<?php
/**
 * PHP security support table.
 *
 * @package Brachmelder
 */

namespace Brachmelder\Check;

defined( 'ABSPATH' ) || exit;

/**
 * Compares the server's PHP version with the end of security support.
 *
 * Source: https://www.php.net/supported-versions.php
 */
final class PhpSupport {

	const ENDED     = 'ended';
	const ENDING    = 'ending';
	const SUPPORTED = 'supported';
	const UNKNOWN   = 'unknown';

	/**
	 * Warn this many days before support ends.
	 */
	const WARN_DAYS = 365;

	/**
	 * End of security support per PHP branch (Y-m-d).
	 *
	 * @var array<string, string>
	 */
	const END_OF_SECURITY_SUPPORT = array(
		'7.0' => '2019-01-10',
		'7.1' => '2019-12-01',
		'7.2' => '2020-11-30',
		'7.3' => '2021-12-06',
		'7.4' => '2022-11-28',
		'8.0' => '2023-11-26',
		'8.1' => '2025-12-31',
		'8.2' => '2026-12-31',
		'8.3' => '2027-12-31',
		'8.4' => '2028-12-31',
		'8.5' => '2029-12-31',
	);

	/**
	 * Oldest branch that is supported for more than WARN_DAYS, i.e. a sensible upgrade target.
	 *
	 * @param int $now Current Unix timestamp.
	 * @return string
	 */
	public static function recommended( int $now ): string {
		foreach ( array_keys( self::END_OF_SECURITY_SUPPORT ) as $branch ) {
			if ( self::SUPPORTED === self::evaluate( (string) $branch, $now )['status'] ) {
				return (string) $branch;
			}
		}
		return (string) array_key_last( self::END_OF_SECURITY_SUPPORT );
	}

	/**
	 * Evaluates a PHP version.
	 *
	 * @param string $version PHP version, e.g. PHP_VERSION.
	 * @param int    $now     Current Unix timestamp.
	 * @return array{status: string, branch: string, end: string, days_left: int}
	 */
	public static function evaluate( string $version, int $now ): array {
		$branch = WpVersions::major( $version );
		$end    = self::END_OF_SECURITY_SUPPORT[ $branch ] ?? '';

		if ( '' === $end ) {
			// Branches newer than the table are fine, older ones are long unsupported.
			$status = self::UNKNOWN;
			if ( '' !== $branch ) {
				$newest = (string) array_key_last( self::END_OF_SECURITY_SUPPORT );
				$status = version_compare( $branch, $newest, '>' ) ? self::SUPPORTED : self::ENDED;
			}
			return array(
				'status'    => $status,
				'branch'    => $branch,
				'end'       => '',
				'days_left' => 0,
			);
		}

		// End of day UTC.
		$end_ts    = (int) strtotime( $end . ' 23:59:59 UTC' );
		$days_left = (int) floor( ( $end_ts - $now ) / 86400 );

		if ( $end_ts < $now ) {
			$status = self::ENDED;
		} elseif ( $days_left <= self::WARN_DAYS ) {
			$status = self::ENDING;
		} else {
			$status = self::SUPPORTED;
		}

		return array(
			'status'    => $status,
			'branch'    => $branch,
			'end'       => $end,
			'days_left' => $days_left,
		);
	}
}