strlen($str1);
	for ($i=0; $i<$size; $i++) {
	$result .= chr(ord($str1[$i]) ^ ord($str2[$i]));
	}
	return $result;
	};

	// initialize ipad, opad
	for ($i=0; $i<64; $i++) {
	$ipad .= chr(0x36);
	$opad .= chr(0x5C);
	}

	// pad $pass so it's 64 bytes
	$pass = str_pad($pass, 64, chr(0));

	// generate hash
	$hash = md5($xor($pass, $opad) . pack("H*",
	md5($xor($pass, $ipad) . base64_decode($challenge))));
	$reply = base64_encode($user . ' ' . $hash);

	// send result
	$this->putLine($reply, true, true);
	}
	else {
	// RFC2831: DIGEST-MD5
	// proxy authorization
	if (!empty($this->prefs['auth_cid'])) {
	$authc = $this->prefs['auth_cid'];
	$pass = $this->prefs['auth_pw'];
	}
	else {
	$authc = $user;
	$user = '';
	}

	$auth_sasl = new Auth_SASL;
	$auth_sasl = $auth_sasl->factory('digestmd5');
	$reply = base64_encode($auth_sasl->getResponse($authc, $pass,
	base64_decode($challenge), $this->host, 'imap', $user));

	// send result
	$this->putLine($reply, true, true);
	$line = trim($this->readReply());

	if ($line[0] != '+') {
	return $this->parseResult($line);
	}

	// check response
	$challenge = substr($line, 2);
	$challenge = base64_decode($challenge);
	if (strpos($challenge, 'rspauth=') === false) {
	return $this->setError(self::ERROR_BAD,
	"Unexpected response from server to DIGEST-MD5 response");
	}

	$this->putLine('');
	}

	$line = $this->readReply();
	$result = $this->parseResult($line);
	}
	else if ($type == 'GSSAPI') {
	if (!extension_loaded('krb5')) {
	return $this->setError(self::ERROR_BYE,
	"The krb5 extension is required for GSSAPI authentication");
	}

	if (empty($this->prefs['gssapi_cn'])) {
	return $this->setError(self::ERROR_BYE,
	"The gssapi_cn parameter is required for GSSAPI authentication");
	}

	if (empty($this->prefs['gssapi_context'])) {
	return $this->setError(self::ERROR_BYE,
	"The gssapi_context parameter is required for GSSAPI authentication");
	}

	putenv('KRB5CCNAME=' . $this->prefs['gssapi_cn']);

	try {
	$ccache = new KRB5CCache();
	$ccache->open($this->prefs['gssapi_cn']);
	$gssapicontext = new GSSAPIContext();
	$gssapicontext->acquireCredentials($ccache);

	$token = '';
	$success = $gssapicontext->initSecContext($this->prefs['gssapi_context'], null, null, null, $token);
	$token = base64_encode($token);
	}
	catch (Exception $e) {
	trigger_error($e->getMessage(), E_USER_WARNING);
	return $this->setError(self::ERROR_BYE, "GSSAPI authentication failed");
	}

	$this->putLine($this->nextTag() . " AUTHENTICATE GSSAPI " . $token);
	$line = trim($this->readReply());

	if ($line[0] != '+') {
	return $this->parseResult($line);
	}

	try {
	$itoken = base64_decode(substr($line, 2));

	if (!$gssapicontext->unwrap($itoken, $itoken)) {
	throw new Exception("GSSAPI SASL input token unwrap failed");
	}

	if (strlen($itoken) < 4) {
	throw new Exception("GSSAPI SASL input token invalid");
	}

	// Integrity/encryption layers are not supported. The first bit
	// indicates that the server supports "no security layers".
	// 0x00 should not occur, but support broken implementations.
	$server_layers = ord($itoken[0]);
	if ($server_layers && ($server_layers & 0x1) != 0x1) {
	throw new Exception("Server requires GSSAPI SASL integrity/encryption");
	}

	// Construct output token. 0x01 in the first octet = SASL layer "none",
	// zero in the following three octets = no data follows.
	// See https://github.com/cyrusimap/cyrus-sasl/blob/e41cfb986c1b1935770de554872247453fdbb079/plugins/gssapi.c#L1284
	if (!$gssapicontext->wrap(pack("CCCC", 0x1, 0, 0, 0), $otoken, true)) {
	throw new Exception("GSSAPI SASL output token wrap failed");
	}
	}
	catch (Exception $e) {
	trigger_error($e->getMessage(), E_USER_WARNING);
	return $this->setError(self::ERROR_BYE, "GSSAPI authentication failed");
	}

	$this->putLine(base64_encode($otoken));

	$line = $this->readReply();
	$result = $this->parseResult($line);
	}
	else if ($type == 'PLAIN') {
	// proxy authorization
	if (!empty($this->prefs['auth_cid'])) {
	$authc = $this->prefs['auth_cid'];
	$pass = $this->prefs['auth_pw'];
	}
	else {
	$authc = $user;
	$user = '';
	}

	$reply = base64_encode($user . chr(0) . $authc . chr(0) . $pass);

	// RFC 4959 (SASL-IR): save one round trip
	if ($this->getCapability('SASL-IR')) {
	list($result, $line) = $this->execute("AUTHENTICATE PLAIN", [$reply],
	self::COMMAND_LASTLINE \| self::COMMAND_CAPABILITY \| self::COMMAND_ANONYMIZED);
	}
	else {
	$this->putLine($this->nextTag() . " AUTHENTICATE PLAIN");
	$line = trim($this->readReply());

	if ($line[0] != '+') {
	return $this->parseResult($line);
	}

	// send result, get reply and process it
	$this->putLine($reply, true, true);
	$line = $this->readReply();
	$result = $this->parseResult($line);
	}
	}
	else if ($type == 'LOGIN') {
	$this->putLine($this->nextTag() . " AUTHENTICATE LOGIN");

	$line = trim($this->readReply());
	if ($line[0] != '+') {
	return $this->parseResult($line);
	}

	$this->putLine(base64_encode($user), true, true);

	$line = trim($this->readReply());
	if ($line[0] != '+') {
	return $this->parseResult($line);
	}

	// send result, get reply and process it
	$this->putLine(base64_encode($pass), true, true);

	$line = $this->readReply();
	$result = $this->parseResult($line);
	}
	else if ($type == 'XOAUTH2') {
	$auth = base64_encode("user=$user\1auth=$pass\1\1");
	$this->putLine($this->nextTag() . " AUTHENTICATE XOAUTH2 $auth", true, true);

	$line = trim($this->readReply());

	if ($line[0] == '+') {
	// send empty line
	$this->putLine('', true, true);
	$line = $this->readReply();
	}

	$result = $this->parseResult($line);
	}
	else {
	$line = 'not supported';
	$result = self::ERROR_UNKNOWN;
	}

	if ($result === self::ERROR_OK) {
	// optional CAPABILITY response
	if ($line && preg_match('/\[CAPABILITY ([^]]+)\]/i', $line, $matches)) {
	$this->parseCapability($matches[1], true);
	}

	return $this->fp;
	}

	return $this->setError($result, "AUTHENTICATE $type: $line");
	}

	/**
	* LOGIN Authentication
	*
	* @param string $user Username
	* @param string $pass Password
	*
	* @return resource\|int Connection resource on success, error code on error
	*/
	protected function login($user, $password)
	{
	// Prevent from sending credentials in plain text when connection is not secure
	if ($this->getCapability('LOGINDISABLED')) {
	return $this->setError(self::ERROR_BAD, "Login disabled by IMAP server");
	}

	list($code, $response) = $this->execute('LOGIN', [$this->escape($user, true), $this->escape($password, true)],
	self::COMMAND_CAPABILITY \| self::COMMAND_ANONYMIZED);

	// re-set capabilities list if untagged CAPABILITY response provided
	if (preg_match('/\* CAPABILITY (.+)/i', $response, $matches)) {
	$this->parseCapability($matches[1], true);
	}

	if ($code == self::ERROR_OK) {
	return $this->fp;
	}

	return $code;
	}

	/**
	* Detects hierarchy delimiter
	*
	* @return string The delimiter
	*/
	public function getHierarchyDelimiter()
	{
	if (!empty($this->prefs['delimiter'])) {
	return $this->prefs['delimiter'];
	}

	// try (LIST "" ""), should return delimiter (RFC2060 Sec 6.3.8)
	list($code, $response) = $this->execute('LIST', [$this->escape(''), $this->escape('')]);

	if ($code == self::ERROR_OK) {
	$args = $this->tokenizeResponse($response, 4);
	$delimiter = $args[3];

	if (strlen($delimiter) > 0) {
	return ($this->prefs['delimiter'] = $delimiter);
	}
	}
	}

	/**
	* NAMESPACE handler (RFC 2342)
	*
	* @return array Namespace data hash (personal, other, shared)
	*/
	public function getNamespace()
	{
	if (array_key_exists('namespace', $this->prefs)) {
	return $this->prefs['namespace'];
	}

	if (!$this->getCapability('NAMESPACE')) {
	return self::ERROR_BAD;
	}

	list($code, $response) = $this->execute('NAMESPACE');

	if ($code == self::ERROR_OK && preg_match('/^\* NAMESPACE /', $response)) {
	$response = substr($response, 11);
	$data = $this->tokenizeResponse($response);
	}

	if (!isset($data) \|\| !is_array($data)) {
	return $code;
	}

	$this->prefs['namespace'] = [
	'personal' => $data[0],
	'other' => $data[1],
	'shared' => $data[2],
	];

	return $this->prefs['namespace'];
	}

	/**
	* Connects to IMAP server and authenticates.
	*
	* @param string $host Server hostname or IP
	* @param string $user User name
	* @param string $password Password
	* @param array $options Connection and class options
	*
	* @return bool True on success, False on failure
	*/
	public function connect($host, $user, $password, $options = [])
	{
	// configure
	$this->set_prefs($options);

	$this->host = $host;
	$this->user = $user;
	$this->logged = false;
	$this->selected = null;

	// check input
	if (empty($host)) {
	$this->setError(self::ERROR_BAD, "Empty host");
	return false;
	}

	if (empty($user)) {
	$this->setError(self::ERROR_NO, "Empty user");
	return false;
	}

	if (empty($password) && empty($options['gssapi_cn'])) {
	$this->setError(self::ERROR_NO, "Empty password");
	return false;
	}

	// Connect
	if (!$this->_connect($host)) {
	return false;
	}

	// Send pre authentication ID info (#7860)
	if (!empty($this->prefs['preauth_ident']) && $this->getCapability('ID')) {
	$this->data['ID'] = $this->id($this->prefs['preauth_ident']);
	}

	$auth_method = $this->prefs['auth_type'];
	$auth_methods = [];
	$result = null;

	// check for supported auth methods
	if (!$auth_method \|\| $auth_method == 'CHECK') {
	if ($auth_caps = $this->getCapability('AUTH')) {
	$auth_methods = $auth_caps;
	}

	// Use best (for security) supported authentication method
	$all_methods = ['DIGEST-MD5', 'CRAM-MD5', 'CRAM_MD5', 'PLAIN', 'LOGIN'];

	if (!empty($this->prefs['gssapi_cn'])) {
	array_unshift($all_methods, 'GSSAPI');
	}

	foreach ($all_methods as $auth_method) {
	if (in_array($auth_method, $auth_methods)) {
	break;
	}
	}

	// Prefer LOGIN over AUTHENTICATE LOGIN for performance reasons
	if ($auth_method == 'LOGIN' && !$this->getCapability('LOGINDISABLED')) {
	$auth_method = 'IMAP';
	}
	}

	// pre-login capabilities can be not complete
	$this->capability_read = false;

	// Authenticate
	switch ($auth_method) {
	case 'CRAM_MD5':
	$auth_method = 'CRAM-MD5';
	case 'CRAM-MD5':
	case 'DIGEST-MD5':
	case 'GSSAPI':
	case 'PLAIN':
	case 'LOGIN':
	case 'XOAUTH2':
	$result = $this->authenticate($user, $password, $auth_method);
	break;

	case 'IMAP':
	$result = $this->login($user, $password);
	break;

	default:
	$this->setError(self::ERROR_BAD, "Configuration error. Unknown auth method: $auth_method");
	}

	// Connected and authenticated
	if (is_resource($result)) {
	if (!empty($this->prefs['force_caps'])) {
	$this->clearCapability();
	}

	$this->logged = true;

	// Send ID info after authentication to ensure reliable result (#7517)
	if (!empty($this->prefs['ident']) && $this->getCapability('ID')) {
	$this->data['ID'] = $this->id($this->prefs['ident']);
	}

	return true;
	}

	$this->closeConnection();

	return false;
	}

	/**
	* Connects to IMAP server.
	*
	* @param string $host Server hostname or IP
	*
	* @return bool True on success, False on failure
	*/
	protected function _connect($host)
	{
	// initialize connection
	$this->error = '';
	$this->errornum = self::ERROR_OK;

