--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/program/lib/Roundcube/rcube_imap_generic.php	Thu Jan 04 15:52:31 2018 -0500
@@ -0,0 +1,4099 @@
+<?php
+
+/**
+ +-----------------------------------------------------------------------+
+ | This file is part of the Roundcube Webmail client                     |
+ | Copyright (C) 2005-2015, The Roundcube Dev Team                       |
+ | Copyright (C) 2011-2012, 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 = array();
+    public $flags = array(
+        'SEEN'     => '\\Seen',
+        'DELETED'  => '\\Deleted',
+        'ANSWERED' => '\\Answered',
+        'DRAFT'    => '\\Draft',
+        'FLAGGED'  => '\\Flagged',
+        'FORWARDED' => '$Forwarded',
+        'MDNSENT'  => '$MDNSent',
+        '*'        => '\\*',
+    );
+
+    protected $fp;
+    protected $host;
+    protected $cmd_tag;
+    protected $cmd_num = 0;
+    protected $resourceid;
+    protected $prefs             = array();
+    protected $logged            = false;
+    protected $capability        = array();
+    protected $capability_readed = 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) 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; $i++) {
+                if (preg_match('/^\{([0-9]+)\}\r\n$/', $parts[$i+1], $matches)) {
+                    // LITERAL+ support
+                    if ($this->prefs['literal+']) {
+                        $parts[$i+1] = sprintf("{%d+}\r\n", $matches[1]);
+                    }
+
+                    $bytes = $this->putLine($parts[$i].$parts[$i+1], false, $anonymized);
+                    if ($bytes === false) {
+                        return false;
+                    }
+
+                    $res += $bytes;
+
+                    // don't wait if server supports LITERAL+ capability
+                    if (!$this->prefs['literal+']) {
+                        $line = $this->readLine(1000);
+                        // handle error in command
+                        if ($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 ?: null;
+            }
+
+            $buffer = fgets($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 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 === null) {
+                    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)
+    {
+        do {
+            $line = trim($this->readLine(1024));
+            // store untagged response lines
+            if ($line[0] == '*') {
+                $untagged[] = $line;
+            }
+        }
+        while ($line[0] == '*');
+
+        if ($untagged) {
+            $untagged = join("\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)) {
+                        $this->data['COPYUID'] = array($m[1], $m[2]);
+                    }
+                }
+
+                $this->result = $str;
+
+                if ($this->errornum != self::ERROR_OK) {
+                    $this->error = $err_prefix ? $err_prefix.$str : $str;
+                }
+            }
+
+            return $this->errornum;
+        }
+
+        return self::ERROR_UNKNOWN;
+    }
+
+    /**
+     * Checks connection stream state.
+     *
+     * @return bool True if connection is closed
+     */
+    protected function eof()
+    {
+        if (!is_resource($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']))
+        ) {
+            $this->closeSocket();
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Closes connection stream.
+     */
+    protected function closeSocket()
+    {
+        @fclose($this->fp);
+        $this->fp = null;
+    }
+
+    /**
+     * Error code/message setter.
+     */
+    protected function setError($code, $msg = '')
+    {
+        $this->errornum = $code;
+        $this->error    = $msg;
+    }
+
+    /**
+     * 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) || $name == '') {
+            return false;
+        }
+
+        if (in_array($name, $this->capability)) {
+            return true;
+        }
+        else if (strpos($name, '=')) {
+            return false;
+        }
+
+        $result = array();
+        foreach ($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_readed) {
+            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_readed = true;
+
+        return $this->hasCapability($name);
+    }
+
+    /**
+     * Clears detected server capabilities
+     */
+    public function clearCapability()
+    {
+        $this->capability        = array();
+        $this->capability_readed = false;
+    }
+
+    /**
+     * DIGEST-MD5/CRAM-MD5/PLAIN Authentication
+     *
+     * @param string $user Username
+     * @param string $pass Password
+     * @param string $type Authentication type (PLAIN/CRAM-MD5/DIGEST-MD5)
+     *
+     * @return resource Connection resourse on success, error code on error
+     */
+    protected function authenticate($user, $pass, $type = 'PLAIN')
+    {
+        if ($type == 'CRAM-MD5' || $type == 'DIGEST-MD5') {
+            if ($type == 'DIGEST-MD5' && !class_exists('Auth_SASL')) {
+                $this->setError(self::ERROR_BYE,
+                    "The Auth_SASL package is required for DIGEST-MD5 authentication");
+                return self::ERROR_BAD;
+            }
+
+            $this->putLine($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) {
+                    $this->setError(self::ERROR_BAD,
+                        "Unexpected response from server to DIGEST-MD5 response");
+                    return self::ERROR_BAD;
+                }
+
+                $this->putLine('');
+            }
+
+            $line   = $this->readReply();
