/backend/zarafa/mapi/class.baserecurrence.php

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<?php
/*
 * Copyright 2005 - 2012  Zarafa B.V.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation with the following additional
 * term according to sec. 7:
 *
 * According to sec. 7 of the GNU Affero General Public License, version
 * 3, the terms of the AGPL are supplemented with the following terms:
 *
 * "Zarafa" is a registered trademark of Zarafa B.V. The licensing of
 * the Program under the AGPL does not imply a trademark license.
 * Therefore any rights, title and interest in our trademarks remain
 * entirely with us.
 *
 * However, if you propagate an unmodified version of the Program you are
 * allowed to use the term "Zarafa" to indicate that you distribute the
 * Program. Furthermore you may use our trademarks where it is necessary
 * to indicate the intended purpose of a product or service provided you
 * use it in accordance with honest practices in industrial or commercial
 * matters.  If you want to propagate modified versions of the Program
 * under the name "Zarafa" or "Zarafa Server", you may only do so if you
 * have a written permission by Zarafa B.V. (to acquire a permission
 * please contact Zarafa at trademark@zarafa.com).
 *
 * The interactive user interface of the software displays an attribution
 * notice containing the term "Zarafa" and/or the logo of Zarafa.
 * Interactive user interfaces of unmodified and modified versions must
 * display Appropriate Legal Notices according to sec. 5 of the GNU
 * Affero General Public License, version 3, when you propagate
 * unmodified or modified versions of the Program. In accordance with
 * sec. 7 b) of the GNU Affero General Public License, version 3, these
 * Appropriate Legal Notices must retain the logo of Zarafa or display
 * the words "Initial Development by Zarafa" if the display of the logo
 * is not reasonably feasible for technical reasons. The use of the logo
 * of Zarafa in Legal Notices is allowed for unmodified and modified
 * versions of the software.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

    /**
     * BaseRecurrence
     * this class is superclass for recurrence for appointments and tasks. This class provides all
     * basic features of recurrence.
     */
    class BaseRecurrence
    {
        /**
         * @var object Mapi Message Store (may be null if readonly)
         */
        var $store;

        /**
         * @var object Mapi Message (may be null if readonly)
         */
        var $message;

        /**
         * @var array Message Properties
         */
        var $messageprops;

        /**
         * @var array list of property tags
         */
        var $proptags;

        /**
         * @var recurrence data of this calendar item
         */
        var $recur;

        /**
         * @var Timezone data of this calendar item
         */
        var $tz;

        /**
         * Constructor
         * @param resource $store MAPI Message Store Object
         * @param resource $message the MAPI (appointment) message
         * @param array $properties the list of MAPI properties the message has.
         */
        function BaseRecurrence($store, $message)
        {
            $this->store = $store;

            if(is_array($message)) {
                $this->messageprops = $message;
            } else {
                $this->message = $message;
                $this->messageprops = mapi_getprops($this->message, $this->proptags);
            }

            if(isset($this->messageprops[$this->proptags["recurring_data"]])) {
                // There is a possibility that recurr blob can be more than 255 bytes so get full blob through stream interface
                if (strlen($this->messageprops[$this->proptags["recurring_data"]]) >= 255) {
                    $this->getFullRecurrenceBlob();
                }

                $this->recur = $this->parseRecurrence($this->messageprops[$this->proptags["recurring_data"]]);
            }
            if(isset($this->proptags["timezone_data"]) && isset($this->messageprops[$this->proptags["timezone_data"]])) {
                $this->tz = $this->parseTimezone($this->messageprops[$this->proptags["timezone_data"]]);
            }
        }

        function getRecurrence()
        {
            return $this->recur;
        }

        function getFullRecurrenceBlob()
        {
            $message = mapi_msgstore_openentry($this->store, $this->messageprops[PR_ENTRYID]);

            $recurrBlob = '';
            $stream = mapi_openproperty($message, $this->proptags["recurring_data"], IID_IStream, 0, 0);
            $stat = mapi_stream_stat($stream);

            for ($i = 0; $i < $stat['cb']; $i += 1024) {
                $recurrBlob .= mapi_stream_read($stream, 1024);
            }

            if (!empty($recurrBlob)) {
                $this->messageprops[$this->proptags["recurring_data"]] = $recurrBlob;
            }
        }

