Merged devel-framework branch (r5746:5779) back into trunk

1 files changed, 1055 insertions, 0 deletions

diff --git a/program/include/rcube_storage.php b/program/include/rcube_storage.php
new file mode 100644
index 000000000..124d148e4
--- /dev/null
+++ b/program/include/rcube_storage.php
@@ -0,0 +1,1055 @@
+<?php
+
+/*
+ +-----------------------------------------------------------------------+
+ | program/include/rcube_storage.php                                     |
+ |                                                                       |
+ | This file is part of the Roundcube Webmail client                     |
+ | Copyright (C) 2005-2012, The Roundcube Dev Team                       |
+ | Copyright (C) 2012, Kolab Systems AG                                  |
+ | Licensed under the GNU GPL                                            |
+ |                                                                       |
+ | PURPOSE:                                                              |
+ |   Mail Storage Engine                                                 |
+ |                                                                       |
+ +-----------------------------------------------------------------------+
+ | Author: Thomas Bruederli <roundcube@gmail.com>                        |
+ | Author: Aleksander Machniak <alec@alec.pl>                            |
+ +-----------------------------------------------------------------------+
+
+ $Id$
+
+*/
+
+
+/**
+ * Abstract class for accessing mail messages storage server
+ *
+ * @package Mail
+ * @author  Thomas Bruederli <roundcube@gmail.com>
+ * @author  Aleksander Machniak <alec@alec.pl>
+ * @version 2.0
+ */
+abstract class rcube_storage
+{
+    /**
+     * Instance of connection object e.g. rcube_imap_generic
+     *
+     * @var mixed
+     */
+    public $conn;
+
+    protected $folder = 'INBOX';
+    protected $default_charset = 'ISO-8859-1';
+    protected $default_folders = array('INBOX');
+    protected $search_set;
+    protected $options = array('auth_method' => 'check');
+    protected $page_size = 10;
+    protected $threading = false;
+
+    /**
+     * All (additional) headers used (in any way) by Roundcube
+     * Not listed here: DATE, FROM, TO, CC, REPLY-TO, SUBJECT, CONTENT-TYPE, LIST-POST
+     * (used for messages listing) are hardcoded in rcube_imap_generic::fetchHeaders()
+     *
+     * @var array
+     */
+    protected $all_headers = array(
+        'IN-REPLY-TO',
+        'BCC',
+        'MESSAGE-ID',
+        'CONTENT-TRANSFER-ENCODING',
+        'REFERENCES',
+        'X-DRAFT-INFO',
+        'MAIL-FOLLOWUP-TO',
+        'MAIL-REPLY-TO',
+        'RETURN-PATH',
+    );
+
+    const UNKNOWN       = 0;
+    const NOPERM        = 1;
+    const READONLY      = 2;
+    const TRYCREATE     = 3;
+    const INUSE         = 4;
+    const OVERQUOTA     = 5;
+    const ALREADYEXISTS = 6;
+    const NONEXISTENT   = 7;
+    const CONTACTADMIN  = 8;
+
+
+    /**
+     * Connect to the server
+     *
+     * @param  string   $host    Host to connect
+     * @param  string   $user    Username for IMAP account
+     * @param  string   $pass    Password for IMAP account
+     * @param  integer  $port    Port to connect to
+     * @param  string   $use_ssl SSL schema (either ssl or tls) or null if plain connection
+     *
+     * @return boolean  TRUE on success, FALSE on failure
+     */
+    abstract function connect($host, $user, $pass, $port = 143, $use_ssl = null);
+
+
+    /**
+     * Close connection. Usually done on script shutdown
+     */
+    abstract function close();
+
+
+    /**
+     * Checks connection state.
