/*
 * Candidate-side proctoring pipeline.
 * MediaPipe runs locally for ML face/gaze/object detection.
 * Enforces Tab/Focus Loss, Clipboard Activity, AI-Tool/Hotkey Detection,
 * Continuous Speech Analysis, Screen Share Enforcement & System Desktop Screenshots.
 * All events (MediaPipe ML + Focus/AI/Speech) are transmitted to the server endpoint.
 */

import { initMeteredIceServers } from './metered.js';

// MediaPipe Published Browser Bundle CDN URLs
const VISION_MODULE_URL = 'https://cdn.jsdelivr.net/npm/@mediapipe/tasks-vision@0.10.22-rc.20250304/vision_bundle.mjs';
const VISION_MODULE_FALLBACK_URL = 'https://unpkg.com/@mediapipe/tasks-vision@0.10.22-rc.20250304/vision_bundle.mjs';
const WASM_ROOT = 'https://cdn.jsdelivr.net/npm/@mediapipe/tasks-vision@0.10.22-rc.20250304/wasm';
const FACE_MODEL_URL = 'https://storage.googleapis.com/mediapipe-models/face_landmarker/face_landmarker/float16/1/face_landmarker.task';
const OBJECT_MODEL_URL = 'https://storage.googleapis.com/mediapipe-models/object_detector/efficientdet_lite0/float32/1/efficientdet_lite0.tflite';

const SAMPLE_INTERVAL_MS = 200;
const NO_FACE_GRACE_MS = 1000;
const LOOKING_AWAY_GRACE_MS = 700;
const PROLONGED_LOOKING_AWAY_MS = 10000;
const PROLONGED_LOOKING_AWAY_RECHECK_MS = 120000;
const PHONE_EVENT_COOLDOWN_MS = 3000;
const SNAPSHOT_QUALITY = 0.72;
const HEAD_YAW_THRESHOLD = 0.34;
const HEAD_PITCH_UP_THRESHOLD = 0.2;
const HEAD_PITCH_DOWN_THRESHOLD = 0.74;
const GAZE_HORIZONTAL_LEFT_THRESHOLD = 0.28;
const GAZE_HORIZONTAL_RIGHT_THRESHOLD = 0.72;
const GAZE_DOWN_THRESHOLD = 0.62;
const CORNER_FIXATION_MS = 18000;
const CORNER_RECHECK_MS = 20000;
const CORNER_JITTER_GRACE_MS = 3000;

// --- State Variables for Violation & Focus Detection ---
let isTabSwitchScreenshotEnabled = true;
let lastTabSwitchTime = 0;
let pendingNativePrompts = 0;
let suppressFocusViolationsUntil = 0;

let screenShareStream = null;
let screenShareVideoElem = null;
let overlayCheckInterval = null;
let candidateSpeechHistory = [];

// --- Native Prompt Suppression Window ---
export function beginNativePrompt() {
    pendingNativePrompts++;
}

export function endNativePrompt() {
    pendingNativePrompts = Math.max(0, pendingNativePrompts - 1);
}

export function armTrailingBuffer(ms) {
    suppressFocusViolationsUntil = Math.max(suppressFocusViolationsUntil, Date.now() + ms);
}

export function isFocusSuppressed() {
    return pendingNativePrompts > 0 || Date.now() < suppressFocusViolationsUntil;
}

export function isCandidateAssessmentPage() {
    if (typeof window === 'undefined' || typeof document === 'undefined') return false;
    const isCandidateUrl = window.location.pathname.includes('/candidate/');
    const hasMonaco = Boolean(document.getElementById('monaco-editor-container'));
    const isInterviewerPage = Boolean(document.getElementById('interviewer-cand-video') || document.getElementById('interviewer-self-video') || document.getElementById('panelist-mesh-grid'));

    return (isCandidateUrl || hasMonaco) && !isInterviewerPage;
}

export function isCandidateCallActive() {
    if (!isCandidateAssessmentPage()) return false;
    if (typeof window !== 'undefined' && typeof window.isCallConnected === 'function') {
        return window.isCallConnected();
    }
    const callStatusBadge = document.getElementById('call-status-badge');
    if (callStatusBadge) {
        return callStatusBadge.textContent.includes('LIVE') || callStatusBadge.textContent.includes('CONNECTED');
    }
    return false;
}

// --- Structured Logging & Backend Reporting ---
class StructuredEventLogger {
    constructor(sessionId) {
        this.sessionId = sessionId;
        this.events = [];
    }

    record(type, confidence, details, snapshot = null) {
        const event = {
            schema: 'candidate-proctoring/v1',
            session_id: this.sessionId,
            event_id: `${type}-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`,
            type,
            timestamp: new Date().toISOString(),
            confidence: Number(Math.max(0, Math.min(1, confidence || 0)).toFixed(4)),
            details: details || {},
            snapshot: snapshot || null,
        };
        this.events.push(event);
        console.log('[proctoring:event]', event);

        this.sendToServer(event);

        return event;
    }

    sendToServer(event) {
        if (!isCandidateAssessmentPage()) return;
        const interviewId = this.sessionId || document.body.dataset.interviewId;
        if (!interviewId) return;

        const csrfToken = document.querySelector('meta[name="csrf-token"]')?.content || window.csrfToken;

        fetch(`/candidate/log-violation/${interviewId}`, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
                'X-CSRF-TOKEN': csrfToken
            },
            body: JSON.stringify({
                type: event.type,
                details: typeof event.details === 'object' ? JSON.stringify(event.details) : event.details,
                confidence: event.confidence,
                snapshot: event.snapshot,
                session_id: event.session_id,
                event_id: event.event_id,
                timestamp: event.timestamp
            })
        })
        .then(r => r.json())
        .then(() => {
            if (typeof BroadcastChannel !== 'undefined') {
                const callSigChannel = new BroadcastChannel('webrtc_call_' + interviewId);
                const liveSyncChannel = new BroadcastChannel('live_sync_' + interviewId);
                callSigChannel.postMessage({ type: 'violation_occurred', violation_type: event.type, details: event.details });
                liveSyncChannel.postMessage({ type: 'violation_logged', violation_type: event.type, details: event.details });
            }
            if (typeof window.pollReviewData === 'function') {
                window.pollReviewData();
            }
        })
        .catch(err => console.log('[proctoring:sync-error]', err));
    }

    report(startedAt, endedAt, durations) {
        const report = {
            schema: 'candidate-proctoring/report-v1',
            session_id: this.sessionId,
            started_at: startedAt,
            ended_at: endedAt,
            generated_at: new Date().toISOString(),
            review_required: true,
            summary: {
                looking_away_ms: Math.round(durations.lookingAwayMs),
                no_face_ms: Math.round(durations.noFaceMs),
                multiple_faces_ms: Math.round(durations.multipleFacesMs),
                prolonged_looking_away_event_count: this.events.filter((event) => event.type === 'prolonged_looking_away').length,
                phone_event_count: this.events.filter((event) => event.type === 'phone_detected').length,
                total_events: this.events.length,
            },
            events: this.events,
        };
        console.log('[proctoring:report]', report);
        return report;
    }
}

