<?php
/**
 * iCalcreator, the PHP class package managing iCal (rfc2445/rfc5445) calendar information.
 *
 * copyright (c) 2007-2019 Kjell-Inge Gustafsson, kigkonsult, All rights reserved
 * Link      https://kigkonsult.se
 * Package   iCalcreator
 * Version   2.26.8
 * License   Subject matter of licence is the software iCalcreator.
 *           The above copyright, link, package and version notices,
 *           this licence notice and the invariant [rfc5545] PRODID result use
 *           as implemented and invoked in iCalcreator shall be included in
 *           all copies or substantial portions of the iCalcreator.
 *
 *           iCalcreator is free software: you can redistribute it and/or modify
 *           it under the terms of the GNU Lesser General Public License as published
 *           by the Free Software Foundation, either version 3 of the License,
 *           or (at your option) any later version.
 *
 *           iCalcreator 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 Lesser General Public License for more details.
 *
 *           You should have received a copy of the GNU Lesser General Public License
 *           along with iCalcreator. If not, see <https://www.gnu.org/licenses/>.
 *
 * This file is a part of iCalcreator.
*/

/**
 * Additional functions to use with Vtimezone components
 *
 * Before calling the functions, set time zone 'GMT' ('date_default_timezone_set')!
 *
 * @author  Yitzchok Lavi <icalcreator@onebigsystem.com>
 *         adjusted for iCalcreator Kjell-Inge Gustafsson, kigkonsult <ical@kigkonsult.se>
 * @version 1.0.2 - 2011-02-24
 */

namespace Kigkonsult\Icalcreator;

use Kigkonsult\Icalcreator\Util\Util;

use function array_merge;
use function count;
use function explode;
use function getdate;
use function is_array;
use function mktime;
use function sort;
use function sprintf;
use function strtotime;
use function substr;
use function time;

/**
 * Returns array with the offset information
 *
 * From UTC for a (UTC) datetime/timestamp in the
 * timezone, according to the VTIMEZONE information in the input array.
 *
 * @param array  $timezonesarray output from function getTimezonesAsDateArrays (below)
 * @param string $tzid           time zone identifier
 * @param mixed  $timestamp      timestamp or a UTC datetime (in array format)
 * @return array                  time zone data with keys for $OFFSETHIS, $OFFSETSEC and $TZNAME
 */
function getTzOffsetForDate( $timezonesarray, $tzid, $timestamp ) {
    static $OFFSETHIS = 'offsetHis';
    static $OFFSETSEC = 'offsetSec';
    static $TZBEFORE = 'tzbefore';
    static $TZAFTER = 'tzafter';
    static $TZNAME = 'tzname';
    if( is_array( $timestamp )) {
        $timestamp = \gmmktime(
            $timestamp[Util::$LCHOUR],
            $timestamp[Util::$LCMIN],
            $timestamp[Util::$LCSEC],
            $timestamp[Util::$LCMONTH],
            $timestamp[Util::$LCDAY],
            $timestamp[Util::$LCYEAR]
        );
    }
    $tzoffset = [];
    // something to return if all goes wrong (such as if $tzid doesn't find us an array of dates)
    $tzoffset[$OFFSETHIS] = '+0000';
    $tzoffset[$OFFSETSEC] = 0;
    $tzoffset[$TZNAME]    = '?';
    if( ! isset( $timezonesarray[$tzid] )) {
        return $tzoffset;
    }
    $tzdatearray = $timezonesarray[$tzid];
    if( is_array( $tzdatearray )) {
        sort( $tzdatearray ); // just in case
        if( $timestamp < $tzdatearray[0][Util::$LCTIMESTAMP] ) {
            // our date is before the first change
            $tzoffset[$OFFSETHIS] = $tzdatearray[0][$TZBEFORE][$OFFSETHIS];
            $tzoffset[$OFFSETSEC] = $tzdatearray[0][$TZBEFORE][$OFFSETSEC];
            $tzoffset[$TZNAME]    = $tzdatearray[0][$TZBEFORE][$OFFSETHIS]; // we don't know the tzname in this case
        }
        elseif( $timestamp >= $tzdatearray[count( $tzdatearray ) - 1][Util::$LCTIMESTAMP] ) {
            // our date is after the last change (we do this so our scan can stop at the last record but one)
            $tzoffset[$OFFSETHIS] = $tzdatearray[count( $tzdatearray ) - 1][$TZAFTER][$OFFSETHIS];
            $tzoffset[$OFFSETSEC] = $tzdatearray[count( $tzdatearray ) - 1][$TZAFTER][$OFFSETSEC];
            $tzoffset[$TZNAME]    = $tzdatearray[count( $tzdatearray ) - 1][$TZAFTER][$TZNAME];
        }
        else {
            // our date somewhere in between
            // loop through the list of dates and stop at the one where the timestamp is before our date and the next one is after it
            // we don't include the last date in our loop as there isn't one after it to check
            for( $i = 0; $i <= \count( $tzdatearray ) - 2; $i++ ) {
                if(( $timestamp >= $tzdatearray[$i][Util::$LCTIMESTAMP] ) &&
                    ( $timestamp < $tzdatearray[$i + 1][Util::$LCTIMESTAMP] )) {
                    $tzoffset[$OFFSETHIS] = $tzdatearray[$i][$TZAFTER][$OFFSETHIS];
                    $tzoffset[$OFFSETSEC] = $tzdatearray[$i][$TZAFTER][$OFFSETSEC];
                    $tzoffset[$TZNAME]    = $tzdatearray[$i][$TZAFTER][$TZNAME];
                    break;
                }
            }
        }
    }
    return $tzoffset;
}

