<?php
/*
 * Copyright 2005 - 2016  Zarafa B.V. and its licensors
 *
 * 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.
 *
 * 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/>.
 *
 * Consult LICENSE file for details
 */

    /**
     * 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 $properties the list of MAPI properties the message has.
         */
        function __construct($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"], $this->messageprops[$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"];
            $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"], $this->recur["subtype"], $this->recur["start"], $this->recur["end"], $this->recur["startocc"], $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 different than the original start date, then we need to skip to the first 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*/) {
                                    if ($curmonth > $selmonth) {//go to next occurrence in 'everyn' months minus difference in first occurrence and original date
                                        $count = $everyn - ($curmonth - $selmonth);
                                    } else if ($curmonth < $selmonth) {//go to next occurrence upto difference in first occurrence and original date
                                        $count = $selmonth - $curmonth;
                                    } else {
                                        // Go to next occurrence while recurrence start date is greater than occurrence date but within same month
                                        if (((int) $this->recur["monthday"]) < $curmonthday) {
                                            $count = $everyn;
                                        }
                                    }
                                } 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"], $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

                                $dayofweek = gmdate("w", $monthbegindow);
                                for($i = 0; $i < 7; $i++) {
                                    if($nday == 5 && (($dayofweek-$i)%7 >= 0) && (1<<( ($dayofweek-$i)%7) ) & $weekdays) {
                                        $day = gmdate("j", $monthbegindow) - $i;
                                        break;
                                    }else if($nday != 5 && (1<<( ($dayofweek+$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
                            $dayofweek = gmdate("w", $monthbegindow);
                            for($i = 0; $i < 7; $i++) {
                                if($nday == 5 && (($dayofweek-$i)%7) >= 0&& (1<<(($dayofweek-$i)%7) ) & $weekdays) {
                                    $day = $i;
                                    break;
                                }else if($nday != 5 && (1<<( ($dayofweek+$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;
                                    }else {
                                        // Set date on the first day of the last month
                                        $occenddate -= (gmdate("j", $occenddate )-1) * 24 * 60 * 60;
                                    }
                                    $dayofweek = gmdate("w", $occenddate);
                                    for($i = 0; $i < 7; $i++) {
                                        if($nday == 5 && (($dayofweek-$i)%7) >= 0&& (1<<(($dayofweek-$i)%7) ) & $weekdays) {
                                            $occenddate -= $i * 24 * 60 * 60;
                                            break;
                                        }else if($nday != 5 && (1<<(($dayofweek+$i)%7) ) & $weekdays) {
                                            $occenddate +=  ($i + (($nday-1) *7)) * 24 * 60 * 60;
                                            break;
                                        }
                                    }

                                break; //case 3:
                                }

                            break;

                    }

                    if (defined("PHP_INT_MAX") && $occenddate > PHP_INT_MAX)
                        $occenddate = PHP_INT_MAX;

                    $this->recur["end"] = $occenddate;

                    $rdata .= pack("V", $this->unixDataToRecurData((int) $this->recur["end"]) );
                    break;
                // Never ends
                case 0x23:
                default:
                    $this->recur["end"] = 0x7fffffff; // max date -> 2038
                    $rdata .= pack("V", 0x5AE980DF);
                    break;
            }

            // UTC date
            $utcstart = $this->toGMT($this->tz, (int) $this->recur["start"]);
            $utcend = $this->toGMT($this->tz, (int) $this->recur["end"]);

            //utc date+time
            $utcfirstoccstartdatetime = (isset($this->recur["startocc"])) ? $utcstart + (((int) $this->recur["startocc"])*60) : $utcstart;
            $utcfirstoccenddatetime = (isset($this->recur["endocc"])) ? $utcstart + (((int) $this->recur["endocc"]) * 60) : $utcstart;

            $propsToSet = array();
            // update reminder time
            $propsToSet[$this->proptags["reminder_time"]] = $utcfirstoccstartdatetime;

            // update first occurrence date
            $propsToSet[$this->proptags["startdate"]] = $propsToSet[$this->proptags["commonstart"]] = $utcfirstoccstartdatetime;
            $propsToSet[$this->proptags["duedate"]] = $propsToSet[$this->proptags["commonend"]] = $utcfirstoccenddatetime;