export function logViolation(type, details, confidence = 1.0, snapshot = null) {
    if (!isCandidateAssessmentPage()) return;
    if (window.candidateProctoring && window.candidateProctoring.logger) {
        window.candidateProctoring.logger.record(type, confidence, details, snapshot);
    } else {
        const interviewId = document.body.dataset.interviewId;
        if (!interviewId) return;
        const csrfToken = document.querySelector('meta[name="csrf-token"]')?.content || window.csrfToken;

        fetch(`/candidate/log-violation/${interviewId}`, {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
                'X-CSRF-TOKEN': csrfToken
            },
            body: JSON.stringify({
                type: type,
                details: typeof details === 'object' ? JSON.stringify(details) : details,
                confidence: confidence,
                snapshot: snapshot
            })
        })
        .then(r => r.json())
        .then(() => {
            if (typeof BroadcastChannel !== 'undefined') {
                const callSigChannel = new BroadcastChannel('webrtc_call_' + interviewId);
                const liveSyncChannel = new BroadcastChannel('live_sync_' + interviewId);
                callSigChannel.postMessage({ type: 'violation_occurred', violation_type: type, details: details });
                liveSyncChannel.postMessage({ type: 'violation_logged', violation_type: type, details: details });
            }
            if (typeof window.pollReviewData === 'function') {
                window.pollReviewData();
            }
        })
        .catch(err => console.log('Log violation fetch error:', err));
    }
}

// --- System Desktop Screenshot Capture Engine ---
function getScreenShareVideoElement() {
    if (!screenShareVideoElem) {
        screenShareVideoElem = document.createElement('video');
        screenShareVideoElem.autoplay = true;
        screenShareVideoElem.muted = true;
        screenShareVideoElem.playsInline = true;
        screenShareVideoElem.style.position = 'fixed';
        screenShareVideoElem.style.top = '0px';
        screenShareVideoElem.style.left = '0px';
        screenShareVideoElem.style.width = '320px';
        screenShareVideoElem.style.height = '180px';
        screenShareVideoElem.style.opacity = '0.001';
        screenShareVideoElem.style.pointerEvents = 'none';
        screenShareVideoElem.style.zIndex = '-9999';
        document.body.appendChild(screenShareVideoElem);
    }
    return screenShareVideoElem;
}

export function captureAndUploadTabScreenshot(reason = 'tab_switch') {
    if (!isTabSwitchScreenshotEnabled || !isCandidateAssessmentPage()) return;
    if (reason !== 'tab_switch' && reason !== 'call_start' && reason !== 'external_ai_detected' && reason !== 'copy_event') return;

    try {
        const tempCanvas = document.createElement('canvas');
        let drewScreenStream = false;

        const isCallStart = (reason === 'call_start');
        const bannerLabel = isCallStart
            ? '📸 CALL STARTED • CANDIDATE SYSTEM SCREEN SNAPSHOT • ' + new Date().toLocaleString()
            : '🚨 CANDIDATE SYSTEM COMPUTER DESKTOP SNAPSHOT • ' + new Date().toLocaleString();

        if (typeof screenShareStream !== 'undefined' && screenShareStream && screenShareStream.getVideoTracks().length > 0) {
            const screenTrack = screenShareStream.getVideoTracks()[0];
            if (screenTrack && screenTrack.readyState === 'live') {
                try {
                    const vidElem = getScreenShareVideoElement();
                    if (vidElem.srcObject !== screenShareStream) {
                        vidElem.srcObject = screenShareStream;
                        vidElem.play().catch(() => {});
                    }

                    let rawW = vidElem.videoWidth || 1280;
                    let rawH = vidElem.videoHeight || 720;

                    if (vidElem.readyState >= 2 && rawW > 0 && rawH > 0) {
                        const maxW = 1280;
                        let targetW = rawW;
                        let targetH = rawH;
                        if (targetW > maxW) {
                            targetH = Math.round(targetH * (maxW / targetW));
                            targetW = maxW;
                        }

                        tempCanvas.width = targetW;
                        tempCanvas.height = targetH;
                        const tempCtx = tempCanvas.getContext('2d');
                        tempCtx.drawImage(vidElem, 0, 0, targetW, targetH);

                        tempCtx.fillStyle = 'rgba(15, 23, 42, 0.90)';
                        tempCtx.fillRect(0, tempCanvas.height - 42, tempCanvas.width, 42);
                        tempCtx.fillStyle = isCallStart ? '#10b981' : '#ef4444';
                        tempCtx.font = 'bold 14px sans-serif';
                        tempCtx.fillText(bannerLabel, 16, tempCanvas.height - 15);

                        uploadTabScreenshotBlob(tempCanvas.toDataURL('image/jpeg', 0.75), reason);
                        drewScreenStream = true;
                    }
                } catch(e) {
                    console.log('Screen stream draw exception:', e);
                }
            }
        }

        if (drewScreenStream) return;

        if (typeof window.html2canvas !== 'undefined' && !document.hidden) {
            window.html2canvas(document.body, { logging: false, useCORS: true, allowTaint: true, scale: 0.85 }).then(canvas => {
                const ctx = canvas.getContext('2d');
                ctx.fillStyle = 'rgba(15, 23, 42, 0.90)';
                ctx.fillRect(0, canvas.height - 42, canvas.width, 42);
                ctx.fillStyle = isCallStart ? '#10b981' : '#ef4444';
                ctx.font = 'bold 14px sans-serif';
                ctx.fillText(bannerLabel, 16, canvas.height - 15);
                uploadTabScreenshotBlob(canvas.toDataURL('image/jpeg', 0.75), reason);
            }).catch(() => {
                fallbackCompositeSnapshot(reason);
            });
        } else {
            fallbackCompositeSnapshot(reason);
        }
    } catch(e) {
        console.log('Candidate system screenshot capture exception:', e);
        fallbackCompositeSnapshot(reason);
    }
}

export function fallbackCompositeSnapshot(reason = 'tab_switch') {
    const interviewId = document.body.dataset.interviewId || '';
    const tempCanvas = document.createElement('canvas');
    const w = 1280;
    const h = 720;
    tempCanvas.width = w;
    tempCanvas.height = h;
    const tempCtx = tempCanvas.getContext('2d');

    tempCtx.fillStyle = '#0b0f19';
    tempCtx.fillRect(0, 0, w, h);
    tempCtx.fillStyle = '#1e293b';
    tempCtx.fillRect(0, 0, w, 50);
    tempCtx.fillStyle = '#38bdf8';
    tempCtx.font = 'bold 16px sans-serif';
    tempCtx.fillText('💻 Candidate System Workspace • ID: ' + interviewId, 20, 32);

    const codeDisplay = document.querySelector('.CodeMirror') || document.getElementById('code-editor') || document.getElementById('monaco-editor-container');
    tempCtx.fillStyle = '#020617';
    tempCtx.fillRect(20, 70, w - 40, h - 130);
    tempCtx.fillStyle = '#94a3b8';
    tempCtx.font = '13px monospace';
    const codeText = codeDisplay ? (codeDisplay.innerText || codeDisplay.value || '') : '';
    const lines = codeText.split('\n').slice(0, 30);
    lines.forEach((line, i) => {
        tempCtx.fillText(line.substring(0, 120), 35, 95 + (i * 18));
    });