/**
 * Return an array containing all the timezone data in the Vcalendar object
 *
 * @param Vcalendar $Vcalendar iCalcreator calendar instance
 * @return array    time zone transition timestamp,
 *                             array before(offsetHis, offsetSec),
 *                             array after(offsetHis, offsetSec, tzname)
 *                             based on the timezone data in the Vcalendar object
 */
function getTimezonesAsDateArrays( $Vcalendar ) {
    static $TZID = 'tzid';
    $timezonedata = [];
    while( $vtz = $Vcalendar->getComponent( Vcalendar::VTIMEZONE )) {
        $tzid       = $vtz->getProperty( $TZID );
        $alltzdates = [];
        while( $vtzc = $vtz->getComponent( Vcalendar::STANDARD )) {
            $newtzdates = expandTimezoneDates( $vtzc );
            $alltzdates = array_merge( $alltzdates, $newtzdates );
        }
        while( $vtzc = $vtz->getComponent( Vcalendar::DAYLIGHT )) {
            $newtzdates = expandTimezoneDates( $vtzc );
            $alltzdates = array_merge( $alltzdates, $newtzdates );
        }
        sort( $alltzdates );
        $timezonedata[$tzid] = $alltzdates;
    }
    return $timezonedata;
}

/**
 * Returns an array containing time zone data from Vtimezone standard/daylight instances
 *
 * @param object $vtzc     an iCalcreator calendar standard/daylight instance
 * @return array         time zone data;
 *                         array before(offsetHis, offsetSec),
 *                         array after(offsetHis, offsetSec, tzname)
 * @todo fix quickfix...
 */
function expandTimezoneDates( $vtzc ) {
    static $OFFSETHIS = 'offsetHis';
    static $OFFSETSEC = 'offsetSec';
    static $TZBEFORE = 'tzbefore';
    static $TZAFTER = 'tzafter';
    static $TZNAME = 'tzname';
    static $YEARLY = 'YEARLY';
    static $FMTDATE = '%04d%02d%02dT%02d%02d%02d';
    static $DAYNAMES = [
        'SU' => 'Sunday',
        'MO' => 'Monday',
        'TU' => 'Tuesday',
        'WE' => 'Wednesday',
        'TH' => 'Thursday',
        'FR' => 'Friday',
        'SA' => 'Saturday',
    ];
    static $MON = 'mon';
    static $MDAY = 'mday';
    static $HOURS = 'hours';
    static $MINUTES = 'minutes';
    static $SECONDS = 'seconds';
    static $MINUS1WEEK = '-1 week';
    static $PLUS1MONTH = '+1 month';
    static $SP1WEEK = ' week';
    static $SP1YEAR = ' year';
    static $PLUS10YEAR = '+10 year';
    $tzdates = [];
    // prepare time zone "description" to attach to each change
    $tzbefore             = [];
    $tzbefore[$OFFSETHIS] = $vtzc->getProperty( Util::$TZOFFSETFROM );
    $tzbefore[$OFFSETSEC] = Util::tz2offset( $tzbefore[$OFFSETHIS] );
    if(( Util::$MINUS != substr((string) $tzbefore[$OFFSETSEC], 0, 1 )) &&
        ( Util::$PLUS != substr((string) $tzbefore[$OFFSETSEC], 0, 1 ))) {
        $tzbefore[$OFFSETSEC] = Util::$PLUS . $tzbefore[$OFFSETSEC];
    }
    $tzafter             = [];
    $tzafter[$OFFSETHIS] = $vtzc->getProperty( Util::$TZOFFSETTO );
    $tzafter[$OFFSETSEC] = Util::tz2offset( $tzafter[$OFFSETHIS] );
    if(( Util::$MINUS != substr((string) $tzafter[$OFFSETSEC], 0, 1 )) &&
        ( Util::$PLUS != substr((string) $tzafter[$OFFSETSEC], 0, 1 ))) {
        $tzafter[$OFFSETSEC] = Util::$PLUS . $tzafter[$OFFSETSEC];
    }
    if( false === ( $tzafter[$TZNAME] = $vtzc->getProperty( Util::$TZNAME ))) {
        $tzafter[$TZNAME] = $tzafter[$OFFSETHIS];
    }
    // find out where to start from
    $dtstart          = $vtzc->getProperty( Util::$DTSTART );
    $dtstarttimestamp = mktime( $dtstart[Util::$LCHOUR],
                                $dtstart[Util::$LCMIN],
                                $dtstart[Util::$LCSEC],
                                $dtstart[Util::$LCMONTH],
                                $dtstart[Util::$LCDAY],
                                $dtstart[Util::$LCYEAR]
    );
    if( ! isset( $dtstart[Util::$UNPARSEDTEXT] )) // ??
    {
        $dtstart[Util::$UNPARSEDTEXT] = sprintf( $FMTDATE, $dtstart[Util::$LCYEAR],