+            $result = $this->parseResult($line);
+        }
+        else if ($type == 'GSSAPI') {
+            if (!extension_loaded('krb5')) {
+                $this->setError(self::ERROR_BYE,
+                    "The krb5 extension is required for GSSAPI authentication");
+                return self::ERROR_BAD;
+            }
+
+            if (empty($this->prefs['gssapi_cn'])) {
+                $this->setError(self::ERROR_BYE,
+                    "The gssapi_cn parameter is required for GSSAPI authentication");
+                return self::ERROR_BAD;
+            }
+
+            if (empty($this->prefs['gssapi_context'])) {
+                $this->setError(self::ERROR_BYE,
+                    "The gssapi_context parameter is required for GSSAPI authentication");
+                return self::ERROR_BAD;
+            }
+
+            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);
+                $this->setError(self::ERROR_BYE, "GSSAPI authentication failed");
+                return self::ERROR_BAD;
+            }
+
+            $this->putLine($this->nextTag() . " AUTHENTICATE GSSAPI " . $token);
+            $line = trim($this->readReply());
+
+            if ($line[0] != '+') {
+                return $this->parseResult($line);
+            }
+
+            try {
+                $challenge = base64_decode(substr($line, 2));
+                $gssapicontext->unwrap($challenge, $challenge);
+                $gssapicontext->wrap($challenge, $challenge, true);
+            }
+            catch (Exception $e) {
+                trigger_error($e->getMessage(), E_USER_WARNING);
+                $this->setError(self::ERROR_BYE, "GSSAPI authentication failed");
+                return self::ERROR_BAD;
+            }
+
+            $this->putLine(base64_encode($challenge));
+
+            $line   = $this->readReply();
+            $result = $this->parseResult($line);
+        }
+        else { // 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) = $this->execute("AUTHENTICATE PLAIN", array($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);
+            }
+        }
+
+        if ($result == self::ERROR_OK) {
+            // optional CAPABILITY response
+            if ($line && preg_match('/\[CAPABILITY ([^]]+)\]/i', $line, $matches)) {
+                $this->parseCapability($matches[1], true);
+            }
+            return $this->fp;
+        }
+        else {
+            $this->setError($result, "AUTHENTICATE $type: $line");
+        }
+
+        return $result;
+    }
+
+    /**
+     * LOGIN Authentication
+     *
+     * @param string $user Username
+     * @param string $pass Password
+     *
+     * @return resource Connection resourse on success, error code on error
+     */
+    protected function login($user, $password)
+    {
+        list($code, $response) = $this->execute('LOGIN', array(
+            $this->escape($user), $this->escape($password)), 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 $code;
+    }
+
+    /**
+     * Detects hierarchy delimiter
+     *
+     * @return string The delimiter
+     */
+    public function getHierarchyDelimiter()
+    {
+        if ($this->prefs['delimiter']) {
+            return $this->prefs['delimiter'];
+        }
+
+        // try (LIST "" ""), should return delimiter (RFC2060 Sec 6.3.8)
+        list($code, $response) = $this->execute('LIST',
+            array($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 (!is_array($data)) {
+            return $code;
+        }
+
+        $this->prefs['namespace'] = array(
+            '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 = array())
+    {
+        // 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($host)) {
+            return false;
+        }
+
+        // Send ID info
+        if (!empty($this->prefs['ident']) && $this->getCapability('ID')) {
+            $this->data['ID'] = $this->id($this->prefs['ident']);
+        }
+
+        $auth_method  = $this->prefs['auth_type'];
+        $auth_methods = array();
+        $result       = null;
+
+        // check for supported auth methods
+        if ($auth_method == 'CHECK') {
+            if ($auth_caps = $this->getCapability('AUTH')) {
+                $auth_methods = $auth_caps;
+            }
+
+            // RFC 2595 (LOGINDISABLED) LOGIN disabled when connection is not secure
+            $login_disabled = $this->getCapability('LOGINDISABLED');
+            if (($key = array_search('LOGIN', $auth_methods)) !== false) {
+                if ($login_disabled) {
+                    unset($auth_methods[$key]);
+                }
+            }
+            else if (!$login_disabled) {
+                $auth_methods[] = 'LOGIN';
+            }
+
+            // Use best (for security) supported authentication method
+            $all_methods = array('DIGEST-MD5', 'CRAM-MD5', 'CRAM_MD5', 'PLAIN', 'LOGIN');
+
+            if (!empty($this->prefs['gssapi_cn'])) {
+                array_unshift($all_methods, 'GSSAPI');
+            }
+
+            foreach ($all_methods as $auth_method) {
+                if (in_array($auth_method, $auth_methods)) {
+                    break;
+                }
+            }
+        }
+        else {
+            // Prevent from sending credentials in plain text when connection is not secure
+            if ($auth_method == 'LOGIN' && $this->getCapability('LOGINDISABLED')) {
+                $this->setError(self::ERROR_BAD, "Login disabled by IMAP server");
+                $this->closeConnection();
+                return false;
+            }
+            // replace AUTH with CRAM-MD5 for backward compat.