            // Set Outlook properties, if it is an appointment
            if (isset($this->messageprops[$this->proptags["message_class"]]) && $this->messageprops[$this->proptags["message_class"]] == "IPM.Appointment") {
                // update real begin and real end date
                $propsToSet[$this->proptags["startdate_recurring"]] = $utcstart;
                $propsToSet[$this->proptags["enddate_recurring"]] = $utcend;

                // recurrencetype
                // Strange enough is the property recurrencetype, (type-0x9) and not the CDO recurrencetype
                $propsToSet[$this->proptags["recurrencetype"]] = ((int) $this->recur["type"]) - 0x9;

                // set named prop 'side_effects' to 369, needed for Outlook to ask for single or total recurrence when deleting
                $propsToSet[$this->proptags["side_effects"]] = 369;
            } else {
                $propsToSet[$this->proptags["side_effects"]] = 3441;
            }

            // FlagDueBy is datetime of the first reminder occurrence. Outlook gives on this time a reminder popup dialog
            // Any change of the recurrence (including changing and deleting exceptions) causes the flagdueby to be reset
            // to the 'next' occurrence; this makes sure that deleting the next ocurrence will correctly set the reminder to
            // the occurrence after that. The 'next' occurrence is defined as being the first occurrence that starts at moment X (server time)
            // with the reminder flag set.
            $reminderprops = mapi_getprops($this->message, array($this->proptags["reminder_minutes"]) );
            if(isset($reminderprops[$this->proptags["reminder_minutes"]]) ) {
                $occ = false;
                $occurrences = $this->getItems(time(), 0x7ff00000, 3, true);

                for($i = 0, $len = count($occurrences) ; $i < $len; $i++) {
                    // This will actually also give us appointments that have already started, but not yet ended. Since we want the next
                    // reminder that occurs after time(), we may have to skip the first few entries. We get 3 entries since that is the maximum
                    // number that would be needed (assuming reminder for item X cannot be before the previous occurrence starts). Worst case:
                    // time() is currently after start but before end of item, but reminder of next item has already passed (reminder for next item
                    // can be DURING the previous item, eg daily allday events). In that case, the first and second items must be skipped.

                    if(($occurrences[$i][$this->proptags["startdate"]] - $reminderprops[$this->proptags["reminder_minutes"]] * 60) > time()) {
                        $occ = $occurrences[$i];
                        break;
                    }
                }

                if($occ) {
                    $propsToSet[$this->proptags["flagdueby"]] = $occ[$this->proptags["startdate"]] - ($reminderprops[$this->proptags["reminder_minutes"]] * 60);
                } else {
                    // Last reminder passed, no reminders any more.
                    $propsToSet[$this->proptags["reminder"]] = false;
                    $propsToSet[$this->proptags["flagdueby"]] = 0x7ff00000;
                }
            }

            // Default data
            // Second item (0x08) indicates the Outlook version (see documentation at the bottom of this file for more information)
            $rdata .= pack("VCCCC", 0x00003006, 0x08, 0x30, 0x00, 0x00);

            if(isset($this->recur["startocc"], $this->recur["endocc"])) {
                // Set start and endtime in minutes
                $rdata .= pack("VV", (int) $this->recur["startocc"], (int) $this->recur["endocc"]);
            }

            // Detailed exception data

            $changed_items = $this->recur["changed_occurences"];

            $rdata .= pack("v", count($changed_items));

            foreach($changed_items as $changed_item)
            {
                // Set start and end time of exception
                $rdata .= pack("V", $this->unixDataToRecurData($changed_item["start"]));
                $rdata .= pack("V", $this->unixDataToRecurData($changed_item["end"]));
                $rdata .= pack("V", $this->unixDataToRecurData($changed_item["basedate"]));

                //Bitmask
                $bitmask = 0;

                // Check for changed strings
                if(isset($changed_item["subject"]))    {
                    $bitmask |= 1 << 0;
                }

                if(isset($changed_item["remind_before"])) {
                    $bitmask |= 1 << 2;
                }

                if(isset($changed_item["reminder_set"])) {
                    $bitmask |= 1 << 3;
                }

                if(isset($changed_item["location"])) {
                    $bitmask |= 1 << 4;
                }

                if(isset($changed_item["busystatus"])) {
                    $bitmask |= 1 << 5;
                }

                if(isset($changed_item["alldayevent"])) {
                    $bitmask |= 1 << 7;
                }

                if(isset($changed_item["label"])) {
                    $bitmask |= 1 << 8;
                }