                                                 $dtstart[Util::$LCMONTH],
                                                 $dtstart[Util::$LCDAY],
                                                 $dtstart[Util::$LCHOUR],
                                                 $dtstart[Util::$LCMIN],
                                                 $dtstart[Util::$LCSEC]
        );
    }
    if( $dtstarttimestamp == 0 ) {
        // it seems that the dtstart string may not have parsed correctly
        // let's set a timestamp starting from 1902, using the time part of the original string
        // so that the time will change at the right time of day
        // at worst we'll get midnight again
        $origdtstartsplit = explode( 'T', $dtstart[Util::$UNPARSEDTEXT] );
        $dtstarttimestamp = strtotime( '19020101', 0 );
        $dtstarttimestamp = strtotime( $origdtstartsplit[1], $dtstarttimestamp );
    }
    // the date (in dtstart and opt RDATE/RRULE) is ALWAYS LOCAL (not utc!!), adjust from 'utc' to 'local' timestamp
    $diff             = -1 * $tzbefore[$OFFSETSEC];
    $dtstarttimestamp += $diff;
    // add this (start) change to the array of changes
    $tzdates[] = [
        Util::$LCTIMESTAMP => $dtstarttimestamp,
        $TZBEFORE          => $tzbefore,
        $TZAFTER           => $tzafter,
    ];
    $datearray = getdate( $dtstarttimestamp );
    // save original array to use time parts, because strtotime (used below) apparently loses the time
    $changetime = $datearray;
    // generate dates according to an RRULE line
    $rrule = $vtzc->getProperty( Util::$RRULE );
    if( is_array( $rrule )) {
        if( $rrule[Util::$FREQ] == $YEARLY ) {
            // calculate transition dates starting from DTSTART
            $offsetchangetimestamp = $dtstarttimestamp;
            // calculate transition dates until 10 years in the future
            $stoptimestamp = strtotime( $PLUS10YEAR, time());
            // if UNTIL is set, calculate until then (however far ahead)
            if( isset( $rrule[Util::$UNTIL] ) && ( $rrule[Util::$UNTIL] != Util::$SP0 )) {
                $stoptimestamp = mktime(
                    $rrule[Util::$UNTIL][Util::$LCHOUR],
                    $rrule[Util::$UNTIL][Util::$LCMIN],
                    $rrule[Util::$UNTIL][Util::$LCSEC],
                    $rrule[Util::$UNTIL][Util::$LCMONTH],
                    $rrule[Util::$UNTIL][Util::$LCDAY],
                    $rrule[Util::$UNTIL][Util::$LCYEAR]
                );
            }
            $count     = 0;
            $stopcount = isset( $rrule[Util::$COUNT] ) ? $rrule[Util::$COUNT] : 0;
            // repeat so long as we're between DTSTART and UNTIL, or we haven't prepared COUNT dates
            while( $offsetchangetimestamp < $stoptimestamp &&
                ( $stopcount == 0 || $count < $stopcount )) {
                // break up the timestamp into its parts
                $datearray = getdate( $offsetchangetimestamp );
                if( isset( $rrule[Util::$BYMONTH] ) && ( $rrule[Util::$BYMONTH] != 0 )) {
                    // set the month
                    $datearray[$MON] = $rrule[Util::$BYMONTH];
                }
                if( isset( $rrule[Util::$BYMONTHDAY] )) {         // start quickfix...
                    // set first found/specific day of month
                    $datearray[$MDAY] = ( is_array( $rrule[Util::$BYMONTHDAY] ))
                        ? reset( $rrule[Util::$BYMONTHDAY] )
                        : $rrule[Util::$BYMONTHDAY]; // end quickfix
                }
                elseif( isset( $rrule[Util::$BYDAY] ) && is_array( $rrule[Util::$BYDAY] )) {  // update: 'isset...'
                    // find the Xth WKDAY in the month
                    // the starting point for this process is the first of the month set above
                    $datearray[$MDAY] = 1;
                    // turn $datearray as it is now back into a timestamp
                    $offsetchangetimestamp = mktime(
                        $datearray[$HOURS],
