[squirrelmail.git] / functions / addressbook.php

<?php

/**
 * functions/addressbook.php - Functions and classes for the addressbook system
 *
 * Functions require SM_PATH and support of forms.php functions
 *
 * @copyright &copy; 1999-2006 The SquirrelMail Project Team
 * @license http://opensource.org/licenses/gpl-license.php GNU Public License
 * @version $Id$
 * @package squirrelmail
 * @subpackage addressbook
 */


/* required includes */
// FIXME, NO display code in functions files
include_once(SM_PATH . 'templates/util_global.php');

/**
 * Create and initialize an addressbook object.
 * @param boolean $showerr display any address book init errors. html page header
 * must be created before calling addressbook_init() with $showerr enabled.
 * @param boolean $onlylocal enable only local address book backends
 * @return object address book object.
 */
function addressbook_init($showerr = true, $onlylocal = false) {
    global $data_dir, $username, $color, $ldap_server, $address_book_global_filename;
    global $addrbook_dsn, $addrbook_table;
    global $abook_global_file, $abook_global_file_writeable, $abook_global_file_listing;
    global $addrbook_global_dsn, $addrbook_global_table, $addrbook_global_writeable, $addrbook_global_listing;

    /* Create a new addressbook object */
    $abook = new AddressBook;

    /* Create empty error message */
    $abook_init_error='';

    /*
        Always add a local backend. We use *either* file-based *or* a
        database addressbook. If $addrbook_dsn is set, the database
        backend is used. If not, addressbooks are stores in files.
    */
    if (isset($addrbook_dsn) && !empty($addrbook_dsn)) {
        /* Database */
        if (!isset($addrbook_table) || empty($addrbook_table)) {
            $addrbook_table = 'address';
        }
        $r = $abook->add_backend('database', Array('dsn' => $addrbook_dsn,
                            'owner' => $username,
                            'table' => $addrbook_table));
        if (!$r && $showerr) {
            $abook_init_error.=_("Error initializing addressbook database.") . "<br />\n" . $abook->error;
        }
    } else {
        /* File */
        $filename = getHashedFile($username, $data_dir, "$username.abook");
        $r = $abook->add_backend('local_file', Array('filename' => $filename,
                              'create'   => true));
        if(!$r && $showerr) {
            // no need to use $abook->error, because message explains error.
            $abook_init_error.=sprintf( _("Error opening file %s"), $filename );
        }
    }

    /* Global file based addressbook */
    if (isset($abook_global_file) &&
        isset($abook_global_file_writeable) &&
        isset($abook_global_file_listing) &&
        trim($abook_global_file)!=''){

        // Detect place of address book
        if (! preg_match("/[\/\\\]/",$abook_global_file)) {
            /* no path chars, address book stored in data directory
             * make sure that there is a slash between data directory
             * and address book file name
             */
            $abook_global_filename=$data_dir
                . ((substr($data_dir, -1) != '/') ? '/' : '')
                . $abook_global_file;
        } elseif (preg_match("/^\/|\w:/",$abook_global_file)) {
            // full path is set in options (starts with slash or x:)
            $abook_global_filename=$abook_global_file;
        } else {
            $abook_global_filename=SM_PATH . $abook_global_file;
        }

        $r = $abook->add_backend('local_file',array('filename'=>$abook_global_filename,
                                                    'name' => _("Global address book"),
                                                    'detect_writeable' => false,
                                                    'writeable'=> $abook_global_file_writeable,
                                                    'listing' => $abook_global_file_listing));

        /* global abook init error is not fatal. add error message and continue */
        if (!$r && $showerr) {
            if ($abook_init_error!='') $abook_init_error.="<br />\n";
            $abook_init_error.=_("Error initializing global addressbook.") . "<br />\n" . $abook->error;
        }
    }

