auditmysite 0.26.0

Resource-efficient WCAG 2.1 Accessibility Checker in Rust
Documentation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
//! Core Web Vitals extraction via CDP
//!
//! Collects LCP, FCP, CLS, TBT, TTFB and other performance metrics.

use chromiumoxide::cdp::browser_protocol::performance::GetMetricsParams;
use chromiumoxide::Page;
use serde::{Deserialize, Serialize};
use tracing::{debug, info, warn};

use crate::error::{AuditError, Result};

/// Source element attribution for a single CLS layout-shift entry.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ClsSource {
    /// Simplified node description, e.g. "DIV#banner" or "IMG"
    pub node: String,
    /// Bounding rect before the shift (may be absent on first paint)
    #[serde(skip_serializing_if = "Option::is_none")]
    pub previous_rect: Option<ShiftRect>,
    /// Bounding rect after the shift
    #[serde(skip_serializing_if = "Option::is_none")]
    pub current_rect: Option<ShiftRect>,
}

/// Axis-aligned bounding rect (viewport-relative pixels).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShiftRect {
    pub top: f64,
    pub left: f64,
    pub bottom: f64,
    pub right: f64,
}

/// A single layout-shift entry with per-element attribution.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ClsShift {
    /// Score contribution of this individual shift
    pub value: f64,
    /// When the shift occurred (ms from navigation start)
    pub start_time_ms: f64,
    /// Elements that moved (may be empty when browser does not expose attribution)
    pub sources: Vec<ClsSource>,
}

/// Core Web Vitals and performance metrics
#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct WebVitals {
    /// Largest Contentful Paint (ms) - target ≤2500
    pub lcp: Option<VitalMetric>,
    /// First Contentful Paint (ms) - target ≤1800
    pub fcp: Option<VitalMetric>,
    /// Cumulative Layout Shift - target ≤0.1
    pub cls: Option<VitalMetric>,
    /// Per-shift CLS attribution (#135)
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub cls_attribution: Vec<ClsShift>,
    /// Time to First Byte (ms)
    pub ttfb: Option<VitalMetric>,
    /// First Input Delay (ms) - deprecated; always null in CDP/headless audits
    #[serde(skip_serializing_if = "Option::is_none")]
    pub fid: Option<VitalMetric>,
    /// Total Blocking Time (ms)
    pub tbt: Option<VitalMetric>,
    /// Speed Index — heuristic proxy: 0.35·FCP + 0.65·LCP (#137)
    pub speed_index: Option<VitalMetric>,
    /// Time to Interactive — simplified: max(domInteractive, last long-task end) (#137)
    pub tti: Option<VitalMetric>,
    /// Interaction to Next Paint — only populated when interaction events fire during audit
    #[serde(skip_serializing_if = "Option::is_none")]
    pub inp: Option<VitalMetric>,
    /// DOM Content Loaded (ms)
    pub dom_content_loaded: Option<f64>,
    /// Page Load Time (ms)
    pub load_time: Option<f64>,
    /// DOM Nodes count
    pub dom_nodes: Option<i64>,
    /// JavaScript Heap Size (bytes)
    pub js_heap_size: Option<i64>,
}

/// Individual vital metric with value and rating
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VitalMetric {
    /// The metric value
    pub value: f64,
    /// Rating: "good", "needs-improvement", "poor"
    pub rating: String,
    /// Target threshold for "good"
    pub target: f64,
}

impl VitalMetric {
    pub fn new(value: f64, good_threshold: f64, poor_threshold: f64) -> Self {
        let rating = if value <= good_threshold {
            "good"
        } else if value <= poor_threshold {
            "needs-improvement"
        } else {
            "poor"
        };

        Self {
            value,
            rating: rating.to_string(),
            target: good_threshold,
        }
    }

    pub fn is_good(&self) -> bool {
        self.rating == "good"
    }
}

impl WebVitals {
    /// Count how many vitals pass the "good" threshold
    pub fn good_count(&self) -> usize {
        [&self.lcp, &self.fcp, &self.cls, &self.tbt]
            .iter()
            .filter(|v| v.as_ref().map(|m| m.is_good()).unwrap_or(false))
            .count()
    }