    const isCallStart = (reason === 'call_start');
    tempCtx.fillStyle = 'rgba(15, 23, 42, 0.90)';
    tempCtx.fillRect(0, tempCanvas.height - 42, tempCanvas.width, 42);
    tempCtx.fillStyle = isCallStart ? '#10b981' : '#ef4444';
    tempCtx.font = 'bold 14px sans-serif';
    const text = isCallStart
        ? '📸 CALL STARTED • CANDIDATE SYSTEM SNAPSHOT • ' + new Date().toLocaleString()
        : '🚨 CANDIDATE SYSTEM SNAPSHOT • ' + new Date().toLocaleString();
    tempCtx.fillText(text, 16, tempCanvas.height - 15);

    uploadTabScreenshotBlob(tempCanvas.toDataURL('image/jpeg', 0.85), reason);
}

export function uploadTabScreenshotBlob(imageData, reason = 'tab_switch') {
    const interviewId = document.body.dataset.interviewId;
    if (!interviewId) return;
    const csrfToken = document.querySelector('meta[name="csrf-token"]')?.content || window.csrfToken;

    fetch(`/candidate/upload-tab-screenshot/${interviewId}`, {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'X-CSRF-TOKEN': csrfToken
        },
        body: JSON.stringify({ image: imageData, reason: reason })
    })
    .then(r => r.json())
    .then(data => {
        console.log('Candidate system screenshot saved:', data);
    })
    .catch(err => console.log('System screenshot fetch error:', err));
}

export function isEntireScreenShare(track) {
    if (!track || !track.getSettings) return true;
    const settings = track.getSettings();
    const surface = settings.displaySurface;

    if (surface) {
        const allowedSurfaces = ['monitor', 'screen'];
        if (!allowedSurfaces.includes(surface)) {
            return false;
        }
    }

    if (window.screen && window.screen.width && settings.width) {
        if (settings.width < (window.screen.width * 0.65) && settings.height < (window.screen.height * 0.65)) {
            return false;
        }
    }

    return true;
}

export function isScreenSharingActive() {
    return Boolean(screenShareStream && screenShareStream.active && screenShareStream.getVideoTracks().some(t => t.readyState === 'live'));
}

export function enforceBrowserFullscreen() {
    if (!isScreenSharingActive() || document.fullscreenElement) return;

    beginNativePrompt();
    if (document.documentElement.requestFullscreen) {
        document.documentElement.requestFullscreen()
            .then(() => {
                endNativePrompt();
                armTrailingBuffer(1000);
            })
            .catch(() => {
                endNativePrompt();
                showFullscreenRequiredModal();
            });
    } else {
        endNativePrompt();
        showFullscreenRequiredModal();
    }
}

export function showFullscreenRequiredModal() {
    if (!isScreenSharingActive() || document.fullscreenElement) return;
    if (typeof window.Swal !== 'undefined') {
        window.Swal.fire({
            icon: 'warning',
            title: 'Fullscreen Mode Required',
            text: 'Your assessment must be conducted in Fullscreen mode while screen sharing. Please click below to enter Fullscreen.',
            confirmButtonText: 'Enter Fullscreen Mode',
            confirmButtonColor: '#6366f1',
            allowOutsideClick: false,
            allowEscapeKey: false
        }).then(() => {
            if (isScreenSharingActive()) {
                enforceBrowserFullscreen();
            }
        });
    }
}

let candidateScreenPeerInstance = null;
const activeScreenCallTargets = new Set();

export function broadcastCandidateScreenStream(stream) {
    if (!stream || !stream.active) return;
    const videoTracks = stream.getVideoTracks();
    if (!videoTracks || videoTracks.length === 0 || videoTracks[0].readyState !== 'live') return;

    const interviewId = document.body?.dataset?.interviewId;
    const submissionId = document.body?.dataset?.submissionId || interviewId;
    if (!interviewId || typeof window.Peer === 'undefined') return;

    const subIdPart = (submissionId && submissionId !== String(interviewId)) ? ('_' + submissionId) : '';
    const legacyScreenPeerId = 'interviewer_screen_' + interviewId + subIdPart;

    const targetPeerIds = new Set();

    // Collect dedicated screen receiver targets from active interviewers
    if (typeof window.latestActivePeers !== 'undefined' && Array.isArray(window.latestActivePeers)) {
        window.latestActivePeers.forEach(p => {
            if (p.peer_id && (p.peer_id.startsWith('interviewer_') || p.role === 'admin' || p.role === 'interviewer')) {
                const screenTargetId = p.peer_id.replace('interviewer_', 'interviewer_screen_');
                targetPeerIds.add(screenTargetId);
            }
        });
    }

    if (targetPeerIds.size === 0) {
        targetPeerIds.add(legacyScreenPeerId);
    }

    const makeCalls = (peer) => {
        targetPeerIds.forEach(targetId => {
            if (activeScreenCallTargets.has(targetId)) return;

            try {
                console.log('[WebRTC Screen] Broadcasting screen to interviewer target:', targetId);
                const outCall = peer.call(targetId, stream);
                if (outCall) {
                    activeScreenCallTargets.add(targetId);
                    outCall.on('close', () => {
                        console.log('[WebRTC Screen] Screen call closed for target:', targetId);
                        activeScreenCallTargets.delete(targetId);
                    });
                    outCall.on('error', (err) => {
                        console.warn('[WebRTC Screen] Screen call error for target:', targetId, err);
                        activeScreenCallTargets.delete(targetId);
                    });
                }
            } catch(e) {
                activeScreenCallTargets.delete(targetId);
            }
        });
    };

    if (candidateScreenPeerInstance && !candidateScreenPeerInstance.destroyed && candidateScreenPeerInstance.open) {
        makeCalls(candidateScreenPeerInstance);
    } else {
        if (candidateScreenPeerInstance && !candidateScreenPeerInstance.destroyed) {
            try { candidateScreenPeerInstance.destroy(); } catch(e) {}
        }
        activeScreenCallTargets.clear();
        const screenPeerId = 'cand_screen_' + interviewId + subIdPart + '_' + Date.now();
        initMeteredIceServers().then(iceServers => {
            candidateScreenPeerInstance = new window.Peer(screenPeerId, {
                config: { iceServers: iceServers }
            });
            candidateScreenPeerInstance.on('open', () => {
                makeCalls(candidateScreenPeerInstance);
            });
            candidateScreenPeerInstance.on('error', err => {
                console.warn('[WebRTC Screen] Candidate screen peer error:', err);
            });
        }).catch(() => {
            candidateScreenPeerInstance = new window.Peer(screenPeerId);
            candidateScreenPeerInstance.on('open', () => {
                makeCalls(candidateScreenPeerInstance);
            });
        });
    }
}

// --- Screen Share Enforcement & Live Overlay Detector (Category 6) ---
export function startScreenShare() {
    if (!navigator.mediaDevices || !navigator.mediaDevices.getDisplayMedia) {
        alert('Screen sharing is not supported on your browser.');
        return;
    }

    beginNativePrompt();

    navigator.mediaDevices.getDisplayMedia({
        video: {
            displaySurface: 'monitor'
        },
        audio: false
    })
    .then(stream => {
        endNativePrompt();
        const track = stream.getVideoTracks()[0];

