<?php

namespace TablePress\PhpOffice\PhpSpreadsheet\Shared;

use DateTimeZone;
use TablePress\PhpOffice\PhpSpreadsheet\Exception as PhpSpreadsheetException;

class TimeZone
{
	/**
	 * Default Timezone used for date/time conversions.
	 */
	protected static string $timezone = 'UTC';

	/**
	 * Validate a Timezone name.
	 *
	 * @param string $timezoneName Time zone (e.g. 'Europe/London')
	 *
	 * @return bool Success or failure
	 */
	private static function validateTimeZone(string $timezoneName): bool
	{
		return in_array($timezoneName, DateTimeZone::listIdentifiers(DateTimeZone::ALL_WITH_BC), true);
	}

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

			return true;
		}

		return false;
	}

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

	/**
	 *    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 $timezoneName The timezone for finding the adjustment to UST
	 * @param float|int $timestamp PHP date/time value
	 *
	 * @return int Number of seconds for timezone adjustment
	 */
	public static function getTimeZoneAdjustment(?string $timezoneName, $timestamp): int
	{
		$timezoneName = $timezoneName ?? self::$timezone;
		$dtobj = Date::dateTimeFromTimestamp("$timestamp");
		if (!self::validateTimeZone($timezoneName)) {
			throw new PhpSpreadsheetException("Invalid timezone $timezoneName");
		}
		$dtobj->setTimeZone(new DateTimeZone($timezoneName));

		return $dtobj->getOffset();
	}
}