    /* Load global addressbook from SQL if configured */
    if (isset($addrbook_global_dsn) && !empty($addrbook_global_dsn)) {
      /* Database configured */
      if (!isset($addrbook_global_table) || empty($addrbook_global_table)) {
          $addrbook_global_table = 'global_abook';
      }
      $r = $abook->add_backend('database',
                               Array('dsn' => $addrbook_global_dsn,
                                     'owner' => 'global',
                                     'name' => _("Global address book"),
                                     'writeable' => $addrbook_global_writeable,
                                     'listing' => $addrbook_global_listing,
                                     'table' => $addrbook_global_table));
      /* global abook init error is not fatal. add error message and continue */
      if (!$r && $showerr) {
          if ($abook_init_error!='') $abook_init_error.="<br />\n";
          $abook_init_error.=_("Error initializing global addressbook.") . "<br />\n" . $abook->error;
      }
    }

    /*
     * hook allows to include different address book backends.
     * plugins should extract $abook and $r from arguments
     * and use same add_backend commands as above functions.
     * @since 1.5.1 and 1.4.5
     */
    $hookReturn = do_hook('abook_init', $abook, $r);
    $abook = $hookReturn[1];
    $r = $hookReturn[2];

    if (! $onlylocal) {
        /* Load configured LDAP servers (if PHP has LDAP support) */
        if (isset($ldap_server) && is_array($ldap_server)) {
            reset($ldap_server);
            while (list($undef,$param) = each($ldap_server)) {
                if (is_array($param)) {
                    $r = $abook->add_backend('ldap_server', $param);
                    if (!$r && $showerr) {
                        if ($abook_init_error!='') $abook_init_error.="<br />\n";
                        $abook_init_error.=sprintf(_("Error initializing LDAP server %s:") .
                                "<br />\n", $param['host']);
                        $abook_init_error.= $abook->error;
                    }
                }
            }
        } // end of ldap server init
    } // end of remote abook backend init

    /**
     * display address book init errors.
     */
    if ($abook_init_error!='' && $showerr) {
        error_box($abook_init_error,$color);
    }

    /* Return the initialized object */
    return $abook;
}

/**
 * Display the "new address" form
 *
 * Form is not closed and you must add closing form tag.
 * @since 1.5.1
 * @param string $form_url form action url
 * @param string $name form name
 * @param string $title form title
 * @param string $button form button name
 * @param array $defdata values of form fields
 */
function abook_create_form($form_url,$name,$title,$button,$defdata=array()) {
    global $color;
    echo addForm($form_url, 'post', 'f_add').
        html_tag( 'table',
                  html_tag( 'tr',
                            html_tag( 'td', "\n". '<strong>' . $title . '</strong>' . "\n",
                                      'center', $color[0]
                                      )
                            )
                  , 'center', '', 'width="90%"' ) ."\n";
    address_form($name, $button, $defdata);
}


/**
 *   Had to move this function outside of the Addressbook Class
 *   PHP 4.0.4 Seemed to be having problems with inline functions.
 *   Note: this can return now since we don't support 4.0.4 anymore.
 */
function addressbook_cmp($a,$b) {

    if($a['backend'] > $b['backend']) {
        return 1;
    } else if($a['backend'] < $b['backend']) {
        return -1;
    }

    return (strtolower($a['name']) > strtolower($b['name'])) ? 1 : -1;

}

/**
 * Make an input field
 * @param string $label
 * @param string $field
 * @param string $name
 * @param string $size
 * @param array $values
 * @param string $add
 */
function addressbook_inp_field($label, $field, $name, $size, $values, $add='') {
    global $color;
    $value = ( isset($values[$field]) ? $values[$field] : '');

    if (is_array($value)) {
        $td_str = addSelect($name.'['.$field.']', $value);
    } else {
        $td_str = addInput($name.'['.$field.']', $value, $size);
    }
    $td_str .= $add ;

    return html_tag( 'tr' ,
            html_tag( 'td', $label . ':', 'right', $color[4]) .
            html_tag( 'td', $td_str, 'left', $color[4])
            )
        . "\n";
}