                $rdata .= pack("v", $bitmask);

                // Set "subject"
                if(isset($changed_item["subject"])) {
                    // convert utf-8 to non-unicode blob string (us-ascii?)
                    $subject = iconv("UTF-8", "windows-1252//TRANSLIT", $changed_item["subject"]);
                    $length = strlen($subject);
                    $rdata .= pack("vv", $length + 1, $length);
                    $rdata .= pack("a".$length, $subject);
                }

                if(isset($changed_item["remind_before"])) {
                    $rdata .= pack("V", $changed_item["remind_before"]);
                }

                if(isset($changed_item["reminder_set"])) {
                    $rdata .= pack("V", $changed_item["reminder_set"]);
                }

                if(isset($changed_item["location"])) {
                    $location = iconv("UTF-8", "windows-1252//TRANSLIT", $changed_item["location"]);
                    $length = strlen($location);
                    $rdata .= pack("vv", $length + 1, $length);
                    $rdata .= pack("a".$length, $location);
                }

                if(isset($changed_item["busystatus"])) {
                    $rdata .= pack("V", $changed_item["busystatus"]);
                }

                if(isset($changed_item["alldayevent"])) {
                    $rdata .= pack("V", $changed_item["alldayevent"]);
                }

                if(isset($changed_item["label"])) {
                    $rdata .= pack("V", $changed_item["label"]);
                }
            }

            $rdata .= pack("V", 0);

            // write extended data
            foreach($changed_items as $changed_item)
            {
                $rdata .= pack("V", 0);
                if(isset($changed_item["subject"]) || isset($changed_item["location"])) {
                    $rdata .= pack("V", $this->unixDataToRecurData($changed_item["start"]));
                    $rdata .= pack("V", $this->unixDataToRecurData($changed_item["end"]));
                    $rdata .= pack("V", $this->unixDataToRecurData($changed_item["basedate"]));
                }

                if(isset($changed_item["subject"])) {
                    $subject = iconv("UTF-8", "UCS-2LE", $changed_item["subject"]);
                    $length = iconv_strlen($subject, "UCS-2LE");
                    $rdata .= pack("v", $length);
                    $rdata .= pack("a".$length*2, $subject);
                }

                if(isset($changed_item["location"])) {
                    $location = iconv("UTF-8", "UCS-2LE", $changed_item["location"]);
                    $length = iconv_strlen($location, "UCS-2LE");
                    $rdata .= pack("v", $length);
                    $rdata .= pack("a".$length*2, $location);
                }

                if(isset($changed_item["subject"]) || isset($changed_item["location"])) {
                    $rdata .= pack("V", 0);
                }
            }

            $rdata .= pack("V", 0);

            // Set props
            $propsToSet[$this->proptags["recurring_data"]] = $rdata;
            $propsToSet[$this->proptags["recurring"]] = true;

            if(isset($this->tz) && $this->tz){
                $timezone = "GMT";
                if($this->tz["timezone"]!=0){
                    // Create user readable timezone information
                    $timezone = sprintf("(GMT %s%02d:%02d)",    (-$this->tz["timezone"]>0 ? "+" : "-"),
                                                            abs($this->tz["timezone"]/60),
                                                            abs($this->tz["timezone"]%60));
                }
                $propsToSet[$this->proptags["timezone_data"]] = $this->getTimezoneData($this->tz);
                $propsToSet[$this->proptags["timezone"]] = $timezone;
            }
            mapi_setprops($this->message, $propsToSet);
        }

        /**
        * Function which converts a recurrence date timestamp to an unix date timestamp.
        * @author Steve Hardy
        * @param Int $rdate the date which will be converted
        * @return Int the converted date
        */
        function recurDataToUnixData($rdate)
        {
            return ($rdate - 194074560) * 60 ;
        }

        /**
        * Function which converts an unix date timestamp to recurrence date timestamp.
        * @author Johnny Biemans
        * @param Date $date the date which will be converted
        * @return Int the converted date in minutes
        */
        function unixDataToRecurData($date)
        {
            return ($date / 60) + 194074560;
        }

