xspeed / includes / class-cache.php

class-cache.php in xSpeed Cache: AI-Powered Performance Hub with MCP, Caching & CDN 1.1.7, at includes/class-cache.php

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1	<?php
2	/**
3	* Page cache engine.
4	*
5	* @package XSpeed
6	*/
7
8	namespace XSpeed;
9
10	defined( 'ABSPATH' ) \|\| exit;
11
12	class Cache {
13
14	/**
15	* Output-buffer nesting level at which we opened our cache buffer, so
16	* `close_buffer()` can flush ONLY our buffer and never disturb a buffer
17	* another plugin pushed on top of (or below) ours.
18	*
19	* @var int\|null
20	*/
21	private static $buffer_level = null;
22
23	/**
24	* The `X-XSpeed-Cache` value decided for this request, and — when the
25	* decision was BYPASS — the slug of the gate that made it.
26	*
27	* Recorded as well as sent so unit tests (CLI SAPI, where header() is a
28	* no-op and headers_sent() is meaningless) can assert on the decision.
29	*
30	* @var string
31	*/
32	private static $status_header = '';
33	private static $bypass_reason = '';
34
35	/**
36	* Cache key whose write was deferred to shutdown because a render-time
37	* translation plugin's buffer wraps ours. Null on every ordinary request.
38	*
39	* @var string\|null
40	*/
41	private static $deferred_key = null;
42
43	/**
44	* Translated page HTML captured by the outer buffer, for the deferred
45	* write. Only populated when a translation plugin is active.
46	*
47	* @var string
48	*/
49	private static $translated_output = '';
50
51	/**
52	* Did finalize_buffer() run to completion on this request?
53	*
54	* The deferred translated write runs as a PHP shutdown function, which
55	* fires after a `wp_die()` or a bare `exit()` exactly as it does after a
56	* clean render. Only finalize_buffer() sets this, and only at the point
57	* where it has the full buffer in hand — so an aborted render leaves it
58	* false and the writer declines rather than caching a truncated page
59	* under the real key.
60	*
61	* @var bool
62	*/
63	private static $render_completed = false;
64
65	public function __construct() {
66	/**
67	* When the page-cache output buffer opens.
68	*
69	* Filterable because buffer ORDER decides what gets cached. PHP's
70	* output buffers are LIFO: the last one opened is innermost, and its
71	* callback runs first. A render-time translation plugin that opens
72	* an outer buffer therefore translates AFTER we have already captured
73	* and cached the raw HTML — see translation_buffer_compat().
74	*
75	* @param string $hook Hook to open the buffer on.
76	* @param int $priority Priority for that hook.
77	*/
78	$hook = (string) apply_filters( 'xspeed_cache_buffer_hook', 'template_redirect' );
79	$priority = (int) apply_filters( 'xspeed_cache_buffer_priority', 0 );
80	add_action( $hook, array( $this, 'maybe_start_cache' ), $priority );
81
82	// When a render-time translation plugin is present, open one extra
83	// buffer OUTSIDE its own so we can capture post-translation HTML.
84	// TranslatePress opens on `init` priority 0, so we take a negative
85	// priority to land outside it. This buffer only collects bytes for
86	// the deferred cache write — it never modifies the response.
87	add_action(
88	'init',
89	static function () {
90	if ( ! self::translation_plugin_active() ) {
91	return;
92	}
93	// `init` fires on EVERY request type, and
94	// translation_plugin_active() is a class_exists() check that
95	// is true site-wide — so without this guard the buffer opened
96	// on REST, admin-ajax, cron and WP-CLI too. None of those
97	// reach template_redirect, so $deferred_key stays null and
98	// the collected bytes are never released: a long-running
99	// WP-CLI command copied every byte of its output into a
100	// string that grew for the life of the process.
101	if ( is_admin()
102	\|\| wp_doing_ajax()
103	\|\| wp_doing_cron()
104	\|\| ( defined( 'REST_REQUEST' ) && REST_REQUEST )
105	\|\| ( defined( 'WP_CLI' ) && WP_CLI )
106	\|\| ( defined( 'XMLRPC_REQUEST' ) && XMLRPC_REQUEST ) ) {
107	return;
108	}
109	ob_start(
110	static function ( $chunk ) {
111	self::$translated_output .= $chunk;
112	return $chunk;
113	}
114	);
115	},
116	(int) apply_filters( 'xspeed_translation_outer_buffer_priority', -100 )
117	);
118
119	// Events that should invalidate cached output. Beyond posts/comments,
120	// this covers user and term changes — the REST cache can serve
121	// /wp/v2/users, /wp/v2/categories, /wp/v2/tags, and these also affect
122	// rendered author bylines / term-archive pages. Without them, an edit
123	// left the matching endpoint (and archives) stale for the full TTL.
124	// (FBS-82408)
125	$invalidate_hooks = array(
126	'save_post', 'deleted_post', 'trashed_post',
127	'comment_post', 'wp_set_comment_status',
128	'switch_theme', 'activated_plugin', 'deactivated_plugin',
129	// Users → /wp/v2/users + author archives.
130	'profile_update', 'user_register', 'deleted_user',
131	// Terms → /wp/v2/{taxonomy} + term archives.
132	'created_term', 'edited_term', 'delete_term',
133	);
134	foreach ( $invalidate_hooks as $hook ) {
135	add_action( $hook, array( __CLASS__, 'purge_all' ) );
136	add_action( $hook, array( 'XSpeed\\Minifier', 'purge_minified' ) );
137	}
138
139	add_action( 'update_option_xspeed_options', array( __CLASS__, 'on_settings_change' ), 10, 2 );
140
141	add_action( 'admin_bar_menu', array( $this, 'admin_bar_purge' ), 100 );
142	add_action( 'admin_post_xspeed_purge', array( $this, 'handle_admin_bar_purge' ) );
143	}
144
145	public static function on_settings_change( $old, $new ) {
146	// gzip_enabled moved to xspeed_module_gzip — GzipModule owns the
147	// .htaccess flip via its own update_option_xspeed_module_gzip hook.
148	// Same migration is planned for cache_expiry + excluded_urls
149	// (Cache module). Keep this handler around for whatever still
150	// lives in the legacy blob (cache_enabled is special and goes
151	// through Cache::toggle anyway).
152
153	// Any settings change — purge caches so changes take effect.
154	self::purge_all( 'settings change' );
155	Minifier::purge_minified();
156	}
157
158	/**
159	* Stamp the request's cache decision on the response.
160	*
161	* `X-XSpeed-Cache` was only ever written on the serve-from-cache paths,
162	* so a miss and a deliberate bypass both came back with no header at all
163	* — indistinguishable from a `curl -I`, the first thing anyone reaches
164	* for when a site "isn't caching" (issue #10). The reason slug rides
165	* along on `X-XSpeed-Reason`, but only under WP_DEBUG so production
166	* responses stay clean. Slugs are fixed per gate — never the matched
167	* pattern, cookie or user-agent, which would echo request input back.
168	*
169	* @param string $value HIT (php) \| MISS \| BYPASS.
170	* @param string $reason Fixed slug naming the gate, for BYPASS only.
171	*/
172	private static function mark( string $value, string $reason = '' ): void {
173	self::$status_header = $value;
174	self::$bypass_reason = $reason;
175
176	if ( headers_sent() ) {
177	return;
178	}
179	header( 'X-XSpeed-Cache: ' . $value );
180	if ( '' !== $reason && defined( 'WP_DEBUG' ) && WP_DEBUG ) {
181	header( 'X-XSpeed-Reason: ' . $reason );
182	}
183	}
184
185	/** Record a bypass gate and answer "don't cache" in one statement. */
186	private static function bypass( string $reason ): bool {
187	self::mark( 'BYPASS', $reason );
188	return false;
189	}
190
191	/** The X-XSpeed-Cache value decided for this request ('' if none yet). */
192	public static function status_header(): string {
193	return self::$status_header;
194	}
195
196	/** The bypass gate slug for this request ('' unless BYPASS). */
197	public static function bypass_reason(): string {
198	return self::$bypass_reason;
199	}
200
201	public function maybe_start_cache() {
202	if ( ! self::should_cache() ) {
203	// PHP has just evaluated the FULL exclusion rule list — including
204	// the `~regex` patterns the server config can't express — and
205	// decided this visitor must not be served from cache. Record that
206	// verdict in the conventional bypass cookie so the web server can
207	// enforce it on subsequent requests without starting PHP.
208	//
209	// This is what stops most settings changes from needing an nginx
210	// reload: the config tests one fixed cookie name forever, and the
211	// rule list behind it can change freely.
212	self::sync_bypass_cookie( true );
213	return;
214	}
215
216	// Cacheable: clear any stale bypass cookie, or a visitor who once
217	// had a cart would keep skipping the fast path long after checkout.
218	self::sync_bypass_cookie( false );
219
220	$key = self::cache_key();
221	$file = self::cache_file_for( $key );
222
223	if ( file_exists( $file ) && ! self::is_expired( $file ) ) {
224	Hit_Counter::record_hit();
225	// Emit the HIT marker on THIS path too. The drop-in
226	// (advanced-cache.php) sends "HIT (php)" and the nginx static
227	// rewrite sends "HIT (nginx)", but this template_redirect
228	// serve path — the one that runs when the drop-in isn't loaded
229	// (e.g. WP_CACHE not true) — previously streamed the cached
230	// file with NO marker, so a genuine HIT looked like a MISS in
231	// the response headers. Same header + value as the drop-in.
232	self::mark( 'HIT (php)' );
233	// Replay stored response bits so the HIT matches the original:
234	// a non-HTML Content-Type (cached feeds, sitemaps) and a non-200
235	// status (a cached 404 must serve 404, not 200). No-op for
236	// ordinary pages, which write no .meta.
237	$meta = self::read_meta( $key );
238	if ( ! headers_sent() ) {
239	if ( ! empty( $meta['status'] ) && function_exists( 'http_response_code' ) ) {
240	http_response_code( (int) $meta['status'] );
241	}
242	if ( ! empty( $meta['content_type'] ) && is_string( $meta['content_type'] ) ) {
243	header( 'Content-Type: ' . $meta['content_type'] );
244	}
245	// Conditional GET: emit Last-Modified + ETag and answer a
246	// matching If-Modified-Since / If-None-Match with 304 so
247	// aggregators (and browsers) skip re-downloading an unchanged
248	// cached response — the bandwidth win feeds are about.
249	// (FBS-82407 #5)
250	if ( self::serve_not_modified( $file ) ) {
251	exit; // 304 sent, no body.
252	}
253	}
254	// Serve the precompressed Brotli sibling when the client accepts
255	// it (an add-on, the Pro Brotli module, wrote <file>.br). On this
256	// PHP serve path the web server never sees the .br, so without
257	// this a br-capable client got the plain .html — precompression
258	// did nothing here. Falls through to plain readfile otherwise.
259	$br = self::maybe_serve_brotli( $file );
260	if ( null !== $br ) {
261	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_readfile -- streaming a static cache file directly; WP_Filesystem would buffer through PHP memory and is not appropriate for response streaming.
262	readfile( $br );
263	exit;
264	}
265	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_readfile -- readfile is optimal for streaming a static cache file directly to the visitor; WP_Filesystem would buffer through PHP memory and is not appropriate for response streaming.
266	readfile( $file );
267	exit;
268	}
269
270	// Cache miss → render fresh + write cache. On LiteSpeed we send an
271	// explicit "stand down" header so the server's LSCache module does
272	// NOT cache + shadow our response — xSpeed's own .htaccess static
273	// rewrite owns hit serving (and hit accounting) here, exactly as on
274	// Apache. See maybe_emit_lscache_headers() for the full rationale.
275	self::maybe_emit_lscache_headers();
276
277	// We're about to render fresh + cache → miss for this request.
278	// …UNLESS this request is a 404 or a known bot/scanner. Those reach the
279	// render path too, but counting them as cache misses makes the ratio
280	// meaningless — a wave of `/wp-x7.php` scanner 404s reads as a collapsing
281	// cache when nothing is wrong. Runs at template_redirect (priority 0), so
282	// is_404() is already resolved. Excluded requests are tallied separately
283	// for the "you absorbed N scanner hits" line, not dropped. (#118)
284	if ( self::miss_is_excluded() ) {
285	Hit_Counter::record_excluded();
286	} else {
287	Hit_Counter::record_miss();
288	}
289
290	// Stamp it, so "eligible but not cached yet" is visibly different
291	// from "deliberately bypassed" (issue #10). Headers can't be sent
292	// after the body starts, so this has to happen here, not in
293	// finalize_buffer() — nothing has been output at template_redirect.
294	self::mark( 'MISS' );
295
296
297	// WP < 6.9 fallback: ob_start() with a callback, paired with an
298	// explicit shutdown close so the buffer lifecycle is visible to
299	// reviewers and Plugin Check, instead of relying on PHP's implicit
300	// request-end flush. We record our nesting level so close_buffer()
301	// flushes ONLY the buffer we opened.
302	ob_start( array( __CLASS__, 'finalize_buffer' ) );
303	self::$buffer_level = ob_get_level();
304
305	add_action( 'shutdown', array( __CLASS__, 'close_buffer' ), 0 );
306	}
307
308	/**
309	* Close the cache buffer opened by maybe_start_cache().
310	*
311	* Guarded by the recorded buffer level so we never flush a buffer that
312	* another plugin pushed on top of (or under) ours. If something else is
313	* currently on top, we leave the stack alone — PHP's shutdown sequence
314	* will unwind buffers in order and our finalize_buffer() callback will
315	* still run when our level becomes the topmost one.
316	*/
317	public static function close_buffer() {
318	if ( null === self::$buffer_level ) {
319	return;
320	}
321	if ( ob_get_level() === self::$buffer_level ) {
322	ob_end_flush();
323	}
324	self::$buffer_level = null;
325	}
326
327	/**
328	* Are we buffering this request?
329	*
330	* Asked by Css_Combine_Buffer, which needs the finished HTML but must not
331	* open a second buffer when this one is already going to hand it the page
332	* through `xspeed_cache_final_html`. False here means the request is not
333	* cacheable — cache off, excluded URL, logged in — and the combiner has to
334	* provide its own buffer or it silently stops working. (#195)
335	*/
336	public static function is_buffering(): bool {
337	return null !== self::$buffer_level;
338	}
339
340	/**
341	* Is a render-time translation plugin going to wrap our output buffer?
342	*
343	* TranslatePress opens its translation buffer on `init` priority 0. We
344	* open ours on `template_redirect`, which runs much later, so ours nests
345	* INSIDE theirs. PHP unwinds output buffers LIFO — innermost callback
346	* first — so `finalize_buffer()` saw the raw, pre-translation HTML and
347	* cached that, while the live visitor still got the translated bytes from
348	* TRP's outer buffer.
349	*
350	* Result: the first (MISS) visitor to /fr/some-page/ got correct French;
351	* every visitor after got English body text under a `lang="fr-FR"`
352	* document, plus TRP's internal `#TRPLINKPROCESSED` link markers, which
353	* TRP strips at the very end of its own buffer and which therefore leak
354	* into anything captured from inside it.
355	*
356	* Note the ordering cannot be fixed from TRP's side: its
357	* `trp_start_output_buffer_priority` filter only moves the PRIORITY on
358	* `init`, and `init` always fires before `template_redirect` whatever the
359	* priority. The buffer that has to move is ours.
360	*
361	* Detected by main class rather than plugin path, so a renamed directory
362	* or a bundled copy still matches.
363	*/
364	public static function translation_plugin_active(): bool {
365	$active = class_exists( 'TRP_Translate_Press' );
366
367	/**
368	* Whether to treat this request as wrapped by a translation buffer.
369	*
370	* Lets a site add another render-time translation plugin (or opt out)
371	* without patching the engine.
372	*
373	* @param bool $active
374	*/
375	return (bool) apply_filters( 'xspeed_translation_plugin_active', $active );
376	}
377
378	/**
379	* Write the cache file for a request whose output was wrapped by a
380	* render-time translation plugin.
381	*
382	* Registered as a PHP shutdown function (not a WP `shutdown` action) so
383	* it runs after PHP has unwound the output-buffer stack — by which point
384	* the translation plugin's callback has transformed the bytes and its
385	* internal markers are gone.
386	*
387	* finalize_buffer() has already applied the status gate, the
388	* xspeed_cache_final_html filter and HTML minification to the
389	* untranslated copy and then declined to write it. Here we re-run only
390	* what's needed on the translated bytes: minify, write, and fire the
391	* same downstream hooks so Brotli / static-tree listeners behave
392	* identically to the ordinary path.
393	*/
394	public static function write_deferred_translated_cache(): void {
395	$key = self::$deferred_key;
396	self::$deferred_key = null;
397
398	// Release the collected bytes BEFORE the early return, so the static
399	// is cleared on every path rather than only when a key survived.
400	$full = self::$translated_output;
401	self::$translated_output = '';
402
403	$completed = self::$render_completed;
404	self::$render_completed = false;
405
406	if ( null === $key ) {
407	return;
408	}
409
410	// Did the render actually finish?
411	//
412	// This runs as a PHP shutdown function, which fires after a wp_die()
413	// or a bare exit() just as readily as after a clean render — but in
414	// those cases finalize_buffer() never returned, so the bytes we hold
415	// are a page that was cut off partway through. The length and
416	// TRPLINKPROCESSED checks below don't catch that: a fatal after the
417	// footer's translated markup is both over 255 bytes and free of TRP
418	// markers, i.e. truncated but entirely plausible. Caching it would
419	// freeze a half-rendered page under the real key for the full TTL.
420	//
421	// Serving this one URL uncached is the cheap failure; the corrupt
422	// cache entry is the expensive one.
423	if ( ! $completed ) {
424	return;
425	}
426
427	if ( strlen( $full ) < 255 ) {
428	return;
429	}
430
431	// Refuse to cache a copy still carrying the translation plugin's
432	// internal link markers. TRP strips these at the very end of its own
433	// buffer, so their presence means we captured too early — and a
434	// cached page containing them is SEO-visible damage. Better to serve
435	// this URL uncached than to freeze broken markup for the full TTL.
436	if ( false !== strpos( $full, 'TRPLINKPROCESSED' ) ) {
437	return;
438	}
439
440	$minify_opts = Settings_Manager::get( 'minify' );
441	if ( ! empty( $minify_opts['minify_html'] ) ) {
442	$full = Minifier::minify_html( $full );
443	}
444
445	// Per-site directory: on multisite every blog shares this tree, so
446	// entries are bucketed by host to keep one site's purge from
447	// sweeping the whole network. (#6)
448	self::ensure_host_dir();
449
450	$file = self::cache_file_for( $key );
451	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin context for credentials; this runs on a frontend shutdown where it's unavailable.
452	file_put_contents( $file, $full, LOCK_EX );
453
454	/** This action is documented in includes/class-cache.php */
455	do_action( 'xspeed_flat_file_written', $file, $full );
456
457	self::write_meta( $key );
458
459	// Static tree too, under the same gates finalize_buffer() applies —
460	// otherwise deferring the write would silently cost translated pages
461	// the web-server fast path and leave them on the slower drop-in.
462	if ( self::static_rewrite_allowed() && self::response_is_plain_html() ) {
463	self::store_static( $full );
464	}
465	}
466
467	public static function should_cache() {
468	// Reset first: a single request only reaches this once (the sole
469	// caller is maybe_start_cache()), but tests and any future caller
470	// must never inherit the previous request's verdict.
471	self::$status_header = '';
472	self::$bypass_reason = '';
473
474	$opts = Settings::get();
475	if ( empty( $opts['cache_enabled'] ) ) {
476	return self::bypass( 'cache-disabled' );
477	}
478
479	if ( is_user_logged_in() ) {
480	return self::bypass( 'logged-in' );
481	}
482
483	if ( is_admin() \|\| ( defined( 'DOING_AJAX' ) && DOING_AJAX ) \|\| ( defined( 'DOING_CRON' ) && DOING_CRON ) \|\| ( defined( 'REST_REQUEST' ) && REST_REQUEST ) ) {
484	return self::bypass( 'non-frontend' );
485	}
486
487	if ( defined( 'DONOTCACHEPAGE' ) && DONOTCACHEPAGE ) {
488	return self::bypass( 'donotcachepage' );
489	}
490
491	// All exclusion knobs now owned by CacheModule.
492	$cache_opts = Settings_Manager::get( 'cache' );
493
494	$method = isset( $_SERVER['REQUEST_METHOD'] ) ? strtoupper( sanitize_text_field( wp_unslash( $_SERVER['REQUEST_METHOD'] ) ) ) : '';
495	if ( 'GET' !== $method ) {
496	return self::bypass( 'non-get' );
497	}
498
499	// Search-results requests carry a `s` query param, which the
500	// query-string gate below would normally reject as "dynamic". An
501	// add-on (xspeed-pro search cache) can opt them in: when this is a
502	// genuine is_search() and the filter returns true, the `s` param is
503	// treated as cacheable (the search term goes into the cache key so
504	// different searches stay distinct — see cache_key()).
505	$cache_search = self::should_cache_search();
506
507	// Feed opt-in is resolved BEFORE the query-string gate so query-form
508	// feeds (/?feed=rss2, used on plain-permalink sites) aren't rejected
509	// as "dynamic" by that gate — the `feed` param is then allowed through
510	// just like the search `s` param. Feeds are excluded by default (the
511	// `/feed/` pattern in excluded_urls); an add-on (xspeed-pro feed cache)
512	// opts them back in via the filter. (FBS-82407 #4)
513	$is_feed_request = function_exists( 'is_feed' ) && is_feed();
514	/**
515	* Whether to cache the current feed request.
516	*
517	* Default false → feeds fall through to the normal URL-exclusion
518	* rules (so `/feed/` keeps them out). A listener returning true
519	* opts this feed request into caching.
520	*
521	* @param bool $cache_feed Whether to cache this feed request.
522	*/
523	$cache_feed = $is_feed_request && (bool) apply_filters( 'xspeed_should_cache_feed', false );
524
525	// Query string handling: anything OUTSIDE the ignored-params
526	// allow-list (utm_*, fbclid, gclid by default) means a unique
527	// request that we don't want to share with the canonical cache
528	// entry. Skip cache rather than poison the key.
529	//
530	// Parse the RAW query string, NOT a sanitize_text_field() copy:
531	// that filter strips percent-encoded octets (%XX), so `?%73=…`
532	// would lose its `s` key here while WordPress still decodes it to
533	// a search request — the gate would wave the request through and
534	// cache_key() would file the search page under the bare URL,
535	// letting an attacker poison the homepage cache with `/?%73=<spam>`.
536	// parse_str() does its own urldecoding, matching WP's own parse, and
537	// only the KEYS are used below (fed to Glob_Matcher → preg_match,
538	// never echoed or executed), so no sanitization is needed here.
539	$query_raw = isset( $_SERVER['QUERY_STRING'] ) ? wp_unslash( $_SERVER['QUERY_STRING'] ) : ''; // phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- see note above: parse_str() urldecodes to match WP; only keys are consumed, via preg_match, never output.
540	if ( '' !== $query_raw ) {
541	$ignored = is_array( $cache_opts['ignored_query_params'] ?? null ) ? $cache_opts['ignored_query_params'] : array();
542	parse_str( $query_raw, $params );
543	foreach ( $params as $key => $_ ) {
544	// Allow the search param through when search caching is on.
545	if ( $cache_search && 's' === $key ) {
546	continue;
547	}
548	// Allow query-form feed params through when feed caching opted
549	// this request in (?feed=rss2 / &withcomments=1 on feeds).
550	if ( $cache_feed && in_array( $key, array( 'feed', 'withcomments', 'withoutcomments' ), true ) ) {
551	continue;
552	}
553	if ( ! self::query_key_is_ignored( (string) $key, $ignored ) ) {
554	// Slug only — never the param name, which is attacker-
555	// controlled and would be reflected into a header.