/**
 * Output form to add and modify address data
 */
function address_form($name, $submittext, $values = array()) {
    global $color, $squirrelmail_language;

    if ($squirrelmail_language == 'ja_JP') {
        echo html_tag( 'table',
                addressbook_inp_field(_("Nickname"),     'nickname', $name, 15, $values,
                    ' <small>' . _("Must be unique") . '</small>') .
                addressbook_inp_field(_("E-mail address"),  'email', $name, 45, $values, '') .
                addressbook_inp_field(_("Last name"),    'lastname', $name, 45, $values, '') .
                addressbook_inp_field(_("First name"),  'firstname', $name, 45, $values, '') .
                addressbook_inp_field(_("Additional info"), 'label', $name, 45, $values, '') .
                list_writable_backends($name) .
                html_tag( 'tr',
                    html_tag( 'td',
                        addSubmit($submittext, $name.'[SUBMIT]'),
                        'center', $color[4], 'colspan="2"')
                    )
                , 'center', '', 'border="0" cellpadding="1" width="90%"') ."\n";
    } else {
        echo html_tag( 'table',
                addressbook_inp_field(_("Nickname"),     'nickname', $name, 15, $values,
                    ' <small>' . _("Must be unique") . '</small>') .
                addressbook_inp_field(_("E-mail address"),  'email', $name, 45, $values, '') .
                addressbook_inp_field(_("First name"),  'firstname', $name, 45, $values, '') .
                addressbook_inp_field(_("Last name"),    'lastname', $name, 45, $values, '') .
                addressbook_inp_field(_("Additional info"), 'label', $name, 45, $values, '') .
                list_writable_backends($name) .
                html_tag( 'tr',
                    html_tag( 'td',
                        addSubmit($submittext, $name.'[SUBMIT]') ,
                        'center', $color[4], 'colspan="2"')
                    )
                , 'center', '', 'border="0" cellpadding="1" width="90%"') ."\n";
    }
}

/**
 * Provides list of writeable backends.
 * Works only when address is added ($name='addaddr')
 * @param string $name name of form
 * @return string html formated backend field (select or hidden)
 */
function list_writable_backends($name) {
    global $color, $abook;
    if ( $name != 'addaddr' ) { return; }
    $writeable_abook = 1;
    if ( $abook->numbackends > 1 ) {
        $backends = $abook->get_backend_list();
        $writeable_abooks=array();
        while (list($undef,$v) = each($backends)) {
            if ($v->writeable) {
                // add each backend to array
                $writeable_abooks[$v->bnum]=$v->sname;
                // save backend number
                $writeable_abook=$v->bnum;
            }
        }
        if (count($writeable_abooks)>1) {
            // we have more than one writeable backend
            $ret=addSelect('backend',$writeable_abooks,null,true);
            return html_tag( 'tr',
                             html_tag( 'td', _("Add to:"),'right', $color[4] ) .
                             html_tag( 'td', $ret, 'left', $color[4] )) . "\n";
        }
    }
    // Only one backend exists or is writeable.
    return html_tag( 'tr',
                     html_tag( 'td',
                               addHidden('backend', $writeable_abook),
                               'center', $color[4], 'colspan="2"')) . "\n";
}

/**
 * Sort array by the key "name"
 */
function alistcmp($a,$b) {
    $abook_sort_order=get_abook_sort();

    switch ($abook_sort_order) {
    case 0:
    case 1:
      $abook_sort='nickname';
      break;
    case 4:
    case 5:
      $abook_sort='email';
      break;
    case 6:
    case 7:
      $abook_sort='label';
      break;
    case 2:
    case 3:
    case 8:
    default:
      $abook_sort='name';
    }

    if ($a['backend'] > $b['backend']) {
        return 1;
    } else {
        if ($a['backend'] < $b['backend']) {
            return -1;
        }
    }

    if( (($abook_sort_order+2) % 2) == 1) {
      return (strtolower($a[$abook_sort]) < strtolower($b[$abook_sort])) ? 1 : -1;
    } else {
      return (strtolower($a[$abook_sort]) > strtolower($b[$abook_sort])) ? 1 : -1;
    }
}