	$port = empty($this->prefs['port']) ? 143 : $this->prefs['port'];
	$ssl_mode = $this->prefs['ssl_mode'] ?? null;

	// check for SSL
	if (!empty($ssl_mode) && $ssl_mode != 'tls') {
	$host = $ssl_mode . '://' . $host;
	}

	if (empty($this->prefs['timeout']) \|\| $this->prefs['timeout'] < 0) {
	$this->prefs['timeout'] = max(0, intval(ini_get('default_socket_timeout')));
	}

	if ($this->debug) {
	// set connection identifier for debug output
	$this->resourceid = strtoupper(substr(md5(microtime() . $host . $this->user), 0, 4));

	$_host = ($ssl_mode == 'tls' ? 'tls://' : '') . $host . ':' . $port;
	$this->debug("Connecting to $_host...");
	}

	if (!empty($this->prefs['socket_options'])) {
	$options = array_intersect_key($this->prefs['socket_options'], ['ssl' => 1]);
	$context = stream_context_create($options);
	$this->fp = stream_socket_client($host . ':' . $port, $errno, $errstr,
	$this->prefs['timeout'], STREAM_CLIENT_CONNECT, $context);
	}
	else {
	$this->fp = @fsockopen($host, $port, $errno, $errstr, $this->prefs['timeout']);
	}

	if (!$this->fp) {
	$this->setError(self::ERROR_BAD, sprintf("Could not connect to %s:%d: %s",
	$host, $port, $errstr ?: "Unknown reason"));

	return false;
	}

	if ($this->prefs['timeout'] > 0) {
	stream_set_timeout($this->fp, $this->prefs['timeout']);
	}

	$line = trim(fgets($this->fp, 8192));

	if ($this->debug && $line) {
	$this->debug('S: '. $line);
	}

	// Connected to wrong port or connection error?
	if (!preg_match('/^\* (OK\|PREAUTH)/i', $line)) {
	if ($line) {
	$error = sprintf("Wrong startup greeting (%s:%d): %s", $host, $port, $line);
	}
	else {
	$error = sprintf("Empty startup greeting (%s:%d)", $host, $port);
	}

	$this->setError(self::ERROR_BAD, $error);
	$this->closeConnection();
	return false;
	}

	$this->data['GREETING'] = trim(preg_replace('/\[[^\]]+\]\s*/', '', $line));

	// RFC3501 [7.1] optional CAPABILITY response
	if (preg_match('/\[CAPABILITY ([^]]+)\]/i', $line, $matches)) {
	$this->parseCapability($matches[1], true);
	}

	// TLS connection
	if ($ssl_mode == 'tls' && $this->getCapability('STARTTLS')) {
	$res = $this->execute('STARTTLS');

	if (empty($res) \|\| $res[0] != self::ERROR_OK) {
	$this->closeConnection();
	return false;
	}

	if (isset($this->prefs['socket_options']['ssl']['crypto_method'])) {
	$crypto_method = $this->prefs['socket_options']['ssl']['crypto_method'];
	}
	else {
	// There is no flag to enable all TLS methods. Net_SMTP
	// handles enabling TLS similarly.
	$crypto_method = STREAM_CRYPTO_METHOD_TLS_CLIENT
	\| @STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT
	\| @STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT;
	}

	if (!stream_socket_enable_crypto($this->fp, true, $crypto_method)) {
	$this->setError(self::ERROR_BAD, "Unable to negotiate TLS");
	$this->closeConnection();
	return false;
	}

	// Now we're secure, capabilities need to be reread
	$this->clearCapability();
	}

	return true;
	}

	/**
	* Initializes environment
	*/
	protected function set_prefs($prefs)
	{
	// set preferences
	if (is_array($prefs)) {
	$this->prefs = $prefs;
	}

	// set auth method
	if (!empty($this->prefs['auth_type'])) {
	$this->prefs['auth_type'] = strtoupper($this->prefs['auth_type']);
	}
	else {
	$this->prefs['auth_type'] = 'CHECK';
	}

	// disabled capabilities
	if (!empty($this->prefs['disabled_caps'])) {
	$this->prefs['disabled_caps'] = array_map('strtoupper', (array)$this->prefs['disabled_caps']);
	}

	// additional message flags
	if (!empty($this->prefs['message_flags'])) {
	$this->flags = array_merge($this->flags, $this->prefs['message_flags']);
	unset($this->prefs['message_flags']);
	}
	}

	/**
	* Checks connection status
	*
	* @return bool True if connection is active and user is logged in, False otherwise.
	*/
	public function connected()
	{
	return $this->fp && $this->logged;
	}

	/**
	* Closes connection with logout.
	*/
	public function closeConnection()
	{
	if ($this->logged && $this->putLine($this->nextTag() . ' LOGOUT')) {
	$this->readReply();
	}

	$this->closeSocket();
	}

	/**
	* Executes SELECT command (if mailbox is already not in selected state)
	*
	* @param string $mailbox Mailbox name
	* @param array $qresync_data QRESYNC data (RFC5162)
	*
	* @return bool True on success, false on error
	*/
	public function select($mailbox, $qresync_data = null)
	{
	if (!strlen($mailbox)) {
	return false;
	}

	if ($this->selected === $mailbox) {
	return true;
	}

	$params = [$this->escape($mailbox)];

	// QRESYNC data items
	// 0. the last known UIDVALIDITY,
	// 1. the last known modification sequence,
	// 2. the optional set of known UIDs, and
	// 3. an optional parenthesized list of known sequence ranges and their
	// corresponding UIDs.
	if (!empty($qresync_data)) {
	if (!empty($qresync_data[2])) {
	$qresync_data[2] = self::compressMessageSet($qresync_data[2]);
	}

	$params[] = ['QRESYNC', $qresync_data];
	}

	list($code, $response) = $this->execute('SELECT', $params);

	if ($code == self::ERROR_OK) {
	$this->clear_mailbox_cache();

	$response = explode("\r\n", $response);
	foreach ($response as $line) {
	if (preg_match('/^\* OK \[/i', $line)) {
	$pos = strcspn($line, ' ]', 6);
	$token = strtoupper(substr($line, 6, $pos));
	$pos += 7;

	switch ($token) {
	case 'UIDNEXT':
	case 'UIDVALIDITY':
	case 'UNSEEN':
	if ($len = strspn($line, '0123456789', $pos)) {
	$this->data[$token] = (int) substr($line, $pos, $len);
	}
	break;

	case 'HIGHESTMODSEQ':
	if ($len = strspn($line, '0123456789', $pos)) {
	$this->data[$token] = (string) substr($line, $pos, $len);
	}
	break;

	case 'NOMODSEQ':
	$this->data[$token] = true;
	break;

	case 'PERMANENTFLAGS':
	$start = strpos($line, '(', $pos);
	$end = strrpos($line, ')');
	if ($start && $end) {
	$flags = substr($line, $start + 1, $end - $start - 1);
	$this->data[$token] = explode(' ', $flags);
	}
	break;
	}
	}
	else if (preg_match('/^\* ([0-9]+) (EXISTS\|RECENT\|FETCH)/i', $line, $match)) {
	$token = strtoupper($match[2]);
	switch ($token) {
	case 'EXISTS':
	case 'RECENT':
	$this->data[$token] = (int) $match[1];
	break;

	case 'FETCH':
	// QRESYNC FETCH response (RFC5162)
	$line = substr($line, strlen($match[0]));
	$fetch_data = $this->tokenizeResponse($line, 1);
	$data = ['id' => $match[1]];

	for ($i=0, $size=count($fetch_data); $i<$size; $i+=2) {
	$data[strtolower($fetch_data[$i])] = $fetch_data[$i+1];
	}

	$this->data['QRESYNC'][$data['uid']] = $data;
	break;
	}
	}
	// QRESYNC VANISHED response (RFC5162)
	else if (preg_match('/^\* VANISHED [()EARLIER]*/i', $line, $match)) {
	$line = substr($line, strlen($match[0]));
	$v_data = $this->tokenizeResponse($line, 1);

	$this->data['VANISHED'] = $v_data;
	}
	}

	$this->data['READ-WRITE'] = $this->resultcode != 'READ-ONLY';
	$this->selected = $mailbox;

	return true;
	}

	return false;
	}

	/**
	* Executes STATUS command
	*
	* @param string $mailbox Mailbox name
	* @param array $items Additional requested item names. By default
	* MESSAGES and UNSEEN are requested. Other defined
	* in RFC3501: UIDNEXT, UIDVALIDITY, RECENT
	*
	* @return array Status item-value hash
	* @since 0.5-beta
	*/
	public function status($mailbox, $items = [])
	{
	if (!strlen($mailbox)) {
	return false;
	}

	if (!in_array('MESSAGES', $items)) {
	$items[] = 'MESSAGES';
	}
	if (!in_array('UNSEEN', $items)) {
	$items[] = 'UNSEEN';
	}

	list($code, $response) = $this->execute('STATUS',
	[$this->escape($mailbox), '(' . implode(' ', $items) . ')'], 0, '/^\* STATUS /i');

	if ($code == self::ERROR_OK && $response) {
	$result = [];
	$response = substr($response, 9); // remove prefix "* STATUS "

	list($mbox, $items) = $this->tokenizeResponse($response, 2);

	// Fix for #1487859. Some buggy server returns not quoted
	// folder name with spaces. Let's try to handle this situation
	if (!is_array($items) && ($pos = strpos($response, '(')) !== false) {
	$response = substr($response, $pos);
	$items = $this->tokenizeResponse($response, 1);
	}

	if (!is_array($items)) {
	return $result;
	}

	for ($i=0, $len=count($items); $i<$len; $i += 2) {
	$result[$items[$i]] = $items[$i+1];
	}

	$this->data['STATUS:'.$mailbox] = $result;

	return $result;
	}

	return false;
	}

	/**
	* Executes EXPUNGE command
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $messages Message UIDs to expunge
	*
	* @return bool True on success, False on error
	*/
	public function expunge($mailbox, $messages = null)
	{
	if (!$this->select($mailbox)) {
	return false;
	}

	if (empty($this->data['READ-WRITE'])) {
	$this->setError(self::ERROR_READONLY, "Mailbox is read-only");
	return false;
	}

	// Clear internal status cache
	$this->clear_status_cache($mailbox);

	if (!empty($messages) && $messages != '*' && $this->hasCapability('UIDPLUS')) {
	$messages = self::compressMessageSet($messages);
	$result = $this->execute('UID EXPUNGE', [$messages], self::COMMAND_NORESPONSE);
	}
	else {
	$result = $this->execute('EXPUNGE', null, self::COMMAND_NORESPONSE);
	}

	if ($result == self::ERROR_OK) {
	$this->selected = null; // state has changed, need to reselect
	return true;
	}

	return false;
	}

	/**
	* Executes CLOSE command
	*
	* @return bool True on success, False on error
	* @since 0.5
	*/
	public function close()
	{
	$result = $this->execute('CLOSE', null, self::COMMAND_NORESPONSE);

	if ($result == self::ERROR_OK) {
	$this->selected = null;
	return true;
	}

	return false;
	}

	/**
	* Folder subscription (SUBSCRIBE)
	*
	* @param string $mailbox Mailbox name
	*
	* @return bool True on success, False on error
	*/
	public function subscribe($mailbox)
	{
	$result = $this->execute('SUBSCRIBE', [$this->escape($mailbox)], self::COMMAND_NORESPONSE);

	return $result == self::ERROR_OK;
	}

	/**
	* Folder unsubscription (UNSUBSCRIBE)
	*
	* @param string $mailbox Mailbox name
	*
	* @return bool True on success, False on error
	*/
	public function unsubscribe($mailbox)
	{
	$result = $this->execute('UNSUBSCRIBE', [$this->escape($mailbox)], self::COMMAND_NORESPONSE);

	return $result == self::ERROR_OK;
	}

	/**
	* Folder creation (CREATE)
	*
	* @param string $mailbox Mailbox name
	* @param array $types Optional folder types (RFC 6154)
	*
	* @return bool True on success, False on error
	*/
	public function createFolder($mailbox, $types = null)
	{
	$args = [$this->escape($mailbox)];

	// RFC 6154: CREATE-SPECIAL-USE
	if (!empty($types) && $this->getCapability('CREATE-SPECIAL-USE')) {
	$args[] = '(USE (' . implode(' ', $types) . '))';
	}

	$result = $this->execute('CREATE', $args, self::COMMAND_NORESPONSE);

	return $result == self::ERROR_OK;
	}

	/**
	* Folder renaming (RENAME)
	*
	* @param string $mailbox Mailbox name
	*
	* @return bool True on success, False on error
	*/
	public function renameFolder($from, $to)
	{
	$result = $this->execute('RENAME', [$this->escape($from), $this->escape($to)], self::COMMAND_NORESPONSE);

	return $result == self::ERROR_OK;
	}

	/**
	* Executes DELETE command
	*
	* @param string $mailbox Mailbox name
	*
	* @return bool True on success, False on error
	*/
	public function deleteFolder($mailbox)
	{
	// Unselect the folder to prevent "BYE Fatal error: Mailbox has been (re)moved" on Cyrus IMAP
	if ($this->selected === $mailbox && $this->hasCapability('UNSELECT')) {
	$this->execute('UNSELECT', [], self::COMMAND_NORESPONSE);
	}