    /// Count how many vitals are available
    pub fn available_count(&self) -> usize {
        [&self.lcp, &self.fcp, &self.cls, &self.tbt]
            .iter()
            .filter(|v| v.is_some())
            .count()
    }
}

/// Inject PerformanceObserver script before navigation so LCP, TBT, and CLS
/// entries are captured from the very first paint (Lighthouse-style).
///
/// Must be called on a fresh `Page` BEFORE `browser.navigate()`. The observers
/// store results in `window.__ams_lcp`, `window.__ams_tbt`, `window.__ams_cls`.
pub async fn prepare_vitals_collection(page: &Page) -> Result<()> {
    let script = r#"
(function() {
    // LCP observer — captures the largest contentful paint before load
    window.__ams_lcp = 0;
    try {
        var _lcpObs = new PerformanceObserver(function(list) {
            var entries = list.getEntries();
            if (entries.length > 0) {
                window.__ams_lcp = entries[entries.length - 1].startTime;
            }
        });
        _lcpObs.observe({ type: 'largest-contentful-paint', buffered: true });
        window.__ams_lcp_obs = _lcpObs;
    } catch(e) {}

    // TBT + TTI via Long Tasks — sum blocking time; track last task end for TTI
    window.__ams_tbt = 0;
    window.__ams_last_task_end = 0;
    try {
        new PerformanceObserver(function(list) {
            var entries = list.getEntries();
            for (var i = 0; i < entries.length; i++) {
                var e = entries[i];
                if (e.duration > 50) {
                    window.__ams_tbt += e.duration - 50;
                }
                var end = e.startTime + e.duration;
                if (end > window.__ams_last_task_end) {
                    window.__ams_last_task_end = end;
                }
            }
        }).observe({ type: 'longtask', buffered: true });
    } catch(e) {}

    // CLS — accumulate total and capture per-shift attribution (#135)
    window.__ams_cls = 0;
    window.__ams_cls_shifts = [];
    try {
        new PerformanceObserver(function(list) {
            var entries = list.getEntries();
            for (var i = 0; i < entries.length; i++) {
                var e = entries[i];
                if (!e.hadRecentInput) {
                    window.__ams_cls += e.value;
                    var sources = [];
                    try {
                        if (e.sources) {
                            for (var j = 0; j < e.sources.length; j++) {
                                var s = e.sources[j];
                                var nodeDesc = 'unknown';
                                try {
                                    if (s.node) {
                                        nodeDesc = s.node.nodeName;
                                        if (s.node.id) nodeDesc += '#' + s.node.id;
                                        else if (s.node.className && typeof s.node.className === 'string') {
                                            var cls = s.node.className.trim().split(/\s+/)[0];
                                            if (cls) nodeDesc += '.' + cls;
                                        }
                                    }
                                } catch(_) {}
                                sources.push({
                                    node: nodeDesc,
                                    previousRect: s.previousRect ? {top: s.previousRect.top, left: s.previousRect.left, bottom: s.previousRect.bottom, right: s.previousRect.right} : null,
                                    currentRect: s.currentRect ? {top: s.currentRect.top, left: s.currentRect.left, bottom: s.currentRect.bottom, right: s.currentRect.right} : null
                                });
                            }
                        }
                    } catch(_) {}
                    window.__ams_cls_shifts.push({value: e.value, startTime: e.startTime, sources: sources});
                }
            }
        }).observe({ type: 'layout-shift', buffered: true });
    } catch(e) {}

    // INP via event-timing (#134) — captures real interaction durations
    window.__ams_inp = 0;
    try {
        new PerformanceObserver(function(list) {
            var entries = list.getEntries();
            for (var i = 0; i < entries.length; i++) {
                var e = entries[i];
                if (e.duration > window.__ams_inp) {
                    window.__ams_inp = e.duration;
                }
            }
        }).observe({ type: 'event', durationThreshold: 16, buffered: true });
    } catch(e) {}
    // Also observe first-input for environments that don't support event-timing
    try {
        new PerformanceObserver(function(list) {
            var entries = list.getEntries();
            for (var i = 0; i < entries.length; i++) {
                var e = entries[i];
                var delay = e.processingStart - e.startTime;
                if (delay > window.__ams_inp) window.__ams_inp = delay;
            }
        }).observe({ type: 'first-input', buffered: true });
    } catch(e) {}
})();
"#;

    page.evaluate_on_new_document(script)
        .await
        .map_err(|e| AuditError::CdpError(format!("Failed to inject vitals observer: {}", e)))?;