+     *
+     * @return boolean  TRUE on success, FALSE on failure
+     */
+    abstract function is_connected();
+
+
+    /**
+     * Returns code of last error
+     *
+     * @return int Error code
+     */
+    abstract function get_error_code();
+
+
+    /**
+     * Returns message of last error
+     *
+     * @return string Error message
+     */
+    abstract function get_error_str();
+
+
+    /**
+     * Returns code of last command response
+     *
+     * @return int Response code (class constant)
+     */
+    abstract function get_response_code();
+
+
+    /**
+     * Set connection and class options
+     *
+     * @param array $opt Options array
+     */
+    public function set_options($opt)
+    {
+        $this->options = array_merge($this->options, (array)$opt);
+    }
+
+
+    /**
+     * Activate/deactivate debug mode.
+     *
+     * @param boolean $dbg True if conversation with the server should be logged
+     */
+    abstract function set_debug($dbg = true);
+
+
+    /**
+     * Set default message charset.
+     *
+     * This will be used for message decoding if a charset specification is not available
+     *
+     * @param  string $cs Charset string
+     */
+    public function set_charset($cs)
+    {
+        $this->default_charset = $cs;
+    }
+
+
+    /**
+     * This list of folders will be listed above all other folders
+     *
+     * @param  array $arr Indexed list of folder names
+     */
+    public function set_default_folders($arr)
+    {
+        if (is_array($arr)) {
+            $this->default_folders = $arr;
+
+            // add inbox if not included
+            if (!in_array('INBOX', $this->default_folders)) {
+                array_unshift($this->default_folders, 'INBOX');
+            }
+        }
+    }
+
+
+    /**
+     * Set internal folder reference.
+     * All operations will be perfomed on this folder.
+     *
+     * @param  string $folder  Folder name
+     */
+    public function set_folder($folder)
+    {
+        if ($this->folder == $folder) {
+            return;
+        }
+
+        $this->folder = $folder;
+    }
+
+
+    /**
+     * Returns the currently used folder name
+     *
+     * @return string Name of the folder
+     */
+    public function get_folder()
+    {
+        return $this->folder;
+    }
+
+
+    /**
+     * Set internal list page number.
+     *
+     * @param int $page Page number to list
+     */
+    public function set_page($page)
+    {
+        $this->list_page = (int) $page;
+    }
+
+
+    /**
+     * Gets internal list page number.
+     *
+     * @return int Page number
+     */
+    public function get_page()
+    {
+        return $this->list_page;
+    }
+
+
+    /**
+     * Set internal page size
+     *
+     * @param int $size Number of messages to display on one page
+     */
+    public function set_pagesize($size)
+    {
+        $this->page_size = (int) $size;
+    }
+
+
+    /**
+     * Get internal page size
+     *
+     * @return int Number of messages to display on one page
+     */
+    public function get_pagesize()
+    {
+        return $this->page_size;
+    }
+
+
+    /**
+     * Save a search result for future message listing methods.
+     *
+     * @param  mixed  $set  Search set in driver specific format
+     */
+    abstract function set_search_set($set);
+
+
+    /**
+     * Return the saved search set.
+     *
+     * @return array Search set in driver specific format, NULL if search wasn't initialized
+     */
+    abstract function get_search_set();
+
+
+    /**
+     * Returns the storage server's (IMAP) capability
+     *
+     * @param   string  $cap Capability name
+     *
+     * @return  mixed   Capability value or TRUE if supported, FALSE if not
+     */
+    abstract function get_capability($cap);
+
+
+    /**
+     * Sets threading flag to the best supported THREAD algorithm.
+     * Enable/Disable threaded mode.
+     *
+     * @param  boolean  $enable TRUE to enable and FALSE
+     *
+     * @return mixed   Threading algorithm or False if THREAD is not supported
+     */
+    public function set_threading($enable = false)
+    {
+        $this->threading = false;
+
+        if ($enable && ($caps = $this->get_capability('THREAD'))) {
+            $methods = array('REFS', 'REFERENCES', 'ORDEREDSUBJECT');
+            $methods = array_intersect($methods, $caps);
+
+            $this->threading = array_shift($methods);
+        }
+
+        return $this->threading;
+    }
+
+
+    /**
+     * Get current threading flag.
+     *
+     * @return mixed  Threading algorithm or False if THREAD is not supported or disabled
+     */
+    public function get_threading()
+    {
+        return $this->threading;
+    }
+
+
+    /**
+     * Checks the PERMANENTFLAGS capability of the current folder
+     * and returns true if the given flag is supported by the server.