        /**
        * Function for parsing the Recurrence value of a Calendar item.
        *
        * Retrieve it from Named Property 0x8216 as a PT_BINARY and pass the
        * data to this function
        *
        * Returns a structure containing the data:
        *
        * type        - type of recurrence: day=10, week=11, month=12, year=13
        * subtype    - type of day recurrence: 2=monthday (ie 21st day of month), 3=nday'th weekdays (ie. 2nd Tuesday and Wednesday)
        * start    - unix timestamp of first occurrence
        * end        - unix timestamp of last occurrence (up to and including), so when start == end -> occurrences = 1
        * numoccur     - occurrences (may be very large when there is no end data)
        *
        * then, for each type:
        *
        * Daily:
        *  everyn    - every [everyn] days in minutes
        *  regen    - regenerating event (like tasks)
        *
        * Weekly:
        *  everyn    - every [everyn] weeks in weeks
        *  regen    - regenerating event (like tasks)
        *  weekdays - bitmask of week days, where each bit is one weekday (weekdays & 1 = Sunday, weekdays & 2 = Monday, etc)
        *
        * Monthly:
        *  everyn    - every [everyn] months
        *  regen    - regenerating event (like tasks)
        *
        *  subtype 2:
        *      monthday - on day [monthday] of the month
        *
        *  subtype 3:
        *      weekdays - bitmask of week days, where each bit is one weekday (weekdays & 1 = Sunday, weekdays & 2 = Monday, etc)
        *   nday    - on [nday]'th [weekdays] of the month
        *
        * Yearly:
        *  everyn    - every [everyn] months (12, 24, 36, ...)
        *  month    - in month [month] (although the month is encoded in minutes since the startning of the year ........)
        *  regen    - regenerating event (like tasks)
        *
        *  subtype 2:
        *   monthday - on day [monthday] of the month
        *
        *  subtype 3:
        *   weekdays - bitmask of week days, where each bit is one weekday (weekdays & 1 = Sunday, weekdays & 2 = Monday, etc)
        *      nday    - on [nday]'th [weekdays] of the month [month]
        * @param string $rdata Binary string
        * @return array recurrence data.
        */
        function parseRecurrence($rdata)
        {
            if (strlen($rdata) < 10) {
                return;
            }

            $ret["changed_occurences"] = array();
            $ret["deleted_occurences"] = array();

            $data = unpack("Vconst1/Crtype/Cconst2/Vrtype2", $rdata);

            $ret["type"] = $data["rtype"];
            $ret["subtype"] = $data["rtype2"];
            $rdata = substr($rdata, 10);

            switch ($data["rtype"])
            {
                case 0x0a:
                    // Daily
                    if (strlen($rdata) < 12) {
                        return $ret;
                    }

                    $data = unpack("Vunknown/Veveryn/Vregen", $rdata);
                    $ret["everyn"] = $data["everyn"];
                    $ret["regen"] = $data["regen"];

                    switch($ret["subtype"])
                    {
                        case 0:
                            $rdata = substr($rdata, 12);
                            break;
                        case 1:
                            $rdata = substr($rdata, 16);
                            break;
                    }

                    break;

                case 0x0b:
                    // Weekly
                    if (strlen($rdata) < 16) {
                        return $ret;
                    }

                    $data = unpack("Vconst1/Veveryn/Vregen", $rdata);
                    $rdata = substr($rdata, 12);

                    $ret["everyn"] = $data["everyn"];
                    $ret["regen"] = $data["regen"];
                    $ret["weekdays"] = 0;

                    if ($data["regen"] == 0) {
                        $data = unpack("Vweekdays", $rdata);
                        $rdata = substr($rdata, 4);

                        $ret["weekdays"] = $data["weekdays"];
                    }
                    break;

                case 0x0c:
                    // Monthly
                    if (strlen($rdata) < 16) {
                        return $ret;
                    }

                    $data = unpack("Vconst1/Veveryn/Vregen/Vmonthday", $rdata);

                    $ret["everyn"] = $data["everyn"];
                    $ret["regen"] = $data["regen"];

                    if ($ret["subtype"] == 3) {
                        $ret["weekdays"] = $data["monthday"];
                    } else {
                        $ret["monthday"] = $data["monthday"];
                    }

                    $rdata = substr($rdata, 16);

                    if ($ret["subtype"] == 3) {
                        $data = unpack("Vnday", $rdata);
                        $ret["nday"] = $data["nday"];
                        $rdata = substr($rdata, 4);
                    }
                    break;

                case 0x0d:
                    // Yearly
                    if (strlen($rdata) < 16)
                        return $ret;

                    $data = unpack("Vmonth/Veveryn/Vregen/Vmonthday", $rdata);

                    $ret["month"] = $data["month"];
                    $ret["everyn"] = $data["everyn"];
                    $ret["regen"] = $data["regen"];

                    if ($ret["subtype"] == 3) {
                        $ret["weekdays"] = $data["monthday"];
                    } else {
                        $ret["monthday"] = $data["monthday"];
                    }

                    $rdata = substr($rdata, 16);

                    if ($ret["subtype"] == 3) {
                        $data = unpack("Vnday", $rdata);
                        $ret["nday"] = $data["nday"];
                        $rdata = substr($rdata, 4);
                    }
                    break;
            }

            if (strlen($rdata) < 16) {
                return $ret;
            }

            $data = unpack("Cterm/C3const1/Vnumoccur/Vconst2/Vnumexcept", $rdata);

            $rdata = substr($rdata, 16);

            $ret["term"] = $data["term"];
            $ret["numoccur"] = $data["numoccur"];
            $ret["numexcept"] = $data["numexcept"];