        // Enforce ENTIRE SCREEN share across all browsers
        if (!isEntireScreenShare(track)) {
            track.stop();
            screenShareStream = null;
            logViolation('tab_switch', 'Candidate attempted non-entire screen share (tab or window)');

            if (typeof window.Swal !== 'undefined') {
                window.Swal.fire({
                    icon: 'error',
                    title: 'Entire Screen Share Required',
                    html: 'You selected a single tab or window.<br><br><b>You MUST select "Entire Screen" (or whole monitor)</b> to continue your interview.',
                    confirmButtonText: 'Reshare Entire Screen Now',
                    confirmButtonColor: '#ef4444',
                    allowOutsideClick: false,
                    allowEscapeKey: false
                }).then(() => {
                    setTimeout(startScreenShare, 300);
                });
            } else {
                alert('Entire Screen share is required. Please select Entire Screen.');
                setTimeout(startScreenShare, 300);
            }
            return;
        }

        screenShareStream = stream;
        const vidElem = getScreenShareVideoElement();
        vidElem.srcObject = stream;
        vidElem.play().catch(() => {});

        updateScreenShareButton(true);

        enforceBrowserFullscreen();

        broadcastCandidateScreenStream(stream);

        track.onended = () => {
            screenShareStream = null;
            activeScreenCallTargets.clear();
            if (candidateScreenPeerInstance && !candidateScreenPeerInstance.destroyed) {
                try { candidateScreenPeerInstance.destroy(); } catch(e) {}
                candidateScreenPeerInstance = null;
            }
            updateScreenShareButton(false);

            if (document.fullscreenElement) {
                try { document.exitFullscreen().catch(() => {}); } catch(e) {}
            }

            logViolation('tab_switch', 'Candidate stopped screen sharing');
        };

        initLiveOverlayDetector();
    })
    .catch(err => {
        endNativePrompt();
        console.log('Screen sharing cancelled/denied:', err);
        screenShareStream = null;
        activeScreenCallTargets.clear();
        updateScreenShareButton(false);
    });
}

export function stopScreenShare() {
    if (screenShareStream) {
        try {
            screenShareStream.getTracks().forEach(track => track.stop());
        } catch(e) {}
        screenShareStream = null;
    }
    activeScreenCallTargets.clear();
    if (candidateScreenPeerInstance && !candidateScreenPeerInstance.destroyed) {
        try { candidateScreenPeerInstance.destroy(); } catch(e) {}
        candidateScreenPeerInstance = null;
    }
    updateScreenShareButton(false);

    if (document.fullscreenElement) {
        try { document.exitFullscreen().catch(() => {}); } catch(e) {}
    }

    logViolation('tab_switch', 'Candidate stopped screen sharing');
}

export function toggleScreenShare() {
    if (screenShareStream && screenShareStream.active && screenShareStream.getVideoTracks().length > 0 && screenShareStream.getVideoTracks()[0].readyState === 'live') {
        stopScreenShare();
    } else {
        startScreenShare();
    }
}

export function updateScreenShareButton(active) {
    const btn = document.getElementById('share-screen-btn');
    if (!btn) return;
    if (active) {
        btn.innerHTML = '🛑 Stop Screen Sharing';
        btn.style.background = '#ef4444';
        btn.style.borderColor = '#dc2626';
        btn.onclick = stopScreenShare;
    } else {
        btn.innerHTML = '🖥️ Share Screen with Interviewer';
        btn.style.background = 'linear-gradient(135deg, #6366f1 0%, #0078d4 100%)';
        btn.style.borderColor = '#6366f1';
        btn.onclick = startScreenShare;
    }
}

export function initLiveOverlayDetector() {
    if (!isCandidateAssessmentPage()) return;
    if (overlayCheckInterval) clearInterval(overlayCheckInterval);

    overlayCheckInterval = setInterval(() => {
        if (!screenShareStream || screenShareStream.getVideoTracks().length === 0) return;
        const track = screenShareStream.getVideoTracks()[0];
        if (track.readyState !== 'live') return;

        const vidElem = getScreenShareVideoElement();
        if (!vidElem || vidElem.videoWidth === 0) return;

        try {
            if (!document.hasFocus()) {
                const now = Date.now();
                if (now - lastTabSwitchTime > 3000) {
                    lastTabSwitchTime = now;
                    logViolation('tab_switch', 'Candidate window lost focus during active screen share');
                    captureAndUploadTabScreenshot('tab_switch');
                }
            }
        } catch(e) {}
    }, 2000);
}

// --- Continuous Speech Recognition (Category 5) ---
export function initQuestionRepeatDetection() {
    if (!isCandidateAssessmentPage()) return;
    const SpeechRecognition = window.SpeechRecognition || window.webkitSpeechRecognition;
    if (!SpeechRecognition) return;

    try {
        const speechRec = new SpeechRecognition();
        speechRec.continuous = true;
        speechRec.interimResults = false;
        speechRec.lang = 'en-US';

        speechRec.onresult = function(event) {
            for (let i = event.resultIndex; i < event.results.length; ++i) {
                if (event.results[i].isFinal) {
                    const transcript = event.results[i][0].transcript.trim().toLowerCase();
                    if (transcript.length < 4) continue;

                    const pageText = (document.body ? document.body.innerText : '').toLowerCase();

                    const words = transcript.split(/\s+/).filter(w => w.length > 3);
                    let matchedWordCount = 0;
                    words.forEach(w => {
                        if (pageText.includes(w)) matchedWordCount++;
                    });
                    const isReadingQuestionOnScreen = words.length >= 3 && (matchedWordCount / words.length) >= 0.5;

                    const isRepeatedSpeech = candidateSpeechHistory.some(prev => {
                        return prev === transcript || (transcript.length > 8 && prev.includes(transcript)) || (prev.length > 8 && transcript.includes(prev));
                    });

                    candidateSpeechHistory.push(transcript);
                    if (candidateSpeechHistory.length > 15) candidateSpeechHistory.shift();

                    const phoneKeywords = ['hello', 'can you hear me', 'on phone', 'calling', 'call you back', 'hold on', 'on the line', 'speaker', 'phone', 'mobile', 'call me', 'speak later', 'hey call', 'on a call'];
                    const isPhoneTalk = phoneKeywords.some(kw => transcript.includes(kw));
                    const isCallConnected = window.isCallConnected ? window.isCallConnected() : false;

                    if (isPhoneTalk) {
                        logViolation('talking_on_phone', `Candidate detected talking on phone / phone call during assessment: "${transcript}"`);
                    } else if (isReadingQuestionOnScreen || isRepeatedSpeech) {
                        if (window.candidateProctoring?.lastStates?.lookingAway) {
                            logViolation('reading_external_device', `Candidate detected reading from external device or mobile screen: "${transcript}"`);
                        } else {
                            logViolation('question_repetition', `Candidate detected reading / repeating question out loud: "${transcript}" (suspected AI prompt ingestion)`);
                        }
                    } else {
                        if (!isCallConnected && transcript.length > 10) {
                            logViolation('talking_secondary_person', `Candidate speaking out loud to secondary person in room: "${transcript}"`);
                        }
                    }
                }
            }
        };

        speechRec.onerror = function() {
            setTimeout(() => { try { speechRec.start(); } catch(e) {} }, 4000);
        };

        speechRec.onend = function() {
            setTimeout(() => { try { speechRec.start(); } catch(e) {} }, 1500);
        };

        speechRec.start();
    } catch(e) {}
}

// --- Candidate Proctoring Event Listeners (Tab focus, Clipboard, Hotkeys, DOM Observer, PiP, Fullscreen) ---
export function initCandidateProctoringListeners() {
    if (!isCandidateAssessmentPage()) return;