+            if ($auth_method == 'AUTH') {
+                $auth_method = 'CRAM-MD5';
+            }
+        }
+
+        // pre-login capabilities can be not complete
+        $this->capability_readed = false;
+
+        // Authenticate
+        switch ($auth_method) {
+            case 'CRAM_MD5':
+                $auth_method = 'CRAM-MD5';
+            case 'CRAM-MD5':
+            case 'DIGEST-MD5':
+            case 'PLAIN':
+            case 'GSSAPI':
+                $result = $this->authenticate($user, $password, $auth_method);
+                break;
+            case 'LOGIN':
+                $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 ($this->prefs['force_caps']) {
+                $this->clearCapability();
+            }
+            $this->logged = true;
+
+            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    = '';
+        $this->errornum = self::ERROR_OK;
+
+        if (!$this->prefs['port']) {
+            $this->prefs['port'] = 143;
+        }
+
+        // check for SSL
+        if ($this->prefs['ssl_mode'] && $this->prefs['ssl_mode'] != 'tls') {
+            $host = $this->prefs['ssl_mode'] . '://' . $host;
+        }
+
+        if ($this->prefs['timeout'] <= 0) {
+            $this->prefs['timeout'] = max(0, intval(ini_get('default_socket_timeout')));
+        }
+
+        if (!empty($this->prefs['socket_options'])) {
+            $context  = stream_context_create($this->prefs['socket_options']);
+            $this->fp = stream_socket_client($host . ':' . $this->prefs['port'], $errno, $errstr,
+                $this->prefs['timeout'], STREAM_CLIENT_CONNECT, $context);
+        }
+        else {
+            $this->fp = @fsockopen($host, $this->prefs['port'], $errno, $errstr, $this->prefs['timeout']);
+        }
+
+        if (!$this->fp) {
+            $this->setError(self::ERROR_BAD, sprintf("Could not connect to %s:%d: %s",
+                $host, $this->prefs['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) {
+            // set connection identifier for debug output
+            preg_match('/#([0-9]+)/', (string) $this->fp, $m);
+            $this->resourceid = strtoupper(substr(md5($m[1].$this->user.microtime()), 0, 4));
+
+            if ($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, $this->prefs['port'], $line);
+            else
+                $error = sprintf("Empty startup greeting (%s:%d)", $host, $this->prefs['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 ($this->prefs['ssl_mode'] == 'tls' && $this->getCapability('STARTTLS')) {
+            $res = $this->execute('STARTTLS');
+
+            if ($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  $qresync_data QRESYNC data (RFC5162)
+     *
+     * @return boolean True on success, false on error
+     */
+    public function select($mailbox, $qresync_data = null)
+    {
+        if (!strlen($mailbox)) {
+            return false;
+        }
+
+        if ($this->selected === $mailbox) {
+            return true;
+        }
+/*
+    Temporary commented out because Courier returns \Noselect for INBOX
+    Requires more investigation
+
+        if (is_array($this->data['LIST']) && is_array($opts = $this->data['LIST'][$mailbox])) {
+            if (in_array('\\Noselect', $opts)) {
+                return false;
+            }
+        }
+*/
+        $params = array($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[] = array('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       = array('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, $items = array())
+    {
+        if (!strlen($mailbox)) {
+            return false;
+        }
+
+        if (!in_array('MESSAGES', $items)) {
+            $items[] = 'MESSAGES';
+        }
+        if (!in_array('UNSEEN', $items)) {
+            $items[] = 'UNSEEN';
+        }
+
+        list($code, $response) = $this->execute('STATUS', array($this->escape($mailbox),
+            '(' . implode(' ', $items) . ')'));
+
+        if ($code == self::ERROR_OK && preg_match('/^\* STATUS /i', $response)) {
+            $result   = array();
+            $response = substr($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 $messages Message UIDs to expunge
+     *
+     * @return boolean True on success, False on error
+     */
+    public function expunge($mailbox, $messages = null)
+    {
+        if (!$this->select($mailbox)) {
+            return false;
+        }
+
+        if (!$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   = $this->execute('UID EXPUNGE', array($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 boolean 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 $mailbox Mailbox name
+     *
+     * @return boolean True on success, False on error
+     */
+    public function subscribe($mailbox)
+    {
+        $result = $this->execute('SUBSCRIBE', array($this->escape($mailbox)),
+            self::COMMAND_NORESPONSE);
+
+        return $result == self::ERROR_OK;
+    }
+
+    /**
+     * Folder unsubscription (UNSUBSCRIBE)
+     *
+     * @param string $mailbox Mailbox name
+     *
+     * @return boolean True on success, False on error
+     */
+    public function unsubscribe($mailbox)
+    {
+        $result = $this->execute('UNSUBSCRIBE', array($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)
+    {
+        $args = array($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 = $this->execute('RENAME', array($this->escape($from), $this->escape($to)),
+            self::COMMAND_NORESPONSE);
+