            // exc_base_dates are *all* the base dates that have been either deleted or modified
            $exc_base_dates = array();
            for($i = 0; $i < $ret["numexcept"]; $i++)
            {
                if (strlen($rdata) < 4) {
                    // We shouldn't arrive here, because that implies
                    // numexcept does not match the amount of data
                    // which is available for the exceptions.
                    return $ret;
                }
                $data = unpack("Vbasedate", $rdata);
                $rdata = substr($rdata, 4);
                $exc_base_dates[] = $this->recurDataToUnixData($data["basedate"]);
            }

            if (strlen($rdata) < 4) {
                return $ret;
            }

            $data = unpack("Vnumexceptmod", $rdata);
            $rdata = substr($rdata, 4);

            $ret["numexceptmod"] = $data["numexceptmod"];

            // exc_changed are the base dates of *modified* occurrences. exactly what is modified
            // is in the attachments *and* in the data further down this function.
            $exc_changed = array();
            for($i = 0; $i < $ret["numexceptmod"]; $i++)
            {
                if (strlen($rdata) < 4) {
                    // We shouldn't arrive here, because that implies
                    // numexceptmod does not match the amount of data
                    // which is available for the exceptions.
                    return $ret;
                }
                $data = unpack("Vstartdate", $rdata);
                $rdata = substr($rdata, 4);
                $exc_changed[] = $this->recurDataToUnixData($data["startdate"]);
            }

            if (strlen($rdata) < 8) {
                return $ret;
            }

            $data = unpack("Vstart/Vend", $rdata);
            $rdata = substr($rdata, 8);

            $ret["start"] = $this->recurDataToUnixData($data["start"]);
            $ret["end"] = $this->recurDataToUnixData($data["end"]);

            // this is where task recurrence stop
            if (strlen($rdata) < 16) {
                return $ret;
            }

            $data = unpack("Vreaderversion/Vwriterversion/Vstartmin/Vendmin", $rdata);
            $rdata = substr($rdata, 16);

            $ret["startocc"] = $data["startmin"];
            $ret["endocc"] = $data["endmin"];
            $readerversion = $data["readerversion"];
            $writerversion = $data["writerversion"];

            $data = unpack("vnumber", $rdata);
            $rdata = substr($rdata, 2);

            $nexceptions = $data["number"];
            $exc_changed_details = array();

            // Parse n modified exceptions
            for($i=0;$i<$nexceptions;$i++)
            {
                $item = array();

                // Get exception startdate, enddate and basedate (the date at which the occurrence would have started)
                $data = unpack("Vstartdate/Venddate/Vbasedate", $rdata);
                $rdata = substr($rdata, 12);

                // Convert recurtimestamp to unix timestamp
                $startdate = $this->recurDataToUnixData($data["startdate"]);
                $enddate = $this->recurDataToUnixData($data["enddate"]);
                $basedate = $this->recurDataToUnixData($data["basedate"]);

                // Set the right properties
                $item["basedate"] = $this->dayStartOf($basedate);
                $item["start"] = $startdate;
                $item["end"] = $enddate;

                $data = unpack("vbitmask", $rdata);
                $rdata = substr($rdata, 2);
                $item["bitmask"] = $data["bitmask"]; // save bitmask for extended exceptions

                // Bitmask to verify what properties are changed
                $bitmask = $data["bitmask"];

                // ARO_SUBJECT: 0x0001
                // Look for field: SubjectLength (2b), SubjectLength2 (2b) and Subject
                if(($bitmask &(1 << 0))) {
                    $data = unpack("vnull_length/vlength", $rdata);
                    $rdata = substr($rdata, 4);

                    $length = $data["length"];
                    $item["subject"] = ""; // Normalized subject
                    for($j = 0; $j < $length && strlen($rdata); $j++)
                    {
                        $data = unpack("Cchar", $rdata);
                        $rdata = substr($rdata, 1);

                        $item["subject"] .= chr($data["char"]);
                    }
                }

                // ARO_MEETINGTYPE: 0x0002
                if(($bitmask &(1 << 1))) {
                    $rdata = substr($rdata, 4);
                    // Attendees modified: no data here (only in attachment)
                }

                // ARO_REMINDERDELTA: 0x0004
                // Look for field: ReminderDelta (4b)
                if(($bitmask &(1 << 2))) {
                    $data = unpack("Vremind_before", $rdata);
                    $rdata = substr($rdata, 4);

                    $item["remind_before"] = $data["remind_before"];
                }

                // ARO_REMINDER: 0x0008
                // Look field: ReminderSet (4b)
                if(($bitmask &(1 << 3))) {
                    $data = unpack("Vreminder_set", $rdata);
                    $rdata = substr($rdata, 4);

                    $item["reminder_set"] = $data["reminder_set"];
                }

                // ARO_LOCATION: 0x0010
                // Look for fields: LocationLength (2b), LocationLength2 (2b) and Location
                // Similar to ARO_SUBJECT above.
                if(($bitmask &(1 << 4))) {
                    $data = unpack("vnull_length/vlength", $rdata);
                    $rdata = substr($rdata, 4);

                    $item["location"] = "";

                    $length = $data["length"];
                    $data = substr($rdata, 0, $length);
                    $rdata = substr($rdata, $length);