        /**
        * gmtime() doesn't exist in standard PHP, so we have to implement it ourselves
        * @author Steve Hardy
        */
        function GetTZOffset($ts)
        {
            $Offset = date("O", $ts);

            $Parity = $Offset < 0 ? -1 : 1;
            $Offset = $Parity * $Offset;
            $Offset = ($Offset - ($Offset % 100)) / 100 * 60 + $Offset % 100;

            return $Parity * $Offset;
        }

        /**
        * gmtime() doesn't exist in standard PHP, so we have to implement it ourselves
        * @author Steve Hardy
        * @param Date $time
        * @return Date GMT Time
        */
        function gmtime($time)
        {
            $TZOffset = $this->GetTZOffset($time);

            $t_time = $time - $TZOffset * 60; #Counter adjust for localtime()
            $t_arr = localtime($t_time, 1);

            return $t_arr;
        }

        function isLeapYear($year) {
            return ( $year % 4 == 0 && ($year % 100 != 0 || $year % 400 == 0) );
        }

        function getMonthInSeconds($year, $month)
        {
            if( in_array($month, array(1,3,5,7,8,10,12) ) ) {
                $day = 31;
            } else if( in_array($month, array(4,6,9,11) ) ) {
                $day = 30;
            } else {
                $day = 28;
                if( $this->isLeapYear($year) == 1 )
                    $day++;
            }
            return $day * 24 * 60 * 60;
        }

        /**
         * Function to get a date by Year Nr, Month Nr, Week Nr, Day Nr, and hour
         * @param int $year
         * @param int $month
         * @param int $week
         * @param int $day
         * @param int $hour
         * @return returns the timestamp of the given date, timezone-independant
         */
        function getDateByYearMonthWeekDayHour($year, $month, $week, $day, $hour)
        {
            // get first day of month
            $date = gmmktime(0,0,0,$month,0,$year + 1900);

            // get wday info
            $gmdate = $this->gmtime($date);

            $date -= $gmdate["tm_wday"] * 24 * 60 * 60; // back up to start of week

            $date += $week * 7 * 24 * 60 * 60; // go to correct week nr
            $date += $day * 24 * 60 * 60;
            $date += $hour * 60 * 60;

            $gmdate = $this->gmtime($date);

            // if we are in the next month, then back up a week, because week '5' means
            // 'last week of month'

            if($gmdate["tm_mon"]+1 != $month)
                $date -= 7 * 24 * 60 * 60;

            return $date;
        }

        /**
         * getTimezone gives the timezone offset (in minutes) of the given
         * local date/time according to the given TZ info
         */
        function getTimezone($tz, $date)
        {
            // No timezone -> GMT (+0)
            if(!isset($tz["timezone"]))
                return 0;

            $dst = false;
            $gmdate = $this->gmtime($date);

            $dststart = $this->getDateByYearMonthWeekDayHour($gmdate["tm_year"], $tz["dststartmonth"], $tz["dststartweek"], 0, $tz["dststarthour"]);
            $dstend = $this->getDateByYearMonthWeekDayHour($gmdate["tm_year"], $tz["dstendmonth"], $tz["dstendweek"], 0, $tz["dstendhour"]);

            if($dststart <= $dstend) {
                // Northern hemisphere, eg DST is during Mar-Oct
                if($date > $dststart && $date < $dstend) {
                    $dst = true;
                }
            } else {
                // Southern hemisphere, eg DST is during Oct-Mar
                if($date < $dstend || $date > $dststart) {
                    $dst = true;
                }
            }

            if($dst) {
                return $tz["timezone"] + $tz["timezonedst"];
            } else {
                return $tz["timezone"];
            }
        }

        /**
         * getWeekNr() returns the week nr of the month (ie first week of february is 1)
         */
        function getWeekNr($date)
        {
            $gmdate = gmtime($date);
            $gmdate["tm_mday"] = 0;
            return strftime("%W", $date) - strftime("%W", gmmktime($gmdate)) + 1;
        }

