xspeed / includes / class-optimize-verifier.php

class-optimize-verifier.php in xSpeed Cache: AI-Powered Performance Hub with MCP, Caching & CDN 1.3.0, at includes/class-optimize-verifier.php

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1	<?php
2	/**
3	* Optimize verifier — did that change break the page?
4	*
5	* @package XSpeed
6	*/
7
8	namespace XSpeed;
9
10	defined( 'ABSPATH' ) \|\| exit;
11
12	/**
13	* Capture what a page looks like, then decide whether a later fetch of it is
14	* still healthy.
15	*
16	* The autopilot's whole claim to being safe rests here. Applying settings is
17	* easy; knowing you have not just served a blank page to every visitor is the
18	* hard part, and it is the part a human doing this by hand actually performs —
19	* they look at the site.
20	*
21	* ## What this can and cannot see
22	*
23	* This runs in PHP, over the HTML a request returns. It catches the failures
24	* that show up in markup: a fatal, a truncated document, a stylesheet that
25	* vanished, a page that collapsed to a fraction of its size.
26	*
27	* It does NOT execute JavaScript, so it cannot see a page that arrives intact
28	* and then breaks in the browser. That failure is real and has happened here:
29	* removing jQuery Migrate produced `jQuery.Deferred exception: e.indexOf is not
30	* a function` on a page whose HTML was complete and the right size. Every
31	* assertion below would have passed it.
32	*
33	* That is why `Optimize_Plan` puts anything with an invisible failure mode in
34	* the AGGRESSIVE tier rather than trusting this class to catch it. The check
35	* and the classification are two halves of one safety story; neither is
36	* sufficient alone. A JS-executing check belongs in the E2E layer, which has a
37	* real browser — see #210.
38	*
39	* Comparison is always against a baseline captured BEFORE the run, never
40	* against absolute thresholds: "this page has 3 stylesheets" is meaningless,
41	* "this page had 54 stylesheets and now has 0" is a broken site.
42	*
43	* @since 1.2.0
44	*/
45	final class Optimize_Verifier {
46
47	/**
48	* How far the HTML may shrink or grow before it is treated as broken.
49	*
50	* Wide on purpose. Minification legitimately removes a chunk of a page,
51	* and combining rewrites a headful of tags — neither is damage. What this
52	* catches is the catastrophic case: a fatal that truncates the document, or
53	* a blank page, both of which collapse the size far past any optimization.
54	*/
55	private const SIZE_TOLERANCE = 0.5;
56
57	/**
58	* Fetch a page and reduce it to the handful of facts worth comparing.
59	*
60	* Requested ANONYMOUSLY and uncached. A logged-in request hits the
61	* drop-in's bailout and never sees the cached path, so it would verify a
62	* page no visitor is served; a cached response would verify the page as it
63	* was BEFORE the change, which is worse than not checking at all.
64	*
65	* @param string $url Absolute URL to sample.
66	* @return array<string,mixed>\|\WP_Error
67	*/
68	public static function sample( string $url ) {
69	$url = esc_url_raw( $url );
70	if ( '' === $url ) {
71	return new \WP_Error( 'xspeed_verify_url', __( 'A URL is required.', 'xspeed' ) );
72	}
73
74	// Cache-buster: without it a static-cached HIT returns the pre-change
75	// page and every check passes against stale HTML.
76	$bust = add_query_arg( 'xspeed_verify', (string) time(), $url );
77
78	$t0 = microtime( true );
79	$resp = wp_remote_get(
80	$bust,
81	array(
82	'timeout' => 20,
83	'redirection' => 3,
84	'sslverify' => false,
85	'headers' => array( 'Cache-Control' => 'no-cache' ),
86	// A real browser UA: some hosts and firewalls serve a
87	// challenge page to unknown agents, which would read as the
88	// site being broken.
89	'user-agent' => 'Mozilla/5.0 (compatible; xSpeed-Verifier/1.0)',
90	)
91	);
92
93	if ( is_wp_error( $resp ) ) {
94	return $resp;
95	}
96
97	$body = (string) wp_remote_retrieve_body( $resp );
98
99	return array(
100	'status' => (int) wp_remote_retrieve_response_code( $resp ),
101	'bytes' => strlen( $body ),
102	'complete' => (bool) preg_match( '#</body\s*>#i', $body ),
103	'stylesheets' => self::count_stylesheets( $body ),
104	'scripts' => (int) preg_match_all( '#<script\b[^>]*\bsrc=#i', $body ),
105	'title' => self::extract_title( $body ),
106	// Wall-clock for the whole request, in ms. The cache-buster above
107	// makes every sample an uncached render, so successive samples
108	// measure the same thing and their medians are comparable — this
109	// is what Optimizer's per-step regression check reads. (#310)
110	'elapsed_ms' => ( microtime( true ) - $t0 ) * 1000,
111	);
112	}
113
114	/**
115	* Count real stylesheet links.