    Ok(())
}

/// Read the pre-injected globals after navigation to collect LCP, TBT, CLS, TTI, INP.
///
/// Flushes and disconnects the LCP observer to capture any buffered entries.
async fn collect_preinjected_vitals(page: &Page) -> Result<PreinjectedVitals> {
    let js = r#"
(function() {
    // Finalize LCP — flush and disconnect observer
    var lcp = 0;
    try {
        if (window.__ams_lcp_obs) {
            var recs = window.__ams_lcp_obs.takeRecords();
            if (recs.length > 0) {
                window.__ams_lcp = recs[recs.length - 1].startTime;
            }
            window.__ams_lcp_obs.disconnect();
        }
        lcp = window.__ams_lcp || 0;
    } catch(e) {}

    return JSON.stringify({
        lcp: lcp,
        tbt: window.__ams_tbt || 0,
        cls: window.__ams_cls || 0,
        lastTaskEnd: window.__ams_last_task_end || 0,
        clsShifts: window.__ams_cls_shifts || [],
        inpDuration: window.__ams_inp || 0
    });
})()
"#;

    let result = page
        .evaluate(js)
        .await
        .map_err(|e| AuditError::CdpError(format!("Preinjected vitals read failed: {}", e)))?;

    let json_str = result.value().and_then(|v| v.as_str()).unwrap_or("{}");
    let parsed: serde_json::Value = serde_json::from_str(json_str).unwrap_or_default();

    let cls_shifts = parse_cls_shifts(&parsed["clsShifts"]);

    Ok(PreinjectedVitals {
        lcp: parsed["lcp"].as_f64().unwrap_or(0.0),
        tbt: parsed["tbt"].as_f64().unwrap_or(0.0),
        cls: parsed["cls"].as_f64().unwrap_or(0.0),
        last_task_end: parsed["lastTaskEnd"].as_f64().unwrap_or(0.0),
        cls_shifts,
        inp_duration: parsed["inpDuration"].as_f64().unwrap_or(0.0),
    })
}

/// Parse CLS shift entries from the JSON value returned by the browser.
fn parse_cls_shifts(val: &serde_json::Value) -> Vec<ClsShift> {
    val.as_array()
        .map(|arr| {
            arr.iter()
                .filter_map(|entry| {
                    let value = entry["value"].as_f64()?;
                    let start_time_ms = entry["startTime"].as_f64().unwrap_or(0.0);
                    let sources = entry["sources"]
                        .as_array()
                        .map(|srcs| {
                            srcs.iter()
                                .map(|s| {
                                    let node = s["node"].as_str().unwrap_or("unknown").to_string();
                                    let previous_rect = parse_shift_rect(&s["previousRect"]);
                                    let current_rect = parse_shift_rect(&s["currentRect"]);
                                    ClsSource {
                                        node,
                                        previous_rect,
                                        current_rect,
                                    }
                                })
                                .collect()
                        })
                        .unwrap_or_default();
                    Some(ClsShift {
                        value,
                        start_time_ms,
                        sources,
                    })
                })
                .collect()
        })
        .unwrap_or_default()
}

fn parse_shift_rect(val: &serde_json::Value) -> Option<ShiftRect> {
    if val.is_null() {
        return None;
    }
    Some(ShiftRect {
        top: val["top"].as_f64().unwrap_or(0.0),
        left: val["left"].as_f64().unwrap_or(0.0),
        bottom: val["bottom"].as_f64().unwrap_or(0.0),
        right: val["right"].as_f64().unwrap_or(0.0),
    })
}

/// Values collected by the pre-injected PerformanceObserver script.
struct PreinjectedVitals {
    lcp: f64,
    tbt: f64,
    cls: f64,
    /// End time of the last long task (ms from navigation start); 0 = no long tasks
    last_task_end: f64,
    /// Per-shift CLS entries (#135)
    cls_shifts: Vec<ClsShift>,
    /// Max event/interaction duration captured by event-timing or first-input (#134)
    inp_duration: f64,
}