        /**
         * parseTimezone parses the timezone as specified in named property 0x8233
         * in Outlook calendar messages. Returns the timezone in minutes negative
         * offset (GMT +2:00 -> -120)
         */
        function parseTimezone($data)
        {
            if(strlen($data) < 48)
                return;

            $tz = unpack("ltimezone/lunk/ltimezonedst/lunk/ldstendmonth/vdstendweek/vdstendhour/lunk/lunk/vunk/ldststartmonth/vdststartweek/vdststarthour/lunk/vunk", $data);
            return $tz;
        }

        function getTimezoneData($tz)
        {
            $data = pack("lllllvvllvlvvlv", $tz["timezone"], 0, $tz["timezonedst"], 0, $tz["dstendmonth"], $tz["dstendweek"], $tz["dstendhour"], 0, 0, 0, $tz["dststartmonth"], $tz["dststartweek"], $tz["dststarthour"], 0 ,0);

            return $data;
        }

        /**
         * createTimezone creates the timezone as specified in the named property 0x8233
         * see also parseTimezone()
         * $tz is an array with the timezone data
         */
        function createTimezone($tz)
        {
            $data = pack("lxxxxlxxxxlvvxxxxxxxxxxlvvxxxxxx",
                        $tz["timezone"],
                        array_key_exists("timezonedst",$tz)?$tz["timezonedst"]:0,
                        array_key_exists("dstendmonth",$tz)?$tz["dstendmonth"]:0,
                        array_key_exists("dstendweek",$tz)?$tz["dstendweek"]:0,
                        array_key_exists("dstendhour",$tz)?$tz["dstendhour"]:0,
                        array_key_exists("dststartmonth",$tz)?$tz["dststartmonth"]:0,
                        array_key_exists("dststartweek",$tz)?$tz["dststartweek"]:0,
                        array_key_exists("dststarthour",$tz)?$tz["dststarthour"]:0
                    );

            return $data;
        }

        /**
         * toGMT returns a timestamp in GMT time for the time and timezone given
         */
        function toGMT($tz, $date) {
            if(!isset($tz['timezone']))
                return $date;
            $offset = $this->getTimezone($tz, $date);

            return $date + $offset * 60;
        }

        /**
         * fromGMT returns a timestamp in the local timezone given from the GMT time given
         */
        function fromGMT($tz, $date) {
            $offset = $this->getTimezone($tz, $date);

            return $date - $offset * 60;
        }

        /**
         * Function to get timestamp of the beginning of the day of the timestamp given
         * @param date $date
         * @return date timestamp referring to same day but at 00:00:00
         */
        function dayStartOf($date)
        {
            $time1 = $this->gmtime($date);

            return gmmktime(0, 0, 0, $time1["tm_mon"] + 1, $time1["tm_mday"], $time1["tm_year"] + 1900);
        }

        /**
         * Function to get timestamp of the beginning of the month of the timestamp given
         * @param date $date
         * @return date Timestamp referring to same month but on the first day, and at 00:00:00
         */
        function monthStartOf($date)
        {
            $time1 = $this->gmtime($date);

            return gmmktime(0, 0, 0, $time1["tm_mon"] + 1, 1, $time1["tm_year"] + 1900);
        }

        /**
         * Function to get timestamp of the beginning of the year of the timestamp given
         * @param date $date
         * @return date Timestamp referring to the same year but on Jan 01, at 00:00:00
         */
        function yearStartOf($date)
        {
            $time1 = $this->gmtime($date);

            return gmmktime(0, 0, 0, 1, 1, $time1["tm_year"] + 1900);
        }


        /**
         * Function which returns the items in a given interval. This included expansion of the recurrence and
         * processing of exceptions (modified and deleted).
         *
         * @param string $entryid the entryid of the message
         * @param array $props the properties of the message
         * @param date $start start time of the interval (GMT)
         * @param date $end end time of the interval (GMT)
         */
        function getItems($start, $end, $limit = 0, $remindersonly = false)
        {
            $items = array();

            if(isset($this->recur)) {

                // Optimization: remindersonly and default reminder is off; since only exceptions with reminder set will match, just look which
                // exceptions are in range and have a reminder set
                if($remindersonly && (!isset($this->messageprops[$this->proptags["reminder"]]) || $this->messageprops[$this->proptags["reminder"]] == false)) {
                    // Sort exceptions by start time
                    uasort($this->recur["changed_occurences"], array($this, "sortExceptionStart"));