+     *
+     * @param   string  $flag Permanentflag name
+     *
+     * @return  boolean True if this flag is supported
+     */
+    abstract function check_permflag($flag);
+
+
+    /**
+     * Returns the delimiter that is used by the server
+     * for folder hierarchy separation.
+     *
+     * @return  string  Delimiter string
+     */
+    abstract function get_hierarchy_delimiter();
+
+
+    /**
+     * Get namespace
+     *
+     * @param string $name Namespace array index: personal, other, shared, prefix
+     *
+     * @return  array  Namespace data
+     */
+    abstract function get_namespace($name = null);
+
+
+    /**
+     * Get messages count for a specific folder.
+     *
+     * @param  string  $folder  Folder name
+     * @param  string  $mode    Mode for count [ALL|THREADS|UNSEEN|RECENT]
+     * @param  boolean $force   Force reading from server and update cache
+     * @param  boolean $status  Enables storing folder status info (max UID/count),
+     *                          required for folder_status()
+     *
+     * @return int     Number of messages
+     */
+    abstract function count($folder = null, $mode = 'ALL', $force = false, $status = true);
+
+
+    /**
+     * Public method for listing headers.
+     *
+     * @param   string   $folder     Folder name
+     * @param   int      $page       Current page to list
+     * @param   string   $sort_field Header field to sort by
+     * @param   string   $sort_order Sort order [ASC|DESC]
+     * @param   int      $slice      Number of slice items to extract from result array
+     *
+     * @return  array    Indexed array with message header objects
+     */
+    abstract function list_messages($folder = null, $page = null, $sort_field = null, $sort_order = null, $slice = 0);
+
+
+    /**
+     * Return sorted list of message UIDs
+     *
+     * @param string $folder     Folder to get index from
+     * @param string $sort_field Sort column
+     * @param string $sort_order Sort order [ASC, DESC]
+     *
+     * @return rcube_result_index|rcube_result_thread List of messages (UIDs)
+     */
+    abstract function index($folder = null, $sort_field = null, $sort_order = null);
+
+
+    /**
+     * Invoke search request to the server.
+     *
+     * @param  string  $folder     Folder name to search in
+     * @param  string  $str        Search criteria
+     * @param  string  $charset    Search charset
+     * @param  string  $sort_field Header field to sort by
+     *
+     * @todo: Search criteria should be provided in non-IMAP format, eg. array
+     */
+    abstract function search($folder = null, $str = 'ALL', $charset = null, $sort_field = null);
+
+
+    /**
+     * Direct (real and simple) search request (without result sorting and caching).
+     *
+     * @param  string  $folder  Folder name to search in
+     * @param  string  $str     Search string
+     *
+     * @return rcube_result_index  Search result (UIDs)
+     */
+    abstract function search_once($folder = null, $str = 'ALL');
+
+
+    /**
+     * Refresh saved search set
+     *
+     * @return array Current search set
+     */
+    abstract function refresh_search();
+
+
+    /* --------------------------------
+     *        messages management
+     * --------------------------------*/
+
+    /**
+     * Fetch message headers and body structure from the server and build
+     * an object structure similar to the one generated by PEAR::Mail_mimeDecode
+     *
+     * @param int     $uid     Message UID to fetch
+     * @param string  $folder  Folder to read from
+     *
+     * @return object rcube_mail_header Message data
+     */
+    abstract function get_message($uid, $folder = null);
+
+
+    /**
+     * Return message headers object of a specific message
+     *
+     * @param int     $id       Message sequence ID or UID
+     * @param string  $folder   Folder to read from
+     * @param bool    $force    True to skip cache
+     *
+     * @return rcube_mail_header Message headers
+     */
+    abstract function get_message_headers($uid, $folder = null, $force = false);
+
+
+    /**
+     * Fetch message body of a specific message from the server
+     *
+     * @param  int                $uid    Message UID
+     * @param  string             $part   Part number