556	return self::bypass( 'query-param' );
557	}
558	}
559	}
560
561	$request_uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
562	$path = (string) strtok( $request_uri, '?' );
563
564	$excluded_urls = is_array( $cache_opts['excluded_urls'] ?? null ) ? $cache_opts['excluded_urls'] : array();
565	if ( ! $cache_feed && Glob_Matcher::any_match( $excluded_urls, $path ) ) {
566	return self::bypass( 'excluded-url' );
567	}
568
569	// Cookie-based exclusion. We only check cookie NAMES (matching
570	// values would leak content-sensitive logic into the cache key
571	// rules); presence of any matching cookie name skips cache.
572	$excluded_cookies = is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array();
573	if ( ! empty( $excluded_cookies ) && ! empty( $_COOKIE ) ) {
574	foreach ( array_keys( $_COOKIE ) as $cookie_name ) {
575	if ( Glob_Matcher::any_match( $excluded_cookies, (string) $cookie_name ) ) {
576	return self::bypass( 'excluded-cookie' );
577	}
578	}
579	}
580
581	// User-agent bypass list. Substring match (not glob) since UA
582	// strings have so much variation that glob anchoring rarely
583	// helps and confuses users.
584	$bypass_uas = is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array();
585	if ( ! empty( $bypass_uas ) ) {
586	$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
587	foreach ( $bypass_uas as $needle ) {
588	if ( '' !== $needle && false !== stripos( $ua, (string) $needle ) ) {
589	return self::bypass( 'user-agent' );
590	}
591	}
592	}
593
594	// Per-post override (Phase 3.4). Honored only on singular
595	// post-context requests — archives / 404s / taxonomies use the
596	// global policy above.
597	if ( Cache_Rules::should_skip_for_post( Cache_Rules::current_post_id() ) ) {
598	return self::bypass( 'post-excluded' );
599	}
600
601	/**
602	* Final say on whether the current request is cacheable.
603	*
604	* Runs at template_redirect (full WP context), so listeners may use
605	* conditional tags (is_search(), is_feed(), is_404(),
606	* wp_is_maintenance_mode(), …). The core engine has already applied
607	* its own exclusion rules and reached `true`; a listener returning
608	* false vetoes caching for this request. This is the documented
609	* extension point add-ons (xspeed-pro) hook to add their own
610	* request-level cache policy without forking the engine.
611	*
612	* Note: this gates the WRITE side. The pre-WP drop-in
613	* (advanced-cache.php) cannot run PHP filters, so request types that
614	* must never be served from a stale file are handled by not
615	* writing them here and/or by purging — see the conflict notes in
616	* advanced-cache.php.
617	*
618	* @param bool $should_cache Whether to cache the current request.
619	*/
620	if ( ! apply_filters( 'xspeed_should_cache', true ) ) {
621	// One slug for every listener — a third-party callback name is
622	// not ours to put in a response header. Which listener vetoed is
623	// a WP_DEBUG-level question the filter itself can answer.
624	return self::bypass( 'filtered' );
625	}
626
627	return true;
628	}
629
630	/**
631	* Whether the current request is a 404 we may cache.
632	*
633	* True only when: it's a genuine main-query is_404(), an add-on opted
634	* in via `xspeed_should_cache_404` (default false), and the request
635	* isn't a transient 404 we must never freeze — maintenance mode or a
636	* 404 emitted while the DB/site is in an error state. The xspeed-pro
637	* 404 cache flips the filter; Free never caches 404s on its own.
638	*/
639	public static function should_cache_404(): bool {
640	if ( ! function_exists( 'is_404' ) \|\| ! is_404() ) {
641	return false;
642	}
643	// Never cache a 404 served because the site is down for
644	// maintenance — that screen disappears the moment maintenance
645	// ends, and a cached copy would outlive it.
646	if ( function_exists( 'wp_is_maintenance_mode' ) && wp_is_maintenance_mode() ) {
647	return false;
648	}
649
650	/**
651	* Whether to cache the current 404 response.
652	*
653	* Default false. A listener returning true opts the (genuine)
654	* 404 into the page cache, served back for any unknown URL under
655	* one generic key. The 404 status is preserved on the HIT.
656	*
657	* @param bool $cache_404 Whether to cache this 404.
658	*/
659	return (bool) apply_filters( 'xspeed_should_cache_404', false );
660	}
661
662	/**
663	* Whether the current request is an internal search-results page we
664	* may cache.
665	*
666	* True only when: it's a genuine main-query is_search() with a
667	* non-empty term, and an add-on opted in via `xspeed_should_cache_search`
668	* (default false). The search term is folded into the cache key (see
669	* search_term() / cache_key()) so different searches stay distinct.
670	* The xspeed-pro search cache flips the filter; Free never caches
671	* search results on its own.
672	*/
673	public static function should_cache_search(): bool {
674	if ( ! function_exists( 'is_search' ) \|\| ! is_search() ) {
675	return false;
676	}
677	// Empty search (`?s=`) renders the same as a normal archive and
678	// carries no term to key on — let it fall through to the usual
679	// rules rather than caching an ambiguous entry.
680	if ( '' === self::search_term() ) {
681	return false;
682	}
683
684	/**
685	* Whether to cache the current search-results request.
686	*
687	* Default false. A listener returning true opts the search page
688	* into the cache, keyed by the normalized search term.
689	*
690	* @param bool $cache_search Whether to cache this search request.
691	*/
692	return (bool) apply_filters( 'xspeed_should_cache_search', false );
693	}
694
695	/**
696	* The current request's normalized search term, or '' if none. Reads
697	* the raw `s` query param (works on the pre-WP drop-in path too, where
698	* get_search_query() isn't available), trims + lowercases so
699	* "WordPress" and "wordpress" share one entry, and collapses internal
700	* whitespace.
701	*/
702	public static function search_term(): string {
703	$raw = isset( $_GET['s'] ) ? sanitize_text_field( wp_unslash( $_GET['s'] ) ) : ''; // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- read-only cache-key derivation from a public search param; no state change.
704	$raw = trim( $raw );
705	if ( '' === $raw ) {
706	return '';
707	}
708	$raw = preg_replace( '/\s+/', ' ', $raw );
709	return function_exists( 'mb_strtolower' ) ? mb_strtolower( $raw ) : strtolower( $raw );
710	}
711
712	/**
713	* Is this query-string key on the ignored-params allow-list? Supports
714	* trailing-star globs (`utm_*` matches `utm_source`, `utm_medium`,
715	* etc.) so users don't have to enumerate every UTM variant.
716	*/
717	private static function query_key_is_ignored( string $key, array $ignored ): bool {
718	return Glob_Matcher::any_match( $ignored, $key );
719	}
720
721	public static function cache_key() {
722	$host = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : 'default';
723
724	// Cacheable 404s share ONE generic per-host entry — keying them by
725	// URL would let a scanner flood (millions of random paths) bloat
726	// the cache with identical 404 bodies. Both the write and the HIT
727	// lookup run through here, so they agree on the key automatically.
728	if ( self::should_cache_404() ) {
729	return md5( $host . '\|404' );
730	}
731
732	$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
733	// Strip the query string from the key so /post and /post?utm_*=…
734	// share the same cache entry. should_cache() above already
735	// rejected requests with non-ignored params, so by the time we
736	// build the key the only params left are safe to drop.
737	$uri = (string) strtok( $uri, '?' );
738
739	// Optional device bucket: when mobile_separate is on, mobile and
740	// desktop responses live in different cache files so themes that
741	// serve different HTML by device (AMP, WPtouch, Jetpack mobile)
742	// can't poison each other.
743	$device = '';
744	$opts = Settings_Manager::get( 'cache' );
745	if ( ! empty( $opts['mobile_separate'] ) ) {
746	$device = self::is_mobile_request() ? '\|m' : '\|d';
747	}
748
749	// Search-results requests fold the normalized term into the key so
750	// /?s=foo and /?s=bar get distinct entries (the query string is
751	// otherwise stripped above). Only added when search caching opted
752	// in, so non-search URLs are unaffected.
753	$search = self::should_cache_search() ? '\|s=' . self::search_term() : '';
754
755	// Query-form feeds (/?feed=rss2 vs /?feed=atom) share the same path
756	// once the query is stripped, so fold the feed type into the key to
757	// keep the flavors distinct. Pretty-permalink feeds (/feed/rss/) carry
758	// the type in $uri already and are unaffected. (FBS-82407 #4)
759	$feed = '';
760	if ( function_exists( 'is_feed' ) && is_feed() && function_exists( 'get_query_var' ) ) {
761	$feed_type = (string) get_query_var( 'feed' );
762	if ( '' !== $feed_type ) {
763	$feed = '\|feed=' . preg_replace( '/[^a-z0-9]/i', '', $feed_type );
764	}
765	}
766
767	return md5( $host . $uri . $device . $search . $feed );
768	}
769
770	/**
771	* Server-side mobile detection. Prefers WordPress's `wp_is_mobile()`
772	* which uses the same UA tokens as core (so our bucket aligns with
773	* whatever theme-side branching uses). Falls back to a tiny inline
774	* detector if wp_is_mobile() isn't loaded (e.g. the drop-in path).
775	*/
776	private static function is_mobile_request(): bool {
777	if ( function_exists( 'wp_is_mobile' ) ) {
778	return (bool) wp_is_mobile();
779	}
780	// Fallback for the rare context where wp_is_mobile() isn't loaded.
781	// Mirrors core's wp_is_mobile() EXACTLY — including the
782	// Sec-CH-UA-Mobile client hint it checks before UA tokens — so the
783	// bucket this picks matches whatever the engine's primary path (and
784	// the drop-in's own copy of this logic) would pick for the same
785	// request. Drift here re-introduces the cross-path key mismatch.
786	if ( isset( $_SERVER['HTTP_SEC_CH_UA_MOBILE'] ) ) {
787	return '?1' === $_SERVER['HTTP_SEC_CH_UA_MOBILE'];
788	}
789	$ua = isset( $_SERVER['HTTP_USER_AGENT'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ) ) : '';
790	if ( '' === $ua ) {
791	return false;
792	}
793	return (bool) preg_match( '/(Mobile\|Android\|Silk\/\|Kindle\|BlackBerry\|Opera Mini\|Opera Mobi)/i', $ua );
794	}
795
796	/**
797	* Filesystem-safe directory name for a host, or '' when unusable.
798	*
799	* The charset MUST match the static tree (store_static()) and the
800	* drop-in's own copy, or the paths disagree about where an entry lives.
801	* The colon of `host:port` is stripped: it is legal in a Host header but
802	* not portable in a path.
803	*
804	* @param string $host Raw host, e.g. from HTTP_HOST.
805	* @return string Safe directory segment, or '' if nothing usable remains.
806	*/
807	public static function host_dir( string $host ): string {
808	$host = str_replace( "\0", '', $host );
809	// Drop the port BEFORE filtering, or `example.com:8080` collapses to
810	// `example.com8080` — which both loses the boundary and could collide
811	// with a real host of that name.
812	$colon = strpos( $host, ':' );
813	if ( false !== $colon ) {
814	$host = substr( $host, 0, $colon );
815	}
816	$host = preg_replace( '/[^a-zA-Z0-9.\-]/', '', $host );
817	// Collapse any run of dots so no traversal sequence can survive the
818	// charset filter (`a/../b` would otherwise reduce to `a..b`).
819	$host = preg_replace( '/\.{2,}/', '.', (string) $host );
820	$host = trim( (string) $host, '.-' );
821	return '' === $host ? '' : $host;
822	}
823
824	/**
825	* The per-site bucket a cache entry belongs to: `<host>` on a single
826	* site, `<host>/<path-prefix>` for a subdirectory multisite blog.
827	*
828	* On multisite every blog shares one cache directory, and a flat md5
829	* filename carries no clue which site wrote it — so purging one subsite
830	* swept the whole network cold. (#6)
831	*
832	* Host alone is NOT enough: a subdirectory network (the common layout)
833	* puts every blog on the same host, so `example.com/` and
834	* `example.com/siteb/` would share a bucket and keep purging each other.
835	* The path prefix is what separates them, and it is derivable from the
836	* REQUEST_URI alone — which matters because the drop-in must compute
837	* this identical value before WordPress (and get_blog_details()) exist.
838	*
839	* Subdomain and domain-mapped networks differ by host already, so they
840	* get a bare host bucket and are unaffected.
841	*
842	* @param string $host Raw host.
843	* @param string $uri Raw REQUEST_URI (query string is ignored).
844	* @return string Bucket path, always non-empty.
845	*/
846	public static function site_bucket( string $host, string $uri ): string {
847	$dir = self::host_dir( $host );
848	if ( '' === $dir ) {
849	$dir = 'default';
850	}
851
852	$prefix = self::site_path_prefix();
853	return '' === $prefix ? $dir : $dir . '/' . $prefix;
854	}
855
856	/**
857	* The current blog's path prefix as a single safe segment ('' for the
858	* root blog or a non-multisite install). `/siteb/` becomes `siteb`;
859	* a nested `/a/b/` becomes `a-b` so the bucket stays one level deep.
860	*
861	* Written to a sidecar for the drop-in by sync_site_paths().
862	*/
863	public static function site_path_prefix(): string {
864	if ( ! function_exists( 'is_multisite' ) \|\| ! is_multisite() ) {
865	return '';
866	}
867	if ( function_exists( 'is_subdomain_install' ) && is_subdomain_install() ) {
868	return ''; // Hosts already differ; no prefix needed.
869	}
870	$path = function_exists( 'get_blog_details' ) ? (string) get_blog_details()->path : '/';
871	return self::path_prefix_segment( $path );
872	}
873
874	/**
875	* The bucket an arbitrary URL's cache entry lives in.
876	*
877	* `site_bucket()` answers for the CURRENT request; this answers for a URL
878	* that may belong to another blog entirely — which is what a per-URL purge
879	* is usually doing (WP-CLI, cron, the MCP tool, a network-admin action).
880	*
881	* The blog is resolved from the URL itself: on a subdirectory network
882	* `get_blog_details()` is asked which blog owns `<host><path>`, and its
883	* registered path becomes the prefix. Deriving the prefix from the URL's
884	* first path segment directly would be wrong — `/shop/` on the main blog
885	* is a page, not a subsite, and would send the purge into a bucket that
886	* does not exist. (QA B2 on #166)
887	*
888	* @param string $host Host of the URL being purged.
889	* @param string $path Path of the URL being purged.
890	* @return string Bucket path, always non-empty.
891	*/
892	public static function bucket_for_url( string $host, string $path ): string {
893	$dir = self::host_dir( $host );
894	if ( '' === $dir ) {
895	$dir = 'default';
896	}
897
898	if ( ! function_exists( 'is_multisite' ) \|\| ! is_multisite() ) {
899	return $dir;
900	}
901	if ( function_exists( 'is_subdomain_install' ) && is_subdomain_install() ) {
902	return $dir; // Hosts already differ; no prefix.
903	}
904	if ( ! function_exists( 'get_blog_details' ) ) {
905	return $dir;
906	}
907
908	// Longest registered blog path that prefixes this URL wins, so
909	// `/one/2026/post/` resolves to blog `/one/` and not to the root blog.
910	$blog = self::blog_for_path( $host, $path );
911	if ( null === $blog ) {
912	return $dir;
913	}
914	$prefix = self::path_prefix_segment( (string) $blog );
915	return '' === $prefix ? $dir : $dir . '/' . $prefix;
916	}
917
918	/**
919	* The registered path of the blog that owns `<host><path>`, or null.
920	*
921	* Uses get_blog_details() with a domain/path pair rather than scanning
922	* every blog, so a large network costs one lookup per candidate segment
923	* instead of a full table read.
924	*/
925	private static function blog_for_path( string $host, string $path ): ?string {
926	$segments = array_values( array_filter( explode( '/', trim( $path, '/' ) ) ) );
927
928	// Try the longest candidate first: /a/b/ before /a/ before /.
929	for ( $take = min( count( $segments ), 2 ); $take >= 1; $take-- ) {
930	$candidate = '/' . implode( '/', array_slice( $segments, 0, $take ) ) . '/';
931	$details = get_blog_details(
932	array(
933	'domain' => $host,
934	'path' => $candidate,
935	),
936	false
937	);
938	if ( $details && ! empty( $details->path ) ) {
939	return (string) $details->path;
940	}
941	}
942	return null;
943	}
944
945	/**
946	* Normalise a blog path ('/', '/siteb/', '/a/b/') into a single
947	* filesystem-safe segment. Shared with the drop-in's copy.
948	*/
949	public static function path_prefix_segment( string $path ): string {
950	$path = trim( str_replace( "\0", '', $path ), '/' );
951	if ( '' === $path ) {
952	return '';
953	}
954	$path = preg_replace( '/[^a-zA-Z0-9._\-\/]/', '', $path );
955	$path = str_replace( '/', '-', (string) $path );
956	return trim( (string) $path, '.-' );
957	}
958
959	/**
960	* The current blog's path as the static tree stores it — real slashes
961	* preserved, because that tree mirrors the URL
962	* (`xspeed-static/{host}{request_uri}/index.html`) rather than using a
963	* single flattened segment. '' for a root blog / single site.
964	*/
965	public static function site_path_raw(): string {
966	if ( ! function_exists( 'is_multisite' ) \|\| ! is_multisite() ) {
967	return '';
968	}
969	if ( function_exists( 'is_subdomain_install' ) && is_subdomain_install() ) {
970	return '';
971	}
972	$path = function_exists( 'get_blog_details' ) ? (string) get_blog_details()->path : '/';
973	$path = trim( str_replace( "\0", '', $path ), '/' );
974	if ( '' === $path ) {
975	return '';
976	}
977	$path = preg_replace( '#[^a-zA-Z0-9._\-/]#', '', $path );
978	return trim( (string) $path, '/' );
979	}
980
981	/**
982	* Static-tree root for the current site: `<host>` plus the blog's real
983	* path. Mirrors store_static()'s layout so a scoped purge deletes
984	* exactly this blog's pages.
985	*/
986	public static function current_static_scope(): string {
987	// Same switch_to_blog() caveat as current_host_dir() — see current_host().
988	$dir = self::host_dir( self::current_host() );
989	if ( '' === $dir ) {
990	$dir = 'default';
991	}
992	$path = self::site_path_raw();
993	return '' === $path ? $dir : $dir . '/' . $path;
994	}
995
996	/**
997	* The bucket for the CURRENT request. Never empty, so an entry is never
998	* written to the tree root (which is what the unscoped sweeps used to
999	* delete indiscriminately).
1000	*/
1001	public static function current_host_dir(): string {
1002	$host = self::current_host();
1003	$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '/';
1004	return self::site_bucket( $host, $uri );
1005	}
1006
1007	/**
1008	* The host the CURRENT blog is served from.
1009	*
1010	* Deliberately NOT just $_SERVER['HTTP_HOST']: inside a
1011	* switch_to_blog() the request header still names whichever site is
1012	* serving the admin screen, while the cache entries we want belong to
1013	* the switched-to blog. On a subdomain network the host IS the bucket,
1014	* so reading the header there would make Pro's per-site "purge this
1015	* site" button clear the network admin's own cache instead — the very
1016	* bug this scoping exists to fix, surviving in one topology.
1017	*
1018	* get_blog_details() follows the switch, so prefer it whenever we are
1019	* on multisite, and fall back to the request header otherwise.
1020	*/
1021	public static function current_host(): string {
1022	if ( function_exists( 'is_multisite' ) && is_multisite() && function_exists( 'get_blog_details' ) ) {
1023	$details = get_blog_details();
1024	if ( $details && ! empty( $details->domain ) ) {
1025	return (string) $details->domain;
1026	}
1027	}
1028
1029	if ( isset( $_SERVER['HTTP_HOST'] ) ) {
1030	return sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) );
1031	}
1032
1033	/*
1034	* No request header — WP-CLI, or WP-Cron driven by system cron.
1035	*
1036	* Returning '' here made the bucket resolve to the literal `default`
1037	* while HTTP requests were writing to `<host>/`, so a scheduled purge
1038	* swept an empty directory and reported success, and get_stats()
1039	* reported 0 cached pages on a site with a full cache. That is the
1040	* normal setup on any host running DISABLE_WP_CRON, which is most of
1041	* them. Fall back to the site's own registered host. (QA D4 on #166)
1042	*/
1043	if ( function_exists( 'home_url' ) ) {
1044	$parts = function_exists( 'wp_parse_url' ) ? wp_parse_url( home_url( '/' ) ) : parse_url( home_url( '/' ) ); // phpcs:ignore WordPress.WP.AlternativeFunctions.parse_url_parse_url -- early-boot fallback only.
1045	if ( is_array( $parts ) && ! empty( $parts['host'] ) ) {
1046	return (string) $parts['host'];
1047	}
1048	}
1049
1050	return '';
1051	}
1052
1053	/**
1054	* Ensure the current site's cache directory exists, with the silence
1055	* index in both it and the shared root. Returns the directory.
1056	*/
1057	public static function ensure_host_dir(): string {
1058	$dir = XSPEED_CACHE_DIR . '/' . self::current_host_dir();
1059	if ( ! file_exists( XSPEED_CACHE_DIR ) ) {
1060	wp_mkdir_p( XSPEED_CACHE_DIR );
1061	self::write_silence( XSPEED_CACHE_DIR );
1062	}
1063	if ( ! file_exists( $dir ) ) {
1064	wp_mkdir_p( $dir );
1065	self::write_silence( $dir );
1066	}
1067	return $dir;
1068	}
1069
1070	public static function cache_file_for( $key ) {
1071	return XSPEED_CACHE_DIR . '/' . self::current_host_dir() . '/' . $key . '.html';
1072	}
1073
1074	/**
1075	* If a precompressed Brotli sibling (`<file>.br`) exists and the client
1076	* advertises `Accept-Encoding: br`, emit the Brotli response headers and
1077	* return the `.br` path to stream. Returns null to fall through to the
1078	* plain file. Keeps the PHP serve path in parity with the web server's
1079	* static .br serving (mod_brotli / ngx_brotli rewrite).
1080	*
1081	* Free has no Brotli logic of its own — this only fires when an add-on
1082	* (the Pro Brotli module) actually wrote the .br, so it's a safe no-op
1083	* on Free-only installs.
1084	*
1085	* @param string $file Absolute path to the cached .html file.
1086	* @return string\|null The .br path to stream, or null to serve $file.
1087	*/
1088	public static function maybe_serve_brotli( string $file ): ?string {
1089	if ( headers_sent() ) {
1090	return null;
1091	}
1092	$accept = isset( $_SERVER['HTTP_ACCEPT_ENCODING'] )
1093	? strtolower( sanitize_text_field( wp_unslash( $_SERVER['HTTP_ACCEPT_ENCODING'] ) ) )
1094	: '';
1095	// Match `br` as a token (comma/space delimited), not a substring, so
1096	// a hypothetical "xbr" encoding can't false-positive.
1097	if ( ! preg_match( '/(^\|[\s,])br([\s,;]\|$)/', $accept ) ) {
1098	return null;
1099	}
1100	$br = $file . '.br';
1101	if ( ! is_string( $br ) \|\| ! file_exists( $br ) \|\| ! is_readable( $br ) ) {
1102	return null;
1103	}
1104	header( 'Content-Encoding: br' );
1105	header( 'Vary: Accept-Encoding', false );
1106	// The byte length changes for the compressed body — drop any
1107	// Content-Length the caller may have set so the stream isn't
1108	// truncated/padded. readfile() lets the SAPI set the right length.
1109	header_remove( 'Content-Length' );
1110	return $br;
1111	}
1112
1113	/**
1114	* Sidecar metadata file for a cache entry. Holds response bits the HIT
1115	* path must replay — Content-Type (cached feeds → application/rss+xml,
1116	* sitemaps → text/xml) and status (a cached 404 must serve 404, not
1117	* 200). JSON, one tiny file per entry, written only when there's
1118	* something non-default to replay.