	$result = $this->execute('DELETE', [$this->escape($mailbox)], self::COMMAND_NORESPONSE);

	return $result == self::ERROR_OK;
	}

	/**
	* Removes all messages in a folder
	*
	* @param string $mailbox Mailbox name
	*
	* @return bool True on success, False on error
	*/
	public function clearFolder($mailbox)
	{
	if ($this->countMessages($mailbox) > 0) {
	$res = $this->flag($mailbox, '1:*', 'DELETED');
	}
	else {
	return true;
	}

	if (!empty($res)) {
	if ($this->selected === $mailbox) {
	$res = $this->close();
	}
	else {
	$res = $this->expunge($mailbox);
	}

	return $res;
	}

	return false;
	}

	/**
	* Returns list of mailboxes
	*
	* @param string $ref Reference name
	* @param string $mailbox Mailbox name
	* @param array $return_opts (see self::_listMailboxes)
	* @param array $select_opts (see self::_listMailboxes)
	*
	* @return array\|bool List of mailboxes or hash of options if STATUS/MYRIGHTS response
	* is requested, False on error.
	*/
	public function listMailboxes($ref, $mailbox, $return_opts = [], $select_opts = [])
	{
	return $this->_listMailboxes($ref, $mailbox, false, $return_opts, $select_opts);
	}

	/**
	* Returns list of subscribed mailboxes
	*
	* @param string $ref Reference name
	* @param string $mailbox Mailbox name
	* @param array $return_opts (see self::_listMailboxes)
	*
	* @return array\|bool List of mailboxes or hash of options if STATUS/MYRIGHTS response
	* is requested, False on error.
	*/
	public function listSubscribed($ref, $mailbox, $return_opts = [])
	{
	return $this->_listMailboxes($ref, $mailbox, true, $return_opts, null);
	}

	/**
	* IMAP LIST/LSUB command
	*
	* @param string $ref Reference name
	* @param string $mailbox Mailbox name
	* @param bool $subscribed Enables returning subscribed mailboxes only
	* @param array $return_opts List of RETURN options (RFC5819: LIST-STATUS, RFC5258: LIST-EXTENDED)
	* Possible: MESSAGES, RECENT, UIDNEXT, UIDVALIDITY, UNSEEN,
	* MYRIGHTS, SUBSCRIBED, CHILDREN
	* @param array $select_opts List of selection options (RFC5258: LIST-EXTENDED)
	* Possible: SUBSCRIBED, RECURSIVEMATCH, REMOTE,
	* SPECIAL-USE (RFC6154)
	*
	* @return array\|bool List of mailboxes or hash of options if STATUS/MYRIGHTS response
	* is requested, False on error.
	*/
	protected function _listMailboxes($ref, $mailbox, $subscribed = false, $return_opts = [], $select_opts = [])
	{
	if (!strlen($mailbox)) {
	$mailbox = '*';
	}

	$lstatus = false;
	$args = [];
	$rets = [];

	if (!empty($select_opts) && $this->getCapability('LIST-EXTENDED')) {
	$select_opts = (array) $select_opts;

	$args[] = '(' . implode(' ', $select_opts) . ')';
	}

	$args[] = $this->escape($ref);
	$args[] = $this->escape($mailbox);

	if (!empty($return_opts) && $this->getCapability('LIST-EXTENDED')) {
	$ext_opts = ['SUBSCRIBED', 'CHILDREN'];
	$rets = array_intersect($return_opts, $ext_opts);
	$return_opts = array_diff($return_opts, $rets);
	}

	if (!empty($return_opts) && $this->getCapability('LIST-STATUS')) {
	$lstatus = true;
	$status_opts = ['MESSAGES', 'RECENT', 'UIDNEXT', 'UIDVALIDITY', 'UNSEEN', 'SIZE'];
	$opts = array_diff($return_opts, $status_opts);
	$status_opts = array_diff($return_opts, $opts);

	if (!empty($status_opts)) {
	$rets[] = 'STATUS (' . implode(' ', $status_opts) . ')';
	}

	if (!empty($opts)) {
	$rets = array_merge($rets, $opts);
	}
	}

	if (!empty($rets)) {
	$args[] = 'RETURN (' . implode(' ', $rets) . ')';
	}

	list($code, $response) = $this->execute($subscribed ? 'LSUB' : 'LIST', $args);

	if ($code == self::ERROR_OK) {
	$folders = [];
	$last = 0;
	$pos = 0;
	$response .= "\r\n";

	while ($pos = strpos($response, "\r\n", $pos+1)) {
	// literal string, not real end-of-command-line
	if ($response[$pos-1] == '}') {
	continue;
	}

	$line = substr($response, $last, $pos - $last);
	$last = $pos + 2;

	if (!preg_match('/^\* (LIST\|LSUB\|STATUS\|MYRIGHTS) /i', $line, $m)) {
	continue;
	}

	$cmd = strtoupper($m[1]);
	$line = substr($line, strlen($m[0]));

	// * LIST (<options>) <delimiter> <mailbox>
	if ($cmd == 'LIST' \|\| $cmd == 'LSUB') {
	list($opts, $delim, $mailbox) = $this->tokenizeResponse($line, 3);

	// Remove redundant separator at the end of folder name, UW-IMAP bug? (#1488879)
	if ($delim) {
	$mailbox = rtrim($mailbox, $delim);
	}

	// Add to result array
	if (!$lstatus) {
	$folders[] = $mailbox;
	}
	else {
	$folders[$mailbox] = [];
	}

	// store folder options
	if ($cmd == 'LIST') {
	// Add to options array
	if (empty($this->data['LIST'][$mailbox])) {
	$this->data['LIST'][$mailbox] = $opts;
	}
	else if (!empty($opts)) {
	$this->data['LIST'][$mailbox] = array_unique(array_merge(
	$this->data['LIST'][$mailbox], $opts));
	}
	}
	}
	else if ($lstatus) {
	// * STATUS <mailbox> (<result>)
	if ($cmd == 'STATUS') {
	list($mailbox, $status) = $this->tokenizeResponse($line, 2);

	for ($i=0, $len=count($status); $i<$len; $i += 2) {
	list($name, $value) = $this->tokenizeResponse($status, 2);
	$folders[$mailbox][$name] = $value;
	}
	}
	// * MYRIGHTS <mailbox> <acl>
	else if ($cmd == 'MYRIGHTS') {
	list($mailbox, $acl) = $this->tokenizeResponse($line, 2);
	$folders[$mailbox]['MYRIGHTS'] = $acl;
	}
	}
	}

	return $folders;
	}

	return false;
	}

	/**
	* Returns count of all messages in a folder
	*
	* @param string $mailbox Mailbox name
	*
	* @return int Number of messages, False on error
	*/
	public function countMessages($mailbox)
	{
	if ($this->selected === $mailbox && isset($this->data['EXISTS'])) {
	return $this->data['EXISTS'];
	}

	// Check internal cache
	if (!empty($this->data['STATUS:'.$mailbox])) {
	$cache = $this->data['STATUS:'.$mailbox];
	if (isset($cache['MESSAGES'])) {
	return (int) $cache['MESSAGES'];
	}
	}

	// Try STATUS (should be faster than SELECT)
	$counts = $this->status($mailbox);
	if (is_array($counts)) {
	return (int) $counts['MESSAGES'];
	}

	return false;
	}

	/**
	* Returns count of messages with \Recent flag in a folder
	*
	* @param string $mailbox Mailbox name
	*
	* @return int Number of messages, False on error
	*/
	public function countRecent($mailbox)
	{
	if ($this->selected === $mailbox && isset($this->data['RECENT'])) {
	return $this->data['RECENT'];
	}

	// Check internal cache
	$cache = $this->data['STATUS:'.$mailbox];
	if (!empty($cache) && isset($cache['RECENT'])) {
	return (int) $cache['RECENT'];
	}

	// Try STATUS (should be faster than SELECT)
	$counts = $this->status($mailbox, ['RECENT']);
	if (is_array($counts)) {
	return (int) $counts['RECENT'];
	}

	return false;
	}

	/**
	* Returns count of messages without \Seen flag in a specified folder
	*
	* @param string $mailbox Mailbox name
	*
	* @return int Number of messages, False on error
	*/
	public function countUnseen($mailbox)
	{
	// Check internal cache
	if (!empty($this->data['STATUS:'.$mailbox])) {
	$cache = $this->data['STATUS:'.$mailbox];
	if (isset($cache['UNSEEN'])) {
	return (int) $cache['UNSEEN'];
	}
	}

	// Try STATUS (should be faster than SELECT+SEARCH)
	$counts = $this->status($mailbox);
	if (is_array($counts)) {
	return (int) $counts['UNSEEN'];
	}

	// Invoke SEARCH as a fallback
	$index = $this->search($mailbox, 'ALL UNSEEN', false, ['COUNT']);
	if (!$index->is_error()) {
	return $index->count();
	}

	return false;
	}

	/**
	* Executes ID command (RFC2971)
	*
	* @param array $items Client identification information key/value hash
	*
	* @return array\|false Server identification information key/value hash, False on error
	* @since 0.6
	*/
	public function id($items = [])
	{
	if (is_array($items) && !empty($items)) {
	foreach ($items as $key => $value) {
	$args[] = $this->escape($key, true);
	$args[] = $this->escape($value, true);
	}
	}

	list($code, $response) = $this->execute('ID',
	[!empty($args) ? '(' . implode(' ', (array) $args) . ')' : $this->escape(null)],
	0, '/^\* ID /i'
	);

	if ($code == self::ERROR_OK && $response) {
	$response = substr($response, 5); // remove prefix "* ID "
	$items = $this->tokenizeResponse($response, 1);
	$result = [];

	if (is_array($items)) {
	for ($i=0, $len=count($items); $i<$len; $i += 2) {
	$result[$items[$i]] = $items[$i+1];
	}
	}

	return $result;
	}

	return false;
	}

	/**
	* Executes ENABLE command (RFC5161)
	*
	* @param mixed $extension Extension name to enable (or array of names)
	*
	* @return array\|bool List of enabled extensions, False on error
	* @since 0.6
	*/
	public function enable($extension)
	{
	if (empty($extension)) {
	return false;
	}

	if (!$this->hasCapability('ENABLE')) {
	return false;
	}

	if (!is_array($extension)) {
	$extension = [$extension];
	}

	if (!empty($this->extensions_enabled)) {
	// check if all extensions are already enabled
	$diff = array_diff($extension, $this->extensions_enabled);

	if (empty($diff)) {
	return $extension;
	}

	// Make sure the mailbox isn't selected, before enabling extension(s)
	if ($this->selected !== null) {
	$this->close();
	}
	}

	list($code, $response) = $this->execute('ENABLE', $extension, 0, '/^\* ENABLED /i');

	if ($code == self::ERROR_OK && $response) {
	$response = substr($response, 10); // remove prefix "* ENABLED "
	$result = (array) $this->tokenizeResponse($response);

	$this->extensions_enabled = array_unique(array_merge((array)$this->extensions_enabled, $result));

	return $this->extensions_enabled;
	}

	return false;
	}

	/**
	* Executes SORT command
	*
	* @param string $mailbox Mailbox name
	* @param string $field Field to sort by (ARRIVAL, CC, DATE, FROM, SIZE, SUBJECT, TO)
	* @param string $criteria Searching criteria
	* @param bool $return_uid Enables UID SORT usage
	* @param string $encoding Character set
	*
	* @return rcube_result_index Response data
	*/
	public function sort($mailbox, $field = 'ARRIVAL', $criteria = '', $return_uid = false, $encoding = 'US-ASCII')
	{
	$old_sel = $this->selected;
	$supported = ['ARRIVAL', 'CC', 'DATE', 'FROM', 'SIZE', 'SUBJECT', 'TO'];
	$field = strtoupper($field);

	if ($field == 'INTERNALDATE') {
	$field = 'ARRIVAL';
	}

	if (!in_array($field, $supported)) {
	return new rcube_result_index($mailbox);
	}

	if (!$this->select($mailbox)) {
	return new rcube_result_index($mailbox);
	}

	// return empty result when folder is empty and we're just after SELECT
	if ($old_sel != $mailbox && empty($this->data['EXISTS'])) {
	return new rcube_result_index($mailbox, '* SORT');
	}

	// RFC 5957: SORT=DISPLAY
	if (($field == 'FROM' \|\| $field == 'TO') && $this->getCapability('SORT=DISPLAY')) {
	$field = 'DISPLAY' . $field;
	}