/**
 * Address book sorting options
 *
 * returns address book sorting order
 * @return integer book sorting options order
 */
function get_abook_sort() {
    global $data_dir, $username;

    /* get sorting order */
    if(sqgetGlobalVar('abook_sort_order', $temp, SQ_GET)) {
      $abook_sort_order = (int) $temp;

      if ($abook_sort_order < 0 or $abook_sort_order > 8)
        $abook_sort_order=8;

      setPref($data_dir, $username, 'abook_sort_order', $abook_sort_order);
    } else {
      /* get previous sorting options. default to unsorted */
      $abook_sort_order = getPref($data_dir, $username, 'abook_sort_order', 8);
    }

    return $abook_sort_order;
}

/**
 * This function shows the address book sort button.
 *
 * @param integer $abook_sort_order current sort value
 * @param string $alt_tag alt tag value (string visible to text only browsers)
 * @param integer $Down sort value when list is sorted ascending
 * @param integer $Up sort value when list is sorted descending
 * @return string html code with sorting images and urls
 */
function show_abook_sort_button($abook_sort_order, $alt_tag, $Down, $Up ) {
    global $form_url, $icon_theme_path;

     /* Figure out which image we want to use. */
    if ($abook_sort_order != $Up && $abook_sort_order != $Down) {
        $img = 'sort_none.png';
        $text_icon = '&#9723;'; // U+25FB WHITE MEDIUM SQUARE
        $which = $Up;
    } elseif ($abook_sort_order == $Up) {
        $img = 'up_pointer.png';
        $text_icon = '&#8679;'; // U+21E7 UPWARDS WHITE ARROW
        $which = $Down;
    } else {
        $img = 'down_pointer.png';
        $text_icon = '&#8681;'; // U+21E9 DOWNWARDS WHITE ARROW
        $which = 8;
    }

    /* Now that we have everything figured out, show the actual button. */
    return '&nbsp;<a href="' . $form_url .'?abook_sort_order=' . $which .
           '" style="text-decoration:none" title="'.$alt_tag.'">' .
           getIcon($icon_theme_path, $img, $text_icon, $alt_tag) .
           '</a>';
}


/**
 * This is the main address book class that connect all the
 * backends and provide services to the functions above.
 * @package squirrelmail
 * @subpackage addressbook
 */
class AddressBook {

    /*
       Cleaning errors from html with htmlspecialchars:
       Errors from the backend are cleaned up in this class because we not always
       have control over it when error output is generated in the backend.
       If this appears to be wrong place then clean it up at the source (the backend)
    */

    /**
     * Enabled address book backends
     * @var array
     */
    var $backends    = array();
    /**
     * Number of enabled backends
     * @var integer
     */
    var $numbackends = 0;
    /**
     * Error messages
     * @var string
     */
    var $error       = '';
    /**
     * id of backend with personal address book
     * @var integer
     */
    var $localbackend = 0;
    /**
     * Name of backend with personal address book
     * @var string
     */
    var $localbackendname = '';
    /**
     * Controls use of 'extra' field
     *
     * Extra field can be used to add link to form, which allows
     * to modify all fields supported by backend. This is the only field
     * that is not sanitized with htmlspecialchars. Backends MUST make
     * sure that field data is sanitized and displayed correctly inside
     * table cell. Use of html formating in other address book fields is
     * not allowed. Backends that don't return 'extra' row in address book
     * data should not modify this object property.
     * @var boolean
     * @since 1.5.1
     */
    var $add_extra_field = false;

    /**
     * Constructor function.
     */
    function AddressBook() {
        $this->localbackendname = _("Personal address book");
    }

    /**
     * Return an array of backends of a given type,
     * or all backends if no type is specified.
     * @param string $type backend type
     * @return array list of backends
     */
    function get_backend_list($type = '') {
        $ret = array();
        for ($i = 1 ; $i <= $this->numbackends ; $i++) {
            if (empty($type) || $type == $this->backends[$i]->btype) {
                $ret[] = &$this->backends[$i];
            }
        }
        return $ret;
    }