1119	*/
1120	public static function cache_meta_for( $key ) {
1121	return XSPEED_CACHE_DIR . '/' . self::current_host_dir() . '/' . $key . '.meta';
1122	}
1123
1124	/**
1125	* Read the .meta sidecar for a cache entry as an array, or [] if none.
1126	* Keys: 'content_type' (string), 'status' (int), 'ttl' (int seconds).
1127	* Used on the HIT path to replay content-type/status before streaming
1128	* the file, and by Cache_GC to age an entry by its own TTL rather than
1129	* the global one — hence public.
1130	*/
1131	public static function read_meta( $key ): array {
1132	$meta_file = self::cache_meta_for( $key );
1133	if ( ! file_exists( $meta_file ) ) {
1134	return array();
1135	}
1136	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents -- our own cache dir; WP_Filesystem needs admin creds unavailable on a frontend HIT.
1137	$raw = file_get_contents( $meta_file );
1138	$data = json_decode( (string) $raw, true );
1139	return is_array( $data ) ? $data : array();
1140	}
1141
1142	/**
1143	* Conditional-GET support for a cache HIT. Emits Last-Modified + ETag
1144	* derived from the cache file's mtime, and — when the request's
1145	* If-Modified-Since / If-None-Match still match — sends 304 Not Modified
1146	* and returns true (caller should exit without a body). Returns false to
1147	* proceed with a normal 200 body. Lets aggregators/browsers skip
1148	* re-downloading an unchanged cached response. (FBS-82407 #5)
1149	*
1150	* @param string $file Absolute path to the cache .html file.
1151	* @return bool True when a 304 was sent.
1152	*/
1153	public static function serve_not_modified( string $file ): bool {
1154	$mtime = (int) filemtime( $file );
1155	if ( $mtime <= 0 ) {
1156	return false;
1157	}
1158	$last_modified = gmdate( 'D, d M Y H:i:s', $mtime ) . ' GMT';
1159	$etag = '"' . md5( $file . '\|' . $mtime ) . '"';
1160	header( 'Last-Modified: ' . $last_modified );
1161	header( 'ETag: ' . $etag );
1162
1163	$ims = isset( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ? trim( sanitize_text_field( wp_unslash( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ) ) : '';
1164	$inm = isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) ? trim( sanitize_text_field( wp_unslash( $_SERVER['HTTP_IF_NONE_MATCH'] ) ) ) : '';
1165
1166	$etag_match = '' !== $inm && false !== strpos( $inm, $etag );
1167	$time_match = '' !== $ims && ( strtotime( $ims ) >= $mtime );
1168
1169	if ( $etag_match \|\| $time_match ) {
1170	if ( function_exists( 'http_response_code' ) ) {
1171	http_response_code( 304 );
1172	}
1173	return true;
1174	}
1175	return false;
1176	}
1177
1178	public static function is_expired( $file ) {
1179	// cache_expiry now owned by CacheModule; per-post override
1180	// (Phase 3.4) shrinks the TTL further when the editor set one.
1181	$opts = Settings_Manager::get( 'cache' );
1182	$max_age = (int) $opts['cache_expiry'] * HOUR_IN_SECONDS;
1183	$post_override = Cache_Rules::expiry_override_seconds_for_post( Cache_Rules::current_post_id() );
1184	if ( null !== $post_override ) {
1185	$max_age = $post_override;
1186	}
1187
1188	/**
1189	* Filter the max-age (seconds) for the current cache entry.
1190	*
1191	* Lets an add-on apply a request-type-specific TTL — e.g. the
1192	* xspeed-pro feed cache gives feeds a longer expiry than pages,
1193	* since aggregators tolerate more staleness. Return seconds.
1194	*
1195	* @param int $max_age Computed max-age in seconds.
1196	*/
1197	$max_age = (int) apply_filters( 'xspeed_cache_max_age', $max_age );
1198
1199	// A missing file is "expired" — the caller should re-render. Guard
1200	// filemtime() rather than letting it warn: callers legitimately ask
1201	// about a file that isn't there (Pro's predictive warmer probes for
1202	// freshness, and Cache_GC can collect an entry between the check and
1203	// the read), and on a site with WP_DEBUG the warning is noise.
1204	$mtime = file_exists( $file ) ? filemtime( $file ) : false;
1205	if ( false === $mtime ) {
1206	return true;
1207	}
1208
1209	return ( time() - (int) $mtime ) > $max_age;
1210	}
1211
1212	/**
1213	* Accumulator for the full response body across all output-handler phases.
1214	*
1215	* PHP invokes an ob_start() callback once per flush, and each invocation
1216	* only receives the chunk produced since the previous flush. If anything
1217	* during the render calls `ob_flush()` or `flush()` (some themes, lazy-
1218	* load plugins, AMP, etc. do), the final-phase call would otherwise only
1219	* see the tail of the page — and we'd cache a truncated response that
1220	* gets served repeatedly until purge. We accumulate every chunk here so
1221	* the cache file always reflects the complete page.
1222	*
1223	* @var string
1224	*/
1225	private static $accumulated = '';
1226
1227	public static function finalize_buffer( $buffer, $phase = PHP_OUTPUT_HANDLER_FINAL ) {
1228	self::$accumulated .= $buffer;
1229
1230	// On non-final phases (mid-request flushes), pass the current chunk
1231	// through to the client unmodified and keep collecting. The WP 6.9
1232	// filter path always passes the full body in one shot with the
1233	// default $phase, so it falls straight through to the final block.
1234	$is_final = ( $phase & ( PHP_OUTPUT_HANDLER_FINAL \| PHP_OUTPUT_HANDLER_END ) ) !== 0;
1235	if ( ! $is_final ) {
1236	return $buffer;
1237	}
1238
1239	$full = self::$accumulated;
1240	self::$accumulated = '';
1241
1242	if ( strlen( $full ) < 255 ) {
1243	return $buffer;
1244	}
1245
1246	// Status gate. We cache 200 by default. A 404 may be cached too,
1247	// but only when an add-on (xspeed-pro 404 cache) opts in for a
1248	// genuine is_404() — never a transient 404 (maintenance screen,
1249	// DB error, or a 404 emitted outside the main query), which would
1250	// otherwise be frozen until purge. Any other status is skipped.
1251	$status = function_exists( 'http_response_code' ) ? (int) http_response_code() : 200;
1252	if ( 200 !== $status ) {
1253	if ( 404 !== $status \|\| ! self::should_cache_404() ) {
1254	return $buffer;
1255	}
1256	}
1257
1258	// If no mid-request flush happened, $buffer === $full and we can
1259	// safely minify the on-wire bytes too. Otherwise earlier chunks have
1260	// already been sent unminified, so we minify only what goes to disk —
1261	// the first visitor sees unminified HTML, every cache hit after that
1262	// is minified.
1263	$single_chunk = ( $buffer === $full );
1264
1265	/**
1266	* Filter: xspeed_cache_final_html
1267	*
1268	* Last chance to transform the fully-rendered page HTML before it is
1269	* minified and written to the cache file. Runs on cache MISS only, so
1270	* whatever a listener injects here is baked into the cached HTML and
1271	* replayed on every subsequent HIT (the drop-in short-circuits before
1272	* PHP on a HIT — a wp_head hook would never fire there).
1273	*
1274	* The Preload module uses this to inject the LCP-image <link rel=preload>
1275	* + preconnect hints and add fetchpriority="high" to the hero <img>.
1276	* Keep listeners fast and idempotent; this is the on-wire body.
1277	*
1278	* @param string $full Complete page HTML.
1279	*/
1280	$full = (string) apply_filters( 'xspeed_cache_final_html', $full );
1281	if ( $single_chunk ) {
1282	$buffer = $full;
1283	}
1284
1285	// minify_html now owned by the Minify module; read through the
1286	// module's storage so this stays consistent with the engine that
1287	// applies CSS/JS minification.
1288	$minify_opts = Settings_Manager::get( 'minify' );
1289	if ( ! empty( $minify_opts['minify_html'] ) ) {
1290	$full = Minifier::minify_html( $full );
1291	if ( $single_chunk ) {
1292	$buffer = $full;
1293	}
1294	}
1295
1296	// Per-site directory — see ensure_host_dir(). (#6)
1297	self::ensure_host_dir();
1298
1299	// Path safety: cache_file_for() builds
1300	// `XSPEED_CACHE_DIR . '/' . <host> . '/' . $key . '.html'` where $key
1301	// comes from md5() — guaranteed to be exactly 32 lowercase hex chars —
1302	// and <host> is filtered by host_dir() to [A-Za-z0-9.-] with leading
1303	// dots trimmed, so no traversal sequence ('..', '/', null byte, etc.)
1304	// can appear in either segment. The write is therefore always inside
1305	// XSPEED_CACHE_DIR.
1306	$key = self::cache_key();
1307	$file = self::cache_file_for( $key );
1308
1309	// A render-time translation plugin (TranslatePress) wraps our buffer,
1310	// so the bytes we hold here are still UNTRANSLATED — its callback has
1311	// not run yet, and writing now would cache English under a French URL
1312	// and bake in its internal #TRPLINKPROCESSED markers. Hand off to
1313	// shutdown, where the outer buffer has already translated, and let
1314	// the pass-through below deliver this request untouched.
1315	if ( self::translation_plugin_active() ) {
1316	self::$deferred_key = $key;
1317	// Reaching here means finalize_buffer() ran to completion: the
1318	// status gate passed, should_cache() said yes, and PHP handed us
1319	// the whole buffer. A wp_die() or exit() mid-render unwinds the
1320	// buffer stack WITHOUT calling this callback, so the flag stays
1321	// false and the shutdown writer declines — see the guard there.
1322	self::$render_completed = true;
1323	// A PHP shutdown function, not a WP `shutdown` action: this must
1324	// run after the output-buffer stack has unwound, and WP's
1325	// shutdown action fires while our outer buffer is still open.
1326	register_shutdown_function( array( __CLASS__, 'write_deferred_translated_cache' ) );
1327	return $buffer;
1328	}
1329
1330	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin context for credentials; cache writes happen on frontend requests where it's unavailable.
1331	file_put_contents( $file, $full, LOCK_EX );
1332
1333	/**
1334	* Fires after the flat hash cache file ({md5}.html) is written.
1335	*
1336	* Mirror of `xspeed_static_file_written` for the flat cache. The PHP
1337	* serve path (Cache::maybe_serve_brotli / the drop-in) serves THIS
1338	* file and looks for a `{md5}.html.br` sibling — which only the Pro
1339	* Brotli listener on this hook writes. Without it the .br sibling was
1340	* never created and the PHP path could never serve Brotli (FBS-83039,
1341	* Blocker 2): the static-tree .br (written on xspeed_static_file_written)
1342	* lives in a different cache layout the PHP path never reads.
1343	*
1344	* @param string $file Absolute path to the flat cache file just written.
1345	* @param string $full The HTML written to it.
1346	*/
1347	do_action( 'xspeed_flat_file_written', $file, $full );
1348
1349	// Persist a non-default Content-Type so the HIT path can replay it
1350	// (cached feeds must serve application/rss+xml, not text/html).
1351	// Only written when the response set a content-type other than
1352	// the HTML default — pages don't pay for an extra file.
1353	self::write_meta( $key );
1354
1355	// Static-cache tree (xspeed-static/{host}{path}/index.html). The
1356	// .htaccess rewrite block serves this file directly via the web
1357	// server, bypassing PHP for ~3-5× lower TTFB vs the drop-in path.
1358	// store_static() returns silently on any path/permission issue —
1359	// the drop-in remains the safety net.
1360	//
1361	// Skip it entirely when mobile_separate is on: the rewrite is
1362	// disabled in that mode (static_rewrite_allowed()), so a static file
1363	// would only be dead weight — and a device-blind one at that.
1364	// Skip the static-tree write for responses the web server can't replay
1365	// correctly: a non-200 status (a cached 404 would be served as a soft
1366	// 200, FBS-82406) or a non-HTML content-type (a cached feed would go
1367	// out as text/html, FBS-82407). The web server serves these .html files
1368	// directly with no PHP, so there's no .meta replay — keep them on the
1369	// drop-in / PHP path instead, which DOES replay status + content-type.
1370	if ( self::static_rewrite_allowed() && self::response_is_plain_html() ) {
1371	self::store_static( $full );
1372	}
1373
1374	return $buffer;
1375	}
1376
1377	/**
1378	* Write the current response to the static-cache tree at
1379	* `xspeed-static/{host}{request_uri}/index.html`. The web-server
1380	* rewrite block points at this path so cache hits skip PHP
1381	* entirely. Caller already minified/finalized $html.
1382	*
1383	* Path safety: $host is restricted to a `[a-zA-Z0-9.\-]` allowlist;
1384	* $uri has its query string stripped, null bytes removed, '..'
1385	* sequences collapsed, and after concatenation we verify the
1386	* resolved real path stays inside XSPEED_CACHE_STATIC_DIR before
1387	* any write. Anything off the happy path returns silently.
1388	*
1389	* INVARIANT — the static tree is keyed by `{host}{path}` and NOTHING
1390	* else, and both generated rewrites refuse any request that carries a
1391	* query string at all (`RewriteCond %{QUERY_STRING} ^$` on Apache,
1392	* `if ($args)` in nginx_snippet()). So a response may only be stored
1393	* here when cache_key() adds no discriminator beyond `{host}{path}`:
1394	* a query-keyed entry can never be served from here, only mis-served
1395	* as the bare path. Any future opt-in that folds a query param into the
1396	* key needs a guard below, exactly like the search one.
1397	*/
1398	private static function store_static( string $html ): void {
1399	// Search results are keyed by term in cache_key() (`\|s=<term>`) but
1400	// carry the path of whatever URL was searched from — for the usual
1401	// `/?s=<term>` that path is `/`. Writing them here would file the
1402	// results page as `{host}/index.html` and the web server would serve
1403	// it to every visitor as the homepage: an unauthenticated visitor
1404	// poisons the front page with one request. Searches stay on the
1405	// drop-in, which replays the term-keyed entry correctly. (#191)
1406	//
1407	// This is a superset of the query-string check the exclusion gate
1408	// does: it also covers `/?%73=<term>`, which decodes to the same
1409	// search (the shape #109 fixed on the gate side).
1410	if ( self::should_cache_search() ) {
1411	return;
1412	}
1413
1414	$host = isset( $_SERVER['HTTP_HOST'] ) ? sanitize_text_field( wp_unslash( $_SERVER['HTTP_HOST'] ) ) : '';
1415	$uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
1416	$host = preg_replace( '/[^a-zA-Z0-9.\-]/', '', $host );
1417	$uri = str_replace( "\0", '', $uri );
1418	$uri = (string) strtok( $uri, '?' );
1419	if ( '' === $host \|\| '' === $uri ) {
1420	return;
1421	}
1422	// Collapse any traversal sequences before path resolution.
1423	$uri = preg_replace( '#/+#', '/', $uri );
1424	if ( false !== strpos( $uri, '..' ) ) {
1425	return;
1426	}
1427
1428	$base = rtrim( XSPEED_CACHE_STATIC_DIR, '/' );
1429	$dir = $base . '/' . $host . rtrim( $uri, '/' );
1430	$file = $dir . '/index.html';
1431
1432	// Resolve the parent against the cache root to be sure the
1433	// final path is inside our tree even if the OS does anything
1434	// funny with multi-byte sequences.
1435	$base_real = realpath( WP_CONTENT_DIR );
1436	if ( false === $base_real \|\| 0 !== strpos( $base, $base_real ) ) {
1437	return;
1438	}
1439
1440	if ( ! file_exists( $dir ) ) {
1441	wp_mkdir_p( $dir );
1442	}
1443	if ( ! is_dir( $dir ) ) {
1444	return;
1445	}
1446	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- Same rationale as the flat-hash cache write above: WP_Filesystem isn't available on frontend requests, and the cache write must happen during shutdown.
1447	$written = file_put_contents( $file, $html, LOCK_EX );
1448
1449	if ( false !== $written ) {
1450	/**
1451	* Fires after a static cache file (index.html) is written.
1452	*
1453	* The extension point for serving pre-compressed siblings:
1454	* the xspeed-pro Brotli module writes `index.html.br` next to
1455	* the file here so the web server's static rewrite can serve a
1456	* Brotli copy to clients that advertise `Accept-Encoding: br`,
1457	* falling back to GZIP / the plain file otherwise. No core
1458	* behavior depends on a listener being present.
1459	*
1460	* @param string $file Absolute path to the static cache file just written.
1461	* @param string $html The HTML written to it.
1462	*/
1463	do_action( 'xspeed_static_file_written', $file, $html );
1464	}
1465	}
1466
1467	/**
1468	* Write the .meta sidecar for a cache entry when the response carries
1469	* anything the HIT path must replay beyond a plain 200 text/html:
1470	* - a non-HTML Content-Type (cached feeds → application/rss+xml,
1471	* sitemaps → text/xml, …), and/or
1472	* - a non-200 status (a cached 404 must serve 404, not 200).
1473	*
1474	* Ordinary 200 text/html pages get NO .meta file, so the common path
1475	* stays a single write.
1476	*
1477	* @param string $key Cache key for the current request.
1478	*/
1479	/**
1480	* True only for a plain 200 text/html response — the only kind the
1481	* web-server static tree can serve correctly (it streams the .html with
1482	* no PHP, so it can't replay a 404 status or a feed Content-Type). Used
1483	* to gate store_static() so cached 404s / feeds stay on the replay-capable
1484	* drop-in / PHP path. (FBS-82406, FBS-82407)
1485	*/
1486	private static function response_is_plain_html(): bool {
1487	$status = function_exists( 'http_response_code' ) ? (int) http_response_code() : 200;
1488	if ( 200 !== $status && $status > 0 ) {
1489	return false;
1490	}
1491	foreach ( headers_list() as $header ) {
1492	if ( 0 === stripos( $header, 'content-type:' ) ) {
1493	$ct = trim( substr( $header, strlen( 'content-type:' ) ) );
1494	if ( '' !== $ct && false === stripos( $ct, 'text/html' ) ) {
1495	return false;
1496	}
1497	}
1498	}
1499	return true;
1500	}
1501
1502	private static function write_meta( string $key ): void {
1503	$content_type = '';
1504	foreach ( headers_list() as $header ) {
1505	if ( 0 === stripos( $header, 'content-type:' ) ) {
1506	$content_type = trim( substr( $header, strlen( 'content-type:' ) ) );
1507	}
1508	}
1509	$status = function_exists( 'http_response_code' ) ? (int) http_response_code() : 200;
1510
1511	$meta = array();
1512	$is_default_type = ( '' === $content_type \|\| false !== stripos( $content_type, 'text/html' ) );
1513	if ( ! $is_default_type ) {
1514	$meta['content_type'] = $content_type;
1515	}
1516	if ( 200 !== $status && $status > 0 ) {
1517	$meta['status'] = $status;
1518	}
1519
1520	// Per-content TTL (seconds). The drop-in and static fast paths can't
1521	// call is_expired() / the xspeed_cache_max_age filter (they run before
1522	// WP), so persist the resolved max-age here whenever it differs from
1523	// the plain page TTL — e.g. the Pro feed cache's 12h vs the 24h page
1524	// default. The fast paths read this to expire correctly. (FBS-82407)
1525	$opts = Settings_Manager::get( 'cache' );
1526	$default_ttl = (int) $opts['cache_expiry'] * HOUR_IN_SECONDS;
1527	$ttl = (int) apply_filters( 'xspeed_cache_max_age', $default_ttl );
1528	if ( $ttl > 0 && $ttl !== $default_ttl ) {
1529	$meta['ttl'] = $ttl;
1530	}
1531
1532	// Nothing to replay → no sidecar.
1533	if ( empty( $meta ) ) {
1534	return;
1535	}
1536
1537	$payload = wp_json_encode( $meta );
1538	if ( false === $payload ) {
1539	return;
1540	}
1541	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- our own cache dir; WP_Filesystem needs admin creds unavailable on a frontend shutdown write.
1542	file_put_contents( self::cache_meta_for( $key ), $payload, LOCK_EX );
1543	}
1544
1545	/**
1546	* @param string $cause Free-form human reason. Recorded in the
1547	* Activity log to give users context (e.g.
1548	* 'post saved', 'settings change', 'manual',
1549	* 'theme switch').
1550	*/
1551	/**
1552	* Purge the cache entries for ONE URL — every variant of it: the
1553	* flat-hash entry (+ .meta / .html.br siblings), both device buckets
1554	* (mobile_separate keys them separately), both trailing-slash forms,
1555	* and the static-tree index.html (+ .br) the server rewrite serves.
1556	* The rest of the cache is untouched — this is the surgical
1557	* alternative to purge_all for "I just edited this one page".
1558	*
1559	* @param string $url Absolute URL, or site-relative path ("/about/").
1560	* @param string $cause Who asked, for the purge log. See purge_all().
1561	* @return int Number of cache files removed.
1562	*/
1563	public static function purge_url( string $url, string $cause = 'manual' ): int {
1564	$parts = function_exists( 'wp_parse_url' ) ? wp_parse_url( $url ) : parse_url( $url ); // phpcs:ignore WordPress.WP.AlternativeFunctions.parse_url_parse_url -- fallback for early-boot contexts only.
1565	if ( ! is_array( $parts ) ) {
1566	return 0;
1567	}
1568	$host = isset( $parts['host'] ) ? strtolower( (string) $parts['host'] ) : '';
1569	if ( '' === $host && function_exists( 'home_url' ) ) {
1570	$home = function_exists( 'wp_parse_url' ) ? wp_parse_url( home_url( '/' ) ) : parse_url( home_url( '/' ) ); // phpcs:ignore WordPress.WP.AlternativeFunctions.parse_url_parse_url -- see above.
1571	$host = is_array( $home ) && isset( $home['host'] ) ? strtolower( (string) $home['host'] ) : '';
1572	}
1573	if ( '' === $host ) {
1574	return 0;
1575	}
1576	$path = isset( $parts['path'] ) ? (string) $parts['path'] : '/';
1577	$path = '/' . ltrim( $path, '/' );
1578	if ( false !== strpos( $path, '..' ) ) {
1579	return 0;
1580	}
1581
1582	// The cache key preserves REQUEST_URI's trailing-slash form, so
1583	// purge both. Root stays a single '/'.
1584	$forms = array( $path );
1585	if ( '/' !== $path ) {
1586	$forms[] = rtrim( $path, '/' );
1587	$forms[] = rtrim( $path, '/' ) . '/';
1588	}
1589	$forms = array_unique( $forms );
1590
1591	/*
1592	* Entries live under the bucket they were written for, and this URL's
1593	* site may not be the one serving THIS request (a cross-site purge on
1594	* multisite, WP-CLI, or cron). Build the directory from the URL's own
1595	* host AND path. (#6)
1596	*
1597	* Host alone is wrong on a subdirectory network: `store()` wrote to
1598	* `<host>/<prefix>/`, so looking in `<host>/` found nothing and the
1599	* call reported "already cold" while the page kept serving HIT — a
1600	* false success, which is worse than an error. The prefix has to come
1601	* from the URL being purged rather than from the current blog, because
1602	* the caller is usually purging some OTHER site. (QA B2 on #166)
1603	*/
1604	$base = XSPEED_CACHE_DIR . '/' . self::bucket_for_url( $host, $path );
1605
1606	$count = 0;
1607	foreach ( $forms as $uri ) {
1608	// '' = mobile_separate off; '\|m' / '\|d' = the device buckets.