	$encoding = $encoding ? trim($encoding) : 'US-ASCII';
	$criteria = $criteria ? 'ALL ' . trim($criteria) : 'ALL';

	list($code, $response) = $this->execute($return_uid ? 'UID SORT' : 'SORT',
	["($field)", $encoding, $criteria]);

	if ($code != self::ERROR_OK) {
	$response = null;
	}

	return new rcube_result_index($mailbox, $response);
	}

	/**
	* Executes THREAD command
	*
	* @param string $mailbox Mailbox name
	* @param string $algorithm Threading algorithm (ORDEREDSUBJECT, REFERENCES, REFS)
	* @param string $criteria Searching criteria
	* @param bool $return_uid Enables UIDs in result instead of sequence numbers
	* @param string $encoding Character set
	*
	* @return rcube_result_thread Thread data
	*/
	public function thread($mailbox, $algorithm = 'REFERENCES', $criteria = '', $return_uid = false, $encoding = 'US-ASCII')
	{
	$old_sel = $this->selected;

	if (!$this->select($mailbox)) {
	return new rcube_result_thread($mailbox);
	}

	// return empty result when folder is empty and we're just after SELECT
	if ($old_sel != $mailbox && !$this->data['EXISTS']) {
	return new rcube_result_thread($mailbox, '* THREAD');
	}

	$encoding = $encoding ? trim($encoding) : 'US-ASCII';
	$algorithm = $algorithm ? trim($algorithm) : 'REFERENCES';
	$criteria = $criteria ? 'ALL '.trim($criteria) : 'ALL';

	list($code, $response) = $this->execute($return_uid ? 'UID THREAD' : 'THREAD',
	[$algorithm, $encoding, $criteria]);

	if ($code != self::ERROR_OK) {
	$response = null;
	}

	return new rcube_result_thread($mailbox, $response);
	}

	/**
	* Executes SEARCH command
	*
	* @param string $mailbox Mailbox name
	* @param string $criteria Searching criteria
	* @param bool $return_uid Enable UID in result instead of sequence ID
	* @param array $items Return items (MIN, MAX, COUNT, ALL)
	*
	* @return rcube_result_index Result data
	*/
	public function search($mailbox, $criteria, $return_uid = false, $items = [])
	{
	$old_sel = $this->selected;

	if (!$this->select($mailbox)) {
	return new rcube_result_index($mailbox);
	}

	// return empty result when folder is empty and we're just after SELECT
	if ($old_sel != $mailbox && !$this->data['EXISTS']) {
	return new rcube_result_index($mailbox, '* SEARCH');
	}

	// If ESEARCH is supported always use ALL
	// but not when items are specified or using simple id2uid search
	if (empty($items) && preg_match('/[^0-9]/', $criteria)) {
	$items = ['ALL'];
	}

	$esearch = empty($items) ? false : $this->getCapability('ESEARCH');
	$criteria = trim($criteria);
	$params = '';

	// RFC4731: ESEARCH
	if (!empty($items) && $esearch) {
	$params .= 'RETURN (' . implode(' ', $items) . ')';
	}

	if (!empty($criteria)) {
	$params .= ($params ? ' ' : '') . $criteria;
	}
	else {
	$params .= 'ALL';
	}

	list($code, $response) = $this->execute($return_uid ? 'UID SEARCH' : 'SEARCH', [$params]);

	if ($code != self::ERROR_OK) {
	$response = null;
	}

	return new rcube_result_index($mailbox, $response);
	}

	/**
	* Simulates SORT command by using FETCH and sorting.
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $message_set Searching criteria (list of messages to return)
	* @param string $index_field Field to sort by (ARRIVAL, CC, DATE, FROM, SIZE, SUBJECT, TO)
	* @param bool $skip_deleted Makes that DELETED messages will be skipped
	* @param bool $uidfetch Enables UID FETCH usage
	* @param bool $return_uid Enables returning UIDs instead of IDs
	*
	* @return rcube_result_index Response data
	*/
	public function index($mailbox, $message_set, $index_field = '', $skip_deleted = true,
	$uidfetch = false, $return_uid = false)
	{
	$msg_index = $this->fetchHeaderIndex($mailbox, $message_set,
	$index_field, $skip_deleted, $uidfetch, $return_uid);

	if (!empty($msg_index)) {
	asort($msg_index); // ASC
	$msg_index = array_keys($msg_index);
	$msg_index = '* SEARCH ' . implode(' ', $msg_index);
	}
	else {
	$msg_index = is_array($msg_index) ? '* SEARCH' : null;
	}

	return new rcube_result_index($mailbox, $msg_index);
	}

	/**
	* Fetches specified header/data value for a set of messages.
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $message_set Searching criteria (list of messages to return)
	* @param string $index_field Field to sort by (ARRIVAL, CC, DATE, FROM, SIZE, SUBJECT, TO)
	* @param bool $skip_deleted Makes that DELETED messages will be skipped
	* @param bool $uidfetch Enables UID FETCH usage
	* @param bool $return_uid Enables returning UIDs instead of IDs
	*
	* @return array\|bool List of header values or False on failure
	*/
	public function fetchHeaderIndex($mailbox, $message_set, $index_field = '', $skip_deleted = true,
	$uidfetch = false, $return_uid = false)
	{
	// Validate input
	if (is_array($message_set)) {
	if (!($message_set = $this->compressMessageSet($message_set))) {
	return false;
	}
	}
	else if (empty($message_set)) {
	return false;
	}
	else if (strpos($message_set, ':')) {
	list($from_idx, $to_idx) = explode(':', $message_set);
	if ($to_idx != '*' && (int) $from_idx > (int) $to_idx) {
	return false;
	}
	}

	$index_field = empty($index_field) ? 'DATE' : strtoupper($index_field);

	$supported = [
	'DATE' => 1,
	'INTERNALDATE' => 4,
	'ARRIVAL' => 4,
	'FROM' => 1,
	'REPLY-TO' => 1,
	'SENDER' => 1,
	'TO' => 1,
	'CC' => 1,
	'SUBJECT' => 1,
	'UID' => 2,
	'SIZE' => 2,
	'SEEN' => 3,
	'RECENT' => 3,
	'DELETED' => 3,
	];

	if (empty($supported[$index_field])) {
	return false;
	}

	$mode = $supported[$index_field];

	// Select the mailbox
	if (!$this->select($mailbox)) {
	return false;
	}

	// build FETCH command string
	$key = $this->nextTag();
	$cmd = $uidfetch ? 'UID FETCH' : 'FETCH';
	$fields = [];

	if ($return_uid) {
	$fields[] = 'UID';
	}
	if ($skip_deleted) {
	$fields[] = 'FLAGS';
	}

	if ($mode == 1) {
	if ($index_field == 'DATE') {
	$fields[] = 'INTERNALDATE';
	}
	$fields[] = "BODY.PEEK[HEADER.FIELDS ($index_field)]";
	}
	else if ($mode == 2) {
	if ($index_field == 'SIZE') {
	$fields[] = 'RFC822.SIZE';
	}
	else if (!$return_uid \|\| $index_field != 'UID') {
	$fields[] = $index_field;
	}
	}
	else if ($mode == 3 && !$skip_deleted) {
	$fields[] = 'FLAGS';
	}
	else if ($mode == 4) {
	$fields[] = 'INTERNALDATE';
	}

	$request = "$key $cmd $message_set (" . implode(' ', $fields) . ")";

	if (!$this->putLine($request)) {
	$this->setError(self::ERROR_COMMAND, "Failed to send $cmd command");
	return false;
	}

	$result = [];

	do {
	$line = rtrim($this->readLine(200));
	$line = $this->multLine($line);

	if (preg_match('/^\* ([0-9]+) FETCH/', $line, $m)) {
	$id = $m[1];
	$flags = null;

	if ($return_uid) {
	if (preg_match('/UID ([0-9]+)/', $line, $matches)) {
	$id = (int) $matches[1];
	}
	else {
	continue;
	}
	}

	if ($skip_deleted && preg_match('/FLAGS $([^)]+)$/', $line, $matches)) {
	$flags = explode(' ', strtoupper($matches[1]));
	if (in_array('\\DELETED', $flags)) {
	continue;
	}
	}

	if ($mode == 1 && $index_field == 'DATE') {
	if (preg_match('/BODY\[HEADER\.FIELDS $"DATE"$\] (.*)/', $line, $matches)) {
	$value = preg_replace(['/^"*[a-z]+:/i'], '', $matches[1]);
	$value = trim($value);
	$result[$id] = rcube_utils::strtotime($value);
	}
	// non-existent/empty Date: header, use INTERNALDATE
	if (empty($result[$id])) {
	if (preg_match('/INTERNALDATE "([^"]+)"/', $line, $matches)) {
	$result[$id] = rcube_utils::strtotime($matches[1]);
	}
	else {
	$result[$id] = 0;
	}
	}
	}
	else if ($mode == 1) {
	if (preg_match('/BODY\[HEADER\.FIELDS $"?(FROM\|REPLY-TO\|SENDER\|TO\|SUBJECT)"?$\] (.*)/', $line, $matches)) {
	$value = preg_replace(['/^"*[a-z]+:/i', '/\s+$/sm'], ['', ''], $matches[2]);
	$result[$id] = trim($value);
	}
	else {
	$result[$id] = '';
	}
	}
	else if ($mode == 2) {
	if (preg_match('/' . $index_field . ' ([0-9]+)/', $line, $matches)) {
	$result[$id] = trim($matches[1]);
	}
	else {
	$result[$id] = 0;
	}
	}
	else if ($mode == 3) {
	if (!$flags && preg_match('/FLAGS $([^)]+)$/', $line, $matches)) {
	$flags = explode(' ', $matches[1]);
	}
	$result[$id] = in_array("\\".$index_field, (array) $flags) ? 1 : 0;
	}
	else if ($mode == 4) {
	if (preg_match('/INTERNALDATE "([^"]+)"/', $line, $matches)) {
	$result[$id] = rcube_utils::strtotime($matches[1]);
	}
	else {
	$result[$id] = 0;
	}
	}
	}
	}
	while (!$this->startsWith($line, $key, true, true));

	return $result;
	}

	/**
	* Returns message sequence identifier
	*
	* @param string $mailbox Mailbox name
	* @param int $uid Message unique identifier (UID)
	*
	* @return int Message sequence identifier
	*/
	public function UID2ID($mailbox, $uid)
	{
	if ($uid > 0) {
	$index = $this->search($mailbox, "UID $uid");

	if ($index->count() == 1) {
	$arr = $index->get();
	return (int) $arr[0];
	}
	}
	}

	/**
	* Returns message unique identifier (UID)
	*
	* @param string $mailbox Mailbox name
	* @param int $uid Message sequence identifier
	*
	* @return int Message unique identifier
	*/
	public function ID2UID($mailbox, $id)
	{
	if (empty($id) \|\| $id < 0) {
	return null;
	}

	if (!$this->select($mailbox)) {
	return null;
	}

	if (!empty($this->data['UID-MAP'][$id])) {
	return $this->data['UID-MAP'][$id];
	}

	if (isset($this->data['EXISTS']) && $id > $this->data['EXISTS']) {
	return null;
	}

	$index = $this->search($mailbox, $id, true);

	if ($index->count() == 1) {
	$arr = $index->get();
	return $this->data['UID-MAP'][$id] = (int) $arr[0];
	}
	}

	/**
	* Sets flag of the message(s)
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $messages Message UID(s)
	* @param string $flag Flag name
	*
	* @return bool True on success, False on failure
	*/
	public function flag($mailbox, $messages, $flag)
	{
	return $this->modFlag($mailbox, $messages, $flag, '+');
	}

	/**
	* Unsets flag of the message(s)
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $messages Message UID(s)
	* @param string $flag Flag name
	*
	* @return bool True on success, False on failure
	*/
	public function unflag($mailbox, $messages, $flag)
	{
	return $this->modFlag($mailbox, $messages, $flag, '-');
	}

	/**
	* Changes flag of the message(s)
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $messages Message UID(s)
	* @param string $flag Flag name
	* @param string $mod Modifier [+\|-]. Default: "+".
	*
	* @return bool True on success, False on failure
	*/
	protected function modFlag($mailbox, $messages, $flag, $mod = '+')
	{
	if (!$flag) {
	return false;
	}

	if (!$this->select($mailbox)) {
	return false;
	}

	if (empty($this->data['READ-WRITE'])) {
	$this->setError(self::ERROR_READONLY, "Mailbox is read-only");
	return false;
	}

	if (!empty($this->flags[strtoupper($flag)])) {
	$flag = $this->flags[strtoupper($flag)];
	}

	// if PERMANENTFLAGS is not specified all flags are allowed
	if (!empty($this->data['PERMANENTFLAGS'])
	&& !in_array($flag, (array) $this->data['PERMANENTFLAGS'])
	&& !in_array('\\*', (array) $this->data['PERMANENTFLAGS'])
	) {
	return false;
	}