    /* ========================== Public ======================== */

    /**
     * Add a new backend.
     *
     * @param string $backend backend name (without the abook_ prefix)
     * @param mixed optional variable that is passed to the backend constructor.
     * See each of the backend classes for valid parameters
     * @return integer number of backends
     */
    function add_backend($backend, $param = '') {
        static $backend_classes;
        if (!isset($backend_classes)) {
            $backend_classes = array();
        }
        if (!isset($backend_classes[$backend])) {
            /**
              * Support backend provided by plugins. Plugin function must
              * return an associative array with as key the backend name ($backend)
              * and as value the file including the path containing the backend class.
              * i.e.: $aBackend = array('backend_template' => SM_PATH . 'plugins/abook_backend_template/functions.php')
              *
              * NB: Because the backend files are included from within this function they DO NOT have access to
              * vars in the global scope. This function is the global scope for the included backend !!!
              */
            $aBackend = do_hook('abook_add_class');
            if (isset($aBackend) && is_array($aBackend) && isset($aBackend[$backend])) {
                require_once($aBackend[$backend]);
            } else {
                require_once(SM_PATH . 'functions/abook_'.$backend.'.php');
            }
            $backend_classes[$backend] = true;
        }
        $backend_name = 'abook_' . $backend;
        $newback = new $backend_name($param);
        //eval('$newback = new ' . $backend_name . '($param);');
        if(!empty($newback->error)) {
            $this->error = $newback->error;
            return false;
        }

        $this->numbackends++;

        $newback->bnum = $this->numbackends;
        $this->backends[$this->numbackends] = $newback;

        /* Store ID of first local backend added */
        if ($this->localbackend == 0 && $newback->btype == 'local') {
            $this->localbackend = $this->numbackends;
            $this->localbackendname = $newback->sname;
        }

        return $this->numbackends;
    }


    /**
     * create string with name and email address
     *
     * This function takes a $row array as returned by the addressbook
     * search and returns an e-mail address with the full name or
     * nickname optionally prepended.
     * @param array $row address book entry
     * @return string email address with real name prepended
     */
    function full_address($row) {
        global $addrsrch_fullname, $data_dir, $username;
        $prefix = getPref($data_dir, $username, 'addrsrch_fullname');
        if (($prefix != "" || (isset($addrsrch_fullname) &&
            $prefix == $addrsrch_fullname)) && $prefix != 'noprefix') {
            $name = ($prefix == 'nickname' ? $row['nickname'] : $row['name']);
            return $name . ' <' . trim($row['email']) . '>';
        } else {
            return trim($row['email']);
        }
    }

    /**
     * Search for entries in address books
     *
     * Return a list of addresses matching expression in
     * all backends of a given type.
     * @param string $expression search expression
     * @param integer $bnum backend number. default to search in all backends
     * @return array search results
     */
    function search($expression, $bnum = -1) {
        $ret = array();
        $this->error = '';

        /* Search all backends */
        if ($bnum == -1) {
            $sel = $this->get_backend_list('');
            $failed = 0;
            for ($i = 0 ; $i < sizeof($sel) ; $i++) {
                $backend = &$sel[$i];
                $backend->error = '';
                $res = $backend->search($expression);
                if (is_array($res)) {
                    $ret = array_merge($ret, $res);
                } else {
                    $this->error .= "<br />\n" . htmlspecialchars($backend->error);
                    $failed++;
                }
            }

            /* Only fail if all backends failed */
            if( $failed >= sizeof( $sel ) ) {
                $ret = FALSE;
            }

        }  else {

            /* Search only one backend */

            $ret = $this->backends[$bnum]->search($expression);
            if (!is_array($ret)) {
                $this->error .= "<br />\n" . htmlspecialchars($this->backends[$bnum]->error);
                $ret = FALSE;
            }
        }

        return( $ret );
    }


    /**
     * Sorted search
     * @param string $expression search expression
     * @param integer $bnum backend number. default to search in all backends
     * @return array search results
     */
    function s_search($expression, $bnum = -1) {

