<?php
/**
 * Web server detection.
 *
 * @package AIBlackout
 */

namespace AIBlackout\Enforcement;

defined( 'ABSPATH' ) || exit;

/**
 * Identifies the web server, and therefore which enforcement layers are
 * real.
 *
 * @since 1.0.0
 */
class ServerProfile {

	/**
	 * Apache, or a drop-in replacement that reads .htaccess.
	 *
	 * @var string
	 */
	const APACHE = 'apache';

	/**
	 * LiteSpeed, which also reads .htaccess.
	 *
	 * @var string
	 */
	const LITESPEED = 'litespeed';

	/**
	 * Nginx, which does not read .htaccess.
	 *
	 * @var string
	 */
	const NGINX = 'nginx';

	/**
	 * Anything else, or a server that did not identify itself.
	 *
	 * @var string
	 */
	const UNKNOWN = 'unknown';

	/**
	 * Returns the raw SERVER_SOFTWARE string.
	 *
	 * @return string Server software, or an empty string when unavailable.
	 */
	public function get_software(): string {
		if ( empty( $_SERVER['SERVER_SOFTWARE'] ) ) {
			return '';
		}

		return sanitize_text_field( wp_unslash( $_SERVER['SERVER_SOFTWARE'] ) );
	}

	/**
	 * Returns the detected server type.
	 *
	 * @return string One of the class constants.
	 */
	public function get_type(): string {
		$software = strtolower( $this->get_software() );

		if ( '' === $software ) {
			return self::UNKNOWN;
		}

		// LiteSpeed is checked first; it does not identify as Apache.
		if ( false !== strpos( $software, 'litespeed' ) ) {
			return self::LITESPEED;
		}

		if ( false !== strpos( $software, 'nginx' ) ) {
			return self::NGINX;
		}

		if ( false !== strpos( $software, 'apache' ) ) {
			return self::APACHE;
		}

		return self::UNKNOWN;
	}

	/**
	 * Returns the Apache version, when the server states one.
	 *
	 * @return string Version string such as 2.4.62, or an empty string.
	 */
	public function get_apache_version(): string {
		if ( self::APACHE !== $this->get_type() ) {
			return '';
		}

		if ( ! preg_match( '#apache/([0-9]+(?:\.[0-9]+)*)#i', $this->get_software(), $matches ) ) {
			return '';
		}

		return $matches[1];
	}

	/**
	 * Whether this is an Apache release too old for the rules we write.
	 *
	 * @return bool True when Apache is older than 2.4.
	 */
	public function is_legacy_apache(): bool {
		$version = $this->get_apache_version();

		if ( '' === $version ) {
			return false;
		}

		return version_compare( $version, '2.4', '<' );
	}

	/**
	 * Whether the server reads .htaccess files.
	 *
	 * @return bool True when the .htaccess layer can work.
	 */
	public function supports_htaccess(): bool {
		$type = $this->get_type();

		if ( self::APACHE === $type ) {
			return ! $this->is_legacy_apache();
		}

		if ( self::LITESPEED === $type ) {
			return true;
		}

		// Core sets this global for the same purpose.
		if ( function_exists( 'got_mod_rewrite' ) && got_mod_rewrite() ) {
			return true;
		}

		return false;
	}

	/**
	 * Whether the site is served by nginx, so the copy-paste snippet applies.
	 *
	 * @return bool True on nginx.
	 */
	public function is_nginx(): bool {
		return self::NGINX === $this->get_type();
	}

	/**
	 * Returns a plain-language description of what this means for the user.
	 *
	 * @return string Human-readable explanation.
	 */
	public function describe(): string {
		switch ( $this->get_type() ) {
			case self::APACHE:
				if ( $this->is_legacy_apache() ) {
					return sprintf(
						/* translators: %s: Apache version string, such as 2.2.34. */
						__( 'Your site runs Apache %s. The .htaccess rules this plugin writes need Apache 2.4, so that layer has been switched off here rather than writing rules that would block nothing.', 'ai-blackout' ),
						$this->get_apache_version()
					);
				}

				return __( 'Your site runs on Apache, so the .htaccess layer works here.', 'ai-blackout' );

			case self::LITESPEED:
				return __( 'Your site runs on LiteSpeed, which reads .htaccess, so that layer works here.', 'ai-blackout' );

			case self::NGINX:
				return __( 'Your site runs on nginx, which does not read .htaccess. Use the nginx snippet instead. A plugin cannot write nginx configuration.', 'ai-blackout' );

			default:
				return __( 'Your server did not identify itself, so the .htaccess layer has been switched off rather than reporting protection that may not exist.', 'ai-blackout' );
		}
	}
}