+        return $result == self::ERROR_OK;
+    }
+
+    /**
+     * Executes DELETE command
+     *
+     * @param string $mailbox Mailbox name
+     *
+     * @return boolean True on success, False on error
+     */
+    public function deleteFolder($mailbox)
+    {
+        $result = $this->execute('DELETE', array($this->escape($mailbox)),
+            self::COMMAND_NORESPONSE);
+
+        return $result == self::ERROR_OK;
+    }
+
+    /**
+     * Removes all messages in a folder
+     *
+     * @param string $mailbox Mailbox name
+     *
+     * @return boolean True on success, False on error
+     */
+    public function clearFolder($mailbox)
+    {
+        if ($this->countMessages($mailbox) > 0) {
+            $res = $this->flag($mailbox, '1:*', 'DELETED');
+        }
+
+        if ($res) {
+            if ($this->selected === $mailbox) {
+                $res = $this->close();
+            }
+            else {
+                $res = $this->expunge($mailbox);
+            }
+        }
+
+        return $res;
+    }
+
+    /**
+     * Returns list of mailboxes
+     *
+     * @param string $ref         Reference name
+     * @param string $mailbox     Mailbox name
+     * @param array  $return_opts (see self::_listMailboxes)
+     * @param array  $select_opts (see self::_listMailboxes)
+     *
+     * @return array|bool List of mailboxes or hash of options if STATUS/MYROGHTS response
+     *                    is requested, False on error.
+     */
+    public function listMailboxes($ref, $mailbox, $return_opts = array(), $select_opts = array())
+    {
+        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  $return_opts (see self::_listMailboxes)
+     *
+     * @return array|bool List of mailboxes or hash of options if STATUS/MYROGHTS response
+     *                    is requested, False on error.
+     */
+    public function listSubscribed($ref, $mailbox, $return_opts = array())
+    {
+        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  $select_opts List of selection options (RFC5258: LIST-EXTENDED)
+     *                            Possible: SUBSCRIBED, RECURSIVEMATCH, REMOTE,
+     *                                      SPECIAL-USE (RFC6154)
+     *
+     * @return array|bool List of mailboxes or hash of options if STATUS/MYROGHTS response
+     *                    is requested, False on error.
+     */
+    protected function _listMailboxes($ref, $mailbox, $subscribed=false,
+        $return_opts=array(), $select_opts=array())
+    {
+        if (!strlen($mailbox)) {
+            $mailbox = '*';
+        }
+
+        $args = array();
+        $rets = array();
+
+        if (!empty($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    = array('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 = array('MESSAGES', 'RECENT', 'UIDNEXT', 'UIDVALIDITY', 'UNSEEN');
+            $opts        = array_diff($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  = array();
+            $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] = array();
+                    }
+
+                    // 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
+        $cache = $this->data['STATUS:'.$mailbox];
+        if (!empty($cache) && isset($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, array('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
+        $cache = $this->data['STATUS:'.$mailbox];
+        if (!empty($cache) && isset($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, array('COUNT'));
+        if (!$index->is_error()) {
+            return $index->count();
+        }
+
+        return false;
+    }
+
+    /**
+     * Executes ID command (RFC2971)
+     *
+     * @param array $items Client identification information key/value hash
+     *
+     * @return array Server identification information key/value hash
+     * @since 0.6
+     */
+    public function id($items = array())
+    {
+        if (is_array($items) && !empty($items)) {
+            foreach ($items as $key => $value) {
+                $args[] = $this->escape($key, true);
+                $args[] = $this->escape($value, true);
+            }
+        }
+
+        list($code, $response) = $this->execute('ID', array(
+            !empty($args) ? '(' . implode(' ', (array) $args) . ')' : $this->escape(null)
+        ));
+
+        if ($code == self::ERROR_OK && preg_match('/^\* ID /i', $response)) {
+            $response = substr($response, 5); // remove prefix "* ID "
+            $items    = $this->tokenizeResponse($response, 1);
+            $result   = null;
+
+            for ($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)) {
+            $extension = array($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', $extension);
+
+        if ($code == self::ERROR_OK && preg_match('/^\* ENABLED /i', $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 = array('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 != $mailbox && !$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',
+            array("($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',
+            array($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 = array())
+    {
+        $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 = array('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',
+            array($params));
+
+        if ($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, $return_uid = false)
+    {
+        if (is_array($message_set)) {
+            if (!($message_set = $this->compressMessageSet($message_set))) {