        $ret = $this->search($expression, $bnum);
        if ( is_array( $ret ) ) {
            usort($ret, 'addressbook_cmp');
        }
        return $ret;
    }


    /**
     * Lookup an address by alias.
     * Only possible in local backends.
     * @param string $alias
     * @param integer backend number
     * @return array lookup results. False, if not found.
     */
    function lookup($alias, $bnum = -1) {

        $ret = array();

        if ($bnum > -1) {
            $res = $this->backends[$bnum]->lookup($alias);
            if (is_array($res)) {
               return $res;
            } else {
               $this->error = htmlspecialchars($this->backends[$bnum]->error);
               return false;
            }
        }

        $sel = $this->get_backend_list('local');
        for ($i = 0 ; $i < sizeof($sel) ; $i++) {
            $backend = &$sel[$i];
            $backend->error = '';
            $res = $backend->lookup($alias);
            if (is_array($res)) {
               if(!empty($res))
              return $res;
            } else {
               $this->error = htmlspecialchars($backend->error);
               return false;
            }
        }

        return $ret;
    }


    /**
     * Return all addresses
     * @param integer $bnum backend number
     * @return array search results
     */
    function list_addr($bnum = -1) {
        $ret = array();

        if ($bnum == -1) {
            $sel = $this->get_backend_list('');
        } else {
            $sel = array(0 => &$this->backends[$bnum]);
        }

        for ($i = 0 ; $i < sizeof($sel) ; $i++) {
            $backend = &$sel[$i];
            $backend->error = '';
            $res = $backend->list_addr();
            if (is_array($res)) {
               $ret = array_merge($ret, $res);
            } else {
               $this->error = htmlspecialchars($backend->error);
               return false;
            }
        }

        return $ret;
    }

    /**
     * Create a new address
     * @param array $userdata added address record
     * @param integer $bnum backend number
     * @return integer the backend number that the/ address was added
     * to, or false if it failed.
     */
    function add($userdata, $bnum) {

        /* Validate data */
        if (!is_array($userdata)) {
            $this->error = _("Invalid input data");
            return false;
        }
        if (empty($userdata['firstname']) && empty($userdata['lastname'])) {
            $this->error = _("Name is missing");
            return false;
        }
        if (empty($userdata['email'])) {
            $this->error = _("E-mail address is missing");
            return false;
        }
        if (empty($userdata['nickname'])) {
            $userdata['nickname'] = $userdata['email'];
        }

        if (eregi('[ \\:\\|\\#\\"\\!]', $userdata['nickname'])) {
            $this->error = _("Nickname contains illegal characters");
            return false;
        }

        /* Check that specified backend accept new entries */
        if (!$this->backends[$bnum]->writeable) {
            $this->error = _("Addressbook is read-only");
            return false;
        }

        /* Add address to backend */
        $res = $this->backends[$bnum]->add($userdata);
        if ($res) {
            return $bnum;
        } else {
            $this->error = htmlspecialchars($this->backends[$bnum]->error);
            return false;
        }

        return false;  // Not reached
    } /* end of add() */


    /**
     * Remove the entries from address book
     * @param mixed $alias entries that have to be removed. Can be string with nickname or array with list of nicknames
     * @param integer $bnum backend number
     * @return bool true if removed successfully. false if there s an error. $this->error contains error message
     */
    function remove($alias, $bnum) {

        /* Check input */
        if (empty($alias)) {
            return true;
        }

        /* Convert string to single element array */
        if (!is_array($alias)) {
            $alias = array(0 => $alias);
        }

        /* Check that specified backend is writable */
        if (!$this->backends[$bnum]->writeable) {
            $this->error = _("Addressbook is read-only");
            return false;
        }