	// Clear internal status cache
	if ($flag == 'SEEN') {
	unset($this->data['STATUS:'.$mailbox]['UNSEEN']);
	}

	if ($mod != '+' && $mod != '-') {
	$mod = '+';
	}

	$result = $this->execute('UID STORE',
	[$this->compressMessageSet($messages), $mod . 'FLAGS.SILENT', "($flag)"],
	self::COMMAND_NORESPONSE
	);

	return $result == self::ERROR_OK;
	}

	/**
	* Copies message(s) from one folder to another
	*
	* @param string\|array $messages Message UID(s)
	* @param string $from Mailbox name
	* @param string $to Destination mailbox name
	*
	* @return bool True on success, False on failure
	*/
	public function copy($messages, $from, $to)
	{
	// Clear last COPYUID data
	unset($this->data['COPYUID']);

	if (!$this->select($from)) {
	return false;
	}

	// Clear internal status cache
	unset($this->data['STATUS:'.$to]);

	$result = $this->execute('UID COPY',
	[$this->compressMessageSet($messages), $this->escape($to)],
	self::COMMAND_NORESPONSE
	);

	return $result == self::ERROR_OK;
	}

	/**
	* Moves message(s) from one folder to another.
	*
	* @param string\|array $messages Message UID(s)
	* @param string $from Mailbox name
	* @param string $to Destination mailbox name
	*
	* @return bool True on success, False on failure
	*/
	public function move($messages, $from, $to)
	{
	if (!$this->select($from)) {
	return false;
	}

	if (empty($this->data['READ-WRITE'])) {
	$this->setError(self::ERROR_READONLY, "Mailbox is read-only");
	return false;
	}

	// use MOVE command (RFC 6851)
	if ($this->hasCapability('MOVE')) {
	// Clear last COPYUID data
	unset($this->data['COPYUID']);

	// Clear internal status cache
	unset($this->data['STATUS:'.$to]);
	$this->clear_status_cache($from);

	$result = $this->execute('UID MOVE',
	[$this->compressMessageSet($messages), $this->escape($to)],
	self::COMMAND_NORESPONSE
	);

	return $result == self::ERROR_OK;
	}

	// use COPY + STORE +FLAGS.SILENT \Deleted + EXPUNGE
	$result = $this->copy($messages, $from, $to);

	if ($result) {
	// Clear internal status cache
	unset($this->data['STATUS:'.$from]);

	$result = $this->flag($from, $messages, 'DELETED');

	if ($messages == '*') {
	// CLOSE+SELECT should be faster than EXPUNGE
	$this->close();
	}
	else {
	$this->expunge($from, $messages);
	}
	}

	return $result;
	}

	/**
	* FETCH command (RFC3501)
	*
	* @param string $mailbox Mailbox name
	* @param mixed $message_set Message(s) sequence identifier(s) or UID(s)
	* @param bool $is_uid True if $message_set contains UIDs
	* @param array $query_items FETCH command data items
	* @param string $mod_seq Modification sequence for CHANGEDSINCE (RFC4551) query
	* @param bool $vanished Enables VANISHED parameter (RFC5162) for CHANGEDSINCE query
	*
	* @return array List of rcube_message_header elements, False on error
	* @since 0.6
	*/
	public function fetch($mailbox, $message_set, $is_uid = false, $query_items = [],
	$mod_seq = null, $vanished = false)
	{
	if (!$this->select($mailbox)) {
	return false;
	}

	$message_set = $this->compressMessageSet($message_set);
	$result = [];

	$key = $this->nextTag();
	$cmd = ($is_uid ? 'UID ' : '') . 'FETCH';
	$request = "$key $cmd $message_set (" . implode(' ', $query_items) . ")";

	if ($mod_seq !== null && $this->hasCapability('CONDSTORE')) {
	$request .= " (CHANGEDSINCE $mod_seq" . ($vanished ? " VANISHED" : '') .")";
	}

	if (!$this->putLine($request)) {
	$this->setError(self::ERROR_COMMAND, "Failed to send $cmd command");
	return false;
	}

	do {
	$line = $this->readFullLine(4096);

	if (!$line) {
	break;
	}

	// Sample reply line:
	// * 321 FETCH (UID 2417 RFC822.SIZE 2730 FLAGS (\Seen)
	// INTERNALDATE "16-Nov-2008 21:08:46 +0100" BODYSTRUCTURE (...)
	// BODY[HEADER.FIELDS ...

	if (preg_match('/^\* ([0-9]+) FETCH/', $line, $m)) {
	$id = intval($m[1]);

	$result[$id] = new rcube_message_header;
	$result[$id]->id = $id;
	$result[$id]->subject = '';
	$result[$id]->messageID = 'mid:' . $id;

	$headers = null;
	$line = substr($line, strlen($m[0]) + 2);

	// Tokenize response and assign to object properties
	while (($tokens = $this->tokenizeResponse($line, 2)) && count($tokens) == 2) {
	list($name, $value) = $tokens;
	if ($name == 'UID') {
	$result[$id]->uid = intval($value);
	}
	else if ($name == 'RFC822.SIZE') {
	$result[$id]->size = intval($value);
	}
	else if ($name == 'RFC822.TEXT') {
	$result[$id]->body = $value;
	}
	else if ($name == 'INTERNALDATE') {
	$result[$id]->internaldate = $value;
	$result[$id]->date = $value;
	$result[$id]->timestamp = rcube_utils::strtotime($value);
	}
	else if ($name == 'FLAGS') {
	if (!empty($value)) {
	foreach ((array)$value as $flag) {
	$flag = str_replace(['$', "\\"], '', $flag);
	$flag = strtoupper($flag);

	$result[$id]->flags[$flag] = true;
	}
	}
	}
	else if ($name == 'MODSEQ') {
	$result[$id]->modseq = $value[0];
	}
	else if ($name == 'ENVELOPE') {
	$result[$id]->envelope = $value;
	}
	else if ($name == 'BODYSTRUCTURE' \|\| ($name == 'BODY' && count($value) > 2)) {
	if (!is_array($value[0]) && (strtolower($value[0]) == 'message' && strtolower($value[1]) == 'rfc822')) {
	$value = [$value];
	}
	$result[$id]->bodystructure = $value;
	}
	else if ($name == 'RFC822') {
	$result[$id]->body = $value;
	}
	else if (stripos($name, 'BODY[') === 0) {
	$name = str_replace(']', '', substr($name, 5));

	if ($name == 'HEADER.FIELDS') {
	// skip ']' after headers list
	$this->tokenizeResponse($line, 1);
	$headers = $this->tokenizeResponse($line, 1);
	}
	else if (strlen($name)) {
	$result[$id]->bodypart[$name] = $value;
	}
	else {
	$result[$id]->body = $value;
	}
	}
	}

	// create array with header field:data
	if (!empty($headers)) {
	$headers = explode("\n", trim($headers));
	$lines = [];
	$ln = 0;

	foreach ($headers as $resln) {
	if (!isset($resln[0]) \|\| ord($resln[0]) <= 32) {
	$lines[$ln] = ($lines[$ln] ?? '') . (empty($lines[$ln]) ? '' : "\n") . trim($resln);
	}
	else {
	$lines[++$ln] = trim($resln);
	}
	}

	foreach ($lines as $str) {
	if (strpos($str, ':') === false) {
	continue;
	}

	list($field, $string) = explode(':', $str, 2);

	$field = strtolower($field);
	$string = preg_replace('/\n[\t\s]*/', ' ', trim($string));

	switch ($field) {
	case 'date';
	$string = substr($string, 0, 128);
	$result[$id]->date = $string;
	$result[$id]->timestamp = rcube_utils::strtotime($string);
	break;
	case 'to':
	$result[$id]->to = preg_replace('/undisclosed-recipients:[;,]*/', '', $string);
	break;
	case 'from':
	case 'subject':
	$string = substr($string, 0, 2048);
	case 'cc':
	case 'bcc':
	case 'references':
	$result[$id]->{$field} = $string;
	break;
	case 'reply-to':
	$result[$id]->replyto = $string;
	break;
	case 'content-transfer-encoding':
	$result[$id]->encoding = substr($string, 0, 32);
	break;
	case 'content-type':
	$ctype_parts = preg_split('/[; ]+/', $string);
	$result[$id]->ctype = strtolower(array_first($ctype_parts));
	if (preg_match('/charset\s=\s"?([a-z0-9\-\.\_]+)"?/i', $string, $regs)) {
	$result[$id]->charset = $regs[1];
	}
	break;
	case 'in-reply-to':
	$result[$id]->in_reply_to = str_replace(["\n", '<', '>'], '', $string);
	break;
	case 'disposition-notification-to':
	case 'x-confirm-reading-to':
	$result[$id]->mdn_to = substr($string, 0, 2048);
	break;
	case 'message-id':
	$result[$id]->messageID = substr($string, 0, 2048);
	break;
	case 'x-priority':
	if (preg_match('/^(\d+)/', $string, $matches)) {
	$result[$id]->priority = intval($matches[1]);
	}
	break;
	default:
	if (strlen($field) < 3) {
	break;
	}
	if (!empty($result[$id]->others[$field])) {
	$string = array_merge((array) $result[$id]->others[$field], (array) $string);
	}
	$result[$id]->others[$field] = $string;
	}
	}
	}
	}
	// VANISHED response (QRESYNC RFC5162)
	// Sample: * VANISHED (EARLIER) 300:310,405,411
	else if (preg_match('/^\* VANISHED [()EARLIER]*/i', $line, $match)) {
	$line = substr($line, strlen($match[0]));
	$v_data = $this->tokenizeResponse($line, 1);

	$this->data['VANISHED'] = $v_data;
	}
	}
	while (!$this->startsWith($line, $key, true));

	return $result;
	}

	/**
	* Returns message(s) data (flags, headers, etc.)
	*
	* @param string $mailbox Mailbox name
	* @param mixed $message_set Message(s) sequence identifier(s) or UID(s)
	* @param bool $is_uid True if $message_set contains UIDs
	* @param bool $bodystr Enable to add BODYSTRUCTURE data to the result
	* @param array $add_headers List of additional headers
	*
	* @return bool\|array List of rcube_message_header elements, False on error
	*/
	public function fetchHeaders($mailbox, $message_set, $is_uid = false, $bodystr = false, $add_headers = [])
	{
	$query_items = ['UID', 'RFC822.SIZE', 'FLAGS', 'INTERNALDATE'];
	$headers = ['DATE', 'FROM', 'TO', 'SUBJECT', 'CONTENT-TYPE', 'CC', 'REPLY-TO',
	'LIST-POST', 'DISPOSITION-NOTIFICATION-TO', 'X-PRIORITY'];

	if (!empty($add_headers)) {
	$add_headers = array_map('strtoupper', $add_headers);
	$headers = array_unique(array_merge($headers, $add_headers));
	}

	if ($bodystr) {
	$query_items[] = 'BODYSTRUCTURE';
	}

	$query_items[] = 'BODY.PEEK[HEADER.FIELDS (' . implode(' ', $headers) . ')]';

	return $this->fetch($mailbox, $message_set, $is_uid, $query_items);
	}

	/**
	* Returns message data (flags, headers, etc.)
	*
	* @param string $mailbox Mailbox name
	* @param int $id Message sequence identifier or UID
	* @param bool $is_uid True if $id is an UID
	* @param bool $bodystr Enable to add BODYSTRUCTURE data to the result
	* @param array $add_headers List of additional headers
	*
	* @return bool\|rcube_message_header Message data, False on error
	*/
	public function fetchHeader($mailbox, $id, $is_uid = false, $bodystr = false, $add_headers = [])
	{
	$a = $this->fetchHeaders($mailbox, $id, $is_uid, $bodystr, $add_headers);

	if (is_array($a)) {
	return array_first($a);
	}

	return false;
	}

	/**
	* Sort messages by specified header field
	*
	* @param array $messages Array of rcube_message_header objects
	* @param string $field Name of the property to sort by
	* @param string $order Sorting order (ASC\|DESC)
	*
	* @return array Sorted input array
	*/
	public static function sortHeaders($messages, $field, $order = 'ASC')
	{
	$field = empty($field) ? 'uid' : strtolower($field);
	$order = empty($order) ? 'ASC' : strtoupper($order);
	$index = [];

	reset($messages);

	// Create an index
	foreach ($messages as $key => $headers) {
	switch ($field) {
	case 'arrival':
	$field = 'internaldate';
	// no-break
	case 'date':
	case 'internaldate':
	case 'timestamp':
	$value = rcube_utils::strtotime($headers->$field);
	if (!$value && $field != 'timestamp') {
	$value = $headers->timestamp;
	}

	break;

	default:
	// @TODO: decode header value, convert to UTF-8
	$value = $headers->$field;
	if (is_string($value)) {
	$value = str_replace('"', '', $value);

	if ($field == 'subject') {
	$value = rcube_utils::remove_subject_prefix($value);
	}
	}
	}