/// Read the current LCP value from the pre-injected global.
///
/// Returns `None` if no LCP was captured yet or the script was not injected.
pub async fn finalize_lcp(page: &Page) -> Result<Option<f64>> {
    let result = page
        .evaluate("window.__ams_lcp || 0")
        .await
        .map_err(|e| AuditError::CdpError(format!("LCP read failed: {}", e)))?;

    let val = result.value().and_then(|v| v.as_f64()).unwrap_or(0.0);
    Ok(if val > 0.0 { Some(val) } else { None })
}

/// Wait for LCP and TBT to stabilize before reading vitals.
///
/// **Phase 1 – LCP**: polls `window.__ams_lcp` every 250 ms (initial 300 ms wait,
/// up to ~3 s) until an LCP entry is captured.
///
/// **Phase 2 – TBT settle**: JS bundles execute *after* LCP fires, so Long Tasks
/// are not yet visible when LCP > 0. Polls `window.__ams_tbt` every 200 ms and
/// breaks only when the value is stable for three consecutive reads (≥ 600 ms
/// unchanged). Max 5 s — matches Lighthouse's quiet-window heuristic.
async fn wait_for_vitals_stable(page: &Page) {
    // Phase 1: wait for first LCP entry
    tokio::time::sleep(std::time::Duration::from_millis(300)).await;
    for _ in 0..11u8 {
        let lcp = page
            .evaluate("window.__ams_lcp || 0")
            .await
            .ok()
            .and_then(|r| r.value().and_then(|v| v.as_f64()))
            .unwrap_or(0.0);
        if lcp > 0.0 {
            break;
        }
        tokio::time::sleep(std::time::Duration::from_millis(250)).await;
    }

    // Phase 2: wait for TBT to stop growing (Long Tasks settle after LCP)
    let mut last_tbt = -1.0_f64;
    let mut stable_ticks: u8 = 0;
    for _ in 0..25u8 {
        // max 5 s (25 × 200 ms)
        tokio::time::sleep(std::time::Duration::from_millis(200)).await;
        let tbt = page
            .evaluate("window.__ams_tbt || 0")
            .await
            .ok()
            .and_then(|r| r.value().and_then(|v| v.as_f64()))
            .unwrap_or(0.0);
        if (tbt - last_tbt).abs() < 1.0 {
            stable_ticks += 1;
            if stable_ticks >= 3 {
                debug!(
                    "TBT stable at {:.0}ms after {} settle ticks",
                    tbt, stable_ticks
                );
                break;
            }
        } else {
            stable_ticks = 0;
        }
        last_tbt = tbt;
    }
}

/// Extract Core Web Vitals from a page
///
/// # Arguments
/// * `page` - The chromiumoxide Page to extract metrics from
///
/// # Returns
/// * `Ok(WebVitals)` - The extracted performance metrics
/// * `Err(AuditError)` - If extraction fails
pub async fn extract_web_vitals(page: &Page) -> Result<WebVitals> {
    info!("Extracting Core Web Vitals...");

    wait_for_vitals_stable(page).await;

    let mut vitals = WebVitals::default();

    // Read pre-injected observer globals first (Lighthouse-style, captures from first paint).
    // Falls back gracefully when prepare_vitals_collection was not called.
    let preinjected = collect_preinjected_vitals(page).await.unwrap_or_else(|e| {
        warn!(
            "Pre-injected vitals unavailable ({}), falling back to CDP",
            e
        );
        PreinjectedVitals {
            lcp: 0.0,
            tbt: 0.0,
            cls: 0.0,
            last_task_end: 0.0,
            cls_shifts: vec![],
            inp_duration: 0.0,
        }
    });
    let last_task_end = preinjected.last_task_end;

    // Apply pre-injected LCP and TBT when non-zero (0 = not captured / not injected)
    if preinjected.lcp > 0.0 && preinjected.lcp < 300_000.0 {
        vitals.lcp = Some(VitalMetric::new(preinjected.lcp, 2500.0, 4000.0));
        debug!("LCP (preinjected): {:.0}ms", preinjected.lcp);
    }
    // TBT: 0 ms is a valid perfect score (no long tasks), always include like CLS.
    vitals.tbt = Some(VitalMetric::new(preinjected.tbt, 200.0, 600.0));
    debug!("TBT (preinjected): {:.0}ms", preinjected.tbt);
    // CLS: 0.0 is a valid perfect score, always apply
    vitals.cls = Some(VitalMetric::new(preinjected.cls, 0.1, 0.25));
    debug!("CLS (preinjected): {:.4}", preinjected.cls);