                    $item["location"] .= $data;
                }

                // ARO_BUSYSTATUS: 0x0020
                // Look for field: BusyStatus (4b)
                if(($bitmask &(1 << 5))) {
                    $data = unpack("Vbusystatus", $rdata);
                    $rdata = substr($rdata, 4);

                    $item["busystatus"] = $data["busystatus"];
                }

                // ARO_ATTACHMENT: 0x0040
                if(($bitmask &(1 << 6))) {
                    // no data: RESERVED
                    $rdata = substr($rdata, 4);
                }

                // ARO_SUBTYPE: 0x0080
                // Look for field: SubType (4b). Determines whether it is an allday event.
                if(($bitmask &(1 << 7))) {
                    $data = unpack("Vallday", $rdata);
                    $rdata = substr($rdata, 4);

                    $item["alldayevent"] = $data["allday"];
                }

                // ARO_APPTCOLOR: 0x0100
                // Look for field: AppointmentColor (4b)
                if(($bitmask &(1 << 8))) {
                    $data = unpack("Vlabel", $rdata);
                    $rdata = substr($rdata, 4);

                    $item["label"] = $data["label"];
                }

                // ARO_EXCEPTIONAL_BODY: 0x0200
                if(($bitmask &(1 << 9))) {
                    // Notes or Attachments modified: no data here (only in attachment)
                }

                array_push($exc_changed_details, $item);
            }

            /**
             * We now have $exc_changed, $exc_base_dates and $exc_changed_details
             * We will ignore $exc_changed, as this information is available in $exc_changed_details
             * also. If an item is in $exc_base_dates and NOT in $exc_changed_details, then the item
             * has been deleted.
             */

            // Find deleted occurrences
            $deleted_occurences = array();

            foreach($exc_base_dates as $base_date) {
                $found = false;

                foreach($exc_changed_details as $details) {
                    if($details["basedate"] == $base_date) {
                        $found = true;
                        break;
                    }
                }
                if(! $found) {
                    // item was not in exc_changed_details, so it must be deleted
                    $deleted_occurences[] = $base_date;
                }
            }

            $ret["deleted_occurences"] = $deleted_occurences;
            $ret["changed_occurences"] = $exc_changed_details;

            // enough data for normal exception (no extended data)
            if (strlen($rdata) < 16) {
                return $ret;
            }

            $data = unpack("Vreservedsize", $rdata);
            $rdata = substr($rdata, 4 + $data["reservedsize"]);

            for($i=0;$i<$nexceptions;$i++)
            {
                // subject and location in ucs-2 to utf-8
                if ($writerversion >= 0x3009) {
                    $data = unpack("Vsize/Vvalue", $rdata); // size includes sizeof(value)==4
                    $rdata = substr($rdata, 4 + $data["size"]);
                }

                $data = unpack("Vreservedsize", $rdata);
                $rdata = substr($rdata, 4 + $data["reservedsize"]);

                // ARO_SUBJECT(0x01) | ARO_LOCATION(0x10)
                if ($exc_changed_details[$i]["bitmask"] & 0x11) {
                    $data = unpack("Vstart/Vend/Vorig", $rdata);
                    $rdata = substr($rdata, 4 * 3);

                    $exc_changed_details[$i]["ex_start_datetime"] = $data["start"];
                    $exc_changed_details[$i]["ex_end_datetime"] = $data["end"];
                    $exc_changed_details[$i]["ex_orig_date"] = $data["orig"];
                }

                // ARO_SUBJECT
                if ($exc_changed_details[$i]["bitmask"] & 0x01) {
                    // decode ucs2 string to utf-8
                    $data = unpack("vlength", $rdata);
                    $rdata = substr($rdata, 2);
                    $length = $data["length"];
                    $data = substr($rdata, 0, $length * 2);
                    $rdata = substr($rdata, $length * 2);
                    $subject = iconv("UCS-2LE", "UTF-8", $data);
                    // replace subject with unicode subject
                    $exc_changed_details[$i]["subject"] = $subject;
                }

                // ARO_LOCATION
                if ($exc_changed_details[$i]["bitmask"] & 0x10) {
                    // decode ucs2 string to utf-8
                    $data = unpack("vlength", $rdata);
                    $rdata = substr($rdata, 2);
                    $length = $data["length"];
                    $data = substr($rdata, 0, $length * 2);
                    $rdata = substr($rdata, $length * 2);
                    $location = iconv("UCS-2LE", "UTF-8", $data);
                    // replace subject with unicode subject
                    $exc_changed_details[$i]["location"] = $location;
                }

                // ARO_SUBJECT(0x01) | ARO_LOCATION(0x10)
                if ($exc_changed_details[$i]["bitmask"] & 0x11) {
                    $data = unpack("Vreservedsize", $rdata);
                    $rdata = substr($rdata, 4 + $data["reservedsize"]);
                }
            }

