/**
 * Browser-side interaction observation. D7.
 *
 * This is the collector, and it collects only what the hard constraints need to
 * be checkable. Notably it does **not** record what was typed, where a pointer
 * moved, or any field value: the impossible-idle-action constraint needs to know
 * *whether* interaction occurred, not what it contained.
 *
 * No platform API is used outside this directory, per D7: `src/core/` stays free
 * of DOM types so the same model runs on either side of the wire.
 */
/** Counters for one field, or for a form as a whole. */
export type InteractionCounts = {
    /** Pointer events: down, move within the element, up. */
    readonly pointer: number;
    /** Key events. Count only, never which keys. */
    readonly keyboard: number;
    /** Paste, drop, and autofill-shaped input with no preceding keystroke. */
    readonly injected: number;
    /** Milliseconds from first interaction to submission, or `undefined`. */
    readonly durationMs: number | undefined;
    /** Whether the field held a value at submission. */
    readonly populated: boolean;
};
export declare const EMPTY_COUNTS: InteractionCounts;
/**
 * Minimal surface the collector needs, so it can be tested without a DOM and
 * without a headless browser. Any `HTMLElement` satisfies it structurally.
 */
export type Observable = {
    addEventListener(type: string, listener: (event: unknown) => void, options?: unknown): void;
    removeEventListener(type: string, listener: (event: unknown) => void, options?: unknown): void;
};
export type ValueSource = {
    /** Whether the watched input currently holds a value. */
    hasValue(): boolean;
};
export type CollectorOptions = {
    /** Defaults to `Date.now`. Injected for the same reason as D11. */
    readonly now?: () => number;
};
/**
 * Watch one element and report interaction counts.
 *
 * `stop()` removes every listener. Call it on unmount: a collector that outlives
 * its element is a leak, and one that keeps counting after submission reports
 * numbers that describe the wrong interaction.
 */
export declare function watchInteraction(target: Observable, value: ValueSource, options?: CollectorOptions): {
    counts: () => InteractionCounts;
    reset(): void;
    stop(): void;
};
/**
 * Reduce counts to the observation shape a declared invariant reads. D16.
 *
 * The collector produces counters; invariants consume a plain object. Keeping the
 * reduction here means the invariant never sees browser detail, and the core never
 * sees a DOM type.
 */
export declare function toObservation(counts: InteractionCounts): {
    readonly fieldPopulated: boolean;
    readonly interactions: number;
    readonly injected: number;
    readonly durationMs: number | undefined;
};
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