+                return false;
+            }
+        }
+        else {
+            list($from_idx, $to_idx) = explode(':', $message_set);
+            if (empty($message_set) ||
+                (isset($to_idx) && $to_idx != '*' && (int)$from_idx > (int)$to_idx)
+            ) {
+                return false;
+            }
+        }
+
+        $index_field = empty($index_field) ? 'DATE' : strtoupper($index_field);
+
+        $fields_a['DATE']         = 1;
+        $fields_a['INTERNALDATE'] = 4;
+        $fields_a['ARRIVAL']      = 4;
+        $fields_a['FROM']         = 1;
+        $fields_a['REPLY-TO']     = 1;
+        $fields_a['SENDER']       = 1;
+        $fields_a['TO']           = 1;
+        $fields_a['CC']           = 1;
+        $fields_a['SUBJECT']      = 1;
+        $fields_a['UID']          = 2;
+        $fields_a['SIZE']         = 2;
+        $fields_a['SEEN']         = 3;
+        $fields_a['RECENT']       = 3;
+        $fields_a['DELETED']      = 3;
+
+        if (!($mode = $fields_a[$index_field])) {
+            return false;
+        }
+
+        //  Select the mailbox
+        if (!$this->select($mailbox)) {
+            return false;
+        }
+
+        // build FETCH command string
+        $key    = $this->nextTag();
+        $cmd    = $uidfetch ? 'UID FETCH' : 'FETCH';
+        $fields = array();
+
+        if ($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 = array();
+
+        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(array('/^"*[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)) {
+                        $value = preg_replace(array('/^"*[a-z]+:/i', '/\s+$/sm'), array('', ''), $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($mailbox)) {
+            return null;
+        }
+
+        if ($uid = $this->data['UID-MAP'][$id]) {
+            return $uid;
+        }
+
+        if (isset($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 (!$this->data['READ-WRITE']) {
+            $this->setError(self::ERROR_READONLY, "Mailbox is read-only");
+            return false;
+        }
+
+        if ($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', array(
+            $this->compressMessageSet($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', array(
+            $this->compressMessageSet($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($from)) {
+            return false;
+        }
+
+        if (!$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', array(
+                $this->compressMessageSet($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 = array(),
+        $mod_seq = null, $vanished = false)
+    {
+        if (!$this->select($mailbox)) {
+            return false;
+        }
+
+        $message_set = $this->compressMessageSet($message_set);
+        $result      = array();
+
+        $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 = $this->readLine(4096);
+
+            if (!$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;
+                $lines   = array();
+                $line    = substr($line, strlen($m[0]) + 2);
+                $ln      = 0;
+
+                // get complete entry
+                while (preg_match('/\{([0-9]+)\}\r\n$/', $line, $m)) {
+                    $bytes = $m[1];
+                    $out   = '';
+
+                    while (strlen($out) < $bytes) {
+                        $out = $this->readBytes($bytes);
+                        if ($out === null) {
+                            break;
+                        }
+                        $line .= $out;
+                    }
+
+                    $str = $this->readLine(4096);
+                    if ($str === false) {
+                        break;
+                    }
+
+                    $line .= $str;
+                }
+
+                // Tokenize response and assign to object properties
+                while (list($name, $value) = $this->tokenizeResponse($line, 2)) {
+                    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) {
+                                $flag = str_replace(array('$', "\\"), '', $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')) {
+                            $value = array($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));
+                    foreach ($headers as $resln) {
+                        if (ord($resln[0]) <= 32) {
+                            $lines[$ln] .= (empty($lines[$ln]) ? '' : "\n") . trim($resln);
+                        }
+                        else {
+                            $lines[++$ln] = trim($resln);
+                        }
+                    }
+
+                    foreach ($lines as $str) {
+                        list($field, $string) = explode(':', $str, 2);
+
+                        $field  = strtolower($field);
+                        $string = preg_replace('/\n[\t\s]*/', ' ', trim($string));
+
+                        switch ($field) {
+                        case 'date';
+                            $result[$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':
+                        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 = $string;
+                        break;
+                        case 'content-type':
+                            $ctype_parts = preg_split('/[; ]+/', $string);
+                            $result[$id]->ctype = strtolower(array_shift($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(array("\n", '<', '>'), '', $string);
+                            break;