            // update with extended data
            $ret["changed_occurences"] = $exc_changed_details;

            return $ret;
        }

        /**
         * Saves the recurrence data to the recurrence property
         * @param array $properties the recurrence data.
         * @return string binary string
         */
        function saveRecurrence()
        {
            // Only save if a message was passed
            if(!isset($this->message))
                return;

            // Abort if no recurrence was set
            if(!isset($this->recur["type"]) && !isset($this->recur["subtype"])) {
                return;
            }

            if(!isset($this->recur["start"]) && !isset($this->recur["end"])) {
                return;
            }

            if(!isset($this->recur["startocc"]) && !isset($this->recur["endocc"])) {
                return;
            }

            $rdata = pack("CCCCCCV", 0x04, 0x30, 0x04, 0x30, (int) $this->recur["type"], 0x20, (int) $this->recur["subtype"]);

            $weekstart = 1; //monday
            $forwardcount = 0;
            $restocc = 0;
            $dayofweek = (int) gmdate("w", (int) $this->recur["start"]); //0 (for Sunday) through 6 (for Saturday)

            $term = (int) $this->recur["type"];
            switch($term)
            {
                case 0x0A:
                    // Daily
                    if(!isset($this->recur["everyn"])) {
                        return;
                    }

                    if($this->recur["subtype"] == 1) {

                        // Daily every workday
                        $rdata .= pack("VVVV", (6 * 24 * 60), 1, 0, 0x3E);
                    } else {
                        // Daily every N days (everyN in minutes)

                        $everyn =  ((int) $this->recur["everyn"]) / 1440;

                        // Calc first occ
                        $firstocc = $this->unixDataToRecurData($this->recur["start"]) % ((int) $this->recur["everyn"]);

                        $rdata .= pack("VVV", $firstocc, (int) $this->recur["everyn"], $this->recur["regen"] ? 1 : 0);
                    }
                    break;
                case 0x0B:
                    // Weekly
                    if(!isset($this->recur["everyn"])) {
                        return;
                    }

                    if (!$this->recur["regen"] && !isset($this->recur["weekdays"])) {
                        return;
                    }

                    // No need to calculate startdate if sliding flag was set.
                    if (!$this->recur['regen']) {
                        // Calculate start date of recurrence

                        // Find the first day that matches one of the weekdays selected
                        $daycount = 0;
                        $dayskip = -1;
                        for($j = 0; $j < 7; $j++) {
                            if(((int) $this->recur["weekdays"]) & (1<<( ($dayofweek+$j)%7)) ) {
                                if($dayskip == -1)
                                    $dayskip = $j;

                                $daycount++;
                            }
                        }

                        // $dayskip is the number of days to skip from the startdate until the first occurrence
                        // $daycount is the number of days per week that an occurrence occurs

                        $weekskip = 0;
                        if(($dayofweek < $weekstart && $dayskip > 0) || ($dayofweek+$dayskip) > 6)
                            $weekskip = 1;

                        // Check if the recurrence ends after a number of occurences, in that case we must calculate the
                        // remaining occurences based on the start of the recurrence.
                        if (((int) $this->recur["term"]) == 0x22) {
                            // $weekskip is the amount of weeks to skip from the startdate before the first occurence
                            // $forwardcount is the maximum number of week occurrences we can go ahead after the first occurrence that
                            // is still inside the recurrence. We subtract one to make sure that the last week is never forwarded over
                            // (eg when numoccur = 2, and daycount = 1)
                            $forwardcount = floor( (int) ($this->recur["numoccur"] -1 ) / $daycount);

                            // $restocc is the number of occurrences left after $forwardcount whole weeks of occurrences, minus one
                            // for the occurrence on the first day
                            $restocc = ((int) $this->recur["numoccur"]) - ($forwardcount*$daycount) - 1;

                            // $forwardcount is now the number of weeks we can go forward and still be inside the recurrence
                            $forwardcount *= (int) $this->recur["everyn"];
                        }

                        // The real start is start + dayskip + weekskip-1 (since dayskip will already bring us into the next week)
                        $this->recur["start"] = ((int) $this->recur["start"]) + ($dayskip * 24*60*60)+ ($weekskip *(((int) $this->recur["everyn"]) - 1) * 7 * 24*60*60);
                    }

                    // Calc first occ
                    $firstocc = ($this->unixDataToRecurData($this->recur["start"]) ) % ( ((int) $this->recur["everyn"]) * 7 * 24 * 60);

                    $firstocc -= (((int) gmdate("w", (int) $this->recur["start"])) - 1) * 24 * 60;

                    if ($this->recur["regen"])
                        $rdata .= pack("VVV", $firstocc, (int) $this->recur["everyn"], 1);
                    else
                        $rdata .= pack("VVVV", $firstocc, (int) $this->recur["everyn"], 0, (int) $this->recur["weekdays"]);
                    break;
                case 0x0C:
                    // Monthly
                case 0x0D:
                    // Yearly
                    if(!isset($this->recur["everyn"])) {
                        return;
                    }
                    if($term == 0x0D /*yearly*/ && !isset($this->recur["month"])) {
                        return;
                    }

                    if($term == 0x0C /*monthly*/) {
                        $everyn = (int) $this->recur["everyn"];
                    }else {
                        $everyn = $this->recur["regen"] ? ((int) $this->recur["everyn"]) * 12 : 12;
                    }