    // 1. Visibility Change (Tab Switched / Window Minimized)
    document.addEventListener('visibilitychange', function () {
        if (!isCandidateAssessmentPage() || isFocusSuppressed()) return;
        if (document.hidden) {
            const now = Date.now();
            if (now - lastTabSwitchTime > 1000) {
                lastTabSwitchTime = now;
                logViolation('tab_switch', 'Candidate switched browser tab or minimized window');
                captureAndUploadTabScreenshot();
            }
        }
    });

    // 2. Window Blur (Assessment Window Lost Focus)
    window.addEventListener('blur', function () {
        if (!isCandidateAssessmentPage() || isFocusSuppressed()) return;
        const now = Date.now();
        if (now - lastTabSwitchTime > 1000) {
            lastTabSwitchTime = now;
            logViolation('tab_switch', 'Candidate assessment window lost focus');
            captureAndUploadTabScreenshot('tab_switch');
        }
    });

    // 3. Mouse Viewport Departure
    document.addEventListener('mouseleave', function () {
        if (!isCandidateAssessmentPage() || isFocusSuppressed()) return;
        const now = Date.now();
        if (now - lastTabSwitchTime > 2500) {
            lastTabSwitchTime = now;
            logViolation('tab_switch', 'Candidate cursor departed assessment window viewport');
            captureAndUploadTabScreenshot('tab_switch');
        }
    });

    // 4. Clipboard Events (Paste into Editor / Copy from Assessment Window)
    document.addEventListener('paste', function () {
        if (!isCandidateAssessmentPage()) return;
        logViolation('paste_event', 'Candidate pasted content into editor window (possible AI answer paste)');
    }, true);

    document.addEventListener('copy', function () {
        if (!isCandidateAssessmentPage()) return;
        logViolation('copy_event', 'Candidate copied text from assessment window (possible Parakeet AI prompt ingestion)');
        captureAndUploadTabScreenshot();
    });

    // 5. Global Keydown AI Hotkey Interception (Capture Phase)
    window.addEventListener('keydown', function (e) {
        if (!isCandidateAssessmentPage()) return;
        if (e.code === 'Tab' || e.key === 'Tab') return;

        const key = (e.key || '').toLowerCase();
        const code = (e.code || '').toLowerCase();
        const isAlt = e.altKey;
        const isCmd = e.metaKey;
        const isCtrl = e.ctrlKey;
        const isShift = e.shiftKey;

        const isAiHotkey = (isAlt && (key === ' ' || code === 'space' || key === 'p' || key === 'a' || key === 's' || key === 'c' || key === 'v' || key === 'q' || key === 'w' || key === 'e' || key === 'x' || key === 'z')) ||
                           (isCmd && (key === ' ' || code === 'space' || key === 'p' || key === 'a' || key === 's' || key === 'x')) ||
                           (isCtrl && isShift && (key === 'a' || key === 'p' || key === 's' || key === 'i' || key === 'c' || key === 'x')) ||
                           (isCmd && isShift && (key === 'a' || key === 'p' || key === 's' || key === 'x' || key === '4' || key === '3')) ||
                           (isCtrl && isAlt) ||
                           (key === 'f12' || code === 'f12' || key === 'f11' || code === 'f11');

        if (isAiHotkey) {
            logViolation('external_ai_detected', `candidate might use external ai: Intercepted AI assistant shortcut hotkey (${e.code || e.key})`);
            captureAndUploadTabScreenshot('external_ai_detected');
        }
    }, true);

    // 6. Injected Extension DOM Observer
    try {
        const aiMutationObserver = new MutationObserver(mutations => {
            if (!isCandidateAssessmentPage()) return;
            for (const mutation of mutations) {
                for (const node of mutation.addedNodes) {
                    if (node.nodeType === 1) {
                        const nodeStr = ((node.id || '') + ' ' + (node.className || '') + ' ' + (node.getAttribute('src') || '')).toLowerCase();
                        if (nodeStr.includes('parakeet') || nodeStr.includes('finalround') || nodeStr.includes('copilot') || nodeStr.includes('ai-assistant') || nodeStr.includes('otter')) {
                            logViolation('external_ai_detected', 'candidate might use external ai: Injected AI extension overlay element detected in DOM (' + node.tagName + ')');
                            captureAndUploadTabScreenshot('external_ai_detected');
                        }
                    }
                }
            }
        });
        aiMutationObserver.observe(document.documentElement, { childList: true, subtree: true });
    } catch(e) {}

    // 7. Picture-in-Picture Floating AI Window Detector
    setInterval(function() {
        if (!isCandidateAssessmentPage()) return;
        if (document.pictureInPictureElement) {
            logViolation('external_ai_detected', 'candidate might use external ai: External Picture-in-Picture floating AI window active');
        }
    }, 6000);

    // 8. Fullscreen Exit Listener (Only enforced when screen sharing is active)
    document.addEventListener('fullscreenchange', function() {
        if (!isCandidateAssessmentPage() || isFocusSuppressed() || !isScreenSharingActive()) return;
        if (!document.fullscreenElement) {
            logViolation('tab_switch', 'Candidate exited full-screen proctoring mode while screen sharing');
            captureAndUploadTabScreenshot();
            showFullscreenRequiredModal();
        }
    });
}

// --- MediaPipe Proctoring Classes ---

class WarningPresenter {
    constructor() {
        this.element = null;
    }

    show(message) {
        // Candidate-side violation notifications removed per directive.
        // All violations are silently logged and sent to the server.
    }
}

class SnapshotService {
    constructor(video, canvas) {
        this.video = video;
        this.canvas = canvas;
    }

    capture() {
        if (!this.video || this.video.readyState < 2 || !this.video.videoWidth) return null;
        const width = Math.min(640, this.video.videoWidth);
        const height = Math.round(width * this.video.videoHeight / this.video.videoWidth);
        this.canvas.width = width;
        this.canvas.height = height;
        this.canvas.getContext('2d').drawImage(this.video, 0, 0, width, height);
        return this.canvas.toDataURL('image/jpeg', SNAPSHOT_QUALITY);
    }
}

class FacePoseDetector {
    constructor(landmarker) {
        this.landmarker = landmarker;
    }

    detect(video, timestamp) {
        const result = this.landmarker.detectForVideo(video, timestamp);
        const faces = result.faceLandmarks || [];
        return {
            count: faces.length,
            pose: faces[0] ? this.estimatePose(faces[0]) : null,
            gaze: faces[0] ? this.estimateGaze(faces[0]) : null,
        };
    }