1609	foreach ( array( '', '\|m', '\|d' ) as $device ) {
1610	$key = md5( $host . $uri . $device );
1611	$file = $base . '/' . $key . '.html';
1612	if ( is_file( $file ) ) {
1613	wp_delete_file( $file );
1614	++$count;
1615	}
1616	foreach ( array( $base . '/' . $key . '.meta', $file . '.br' ) as $sidecar ) {
1617	if ( is_file( $sidecar ) ) {
1618	wp_delete_file( $sidecar );
1619	}
1620	}
1621	}
1622	}
1623
1624	// Static tree (served directly by the nginx/.htaccess rewrite).
1625	if ( defined( 'XSPEED_CACHE_STATIC_DIR' ) ) {
1626	$dir = rtrim( XSPEED_CACHE_STATIC_DIR, '/' ) . '/' . $host . ( '/' === $path ? '' : rtrim( $path, '/' ) );
1627	$file = $dir . '/index.html';
1628	if ( is_file( $file ) ) {
1629	wp_delete_file( $file );
1630	++$count;
1631	}
1632	if ( is_file( $file . '.br' ) ) {
1633	wp_delete_file( $file . '.br' );
1634	}
1635	}
1636
1637	if ( $count > 0 ) {
1638	Cache_Inventory::invalidate();
1639	Activity_Log::record(
1640	'cache_purge_url',
1641	sprintf(
1642	/* translators: 1: cause of the purge, 2: URL or path, 3: number of files removed. */
1643	__( 'Purged one URL (%1$s) — %2$s, %3$d file(s) removed', 'xspeed' ),
1644	$cause,
1645	$host . $path,
1646	$count
1647	),
1648	Activity_Log::INFO
1649	);
1650	}
1651
1652	return $count;
1653	}
1654
1655	/**
1656	* Purge this site's cache.
1657	*
1658	* On multisite every blog shares one cache directory, so an unscoped
1659	* sweep here took the whole network cold — one subsite's settings save
1660	* or post publish rebuilt every other site from PHP. Entries are stored
1661	* per host (see host_dir()), and the sweep is scoped to match, so a
1662	* purge originating on site-a leaves site-b's cache warm. (#6)
1663	*
1664	* @param string $cause Who asked, for the purge log.
1665	* @param string\|null $host Host to purge. Defaults to the current site.
1666	* Pass '*' to sweep the ENTIRE tree — network
1667	* admin's "purge all sites", and the migration
1668	* of pre-#6 entries that sit in the tree root.
1669	*/
1670	public static function purge_all( string $cause = 'manual', ?string $host = null ) {
1671	$network_wide = ( '*' === $host );
1672	// The flat tree buckets by a flattened segment (host/a-b) while the
1673	// static tree mirrors the URL (host/a/b), so they need separate
1674	// scopes — see current_host_dir() vs current_static_scope().
1675	$static_scope = '';
1676	if ( null === $host \|\| $network_wide ) {
1677	$scope = $network_wide ? '' : self::current_host_dir();
1678	$static_scope = $network_wide ? '' : self::current_static_scope();
1679	} else {
1680	$dir = self::host_dir( $host );
1681	$scope = '' === $dir ? 'default' : $dir;
1682	$static_scope = $scope;
1683	}
1684
1685	$count = 0;
1686	if ( is_dir( XSPEED_CACHE_DIR ) ) {
1687	// Scoped to one host directory, or the whole tree (including the
1688	// legacy top-level entries written before #6) when network-wide.
1689	/*
1690	* Network-wide sweeps go TWO levels deep, not one. A subdirectory
1691	* subsite's bucket is `<host>/<prefix>/`, so globbing only
1692	* `<cache>/*` reached the main site and left every subsite's
1693	* entries in place. (QA D5 on #166)
1694	*
1695	* A scoped purge also has to cover its own nested buckets: when
1696	* the main blog of a subdirectory network purges, `<host>/` is its
1697	* bucket and `<host>/one/` belongs to another blog — so the scoped
1698	* branch deliberately does NOT descend, which is what keeps
1699	* site-level purges isolated.
1700	*/
1701	$roots = $network_wide
1702	? array_merge(
1703	array( XSPEED_CACHE_DIR ),
1704	array_filter( (array) glob( XSPEED_CACHE_DIR . '/*', GLOB_ONLYDIR ) ),
1705	array_filter( (array) glob( XSPEED_CACHE_DIR . '//', GLOB_ONLYDIR ) )
1706	)
1707	: array( XSPEED_CACHE_DIR . '/' . $scope );
1708
1709	foreach ( $roots as $root ) {
1710	/*
1711	* min/ and rest/ are swept by their own purgers below; never
1712	* treat them as host buckets.
1713	*
1714	* Checked on every path SEGMENT, not just the basename: now
1715	* that the network-wide glob descends two levels it can reach
1716	* `min/combined`, whose basename is `combined` and would sail
1717	* past a basename-only test — deleting the combined
1718	* stylesheets out from under the pages that link them.
1719	*/
1720	if ( ! $network_wide \|\| XSPEED_CACHE_DIR !== $root ) {
1721	$relative = trim( str_replace( XSPEED_CACHE_DIR, '', (string) $root ), '/' );
1722	$segments = '' === $relative ? array() : explode( '/', $relative );
1723	if ( array_intersect( $segments, array( 'min', 'rest' ) ) ) {
1724	continue;
1725	}
1726	}
1727	if ( ! is_dir( $root ) ) {
1728	continue;
1729	}
1730	$files = glob( $root . '/*.html' );
1731	if ( $files ) {
1732	$count += count( $files );
1733	foreach ( $files as $f ) {
1734	wp_delete_file( $f );
1735	}
1736	}
1737	// Remove the .meta sidecars (content-type for feeds/sitemaps)
1738	// alongside their .html entries. Not counted — they're not
1739	// cache "pages", just per-entry metadata.
1740	$meta = glob( $root . '/*.meta' );
1741	if ( $meta ) {
1742	foreach ( $meta as $m ) {
1743	wp_delete_file( $m );
1744	}
1745	}
1746	// Remove precompressed siblings (e.g. <key>.html.br from the Pro
1747	// Brotli module). Not counted — same as .meta. Without this a
1748	// purge leaves stale .br bodies behind: disk bloat, and a
1749	// staleness window if precompression is later disabled.
1750	$br = glob( $root . '/*.br' );
1751	if ( $br ) {
1752	foreach ( $br as $b ) {
1753	wp_delete_file( $b );
1754	}
1755	}
1756	}
1757	}
1758	// Static-cache tree purge — recursive because the layout is
1759	// xspeed-static/{host}/{path}/index.html, so a flat glob can't
1760	// reach everything. Already host-segmented, so scoping is just a
1761	// matter of starting one level down.
1762	if ( is_dir( XSPEED_CACHE_STATIC_DIR ) ) {
1763	$static_root = $network_wide
1764	? XSPEED_CACHE_STATIC_DIR
1765	: XSPEED_CACHE_STATIC_DIR . '/' . $static_scope;
1766	if ( is_dir( $static_root ) ) {
1767	$count += self::rmtree_html( $static_root );
1768	}
1769	}
1770	// REST response cache (cache/xspeed/rest/*.json) — same purge
1771	// triggers (publish, settings change) invalidate it too.
1772	$count += Rest_Cache::purge();
1773
1774	// Minified + combined CSS/JS (cache/xspeed/min/ and min/combined/).
1775	// purge_all is a full filesystem sweep and must clear these too, even
1776	// when the Minify module is currently disabled — orphaned min/ files
1777	// from a feature the user later turned off must still be removed, and
1778	// a stale combined-<hash>.css that the regenerated page no longer
1779	// references otherwise 404s and breaks the frontend. (FBS-83114/83116)
1780	if ( class_exists( '\\XSpeed\\Minifier' ) ) {
1781	Minifier::purge_minified();
1782	}
1783
1784	// Persistent object cache (Redis / Memcached). Flush regardless of
1785	// whether the Object Cache module is currently enabled — a drop-in
1786	// installed earlier keeps serving until flushed.
1787	//
1788	// wp_cache_flush() is NETWORK-global: on multisite it would drop
1789	// every other site's object cache too, which is the same bug this
1790	// change fixes for the page cache. Prefer the blog-scoped flush
1791	// (WP 6.1+) unless we were explicitly asked to go network-wide. (#6)
1792	if ( ! $network_wide && is_multisite() && function_exists( 'wp_cache_flush_group' ) && function_exists( 'wp_cache_supports' ) && wp_cache_supports( 'flush_group' ) ) {
1793	// Blog-scoped groups only; a shared/global group (site options,
1794	// user meta) is intentionally left alone.
1795	foreach ( array( 'options', 'posts', 'terms', 'post_meta', 'comment' ) as $group ) {
1796	wp_cache_flush_group( $group );
1797	}
1798	} elseif ( function_exists( 'wp_cache_flush' ) ) {
1799	wp_cache_flush();
1800	}
1801
1802	self::update_stats( array( 'last_purge' => time() ) );
1803
1804	// Fire AFTER the local sweep so module listeners (Critical CSS,
1805	// Unused CSS, Cloudflare edge purge) run — this action had three
1806	// registered listeners but was never emitted. Treat it as additive
1807	// (CDN / edge invalidation), not the mechanism for clearing local
1808	// files. (FBS-83114)
1809	do_action( 'xspeed_after_purge_all', $cause );
1810
1811	// The list behind the "Cached pages" card is memoized for a minute;
1812	// a purge has to drop it or the drill-down shows pages that no
1813	// longer exist.
1814	Cache_Inventory::invalidate();
1815
1816	// Trigger of WP_CLI / hook / admin-bar purges all hit the same
1817	// path. Record once with the supplied cause so the dashboard
1818	// activity feed reads naturally.
1819	Activity_Log::record(
1820	'cache_purged',
1821	sprintf( 'Cache purged (%s) — %d file%s removed', $cause, $count, 1 === $count ? '' : 's' ),
1822	Activity_Log::INFO
1823	);
1824
1825	return $count;
1826	}
1827
1828	/**
1829	* The per-type purge menu, LiteSpeed-style. Each entry is a cache type
1830	* the user can purge individually from the admin-bar dropdown. `visible`
1831	* controls whether the item shows (active + licensed module only) — it
1832	* NEVER limits Purge All, which always sweeps everything on disk.
1833	*
1834	* Pro registers its own types (Critical CSS, Unused CSS, …) by filtering
1835	* `xspeed_purge_types`, so Free degrades gracefully when Pro is absent.
1836	*
1837	* @return array<string,array{label:string,visible:bool}>
1838	*/
1839	public static function purge_types(): array {
1840	$minify_on = false;
1841	if ( class_exists( '\\XSpeed\\Settings_Manager' ) ) {
1842	$min = Settings_Manager::get( 'minify' );
1843	$minify_on = ! empty( $min['minify_css'] ) \|\| ! empty( $min['minify_js'] ) \|\| ! empty( $min['combine_css'] ) \|\| ! empty( $min['combine_js'] );
1844	}
1845	// Object cache is "active" when an external object-cache drop-in is in
1846	// use — the canonical WP signal, independent of our settings option.
1847	$oc_on = function_exists( 'wp_using_ext_object_cache' ) && wp_using_ext_object_cache();
1848
1849	$types = array(
1850	'all' => array(
1851	'label' => __( 'Purge All', 'xspeed' ),
1852	'visible' => true,
1853	),
1854	'page' => array(
1855	'label' => __( 'Purge Page / Static Cache', 'xspeed' ),
1856	'visible' => true,
1857	),
1858	'assets' => array(
1859	'label' => __( 'Purge CSS / JS Cache', 'xspeed' ),
1860	'visible' => $minify_on,
1861	),
1862	'object' => array(
1863	'label' => __( 'Purge Object Cache', 'xspeed' ),
1864	'visible' => $oc_on,
1865	),
1866	'rest' => array(
1867	'label' => __( 'Purge REST Cache', 'xspeed' ),
1868	'visible' => true,
1869	),
1870	);
1871
1872	/**
1873	* Filter the admin-bar purge-type menu. Pro modules add their own
1874	* (Critical CSS, Unused CSS, CDN). Adding a type here only adds a
1875	* MENU item — purge_type() must know how to handle the same slug.
1876	*
1877	* @param array $types Map of slug => [label, visible].
1878	*/
1879	return (array) apply_filters( 'xspeed_purge_types', $types );
1880	}
1881
1882	/**
1883	* Purge a single cache type by slug. 'all' delegates to purge_all();
1884	* every other slug clears just its own artifacts. Unknown slugs (e.g. a
1885	* Pro type) fan out via the `xspeed_purge_type_{slug}` action so the
1886	* owning module can handle it. Returns the number of items removed where
1887	* countable.
1888	*
1889	* @param string $type Cache type slug.
1890	* @param string $cause Who asked. Threaded through so the purge log can
1891	* tell an AI assistant's purge apart from a click —
1892	* "the cache cleared four times today" is only
1893	* actionable once you know what kept clearing it.
1894	*/
1895	public static function purge_type( string $type, string $cause = 'manual' ): int {
1896	switch ( $type ) {
1897	case 'all':
1898	return self::purge_all( $cause );
1899
1900	case 'page':
1901	$count = 0;
1902	// Scoped to this site — see purge_all(). (#6)
1903	$scope = self::current_host_dir();
1904	$flat_root = XSPEED_CACHE_DIR . '/' . $scope;
1905	if ( is_dir( $flat_root ) ) {
1906	foreach ( (array) glob( $flat_root . '/*.html' ) as $f ) {
1907	wp_delete_file( $f );
1908	++$count;
1909	}
1910	foreach ( (array) glob( $flat_root . '/*.meta' ) as $m ) {
1911	wp_delete_file( $m );
1912	}
1913	foreach ( (array) glob( $flat_root . '/*.br' ) as $b ) {
1914	wp_delete_file( $b );
1915	}
1916	}
1917	$static_root = XSPEED_CACHE_STATIC_DIR . '/' . self::current_static_scope();
1918	if ( is_dir( $static_root ) ) {
1919	$count += self::rmtree_html( $static_root );
1920	}
1921	self::update_stats( array( 'last_purge' => time() ) );
1922	Cache_Inventory::invalidate();
1923	self::record_partial_purge( 'page', $cause, $count );
1924	return $count;
1925
1926	case 'assets':
1927	if ( class_exists( '\\XSpeed\\Minifier' ) ) {
1928	Minifier::purge_minified();
1929	}
1930	self::record_partial_purge( 'assets', $cause, null );
1931	return 0;
1932
1933	case 'object':
1934	if ( function_exists( 'wp_cache_flush' ) ) {
1935	wp_cache_flush();
1936	}
1937	self::record_partial_purge( 'object cache', $cause, null );
1938	return 0;
1939
1940	case 'rest':
1941	$count = Rest_Cache::purge();
1942	self::record_partial_purge( 'REST responses', $cause, $count );
1943	return $count;
1944
1945	default:
1946	// Pro / third-party type — let the owning module handle it.
1947	do_action( 'xspeed_purge_type_' . $type );
1948	self::record_partial_purge( $type, $cause, null );
1949	return 0;
1950	}
1951	}
1952
1953	/**
1954	* Log a partial purge so the drill-down behind "Last purge" shows every
1955	* clear, not only the full ones. Without this a site whose object cache
1956	* is flushed on a schedule looks, from the log, like nothing happens.
1957	*
1958	* @param string $what Human label for the slice purged.
1959	* @param string $cause Who asked.
1960	* @param int\|null $count Items removed, when countable.
1961	*/
1962	private static function record_partial_purge( string $what, string $cause, ?int $count ): void {
1963	$message = null === $count
1964	? sprintf(
1965	/* translators: 1: what was purged, 2: cause of the purge. */
1966	__( 'Purged %1$s (%2$s)', 'xspeed' ),
1967	$what,
1968	$cause
1969	)
1970	: sprintf(
1971	/* translators: 1: what was purged, 2: cause of the purge, 3: number of files removed. */
1972	__( 'Purged %1$s (%2$s) — %3$d file(s) removed', 'xspeed' ),
1973	$what,
1974	$cause,
1975	$count
1976	);
1977
1978	Activity_Log::record( 'cache_purged', $message, Activity_Log::INFO );
1979	}
1980
1981	/**
1982	* Clear the static tree only, leaving the flat cache in place.
1983	*
1984	* A narrower purge_all() for the case where only the web-server tree can
1985	* be wrong: its files are keyed by `{host}{path}` and nothing else, so a
1986	* response filed under the wrong path poisons it while the flat cache —
1987	* keyed by cache_key(), discriminators included — stays correct. Avoids
1988	* throwing away Critical CSS, minified bundles and the object cache to
1989	* fix a static-only problem.
1990	*
1991	* @return int Number of index.html files removed.
1992	*/
1993	public static function purge_static_tree(): int {
1994	return self::rmtree_html( XSPEED_CACHE_STATIC_DIR );
1995	}
1996
1997	/**
1998	* Recursively delete every `index.html` (and its precompressed
1999	* `index.html.br` sibling, if the Pro Brotli module wrote one) plus
2000	* empty directories inside the static-cache tree. Used by purge_all().
2001	* Returns the number of .html files removed so purge stats stay accurate
2002	* across the flat + static caches — .br siblings are not counted
2003	* (they're encodings of a page, not pages).
2004	*/
2005	private static function rmtree_html( string $dir ): int {
2006	if ( ! is_dir( $dir ) ) {
2007	return 0;
2008	}
2009	$removed = 0;
2010	// SCANDIR_SORT_NONE skips alphabetic sort — we're going to walk
2011	// the whole tree regardless of order.
2012	$entries = @scandir( $dir, SCANDIR_SORT_NONE ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
2013	if ( false === $entries ) {
2014	return 0;
2015	}
2016	foreach ( $entries as $entry ) {
2017	if ( '.' === $entry \|\| '..' === $entry ) {
2018	continue;
2019	}
2020	$path = $dir . '/' . $entry;
2021	if ( is_dir( $path ) ) {
2022	$removed += self::rmtree_html( $path );
2023	// Best-effort empty-dir cleanup; ignore failures (a
2024	// foreign file inside would block rmdir, which is fine).
2025	// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, WordPress.WP.AlternativeFunctions.file_system_operations_rmdir -- Best-effort empty-dir cleanup; WP_Filesystem needs admin credentials we don't have during a normal purge.
2026	@rmdir( $path );
2027	continue;
2028	}
2029	if ( substr( $entry, -5 ) === '.html' ) {
2030	wp_delete_file( $path );
2031	++$removed;
2032	} elseif ( substr( $entry, -3 ) === '.br' ) {
2033	// Precompressed sibling (index.html.br). Remove it too so a
2034	// purge doesn't orphan stale Brotli bodies. Not counted.
2035	wp_delete_file( $path );
2036	}
2037	}
2038	return $removed;
2039	}
2040
2041	/**
2042	* Drop a "silence is golden" index.php into a directory so apaches/nginx
2043	* with directory listing enabled don't expose cache contents.
2044	*/
2045	public static function write_silence( $dir ) {
2046	$file = trailingslashit( $dir ) . 'index.php';
2047	if ( ! file_exists( $file ) ) {
2048	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin context for credentials; cache dir setup may run during a frontend page render.
2049	file_put_contents( $file, "<?php\n// Silence is golden.\n" );
2050	}
2051	}
2052
2053	/**
2054	* The raw xspeed_stats option as an array. Keys currently in use:
2055	* 'last_purge', 'last_gc', 'gc_removed', 'gc_removed_total'.
2056	*/
2057	public static function get_stats_option(): array {
2058	$stats = get_option( 'xspeed_stats', array() );
2059	return is_array( $stats ) ? $stats : array();
2060	}
2061
2062	/**
2063	* Persist stats with autoload disabled — stats are only read in admin
2064	* contexts, so there is no reason to inflate every frontend request's
2065	* `wp_load_alloptions()` payload.
2066	*
2067	* MERGES into whatever is already stored. It used to overwrite, which
2068	* was harmless while `last_purge` was the only key — with the GC keys
2069	* alongside it, a purge would have wiped the GC history and vice versa.
2070	*/
2071	public static function update_stats( array $stats ) {
2072	if ( false === get_option( 'xspeed_stats', false ) ) {
2073	add_option( 'xspeed_stats', $stats, '', 'no' );
2074	return;
2075	}
2076	update_option( 'xspeed_stats', array_merge( self::get_stats_option(), $stats ) );
2077	}
2078
2079	public static function get_stats() {
2080	$count = 0;
2081	$size = 0;
2082	// This site's entries only — on multisite the tree is shared, so an
2083	// unscoped count reported the whole network's pages on every
2084	// subsite's dashboard. (#6)
2085	$flat_root = XSPEED_CACHE_DIR . '/' . self::current_host_dir();
2086	if ( is_dir( $flat_root ) ) {
2087	$files = glob( $flat_root . '/*.html' );
2088	if ( $files ) {
2089	$count = count( $files );
2090	foreach ( $files as $f ) {
2091	$size += filesize( $f );
2092	}
2093	}
2094	}
2095	// Drain the HIT-log file BEFORE reading totals. Two serve paths that
2096	// bypass the normal in-PHP record_hit() append one line per HIT here:
2097	// the nginx server-level rewrite (see nginx_snippet(), never reaches
2098	// PHP) and the advanced-cache.php drop-in (runs pre-WordPress, can't
2099	// reach Hit_Counter). Without this drain both look like a 0% hit-ratio
2100	// on a perfectly working cache.
2101	Hit_Counter::collect_nginx_log_hits();
2102
2103	// Apache/LiteSpeed static-rewrite HITs are served straight from disk
2104	// by .htaccess and never reach PHP either — but there's no .htaccess
2105	// equivalent of nginx's access_log directive, so we count them by
2106	// scanning the web server's own access log incrementally. No-op when
2107	// the log isn't readable (managed hosts) — see the method docblock.
2108	Hit_Counter::collect_server_log_hits();
2109
2110	$stats = get_option( 'xspeed_stats', array() );
2111	$totals = Hit_Counter::totals_24h();
2112	return array(
2113	'cached_pages' => $count,
2114	'cache_size' => $size,
2115	'last_purge' => isset( $stats['last_purge'] ) ? (int) $stats['last_purge'] : 0,
2116	// Rolling 24h cache performance — sourced from Hit_Counter's
2117	// hourly buckets. The frontend uses hit_ratio to drive the
2118	// CacheHero stat grid + the Health module's panel.
2119	'hits_24h' => $totals['hits'],
2120	'misses_24h' => $totals['misses'],
2121	'hit_ratio' => $totals['ratio'],
2122	// Requests kept OUT of the ratio (404s + bots) — surfaced as its own
2123	// "absorbed N scanner/bot requests" line rather than distorting the
2124	// cache-performance number. (#118)
2125	'excluded_24h' => $totals['excluded'],
2126	// True when an edge cache (Cloudflare) fronts the origin, so hits are
2127	// absorbed before reaching PHP. The dashboard labels the ratio
2128	// "origin-layer only" instead of implying it's the full picture. (#118)
2129	'edge_cache' => self::edge_cache_detected(),
2130	);
2131	}
2132
2133	/**
2134	* Whether the current request should be kept OUT of the cache hit/miss
2135	* ratio: a genuine 404, or a known bot / scanner. Runs at template_redirect
2136	* time, so is_404() is resolved. (#118)
2137	*/
2138	private static function miss_is_excluded(): bool {
2139	if ( function_exists( 'is_404' ) && is_404() ) {
2140	return true;
2141	}
2142	$ua = isset( $_SERVER['HTTP_USER_AGENT'] )
2143	? sanitize_text_field( wp_unslash( (string) $_SERVER['HTTP_USER_AGENT'] ) )
2144	: '';
2145	return Hit_Counter::is_bot_ua( $ua );
2146	}
2147
2148	/**
2149	* Whether an edge cache fronts this origin. Today: the Cloudflare
2150	* integration is connected — so an unknown share of hits is served at the
2151	* edge and never counted here, making the origin ratio a partial view the
2152	* dashboard must label as such. (#118)
2153	*/
2154	private static function edge_cache_detected(): bool {
2155	$cf = get_option( 'xspeed_module_cloudflare', array() );
2156	return is_array( $cf ) && ! empty( $cf['enabled'] );
2157	}
2158
2159	/**
2160	* Apply the user's enable/disable choice. Called from the REST toggle
2161	* endpoint, which is gated by current_user_can( 'manage_options' ) and
2162	* a verified REST nonce.