                        $datearray[$MINUTES],
                        $datearray[$SECONDS],
                        $datearray[$MON],
                        $datearray[$MDAY],
                        $datearray[Util::$LCYEAR]
                    );
                    if( $rrule[Util::$BYDAY][0] > 0 ) {
                        // to find Xth WKDAY in month, we find last WKDAY in month before
                        // we do that by finding first WKDAY in this month and going back one week
                        // then we add X weeks (below)
                        $offsetchangetimestamp = strtotime( $DAYNAMES[$rrule[Util::$BYDAY][Util::$DAY]],
                                                            $offsetchangetimestamp
                        );
                        $offsetchangetimestamp = strtotime( $MINUS1WEEK, $offsetchangetimestamp );
                    }
                    else {
                        // to find Xth WKDAY before the end of the month, we find the first WKDAY in the following month
                        // we do that by going forward one month and going to WKDAY there
                        // then we subtract X weeks (below)
                        $offsetchangetimestamp = strtotime( $PLUS1MONTH, $offsetchangetimestamp );
                        $offsetchangetimestamp = strtotime( $DAYNAMES[$rrule[Util::$BYDAY][Util::$DAY]],
                                                            $offsetchangetimestamp
                        );
                    }
                    // now move forward or back the appropriate number of weeks, into the month we want
                    $offsetchangetimestamp = strtotime( $rrule[Util::$BYDAY][0] . $SP1WEEK, $offsetchangetimestamp );
                    $datearray             = getdate( $offsetchangetimestamp );
                }
                // convert the date parts back into a timestamp, setting the time parts according to the
                // original time data which we stored
                $offsetchangetimestamp = mktime(
                    $changetime[$HOURS],
                    $changetime[$MINUTES],
                    $changetime[$SECONDS] + $diff,
                    $datearray[$MON],
                    $datearray[$MDAY],
                    $datearray[Util::$LCYEAR]
                );
                // add this change to the array of changes
                $tzdates[] = [
                    Util::$LCTIMESTAMP => $offsetchangetimestamp,
                    $TZBEFORE          => $tzbefore,
                    $TZAFTER           => $tzafter,
                ];
                // update \counters (timestamp and \count)
                $offsetchangetimestamp = strtotime( Util::$PLUS
                                                    . (( isset( $rrule[Util::$INTERVAL] ) && ( $rrule[Util::$INTERVAL] != 0 ))
                                                        ? $rrule[Util::$INTERVAL] : 1 )
                                                    . $SP1YEAR, $offsetchangetimestamp
                );
                $count                 += 1;
            }
        }
    }
    // generate dates according to RDATE lines
    while( $rdates = $vtzc->getProperty( Util::$RDATE )) {
        if( is_array( $rdates )) {
            foreach( $rdates as $rdate ) {
                // convert the explicit change date to a timestamp
                $offsetchangetimestamp = \mktime(
                    $rdate[Util::$LCHOUR],
                    $rdate[Util::$LCMIN],
                    $rdate[Util::$LCSEC] + $diff,
                    $rdate[Util::$LCMONTH],
                    $rdate[Util::$LCDAY],
                    $rdate[Util::$LCYEAR]
                );
                // add this change to the array of changes
                $tzdates[] = [
                    Util::$LCTIMESTAMP => $offsetchangetimestamp,
                    $TZBEFORE          => $tzbefore,
                    $TZAFTER           => $tzafter,
                ];
            }
        }
    }
    return $tzdates;
}