+     * @param  rcube_message_part $o_part Part object created by get_structure()
+     * @param  mixed              $print  True to print part, ressource to write part contents in
+     * @param  resource           $fp     File pointer to save the message part
+     * @param  boolean            $skip_charset_conv Disables charset conversion
+     *
+     * @return string Message/part body if not printed
+     */
+    abstract function get_message_part($uid, $part = 1, $o_part = null, $print = null, $fp = null, $skip_charset_conv = false);
+
+
+    /**
+     * Fetch message body of a specific message from the server
+     *
+     * @param  int    $uid  Message UID
+     *
+     * @return string $part Message/part body
+     * @see    rcube_imap::get_message_part()
+     */
+    public function get_body($uid, $part = 1)
+    {
+        $headers = $this->get_message_headers($uid);
+        return rcube_charset_convert($this->get_message_part($uid, $part, null),
+            $headers->charset ? $headers->charset : $this->default_charset);
+    }
+
+
+    /**
+     * Returns the whole message source as string (or saves to a file)
+     *
+     * @param int      $uid Message UID
+     * @param resource $fp  File pointer to save the message
+     *
+     * @return string Message source string
+     */
+    abstract function get_raw_body($uid, $fp = null);
+
+
+    /**
+     * Returns the message headers as string
+     *
+     * @param int $uid  Message UID
+     *
+     * @return string Message headers string
+     */
+    abstract function get_raw_headers($uid);
+
+
+    /**
+     * Sends the whole message source to stdout
+     */
+    abstract function print_raw_body($uid);
+
+
+    /**
+     * Set message flag to one or several messages
+     *
+     * @param mixed   $uids       Message UIDs as array or comma-separated string, or '*'
+     * @param string  $flag       Flag to set: SEEN, UNDELETED, DELETED, RECENT, ANSWERED, DRAFT, MDNSENT
+     * @param string  $folder     Folder name
+     * @param boolean $skip_cache True to skip message cache clean up
+     *
+     * @return bool  Operation status
+     */
+    abstract function set_flag($uids, $flag, $folder = null, $skip_cache = false);
+
+
+    /**
+     * Remove message flag for one or several messages
+     *
+     * @param mixed  $uids    Message UIDs as array or comma-separated string, or '*'
+     * @param string $flag    Flag to unset: SEEN, DELETED, RECENT, ANSWERED, DRAFT, MDNSENT
+     * @param string $folder  Folder name
+     *
+     * @return bool   Operation status
+     * @see set_flag
+     */
+    public function unset_flag($uids, $flag, $folder = null)
+    {
+        return $this->set_flag($uids, 'UN'.$flag, $folder);
+    }
+
+
+    /**
+     * Append a mail message (source) to a specific folder.
+     *
+     * @param string  $folder  Target folder
+     * @param string  $message The message source string or filename
+     * @param string  $headers Headers string if $message contains only the body
+     * @param boolean $is_file True if $message is a filename
+     *
+     * @return int|bool Appended message UID or True on success, False on error
+     */
+    abstract function save_message($folder, &$message, $headers = '', $is_file = false);
+
+
+    /**
+     * Move message(s) from one folder to another.
+     *
+     * @param mixed  $uids  Message UIDs as array or comma-separated string, or '*'
+     * @param string $to    Target folder
+     * @param string $from  Source folder
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function move_message($uids, $to, $from = null);
+
+
+    /**
+     * Copy message(s) from one mailbox to another.
+     *
+     * @param mixed  $uids  Message UIDs as array or comma-separated string, or '*'
+     * @param string $to    Target folder
+     * @param string $from  Source folder
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function copy_message($uids, $to, $from = null);
+
+
+    /**
+     * Mark message(s) as deleted and expunge.
+     *
+     * @param mixed  $uids    Message UIDs as array or comma-separated string, or '*'
+     * @param string $folder  Source folder
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function delete_message($uids, $folder = null);
+
+
+    /**
+     * Expunge message(s) and clear the cache.