+                        case 'return-receipt-to':
+                        case 'disposition-notification-to':
+                        case 'x-confirm-reading-to':
+                            $result[$id]->mdn_to = $string;
+                            break;
+                        case 'message-id':
+                            $result[$id]->messageID = $string;
+                            break;
+                        case 'x-priority':
+                            if (preg_match('/^(\d+)/', $string, $matches)) {
+                                $result[$id]->priority = intval($matches[1]);
+                            }
+                            break;
+                        default:
+                            if (strlen($field) < 3) {
+                                break;
+                            }
+                            if ($result[$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 = array())
+    {
+        $query_items = array('UID', 'RFC822.SIZE', 'FLAGS', 'INTERNALDATE');
+        $headers     = array('DATE', 'FROM', 'TO', 'SUBJECT', 'CONTENT-TYPE', 'CC', 'REPLY-TO',
+            'LIST-POST', 'DISPOSITION-NOTIFICATION-TO', 'X-PRIORITY');
+
+        if (!empty($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 = array())
+    {
+        $a = $this->fetchHeaders($mailbox, $id, $is_uid, $bodystr, $add_headers);
+        if (is_array($a)) {
+            return array_shift($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 $flag     Sorting order (ASC|DESC)
+     *
+     * @return array Sorted input array
+     */
+    public static function sortHeaders($messages, $field, $flag)
+    {
+        // Strategy: First, we'll create an "index" array.
+        // Then, we'll use sort() on that array, and use that to sort the main array.
+
+        $field  = empty($field) ? 'uid' : strtolower($field);
+        $flag   = empty($flag) ? 'ASC' : strtoupper($flag);
+        $index  = array();
+        $result = array();
+
+        reset($messages);
+
+        foreach ($messages as $key => $headers) {
+            $value = null;
+
+            switch ($field) {
+            case 'arrival':
+                $field = 'internaldate';
+            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 = preg_replace('/^(Re:\s*|Fwd:\s*|Fw:\s*)+/i', '', $value);
+                    }
+
+                    $data = strtoupper($value);
+                }
+            }
+
+            $index[$key] = $value;
+        }
+
+        if (!empty($index)) {
+            // sort index
+            if ($flag == 'ASC') {
+                asort($index);
+            }
+            else {
+                arsort($index);
+            }
+
+            // form new array based on index
+            foreach ($index as $key => $val) {
+                $result[$key] = $messages[$key];
+            }
+        }
+
+        return $result;
+    }
+
+    /**
+     * 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   $mime    Use MIME instad of HEADER
+     *
+     * @return array|bool Array containing headers string for each specified body
+     *                    False on failure.
+     */
+    public function fetchMIMEHeaders($mailbox, $uid, $parts, $mime = true)
+    {
+        if (!$this->select($mailbox)) {
+            return false;
+        }
+
+        $result = false;
+        $parts  = (array) $parts;
+        $key    = $this->nextTag();
+        $peeks  = array();
+        $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;
+        }
+
+        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('/^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;
+        }
+
+        $binary = true;
+
+        do {
+            if (!$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 \[UNKNOWN-CTE\]/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  = '';
+                $found = true;
+
+                // empty body
+                if (!$bytes) {
+                    $result = '';
+                }
+                else while ($bytes > 0) {
+                    $line = $this->readLine(8192);
+
+                    if ($line === null) {
+                        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 = array(), $date = null, $binary = false)
+    {
+        unset($this->data['APPENDUID']);
+
+        if ($mailbox === null || $mailbox === '') {
+            return false;
+        }
+
+        $binary       = $binary && $this->getCapability('BINARY');
+        $literal_plus = !$binary && $this->prefs['literal+'];
+        $len          = 0;
+        $msg          = is_array($message) ? $message : array(&$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 = array(), $date = null, $binary = false)
+    {
+        // open message file
+        if (file_exists(realpath($path))) {
+            $fp = fopen($path, 'r');
+        }
+
+        if (!$fp) {
+            $this->setError(self::ERROR_UNKNOWN, "Couldn't open $path for reading");
+            return false;
+        }
+
+        $message = array();
+        if ($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 $mailbox Mailbox name
+     *
+     * @return array Quota information
+     */
+    public function getQuota($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) = $this->execute('GETQUOTAROOT', array($this->escape($mailbox)));
+
+        $result   = false;
+        $min_free = PHP_INT_MAX;
+        $all      = array();
+
+        if ($code == self::ERROR_OK) {
+            foreach (explode("\n", $response) as $line) {