                    // Loop through all changed exceptions
                    foreach($this->recur["changed_occurences"] as $exception) {
                        // Check reminder set
                        if(!isset($exception["reminder"]) || $exception["reminder"] == false)
                            continue;

                        // Convert to GMT
                        $occstart = $this->toGMT($this->tz, $exception["start"]); // seb changed $tz to $this->tz
                        $occend = $this->toGMT($this->tz, $exception["end"]); // seb changed $tz to $this->tz

                        // Check range criterium
                        if($occstart > $end || $occend < $start)
                            continue;

                        // OK, add to items.
                        array_push($items, $this->getExceptionProperties($exception));
                        if($limit && (count($items) == $limit))
                            break;
                    }

                    uasort($items, array($this, "sortStarttime"));

                    return $items;
                }

                // From here on, the dates of the occurrences are calculated in local time, so the days we're looking
                // at are calculated from the local time dates of $start and $end
                // TODO use one isset
                if(isset($this->recur['regen'], $this->action['datecompleted']) && $this->recur['regen']) {
                    $daystart = $this->dayStartOf($this->action['datecompleted']);
                } else {
                    $daystart = $this->dayStartOf($this->recur["start"]); // start on first day of occurrence
                }

                // Calculate the last day on which we want to be looking at a recurrence; this is either the end of the view
                // or the end of the recurrence, whichever comes first
                if($end > $this->toGMT($this->tz, $this->recur["end"])) {
                    $rangeend = $this->toGMT($this->tz, $this->recur["end"]);
                } else {
                    $rangeend = $end;
                }

                $dayend = $this->dayStartOf($this->fromGMT($this->tz, $rangeend));

                // Loop through the entire recurrence range of dates, and check for each occurrence whether it is in the view range.

                switch($this->recur["type"])
                {
                case 10:
                    // Daily
                    if($this->recur["everyn"] <= 0)
                        $this->recur["everyn"] = 1440;

                    if($this->recur["subtype"] == 0) {
                        // Every Nth day
                        for($now = $daystart; $now <= $dayend && ($limit == 0 || count($items) < $limit); $now += 60 * $this->recur["everyn"]) {
                            $this->processOccurrenceItem($items, $start, $end, $now, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                        }
                    } else {
                        // Every workday
                        for($now = $daystart; $now <= $dayend && ($limit == 0 || count($items) < $limit); $now += 60 * 1440)
                        {
                            $nowtime = $this->gmtime($now);
                            if ($nowtime["tm_wday"] > 0 && $nowtime["tm_wday"] < 6) { // only add items in the given timespace
                                $this->processOccurrenceItem($items, $start, $end, $now, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                            }
                        }
                    }
                    break;
                case 11:
                    // Weekly
                    if($this->recur["everyn"] <= 0)
                        $this->recur["everyn"] = 1;

                    // If sliding flag is set then move to 'n' weeks
                    if ($this->recur['regen']) $daystart += (60 * 60 * 24 * 7 * $this->recur["everyn"]);

                    for($now = $daystart; $now <= $dayend && ($limit == 0 || count($items) < $limit); $now += (60 * 60 * 24 * 7 * $this->recur["everyn"]))
                    {
                        if ($this->recur['regen']) {
                            $this->processOccurrenceItem($items, $start, $end, $now, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                        } else {
                            // Loop through the whole following week to the first occurrence of the week, add each day that is specified
                            for($wday = 0; $wday < 7; $wday++)
                            {
                                $daynow = $now + $wday * 60 * 60 * 24;
                                //checks weather the next coming day in recurring pattern is less than or equal to end day of the recurring item
                                if ($daynow <= $dayend){
                                    $nowtime = $this->gmtime($daynow); // Get the weekday of the current day
                                    if(($this->recur["weekdays"] &(1 << $nowtime["tm_wday"]))) { // Selected ?
                                        $this->processOccurrenceItem($items, $start, $end, $daynow, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                                    }
                                }
                            }
                        }
                    }
                    break;
                case 12:
                    // Monthly
                    if($this->recur["everyn"] <= 0)
                        $this->recur["everyn"] = 1;