    estimatePose(landmarks) {
        const point = (index) => landmarks[index];
        const leftEye = point(33);
        const rightEye = point(263);
        const nose = point(1);
        const mouth = point(13);
        const eyeMidX = (leftEye.x + rightEye.x) / 2;
        const eyeMidY = (leftEye.y + rightEye.y) / 2;
        const eyeDistance = Math.max(0.001, Math.abs(rightEye.x - leftEye.x));
        const yaw = (nose.x - eyeMidX) / eyeDistance;
        const pitch = (nose.y - eyeMidY) / Math.max(0.001, Math.abs(mouth.y - eyeMidY));
        return { yaw, pitch, confidence: Math.min(1, 0.5 + Math.abs(yaw) * 0.4 + Math.abs(pitch - 0.5) * 0.2) };
    }

    estimateGaze(landmarks) {
        const leftEye = this.estimateEyeGaze(landmarks, {
            corners: [33, 133],
            top: [159, 158],
            bottom: [145, 153],
            iris: [468, 469, 470, 471, 472],
        });
        const rightEye = this.estimateEyeGaze(landmarks, {
            corners: [362, 263],
            top: [386, 385],
            bottom: [374, 380],
            iris: [473, 474, 475, 476, 477],
        });
        const eyes = [leftEye, rightEye].filter(Boolean);
        if (!eyes.length) return null;

        const horizontal = eyes.reduce((total, eye) => total + eye.horizontal, 0) / eyes.length;
        const vertical = eyes.reduce((total, eye) => total + eye.vertical, 0) / eyes.length;
        const confidence = Math.min(1, 0.45 + Math.max(Math.abs(horizontal - 0.5), Math.abs(vertical - 0.5)) * 1.4);

        return { horizontal, vertical, confidence };
    }

    estimateEyeGaze(landmarks, config) {
        const points = [...config.corners, ...config.top, ...config.bottom, ...config.iris].map((index) => landmarks[index]);
        if (points.some((point) => !point)) return null;

        const cornerA = landmarks[config.corners[0]];
        const cornerB = landmarks[config.corners[1]];
        const topY = this.averageCoordinate(landmarks, config.top, 'y');
        const bottomY = this.averageCoordinate(landmarks, config.bottom, 'y');
        const irisX = this.averageCoordinate(landmarks, config.iris, 'x');
        const irisY = this.averageCoordinate(landmarks, config.iris, 'y');
        const leftX = Math.min(cornerA.x, cornerB.x);
        const rightX = Math.max(cornerA.x, cornerB.x);

        return {
            horizontal: this.clamp01((irisX - leftX) / Math.max(0.001, rightX - leftX)),
            vertical: this.clamp01((irisY - topY) / Math.max(0.001, bottomY - topY)),
        };
    }

    averageCoordinate(landmarks, indexes, coordinate) {
        return indexes.reduce((total, index) => total + landmarks[index][coordinate], 0) / indexes.length;
    }

    clamp01(value) {
        return Math.max(0, Math.min(1, value));
    }
}

class LookingAwayClassifier {
    classify(face) {
        const reasons = [];
        const pose = face.pose;
        const gaze = face.gaze;

        if (pose && Math.abs(pose.yaw) > HEAD_YAW_THRESHOLD) reasons.push('head_yaw');
        if (pose && pose.pitch < HEAD_PITCH_UP_THRESHOLD) reasons.push('head_up');
        if (pose && pose.pitch > HEAD_PITCH_DOWN_THRESHOLD) reasons.push('head_down');
        if (gaze && gaze.horizontal < GAZE_HORIZONTAL_LEFT_THRESHOLD) reasons.push('eye_gaze_left');
        if (gaze && gaze.horizontal > GAZE_HORIZONTAL_RIGHT_THRESHOLD) reasons.push('eye_gaze_right');
        if (gaze && gaze.vertical > GAZE_DOWN_THRESHOLD) reasons.push('eye_gaze_down');

        return {
            active: reasons.length > 0,
            confidence: this.confidence(reasons, pose, gaze),
            details: {
                reasons,
                yaw: pose?.yaw ?? null,
                pitch: pose?.pitch ?? null,
                gaze_horizontal: gaze?.horizontal ?? null,
                gaze_vertical: gaze?.vertical ?? null,
            },
        };
    }

    confidence(reasons, pose, gaze) {
        if (!reasons.length) return 0;
        return Math.max(
            reasons.some((reason) => reason.startsWith('head_')) ? pose?.confidence || 0 : 0,
            reasons.some((reason) => reason.startsWith('eye_')) ? gaze?.confidence || 0 : 0,
        );
    }
}

class PhoneDetector {
    constructor(detector) {
        this.detector = detector;
    }

    detect(video, timestamp) {
        if (!this.detector || !video || video.readyState < 2 || !video.videoWidth) return null;
        try {
            const ts = Math.round(timestamp);
            const result = this.detector.detectForVideo(video, ts);
            const detections = result ? (result.detections || []) : [];
            for (const detection of detections) {
                const categories = detection.categories || [];
                for (const category of categories) {
                    const name = (category.categoryName || category.displayName || '').toLowerCase();
                    const score = category.score || 0;
                    if (/cell phone|mobile phone|phone|remote|handheld|device|calculator|tablet/i.test(name) && score >= 0.15) {
                        console.log('[proctoring:phone_detected_raw]', { name, score });
                        return { confidence: score, label: category.categoryName || category.displayName || 'cell phone' };
                    }
                }
            }
        } catch (e) {
            console.warn('[proctoring:phone_detect_error]', e.message);
        }
        return null;
    }
}

class DurationTracker {
    constructor() {
        this.activeSince = { lookingAway: null, noFace: null, multipleFaces: null };
        this.total = { lookingAwayMs: 0, noFaceMs: 0, multipleFacesMs: 0 };
    }

    update(name, active, now) {
        const startedAt = this.activeSince[name];
        if (active && startedAt === null) this.activeSince[name] = now;
        if (!active && startedAt !== null) {
            this.total[`${name}Ms`] += now - startedAt;
            this.activeSince[name] = null;
        }
    }

    finish(now) {
        Object.keys(this.activeSince).forEach((name) => this.update(name, false, now));
        return { ...this.total };
    }
}

class ProlongedLookingAwayTracker {
    constructor({ thresholdMs, recheckMs }) {
        this.thresholdMs = thresholdMs;
        this.recheckMs = recheckMs;
        this.startedAt = null;
        this.nextCheckAt = null;
    }

    update(active, now) {
        if (!active) {
            this.reset();
            return null;
        }

        if (this.startedAt === null) this.startedAt = now;

        const durationMs = now - this.startedAt;
        if (durationMs < this.thresholdMs || (this.nextCheckAt !== null && now < this.nextCheckAt)) return null;

        const recheck = this.nextCheckAt !== null;
        this.nextCheckAt = now + this.recheckMs;

        return {
            duration_ms: Math.round(durationMs),
            threshold_ms: this.thresholdMs,
            recheck,
            recheck_interval_ms: this.recheckMs,
            next_check_at: new Date(Date.now() + this.recheckMs).toISOString(),
        };
    }

    reset() {
        this.startedAt = null;
        this.nextCheckAt = null;
    }
}

class CornerGazeClassifier {
    classify(face) {
        const pose = face.pose;
        const gaze = face.gaze;
        if (!pose || !gaze) return null;

        const horiz = gaze.horizontal;
        const vert = gaze.vertical;
        const yaw = pose.yaw;
        const pitch = pose.pitch;