+                if (preg_match('/^\* QUOTA /', $line)) {
+                    list(, , $quota_root) = $this->tokenizeResponse($line, 3);
+
+                    while ($line) {
+                        list($type, $used, $total) = $this->tokenizeResponse($line, 1);
+                        $type = strtolower($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  $acl     ACL string or array
+     *
+     * @return boolean True on success, False on failure
+     *
+     * @since 0.5-beta
+     */
+    public function setACL($mailbox, $user, $acl)
+    {
+        if (is_array($acl)) {
+            $acl = implode('', $acl);
+        }
+
+        $result = $this->execute('SETACL', array(
+            $this->escape($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 $user    User name
+     *
+     * @return boolean True on success, False on failure
+     *
+     * @since 0.5-beta
+     */
+    public function deleteACL($mailbox, $user)
+    {
+        $result = $this->execute('DELETEACL', array(
+            $this->escape($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) = $this->execute('GETACL', array($this->escape($mailbox)));
+
+        if ($code == self::ERROR_OK && preg_match('/^\* ACL /i', $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', array(
+            $this->escape($mailbox), $this->escape($user)));
+
+        if ($code == self::ERROR_OK && preg_match('/^\* LISTRIGHTS /i', $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 array(
+                '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) = $this->execute('MYRIGHTS', array($this->escape($mailbox)));
+
+        if ($code == self::ERROR_OK && preg_match('/^\* MYRIGHTS /i', $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  $entries Entry-value array (use NULL value as NIL)
+     *
+     * @return boolean True on success, False on failure
+     * @since 0.5-beta
+     */
+    public function setMetadata($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', array(
+            $this->escape($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  $entries Entry names array
+     *
+     * @return boolean True on success, False on failure
+     *
+     * @since 0.5-beta
+     */
+    public function deleteMetadata($mailbox, $entries)
+    {
+        if (!is_array($entries) && !empty($entries)) {
+            $entries = explode(' ', $entries);
+        }
+
+        if (empty($entries)) {
+            $this->setError(self::ERROR_COMMAND, "Wrong argument for SETMETADATA command");
+            return false;
+        }
+
+        foreach ($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, $options=array())
+    {
+        if (!is_array($entries)) {
+            $entries = array($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);
+            $opts = array();
+
+            if (!empty($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', array(
+            $this->escape($mailbox), $optlist));
+
+        if ($code == self::ERROR_OK) {
+            $result = array();
+            $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
+            if (!empty($data) && ($size = count($data))) {
+                for ($i=0; $i<$size; $i++) {
+                    if (isset($mbox) && is_array($data[$i])) {
+                        $size_sub = count($data[$i]);
+                        for ($x=0; $x<$size_sub; $x+=2) {
+                            if ($data[$i][$x+1] !== null)
+                                $result[$mbox][$data[$i][$x]] = $data[$i][$x+1];
+                        }
+                        unset($data[$i]);
+                    }
+                    else if ($data[$i] == '*') {
+                        if ($data[$i+1] == 'METADATA') {
+                            $mbox = $data[$i+2];
+                            unset($data[$i]);   // "*"
+                            unset($data[++$i]); // "METADATA"
+                            unset($data[++$i]); // Mailbox
+                        }
+                        // get rid of other untagged responses
+                        else {
+                            unset($mbox);
+                            unset($data[$i]);
+                        }
+                    }
+                    else if (isset($mbox)) {
+                        if ($data[++$i] !== null)
+                            $result[$mbox][$data[$i-1]] = $data[$i];
+                        unset($data[$i]);
+                        unset($data[$i-1]);
+                    }
+                    else {
+                        unset($data[$i]);
+                    }
+                }
+            }
+
+            return $result;
+        }
+    }
+
+    /**
+     * Send the SETANNOTATION command (draft-daboo-imap-annotatemore)
+     *
+     * @param string $mailbox Mailbox name
+     * @param array  $data    Data array where each item is an array with
+     *                        three elements: entry name, attribute name, value
+     *
+     * @return boolean True on success, False on failure
+     * @since 0.5-beta
+     */
+    public function setAnnotation($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', array(
+            $this->escape($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  $data    Data array where each item is an array with
+     *                        two elements: entry name and attribute name
+     *
+     * @return boolean True on success, False on failure
+     *
+     * @since 0.5-beta
+     */
+    public function deleteAnnotation($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)) {