                    // Loop through all months from start to end of occurrence, starting at beginning of first month
                    for($now = $this->monthStartOf($daystart); $now <= $dayend && ($limit == 0 || count($items) < $limit); $now += $this->daysInMonth($now, $this->recur["everyn"]) * 24 * 60 * 60 )
                    {
                        if(isset($this->recur["monthday"]) &&($this->recur['monthday'] != "undefined") && !$this->recur['regen']) { // Day M of every N months
                            $difference = 1;
                            if ($this->daysInMonth($now, $this->recur["everyn"]) < $this->recur["monthday"]) {
                                $difference = $this->recur["monthday"] - $this->daysInMonth($now, $this->recur["everyn"]) + 1;
                            }
                            $daynow = $now + (($this->recur["monthday"] - $difference) * 24 * 60 * 60);
                            //checks weather the next coming day in recurrence pattern is less than or equal to end day of the recurring item
                            if ($daynow <= $dayend){
                                $this->processOccurrenceItem($items, $start, $end, $daynow, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                            }
                        }
                        else if(isset($this->recur["nday"], $this->recur["weekdays"])) { // Nth [weekday] of every N months
                            // Sanitize input
                            if($this->recur["weekdays"] == 0)
                                $this->recur["weekdays"] = 1;

                            // If nday is not set to the last day in the month
                            if ($this->recur["nday"] < 5) {
                                // keep the track of no. of time correct selection pattern(like 2nd weekday, 4th fiday, etc.)is matched
                                $ndaycounter = 0;
                                // Find matching weekday in this month
                                for($day = 0, $total = $this->daysInMonth($now, 1); $day < $total; $day++)
                                {
                                    $daynow = $now + $day * 60 * 60 * 24;
                                    $nowtime = $this->gmtime($daynow); // Get the weekday of the current day

                                    if($this->recur["weekdays"] & (1 << $nowtime["tm_wday"])) { // Selected ?
                                        $ndaycounter ++;
                                    }
                                    // check the selected pattern is same as asked Nth weekday,If so set the firstday
                                    if($this->recur["nday"] == $ndaycounter){
                                        $firstday = $day;
                                        break;
                                    }
                                }
                                // $firstday is the day of the month on which the asked pattern of nth weekday matches
                                $daynow = $now + $firstday * 60 * 60 * 24;
                            }else{
                                // Find last day in the month ($now is the firstday of the month)
                                $NumDaysInMonth =  $this->daysInMonth($now, 1);
                                $daynow = $now + (($NumDaysInMonth-1) * 24*60*60);

                                $nowtime = $this->gmtime($daynow);
                                while (($this->recur["weekdays"] & (1 << $nowtime["tm_wday"]))==0){
                                    $daynow -= 86400;
                                    $nowtime = $this->gmtime($daynow);
                                }
                            }

                            /**
                             * checks weather the next coming day in recurrence pattern is less than or equal to end day of the            * recurring item.Also check weather the coming day in recurrence pattern is greater than or equal to start * of recurring pattern, so that appointment that fall under the recurrence range are only displayed.
                             */
                            if ($daynow <= $dayend && $daynow >= $daystart){
                                $this->processOccurrenceItem($items, $start, $end, $daynow, $this->recur["startocc"], $this->recur["endocc"], $this->tz , $remindersonly);
                            }
                        } else if ($this->recur['regen']) {
                            $next_month_start = $now + ($this->daysInMonth($now, 1) * 24 * 60 * 60);
                            $now = $daystart +($this->daysInMonth($next_month_start, $this->recur['everyn']) * 24 * 60 * 60);

                            if ($now <= $dayend) {
                                $this->processOccurrenceItem($items, $daystart, $end, $now, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                            }
                        }
                    }
                    break;
                case 13:
                    // Yearly
                    if($this->recur["everyn"] <= 0)
                        $this->recur["everyn"] = 12;