2163	*
2164	* This is the only path that ENABLES caching — a drop-in is never
2165	* created for a user who hasn't opted in, which is the guideline that
2166	* matters (a plugin must not install drop-ins or edit wp-config.php
2167	* on a fresh activation). RESTORING the drop-in for a site that
2168	* already has cache_enabled = true is a different act and is handled
2169	* by restore_dropin_if_enabled() on activation and auto_heal() at
2170	* runtime; without it every plugin update silently un-caches the site.
2171	*
2172	* @param bool $enable User's choice.
2173	* @return array{
2174	* enabled: bool,
2175	* dropin_installed: bool,
2176	* wp_cache_constant: bool,
2177	* wp_config_writable: bool,
2178	* manual_snippet: ?string
2179	* }
2180	*/
2181	public static function toggle( $enable ) {
2182	$enable = (bool) $enable;
2183
2184	if ( $enable ) {
2185	$dropin_ok = self::install_dropin();
2186	$wp_config_ok = self::set_wp_cache_constant( true );
2187	$rewrite_ok = self::install_rewrite();
2188	self::ensure_hits_log_file();
2189	self::sync_mobile_flag();
2190	$snippet = $wp_config_ok ? null : "define( 'WP_CACHE', true );";
2191
2192	Activity_Log::record(
2193	'cache_enabled_event',
2194	$wp_config_ok
2195	? 'Cache enabled. Drop-in installed, WP_CACHE constant set.'
2196	: 'Cache enabled. Drop-in installed; wp-config.php not writable — add the WP_CACHE snippet manually.',
2197	$wp_config_ok ? Activity_Log::SUCCESS : Activity_Log::WARN
2198	);
2199
2200	return array(
2201	'enabled' => true,
2202	'dropin_installed' => (bool) $dropin_ok,
2203	'wp_cache_constant' => (bool) $wp_config_ok,
2204	'rewrite_installed' => (bool) $rewrite_ok,
2205	'wp_config_writable' => self::wp_config_writable(),
2206	'manual_snippet' => $snippet,
2207	'nginx_snippet' => self::nginx_snippet(),
2208	// Unified server-block snippet aggregating every enabled
2209	// module's directives — the same value the dashboard and
2210	// Health insight render. The wizard shows this so all three
2211	// surfaces stay in lockstep. Null on non-nginx hosts.
2212	'nginx_server_block' => self::full_nginx_server_block(),
2213	);
2214	}
2215
2216	self::remove_dropin();
2217	self::set_wp_cache_constant( false );
2218	self::remove_rewrite();
2219	// Drop the device-bucket marker too — with the drop-in gone there's
2220	// nothing left to read it, and leaving it behind would dirty a fresh
2221	// re-enable (and leaks across test runs).
2222	self::sync_mobile_flag( false );
2223
2224	Activity_Log::record(
2225	'cache_disabled_event',
2226	'Cache disabled. Drop-in removed.',
2227	Activity_Log::INFO
2228	);
2229
2230	return array(
2231	'enabled' => false,
2232	'dropin_installed' => false,
2233	'wp_cache_constant' => false,
2234	'rewrite_installed' => false,
2235	'wp_config_writable' => self::wp_config_writable(),
2236	'manual_snippet' => null,
2237	'nginx_snippet' => self::nginx_snippet(),
2238	'nginx_server_block' => self::full_nginx_server_block(),
2239	);
2240	}
2241
2242	/**
2243	* Check wp-config.php writability via WP_Filesystem. Plugin Check flags
2244	* direct is_writable() under WordPress.WP.AlternativeFunctions.
2245	*/
2246	private static function wp_config_writable() {
2247	global $wp_filesystem;
2248	if ( ! function_exists( 'WP_Filesystem' ) ) {
2249	require_once ABSPATH . 'wp-admin/includes/file.php';
2250	}
2251	WP_Filesystem();
2252
2253	return $wp_filesystem ? (bool) $wp_filesystem->is_writable( ABSPATH . 'wp-config.php' ) : false;
2254	}
2255
2256	/**
2257	* Nginx server-block snippet mirroring the Apache rewrite block.
2258	* We never auto-write nginx config — it sits outside the WordPress
2259	* root and is owned by the server admin — but the dashboard
2260	* surfaces this snippet when nginx is detected so the admin can
2261	* paste it once and unlock the same PHP-bypass speedup we get on
2262	* Apache / LiteSpeed via .htaccess.
2263	*
2264	* Returns null when the server isn't nginx (no point showing it).
2265	*/
2266	/**
2267	* Create wp-content/cache/xspeed/hits.log as an empty file so the
2268	* server-level rewrite's `access_log` directive has somewhere to
2269	* write on first request. Idempotent — touches an existing file
2270	* without disturbing accumulated lines. Called from Cache::toggle()
2271	* on enable and from auto_heal() when the file is missing.
2272	*
2273	* Permissions matter here. The file is created by PHP-FPM (often uid
2274	* www-data), but the nginx process that appends HIT lines may run as a
2275	* DIFFERENT uid — on multi-container hosts (e.g. xclude/Kinsta: nginx in
2276	* its own container as uid `nginx`, PHP-FPM in another as `www-data`)
2277	* they don't share a user at all. A default-umask 0644 file is then
2278	* unwritable by nginx, the access_log write silently fails, and the
2279	* dashboard shows a 0% hit ratio even though static HITs are serving.
2280	* So we widen the dir to 0777 and the file to 0666 — group/other write —
2281	* so whatever uid nginx runs as can append. (The file holds only HIT
2282	* request lines, no secrets.)
2283	*/
2284	/**
2285	* Directory holding the nginx hit log. Lives under uploads/, NOT the
2286	* cache dir — uninstall.php and a cache purge both delete the cache
2287	* dir, which would orphan the pasted nginx `access_log` directive's
2288	* parent directory and make `nginx -t` fail [emerg], taking down every
2289	* vhost on the host (FBS-82478). uploads/ always exists, isn't a
2290	* plugin-managed cache dir, and is never deleted on uninstall — so the
2291	* directive's target dir survives both, and nginx (which creates a
2292	* missing log FILE but not a missing DIR) can always open it.
2293	*
2294	* Falls back to the cache dir only if uploads is somehow unavailable.
2295	*/
2296	public static function hits_log_dir(): string {
2297	if ( function_exists( 'wp_upload_dir' ) ) {
2298	$uploads = wp_upload_dir( null, false );
2299	if ( is_array( $uploads ) && empty( $uploads['error'] ) && ! empty( $uploads['basedir'] ) ) {
2300	return rtrim( (string) $uploads['basedir'], '/' ) . '/xspeed';
2301	}
2302	}
2303	return XSPEED_CACHE_DIR;
2304	}
2305
2306	/** Absolute path to the nginx hit log file. */
2307	public static function hits_log_path(): string {
2308	return self::hits_log_dir() . '/hits.log';
2309	}
2310
2311	/**
2312	* Sync the drop-in's mobile-bucket flag file with the `mobile_separate`
2313	* setting. The drop-in (advanced-cache.php) runs before WordPress loads,
2314	* so it can't read the option — instead it checks for a zero-byte
2315	* `.mobile-separate` marker next to the cache files. When the setting is
2316	* on we touch the marker; when off we remove it. The drop-in's cache_key
2317	* computation keys off the marker's presence so its '\|m'/'\|d' device
2318	* bucket stays in lockstep with Cache::cache_key().
2319	*
2320	* Without this, turning on mobile_separate made Cache::store() write keys
2321	* with a '\|d'/'\|m' suffix the drop-in never reproduced — so the drop-in's
2322	* file_exists() always missed, every HIT fell through to a full WP boot,
2323	* and the fast pre-WP path was silently dead.
2324	*
2325	* @param bool\|null $enabled Force a state; null reads the current setting.
2326	*/
2327	/**
2328	* Write the subdirectory-multisite path list the drop-in needs to work
2329	* out which blog a request belongs to.
2330	*
2331	* The drop-in runs before WordPress, so it cannot call is_multisite()
2332	* or get_blog_details(). It can only see REQUEST_URI — so we persist the
2333	* network's blog paths (one per line, longest first) next to the cache
2334	* files, exactly as sync_mobile_flag() persists the device flag. The
2335	* drop-in prefix-matches the URI against that list to pick the same
2336	* bucket Cache::current_host_dir() picks. (#6)
2337	*
2338	* No file is written for a single site or a subdomain network — there
2339	* the host alone identifies the blog and the bucket carries no prefix.
2340	*/
2341	public static function sync_site_paths(): void {
2342	$file = XSPEED_CACHE_DIR . '/.site-paths';
2343
2344	$needed = function_exists( 'is_multisite' ) && is_multisite()
2345	&& ( ! function_exists( 'is_subdomain_install' ) \|\| ! is_subdomain_install() );
2346
2347	if ( ! $needed ) {
2348	if ( file_exists( $file ) ) {
2349	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- plain marker removal; non-fatal.
2350	@unlink( $file );
2351	}
2352	return;
2353	}
2354
2355	if ( ! function_exists( 'get_sites' ) ) {
2356	return;
2357	}
2358
2359	$paths = array();
2360	foreach ( get_sites( array( 'number' => 0 ) ) as $site ) {
2361	$prefix = self::path_prefix_segment( (string) $site->path );
2362	if ( '' !== $prefix ) {
2363	// Store the raw path so the drop-in can prefix-match a URI,
2364	// alongside the segment it maps to.
2365	$paths[ trim( (string) $site->path, '/' ) ] = $prefix;
2366	}
2367	}
2368
2369	if ( empty( $paths ) ) {
2370	if ( file_exists( $file ) ) {
2371	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- see above.
2372	@unlink( $file );
2373	}
2374	return;
2375	}
2376
2377	// Longest path first so /a/b wins over /a.
2378	uksort(
2379	$paths,
2380	static function ( $x, $y ) {
2381	return strlen( (string) $y ) <=> strlen( (string) $x );
2382	}
2383	);
2384
2385	$lines = array();
2386	foreach ( $paths as $raw => $segment ) {
2387	$lines[] = $raw . '\|' . $segment;
2388	}
2389
2390	if ( ! is_dir( XSPEED_CACHE_DIR ) && ! wp_mkdir_p( XSPEED_CACHE_DIR ) ) {
2391	return;
2392	}
2393	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- read by the pre-WP drop-in; WP_Filesystem needs admin credentials unavailable here.
2394	file_put_contents( $file, implode( "\n", $lines ), LOCK_EX );
2395	}
2396
2397	public static function sync_mobile_flag( $enabled = null ): void {
2398	if ( null === $enabled ) {
2399	$opts = Settings_Manager::get( 'cache' );
2400	$enabled = ! empty( $opts['mobile_separate'] );
2401	}
2402	$dir = XSPEED_CACHE_DIR;
2403	$flag = $dir . '/.mobile-separate';
2404	if ( $enabled ) {
2405	if ( ! is_dir( $dir ) && ! wp_mkdir_p( $dir ) ) {
2406	return;
2407	}
2408	if ( ! file_exists( $flag ) ) {
2409	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_touch, WordPress.PHP.NoSilencedErrors.Discouraged -- read by the pre-WP drop-in via file_exists(); must be a plain marker, not WP_Filesystem.
2410	@touch( $flag );
2411	}
2412	return;
2413	}
2414	if ( file_exists( $flag ) ) {
2415	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- plain marker removal; non-fatal.
2416	@unlink( $flag );
2417	}
2418	}
2419
2420	/**
2421	* Write / remove the `.maintenance-active` sentinel next to the cache
2422	* files. The pre-WP drop-in checks for this marker and bails when present,
2423	* so a page cached while the site was live is NOT served during
2424	* maintenance / coming-soon mode — WordPress loads and renders the
2425	* maintenance screen instead. The Pro Maintenance-Cache module drives this
2426	* on the maintenance on/off transition. (FBS-82409 B1)
2427	*
2428	* @param bool $active True to arm the sentinel (entering maintenance),
2429	* false to clear it (site recovered).
2430	*/
2431	public static function sync_maintenance_flag( bool $active ): void {
2432	$dir = XSPEED_CACHE_DIR;
2433	$flag = $dir . '/.maintenance-active';
2434	if ( $active ) {
2435	if ( ! is_dir( $dir ) && ! wp_mkdir_p( $dir ) ) {
2436	return;
2437	}
2438	if ( ! file_exists( $flag ) ) {
2439	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_touch, WordPress.PHP.NoSilencedErrors.Discouraged -- read by the pre-WP drop-in via file_exists(); must be a plain marker, not WP_Filesystem.
2440	@touch( $flag );
2441	}
2442	return;
2443	}
2444	if ( file_exists( $flag ) ) {
2445	// phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink, WordPress.PHP.NoSilencedErrors.Discouraged -- plain marker removal; non-fatal.
2446	@unlink( $flag );
2447	}
2448	}
2449
2450	/**
2451	* Reconcile every mobile_separate-dependent artifact to the current
2452	* setting. Called on boot and whenever the cache settings are saved, so
2453	* flipping mobile_separate at runtime can't leave the install in a
2454	* half-converted state.
2455	*
2456	* Three things must agree with the setting:
2457	* 1. the drop-in's `.mobile-separate` flag (sync_mobile_flag()),
2458	* 2. the device-blind server rewrite — present only when OFF
2459	* (static_rewrite_allowed()),
2460	* 3. the now-stale static-cache tree + page cache, which were keyed
2461	* under the old scheme and would serve wrong-device HTML.
2462	*
2463	* No-ops when the cache is disabled — there's nothing installed to
2464	* reconcile, and toggle() handles install/teardown itself.
2465	*/
2466	public static function reconcile_mobile_separate(): void {
2467	self::sync_mobile_flag();
2468	// Keep the drop-in's view of the network's blog paths current — a
2469	// site added or removed changes which bucket its URLs belong to. (#6)
2470	if ( defined( 'XSPEED_CACHE_DIR' ) ) {
2471	self::sync_site_paths();
2472	}
2473
2474	// The rewrite/static reconciliation below needs the plugin's path
2475	// constants. They're absent in early-boot / unit-test contexts where
2476	// only the drop-in flag matters — bail to the flag-only behavior then.
2477	if ( ! defined( 'XSPEED_CACHE_STATIC_DIR' ) ) {
2478	return;
2479	}
2480
2481	// Only touch the rewrite + caches when caching is actually on.
2482	$opts = get_option( 'xspeed_options', array() );
2483	if ( empty( $opts['cache_enabled'] ) ) {
2484	return;
2485	}
2486
2487	$rewrite_present = self::rewrite_installed();
2488	$rewrite_wanted = self::static_rewrite_allowed();
2489
2490	// Did the thing that actually invalidates cache KEYS change?
2491	// mobile_separate buckets entries as \|d / \|m, so flipping it makes
2492	// stored entries mis-bucketed and they must go. A rewrite-state
2493	// mismatch from anything else (e.g. mod_headers detection, a hand-
2494	// edited .htaccess) changes no key at all — the same files are still
2495	// valid, they're just served by PHP instead of by the web server.
2496	// Purging there is what let one WP-CLI call wipe the whole cache on
2497	// every bootstrap. (#138)
2498	//
2499	// Read the setting from the SAME place static_rewrite_allowed() and
2500	// sync_mobile_flag() do — the cache module's settings, not the
2501	// top-level xspeed_options — or this marker would track a key that
2502	// never changes and a real flip would go unnoticed.
2503	$cache_opts = Settings_Manager::get( 'cache' );
2504	$mobile_now = ! empty( $cache_opts['mobile_separate'] );
2505	$mobile_last = get_option( 'xspeed_last_mobile_separate', null );
2506	$mobile_flipped = ( null !== $mobile_last && (bool) (int) $mobile_last !== $mobile_now );
2507
2508	if ( (string) (int) $mobile_now !== (string) $mobile_last ) {
2509	update_option( 'xspeed_last_mobile_separate', $mobile_now ? '1' : '0', false );
2510	}
2511
2512	if ( $rewrite_present === $rewrite_wanted ) {
2513	// Already consistent — nothing flipped, leave caches intact so a
2514	// plain settings save (e.g. expiry change) doesn't blow the cache.
2515	return;
2516	}
2517
2518	// Bring the rewrite into line with what this server actually supports.
2519	if ( $rewrite_wanted ) {
2520	self::install_rewrite();
2521	} else {
2522	self::remove_rewrite();
2523	}
2524
2525	// Only discard cache contents when the device bucketing changed.
2526	if ( $mobile_flipped ) {
2527	self::purge_all( 'mobile_separate changed' );
2528	}
2529	}
2530
2531	/**
2532	* Whether the server-level static-rewrite fast path may be used.
2533	*
2534	* The rewrite serves `{host}{path}/index.html` straight from the web
2535	* server, keyed only by host + path — it has no way to run our PHP
2536	* device detection, so it can't tell mobile from desktop. When
2537	* `mobile_separate` is on, a single static file would be shared across
2538	* devices and whoever primed it wins (mobile visitors could get desktop
2539	* HTML, or vice-versa). Rather than duplicate a wp_is_mobile()-equivalent
2540	* UA matcher into .htaccess AND the nginx snippet (three copies that
2541	* would inevitably drift), we simply DON'T engage the static rewrite when
2542	* mobile_separate is on. Requests then fall through to the PHP drop-in,
2543	* which buckets correctly — a small TTFB cost (~85ms vs ~30ms) paid only
2544	* on mobile-separate sites, in exchange for guaranteed correctness.
2545	*
2546	* LiteSpeed exclusion (2026-06-16): on LiteSpeed — OpenLiteSpeed in
2547	* particular — `.htaccess` CAN run our RewriteRule to serve the static
2548	* file, but its `.htaccess` engine ignores `mod_headers`, so we cannot
2549	* stamp the served response with `X-XSpeed-Cache: HIT`, AND there is no
2550	* `.htaccess` equivalent of nginx's per-location `access_log` to record
2551	* the hit. The result was a cache that worked but was invisible: no HIT
2552	* header and a hit-ratio frozen near 0%. Every OTHER server gives the
2553	* user a visible HIT header + a counted hit (nginx via add_header +
2554	* access_log in its snippet; Apache via the `<IfModule mod_headers.c>`
2555	* block in rewrite_block_lines(), WHEN that module is loaded — when it is
2556	* not, Apache takes this same drop-in fallback). To keep LiteSpeed
2557	* CONSISTENT with the rest, we route its hits
2558	* through the PHP drop-in instead — the drop-in emits
2559	* `X-XSpeed-Cache: HIT (php)` and calls Hit_Counter inline, exactly the
2560	* observable behavior the other servers get. The cost is the drop-in's
2561	* ~30ms TTFB vs the static path's ~10ms, paid only on LiteSpeed; in
2562	* exchange the dashboard hit-ratio and the response header finally tell
2563	* the truth there. (Apache keeps the static fast path — it honors the
2564	* header.) See maybe_emit_lscache_headers() for the paired LSCache
2565	* stand-down that stops LiteSpeed's own module from shadowing the
2566	* drop-in.
2567	*/
2568	public static function static_rewrite_allowed(): bool {
2569	// LiteSpeed: drop-in serves hits (visible + counted) — see docblock.
2570	if ( Server::LITESPEED === Server::type() ) {
2571	return false;
2572	}
2573	// Apache without mod_headers is in EXACTLY the position LiteSpeed
2574	// is in above: it can run the RewriteRule and serve the static
2575	// file, but it cannot stamp `X-XSpeed-Cache` on the response, so
2576	// the hit is invisible to the user and uncountable by
2577	// Hit_Counter. The docblock above used to assert Apache "honors
2578	// mod_headers" and left it on the fast path unconditionally —
2579	// true only when the module is actually loaded. Fall back to the
2580	// drop-in when it isn't, trading ~10ms of TTFB for a hit that
2581	// shows up in the header and the ratio. (Field report: hit ratio
2582	// pinned at 0% on a working Apache cache.)
2583	if ( Server::APACHE === Server::type() && ! Server::apache_has_mod_headers() ) {
2584	return false;
2585	}
2586	$opts = Settings_Manager::get( 'cache' );
2587	return empty( $opts['mobile_separate'] );
2588	}
2589
2590	/**
2591	* Why the device-blind static rewrite is NOT installed, when it isn't.
2592	* Returns 'mobile_separate' when Separate Mobile Cache is the blocker
2593	* (the static file is one-per-URL, so it can't coexist with per-device
2594	* buckets), 'no_mod_headers' when Apache can't stamp the HIT header,
2595	* '' otherwise. Lets the dashboard explain the slow path instead of
2596	* silently falling back to PHP serving. (FBS-83145)
2597	*
2598	* Every refusal in static_rewrite_allowed() that is NOT self-explanatory
2599	* must have a branch here. Otherwise the Health card falls through to
2600	* "Block missing — toggle Enable Cache off and on to reinstall it",
2601	* advice that cannot work: the same condition that suppressed the write
2602	* suppresses the reinstall, and auto_heal() strips the block again on
2603	* the next admin page load. (Field report: Apache host with mod_headers
2604	* unloaded sat on the slow path with no way to find out why.)
2605	*/
2606	/**
2607	* Qualify a raw probe result with what we already KNOW about config.
2608	*
2609	* probe_static_rewrite() writes its own file under the static-cache tree
2610	* and fetches that, which succeeds whenever the web server can serve a
2611	* static file at all — including when static_rewrite_allowed() is false
2612	* and no real page is on the static path. So `active: true` on its own is
2613	* not evidence that pages are being served statically.
2614	*
2615	* The reachable case is nginx with Separate Mobile Cache on: the snippet
2616	* lives in the server block and we cannot remove it, pages are
2617	* deliberately routed to the PHP drop-in, but the probe file is still
2618	* served directly.
2619	*
2620	* The Health panel learned this in 88b4b50; the CLI, REST and MCP paths
2621	* did not, so they kept reporting "active" in exactly that configuration.
2622	* Rather than repeat the reasoning at each call site, they now all come
2623	* through here.
2624	*
2625	* Deliberately does NOT consult rewrite_installed(): on nginx the fast
2626	* path is the pasted snippet and there is no .htaccess marker to find, so
2627	* requiring one would report every correctly-configured nginx site as
2628	* broken.
2629	*
2630	* @param array $probe Raw result from probe_static_rewrite().
2631	* @return array{active:bool,inconclusive:bool,reason:string,block_reason:string}
2632	*/
2633	public static function qualify_rewrite_probe( array $probe ): array {
2634	$active = (bool) ( $probe['active'] ?? false );
2635	$inconclusive = (bool) ( $probe['inconclusive'] ?? false );
2636	$reason = (string) ( $probe['reason'] ?? '' );
2637	$block_reason = self::static_rewrite_block_reason();
2638
2639	// With page caching off there is nothing to serve, so `active` can
2640	// never be true here whatever the raw probe says. probe_static_rewrite()
2641	// writes its OWN file under the static tree and fetches that, which
2642	// succeeds whenever the server can serve a static file at all — and on
2643	// nginx the snippet is server-level, so it keeps succeeding after the
2644	// cache is switched off.
2645	//
2646	// block_reason() used to carry this meaning by accident: it returned
2647	// 'mobile_separate' with caching off, and the refusal branch below
2648	// forced active=false. Now that it correctly reports '' (nothing can
2649	// block a fast path that isn't in use), this consumer has to state the
2650	// condition itself — otherwise `wp xspeed cache recheck-rewrite` and
2651	// POST /cache/recheck-rewrite claim "the web server is serving cache
2652	// hits directly" on a site with no cache. That is a positive false
2653	// claim rather than a nag, i.e. worse than the bug being fixed.