        const isLeft = (horiz <= 0.42 || yaw <= -0.16);
        const isRight = (horiz >= 0.58 || yaw >= 0.16);
        const isTop = (vert <= 0.44 || pitch <= 0.38);
        const isBottom = (vert >= 0.56 || pitch >= 0.62);

        let corner = null;
        let cornerLabel = null;

        if (isLeft && isTop) {
            corner = 'top_left';
            cornerLabel = 'Top-Left Screen Corner';
        } else if (isRight && isTop) {
            corner = 'top_right';
            cornerLabel = 'Top-Right Screen Corner';
        } else if (isLeft && isBottom) {
            corner = 'bottom_left';
            cornerLabel = 'Bottom-Left Screen Corner';
        } else if (isRight && isBottom) {
            corner = 'bottom_right';
            cornerLabel = 'Bottom-Right Screen Corner';
        } else if (isBottom) {
            corner = 'bottom_center';
            cornerLabel = 'Screen Bottom / Downside';
        } else if (isLeft) {
            corner = 'screen_left';
            cornerLabel = 'Screen Left Side';
        } else if (isRight) {
            corner = 'screen_right';
            cornerLabel = 'Screen Right Side';
        }

        if (!corner) return null;

        const confidence = Math.min(1, 0.5 + Math.max(Math.abs(horiz - 0.5), Math.abs(vert - 0.5)) * 1.2);

        return {
            corner,
            corner_label: cornerLabel,
            confidence,
            details: {
                corner,
                corner_label: cornerLabel,
                yaw,
                pitch,
                gaze_horizontal: horiz,
                gaze_vertical: vert,
            }
        };
    }
}

class CornerGazeTracker {
    constructor({ thresholdMs, recheckMs, graceMs }) {
        this.thresholdMs = thresholdMs;
        this.recheckMs = recheckMs;
        this.graceMs = graceMs;

        this.currentCorner = null;
        this.startedAt = null;
        this.lastActiveAt = null;
        this.nextCheckAt = null;
    }

    update(cornerResult, now) {
        if (!cornerResult) {
            if (this.lastActiveAt && (now - this.lastActiveAt) > this.graceMs) {
                this.reset();
            }
            return null;
        }

        const activeCorner = cornerResult.corner;

        const isRelatedZone = (this.currentCorner && (
            (this.currentCorner.startsWith('bottom_') && activeCorner.startsWith('bottom_')) ||
            (this.currentCorner.startsWith('top_') && activeCorner.startsWith('top_')) ||
            (this.currentCorner === activeCorner)
        ));

        if (!this.currentCorner || !isRelatedZone) {
            this.currentCorner = activeCorner;
            this.startedAt = now;
            this.nextCheckAt = null;
        } else {
            this.currentCorner = activeCorner;
        }

        this.lastActiveAt = now;

        const durationMs = now - this.startedAt;
        if (durationMs < this.thresholdMs || (this.nextCheckAt !== null && now < this.nextCheckAt)) {
            return null;
        }

        this.nextCheckAt = now + this.recheckMs;

        return {
            corner: activeCorner,
            corner_label: cornerResult.corner_label,
            duration_ms: Math.round(durationMs),
            duration_s: Math.round(durationMs / 1000),
            confidence: cornerResult.confidence,
            details: {
                ...cornerResult.details,
                duration_ms: Math.round(durationMs),
                duration_s: Math.round(durationMs / 1000),
            }
        };
    }

    reset() {
        this.currentCorner = null;
        this.startedAt = null;
        this.lastActiveAt = null;
        this.nextCheckAt = null;
    }
}

class CandidateProctoring {
    constructor({ sessionId, video, canvas }) {
        this.sessionId = sessionId;
        this.video = video;
        this.canvas = canvas;
        this.logger = new StructuredEventLogger(sessionId);
        this.warning = new WarningPresenter();
        this.snapshot = new SnapshotService(video, canvas);
        this.durations = new DurationTracker();
        this.lookingAwayClassifier = new LookingAwayClassifier();
        this.prolongedLookingAway = new ProlongedLookingAwayTracker({
            thresholdMs: PROLONGED_LOOKING_AWAY_MS,
            recheckMs: PROLONGED_LOOKING_AWAY_RECHECK_MS,
        });
        this.cornerGazeClassifier = new CornerGazeClassifier();
        this.cornerGazeTracker = new CornerGazeTracker({
            thresholdMs: CORNER_FIXATION_MS,
            recheckMs: CORNER_RECHECK_MS,
            graceMs: CORNER_JITTER_GRACE_MS,
        });
        this.startedAt = new Date().toISOString();
        this.lastSampleAt = 0;
        this.lastPhoneEventAt = 0;
        this.lastStates = { lookingAway: false, noFace: false, multipleFaces: false };
        this.running = false;
        this.modelsReady = false;
        this.reported = false;
    }

    async start() {
        if (this.running) return;
        try {
            const vision = await this.importVisionModule();
            const fileset = await vision.FilesetResolver.forVisionTasks(WASM_ROOT);

            const faceLandmarker = await this.withAmdLoaderDisabled(() =>
                this.createModel(vision.FaceLandmarker, fileset, {
                    modelAssetPath: FACE_MODEL_URL,
                    runningMode: 'VIDEO', numFaces: 3, minFaceDetectionConfidence: 0.5,
                    minFacePresenceConfidence: 0.5, minTrackingConfidence: 0.5,
                })
            );
            this.faceDetector = new FacePoseDetector(faceLandmarker);

            try {
                const objectDetector = await this.withAmdLoaderDisabled(() =>
                    this.createModel(vision.ObjectDetector, fileset, {
                        modelAssetPath: OBJECT_MODEL_URL,
                        runningMode: 'VIDEO', maxResults: 10, scoreThreshold: 0.35,
                    })
                );
                this.phoneDetector = new PhoneDetector(objectDetector);
                console.log('[proctoring:object_detector_ready]');
            } catch (objErr) {
                console.error('[proctoring:object_detector_failed]', objErr);
            }

            this.modelsReady = true;
            this.running = true;
            this.scheduleNextSample();
            console.log('[proctoring:ready]', { schema: 'candidate-proctoring/v1', session_id: this.sessionId });
        } catch (error) {
            console.error('[proctoring:error]', { schema: 'candidate-proctoring/v1', session_id: this.sessionId, code: 'model_initialization_failed', message: error.message });
        }
    }

    async importVisionModule() {
        try {
            return await import(/* @vite-ignore */ VISION_MODULE_URL);
        } catch (primaryError) {
            console.warn('[proctoring:warning]', {
                schema: 'candidate-proctoring/v1', session_id: this.sessionId,
                code: 'vision_cdn_fallback', message: primaryError.message,
            });
            return import(/* @vite-ignore */ VISION_MODULE_FALLBACK_URL);
        }
    }

    async withAmdLoaderDisabled(callback) {
        const amdGlobals = ['define', 'require', 'requirejs'];
        const saved = amdGlobals.map((name) => ({ name, value: globalThis[name] }));
        amdGlobals.forEach((name) => {
            try {
                delete globalThis[name];
            } catch (error) {
                globalThis[name] = undefined;
            }
        });

        try {
            return await callback();
        } finally {
            saved.forEach(({ name, value }) => {
                if (value === undefined) delete globalThis[name];
                else globalThis[name] = value;
            });
        }
    }