        /* Remove user from backend */
        $res = $this->backends[$bnum]->remove($alias);
        if ($res) {
            return $bnum;
        } else {
            $this->error = htmlspecialchars($this->backends[$bnum]->error);
            return false;
        }

        return FALSE;  /* Not reached */
    } /* end of remove() */


    /**
     * Modify entry in address book
     * @param string $alias nickname
     * @param array $userdata newdata
     * @param integer $bnum backend number
     */
    function modify($alias, $userdata, $bnum) {

        /* Check input */
        if (empty($alias) || !is_string($alias)) {
            return true;
        }

        /* Validate data */
        if(!is_array($userdata)) {
            $this->error = _("Invalid input data");
            return false;
        }
        if (empty($userdata['firstname']) && empty($userdata['lastname'])) {
            $this->error = _("Name is missing");
            return false;
        }
        if (empty($userdata['email'])) {
            $this->error = _("E-mail address is missing");
            return false;
        }

        if (eregi('[\\: \\|\\#"\\!]', $userdata['nickname'])) {
            $this->error = _("Nickname contains illegal characters");
            return false;
        }

        if (empty($userdata['nickname'])) {
            $userdata['nickname'] = $userdata['email'];
        }

        /* Check that specified backend is writable */
        if (!$this->backends[$bnum]->writeable) {
            $this->error = _("Addressbook is read-only");;
            return false;
        }

        /* Modify user in backend */
        $res = $this->backends[$bnum]->modify($alias, $userdata);
        if ($res) {
            return $bnum;
        } else {
            $this->error = htmlspecialchars($this->backends[$bnum]->error);
            return false;
        }

        return FALSE;  /* Not reached */
    } /* end of modify() */


} /* End of class Addressbook */

/**
 * Generic backend that all other backends extend
 * @package squirrelmail
 * @subpackage addressbook
 */
class addressbook_backend {

    /* Variables that all backends must provide. */
    /**
     * Backend type
     *
     * Can be 'local' or 'remote'
     * @var string backend type
     */
    var $btype      = 'dummy';
    /**
     * Internal backend name
     * @var string
     */
    var $bname      = 'dummy';
    /**
     * Displayed backend name
     * @var string
     */
    var $sname      = 'Dummy backend';

    /*
     * Variables common for all backends, but that
     * should not be changed by the backends.
     */
    /**
     * Backend number
     * @var integer
     */
    var $bnum       = -1;
    /**
     * Error messages
     * @var string
     */
    var $error      = '';
    /**
     * Writeable flag
     * @var bool
     */
    var $writeable  = false;

    /**
     * Set error message
     * @param string $string error message
     * @return bool
     */
    function set_error($string) {
        $this->error = '[' . $this->sname . '] ' . $string;
        return false;
    }


    /* ========================== Public ======================== */

    /**
     * Search for entries in backend
     *
     * Working backend should support use of wildcards. * symbol
     * should match one or more symbols. ? symbol should match any
     * single symbol.
     * @param string $expression
     * @return bool
     */
    function search($expression) {
        $this->set_error('search not implemented');
        return false;
    }

    /**
     * Find entry in backend by alias
     * @param string $alias name used for id
     * @return bool
     */
    function lookup($alias) {
        $this->set_error('lookup not implemented');
        return false;
    }

    /**
     * List all entries in backend
     *
     * Working backend should provide this function or at least
     * dummy function that returns empty array.
     * @return bool
     */
    function list_addr() {
        $this->set_error('list_addr not implemented');
        return false;
    }

    /**
     * Add entry to backend
     * @param array userdata
     * @return bool
     */
    function add($userdata) {
        $this->set_error('add not implemented');
        return false;
    }

    /**
     * Remove entry from backend
     * @param string $alias name used for id
     * @return bool
     */
    function remove($alias) {
        $this->set_error('delete not implemented');
        return false;
    }

    /**
     * Modify entry in backend
     * @param string $alias name used for id
     * @param array $newuserdata new data
     * @return bool
     */
    function modify($alias, $newuserdata) {
        $this->set_error('modify not implemented');
        return false;
    }
}
?>