    // CLS attribution (#135)
    vitals.cls_attribution = preinjected.cls_shifts;

    // INP (#134): event-timing or first-input duration; 0 = no interaction captured.
    // In headless audits interactions rarely fire, so 0 means "not measurable" and
    // we leave the field empty rather than reporting a misleading 0ms.
    if preinjected.inp_duration > 0.0 {
        vitals.inp = Some(VitalMetric::new(preinjected.inp_duration, 200.0, 500.0));
        debug!("INP (event-timing): {:.0}ms", preinjected.inp_duration);
    }

    // Get performance metrics via CDP for FCP, DCL, heap, node count
    let metrics_response = page
        .execute(GetMetricsParams::default())
        .await
        .map_err(|e| AuditError::CdpError(format!("Failed to get metrics: {}", e)))?;

    for metric in &metrics_response.metrics {
        let value = metric.value;
        match metric.name.as_str() {
            "FirstContentfulPaint" => {
                let ms = value * 1000.0;
                if ms > 0.0 && ms < 300_000.0 {
                    vitals.fcp = Some(VitalMetric::new(ms, 1800.0, 3000.0));
                    debug!("FCP (CDP): {:.0}ms", ms);
                }
            }
            "LargestContentfulPaint" if vitals.lcp.is_none() => {
                // Only use CDP LCP as fallback when pre-injected observer missed it
                let ms = value * 1000.0;
                if ms > 0.0 && ms < 300_000.0 {
                    vitals.lcp = Some(VitalMetric::new(ms, 2500.0, 4000.0));
                    debug!("LCP (CDP fallback): {:.0}ms", ms);
                }
            }
            "DomContentLoaded" => {
                let ms = value * 1000.0;
                if ms > 0.0 && ms < 300_000.0 {
                    vitals.dom_content_loaded = Some(ms);
                }
            }
            "JSHeapUsedSize" => {
                vitals.js_heap_size = Some(value as i64);
            }
            "Nodes" => {
                vitals.dom_nodes = Some(value as i64);
            }
            _ => {}
        }
    }

    // Extract additional metrics via JavaScript (FCP fallback, TTFB, load time)
    let js_metrics = extract_js_metrics(page).await?;

    if vitals.fcp.is_none() && js_metrics.fcp.is_some() {
        vitals.fcp = js_metrics.fcp;
    }
    if vitals.lcp.is_none() && js_metrics.lcp.is_some() {
        vitals.lcp = js_metrics.lcp;
    }
    if js_metrics.ttfb.is_some() {
        vitals.ttfb = js_metrics.ttfb;
    }
    if js_metrics.load_time.is_some() {
        vitals.load_time = js_metrics.load_time;
    }
    if vitals.dom_content_loaded.is_none() {
        if let Some(js_dcl) = js_metrics.dom_content_loaded {
            if js_dcl > 0.0 && js_dcl < 300_000.0 {
                vitals.dom_content_loaded = Some(js_dcl);
            }
        }
    }

    // TTI (#137): max(domInteractive, last_long_task_end).
    // domInteractive = domContentLoadedEventStart (navigation timing).
    // Thresholds from Lighthouse: good ≤3800ms, poor >7300ms.
    let dom_interactive_ms: f64 = page
        .evaluate("(function(){ var n = performance.getEntriesByType('navigation')[0]; return n ? n.domInteractive : 0; })()")
        .await
        .ok()
        .and_then(|r| r.value().and_then(|v| v.as_f64()))
        .unwrap_or(0.0);
    let tti_ms = dom_interactive_ms.max(last_task_end);
    if tti_ms > 0.0 && tti_ms < 300_000.0 {
        vitals.tti = Some(VitalMetric::new(tti_ms, 3800.0, 7300.0));
        debug!("TTI (approx): {:.0}ms", tti_ms);
    }