116	*
117	* `<noscript>` blocks are stripped first. The async-CSS pattern emits a
118	* no-JS fallback `<link>` beside every deferred one, so counting naively
119	* doubles the total and makes a healthy page look like it grew — a
120	* mistake worth guarding against in code, having been made once in
121	* analysis.
122	*
123	* @param string $html Page HTML.
124	*/
125	private static function count_stylesheets( string $html ): int {
126	$stripped = (string) preg_replace( '#<noscript\b[^>]>.?</noscript\s*>#is', '', $html );
127	return (int) preg_match_all( '#<link\b[^>]*\brel=["\']?stylesheet#i', $stripped );
128	}
129
130	/**
131	* @param string $html Page HTML.
132	*/
133	private static function extract_title( string $html ): string {
134	if ( preg_match( '#<title\b[^>]>(.?)</title\s*>#is', $html, $m ) ) {
135	return trim( wp_strip_all_tags( $m[1] ) );
136	}
137	return '';
138	}
139
140	/**
141	* Compare a fresh sample against the baseline.
142	*
143	* Returns every failure rather than the first, so a report can say what
144	* actually went wrong instead of "verification failed".
145	*
146	* Pure — no I/O, unit-tested.
147	*
148	* @param array<string,mixed> $baseline Sample taken before the run.
149	* @param array<string,mixed> $current Sample taken after a change.
150	* @return array{ok:bool,failures:string[]}
151	*/
152	public static function compare( array $baseline, array $current ): array {
153	$failures = array();
154
155	if ( 200 !== (int) ( $current['status'] ?? 0 ) ) {
156	$failures[] = sprintf(
157	/* translators: %d: HTTP status code */
158	__( 'The page returned HTTP %d.', 'xspeed' ),
159	(int) ( $current['status'] ?? 0 )
160	);
161	// Nothing below is meaningful once the response itself failed.
162	return array(
163	'ok' => false,
164	'failures' => $failures,
165	);
166	}
167
168	if ( empty( $current['complete'] ) ) {
169	$failures[] = __( 'The page stopped part-way through — no closing </body>, which usually means a PHP fatal.', 'xspeed' );
170	}
171
172	$before = (int) ( $baseline['bytes'] ?? 0 );
173	$after = (int) ( $current['bytes'] ?? 0 );
174	if ( $before > 0 ) {
175	$ratio = $after / $before;
176	if ( $ratio < ( 1 - self::SIZE_TOLERANCE ) \|\| $ratio > ( 1 + self::SIZE_TOLERANCE ) ) {
177	$failures[] = sprintf(
178	/* translators: 1: before size in bytes, 2: after size in bytes */
179	__( 'The page size changed from %1$d to %2$d bytes — too far to be optimization.', 'xspeed' ),
180	$before,
181	$after
182	);
183	}
184	}
185
186	// Zero is the signal, not a decrease: combining legitimately takes 54
187	// stylesheets down to 3. Losing them ALL is a page with no styling.
188	if ( (int) ( $baseline['stylesheets'] ?? 0 ) > 0 && 0 === (int) ( $current['stylesheets'] ?? 0 ) ) {
189	$failures[] = __( 'Every stylesheet disappeared — the page would render unstyled.', 'xspeed' );
190	}
191	if ( (int) ( $baseline['scripts'] ?? 0 ) > 0 && 0 === (int) ( $current['scripts'] ?? 0 ) ) {
192	$failures[] = __( 'Every script disappeared.', 'xspeed' );
193	}
194
195	$before_title = (string) ( $baseline['title'] ?? '' );
196	if ( '' !== $before_title && $before_title !== (string) ( $current['title'] ?? '' ) ) {
197	$failures[] = __( 'The page title changed — this may be an error page rather than the site.', 'xspeed' );
198	}
199
200	return array(
201	'ok' => array() === $failures,
202	'failures' => $failures,
203	);
204	}
205	}
206