<?php

/**
 * PHPExcel
 *
 * Copyright (c) 2006 - 2013 PHPExcel
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package	PHPExcel_Shared
 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license	http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
 * @version	1.7.9, 2013-06-02
 */


/**
 * PHPExcel_Shared_TimeZone
 *
 * @category   PHPExcel
 * @package	PHPExcel_Shared
 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
 */
class PHPExcel_Shared_TimeZone
{
	/*
	 * Default Timezone used for date/time conversions
	 *
	 * @private
	 * @var	string
	 */
	protected static $_timezone	= 'UTC';

	/**
	 * Validate a Timezone name
	 *
	 * @param	 string		$timezone			Time zone (e.g. 'Europe/London')
	 * @return	 boolean						Success or failure
	 */
	public static function _validateTimeZone($timezone) {
		if (in_array($timezone, DateTimeZone::listIdentifiers())) {
			return TRUE;
		}
		return FALSE;
	}

	/**
	 * Set the Default Timezone used for date/time conversions
	 *
	 * @param	 string		$timezone			Time zone (e.g. 'Europe/London')
	 * @return	 boolean						Success or failure
	 */
	public static function setTimeZone($timezone) {
		if (self::_validateTimezone($timezone)) {
			self::$_timezone = $timezone;
			return TRUE;
		}
		return FALSE;
	}	//	function setTimezone()


	/**
	 * Return the Default Timezone used for date/time conversions
	 *
	 * @return	 string		Timezone (e.g. 'Europe/London')
	 */
	public static function getTimeZone() {
		return self::$_timezone;
	}	//	function getTimezone()


	/**
	 *	Return the Timezone transition for the specified timezone and timestamp
	 *
	 *	@param		DateTimeZone	 	$objTimezone	The timezone for finding the transitions
	 *	@param		integer	 			$timestamp		PHP date/time value for finding the current transition
	 *	@return	 	array				The current transition details
	 */
	private static function _getTimezoneTransitions($objTimezone, $timestamp) {
		$allTransitions = $objTimezone->getTransitions();
		$transitions = array();
		foreach($allTransitions as $key => $transition) {
			if ($transition['ts'] > $timestamp) {
				$transitions[] = ($key > 0) ? $allTransitions[$key - 1] : $transition;
				break;
			}
			if (empty($transitions)) {
				$transitions[] = end($allTransitions);
			}
		}

		return $transitions;
	}

	/**
	 *	Return the Timezone offset used for date/time conversions to/from UST
	 *	This requires both the timezone and the calculated date/time to allow for local DST
	 *
	 *	@param		string	 			$timezone		The timezone for finding the adjustment to UST
	 *	@param		integer	 			$timestamp		PHP date/time value
	 *	@return	 	integer				Number of seconds for timezone adjustment
	 *	@throws		PHPExcel_Exception
	 */
	public static function getTimeZoneAdjustment($timezone, $timestamp) {
		if ($timezone !== NULL) {
			if (!self::_validateTimezone($timezone)) {
				throw new PHPExcel_Exception("Invalid timezone " . $timezone);
			}
		} else {
			$timezone = self::$_timezone;
		}

		if ($timezone == 'UST') {
			return 0;
		}

		$objTimezone = new DateTimeZone($timezone);
		if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
			$transitions = $objTimezone->getTransitions($timestamp,$timestamp);
		} else {
			$transitions = self::_getTimezoneTransitions($objTimezone, $timestamp);
		}

		return (count($transitions) > 0) ? $transitions[0]['offset'] : 0;
	}

}