                    // Get montday/month/year of original start
                    $curmonthday = gmdate("j", (int) $this->recur["start"] );
                    $curyear = gmdate("Y", (int) $this->recur["start"] );
                    $curmonth = gmdate("n", (int) $this->recur["start"] );

                    // Check if the recurrence ends after a number of occurences, in that case we must calculate the
                    // remaining occurences based on the start of the recurrence.
                    if (((int) $this->recur["term"]) == 0x22) {
                        // $forwardcount is the number of occurrences we can skip and still be inside the recurrence range (minus
                        // one to make sure there are always at least one occurrence left)
                        $forwardcount = ((((int) $this->recur["numoccur"])-1) * $everyn );
                    }

                    // Get month for yearly on D'th day of month M
                    if($term == 0x0D /*yearly*/) {
                        $selmonth = floor(((int) $this->recur["month"]) / (24 * 60 *29)) + 1; // 1=jan, 2=feb, eg
                    }

                    switch((int) $this->recur["subtype"])
                    {
                        // on D day of every M month
                        case 2:
                            if(!isset($this->recur["monthday"])) {
                                return;
                            }
                            // Recalc startdate

                            // Set on the right begin day

                            // Go the beginning of the month
                            $this->recur["start"] -= ($curmonthday-1) * 24*60*60;
                            // Go the the correct month day
                            $this->recur["start"] += (((int) $this->recur["monthday"])-1) * 24*60*60;

                            // If the previous calculation gave us a start date *before* the original start date, then we need to skip to the next occurrence
                            if ( ($term == 0x0C /*monthly*/ && ((int) $this->recur["monthday"]) < $curmonthday) ||
                                ($term == 0x0D /*yearly*/ &&( $selmonth < $curmonth || ($selmonth == $curmonth && ((int) $this->recur["monthday"]) < $curmonthday)) ))
                            {
                                if($term == 0x0D /*yearly*/)
                                    $count = ($everyn - ($curmonth - $selmonth)); // Yearly, go to next occurrence in 'everyn' months minus difference in first occurence and original date
                                else
                                    $count = $everyn; // Monthly, go to next occurrence in 'everyn' months

                                // Forward by $count months. This is done by getting the number of days in that month and forwarding that many days
                                for($i=0; $i < $count; $i++) {
                                    $this->recur["start"] += $this->getMonthInSeconds($curyear, $curmonth);

                                    if($curmonth == 12) {
                                        $curyear++;
                                        $curmonth = 0;
                                    }
                                    $curmonth++;
                                }
                            }

                            // "start" is now pointing to the first occurrence, except that it will overshoot if the
                            // month in which it occurs has less days than specified as the day of the month. So 31st
                            // of each month will overshoot in february (29 days). We compensate for that by checking
                            // if the day of the month we got is wrong, and then back up to the last day of the previous
                            // month.
                            if(((int) $this->recur["monthday"]) >=28 && ((int) $this->recur["monthday"]) <= 31 &&
                                gmdate("j", ((int) $this->recur["start"])) < ((int) $this->recur["monthday"]))
                            {
                                $this->recur["start"] -= gmdate("j", ((int) $this->recur["start"])) * 24 * 60 *60;
                            }

                            // "start" is now the first occurrence

                            if($term == 0x0C /*monthly*/) {
                                // Calc first occ
                                $monthIndex = ((((12%$everyn) * ((((int) gmdate("Y", $this->recur["start"])) - 1601)%$everyn)) % $everyn) + (((int) gmdate("n", $this->recur["start"])) - 1))%$everyn;

                                $firstocc = 0;
                                for($i=0; $i < $monthIndex; $i++) {
                                    $firstocc+= $this->getMonthInSeconds(1601 + floor($i/12), ($i%12)+1) / 60;
                                }

                                $rdata .= pack("VVVV", $firstocc, $everyn, $this->recur["regen"], (int) $this->recur["monthday"]);
                            } else{
                                // Calc first occ
                                $firstocc = 0;
                                $monthIndex = (int) gmdate("n", $this->recur["start"]);
                                for($i=1; $i < $monthIndex; $i++) {
                                    $firstocc+= $this->getMonthInSeconds(1601 + floor($i/12), $i) / 60;
                                }

                                $rdata .= pack("VVVV", $firstocc, $everyn, $this->recur["regen"], (int) $this->recur["monthday"]);
                            }
                            break;

                        case 3:
                            // monthly: on Nth weekday of every M month
                            // yearly: on Nth weekday of M month
                            if(!isset($this->recur["weekdays"]) && !isset($this->recur["nday"])) {
                                return;
                            }

                            $weekdays = (int) $this->recur["weekdays"];
                            $nday = (int) $this->recur["nday"];

                            // Calc startdate
                            $monthbegindow = (int) $this->recur["start"];