    async createModel(Model, fileset, options) {
        try {
            return await Model.createFromOptions(fileset, { ...options, baseOptions: { modelAssetPath: options.modelAssetPath, delegate: 'GPU' } });
        } catch (gpuError) {
            console.warn('[proctoring:warning]', { schema: 'candidate-proctoring/v1', session_id: this.sessionId, code: 'gpu_delegate_unavailable', message: gpuError.message });
            return Model.createFromOptions(fileset, { ...options, baseOptions: { modelAssetPath: options.modelAssetPath, delegate: 'CPU' } });
        }
    }

    scheduleNextSample() {
        if (!this.running) return;
        setTimeout(() => this.sample(), SAMPLE_INTERVAL_MS);
    }

    sample() {
        if (!this.running) return;
        if (this.video.readyState < 2 || !this.video.videoWidth) return this.scheduleNextSample();
        const timestamp = performance.now();
        try {
            const face = this.faceDetector.detect(this.video, timestamp);
            const phone = this.phoneDetector ? this.phoneDetector.detect(this.video, timestamp) : null;
            this.processFace(face, timestamp);
            this.processPhone(phone, timestamp);
        } catch (error) {
            console.error('[proctoring:error]', { schema: 'candidate-proctoring/v1', session_id: this.sessionId, code: 'frame_processing_failed', message: error.message });
        }
        this.lastSampleAt = timestamp;
        this.scheduleNextSample();
    }

    processFace(result, now) {
        const noFace = result.count === 0;
        const multipleFaces = result.count > 1;
        const lookingAwayResult = this.lookingAwayClassifier.classify(result);
        const cornerGazeResult = this.cornerGazeClassifier.classify(result);

        this.durations.update('noFace', noFace, now);
        this.durations.update('multipleFaces', multipleFaces, now);
        this.durations.update('lookingAway', lookingAwayResult.active, now);

        this.transition('noFace', noFace, noFace ? 0.95 : 0, { face_count: result.count }, NO_FACE_GRACE_MS, 'Candidate face is not visible');
        this.transition('multipleFaces', multipleFaces, multipleFaces ? 0.95 : 0, { face_count: result.count }, 0, 'Multiple faces detected');
        this.transition('lookingAway', lookingAwayResult.active, lookingAwayResult.confidence, lookingAwayResult.details, LOOKING_AWAY_GRACE_MS, 'Please look toward the camera');
        this.trackProlongedLookingAway(lookingAwayResult, now);
        this.trackCornerGaze(cornerGazeResult, now);
    }

    transition(name, active, confidence, details, graceMs, message) {
        if (active === this.lastStates[name]) return;
        if (active && graceMs > 0 && this.durations.activeSince[name] && performance.now() - this.durations.activeSince[name] < graceMs) return;
        this.lastStates[name] = active;
        if (active) {
            this.warning.show(message);
            const eventName = name === 'lookingAway' ? 'looking_away' : name === 'noFace' ? 'face_missing' : 'multiple_faces';
            this.logger.record(eventName, confidence, details, this.snapshot.capture());
        }
    }

    trackProlongedLookingAway(lookingAwayResult, now) {
        const prolongedEvent = this.prolongedLookingAway.update(lookingAwayResult.active, now);
        if (!prolongedEvent) return;

        this.warning.show(`Candidate has been looking away for over ${Math.round(PROLONGED_LOOKING_AWAY_MS / 1000)} seconds`);
        this.logger.record('prolonged_looking_away', lookingAwayResult.confidence, {
            ...prolongedEvent,
            ...lookingAwayResult.details,
        }, this.snapshot.capture());
    }

    trackCornerGaze(cornerResult, now) {
        const cornerEvent = this.cornerGazeTracker.update(cornerResult, now);
        if (!cornerEvent) return;

        this.logger.record('prolonged_corner_gaze', cornerEvent.confidence, {
            ...cornerEvent.details,
        }, this.snapshot.capture());
    }

    processPhone(phone, now) {
        if (!phone || now - this.lastPhoneEventAt < PHONE_EVENT_COOLDOWN_MS) return;
        this.lastPhoneEventAt = now;
        this.warning.show('Possible phone detected in camera frame');
        this.logger.record('phone_detected', phone.confidence, { label: phone.label }, this.snapshot.capture());
    }

    stop() {
        if (this.reported) return null;
        this.running = false;
        this.reported = true;
        return this.logger.report(this.startedAt, new Date().toISOString(), this.durations.finish(performance.now()));
    }
}

// --- Candidate Proctoring Auto-Boot & Listener Registration ---
function bootCandidateProctoring() {
    if (!isCandidateAssessmentPage()) return;
    const sessionId = document.body.dataset.interviewId;
    if (!sessionId) return;

    const video = document.getElementById('webcam');
    const canvas = document.getElementById('proctor-canvas') || document.createElement('canvas');

    // Boot MediaPipe proctoring if webcam element exists
    if (video && navigator.mediaDevices) {
        const proctor = new CandidateProctoring({ sessionId, video, canvas });
        window.candidateProctoring = proctor;
        const startWhenReady = () => proctor.start();
        if (video.readyState >= 2) startWhenReady();
        video.addEventListener('loadeddata', startWhenReady, { once: true });
        const callStatus = document.getElementById('call-status-badge');
        if (callStatus) {
            const statusObserver = new MutationObserver(() => {
                if (/ended/i.test(callStatus.textContent || '')) proctor.stop();
            });
            statusObserver.observe(callStatus, { childList: true, characterData: true, subtree: true });
        }
        window.addEventListener('pagehide', () => proctor.stop(), { once: true });
    }

    // Initialize all candidate cheat detection event listeners & speech analysis
    initCandidateProctoringListeners();
    initQuestionRepeatDetection();
}

// --- Window Bindings for Proctoring ---
if (typeof window !== 'undefined') {
    window.logViolation = logViolation;
    window.captureAndUploadTabScreenshot = captureAndUploadTabScreenshot;
    window.fallbackCompositeSnapshot = fallbackCompositeSnapshot;
    window.uploadTabScreenshotBlob = uploadTabScreenshotBlob;
    window.beginNativePrompt = beginNativePrompt;
    window.endNativePrompt = endNativePrompt;
    window.armTrailingBuffer = armTrailingBuffer;
    window.isFocusSuppressed = isFocusSuppressed;
    window.isScreenSharingActive = isScreenSharingActive;
    window.startScreenShare = startScreenShare;
    window.stopScreenShare = stopScreenShare;
    window.toggleScreenShare = toggleScreenShare;
    window.updateScreenShareButton = updateScreenShareButton;
    window.initLiveOverlayDetector = initLiveOverlayDetector;
    window.initQuestionRepeatDetection = initQuestionRepeatDetection;
    window.initCandidateProctoringListeners = initCandidateProctoringListeners;
    window.isCandidateAssessmentPage = isCandidateAssessmentPage;
    window.isCandidateCallActive = isCandidateCallActive;
    window.broadcastCandidateScreenStream = broadcastCandidateScreenStream;
    window.getScreenShareStream = () => screenShareStream;

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', bootCandidateProctoring, { once: true });
    } else {
        bootCandidateProctoring();
    }
}