	$index[$key] = $value;
	}

	$sort_order = $order == 'ASC' ? SORT_ASC : SORT_DESC;
	$sort_flags = SORT_STRING \| SORT_FLAG_CASE;

	if (in_array($field, ['arrival', 'date', 'internaldate', 'timestamp'])) {
	$sort_flags = SORT_NUMERIC;
	}

	array_multisort($index, $sort_order, $sort_flags, $messages);

	return $messages;
	}

	/**
	* Fetch MIME headers of specified message parts
	*
	* @param string $mailbox Mailbox name
	* @param int $uid Message UID
	* @param array $parts Message part identifiers
	* @param bool $mime Use MIME instead of HEADER
	*
	* @return array\|bool Array containing headers string for each specified body
	* False on failure.
	*/
	public function fetchMIMEHeaders($mailbox, $uid, $parts, $mime = true)
	{
	if (!$this->select($mailbox)) {
	return false;
	}

	$parts = (array) $parts;
	$key = $this->nextTag();
	$peeks = [];
	$type = $mime ? 'MIME' : 'HEADER';

	// format request
	foreach ($parts as $part) {
	$peeks[] = "BODY.PEEK[$part.$type]";
	}

	$request = "$key UID FETCH $uid (" . implode(' ', $peeks) . ')';

	// send request
	if (!$this->putLine($request)) {
	$this->setError(self::ERROR_COMMAND, "Failed to send UID FETCH command");
	return false;
	}

	$result = [];

	do {
	$line = $this->readLine(1024);
	if (preg_match('/^\* [0-9]+ FETCH [0-9UID( ]+/', $line, $m)) {
	$line = ltrim(substr($line, strlen($m[0])));
	while (preg_match('/^\s*BODY\[([0-9\.]+)\.'.$type.'\]/', $line, $matches)) {
	$line = substr($line, strlen($matches[0]));
	$result[$matches[1]] = trim($this->multLine($line));
	$line = $this->readLine(1024);
	}
	}
	}
	while (!$this->startsWith($line, $key, true));

	return $result;
	}

	/**
	* Fetches message part header
	*/
	public function fetchPartHeader($mailbox, $id, $is_uid = false, $part = null)
	{
	$part = empty($part) ? 'HEADER' : $part.'.MIME';

	return $this->handlePartBody($mailbox, $id, $is_uid, $part);
	}

	/**
	* Fetches body of the specified message part
	*/
	public function handlePartBody($mailbox, $id, $is_uid = false, $part = '', $encoding = null, $print = null,
	$file = null, $formatted = false, $max_bytes = 0)
	{
	if (!$this->select($mailbox)) {
	return false;
	}

	$binary = true;
	$initiated = false;

	do {
	if (!$initiated) {
	switch ($encoding) {
	case 'base64':
	$mode = 1;
	break;
	case 'quoted-printable':
	$mode = 2;
	break;
	case 'x-uuencode':
	case 'x-uue':
	case 'uue':
	case 'uuencode':
	$mode = 3;
	break;
	default:
	$mode = 0;
	}

	// Use BINARY extension when possible (and safe)
	$binary = $binary && $mode && preg_match('/^[0-9.]+$/', $part) && $this->hasCapability('BINARY');
	$fetch_mode = $binary ? 'BINARY' : 'BODY';
	$partial = $max_bytes ? sprintf('<0.%d>', $max_bytes) : '';

	// format request
	$key = $this->nextTag();
	$cmd = ($is_uid ? 'UID ' : '') . 'FETCH';
	$request = "$key $cmd $id ($fetch_mode.PEEK[$part]$partial)";
	$result = false;
	$found = false;
	$initiated = true;

	// send request
	if (!$this->putLine($request)) {
	$this->setError(self::ERROR_COMMAND, "Failed to send $cmd command");
	return false;
	}

	if ($binary) {
	// WARNING: Use $formatted argument with care, this may break binary data stream
	$mode = -1;
	}
	}

	$line = trim($this->readLine(1024));

	if (!$line) {
	break;
	}

	// handle UNKNOWN-CTE response - RFC 3516, try again with standard BODY request
	if ($binary && !$found && preg_match('/^' . $key . ' NO \[(UNKNOWN-CTE\|PARSE)\]/i', $line)) {
	$binary = $initiated = false;
	continue;
	}

	// skip irrelevant untagged responses (we have a result already)
	if ($found \|\| !preg_match('/^\* ([0-9]+) FETCH (.*)$/', $line, $m)) {
	continue;
	}

	$line = $m[2];

	// handle one line response
	if ($line[0] == '(' && substr($line, -1) == ')') {
	// tokenize content inside brackets
	// the content can be e.g.: (UID 9844 BODY[2.4] NIL)
	$tokens = $this->tokenizeResponse(preg_replace('/(^$\|$$)/', '', $line));

	for ($i=0; $i<count($tokens); $i+=2) {
	if (preg_match('/^(BODY\|BINARY)/i', $tokens[$i])) {
	$result = $tokens[$i+1];
	$found = true;
	break;
	}
	}

	if ($result !== false) {
	if ($mode == 1) {
	$result = base64_decode($result);
	}
	else if ($mode == 2) {
	$result = quoted_printable_decode($result);
	}
	else if ($mode == 3) {
	$result = convert_uudecode($result);
	}
	}
	}
	// response with string literal
	else if (preg_match('/\{([0-9]+)\}$/', $line, $m)) {
	$bytes = (int) $m[1];
	$prev = '';
	$found = true;
	$chunkSize = 1024 * 1024;

	// empty body
	if (!$bytes) {
	$result = '';
	}
	else while ($bytes > 0) {
	$line = $this->readBytes($bytes > $chunkSize ? $chunkSize : $bytes);

	if ($line === '') {
	break;
	}

	$len = strlen($line);

	if ($len > $bytes) {
	$line = substr($line, 0, $bytes);
	$len = strlen($line);
	}
	$bytes -= $len;

	// BASE64
	if ($mode == 1) {
	$line = preg_replace('\|[^a-zA-Z0-9+=/]\|', '', $line);
	// create chunks with proper length for base64 decoding
	$line = $prev.$line;
	$length = strlen($line);
	if ($length % 4) {
	$length = floor($length / 4) * 4;
	$prev = substr($line, $length);
	$line = substr($line, 0, $length);
	}
	else {
	$prev = '';
	}
	$line = base64_decode($line);
	}
	// QUOTED-PRINTABLE
	else if ($mode == 2) {
	$line = rtrim($line, "\t\r\0\x0B");
	$line = quoted_printable_decode($line);
	}
	// UUENCODE
	else if ($mode == 3) {
	$line = rtrim($line, "\t\r\n\0\x0B");
	if ($line == 'end' \|\| preg_match('/^begin\s+[0-7]+\s+.+$/', $line)) {
	continue;
	}
	$line = convert_uudecode($line);
	}
	// default
	else if ($formatted) {
	$line = rtrim($line, "\t\r\n\0\x0B") . "\n";
	}

	if ($file) {
	if (fwrite($file, $line) === false) {
	break;
	}
	}
	else if ($print) {
	echo $line;
	}
	else {
	$result .= $line;
	}
	}
	}
	}
	while (!$this->startsWith($line, $key, true) \|\| !$initiated);

	if ($result !== false) {
	if ($file) {
	return fwrite($file, $result);
	}
	else if ($print) {
	echo $result;
	return true;
	}

	return $result;
	}

	return false;
	}

	/**
	* Handler for IMAP APPEND command
	*
	* @param string $mailbox Mailbox name
	* @param string\|array $message The message source string or array (of strings and file pointers)
	* @param array $flags Message flags
	* @param string $date Message internal date
	* @param bool $binary Enable BINARY append (RFC3516)
	*
	* @return string\|bool On success APPENDUID response (if available) or True, False on failure
	*/
	public function append($mailbox, &$message, $flags = [], $date = null, $binary = false)
	{
	unset($this->data['APPENDUID']);

	if ($mailbox === null \|\| $mailbox === '') {
	return false;
	}

	$binary = $binary && $this->getCapability('BINARY');
	$literal_plus = !$binary && !empty($this->prefs['literal+']);
	$len = 0;
	$msg = is_array($message) ? $message : [&$message];
	$chunk_size = 512000;

	for ($i=0, $cnt=count($msg); $i<$cnt; $i++) {
	if (is_resource($msg[$i])) {
	$stat = fstat($msg[$i]);
	if ($stat === false) {
	return false;
	}
	$len += $stat['size'];
	}
	else {
	if (!$binary) {
	$msg[$i] = str_replace("\r", '', $msg[$i]);
	$msg[$i] = str_replace("\n", "\r\n", $msg[$i]);
	}

	$len += strlen($msg[$i]);
	}
	}

	if (!$len) {
	return false;
	}

	// build APPEND command
	$key = $this->nextTag();
	$request = "$key APPEND " . $this->escape($mailbox) . ' (' . $this->flagsToStr($flags) . ')';
	if (!empty($date)) {
	$request .= ' ' . $this->escape($date);
	}
	$request .= ' ' . ($binary ? '~' : '') . '{' . $len . ($literal_plus ? '+' : '') . '}';

	// send APPEND command
	if (!$this->putLine($request)) {
	$this->setError(self::ERROR_COMMAND, "Failed to send APPEND command");
	return false;
	}

	// Do not wait when LITERAL+ is supported
	if (!$literal_plus) {
	$line = $this->readReply();

	if ($line[0] != '+') {
	$this->parseResult($line, 'APPEND: ');
	return false;
	}
	}

	foreach ($msg as $msg_part) {
	// file pointer
	if (is_resource($msg_part)) {
	rewind($msg_part);
	while (!feof($msg_part) && $this->fp) {
	$buffer = fread($msg_part, $chunk_size);
	$this->putLine($buffer, false);
	}
	fclose($msg_part);
	}
	// string
	else {
	$size = strlen($msg_part);

	// Break up the data by sending one chunk (up to 512k) at a time.
	// This approach reduces our peak memory usage
	for ($offset = 0; $offset < $size; $offset += $chunk_size) {
	$chunk = substr($msg_part, $offset, $chunk_size);
	if (!$this->putLine($chunk, false)) {
	return false;
	}
	}
	}
	}

	if (!$this->putLine('')) { // \r\n
	return false;
	}

	do {
	$line = $this->readLine();
	} while (!$this->startsWith($line, $key, true, true));

	// Clear internal status cache
	unset($this->data['STATUS:'.$mailbox]);

	if ($this->parseResult($line, 'APPEND: ') != self::ERROR_OK) {
	return false;
	}

	if (!empty($this->data['APPENDUID'])) {
	return $this->data['APPENDUID'];
	}

	return true;
	}

	/**
	* Handler for IMAP APPEND command.
	*
	* @param string $mailbox Mailbox name
	* @param string $path Path to the file with message body
	* @param string $headers Message headers
	* @param array $flags Message flags
	* @param string $date Message internal date
	* @param bool $binary Enable BINARY append (RFC3516)
	*
	* @return string\|bool On success APPENDUID response (if available) or True, False on failure
	*/
	public function appendFromFile($mailbox, $path, $headers = null, $flags = [], $date = null, $binary = false)
	{
	// open message file
	if (file_exists(realpath($path))) {
	$fp = fopen($path, 'r');
	}

	if (empty($fp)) {
	$this->setError(self::ERROR_UNKNOWN, "Couldn't open $path for reading");
	return false;
	}

	$message = [];
	if ($headers) {
	$message[] = trim($headers, "\r\n") . "\r\n\r\n";
	}
	$message[] = $fp;

	return $this->append($mailbox, $message, $flags, $date, $binary);
	}

	/**
	* Returns QUOTA information
	*
	* @param string $mailbox Mailbox name
	*
	* @return array\|false Quota information, False on error
	*/
	public function getQuota($mailbox = null)
	{
	if ($mailbox === null \|\| $mailbox === '') {
	$mailbox = 'INBOX';
	}

	// a0001 GETQUOTAROOT INBOX
	// * QUOTAROOT INBOX user/sample
	// * QUOTA user/sample (STORAGE 654 9765)
	// a0001 OK Completed

	list($code, $response) = $this->execute('GETQUOTAROOT', [$this->escape($mailbox)], 0, '/^\* QUOTA /i');

	if ($code != self::ERROR_OK) {
	return false;
	}

	$min_free = PHP_INT_MAX;
	$result = [];
	$all = [];

	foreach (explode("\n", $response) as $line) {
	$tokens = $this->tokenizeResponse($line, 3);
	$quota_root = $tokens[2] ?? null;
	$quotas = $this->tokenizeResponse($line, 1);

	if (empty($quotas)) {
	continue;
	}

	foreach (array_chunk($quotas, 3) as $quota) {
	list($type, $used, $total) = $quota;
	$type = strtolower($type);

	if ($type && $total) {
	$all[$quota_root][$type]['used'] = intval($used);
	$all[$quota_root][$type]['total'] = intval($total);
	}
	}

	if (empty($all[$quota_root]['storage'])) {
	continue;
	}

	$used = $all[$quota_root]['storage']['used'];
	$total = $all[$quota_root]['storage']['total'];
	$free = $total - $used;