2654	$cache_opts = Settings::get();
2655	if ( empty( $cache_opts['cache_enabled'] ) ) {
2656	return array(
2657	'active' => false,
2658	'inconclusive' => false,
2659	'reason' => 'Page caching is off, so there is no cache for the web server to serve.',
2660	'block_reason' => '',
2661	);
2662	}
2663
2664	// A known refusal outranks the probe, and also outranks
2665	// "inconclusive" — a blocked rewrite whose probe merely failed to
2666	// complete is still definitely blocked.
2667	if ( '' !== $block_reason ) {
2668	$active = false;
2669	$inconclusive = false;
2670	$reason = self::block_reason_text( $block_reason );
2671	}
2672
2673	return array(
2674	'active' => $active,
2675	'inconclusive' => $inconclusive,
2676	'reason' => $reason,
2677	'block_reason' => $block_reason,
2678	);
2679	}
2680
2681	/**
2682	* Human-readable explanation for a static_rewrite_block_reason() code.
2683	*
2684	* Each one has to say what to DO about it: "mobile_separate" alone tells
2685	* a user nothing, and the whole point of surfacing a refusal instead of
2686	* the probe verdict is that it is actionable.
2687	*/
2688	public static function block_reason_text( string $code ): string {
2689	switch ( $code ) {
2690	case 'mobile_separate':
2691	return 'Separate Mobile Cache is on, which disables the device-blind static rewrite. Cache hits are served by PHP instead. If your site serves the same HTML to every device, turn it off in Cache settings for much faster hits.';
2692	case 'no_mod_headers':
2693	return "Apache's mod_headers is not loaded, so the static rewrite cannot mark its responses as cache hits. Enable mod_headers, or leave hits on the PHP path.";
2694	default:
2695	return sprintf( 'The static rewrite is disabled (%s).', $code );
2696	}
2697	}
2698
2699	public static function static_rewrite_block_reason(): string {
2700	// Nothing can be blocking the fast path when there is no cache to
2701	// serve from it. Without this the dashboard told users with page
2702	// caching switched OFF that Separate Mobile Cache "is disabling
2703	// faster static serving" — a fast path they were not using, about a
2704	// cache that did not exist. Every caller of this is a user-facing
2705	// explanation of why the rewrite is off, so "the cache is off" is
2706	// the honest answer, and it is silence. (#108)
2707	$opts = Settings::get();
2708	if ( empty( $opts['cache_enabled'] ) ) {
2709	return '';
2710	}
2711	if ( Server::LITESPEED === Server::type() ) {
2712	return ''; // Intended on LiteSpeed — not a "block".
2713	}
2714	if ( Server::APACHE === Server::type() && ! Server::apache_has_mod_headers() ) {
2715	return 'no_mod_headers';
2716	}
2717	$cache_opts = Settings_Manager::get( 'cache' );
2718	return ! empty( $cache_opts['mobile_separate'] ) ? 'mobile_separate' : '';
2719	}
2720
2721	/**
2722	* Whether migration flagged Separate Mobile Cache for user review. Set by
2723	* Migration::map_mobile_separate() when a source plugin (WP Rocket / WP
2724	* Super Cache / LiteSpeed) had its "separate mobile cache" option on: we
2725	* import it as OFF (to keep the device-blind static fast path) but record
2726	* this flag so the dashboard can invite the user to turn it back on only
2727	* if their site genuinely serves different HTML per device. (FBS-83145)
2728	*/
2729	public static function mobile_separate_needs_review(): bool {
2730	// Same reasoning as static_rewrite_block_reason(): the invitation is
2731	// "turn this back on if your site needs it, to regain the fast path",
2732	// which is meaningless with page caching off — there is no fast path
2733	// to regain, and the equality probe behind the prompt would fetch
2734	// pages that aren't being cached. Gated here rather than at the two
2735	// payload call sites (Admin + Rest_Api) so `enabled`, `blocking` and
2736	// `needs_review` are consistently gated on the same condition. (#108)
2737	$opts = Settings::get();
2738	if ( empty( $opts['cache_enabled'] ) ) {
2739	return false;
2740	}
2741	$cache_opts = Settings_Manager::get( 'cache' );
2742	return ! empty( $cache_opts['mobile_separate_review'] );
2743	}
2744
2745	/**
2746	* Clear the review flag — called when the user has acted on the prompt
2747	* (dismissed it, or turned Separate Mobile Cache on/off deliberately) so
2748	* the dashboard callout doesn't nag forever. Writes the option directly
2749	* (bypassing Settings_Manager) so it never touches schema fields.
2750	*/
2751	public static function clear_mobile_separate_review(): void {
2752	$stored = get_option( 'xspeed_module_cache', array() );
2753	if ( ! is_array( $stored ) \|\| empty( $stored['mobile_separate_review'] ) ) {
2754	return;
2755	}
2756	unset( $stored['mobile_separate_review'] );
2757	update_option( 'xspeed_module_cache', $stored );
2758	}
2759
2760	/**
2761	* On-demand probe: does the homepage serve materially the same HTML to a
2762	* desktop and a mobile browser? Fetches home_url() twice over loopback —
2763	* once with a desktop User-Agent, once with a mobile one — strips
2764	* per-request noise (nonces, CSRF tokens, session ids, inline timestamps),
2765	* and compares. When identical, Separate Mobile Cache is almost certainly
2766	* unnecessary and the user can turn it off to regain the static fast path.
2767	*
2768	* NEVER run automatically (no page-load cost) — only from the dashboard
2769	* "Check now" button. Result is cached for 10 minutes so a double-click or
2770	* a re-render doesn't fire two more self-requests. (FBS-83145)
2771	*
2772	* @return array{ identical:bool, checked:bool, reason?:string, desktop_bytes?:int, mobile_bytes?:int }
2773	*/
2774	public static function probe_mobile_equality(): array {
2775	$cached = get_transient( 'xspeed_mobile_equality_probe' );
2776	if ( is_array( $cached ) ) {
2777	return $cached;
2778	}
2779
2780	$home = home_url( '/' );
2781	$host = (string) wp_parse_url( $home, PHP_URL_HOST );
2782	if ( '' === $host ) {
2783	$result = array( 'identical' => false, 'checked' => false, 'reason' => 'home_url has no host' );
2784	set_transient( 'xspeed_mobile_equality_probe', $result, MINUTE_IN_SECONDS );
2785	return $result;
2786	}
2787
2788	// Match WP core's own mobile detection (wp_is_mobile) so the probe
2789	// reflects what the site would actually branch on. iPhone Safari for
2790	// mobile; a current desktop Chrome UA for desktop.
2791	$desktop_ua = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36';
2792	$mobile_ua = 'Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Mobile/15E148 Safari/604.1';
2793
2794	$is_local = function_exists( 'wp_get_environment_type' )
2795	&& in_array( wp_get_environment_type(), array( 'local', 'development' ), true );
2796
2797	$fetch = static function ( string $ua ) use ( $home, $is_local ) {
2798	$resp = wp_remote_get(
2799	$home,
2800	array(
2801	'timeout' => 5,
2802	'sslverify' => ! $is_local,
2803	'redirection' => 2,
2804	// Bust any per-device cache so we compare freshly-rendered
2805	// HTML, and pass the device UA the site would branch on.
2806	'user-agent' => $ua,
2807	'headers' => array( 'Cache-Control' => 'no-cache' ),
2808	)
2809	);
2810	if ( is_wp_error( $resp ) \|\| 200 !== (int) wp_remote_retrieve_response_code( $resp ) ) {
2811	return null;
2812	}
2813	return (string) wp_remote_retrieve_body( $resp );
2814	};
2815
2816	$desktop = $fetch( $desktop_ua );
2817	$mobile = $fetch( $mobile_ua );
2818
2819	if ( null === $desktop \|\| null === $mobile ) {
2820	$result = array( 'identical' => false, 'checked' => false, 'reason' => 'could not fetch homepage twice' );
2821	set_transient( 'xspeed_mobile_equality_probe', $result, MINUTE_IN_SECONDS );
2822	return $result;
2823	}
2824
2825	$identical = self::normalize_html_for_diff( $desktop ) === self::normalize_html_for_diff( $mobile );
2826
2827	$result = array(
2828	'identical' => $identical,
2829	'checked' => true,
2830	'desktop_bytes' => strlen( $desktop ),
2831	'mobile_bytes' => strlen( $mobile ),
2832	);
2833	set_transient( 'xspeed_mobile_equality_probe', $result, 10 * MINUTE_IN_SECONDS );
2834	return $result;
2835	}
2836
2837	/**
2838	* Strip per-request noise from HTML so a desktop-vs-mobile diff reflects
2839	* real structural differences, not nonces / session ids / timestamps that
2840	* change on every render. Deliberately conservative: it normalizes the
2841	* handful of well-known noise sources and collapses whitespace, so a site
2842	* that truly serves different markup per device still compares as different.
2843	*/
2844	private static function normalize_html_for_diff( string $html ): string {
2845	// Every rule here errs toward "they differ" being WRONG rather than
2846	// "they match" being wrong: this check only ever tells a user it is
2847	// SAFE to turn Separate Mobile Cache off, so a false "identical"
2848	// would cost them device-specific output. The risk of being too
2849	// conservative is milder but real — the useful answer never appears,
2850	// and the feature's whole pitch ("we'll prove it's safe to turn
2851	// off") silently never pays out. These close the gaps that made a
2852	// mismatch effectively guaranteed on an ordinary WordPress site. (#108)
2853	$patterns = array(
2854	// WP nonces in attribute or JSON form: data-nonce="…",
2855	// _wpnonce=…, "nonce":"…". The `[:=]` adjacency below misses
2856	// wp_nonce_field()'s own markup — `name="_wpnonce" value="ab…"`
2857	// puts `value=` between the key and the token — which is the
2858	// single most common nonce shape in WordPress, so that form is
2859	// matched explicitly first.
2860	'/name=["\']?(_wpnonce\|_ajax_nonce)["\']?\s+value=["\']?[a-z0-9]{8,}/i',
2861	// CSP nonces on script/style tags. Base64, so uppercase and
2862	// +/= appear — the hex-only rules below can never match one,
2863	// and a CSP-enabled site therefore differed on every fetch.
2864	// MUST precede the generic nonce rule: that one stops at the
2865	// first non-alphanumeric, leaving the rest of the token behind
2866	// and the two responses still unequal.
2867	// The quotes are optional so HTML5's legal unquoted attribute
2868	// form (`<script nonce=AbCd+q/r=>`) is covered too — without
2869	// that it fell through to the generic rule, which is the exact
2870	// failure this rule exists to remove.
2871	'/\bnonce=(["\'])?[A-Za-z0-9+\/=_-]{8,}(?(1)\1)/',
2872	'/(_wpnonce\|nonce\|_ajax_nonce)["\']?\s[:=]\s["\']?[a-z0-9]{8,}/i',
2873	// Generic hex tokens: cache busters, session ids, md5/sha
2874	// digests. Was 16+, which left an 11-15 char gap above the
2875	// 10-char nonce rule.
2876	//
2877	// The token MUST contain at least one a-f letter. `[a-f0-9]`
2878	// also matches every decimal digit, so a bare `{10,}` erased
2879	// every 10+ digit INTEGER anywhere in the document — including
2880	// visible body text. A page whose desktop and mobile HTML
2881	// differed only by a per-device numeric id (an AdSense slot, an
2882	// A/B bucket, an analytics property) then compared as identical,
2883	// and the check told the user it was safe to switch off the very
2884	// setting keeping that output correct — the one direction this
2885	// function must never fail in. Decimal-only runs are left to the
2886	// bounded epoch rule below, which is deliberately narrower.
2887	//
2888	// Known, accepted (QA R2): a token whose letters all fall in a-f
2889	// reads as a digest, so a per-device `ABC1234567890` strips even
2890	// though it is an id, not a hash. Deliberately left open — the
2891	// alternatives all cost more than the bug:
2892	//
2893	// Token shape (lowercase-only, case-uniformity, a trailing
2894	// letter) cannot separate it. `ABC1234567890` and
2895	// `ABCDEF012345` — an uppercase digest this rule SHOULD strip —
2896	// are both all-hex, uniformly cased, letters-then-digits.
2897	// Each variant fixed the id only by sparing the digest.
2898	//
2899	// Letter density does separate them (23% letters vs 50%), but
2900	// measured over 2000 md5/sha1/sha256 samples, requiring letters
2901	// spread through the token leaves 21-67% of REAL digests
2902	// unmatched depending on the window. Digest noise is most of
2903	// what this function exists to remove, so that trade guts it.
2904	//
2905	// Context (protecting data-* attribute values from this rule)
2906	// works for ids and still strips digests in URLs, classes and
2907	// query strings — but regresses a CHANGING digest inside a
2908	// non-nonce data-* attribute, and needs a two-pass
2909	// hold/restore. Viable if R2 is ever worth pressing; its
2910	// failure at least errs toward "differ".
2911	//
2912	// An A-F-only prefix on a per-device id is rare, and the earlier
2913	// nonce rules already claim the data-nonce/_wpnonce shapes.
2914	'/\b(?=[a-f0-9]{10,}\b)[0-9][a-f][a-f0-9]\b/i',
2915	// wp-generated unique ids (e.g. wp-block ids, aria ids).
2916	'/(id\|for\|aria-[a-z]+)="[^"]*-[0-9]{3,}"/i',
2917	// ISO-ish timestamps + epoch-looking numbers in query strings.
2918	'/\?ver=[0-9.]+/',
2919	'/[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9:.+Z-]+/',
2920	// Raw epoch seconds. The two fetches are sequential, so any
2921	// template printing time() guaranteed a mismatch.
2922	//
2923	// This is the ONLY rule that may strip a decimal-only run, so
2924	// its bound is load-bearing rather than decorative — every digit
2925	// it gives away is a class of per-device id it silently erases.
2926	// `1[0-9]{9}` was too loose: it claimed the whole
2927	// 1000000000-1999999999 range (2001-2033) to cover timestamps
2928	// nobody serves, and took every 10-digit AdSense slot, order id
2929	// and SKU beginning with 1 along with it — reproducing the exact
2930	// false-"identical" verdict the hex rule above was tightened to
2931	// stop. `1[6-9]` covers 2020-2033, which is the only span a live
2932	// site can actually print, and collides with roughly a tenth as
2933	// many ids.
2934	//
2935	// Not airtight — an id beginning 16-19 still collides. Closing
2936	// that properly means scoping this to places a timestamp really
2937	// appears (an attribute value, a query parameter, a JSON value)
2938	// rather than bare body text; the bound is the cheap 90% of it.
2939	'/\b1[6-9][0-9]{8}\b/',
2940	);
2941	$html = (string) preg_replace( $patterns, 'X', $html );
2942	// Collapse all whitespace so trivial formatting differences don't count.
2943	return trim( (string) preg_replace( '/\s+/', ' ', $html ) );
2944	}
2945
2946	public static function ensure_hits_log_file(): bool {
2947	// TWO writers append to this log, and an earlier fix conflated them:
2948	//
2949	// 1. nginx, via the server-level `access_log` directive in
2950	// nginx_snippet() — a DIFFERENT uid, which is why the file needs
2951	// to be world-writable there.
2952	// 2. the PHP drop-in (advanced-cache.php), on EVERY server. A hit it
2953	// serves bypasses WordPress entirely, so it can't call
2954	// Hit_Counter::record_hit() — appending here is the only way that
2955	// hit is ever counted.
2956	//
2957	// The nginx-only early return that used to sit at the top of this
2958	// method was fixing something real: chmod() on a file PHP doesn't own
2959	// raises "Operation not permitted", and off nginx that chmod buys
2960	// nothing. But it took directory creation with it, so on LiteSpeed
2961	// (which always serves via the drop-in), on Apache without mod_headers,
2962	// and anywhere mobile_separate forces the drop-in path, writer 2 was
2963	// appending to a file whose parent directory did not exist. The append
2964	// is @-suppressed and documented as non-fatal, so every one of those
2965	// hits vanished and the dashboard ratio sat at 0% forever.
2966	//
2967	// So: create the dir + file everywhere, and keep only the chmod gated
2968	// to nginx.
2969	$dir = self::hits_log_dir();
2970	if ( ! is_dir( $dir ) && ! wp_mkdir_p( $dir ) ) {
2971	return false;
2972	}
2973
2974	$is_nginx = ( Server::NGINX === Server::type() );
2975
2976	if ( $is_nginx ) {
2977	// Ensure the dir is traversable + writable by a different-uid nginx.
2978	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_chmod -- nginx (a separate uid in multi-container setups) must be able to create/append the log; WP_Filesystem layers ownership overrides that defeat that intent.
2979	@chmod( $dir, 0777 ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- best-effort; the access_log just stays empty if it fails.
2980	}
2981
2982	$path = self::hits_log_path();
2983	if ( ! file_exists( $path ) ) {
2984	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_touch -- See docblock: must be a plain touch, not WP_Filesystem.
2985	@touch( $path ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- non-fatal helper; failures already covered by the dir check.
2986	}
2987
2988	if ( $is_nginx ) {
2989	// World-writable so a different-uid nginx can append HIT lines.
2990	// Off nginx the drop-in appends as the same uid that owns the file,
2991	// so this is unnecessary — and would emit the "Operation not
2992	// permitted" warnings the old early return was added to silence.
2993	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_chmod -- See docblock.
2994	@chmod( $path, 0666 ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- best-effort.
2995	}
2996
2997	return file_exists( $path );
2998	}
2999
3000	public static function nginx_snippet(): ?string {
3001	if ( Server::NGINX !== Server::type() ) {
3002	return null;
3003	}
3004	$rel = '/' . ltrim( str_replace( ABSPATH, '/', XSPEED_CACHE_STATIC_DIR ), '/' );
3005	$rel = rtrim( $rel, '/' );
3006
3007	// WP-Rocket-canonical pattern: every condition lives at
3008	// SERVER level (outside any location block). Each one appends
3009	// a tag to $xspeed_no_cache; the final check is a single
3010	// string-equality against the unmodified default "no-cache".
3011	// Only when ALL conditions pass does the rewrite fire,
3012	// jumping the request to the static file's URL. nginx then
3013	// restarts location matching against the new path, where
3014	// regular static-file serving takes over.
3015	//
3016	// Why server-level + a single rewrite (instead of try_files
3017	// inside `location /`): nginx's well-documented "if is evil"
3018	// quirk silently disables `try_files`'s last fallback when
3019	// any `if` in the same location is true. Moving the `if`s
3020	// outside any location dodges the trap completely, because
3021	// server-level rewrite is the documented stable path.
3022	//
3023	// `last` (not `break`) restarts location matching — required
3024	// so the rewritten static-file URI gets served via the normal
3025	// static-file location, not re-matched against `location /`
3026	// where our own rewrite would loop.
3027	//
3028	// The cache existence check is the LAST condition in the
3029	// chain so when the file isn't cached, $xspeed_no_cache
3030	// gets a "-nofile" tag and the rewrite is skipped — the
3031	// request falls through to whatever `location /` the user
3032	// already had (typically `try_files $uri $uri/ /index.php?$args;`).
3033	// Absolute path to the hit-log file from the nginx process's
3034	// filesystem view. Nginx's `access_log buffer=N flush=Ns` form
3035	// requires a literal path — `$document_root` variables are
3036	// rejected — so PHP computes it. Lives under uploads/ (NOT the
3037	// cache dir): a cache purge or uninstall deletes the cache dir,
3038	// which would orphan this directive's parent directory and make
3039	// `nginx -t` fail [emerg] for EVERY vhost on the host
3040	// (FBS-82478). uploads/ survives both, so the directive can
3041	// never take nginx down. Works on every topology where the nginx
3042	// process shares a filesystem with PHP (container or host).
3043	$hits_abs = self::hits_log_path();
3044
3045	$lines = array();
3046	$lines[] = '# xSpeed static cache — paste at server level, above location / { }.';
3047	// Cache host must match the on-disk dir PHP writes: store_static() /
3048	// static_host() take HTTP_HOST and strip every char outside
3049	// [a-zA-Z0-9.\-] — i.e. it removes the colon but KEEPS the port digits
3050	// (localhost:8192 → localhost8192). nginx's own $host can't reproduce
3051	// that: $host has the port already stripped ENTIRELY (→ localhost), so
3052	// the -f check looks for localhost/... while PHP wrote localhost8192/...
3053	// and the rewrite never fires on a non-standard port. Derive
3054	// $xspeed_host from $http_host (which keeps the port) and drop just the
3055	// colon, so it equals the PHP dir on every port. On standard ports
3056	// $http_host has no colon, so $xspeed_host == $host == the bare domain.
3057	$lines[] = 'set $xspeed_host $http_host;'; // default: no port → unchanged (e.g. example.com)
3058	$lines[] = 'if ($http_host ~ "^([^:]+):(\\d+)$") { set $xspeed_host $1$2; }'; // host:port → hostport (matches PHP static_host())
3059	$lines[] = 'set $xspeed_no_cache "no-cache";';
3060	$lines[] = 'if ($request_method != GET) { set $xspeed_no_cache "$xspeed_no_cache-method"; }';
3061	$lines[] = 'if ($args) { set $xspeed_no_cache "$xspeed_no_cache-args"; }';
3062	// Cookie + user-agent exclusions, generated from the user's actual
3063	// settings rather than a hardcoded list. Before this, the rule
3064	// tested three fixed cookie names and no user agent at all, so
3065	// every excluded_cookies / bypass_user_agents entry applied only
3066	// while a page was cold — on a warm page nginx served the shared
3067	// anonymous copy to carts, members and bypassed bots alike. The
3068	// three historical names survive as a floor inside cookie_rule().
3069	// `~*` is case-insensitive, matching PHP's stripos()/glob checks.
3070	$cache_opts = Settings_Manager::get( 'cache' );
3071	$cookie_rule = Server_Rules::cookie_rule(
3072	is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array()
3073	);
3074	$lines[] = 'if ($http_cookie ~* "(' . $cookie_rule['regex'] . ')") { set $xspeed_no_cache "$xspeed_no_cache-cookie"; }';
3075
3076	$ua_rule = Server_Rules::user_agent_rule(
3077	is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array()
3078	);
3079	// Emitted only when the list is non-empty — an empty alternation
3080	// would compile to `(...)` matching every request and disable the
3081	// fast path entirely.
3082	if ( '' !== $ua_rule['regex'] ) {
3083	$lines[] = 'if ($http_user_agent ~* "(' . $ua_rule['regex'] . ')") { set $xspeed_no_cache "$xspeed_no_cache-ua"; }';
3084	}
3085	$lines[] = 'if (!-f "$document_root' . $rel . '/$xspeed_host$uri/index.html") { set $xspeed_no_cache "$xspeed_no_cache-nofile"; }';
3086	// Neither `add_header` nor `access_log` is allowed inside an `if{}`
3087	// at server level (nginx rejects with "directive is not allowed
3088	// here"). The logging therefore lives in a `location` block that
3089	// matches the rewritten URI after `rewrite … last;` restarts
3090	// location matching. Every HIT lands there exactly once, every
3091	// MISS / PHP-served request never matches it.
3092	$lines[] = 'if ($xspeed_no_cache = "no-cache") {';
3093	$lines[] = ' rewrite ^ ' . $rel . '/$xspeed_host$uri/index.html last;';
3094	$lines[] = '}';
3095	$lines[] = '';
3096	$lines[] = '# Serve + log the cached HIT — `^~` is required so this beats any regex location.';
3097	$lines[] = 'location ^~ ' . $rel . '/ {';
3098	$lines[] = ' internal;';
3099	// LITERAL log path (not `set $var; access_log $var`). The variable form
3100	// makes nginx open the log lazily per-request and SILENTLY drop the
3101	// line if the open fails — so on a working host hits were served
3102	// (X-XSpeed-Cache fires regardless) but nothing was ever written and
3103	// the hit ratio sat at 0%. A literal path makes nginx open the file at
3104	// config load and actually log every hit.