+            $entries = array($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)) {
+            $attribs = array($attribs);
+        }
+
+        // create attributes string
+        foreach ($attribs as $idx => $name) {
+            $attribs[$idx] = $this->escape($name, true);
+        }
+        $attribs = '(' . implode(' ', $attribs) . ')';
+
+        list($code, $response) = $this->execute('GETANNOTATION', array(
+            $this->escape($mailbox), $entries, $attribs));
+
+        if ($code == self::ERROR_OK) {
+            $result = array();
+            $data   = $this->tokenizeResponse($response);
+
+            // 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, $is_uid, array('BODYSTRUCTURE'));
+
+        if (is_array($result)) {
+            $result = array_shift($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);
+        $data   = array();
+
+        if (empty($part_a)) {
+            return $data;
+        }
+
+        // content-type
+        if (is_array($part_a[0])) {
+            $data['type'] = 'multipart';
+        }
+        else {
+            $data['type']     = strtolower($part_a[0]);
+            $data['encoding'] = strtolower($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    $options   Execution options
+     *
+     * @return mixed Response code or list of response code and data
+     * @since 0.5-beta
+     */
+    public function execute($command, $arguments=array(), $options=0)
+    {
+        $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 : array(self::ERROR_COMMAND, '');
+        }
+
+        // Parse response
+        do {
+            $line = $this->readLine(4096);
+
+            if ($response !== null) {
+                $response .= $line;
+            }
+
+            // parse untagged response for [COPYUID 1204196876 3456:3457 123:124] (RFC6851)
+            if ($line && $command == 'UID MOVE' && substr_compare($line, '* OK', 0, 4, true)) {
+                if (preg_match("/^\* OK \[COPYUID [0-9]+ ([0-9,:]+) ([0-9,:]+)\]/i", $line, $m)) {
+                    $this->data['COPYUID'] = array($m[1], $m[2]);
+                }
+            }
+        }
+        while (!$this->startsWith($line, $tag . ' ', true, true));
+
+        $code = $this->parseResult($line, $command . ': ');
+
+        // Remove last line from response
+        if ($response) {
+            $line_len = min(strlen($response), strlen($line) + 2);
+            $response = substr($response, 0, -$line_len);
+        }
+
+        // optional CAPABILITY response
+        if (($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 ? $code : array($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)
+    {
+        $result = array();
+
+        while (!$num || count($result) < $num) {
+            // remove spaces from the beginning of the string
+            $str = ltrim($str);
+
+            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 $result;
+
+            // String atom, number, astring, NIL, *, %
+            default:
+                // empty string
+                if ($str === '' || $str === null) {
+                    break 2;
+                }
+
+                // 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)
+    {
+        $string = '';
+
+        if (is_array($element)) {
+            reset($element);
+            foreach ($element as $value) {
+                $string .= ' ' . self::r_implode($value);
+            }
+        }
+        else {
+            return $element;
+        }
+
+        return '(' . trim($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 $messages;
+            }
+
+            // see if it's already been compressed
+            if (strpos($messages, ':') !== false) {
+                return $messages;
+            }
+
+            // separate, then sort
+            $messages = explode(',', $messages);
+        }
+
+        sort($messages);
+
+        $result = array();
+        $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
+        return implode(',', $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 array();
+        }
+
+        $result   = array();
+        $messages = explode(',', $messages);
+
+        foreach ($messages as $idx => $part) {
+            $items = explode(':', $part);
+            $max   = max($items[0], $items[1]);
+
+            for ($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]);
+
+        $keys = array('EXISTS', 'RECENT', 'UNSEEN', 'UID-MAP');
+
+        foreach ($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);
+
+        $keys = array('UIDNEXT', 'UIDVALIDITY', 'HIGHESTMODSEQ', 'NOMODSEQ',
+            'PERMANENTFLAGS', 'QRESYNC', 'VANISHED', 'READ-WRITE');
+
+        foreach ($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)) {
+            $this->prefs['literal+'] = true;
+        }
+
+        if ($trusted) {
+            $this->capability_readed = true;
+        }
+    }
+
+    /**
+     * Escapes a string when it contains special characters (RFC3501)
+     *
+     * @param string  $string       IMAP string
+     * @param boolean $force_quotes Forces string quoting (for atoms)
+     *
+     * @return string String atom, quoted-string or string literal
+     * @todo lists
+     */
+    public static function escape($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 boolean  $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($this->debug_handler, array(&$this, $message));
+        }
+        else {
+            echo "DEBUG: $message\n";
+        }
+    }
+}