<?php
/**
 * XSPEED_DROPIN
 * Drop-in cache loader. Serves cached HTML before WordPress fully boots.
 *
 * IMPORTANT: This file is included by wp-settings.php BEFORE
 * wp-includes/formatting.php and wp-includes/load.php are loaded, so NO
 * WordPress functions (sanitize_text_field, wp_unslash, is_admin,
 * HOUR_IN_SECONDS, etc.) are available here. Use raw PHP only.
 *
 * @package XSpeed
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

// Only handle plain GET requests.
// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.MissingUnslash,WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- Drop-in runs before wp-includes/formatting.php loads, so wp_unslash() and sanitize_text_field() are unavailable. Value is upper-cased and matched against the literal string 'GET'; never echoed, never executed.
$xspeed_method = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( (string) $_SERVER['REQUEST_METHOD'] ) : '';
if ( 'GET' !== $xspeed_method ) {
	return;
}

// Skip cached query-string requests (search, pagination via ?, etc.).
if ( ! empty( $_SERVER['QUERY_STRING'] ) ) {
	return;
}

// Honor explicit bypass header. xSpeed's own benchmark REST endpoint
// sends `X-XSpeed-Bypass: 1` so we can measure uncached TTFB for the
// before/after comparison on the dashboard. Harmless if a third party
// sends it — they just get an uncached response.
// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.MissingUnslash,WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- Drop-in runs before WP loads. Value is only used as an isset() check + literal string comparison, never echoed.
if ( ! empty( $_SERVER['HTTP_X_XSPEED_BYPASS'] ) ) {
	return;
}

if ( ! isset( $_SERVER['REQUEST_URI'] ) ) {
	return;
}

// Raw-PHP sanitization: strip null bytes only. This value is used for
// substring comparisons and as input to md5() — never echoed, never
// executed, never written to disk as data. Magic quotes was removed in
// PHP 5.4 and the plugin requires PHP 7.4+, so no unslashing is needed.
// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.MissingUnslash,WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- Drop-in runs before wp_unslash()/sanitize_text_field() are loaded; null-byte strip is the strongest sanitizer available pre-WP-bootstrap. Value is only used for substring comparison and as md5() input.
$xspeed_request_uri = str_replace( "\0", '', (string) $_SERVER['REQUEST_URI'] );

// Skip admin / login requests.
if ( false !== strpos( $xspeed_request_uri, '/wp-admin' ) || false !== strpos( $xspeed_request_uri, '/wp-login' ) ) {
	return;
}

// Skip logged-in users and comment authors — never serve a cached page to
// someone who has a session cookie. Reading raw cookies; we only inspect
// names, not values.
if ( ! empty( $_COOKIE ) ) {
	foreach ( $_COOKIE as $xspeed_cookie_name => $xspeed_cookie_value ) {
		unset( $xspeed_cookie_value );
		$xspeed_cookie_name = (string) $xspeed_cookie_name;
		if ( 0 === strpos( $xspeed_cookie_name, 'wordpress_logged_in' )
			|| 0 === strpos( $xspeed_cookie_name, 'comment_author_' )
			|| 0 === strpos( $xspeed_cookie_name, 'wp-postpass_' ) ) {
			return;
		}
	}
}

// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.MissingUnslash,WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- Drop-in runs before wp_unslash()/sanitize_text_field() are loaded. Value is filtered through a strict allowlist regex below (letters, digits, dot, hyphen, colon) and only used as md5() input for the cache key.
$xspeed_host = isset( $_SERVER['HTTP_HOST'] ) ? (string) $_SERVER['HTTP_HOST'] : 'default';
$xspeed_host = str_replace( "\0", '', $xspeed_host );
// Restrict host to a safe charset (letters, digits, dot, hyphen, colon for port).
$xspeed_host = preg_replace( '/[^a-zA-Z0-9.\-:]/', '', $xspeed_host );

$xspeed_path_only  = strtok( $xspeed_request_uri, '?' );
$xspeed_cache_key  = md5( $xspeed_host . $xspeed_path_only );
$xspeed_cache_file = WP_CONTENT_DIR . '/cache/xspeed/' . $xspeed_cache_key . '.html';

if ( file_exists( $xspeed_cache_file ) ) {
	// 24h TTL in seconds. HOUR_IN_SECONDS is a WordPress constant defined
	// after this drop-in loads, so use a literal here.
	$xspeed_age = time() - filemtime( $xspeed_cache_file );
	if ( $xspeed_age < 86400 ) {
		// PHP-served cache hit (the ~85ms fallback path). The nginx static
		// rewrite sends "HIT (nginx)" for the fast 5-15ms path; same header,
		// distinct value so you can tell which layer served the page.
		header( 'X-XSpeed-Cache: HIT (php)' );
		// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_readfile -- Drop-in runs before WP_Filesystem is available; readfile is optimal for streaming a static cache file to the visitor.
		readfile( $xspeed_cache_file );
		exit;
	}
}