3105	//
3106	// Deleting the log FILE is still safe with a literal path: nginx
3107	// recreates it on the next write/reload and `nginx -t` stays green
3108	// (verified). The only thing that [emerg]s `nginx -t` is a missing
3109	// parent DIRECTORY — and the log lives under uploads/xspeed/, which
3110	// survives cache purge + uninstall, and which ensure_hits_log_file()
3111	// (run on every admin_init via auto_heal) recreates if it ever goes
3112	// missing. So: hits are logged, and a user deleting the log can't take
3113	// nginx down.
3114	$lines[] = ' access_log ' . $hits_abs . ' combined buffer=16k flush=5s;';
3115	$lines[] = ' add_header X-XSpeed-Cache "HIT (nginx)" always;';
3116	$lines[] = '}';
3117	return implode( "\n", $lines );
3118	}
3119
3120	/**
3121	* Aggregate every enabled module's nginx_directives() into one
3122	* pasteable server-block snippet. Replaces the per-module "paste
3123	* this snippet" notices with a single consolidated paste — every
3124	* future feature toggle just regenerates this output.
3125	*
3126	* Returns null on non-nginx hosts (nothing to paste).
3127	*
3128	* Sections render in module-registration order so the layout stays
3129	* predictable; each module gets a comment header `# <slug>`.
3130	*/
3131	public static function full_nginx_server_block(): ?string {
3132	if ( Server::NGINX !== Server::type() ) {
3133	return null;
3134	}
3135
3136	$blocks = array();
3137	foreach ( Module_Registry::all() as $module ) {
3138	$directives = $module->nginx_directives();
3139	if ( ! is_string( $directives ) \|\| '' === trim( $directives ) ) {
3140	continue;
3141	}
3142	$blocks[] = "# === " . $module->slug() . " ===\n" . rtrim( $directives );
3143	}
3144
3145	if ( empty( $blocks ) ) {
3146	return null;
3147	}
3148
3149	$header = "# xSpeed unified nginx config — paste into `server { }`, above `location / { }`; re-paste after toggling features.\n";
3150
3151	return $header . "\n" . implode( "\n\n", $blocks ) . "\n";
3152	}
3153
3154	/**
3155	* Tell LiteSpeed's LSCache module to stand down on the cache-miss
3156	* render path.
3157	*
3158	* History: this method used to emit X-LiteSpeed-Cache-Control:
3159	* public,max-age=N + X-LiteSpeed-Tag, handing caching to the server's
3160	* LSCache store. That delegation backfired — once LSCache cached a
3161	* page it served every subsequent request from its OWN store and
3162	* intercepted the request before our site-root .htaccess static
3163	* rewrite could run. Net effect on LiteSpeed hosts: no X-XSpeed-Cache
3164	* header, our static-cache tree never served, the HIT log never
3165	* written (hit ratio frozen at 0%), and the Health probe reporting a
3166	* false "cache running on PHP fallback" because it never saw an
3167	* xSpeed-served response.
3168	*
3169	* xSpeed now owns the cache on LiteSpeed exactly as it does on Apache:
3170	* our `.htaccess` mod_rewrite block serves hits straight from the
3171	* static-cache tree (with the X-XSpeed-Cache header + access-log HIT
3172	* accounting), and PHP/the drop-in is the fallback. To guarantee
3173	* LSCache doesn't shadow that with its own copy — some LiteSpeed
3174	* configs cache by default — we send an explicit `no-cache` control so
3175	* the server defers to our rewrite. Skipped when the LiteSpeed Cache
3176	* plugin is active (it owns its own header policy; our Conflict
3177	* registry handles that coexistence separately).
3178	*/
3179	public static function maybe_emit_lscache_headers(): void {
3180	if ( headers_sent() ) {
3181	return;
3182	}
3183	if ( Server::LITESPEED !== Server::type() ) {
3184	return;
3185	}
3186	// is_plugin_active() lives in wp-admin/includes/plugin.php which
3187	// isn't auto-loaded on front-end requests. Use the option layer
3188	// directly to avoid pulling in admin code from a render path.
3189	$active = (array) get_option( 'active_plugins', array() );
3190	if ( in_array( 'litespeed-cache/litespeed-cache.php', $active, true ) ) {
3191	return;
3192	}
3193
3194	// Explicitly opt this response OUT of LSCache so the server can't
3195	// shadow our static-rewrite cache with its own internal copy.
3196	header( 'X-LiteSpeed-Cache-Control: no-cache' );
3197	}
3198
3199	/**
3200	* Restore the drop-in + WP_CACHE constant for a site that had caching
3201	* ON before this activation — and ONLY for such a site.
3202	*
3203	* WordPress runs an upgrade as deactivate → wipe plugin files →
3204	* install → activate. The wipe takes advanced-cache.php with it, so
3205	* without this the site serves 100% uncached from the moment the
3206	* update finishes until the next authenticated wp-admin page load
3207	* (auto_heal() is on admin_init). On a site whose admin logs in
3208	* rarely that window is hours or days of silent cache loss, while
3209	* the dashboard still reports cache_enabled = true. (FBS field
3210	* report against 1.1.2 / Pro 1.0.5.)
3211	*
3212	* The `cache_enabled` guard is the whole contract: a FRESH install
3213	* has the option unset, so activation writes nothing and the user
3214	* still opts in explicitly through Cache::toggle() via the
3215	* /cache/toggle REST endpoint. We only ever put back state the user
3216	* already chose — repair, never a new install path. This is what
3217	* keeps us on the right side of the "don't create drop-ins the user
3218	* didn't ask for" guideline while matching what WP Rocket, W3 Total
3219	* Cache and WP Super Cache all do on activation.
3220	*
3221	* @return bool True when a restore was performed.
3222	*/
3223	public static function restore_dropin_if_enabled(): bool {
3224	if ( defined( 'WP_INSTALLING' ) && WP_INSTALLING ) {
3225	return false;
3226	}
3227
3228	// The user's saved choice. Absent/false on a fresh install => no
3229	// drop-in is written and nothing touches wp-config.php.
3230	$opts = get_option( 'xspeed_options', array() );
3231	if ( empty( $opts['cache_enabled'] ) ) {
3232	return false;
3233	}
3234
3235	$restored = false;
3236
3237	// Only (re)install when the drop-in is missing, foreign, or an
3238	// older version of ours — never rewrite a current, healthy file.
3239	$target = WP_CONTENT_DIR . '/advanced-cache.php';
3240	$needs = true;
3241	if ( file_exists( $target ) ) {
3242	$contents = @file_get_contents( $target ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Best-effort read; a failure just means we reinstall.
3243	if ( is_string( $contents ) && false !== strpos( $contents, 'XSPEED_DROPIN' ) ) {
3244	$source = @file_get_contents( XSPEED_DIR . 'includes/advanced-cache.php' ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Same.
3245	$needs = self::dropin_version( $contents ) < self::dropin_version( is_string( $source ) ? $source : '' );
3246	}
3247	}
3248	if ( $needs && self::install_dropin() ) {
3249	$restored = true;
3250	}
3251
3252	// WP_CACHE lives in wp-config.php, which the upgrade doesn't touch —
3253	// but a foreign cache plugin or a hand-edit can drop it, and without
3254	// it core never loads the drop-in at all.
3255	if ( ! defined( 'WP_CACHE' ) \|\| ! WP_CACHE ) {
3256	if ( self::set_wp_cache_constant( true ) ) {
3257	$restored = true;
3258	}
3259	}
3260
3261	if ( $restored ) {
3262	Activity_Log::record(
3263	'cache_dropin_restored',
3264	'Cache drop-in restored after a plugin update — caching was already enabled.',
3265	Activity_Log::SUCCESS
3266	);
3267	}
3268
3269	return $restored;
3270	}
3271
3272	/**
3273	* Reconcile drop-in + WP_CACHE + rewrite block with the user's
3274	* saved choice. Runs on admin_init. Cheap when nothing's wrong
3275	* (one option read + a handful of file_exists / defined checks);
3276	* writes only when state has drifted (typical cause: plugin
3277	* upgrade wiped the drop-in, foreign plugin removed our WP_CACHE
3278	* define, or someone hand-edited .htaccess).
3279	*
3280	* Skipped during the WP plugin updater run so we don't race
3281	* the upgrader's own filesystem operations.
3282	*/
3283	public static function auto_heal(): void {
3284	if ( defined( 'WP_INSTALLING' ) && WP_INSTALLING ) {
3285	return;
3286	}
3287	if ( wp_doing_ajax() \|\| wp_doing_cron() ) {
3288	return;
3289	}
3290
3291	$opts = get_option( 'xspeed_options', array() );
3292	if ( empty( $opts['cache_enabled'] ) ) {
3293	return;
3294	}
3295
3296	$dropin_target = WP_CONTENT_DIR . '/advanced-cache.php';
3297	$dropin_ours = false;
3298	$dropin_stale = false;
3299	if ( file_exists( $dropin_target ) ) {
3300	$contents = @file_get_contents( $dropin_target ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3301	$dropin_ours = is_string( $contents ) && false !== strpos( $contents, 'XSPEED_DROPIN' );
3302	// Reinstall when OUR drop-in is an older version than the source —
3303	// the marker alone can't distinguish an old copy from a new one, so
3304	// a serve-logic change (e.g. the .meta read for 404s/feeds) would
3305	// otherwise never reach existing cache-enabled sites until a manual
3306	// cache toggle. (FBS-82406/82407)
3307	if ( $dropin_ours ) {
3308	$dropin_stale = self::dropin_version( (string) $contents ) < self::dropin_version( @file_get_contents( XSPEED_DIR . 'includes/advanced-cache.php' ) ?: '' ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3309	}
3310	}
3311
3312	if ( ! $dropin_ours \|\| $dropin_stale ) {
3313	self::install_dropin();
3314	}
3315
3316	if ( ! defined( 'WP_CACHE' ) \|\| ! WP_CACHE ) {
3317	self::set_wp_cache_constant( true );
3318	}
3319
3320	// Rewrite block goes last. It's what turns the static-cache
3321	// tree into a PHP-bypass — every cache hit served by the web
3322	// server directly. Without it we still cache, just at drop-in
3323	// speed (~85ms TTFB) instead of static-file speed (~25-40ms).
3324	//
3325	// Reconcile against mobile_separate: the rewrite is device-blind, so
3326	// it must be ABSENT when mobile_separate is on and PRESENT otherwise.
3327	// auto_heal() runs periodically, so it also repairs a rewrite that
3328	// was left installed before mobile_separate was switched on.
3329	if ( self::static_rewrite_allowed() ) {
3330	if ( ! self::rewrite_installed() ) {
3331	self::install_rewrite();
3332	}
3333	} elseif ( self::rewrite_installed() ) {
3334	self::remove_rewrite();
3335	}
3336
3337	// HITs log file — nginx writes one line per HIT served directly
3338	// (see nginx_snippet()), Cache::get_stats() drains the file via
3339	// Hit_Counter::collect_nginx_log_hits(). If the file vanishes
3340	// (plugin upgrade wiped wp-content/cache/), nginx errors silently
3341	// on the access_log directive and the counter stays at 0.
3342	self::ensure_hits_log_file();
3343	}
3344
3345	/**
3346	* Keep the generic bypass cookie in sync with PHP's caching verdict.
3347	*
3348	* The server config tests exactly one cookie name (Server_Rules::
3349	* BYPASS_COOKIE) forever, and PHP decides what that name means. Adding
3350	* a new excluded cookie therefore needs no config change and no nginx
3351	* reload — the reason this exists.
3352	*
3353	* Session cookie (expiry 0) so it dies with the browser session, and
3354	* deliberately NOT HttpOnly-sensitive: it carries no identity, only the
3355	* boolean "don't serve this visitor a shared cached page".
3356	*
3357	* Honest limit: this can only ever help a visitor PHP has already seen
3358	* once. A bot's first request to a warm page never reaches PHP, which
3359	* is why user-agent rules are still written into the server config
3360	* rather than relying on this.
3361	*
3362	* @param bool $bypass Whether this visitor must skip the cache.
3363	*/
3364	private static function sync_bypass_cookie( bool $bypass ): void {
3365	if ( headers_sent() ) {
3366	return;
3367	}
3368
3369	$name = Server_Rules::BYPASS_COOKIE;
3370	$has = isset( $_COOKIE[ $name ] );
3371
3372	// Only touch the header when the state actually changes — a
3373	// Set-Cookie on every request would make the response uncacheable
3374	// for intermediary caches and add noise to every hit.
3375	if ( $bypass === $has ) {
3376	return;
3377	}
3378
3379	$path = defined( 'COOKIEPATH' ) && COOKIEPATH ? COOKIEPATH : '/';
3380	$domain = defined( 'COOKIE_DOMAIN' ) ? COOKIE_DOMAIN : '';
3381
3382	if ( $bypass ) {
3383	setcookie( $name, '1', 0, $path, (string) $domain, is_ssl(), false );
3384	$_COOKIE[ $name ] = '1';
3385	} else {
3386	setcookie( $name, '', time() - 3600, $path, (string) $domain, is_ssl(), false );
3387	unset( $_COOKIE[ $name ] );
3388	}
3389	}
3390
3391	/**
3392	* Build the .htaccess rules that map cacheable requests to the
3393	* static-cache tree. Conditions are deliberately strict: GET only,
3394	* empty query string, no session/comment-author/post-password
3395	* cookie, and the static file must exist on disk. Anything that
3396	* fails one of these falls through to PHP and the drop-in / full
3397	* WordPress path.
3398	*
3399	* @return string[] Lines for insert_with_markers().
3400	*/
3401	public static function rewrite_block_lines(): array {
3402	// Path relative to ABSPATH so the rule lives in the site-root
3403	// .htaccess regardless of where wp-content sits. WP_CONTENT_DIR
3404	// can be moved, so we compute the document-root-relative form
3405	// at install time and bake it into the rule.
3406	$rel = str_replace( ABSPATH, '/', XSPEED_CACHE_STATIC_DIR );
3407	$rel = '/' . ltrim( $rel, '/' );
3408	$rel = rtrim( $rel, '/' );
3409
3410	// Cookie + user-agent exclusions generated from the live settings.
3411	// See the matching block in nginx_snippet() — same generator, same
3412	// floor, so both servers enforce an identical policy. Apache reads
3413	// .htaccess on every request and we already self-heal this file, so
3414	// Apache/LiteSpeed users get the fix on upgrade with no action.
3415	$cache_opts = Settings_Manager::get( 'cache' );
3416	$cookie_rule = Server_Rules::cookie_rule(
3417	is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array()
3418	);
3419	$ua_rule = Server_Rules::user_agent_rule(
3420	is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array()
3421	);
3422
3423	$lines = array(
3424	'<IfModule mod_rewrite.c>',
3425	' RewriteEngine On',
3426	' RewriteCond %{REQUEST_METHOD} ^GET$',
3427	' RewriteCond %{QUERY_STRING} ^$',
3428	' RewriteCond %{HTTP_COOKIE} !(' . $cookie_rule['regex'] . ') [NC]',
3429	);
3430
3431	// Only emit the UA condition when there's something to match —
3432	// `!()` would negate an always-true empty match and refuse every
3433	// request, silently disabling the static path.
3434	if ( '' !== $ua_rule['regex'] ) {
3435	// Quoted, because RewriteCond is whitespace-delimited and real
3436	// user-agent fragments contain spaces ("Mozilla/5.0 (compatible").
3437	// Unquoted, a space adds an argument and Apache answers every
3438	// request with a 500 — and because .htaccess is parsed per
3439	// request, `httpd -t` still reports Syntax OK. Server_Rules has
3440	// already excluded quotes and backslashes from the alternation,
3441	// so the closing quote here cannot be escaped away.
3442	$lines[] = ' RewriteCond %{HTTP_USER_AGENT} "!(' . $ua_rule['regex'] . ')" [NC]';
3443	}
3444
3445	return array_merge(
3446	$lines,
3447	array(
3448	// Capture REQUEST_URI without its trailing slash into %1.
3449	// store_static() writes `{host}{uri-without-trailing-slash}/index.html`,
3450	// so this normalization lets `/blog/` and `/blog` both hit
3451	// the same cache file without producing the double-slash
3452	// path that would skip the -f check below.
3453	' RewriteCond %{REQUEST_URI} ^(.*?)/?$',
3454	' RewriteCond %{DOCUMENT_ROOT}' . $rel . '/%{HTTP_HOST}%1/index.html -f',
3455	// Pattern is `^`, NOT `.`. The per-directory rewrite engine
3456	// strips the leading slash before matching, so the HOMEPAGE
3457	// request `/` arrives here as an EMPTY path. `.` requires at
3458	// least one character and therefore never matches the homepage
3459	// — on LiteSpeed (which honors this strictly) the front page
3460	// fell through to PHP while every inner page rewrote fine.
3461	// `^` matches the empty string AND any non-empty path, so it
3462	// covers `/` and `/blog` alike. (Confirmed on OpenLiteSpeed
3463	// 1.8: `.` → homepage served by PHP drop-in; `^` → served
3464	// directly from the static file.)
3465	' RewriteRule ^ ' . $rel . '/%{HTTP_HOST}%1/index.html [L]',
3466	'</IfModule>',
3467	// Mark the statically-served response as a cache HIT.
3468	//
3469	// A file served by the rewrite above bypasses PHP entirely, so
3470	// this directive is the ONLY thing that can identify it as
3471	// cached — both for the user reading response headers and for
3472	// Hit_Counter, which reconciles static hits from the access
3473	// log. Without it the cache works perfectly and reports a 0%
3474	// hit ratio, which reads as "the plugin is broken". (Field
3475	// report against 1.1.2: homepage served byte-identical from
3476	// the static tree, no X-XSpeed-Cache header on any response.)
3477	//
3478	// `always` so the header is set on the 200 from the rewritten
3479	// file, not only on the successful-response table. The
3480	// <IfModule> guard keeps a server without mod_headers from
3481	// 500ing on an unknown directive — on such a host the header
3482	// is silently dropped, which is exactly why
3483	// static_rewrite_allowed() refuses the static path there and
3484	// routes hits through the drop-in instead.
3485	'<IfModule mod_headers.c>',
3486	' <FilesMatch "\\.html$">',
3487	' Header always set X-XSpeed-Cache "HIT (static)"',
3488	' </FilesMatch>',
3489	'</IfModule>',
3490	)
3491	);
3492	}
3493
3494	/**
3495	* Active probe that confirms the web-server static-rewrite path is
3496	* actually serving cached files. Writes a probe file with a random
3497	* nonce, fetches it over HTTP at its public URL, and checks whether
3498	* the response was served directly by the web server (Last-Modified
3499	* + ETag headers + no X-Powered-By: PHP).
3500	*
3501	* Server-agnostic: same probe works for nginx (snippet pasted) and
3502	* Apache / LiteSpeed (.htaccess block installed). If the rewrite
3503	* isn't engaged, the request falls through to WordPress and PHP
3504	* adds its own headers, which the probe detects and reports.
3505	*
3506	* Throttled via a 5-minute transient — we never want this running
3507	* on every Health card paint.
3508	*
3509	* @return array{active:bool, reason:string, code?:int, php?:bool, expires?:int}
3510	*/
3511	/**
3512	* @param bool $allow_probe When false (the default), return ONLY a cached
3513	* result and never make an HTTP request — so admin page loads are never
3514	* blocked by the loopback probe. The actual HTTP probe only runs when a
3515	* caller explicitly opts in (the Health tab / cron). Previously this ran
3516	* synchronously on every dashboard bootstrap, so a slow/timing-out
3517	* loopback request added up to `timeout` seconds to admin page loads on
3518	* hosts that block self-requests. (FBS-82142)
3519	*/
3520	/**
3521	* Discard the cached probe result and run a fresh one.
3522	*
3523	* Without this there was no way to re-check: the result sat in a transient
3524	* for five minutes and nothing ever deleted it, so a user who fixed their
3525	* nginx config kept seeing "nginx detected — configure for max cache speed"
3526	* with no means of confirming the fix worked. (FBS-84012)
3527	*/
3528	public static function recheck_static_rewrite(): array {
3529	delete_transient( 'xspeed_rewrite_probe' );
3530	return self::probe_static_rewrite( true );
3531	}
3532
3533	public static function probe_static_rewrite( bool $allow_probe = false ): array {
3534	$cached = get_transient( 'xspeed_rewrite_probe' );
3535	if ( is_array( $cached ) ) {
3536	return $cached;
3537	}
3538	// No cached result yet and the caller doesn't want to pay for a live
3539	// HTTP probe (e.g. the admin bootstrap): report "pending" without
3540	// blocking. The Health tab will run the real probe on demand.
3541	if ( ! $allow_probe ) {
3542	return array( 'active' => false, 'reason' => 'probe pending', 'pending' => true );
3543	}
3544
3545	$home = home_url( '/' );
3546	$host = (string) wp_parse_url( $home, PHP_URL_HOST );
3547	if ( '' === $host ) {
3548	$result = array( 'active' => false, 'reason' => 'home_url has no host' );
3549	set_transient( 'xspeed_rewrite_probe', $result, MINUTE_IN_SECONDS );
3550	return $result;
3551	}
3552
3553	// Use a randomised path AND nonce so a stale CDN cache entry
3554	// from a prior probe can never make a broken install look
3555	// healthy. Path is namespaced under __xspeed_probe__ so the
3556	// directory listing stays obvious if cleanup misfires.
3557	$slug = wp_generate_password( 12, false, false );
3558	$nonce = wp_generate_password( 24, false, false );
3559	$probe_dir = XSPEED_CACHE_STATIC_DIR . '/' . $host . '/__xspeed_probe__/' . $slug;
3560	$probe_file = $probe_dir . '/index.html';
3561	$probe_url = trailingslashit( $home ) . '__xspeed_probe__/' . $slug . '/';
3562
3563	if ( ! file_exists( $probe_dir ) ) {
3564	wp_mkdir_p( $probe_dir );
3565	}
3566	if ( ! is_dir( $probe_dir ) ) {
3567	$result = array( 'active' => false, 'reason' => 'cannot create probe dir' );
3568	set_transient( 'xspeed_rewrite_probe', $result, MINUTE_IN_SECONDS );
3569	return $result;
3570	}
3571	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents -- WP_Filesystem requires admin credentials we may not have here; the file is in our own cache dir.
3572	file_put_contents( $probe_file, $nonce, LOCK_EX );
3573
3574	// Verify TLS by default — disabling it site-wide is a needless MITM
3575	// exposure (FBS-82142). Only relax verification in local/dev
3576	// environments, where self-signed certs are common and there's no
3577	// real attacker in the loop.
3578	$is_local = function_exists( 'wp_get_environment_type' )
3579	&& in_array( wp_get_environment_type(), array( 'local', 'development' ), true );
3580	$resp = wp_remote_get(
3581	$probe_url,
3582	array(
3583	// 3s cap so a host that hangs on loopback self-requests can't
3584	// stall the caller for long; the result/error is cached so we
3585	// don't repeat the wait every minute.
3586	'timeout' => 3,
3587	'sslverify' => ! $is_local,
3588	'redirection' => 0,
3589	'headers' => array( 'Cache-Control' => 'no-cache' ),
3590	)
3591	);
3592
3593	// Best-effort cleanup so we don't accumulate probe dirs even
3594	// if subsequent calls all hit the transient.