	// calculate lowest available space from all storage quotas
	if ($free < $min_free) {
	$min_free = $free;
	$result['used'] = $used;
	$result['total'] = $total;
	$result['percent'] = min(100, round(($used/max(1,$total))*100));
	$result['free'] = 100 - $result['percent'];
	}
	}

	if (!empty($result)) {
	$result['all'] = $all;
	}

	return $result;
	}

	/**
	* Send the SETACL command (RFC4314)
	*
	* @param string $mailbox Mailbox name
	* @param string $user User name
	* @param mixed $acl ACL string or array
	*
	* @return bool True on success, False on failure
	*
	* @since 0.5-beta
	*/
	public function setACL($mailbox, $user, $acl)
	{
	if (is_array($acl)) {
	$acl = implode('', $acl);
	}

	$result = $this->execute('SETACL',
	[$this->escape($mailbox), $this->escape($user), strtolower($acl)],
	self::COMMAND_NORESPONSE
	);

	return $result == self::ERROR_OK;
	}

	/**
	* Send the DELETEACL command (RFC4314)
	*
	* @param string $mailbox Mailbox name
	* @param string $user User name
	*
	* @return bool True on success, False on failure
	*
	* @since 0.5-beta
	*/
	public function deleteACL($mailbox, $user)
	{
	$result = $this->execute('DELETEACL',
	[$this->escape($mailbox), $this->escape($user)],
	self::COMMAND_NORESPONSE
	);

	return $result == self::ERROR_OK;
	}

	/**
	* Send the GETACL command (RFC4314)
	*
	* @param string $mailbox Mailbox name
	*
	* @return array User-rights array on success, NULL on error
	* @since 0.5-beta
	*/
	public function getACL($mailbox)
	{
	list($code, $response) = $this->execute('GETACL', [$this->escape($mailbox)], 0, '/^\* ACL /i');

	if ($code == self::ERROR_OK && $response) {
	// Parse server response (remove "* ACL ")
	$response = substr($response, 6);
	$ret = $this->tokenizeResponse($response);
	$mbox = array_shift($ret);
	$size = count($ret);

	// Create user-rights hash array
	// @TODO: consider implementing fixACL() method according to RFC4314.2.1.1
	// so we could return only standard rights defined in RFC4314,
	// excluding 'c' and 'd' defined in RFC2086.
	if ($size % 2 == 0) {
	for ($i=0; $i<$size; $i++) {
	$ret[$ret[$i]] = str_split($ret[++$i]);
	unset($ret[$i-1]);
	unset($ret[$i]);
	}
	return $ret;
	}

	$this->setError(self::ERROR_COMMAND, "Incomplete ACL response");
	}
	}

	/**
	* Send the LISTRIGHTS command (RFC4314)
	*
	* @param string $mailbox Mailbox name
	* @param string $user User name
	*
	* @return array List of user rights
	* @since 0.5-beta
	*/
	public function listRights($mailbox, $user)
	{
	list($code, $response) = $this->execute('LISTRIGHTS',
	[$this->escape($mailbox), $this->escape($user)], 0, '/^\* LISTRIGHTS /i');

	if ($code == self::ERROR_OK && $response) {
	// Parse server response (remove "* LISTRIGHTS ")
	$response = substr($response, 13);

	$ret_mbox = $this->tokenizeResponse($response, 1);
	$ret_user = $this->tokenizeResponse($response, 1);
	$granted = $this->tokenizeResponse($response, 1);
	$optional = trim($response);

	return [
	'granted' => str_split($granted),
	'optional' => explode(' ', $optional),
	];
	}
	}

	/**
	* Send the MYRIGHTS command (RFC4314)
	*
	* @param string $mailbox Mailbox name
	*
	* @return array MYRIGHTS response on success, NULL on error
	* @since 0.5-beta
	*/
	public function myRights($mailbox)
	{
	list($code, $response) = $this->execute('MYRIGHTS', [$this->escape($mailbox)], 0, '/^\* MYRIGHTS /i');

	if ($code == self::ERROR_OK && $response) {
	// Parse server response (remove "* MYRIGHTS ")
	$response = substr($response, 11);

	$ret_mbox = $this->tokenizeResponse($response, 1);
	$rights = $this->tokenizeResponse($response, 1);

	return str_split($rights);
	}
	}

	/**
	* Send the SETMETADATA command (RFC5464)
	*
	* @param string $mailbox Mailbox name
	* @param array $entries Entry-value array (use NULL value as NIL)
	*
	* @return bool True on success, False on failure
	* @since 0.5-beta
	*/
	public function setMetadata($mailbox, $entries)
	{
	if (!is_array($entries) \|\| empty($entries)) {
	$this->setError(self::ERROR_COMMAND, "Wrong argument for SETMETADATA command");
	return false;
	}

	foreach ($entries as $name => $value) {
	$entries[$name] = $this->escape($name) . ' ' . $this->escape($value, true);
	}

	$entries = implode(' ', $entries);
	$result = $this->execute('SETMETADATA',
	[$this->escape($mailbox), '(' . $entries . ')'],
	self::COMMAND_NORESPONSE
	);

	return $result == self::ERROR_OK;
	}

	/**
	* Send the SETMETADATA command with NIL values (RFC5464)
	*
	* @param string $mailbox Mailbox name
	* @param array $entries Entry names array
	*
	* @return bool True on success, False on failure
	*
	* @since 0.5-beta
	*/
	public function deleteMetadata($mailbox, $entries)
	{
	if (!is_array($entries) && !empty($entries)) {
	$entries = explode(' ', $entries);
	}

	if (empty($entries)) {
	$this->setError(self::ERROR_COMMAND, "Wrong argument for SETMETADATA command");
	return false;
	}

	$data = [];
	foreach ($entries as $entry) {
	$data[$entry] = null;
	}

	return $this->setMetadata($mailbox, $data);
	}

	/**
	* Send the GETMETADATA command (RFC5464)
	*
	* @param string $mailbox Mailbox name
	* @param array $entries Entries
	* @param array $options Command options (with MAXSIZE and DEPTH keys)
	*
	* @return array GETMETADATA result on success, NULL on error
	*
	* @since 0.5-beta
	*/
	public function getMetadata($mailbox, $entries, $options = [])
	{
	if (!is_array($entries)) {
	$entries = [$entries];
	}

	// create entries string
	foreach ($entries as $idx => $name) {
	$entries[$idx] = $this->escape($name);
	}

	$optlist = '';
	$entlist = '(' . implode(' ', $entries) . ')';

	// create options string
	if (is_array($options)) {
	$options = array_change_key_case($options, CASE_UPPER);
	$opts = [];

	if (!empty($options['MAXSIZE'])) {
	$opts[] = 'MAXSIZE '.intval($options['MAXSIZE']);
	}
	if (!empty($options['DEPTH'])) {
	$opts[] = 'DEPTH '.intval($options['DEPTH']);
	}

	if ($opts) {
	$optlist = '(' . implode(' ', $opts) . ')';
	}
	}

	$optlist .= ($optlist ? ' ' : '') . $entlist;

	list($code, $response) = $this->execute('GETMETADATA', [$this->escape($mailbox), $optlist]);

	if ($code == self::ERROR_OK) {
	$result = [];
	$data = $this->tokenizeResponse($response);

	// The METADATA response can contain multiple entries in a single
	// response or multiple responses for each entry or group of entries
	for ($i = 0, $size = count($data); $i < $size; $i++) {
	if ($data[$i] === '*'
	&& $data[++$i] === 'METADATA'
	&& is_string($mbox = $data[++$i])
	&& is_array($data[++$i])
	) {
	for ($x = 0, $size2 = count($data[$i]); $x < $size2; $x += 2) {
	if ($data[$i][$x+1] !== null) {
	$result[$mbox][$data[$i][$x]] = $data[$i][$x+1];
	}
	}
	}
	}

	return $result;
	}
	}

	/**
	* Send the SETANNOTATION command (draft-daboo-imap-annotatemore)
	*
	* @param string $mailbox Mailbox name
	* @param array $data Data array where each item is an array with
	* three elements: entry name, attribute name, value
	*
	* @return bool True on success, False on failure
	* @since 0.5-beta
	*/
	public function setAnnotation($mailbox, $data)
	{
	if (!is_array($data) \|\| empty($data)) {
	$this->setError(self::ERROR_COMMAND, "Wrong argument for SETANNOTATION command");
	return false;
	}

	foreach ($data as $entry) {
	// ANNOTATEMORE drafts before version 08 require quoted parameters
	$entries[] = sprintf('%s (%s %s)', $this->escape($entry[0], true),
	$this->escape($entry[1], true), $this->escape($entry[2], true));
	}

	$entries = implode(' ', $entries);
	$result = $this->execute('SETANNOTATION', [$this->escape($mailbox), $entries], self::COMMAND_NORESPONSE);

	return $result == self::ERROR_OK;
	}

	/**
	* Send the SETANNOTATION command with NIL values (draft-daboo-imap-annotatemore)
	*
	* @param string $mailbox Mailbox name
	* @param array $data Data array where each item is an array with
	* two elements: entry name and attribute name
	*
	* @return bool True on success, False on failure
	*
	* @since 0.5-beta
	*/
	public function deleteAnnotation($mailbox, $data)
	{
	if (!is_array($data) \|\| empty($data)) {
	$this->setError(self::ERROR_COMMAND, "Wrong argument for SETANNOTATION command");
	return false;
	}

	return $this->setAnnotation($mailbox, $data);
	}

	/**
	* Send the GETANNOTATION command (draft-daboo-imap-annotatemore)
	*
	* @param string $mailbox Mailbox name
	* @param array $entries Entries names
	* @param array $attribs Attribs names
	*
	* @return array Annotations result on success, NULL on error
	*
	* @since 0.5-beta
	*/
	public function getAnnotation($mailbox, $entries, $attribs)
	{
	if (!is_array($entries)) {
	$entries = [$entries];
	}

	// create entries string
	// ANNOTATEMORE drafts before version 08 require quoted parameters
	foreach ($entries as $idx => $name) {
	$entries[$idx] = $this->escape($name, true);
	}
	$entries = '(' . implode(' ', $entries) . ')';

	if (!is_array($attribs)) {
	$attribs = [$attribs];
	}

	// create attributes string
	foreach ($attribs as $idx => $name) {
	$attribs[$idx] = $this->escape($name, true);
	}
	$attribs = '(' . implode(' ', $attribs) . ')';

	list($code, $response) = $this->execute('GETANNOTATION', [$this->escape($mailbox), $entries, $attribs]);

	if ($code == self::ERROR_OK) {
	$result = [];
	$data = $this->tokenizeResponse($response);
	$last_entry = null;

	// Here we returns only data compatible with METADATA result format
	if (!empty($data) && ($size = count($data))) {
	for ($i=0; $i<$size; $i++) {
	$entry = $data[$i];
	if (isset($mbox) && is_array($entry)) {
	$attribs = $entry;
	$entry = $last_entry;
	}
	else if ($entry == '*') {
	if ($data[$i+1] == 'ANNOTATION') {
	$mbox = $data[$i+2];
	unset($data[$i]); // "*"
	unset($data[++$i]); // "ANNOTATION"
	unset($data[++$i]); // Mailbox
	}
	// get rid of other untagged responses
	else {
	unset($mbox);
	unset($data[$i]);
	}
	continue;
	}
	else if (isset($mbox)) {
	$attribs = $data[++$i];
	}
	else {
	unset($data[$i]);
	continue;
	}

	if (!empty($attribs)) {
	for ($x=0, $len=count($attribs); $x<$len;) {
	$attr = $attribs[$x++];
	$value = $attribs[$x++];
	if ($attr == 'value.priv' && $value !== null) {
	$result[$mbox]['/private' . $entry] = $value;
	}
	else if ($attr == 'value.shared' && $value !== null) {
	$result[$mbox]['/shared' . $entry] = $value;
	}
	}
	}

	$last_entry = $entry;
	unset($data[$i]);
	}
	}

	return $result;
	}
	}

	/**
	* Returns BODYSTRUCTURE for the specified message.
	*
	* @param string $mailbox Folder name
	* @param int $id Message sequence number or UID
	* @param bool $is_uid True if $id is an UID
	*
	* @return array\|bool Body structure array or False on error.
	* @since 0.6
	*/
	public function getStructure($mailbox, $id, $is_uid = false)
	{
	$result = $this->fetch($mailbox, $id, $is_uid, ['BODYSTRUCTURE']);

	if (is_array($result) && !empty($result)) {
	$result = array_first($result);
	return $result->bodystructure;
	}

	return false;
	}

	/**
	* Returns data of a message part according to specified structure.
	*
	* @param array $structure Message structure (getStructure() result)
	* @param string $part Message part identifier
	*
	* @return array Part data as hash array (type, encoding, charset, size)
	*/
	public static function getStructurePartData($structure, $part)
	{
	$part_a = self::getStructurePartArray($structure, $part);
	$data = [];

	if (empty($part_a)) {
	return $data;
	}

	// content-type
	if (is_array($part_a[0])) {
	$data['type'] = 'multipart';
	}
	else {
	$data['type'] = strtolower($part_a[0]);
	$data['subtype'] = strtolower($part_a[1]);
	$data['encoding'] = strtolower($part_a[5]);