                    for($now = $this->yearStartOf($daystart); $now <= $dayend && ($limit == 0 || count($items) < $limit); $now += $this->daysInMonth($now, $this->recur["everyn"]) * 24 * 60 * 60 )
                    {
                        if(isset($this->recur["monthday"]) && !$this->recur['regen']) { // same as monthly, but in a specific month
                            // recur["month"] is in minutes since the beginning of the year
                            $month = $this->monthOfYear($this->recur["month"]); // $month is now month of year [0..11]
                            $monthday = $this->recur["monthday"]; // $monthday is day of the month [1..31]
                            $monthstart = $now + $this->daysInMonth($now, $month) * 24 * 60 * 60; // $monthstart is the timestamp of the beginning of the month
                            if($monthday > $this->daysInMonth($monthstart, 1))
                                $monthday = $this->daysInMonth($monthstart, 1);    // Cap $monthday on month length (eg 28 feb instead of 29 feb)
                            $daynow = $monthstart + ($monthday-1) * 24 * 60 * 60;
                            $this->processOccurrenceItem($items, $start, $end, $daynow, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                        }
                        else if(isset($this->recur["nday"], $this->recur["weekdays"])) { // Nth [weekday] in month X of every N years

                            // Go the correct month
                            $monthnow = $now + $this->daysInMonth($now, $this->monthOfYear($this->recur["month"])) * 24 * 60 * 60;

                            // Find first matching weekday in this month
                            for($wday = 0; $wday < 7; $wday++)
                            {
                                $daynow = $monthnow + $wday * 60 * 60 * 24;
                                $nowtime = $this->gmtime($daynow); // Get the weekday of the current day

                                if($this->recur["weekdays"] & (1 << $nowtime["tm_wday"])) { // Selected ?
                                    $firstday = $wday;
                                    break;
                                }
                            }

                            // Same as above (monthly)
                            $daynow = $monthnow + ($firstday + ($this->recur["nday"]-1)*7) * 60 * 60 * 24;

                            while($this->monthStartOf($daynow) != $this->monthStartOf($monthnow)) {
                                $daynow -= 7 * 60 * 60 * 24;
                            }

                            $this->processOccurrenceItem($items, $start, $end, $daynow, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                        } else if ($this->recur['regen']) {
                            $year_starttime = $this->gmtime($now);
                            $is_next_leapyear = $this->isLeapYear($year_starttime['tm_year'] + 1900 + 1);    // +1 next year
                            $now = $daystart + ($is_next_leapyear ? 31622400 /* Leap year in seconds */ : 31536000 /*year in seconds*/);

                            if ($now <= $dayend) {
                                $this->processOccurrenceItem($items, $daystart, $end, $now, $this->recur["startocc"], $this->recur["endocc"], $this->tz, $remindersonly);
                            }
                        }
                    }
                }
                //to get all exception items
                if (!empty($this->recur['changed_occurences']))
                    $this->processExceptionItems($items, $start, $end);
            }

            // sort items on starttime
            usort($items, array($this, "sortStarttime"));

            // Return the MAPI-compatible list of items for this object
            return $items;
        }

        function sortStarttime($a, $b)
        {
            $aTime = $a[$this->proptags["startdate"]];
            $bTime = $b[$this->proptags["startdate"]];

            return $aTime==$bTime?0:($aTime>$bTime?1:-1);
        }

        /**
         * daysInMonth
         *
         * Returns the number of days in the upcoming number of months. If you specify 1 month as
         * $months it will give you the number of days in the month of $date. If you specify more it
         * will also count the days in the upcomming months and add that to the number of days. So
         * if you have a date in march and you specify $months as 2 it will return 61.
         * @param Integer $date Specified date as timestamp from which you want to know the number
         * of days in the month.
         * @param Integer $months Number of months you want to know the number of days in.
         * @returns Integer Number of days in the specified amount of months.
         */
        function daysInMonth($date, $months) {
            $days = 0;

            for($i=0;$i<$months;$i++) {
                $days += date("t", $date + $days * 24 * 60 * 60);
            }

            return $days;
        }

        // Converts MAPI-style 'minutes' into the month of the year [0..11]
        function monthOfYear($minutes) {
            $d = gmmktime(0,0,0,1,1,2001); // The year 2001 was a non-leap year, and the minutes provided are always in non-leap-year-minutes

            $d += $minutes*60;

            $dtime = $this->gmtime($d);

            return $dtime["tm_mon"];
        }

        function sortExceptionStart($a, $b)
        {
            return $a["start"] == $b["start"] ? 0 : ($a["start"]  > $b["start"] ? 1 : -1 );
        }
    }