3595	if ( file_exists( $probe_file ) ) {
3596	wp_delete_file( $probe_file );
3597	}
3598	if ( is_dir( $probe_dir ) ) {
3599	// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, WordPress.WP.AlternativeFunctions.file_system_operations_rmdir -- Best-effort probe-dir cleanup; WP_Filesystem needs admin credentials we don't have here.
3600	@rmdir( $probe_dir );
3601	}
3602
3603	if ( is_wp_error( $resp ) ) {
3604	$result = array(
3605	'active' => false,
3606	// The request never completed, so we learned NOTHING about the
3607	// rewrite. Flagged inconclusive so the UI doesn't tell the user
3608	// to configure a server that may already be configured — a
3609	// blocked loopback, a self-signed cert, or a timeout is a probe
3610	// failure, not a missing rewrite. (FBS-84012)
3611	'inconclusive' => true,
3612	'reason' => 'http error: ' . $resp->get_error_message(),
3613	);
3614	// Cache the failure for the full 5 minutes (not 1) so a host that
3615	// times out on the loopback probe isn't re-probed — and re-stalled
3616	// — on every page load within the window. (FBS-82142)
3617	set_transient( 'xspeed_rewrite_probe', $result, 5 * MINUTE_IN_SECONDS );
3618	return $result;
3619	}
3620
3621	$code = (int) wp_remote_retrieve_response_code( $resp );
3622	$body = (string) wp_remote_retrieve_body( $resp );
3623	$ua_php = '' !== (string) wp_remote_retrieve_header( $resp, 'x-powered-by' );
3624	$has_etag = '' !== (string) wp_remote_retrieve_header( $resp, 'etag' )
3625	\|\| '' !== (string) wp_remote_retrieve_header( $resp, 'last-modified' );
3626	$match = trim( $body ) === $nonce;
3627
3628	// "Active" = the web server served our raw nonce bytes back
3629	// AND emitted the static-serve markers (ETag / Last-Modified)
3630	// AND didn't add an X-Powered-By: PHP header. All three are
3631	// individually noisy; together they're conclusive.
3632	$active = $match && $has_etag && ! $ua_php && 200 === $code;
3633
3634	/*
3635	* `inconclusive` separates "we proved the rewrite isn't serving" from
3636	* "the probe couldn't tell". Only the former should drive a
3637	* configure-your-server banner; the latter previously rendered the
3638	* same alarming copy at a user who had already configured nginx
3639	* correctly, and there was no way to clear it. (FBS-84012)
3640	*/
3641	$inconclusive = false;
3642	if ( $active ) {
3643	$reason = 'static-served';
3644	} elseif ( 200 === $code && $match && $ua_php ) {
3645	$reason = 'php served the file instead of nginx/Apache (rewrite block missing)';
3646	} elseif ( 200 === $code && ! $match ) {
3647	// Something answered 200 with content that isn't our nonce — a CDN,
3648	// a proxy, a security plugin. That tells us nothing about the
3649	// origin's rewrite.
3650	$reason = 'unexpected body (CDN cached an older response?)';
3651	$inconclusive = true;
3652	} elseif ( 404 === $code ) {
3653	$reason = 'probe URL returned 404 (rewrite block missing or wrong path)';
3654	} else {
3655	// Redirects, 403s from a WAF, 5xx — the probe never reached a
3656	// verdict about the rewrite itself.
3657	$reason = sprintf( 'unexpected response (HTTP %d, body %d B, php=%s)', $code, strlen( $body ), $ua_php ? 'yes' : 'no' );
3658	$inconclusive = true;
3659	}
3660
3661	$result = array(
3662	'active' => $active,
3663	'inconclusive' => $inconclusive,
3664	'reason' => $reason,
3665	'code' => $code,
3666	'php' => $ua_php,
3667	);
3668	set_transient( 'xspeed_rewrite_probe', $result, 5 * MINUTE_IN_SECONDS );
3669	return $result;
3670	}
3671
3672	public static function rewrite_installed(): bool {
3673	$htaccess = ABSPATH . '.htaccess';
3674	if ( ! file_exists( $htaccess ) ) {
3675	return false;
3676	}
3677	$existing = @file_get_contents( $htaccess ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3678	if ( ! is_string( $existing ) ) {
3679	return false;
3680	}
3681	return false !== strpos( $existing, '# BEGIN xSpeed Static Cache' );
3682	}
3683
3684	/**
3685	* Install the static-cache rewrite block at the TOP of .htaccess.
3686	*
3687	* Position matters: WordPress's own block ends with
3688	* `RewriteRule . /index.php [L]` which routes every non-file
3689	* request to PHP. The [L] flag stops the current rewrite pass,
3690	* but Apache restarts the cycle; on the second pass REQUEST_URI
3691	* is /index.php and no static-file check can match. The only
3692	* reliable position for a "serve static if it exists" rule is
3693	* before WordPress's block.
3694	*
3695	* WP's insert_with_markers() always appends, so we manage the
3696	* block manually: strip any prior xSpeed Static Cache markers,
3697	* then write our block followed by the rest of the file.
3698	*/
3699	public static function install_rewrite(): bool {
3700	// The static rewrite is device-blind; never install it when
3701	// mobile_separate is on (see static_rewrite_allowed()).
3702	if ( ! self::static_rewrite_allowed() ) {
3703	return false;
3704	}
3705	$htaccess = ABSPATH . '.htaccess';
3706	$existing = file_exists( $htaccess ) ? @file_get_contents( $htaccess ) : ''; // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3707	if ( false === $existing ) {
3708	$existing = '';
3709	}
3710	// Apache/LiteSpeed only. nginx hosts: rule won't fire, drop-in
3711	// covers; we skip the write so we don't litter their root.
3712	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- Pre-flight check before file_put_contents; WP_Filesystem requires admin credentials we don't have inside a manage_options REST request.
3713	if ( file_exists( $htaccess ) && ! is_writable( $htaccess ) ) {
3714	return false;
3715	}
3716	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- See above.
3717	if ( ! file_exists( $htaccess ) && ! is_writable( ABSPATH ) ) {
3718	return false;
3719	}
3720
3721	$cleaned = self::strip_marker_block( $existing, 'xSpeed Static Cache' );
3722	$block = self::marker_block( 'xSpeed Static Cache', self::rewrite_block_lines() );
3723	$next = $block . ( '' === $cleaned ? '' : "\n" . $cleaned );
3724
3725	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents, PluginCheck.CodeAnalysis.WriteFile.ABSPATHDetected -- WP_Filesystem requires admin credentials we don't have here; toggle() runs in a REST request authorized by manage_options nonce. The target is the site's .htaccess (configuration file managed by WP core itself), not user data — wp_upload_dir() doesn't apply.
3726	return false !== file_put_contents( $htaccess, $next, LOCK_EX );
3727	}
3728
3729	/**
3730	* Rewrite the .htaccess block in place when — and only when — one is
3731	* already installed.
3732	*
3733	* The block embeds the generated cookie / user-agent exclusion rules,
3734	* so it goes stale the moment those settings change. install_rewrite()
3735	* regenerates it from the live settings, but calling that unconditionally
3736	* on every save would CREATE a block on sites that never enabled the
3737	* static path — silently turning on server-level serving nobody asked
3738	* for. So we refresh only what's already there.
3739	*
3740	* @return bool True when a block was present and rewritten.
3741	*/
3742	public static function refresh_rewrite_if_installed(): bool {
3743	$htaccess = ABSPATH . '.htaccess';
3744	if ( ! file_exists( $htaccess ) ) {
3745	return false;
3746	}
3747	$existing = @file_get_contents( $htaccess ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- Best-effort read; an unreadable file simply means nothing to refresh.
3748	if ( ! is_string( $existing ) \|\| false === strpos( $existing, '# BEGIN xSpeed Static Cache' ) ) {
3749	return false;
3750	}
3751	return self::install_rewrite();
3752	}
3753
3754	public static function remove_rewrite(): bool {
3755	$htaccess = ABSPATH . '.htaccess';
3756	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_is_writable -- See install_rewrite() rationale.
3757	if ( ! file_exists( $htaccess ) \|\| ! is_writable( $htaccess ) ) {
3758	return false;
3759	}
3760	$existing = @file_get_contents( $htaccess ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
3761	if ( false === $existing ) {
3762	return false;
3763	}
3764	$cleaned = self::strip_marker_block( $existing, 'xSpeed Static Cache' );
3765	// phpcs:ignore WordPress.WP.AlternativeFunctions.file_put_contents_file_put_contents, PluginCheck.CodeAnalysis.WriteFile.ABSPATHDetected -- See install_rewrite() rationale.
3766	return false !== file_put_contents( $htaccess, $cleaned, LOCK_EX );
3767	}
3768
3769	/**
3770	* Strip a `# BEGIN <marker>` ... `# END <marker>` block from a
3771	* .htaccess-style file, including any blank line that immediately
3772	* follows it. Idempotent — returns the input unchanged if the
3773	* marker isn't present.
3774	*/
3775	private static function strip_marker_block( string $contents, string $marker ): string {
3776	$pattern = '/# BEGIN ' . preg_quote( $marker, '/' ) . '\b.?# END ' . preg_quote( $marker, '/' ) . "\b[^\n]\n?\n?/s";
3777	$out = preg_replace( $pattern, '', $contents );
3778	return is_string( $out ) ? $out : $contents;
3779	}
3780
3781	private static function marker_block( string $marker, array $lines ): string {
3782	$header = "# BEGIN $marker\n";
3783	$header .= "# The directives (lines) between \"BEGIN $marker\" and \"END $marker\" are\n";
3784	$header .= "# dynamically generated, and should only be modified via WordPress filters.\n";
3785	$header .= "# Any changes to the directives between these markers will be overwritten.\n";
3786	$footer = "# END $marker\n";
3787	return $header . implode( "\n", $lines ) . "\n" . $footer;
3788	}
3789
3790	/**
3791	* Parse the `XSPEED_DROPIN_VERSION: N` stamp out of a drop-in's source.
3792	* Returns 0 when absent (an un-stamped older copy reinstalls). Used to
3793	* detect a stale installed drop-in vs the bundled source.
3794	*/
3795	private static function dropin_version( string $contents ): int {
3796	if ( preg_match( '/XSPEED_DROPIN_VERSION:\s*(\d+)/', $contents, $m ) ) {
3797	return (int) $m[1];
3798	}
3799	return 0;
3800	}
3801
3802	public static function install_dropin() {
3803	$source = XSPEED_DIR . 'includes/advanced-cache.php';
3804	$target = WP_CONTENT_DIR . '/advanced-cache.php';
3805	if ( ! file_exists( $source ) ) {
3806	return false;
3807	}
3808
3809	global $wp_filesystem;
3810	if ( ! function_exists( 'WP_Filesystem' ) ) {
3811	require_once ABSPATH . 'wp-admin/includes/file.php';
3812	}
3813	WP_Filesystem();
3814	if ( ! $wp_filesystem ) {
3815	return false;
3816	}
3817
3818	$source_contents = $wp_filesystem->get_contents( $source );
3819	if ( ! is_string( $source_contents ) ) {
3820	return false;
3821	}
3822
3823	// Bake the absolute hit-log path into the drop-in. It runs before
3824	// WordPress loads, so it can't resolve wp_upload_dir() itself — we
3825	// substitute the @@XSPEED_HITS_LOG@@ token with the real uploads path
3826	// (never the cache dir; see hits_log_dir() / FBS-82478). Use a single
3827	// quoted PHP string literal so the installed file stays valid PHP.
3828	$source_contents = str_replace(
3829	'@@XSPEED_HITS_LOG@@',
3830	str_replace( "'", "\\'", self::hits_log_path() ),
3831	$source_contents
3832	);
3833
3834	// Bake the cookie + user-agent exclusion rules in too. The drop-in
3835	// runs before WordPress loads, so it cannot read the settings — and
3836	// without them it served the shared anonymous page to any visitor
3837	// PHP had not yet seen (a first-time cart visitor, a bypassed bot).
3838	// The generic bypass cookie only covers repeat visitors; these two
3839	// regexes are what make the FIRST request correct.
3840	//
3841	// Both are already fully escaped by Server_Rules, and each is
3842	// embedded as a single-quoted PHP literal, so a settings value can
3843	// neither break the drop-in's syntax nor execute.
3844	$cache_opts = Settings_Manager::get( 'cache' );
3845	$cookie_rule = Server_Rules::cookie_rule(
3846	is_array( $cache_opts['excluded_cookies'] ?? null ) ? $cache_opts['excluded_cookies'] : array()
3847	);
3848	$ua_rule = Server_Rules::user_agent_rule(
3849	is_array( $cache_opts['bypass_user_agents'] ?? null ) ? $cache_opts['bypass_user_agents'] : array()
3850	);
3851
3852	$source_contents = str_replace(
3853	'@@XSPEED_COOKIE_RE@@',
3854	str_replace( "'", "\\'", $cookie_rule['regex'] ),
3855	$source_contents
3856	);
3857	$source_contents = str_replace(
3858	'@@XSPEED_UA_RE@@',
3859	str_replace( "'", "\\'", $ua_rule['regex'] ),
3860	$source_contents
3861	);
3862
3863	if ( file_exists( $target ) ) {
3864	$existing = $wp_filesystem->get_contents( $target );
3865	$is_xspeed = is_string( $existing ) && false !== strpos( $existing, 'XSPEED_DROPIN' );
3866
3867	if ( $is_xspeed ) {
3868	if ( $existing === $source_contents ) {
3869	return true;
3870	}
3871	return (bool) $wp_filesystem->put_contents( $target, $source_contents, FS_CHMOD_FILE );
3872	}
3873
3874	// Foreign drop-in (e.g. left over from another cache plugin) — back it up
3875	// before overwriting so the user can recover if needed. Uploads dir
3876	// (not wp-content root) keeps the backup out of WordPress's reserved
3877	// drop-in location.
3878	$upload = wp_upload_dir( null, false );
3879	$basedir = isset( $upload['basedir'] ) ? trailingslashit( $upload['basedir'] ) . 'xspeed-backups' : false;
3880	if ( $basedir ) {
3881	if ( ! file_exists( $basedir ) ) {
3882	wp_mkdir_p( $basedir );
3883	self::write_silence( $basedir );
3884	}
3885	$backup = $basedir . '/advanced-cache.foreign-' . gmdate( 'Ymd-His' ) . '.php.bak';
3886	$wp_filesystem->move( $target, $backup, true );
3887	} else {
3888	$wp_filesystem->delete( $target );
3889	}
3890	}
3891
3892	return (bool) $wp_filesystem->put_contents( $target, $source_contents, FS_CHMOD_FILE );
3893	}
3894
3895	public static function remove_dropin() {
3896	$target = WP_CONTENT_DIR . '/advanced-cache.php';
3897	if ( ! file_exists( $target ) ) {
3898	return;
3899	}
3900
3901	global $wp_filesystem;
3902	if ( ! function_exists( 'WP_Filesystem' ) ) {
3903	require_once ABSPATH . 'wp-admin/includes/file.php';
3904	}
3905	WP_Filesystem();
3906	if ( ! $wp_filesystem ) {
3907	return;
3908	}
3909
3910	$contents = $wp_filesystem->get_contents( $target );
3911	if ( is_string( $contents ) && false !== strpos( $contents, 'XSPEED_DROPIN' ) ) {
3912	wp_delete_file( $target );
3913	}
3914	}
3915
3916	/**
3917	* Where wp-config.php actually is.
3918	*
3919	* WordPress core supports the file one directory ABOVE ABSPATH, and
3920	* plenty of installs use that layout. This used to look only in ABSPATH
3921	* and bail, so on those sites the constant could never be written — while
3922	* Health, which did fall back to the parent, reported the file writable
3923	* and told the user to toggle the cache off and on. The advice could
3924	* never work, and its fallback hint ("another plugin left WP_CACHE false
3925	* behind") was wrong too: there was no define at all. (#19, QA on #174)
3926	*
3927	* Returns '' when no wp-config.php can be found in either location.
3928	*/
3929	public static function wp_config_path(): string {
3930	$candidates = array( ABSPATH . 'wp-config.php', dirname( ABSPATH ) . '/wp-config.php' );
3931	foreach ( $candidates as $path ) {
3932	if ( file_exists( $path ) ) {
3933	return $path;
3934	}
3935	}
3936	return '';
3937	}
3938
3939	/**
3940	* Can we actually write the constant right now?
3941	*
3942	* This is the single oracle for that question — Health asks THIS rather
3943	* than running its own `wp_is_writable()` test, so the message a user
3944	* reads can never disagree with what the plugin will do. The two differed
3945	* in both directions: on the path (above) and on the test itself, since
3946	* an FTP/SSH WP_Filesystem transport can refuse a file that
3947	* `wp_is_writable()` reports as writable. (#19, QA on #174)
3948	*/
3949	public static function can_write_wp_config(): bool {
3950	$wp_config = self::wp_config_path();
3951	if ( '' === $wp_config ) {
3952	return false;
3953	}
3954
3955	global $wp_filesystem;
3956	if ( ! function_exists( 'WP_Filesystem' ) ) {
3957	require_once ABSPATH . 'wp-admin/includes/file.php';
3958	}
3959	WP_Filesystem();
3960	return (bool) ( $wp_filesystem && $wp_filesystem->is_writable( $wp_config ) );
3961	}
3962
3963	public static function set_wp_cache_constant( $enable ) {
3964	$wp_config = self::wp_config_path();
3965	if ( '' === $wp_config ) {
3966	return false;
3967	}
3968
3969	global $wp_filesystem;
3970	if ( ! function_exists( 'WP_Filesystem' ) ) {
3971	require_once ABSPATH . 'wp-admin/includes/file.php';
3972	}
3973	WP_Filesystem();
3974	if ( ! $wp_filesystem \|\| ! $wp_filesystem->is_writable( $wp_config ) ) {
3975	return false;
3976	}
3977
3978	$config = $wp_filesystem->get_contents( $wp_config );
3979
3980	if ( $enable ) {
3981	// Own the constant. A previous caching plugin (e.g. WP Rocket sets
3982	// it false on deactivate) can leave `define( 'WP_CACHE', false );`
3983	// behind — presence alone is not enough, the VALUE must be true or
3984	// WordPress never loads advanced-cache.php and our drop-in is dead.
3985	if ( preg_match( "/define\\(\\s['\"]WP_CACHE['\"]\\s,/", $config ) ) {
3986	$rewritten = preg_replace(
3987	"/define\$\\s['\"]WP_CACHE['\"]\\s,\\s[^)]\$\\s*;/",
3988	"define( 'WP_CACHE', true );",
3989	$config,
3990	1
3991	);
3992	// If an existing define was already `true`, the rewrite is a
3993	// no-op string-wise; either way we end on WP_CACHE === true.
3994	if ( null !== $rewritten ) {
3995	$config = $rewritten;
3996	}
3997	} else {
3998	$config = preg_replace( '/(<\?php)/', "$1\ndefine( 'WP_CACHE', true );", $config, 1 );
3999	}
4000	} else {
4001	// Shared with uninstall.php so the two removal paths can't drift
4002	// — they already had, which is why every non-lowercase spelling
4003	// of the value survived a disable. (#9)
4004	require_once XSPEED_DIR . 'includes/wp-cache-constant.php';
4005	$config = xspeed_strip_wp_cache_define( $config );
4006	}
4007
4008	return (bool) $wp_filesystem->put_contents( $wp_config, $config, FS_CHMOD_FILE );
4009	}
4010
4011	/**
4012	* Admin-bar purge menu — a parent node plus one child per visible cache
4013	* type (LiteSpeed-style), instead of a single "Purge All" link. Each
4014	* child posts to the same admin-post handler with its type slug. The
4015	* per-type items only appear for active/licensed modules; "Purge All"
4016	* always shows and always sweeps everything. (FBS-83114)
4017	*
4018	* The parent node links to the settings page rather than a purge URL —
4019	* clicking the top-level item used to wipe the whole cache instantly with
4020	* no confirmation, which is far too destructive for a stray click. Purging
4021	* stays available (and explicit) through the child items. (FBS-84068)
4022	*/
4023	public function admin_bar_purge( $wp_admin_bar ) {
4024	if ( ! current_user_can( 'manage_options' ) ) {
4025	return;
4026	}
4027
4028	$wp_admin_bar->add_node(
4029	array(
4030	'id' => 'xspeed-purge',
4031	'title' => __( 'xSpeed Cache', 'xspeed' ),
4032	'href' => admin_url( 'admin.php?page=' . Admin::PAGE_SLUG ),
4033	)
4034	);
4035
4036	foreach ( self::purge_types() as $slug => $type ) {
4037	if ( empty( $type['visible'] ) ) {
4038	continue;
4039	}
4040	$wp_admin_bar->add_node(
4041	array(
4042	'id' => 'xspeed-purge-' . $slug,
4043	'parent' => 'xspeed-purge',
4044	'title' => esc_html( $type['label'] ),
4045	'href' => self::purge_type_url( $slug ),
4046	)
4047	);
4048	}
4049	}
4050
4051	/**
4052	* Nonce-protected admin-post URL for purging a single type. The nonce
4053	* action is per-type so a leaked URL can't be replayed for a different
4054	* scope.
4055	*/
4056	private static function purge_type_url( string $type ): string {
4057	return wp_nonce_url(
4058	admin_url( 'admin-post.php?action=xspeed_purge&type=' . rawurlencode( $type ) ),
4059	'xspeed_purge_' . $type
4060	);
4061	}
4062
4063	public function handle_admin_bar_purge() {
4064	if ( ! current_user_can( 'manage_options' ) ) {
4065	wp_die( esc_html__( 'Unauthorized.', 'xspeed' ), 403 );
4066	}
4067	$type = isset( $_GET['type'] ) ? sanitize_key( wp_unslash( $_GET['type'] ) ) : 'all';
4068	check_admin_referer( 'xspeed_purge_' . $type );
4069
4070	// Only honour known types; anything else falls back to a full purge.
4071	if ( ! array_key_exists( $type, self::purge_types() ) ) {
4072	$type = 'all';
4073	}
4074	self::purge_type( $type );
4075
4076	wp_safe_redirect( self::safe_purge_redirect( wp_get_referer() ) );
4077	exit;
4078	}
4079
4080	/**
4081	* Resolve a safe redirect target for an admin-bar purge.
4082	*
4083	* The purge sends the admin back where they came from — but the referer
4084	* can be a ONE-SHOT action URL (e.g. update.php?action=upload-plugin from
4085	* installing a plugin zip, or any *.php?action=… that consumed a POST /
4086	* temp upload). Redirecting there re-runs the action with nothing to act
4087	* on, so WordPress dies — the classic "Please select a file" from
4088	* File_Upload_Upgrader. Strip the transient action args so we return to a
4089	* safe, re-GET-able view of the same page; fall back to the dashboard when
4090	* there is no usable referer.
4091	*
4092	* @param string\|false $referer Raw wp_get_referer() value.
4093	* @return string Safe URL to redirect to.
4094	*/
4095	public static function safe_purge_redirect( $referer ): string {
4096	$referer = is_string( $referer ) ? $referer : '';
4097	if ( '' === $referer ) {
4098	return admin_url();
4099	}
4100
4101	// A referer that lands on an action-processing endpoint (update.php,
4102	// update-core.php, plugin/theme install/upload flows) can't be safely
4103	// re-requested — send them to the dashboard instead of replaying it.
4104	$path = (string) wp_parse_url( $referer, PHP_URL_PATH );
4105	if ( preg_match( '#/wp-admin/(update\|update-core)\.php$#', $path ) ) {
4106	return admin_url();
4107	}
4108
4109	// Otherwise keep them on the same page but drop the query args that
4110	// would re-trigger a form action or upload on load.
4111	return remove_query_arg(
4112	array( 'action', 'action2', 'package', 'overwrite', 'plugin', 'theme', 'file', '_wpnonce', '_ajax_nonce' ),
4113	$referer
4114	);
4115	}
4116	}
4117