                            if($nday == 5) {
                                // Set date on the last day of the last month
                                $monthbegindow += (gmdate("t", $monthbegindow ) - gmdate("j", $monthbegindow )) * 24 * 60 * 60;
                            }else {
                                // Set on the first day of the month
                                $monthbegindow -= ((gmdate("j", $monthbegindow )-1) * 24 * 60 * 60);
                            }

                            if($term == 0x0D /*yearly*/) {
                                // Set on right month
                                if($selmonth < $curmonth)
                                    $tmp = 12 - $curmonth + $selmonth;
                                else
                                    $tmp = ($selmonth - $curmonth);

                                for($i=0; $i < $tmp; $i++) {
                                    $monthbegindow += $this->getMonthInSeconds($curyear, $curmonth);

                                    if($curmonth == 12) {
                                        $curyear++;
                                        $curmonth = 0;
                                    }
                                    $curmonth++;
                                }

                            }else {
                                // Check or you exist in the right month

                                for($i = 0; $i < 7; $i++) {
                                    if($nday == 5 && (1<<( (gmdate("w", $monthbegindow)-$i)%7) ) & $weekdays) {
                                        $day = gmdate("j", $monthbegindow) - $i;
                                        break;
                                    }else if($nday != 5 && (1<<( (gmdate("w", $monthbegindow )+$i)%7) ) & $weekdays) {
                                        $day = (($nday-1)*7) + ($i+1);
                                        break;
                                    }
                                }

                                // Goto the next X month
                                if(isset($day) && ($day < gmdate("j", (int) $this->recur["start"])) ) {
                                    if($nday == 5) {
                                        $monthbegindow += 24 * 60 * 60;
                                        if($curmonth == 12) {
                                            $curyear++;
                                            $curmonth = 0;
                                        }
                                        $curmonth++;
                                    }

                                    for($i=0; $i < $everyn; $i++) {
                                        $monthbegindow += $this->getMonthInSeconds($curyear, $curmonth);

                                        if($curmonth == 12) {
                                            $curyear++;
                                            $curmonth = 0;
                                        }
                                        $curmonth++;
                                    }

                                    if($nday == 5) {
                                        $monthbegindow -= 24 * 60 * 60;
                                    }
                                }
                            }

                            //FIXME: weekstart?

                            $day = 0;
                            // Set start on the right day
                            for($i = 0; $i < 7; $i++) {
                                if($nday == 5 && (1<<( (gmdate("w", $monthbegindow )-$i)%7) ) & $weekdays) {
                                    $day = $i;
                                    break;
                                }else if($nday != 5 && (1<<( (gmdate("w", $monthbegindow )+$i)%7) ) & $weekdays) {
                                    $day = ($nday - 1) * 7 + ($i+1);
                                    break;
                                }
                            }
                            if($nday == 5)
                                $monthbegindow -= $day * 24 * 60 *60;
                            else
                                $monthbegindow += ($day-1) * 24 * 60 *60;

                            $firstocc = 0;

                            if($term == 0x0C /*monthly*/) {
                                // Calc first occ
                                $monthIndex = ((((12%$everyn) * (((int) gmdate("Y", $this->recur["start"]) - 1601)%$everyn)) % $everyn) + (((int) gmdate("n", $this->recur["start"])) - 1))%$everyn;

                                for($i=0; $i < $monthIndex; $i++) {
                                    $firstocc+= $this->getMonthInSeconds(1601 + floor($i/12), ($i%12)+1) / 60;
                                }

                                $rdata .= pack("VVVVV", $firstocc, $everyn, 0, $weekdays, $nday);
                            } else {
                                // Calc first occ
                                $monthIndex = (int) gmdate("n", $this->recur["start"]);

                                for($i=1; $i < $monthIndex; $i++) {
                                    $firstocc+= $this->getMonthInSeconds(1601 + floor($i/12), $i) / 60;
                                }

                                $rdata .= pack("VVVVV", $firstocc, $everyn, 0, $weekdays, $nday);
                            }
                            break;
                    }
                    break;



            }

            if(!isset($this->recur["term"])) {
                return;
            }

            // Terminate
            $term = (int) $this->recur["term"];
            $rdata .= pack("CCCC", $term, 0x20, 0x00, 0x00);

            switch($term)
            {
                // After the given enddate
                case 0x21:
                    $rdata .= pack("V", 10);
                    break;
                // After a number of times
                case 0x22:
                    if(!isset($this->recur["numoccur"])) {
                        return;
                    }

                    $rdata .= pack("V", (int) $this->recur["numoccur"]);
                    break;
                // Never ends
                case 0x23:
                    $rdata .= pack("V", 0);
                    break;
            }

            // Strange little thing for the recurrence type "every workday"
            if(((int) $this->recur["type"]) == 0x0B && ((int) $this->recur["subtype"]) == 1) {
                $rdata .= pack("V", 1);
            } else { // Other recurrences
                $rdata .= pack("V", 0);
            }

            // Exception data

            // Get all exceptions
            $deleted_items = $this->recur["deleted_occurences"];
            $changed_items = $this->recur["changed_occurences"];