+     *
+     * @param mixed   $uids        Message UIDs as array or comma-separated string, or '*'
+     * @param string  $folder      Folder name
+     * @param boolean $clear_cache False if cache should not be cleared
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function expunge_message($uids, $folder = null, $clear_cache = true);
+
+
+    /**
+     * Parse message UIDs input
+     *
+     * @param mixed  $uids  UIDs array or comma-separated list or '*' or '1:*'
+     *
+     * @return array Two elements array with UIDs converted to list and ALL flag
+     */
+    protected function parse_uids($uids)
+    {
+        if ($uids === '*' || $uids === '1:*') {
+            if (empty($this->search_set)) {
+                $uids = '1:*';
+                $all = true;
+            }
+            // get UIDs from current search set
+            else {
+                $uids = join(',', $this->search_set->get());
+            }
+        }
+        else {
+            if (is_array($uids)) {
+                $uids = join(',', $uids);
+            }
+
+            if (preg_match('/[^0-9,]/', $uids)) {
+                $uids = '';
+            }
+        }
+
+        return array($uids, (bool) $all);
+    }
+
+
+    /* --------------------------------
+     *        folder managment
+     * --------------------------------*/
+
+    /**
+     * Get a list of subscribed folders.
+     *
+     * @param   string  $root      Optional root folder
+     * @param   string  $name      Optional name pattern
+     * @param   string  $filter    Optional filter
+     * @param   string  $rights    Optional ACL requirements
+     * @param   bool    $skip_sort Enable to return unsorted list (for better performance)
+     *
+     * @return  array   List of folders
+     */
+    abstract function list_folders_subscribed($root = '', $name = '*', $filter = null, $rights = null, $skip_sort = false);
+
+
+    /**
+     * Get a list of all folders available on the server.
+     *
+     * @param string  $root      IMAP root dir
+     * @param string  $name      Optional name pattern
+     * @param mixed   $filter    Optional filter
+     * @param string  $rights    Optional ACL requirements
+     * @param bool    $skip_sort Enable to return unsorted list (for better performance)
+     *
+     * @return array Indexed array with folder names
+     */
+    abstract function list_folders($root = '', $name = '*', $filter = null, $rights = null, $skip_sort = false);
+
+
+    /**
+     * Subscribe to a specific folder(s)
+     *
+     * @param array $folders Folder name(s)
+     *
+     * @return boolean True on success
+     */
+    abstract function subscribe($folders);
+
+
+    /**
+     * Unsubscribe folder(s)
+     *
+     * @param array $folders Folder name(s)
+     *
+     * @return boolean True on success
+     */
+    abstract function unsubscribe($folders);
+
+
+    /**
+     * Create a new folder on the server.
+     *
+     * @param string  $folder    New folder name
+     * @param boolean $subscribe True if the newvfolder should be subscribed
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function create_folder($folder, $subscribe = false);
+
+
+    /**
+     * Set a new name to an existing folder
+     *
+     * @param string $folder   Folder to rename
+     * @param string $new_name New folder name
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function rename_folder($folder, $new_name);
+
+
+    /**
+     * Remove a folder from the server.
+     *
+     * @param string $folder Folder name
+     *
+     * @return boolean True on success, False on error
+     */
+    abstract function delete_folder($folder);
+
+
+    /**
+     * Send expunge command and clear the cache.
+     *
+     * @param string  $folder      Folder name
+     * @param boolean $clear_cache False if cache should not be cleared
+     *
+     * @return boolean True on success, False on error
+     */
+    public function expunge_folder($folder = null, $clear_cache = true)
+    {
+        return $this->expunge_message('*', $folder, $clear_cache);
+    }
+
+
+    /**
+     * Remove all messages in a folder..
