import type { EventKind } from "@a4anthony/proctorkit-types";
export interface ObserverEmitter {
    emit(kind: EventKind, payload?: Record<string, unknown>): void;
}
export interface ScreenshotObserverConfig {
    /**
     * Render a blur overlay over the page whenever a screenshot is
     * suspected. The candidate sees a frosted overlay and (after 5s) a
     * "Resume Session" button. Useful as a deterrent and as a way to
     * obscure delayed-capture tools that snapshot the page after the
     * candidate switches back. Default: false.
     */
    blurOnSuspicion?: boolean;
    /**
     * Milliseconds before the warning text + Resume button reveal on top
     * of the blur. Default: 5000.
     */
    resumeRevealMs?: number;
    /**
     * Customise the deterrent overlay copy.
     */
    resumeButtonText?: string;
    warningText?: string;
}
export type ScreenshotTrigger = "keyboard" | "visibility" | "blur";
/**
 * Watches for behaviours that indicate the candidate is trying to take
 * a screenshot. Emits a consolidated `screenshot.attempted` event with
 * the trigger ("keyboard" / "visibility" / "blur") in the payload, so
 * proctors see a single, semantic row in the timeline.
 *
 * Optionally renders a blur overlay over the page so that delayed
 * capture tools snapshot a blurred view.
 *
 * Screenshot-key handling (ported from teq-lib's proven approach):
 *
 *   1. Cmd+Shift keydown latches `screenshotKeyActive = true` and shows
 *      the blur. macOS swallows the digit keydown for Cmd+Shift+3/4/5
 *      and the keyup for the modifiers, so we cannot rely on detecting
 *      the digit — the latch is what carries state across the OS
 *      clipping tool's lifecycle.
 *   2. window.blur fires while the OS clipping tool is up → re-shows
 *      the blur (idempotent).
 *   3. window.focus fires when the clipping tool closes. We gate
 *      hideBlur on `!screenshotKeyActive`. The flag is still true
 *      because no keyup ever cleared it, so the overlay stays.
 *   4. The candidate either clicks Resume (clears flag + hides) or
 *      releases one of the listed modifiers cleanly back into the page
 *      (clears flag + hides). After 5s the Resume button reveals as a
 *      fallback exit so the candidate isn't stuck.
 *
 * IMPORTANT: this is a deterrent, not real prevention. OS-level
 * screenshot keys (Cmd+Shift+3 on macOS, PrintScreen on Windows) are
 * intercepted by the OS before the page sees them, so the screenshot
 * usually completes before the observer's preventDefault runs. The
 * forensic value is the *attempt log*, not the block.
 */
export declare class ScreenshotObserver {
    private readonly emitter;
    private listening;
    private readonly config;
    private readonly listeners;
    private overlay;
    private resumeButton;
    private warningEl;
    private buttonTimer;
    private isDragging;
    private screenshotKeyActive;
    constructor(emitter: ObserverEmitter, config: ScreenshotObserverConfig | boolean | undefined);
    start(): void;
    stop(): void;
    private bind;
    private emit;
    private showBlur;
    private hideBlur;
    private mountOverlay;
    private removeOverlay;
}
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