            // Merge deleted and changed items into one list
            $items = $deleted_items;

            foreach($changed_items as $changed_item)
                array_push($items, $changed_item["basedate"]);

            sort($items);

            // Add the merged list in to the rdata
            $rdata .= pack("V", count($items));
            foreach($items as $item)
                $rdata .= pack("V", $this->unixDataToRecurData($item));

            // Loop through the changed exceptions (not deleted)
            $rdata .= pack("V", count($changed_items));
            $items = array();

            foreach($changed_items as $changed_item)
            {
                $items[] = $this->dayStartOf($changed_item["start"]);
            }

            sort($items);

            // Add the changed items list int the rdata
            foreach($items as $item)
                $rdata .= pack("V", $this->unixDataToRecurData($item));

            // Set start date
            $rdata .= pack("V", $this->unixDataToRecurData((int) $this->recur["start"]));

            // Set enddate
            switch($term)
            {
                // After the given enddate
                case 0x21:
                    $rdata .= pack("V", $this->unixDataToRecurData((int) $this->recur["end"]));
                    break;
                // After a number of times
                case 0x22:
                    // @todo: calculate enddate with intval($this->recur["startocc"]) + intval($this->recur["duration"]) > 24 hour
                    $occenddate = (int) $this->recur["start"];

                    switch((int) $this->recur["type"]) {
                        case 0x0A: //daily

                            if($this->recur["subtype"] == 1) {
                                // Daily every workday
                                $restocc = (int) $this->recur["numoccur"];

                                // Get starting weekday
                                $nowtime = $this->gmtime($occenddate);
                                $j = $nowtime["tm_wday"];

                                while(1)
                                {
                                    if(($j%7) > 0 && ($j%7)<6 ) {
                                        $restocc--;
                                    }

                                    $j++;

                                    if($restocc <= 0)
                                        break;

                                    $occenddate += 24*60*60;
                                }

                            } else {
                                // -1 because the first day already counts (from 1-1-1980 to 1-1-1980 is 1 occurrence)
                                $occenddate += (((int) $this->recur["everyn"]) * 60 * (((int) $this->recur["numoccur"]-1)));
                            }
                            break;
                        case 0x0B: //weekly
                            // Needed values
                            // $forwardcount - number of weeks we can skip forward
                            // $restocc - number of remaning occurrences after the week skip

                            // Add the weeks till the last item
                            $occenddate+=($forwardcount*7*24*60*60);

                            $dayofweek = gmdate("w", $occenddate);

                            // Loop through the last occurrences until we have had them all
                            for($j = 1; $restocc>0; $j++)
                            {
                                // Jump to the next week (which may be N weeks away) when going over the week boundary
                                if((($dayofweek+$j)%7) == $weekstart)
                                    $occenddate += (((int) $this->recur["everyn"])-1) * 7 * 24*60*60;

                                // If this is a matching day, once less occurrence to process
                                if(((int) $this->recur["weekdays"]) & (1<<(($dayofweek+$j)%7)) ) {
                                    $restocc--;
                                }

                                // Next day
                                $occenddate += 24*60*60;
                            }

                            break;
                        case 0x0C: //monthly
                        case 0x0D: //yearly

                            $curyear = gmdate("Y", (int) $this->recur["start"] );
                            $curmonth = gmdate("n", (int) $this->recur["start"] );
                            // $forwardcount = months

                            switch((int) $this->recur["subtype"])
                            {
                                case 2: // on D day of every M month
                                    while($forwardcount > 0)
                                    {
                                        $occenddate += $this->getMonthInSeconds($curyear, $curmonth);

                                        if($curmonth >=12) {
                                            $curmonth = 1;
                                            $curyear++;
                                        } else {
                                            $curmonth++;
                                        }
                                        $forwardcount--;
                                    }

                                    // compensation between 28 and 31
                                    if(((int) $this->recur["monthday"]) >=28 && ((int) $this->recur["monthday"]) <= 31 &&
                                        gmdate("j", $occenddate) < ((int) $this->recur["monthday"]))
                                    {
                                        if(gmdate("j", $occenddate) < 28)
                                            $occenddate -= gmdate("j", $occenddate) * 24 * 60 *60;
                                        else
                                            $occenddate += (gmdate("t", $occenddate) - gmdate("j", $occenddate)) * 24 * 60 *60;
                                    }


                                    break;
                                case 3: // on Nth weekday of every M month
                                    $nday = (int) $this->recur["nday"]; //1 tot 5
                                    $weekdays = (int) $this->recur["weekdays"];


                                    while($forwardcount > 0)
                                    {
                                        $occenddate += $this->getMonthInSeconds($curyear, $curmonth);
                                        if($curmonth >=12) {
                                            $curmonth = 1;
                                            $curyear++;
                                        } else {
                                            $curmonth++;
                                        }

                                        $forwardcount--;
                                    }

                                    if($nday == 5) {
                                        // Set date on the last day of the last month
                                        $occenddate += (gmdate("t", $occenddate ) - gmdate("j", $occenddate )) * 24 * 60 * 60;
                                …