	// charset
	if (is_array($part_a[2])) {
	foreach ($part_a[2] as $key => $val) {
	if (strcasecmp($val, 'charset') == 0) {
	$data['charset'] = $part_a[2][$key+1];
	break;
	}
	}
	}
	}

	// size
	$data['size'] = intval($part_a[6]);

	return $data;
	}

	public static function getStructurePartArray($a, $part)
	{
	if (!is_array($a)) {
	return false;
	}

	if (empty($part)) {
	return $a;
	}

	$ctype = is_string($a[0]) && is_string($a[1]) ? $a[0] . '/' . $a[1] : '';

	if (strcasecmp($ctype, 'message/rfc822') == 0) {
	$a = $a[8];
	}

	if (strpos($part, '.') > 0) {
	$orig_part = $part;
	$pos = strpos($part, '.');
	$rest = substr($orig_part, $pos+1);
	$part = substr($orig_part, 0, $pos);

	return self::getStructurePartArray($a[$part-1], $rest);
	}
	else if ($part > 0) {
	return is_array($a[$part-1]) ? $a[$part-1] : $a;
	}
	}

	/**
	* Creates next command identifier (tag)
	*
	* @return string Command identifier
	* @since 0.5-beta
	*/
	public function nextTag()
	{
	$this->cmd_num++;
	$this->cmd_tag = sprintf('A%04d', $this->cmd_num);

	return $this->cmd_tag;
	}

	/**
	* Sends IMAP command and parses result
	*
	* @param string $command IMAP command
	* @param array $arguments Command arguments
	* @param int $options Execution options
	* @param string $filter Line filter (regexp)
	*
	* @return mixed Response code or list of response code and data
	* @since 0.5-beta
	*/
	public function execute($command, $arguments = [], $options = 0, $filter = null)
	{
	$tag = $this->nextTag();
	$query = $tag . ' ' . $command;
	$noresp = ($options & self::COMMAND_NORESPONSE);
	$response = $noresp ? null : '';

	if (!empty($arguments)) {
	foreach ($arguments as $arg) {
	$query .= ' ' . self::r_implode($arg);
	}
	}

	// Send command
	if (!$this->putLineC($query, true, ($options & self::COMMAND_ANONYMIZED))) {
	preg_match('/^[A-Z0-9]+ ((UID )?[A-Z]+)/', $query, $matches);
	$cmd = $matches[1] ?: 'UNKNOWN';
	$this->setError(self::ERROR_COMMAND, "Failed to send $cmd command");

	return $noresp ? self::ERROR_COMMAND : [self::ERROR_COMMAND, ''];
	}

	// Parse response
	do {
	$line = $this->readFullLine(4096);

	if ($response !== null) {
	if (!$filter \|\| preg_match($filter, $line)) {
	$response .= $line;
	}
	}

	// parse untagged response for [COPYUID 1204196876 3456:3457 123:124] (RFC6851)
	if ($line && $command == 'UID MOVE') {
	if (preg_match("/^\* OK \[COPYUID [0-9]+ ([0-9,:]+) ([0-9,:]+)\]/i", $line, $m)) {
	$this->data['COPYUID'] = [$m[1], $m[2]];
	}
	}
	}
	while (!$this->startsWith($line, $tag . ' ', true, true));

	$code = $this->parseResult($line, $command . ': ');

	// Remove last line from response
	if ($response) {
	if (!$filter) {
	$line_len = min(strlen($response), strlen($line));
	$response = substr($response, 0, -$line_len);
	}

	$response = rtrim($response, "\r\n");
	}

	// optional CAPABILITY response
	if (($options & self::COMMAND_CAPABILITY) && $code == self::ERROR_OK
	&& preg_match('/\[CAPABILITY ([^]]+)\]/i', $line, $matches)
	) {
	$this->parseCapability($matches[1], true);
	}

	// return last line only (without command tag, result and response code)
	if ($line && ($options & self::COMMAND_LASTLINE)) {
	$response = preg_replace("/^$tag (OK\|NO\|BAD\|BYE\|PREAUTH)?\s(\[[a-z-]+\])?\s/i", '', trim($line));
	}

	return $noresp ? $code : [$code, $response];
	}

	/**
	* Splits IMAP response into string tokens
	*
	* @param string &$str The IMAP's server response
	* @param int $num Number of tokens to return
	*
	* @return mixed Tokens array or string if $num=1
	* @since 0.5-beta
	*/
	public static function tokenizeResponse(&$str, $num=0)
	{
	$result = [];

	while (!$num \|\| count($result) < $num) {
	// remove spaces from the beginning of the string
	$str = ltrim($str);

	// empty string
	if ($str === '' \|\| $str === null) {
	break;
	}

	switch ($str[0]) {

	// String literal
	case '{':
	if (($epos = strpos($str, "}\r\n", 1)) == false) {
	// error
	}
	if (!is_numeric(($bytes = substr($str, 1, $epos - 1)))) {
	// error
	}

	$result[] = $bytes ? substr($str, $epos + 3, $bytes) : '';
	$str = substr($str, $epos + 3 + $bytes);
	break;

	// Quoted string
	case '"':
	$len = strlen($str);

	for ($pos=1; $pos<$len; $pos++) {
	if ($str[$pos] == '"') {
	break;
	}
	if ($str[$pos] == "\\") {
	if ($str[$pos + 1] == '"' \|\| $str[$pos + 1] == "\\") {
	$pos++;
	}
	}
	}

	// we need to strip slashes for a quoted string
	$result[] = stripslashes(substr($str, 1, $pos - 1));
	$str = substr($str, $pos + 1);
	break;

	// Parenthesized list
	case '(':
	$str = substr($str, 1);
	$result[] = self::tokenizeResponse($str);
	break;

	case ')':
	$str = substr($str, 1);
	return $result;

	// String atom, number, astring, NIL, *, %
	default:
	// excluded chars: SP, CTL, ), DEL
	// we do not exclude [ and ] (#1489223)
	if (preg_match('/^([^\x00-\x20\x29\x7F]+)/', $str, $m)) {
	$result[] = $m[1] == 'NIL' ? null : $m[1];
	$str = substr($str, strlen($m[1]));
	}

	break;
	}
	}

	return $num == 1 ? ($result[0] ?? '') : $result;
	}

	/**
	* Joins IMAP command line elements (recursively)
	*/
	protected static function r_implode($element)
	{
	if (!is_array($element)) {
	return $element;
	}

	reset($element);

	$string = '';

	foreach ($element as $value) {
	$string .= ' ' . self::r_implode($value);
	}

	return '(' . trim($string) . ')';
	}

	/**
	* Converts message identifiers array into sequence-set syntax
	*
	* @param array $messages Message identifiers
	* @param bool $force Forces compression of any size
	*
	* @return string Compressed sequence-set
	*/
	public static function compressMessageSet($messages, $force = false)
	{
	// given a comma delimited list of independent mid's,
	// compresses by grouping sequences together
	if (!is_array($messages)) {
	// if less than 255 bytes long, let's not bother
	if (!$force && strlen($messages) < 255) {
	return preg_match('/[^0-9:,*]/', $messages) ? 'INVALID' : $messages;
	}

	// see if it's already been compressed
	if (strpos($messages, ':') !== false) {
	return preg_match('/[^0-9:,*]/', $messages) ? 'INVALID' : $messages;
	}

	// separate, then sort
	$messages = explode(',', $messages);
	}

	sort($messages);

	$result = [];
	$start = $prev = $messages[0];

	foreach ($messages as $id) {
	$incr = $id - $prev;
	if ($incr > 1) { // found a gap
	if ($start == $prev) {
	$result[] = $prev; // push single id
	}
	else {
	$result[] = $start . ':' . $prev; // push sequence as start_id:end_id
	}
	$start = $id; // start of new sequence
	}
	$prev = $id;
	}

	// handle the last sequence/id
	if ($start == $prev) {
	$result[] = $prev;
	}
	else {
	$result[] = $start.':'.$prev;
	}

	// return as comma separated string
	$result = implode(',', $result);

	return preg_match('/[^0-9:,*]/', $result) ? 'INVALID' : $result;
	}

	/**
	* Converts message sequence-set into array
	*
	* @param string $messages Message identifiers
	*
	* @return array List of message identifiers
	*/
	public static function uncompressMessageSet($messages)
	{
	if (empty($messages)) {
	return [];
	}

	$result = [];
	$messages = explode(',', $messages);

	foreach ($messages as $idx => $part) {
	$items = explode(':', $part);

	if (!empty($items[1]) && $items[1] > $items[0]) {
	$max = $items[1];
	}
	else {
	$max = $items[0];
	}

	for ($x = $items[0]; $x <= $max; $x++) {
	$result[] = (int) $x;
	}

	unset($messages[$idx]);
	}

	return $result;
	}

	/**
	* Clear internal status cache
	*/
	protected function clear_status_cache($mailbox)
	{
	unset($this->data['STATUS:' . $mailbox]);

	$keys = ['EXISTS', 'RECENT', 'UNSEEN', 'UID-MAP'];

	foreach ($keys as $key) {
	unset($this->data[$key]);
	}
	}

	/**
	* Clear internal cache of the current mailbox
	*/
	protected function clear_mailbox_cache()
	{
	$this->clear_status_cache($this->selected);

	$keys = ['UIDNEXT', 'UIDVALIDITY', 'HIGHESTMODSEQ', 'NOMODSEQ',
	'PERMANENTFLAGS', 'QRESYNC', 'VANISHED', 'READ-WRITE'];

	foreach ($keys as $key) {
	unset($this->data[$key]);
	}
	}

	/**
	* Converts flags array into string for inclusion in IMAP command
	*
	* @param array $flags Flags (see self::flags)
	*
	* @return string Space-separated list of flags
	*/
	protected function flagsToStr($flags)
	{
	foreach ((array) $flags as $idx => $flag) {
	if ($flag = $this->flags[strtoupper($flag)]) {
	$flags[$idx] = $flag;
	}
	}

	return implode(' ', (array) $flags);
	}

	/**
	* CAPABILITY response parser
	*/
	protected function parseCapability($str, $trusted=false)
	{
	$str = preg_replace('/^\* CAPABILITY /i', '', $str);

	$this->capability = explode(' ', strtoupper($str));

	if (!empty($this->prefs['disabled_caps'])) {
	$this->capability = array_diff($this->capability, $this->prefs['disabled_caps']);
	}

	if (!isset($this->prefs['literal+']) && in_array('LITERAL+', $this->capability)) {
	$this->prefs['literal+'] = true;
	}
	else if (!isset($this->prefs['literal-']) && in_array('LITERAL-', $this->capability)) {
	$this->prefs['literal-'] = true;
	}

	if ($trusted) {
	$this->capability_read = true;
	}
	}

	/**
	* Escapes a string when it contains special characters (RFC3501)
	*
	* @param string $string IMAP string
	* @param bool $force_quotes Forces string quoting (for atoms)
	*
	* @return string String atom, quoted-string or string literal
	* @todo lists
	*/
	public static function escape($string, $force_quotes = false)
	{
	if ($string === null) {
	return 'NIL';
	}

	if ($string === '') {
	return '""';
	}

	// atom-string (only safe characters)
	if (!$force_quotes && !preg_match('/[\x00-\x20\x22\x25\x28-\x2A\x5B-\x5D\x7B\x7D\x80-\xFF]/', $string)) {
	return $string;
	}

	// quoted-string
	if (!preg_match('/[\r\n\x00\x80-\xFF]/', $string)) {
	return '"' . addcslashes($string, '\\"') . '"';
	}

	// literal-string
	return sprintf("{%d}\r\n%s", strlen($string), $string);
	}

	/**
	* Set the value of the debugging flag.
	*
	* @param bool $debug New value for the debugging flag.
	* @param callback $handler Logging handler function
	*
	* @since 0.5-stable
	*/
	public function setDebug($debug, $handler = null)
	{
	$this->debug = $debug;
	$this->debug_handler = $handler;
	}

	/**
	* Write the given debug text to the current debug output handler.
	*
	* @param string $message Debug message text.
	*
	* @since 0.5-stable
	*/
	protected function debug($message)
	{
	if (($len = strlen($message)) > self::DEBUG_LINE_LENGTH) {
	$diff = $len - self::DEBUG_LINE_LENGTH;
	$message = substr($message, 0, self::DEBUG_LINE_LENGTH)
	. "... [truncated $diff bytes]";
	}

	if ($this->resourceid) {
	$message = sprintf('[%s] %s', $this->resourceid, $message);
	}

	if ($this->debug_handler) {
	call_user_func_array($this->debug_handler, [$this, $message]);
	}
	else {
	echo "DEBUG: $message\n";
	}
	}
	}

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