    // Speed Index (#137): heuristic proxy = 0.35·FCP + 0.65·LCP.
    // Real Speed Index requires video-frame analysis; this approximation
    // correlates well for typical content-heavy pages.
    // Thresholds from Lighthouse: good ≤3400ms, poor >5800ms.
    if let (Some(fcp), Some(lcp)) = (&vitals.fcp, &vitals.lcp) {
        let si = 0.35 * fcp.value + 0.65 * lcp.value;
        vitals.speed_index = Some(VitalMetric::new(si, 3400.0, 5800.0));
        debug!("Speed Index (heuristic): {:.0}ms", si);
    }

    info!(
        "Web Vitals extracted: LCP={:?}ms, FCP={:?}ms, CLS={:?}, TTI={:?}ms, INP={:?}ms",
        vitals.lcp.as_ref().map(|v| v.value as i64),
        vitals.fcp.as_ref().map(|v| v.value as i64),
        vitals.cls.as_ref().map(|v| v.value),
        vitals.tti.as_ref().map(|v| v.value as i64),
        vitals.inp.as_ref().map(|v| v.value as i64),
    );

    Ok(vitals)
}

/// Extract metrics via JavaScript Performance API
async fn extract_js_metrics(page: &Page) -> Result<WebVitals> {
    let js_code = r#"
    (() => {
        const result = {};

        // Navigation Timing
        const nav = performance.getEntriesByType('navigation')[0];
        if (nav) {
            result.ttfb = nav.responseStart - nav.requestStart;
            result.loadTime = nav.loadEventEnd - nav.startTime;
            result.domContentLoaded = nav.domContentLoadedEventEnd - nav.startTime;
        }

        // Paint Timing
        const paints = performance.getEntriesByType('paint');
        for (const paint of paints) {
            if (paint.name === 'first-contentful-paint') {
                result.fcp = paint.startTime;
            }
        }

        // LCP (if available)
        const lcpEntries = performance.getEntriesByType('largest-contentful-paint');
        if (lcpEntries.length > 0) {
            result.lcp = lcpEntries[lcpEntries.length - 1].startTime;
        }

        return JSON.stringify(result);
    })()
    "#;

    let js_result = page
        .evaluate(js_code)
        .await
        .map_err(|e| AuditError::CdpError(format!("JS metrics extraction failed: {}", e)))?;

    let json_str = js_result.value().and_then(|v| v.as_str()).unwrap_or("{}");

    let parsed: serde_json::Value = serde_json::from_str(json_str).unwrap_or_default();

    let mut vitals = WebVitals::default();

    if let Some(lcp) = parsed["lcp"].as_f64() {
        vitals.lcp = Some(VitalMetric::new(lcp, 2500.0, 4000.0));
    }
    if let Some(fcp) = parsed["fcp"].as_f64() {
        vitals.fcp = Some(VitalMetric::new(fcp, 1800.0, 3000.0));
    }
    if let Some(ttfb) = parsed["ttfb"].as_f64() {
        vitals.ttfb = Some(VitalMetric::new(ttfb, 800.0, 1800.0));
    }
    if let Some(load_time) = parsed["loadTime"].as_f64() {
        vitals.load_time = Some(load_time);
    }
    if let Some(dcl) = parsed["domContentLoaded"].as_f64() {
        vitals.dom_content_loaded = Some(dcl);
    }

    Ok(vitals)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_vital_metric_good() {
        let metric = VitalMetric::new(1500.0, 2500.0, 4000.0);
        assert!(metric.is_good());
        assert_eq!(metric.rating, "good");
    }

    #[test]
    fn test_vital_metric_needs_improvement() {
        let metric = VitalMetric::new(3000.0, 2500.0, 4000.0);
        assert!(!metric.is_good());
        assert_eq!(metric.rating, "needs-improvement");
    }

    #[test]
    fn test_vital_metric_poor() {
        let metric = VitalMetric::new(5000.0, 2500.0, 4000.0);
        assert!(!metric.is_good());
        assert_eq!(metric.rating, "poor");
    }

    #[test]
    fn test_web_vitals_good_count() {
        let vitals = WebVitals {
            lcp: Some(VitalMetric::new(2000.0, 2500.0, 4000.0)),
            fcp: Some(VitalMetric::new(1500.0, 1800.0, 3000.0)),
            cls: Some(VitalMetric::new(0.05, 0.1, 0.25)),
            ..Default::default()
        };

        assert_eq!(vitals.good_count(), 3);
        assert_eq!(vitals.available_count(), 3);
    }
}