+     *
+     * @param string  $folder  Folder name
+     *
+     * @return boolean True on success, False on error
+     */
+    public function clear_folder($folder = null)
+    {
+        return $this->delete_message('*', $folder);
+    }
+
+
+    /**
+     * Checks if folder exists and is subscribed
+     *
+     * @param string   $folder       Folder name
+     * @param boolean  $subscription Enable subscription checking
+     *
+     * @return boolean True if folder exists, False otherwise
+     */
+    abstract function folder_exists($folder, $subscription = false);
+
+
+    /**
+     * Get folder size (size of all messages in a folder)
+     *
+     * @param string $folder Folder name
+     *
+     * @return int Folder size in bytes, False on error
+     */
+    abstract function folder_size($folder);
+
+
+    /**
+     * Returns the namespace where the folder is in
+     *
+     * @param string $folder Folder name
+     *
+     * @return string One of 'personal', 'other' or 'shared'
+     */
+    abstract function folder_namespace($folder);
+
+
+    /**
+     * Gets folder attributes (from LIST response, e.g. \Noselect, \Noinferiors).
+     *
+     * @param string $folder  Folder name
+     * @param bool   $force   Set to True if attributes should be refreshed
+     *
+     * @return array Options list
+     */
+    abstract function folder_attributes($folder, $force = false);
+
+
+    /**
+     * Gets connection (and current folder) data: UIDVALIDITY, EXISTS, RECENT,
+     * PERMANENTFLAGS, UIDNEXT, UNSEEN
+     *
+     * @param string $folder Folder name
+     *
+     * @return array Data
+     */
+    abstract function folder_data($folder);
+
+
+    /**
+     * Returns extended information about the folder.
+     *
+     * @param string $folder Folder name
+     *
+     * @return array Data
+     */
+    abstract function folder_info($folder);
+
+
+    /**
+     * Returns current status of a folder
+     *
+     * @param string $folder Folder name
+     *
+     * @return int Folder status
+     */
+    abstract function folder_status($folder = null);
+
+
+    /**
+     * Synchronizes messages cache.
+     *
+     * @param string $folder Folder name
+     */
+    abstract function folder_sync($folder);
+
+
+    /**
+     * Modify folder name according to namespace.
+     * For output it removes prefix of the personal namespace if it's possible.
+     * For input it adds the prefix. Use it before creating a folder in root
+     * of the folders tree.
+     *
+     * @param string $folder  Folder name
+     * @param string $mode    Mode name (out/in)
+     *
+     * @return string Folder name
+     */
+    abstract function mod_folder($folder, $mode = 'out');
+
+
+    /**
+     * Create all folders specified as default
+     */
+    public function create_default_folders()
+    {
+        // create default folders if they do not exist
+        foreach ($this->default_folders as $folder) {
+            if (!$this->folder_exists($folder)) {
+                $this->create_folder($folder, true);
+            }
+            else if (!$this->folder_exists($folder, true)) {
+                $this->subscribe($folder);
+            }
+        }
+    }
+
+
+    /**
+     * Get mailbox quota information.
+     *
+     * @return mixed Quota info or False if not supported
+     */
+    abstract function get_quota();
+
+
+    /* -----------------------------------------
+     *   ACL and METADATA methods
+     * ----------------------------------------*/
+
+    /**
+     * Changes the ACL on the specified folder (SETACL)
+     *
+     * @param string $folder  Folder name
+     * @param string $user    User name
+     * @param string $acl     ACL string
+     *
+     * @return boolean True on success, False on failure
+     */
+    abstract function set_acl($folder, $user, $acl);
+
+
+    /**
+     * Removes any <identifier,rights> pair for the
+     * specified user from the ACL for the specified
+     * folder (DELETEACL).
+     *
+     * @param string $folder  Folder name
+     * @param string $user    User name
+     *
+     * @return boolean True on success, False on failure
+     */
+    abstract function delete_acl($folder, $user);
+
+
+    /**
+     * Returns the access control list for a folder (GETACL).
+     *
+     * @param string $folder Folder name
+     *
+     * @return array User-rights array on success, NULL on error
+     */
+    abstract function get_acl($folder);
+
+
+    /**
+     * Returns information about what rights can be granted to the
+     * user (identifier) in the ACL for the folder (LISTRIGHTS).
+     *
+     * @param string $folder  Folder name
+     * @param string $user    User name
+     *
+     * @return array List of user rights
+     */
+    abstract function list_rights($folder, $user);
+
+
+    /**
+     * Returns the set of rights that the current user has to a folder (MYRIGHTS).
+     *
+     * @param string $folder Folder name
+     *
+     * @return array MYRIGHTS response on success, NULL on error
+     */
+    abstract function my_rights($folder);
+
+
+    /**
+     * Sets metadata/annotations (SETMETADATA/SETANNOTATION)
+     *
+     * @param string $folder  Folder name (empty for server metadata)
+     * @param array  $entries Entry-value array (use NULL value as NIL)
+     *
+     * @return boolean True on success, False on failure
+     */
+    abstract function set_metadata($folder, $entries);
+
+
+    /**
+     * Unsets metadata/annotations (SETMETADATA/SETANNOTATION)
+     *
+     * @param string $folder  Folder name (empty for server metadata)
+     * @param array  $entries Entry names array
+     *
+     * @return boolean True on success, False on failure
+     */
+    abstract function delete_metadata($folder, $entries);
+
+
+    /**
+     * Returns folder metadata/annotations (GETMETADATA/GETANNOTATION).
+     *
+     * @param string $folder   Folder name (empty for server metadata)
+     * @param array  $entries  Entries
+     * @param array  $options  Command options (with MAXSIZE and DEPTH keys)
+     *
+     * @return array Metadata entry-value hash array on success, NULL on error
+     */
+    abstract function get_metadata($folder, $entries, $options = array());
+
+
+    /* -----------------------------------------
+     *   Cache related functions
+     * ----------------------------------------*/
+
+    /**
+     * Clears the cache.
+     *
+     * @param string  $key         Cache key name or pattern
+     * @param boolean $prefix_mode Enable it to clear all keys starting
+     *                             with prefix specified in $key
+     */
+    abstract function clear_cache($key = null, $prefix_mode = false);
+
+    /**
+     * Returns cached value
+     *
+     * @param string $key Cache key
+     *
+     * @return mixed Cached value
+     */
+    abstract function get_cache($key);
+
+}  // end class rcube_storage
+
+
+/**
+ * Class representing a message part
+ *
+ * @package Mail
+ */
+class rcube_message_part
+{
+    var $mime_id = '';
+    var $ctype_primary = 'text';
+    var $ctype_secondary = 'plain';
+    var $mimetype = 'text/plain';
+    var $disposition = '';
+    var $filename = '';
+    var $encoding = '8bit';
+    var $charset = '';
+    var $size = 0;
+    var $headers = array();
+    var $d_parameters = array();
+    var $ctype_parameters = array();
+
+    function __clone()
+    {
+        if (isset($this->parts)) {
+            foreach ($this->parts as $idx => $part) {
+                if (is_object($part)) {
+                    $this->parts[$idx] = clone $part;
+                }
+            }
+        }
+    }
+}
+
+
+/**
+ * Class for sorting an array of rcube_mail_header objects in a predetermined order.
+ *
+ * @package Mail
+ * @author Eric Stadtherr
+ */
+class rcube_header_sorter
+{
+    private $uids = array();
+
+
+    /**
+     * Set the predetermined sort order.
+     *
+     * @param array $index  Numerically indexed array of IMAP UIDs
+     */
+    function set_index($index)
+    {
+        $index = array_flip($index);
+
+        $this->uids = $index;
+    }
+
+    /**
+     * Sort the array of header objects
+     *
+     * @param array $headers Array of rcube_mail_header objects indexed by UID
+     */
+    function sort_headers(&$headers)
+    {
+        uksort($headers, array($this, "compare_uids"));
+    }
+
+    /**
+     * Sort method called by uksort()
+     *
+     * @param int $a Array key (UID)
+     * @param int $b Array key (UID)
+     */
+    function compare_uids($a, $b)
+    {
+        // then find each sequence number in my ordered list
+        $posa = isset($this->uids[$a]) ? intval($this->uids[$a]) : -1;
+        $posb = isset($this->uids[$b]) ? intval($this->uids[$b]) : -1;
+
+        // return the relative position as the comparison value
+        return $posa - $posb;
+    }
+}