import type { ChatScrollDirection } from './chatScrollIntent.js';
import { type ScrollGeometry } from './chatScrollPolicy.js';
export type DirectionalScrollGeometry = ScrollGeometry & {
    capturedAt: number;
    direction: ChatScrollDirection;
};
export type PendingScrollDirection = {
    capturedAt: number;
    direction: ChatScrollDirection;
};
export type RecordScrollIntentArgs = {
    direction: ChatScrollDirection;
    current: ScrollGeometry;
    now: number;
};
export type RecordUserScrollArgs = {
    previousScrollTop: number;
    current: ScrollGeometry;
    now: number;
};
export type GetProgressPreservationTargetArgs = {
    current: ScrollGeometry;
    now: number;
};
export type ChatScrollProgressPreserverOptions = {
    activeWindowMs?: number;
    movementThresholdPx?: number;
    minAdjustmentPx?: number;
};
export type PreserveMinimumScrollProgressArgs = {
    previous: ScrollGeometry;
    current: ScrollGeometry;
    minAdjustmentPx?: number;
};
export type PreserveDirectionalScrollProgressArgs = {
    direction: ChatScrollDirection;
    previous: ScrollGeometry;
    current: ScrollGeometry;
    minAdjustmentPx?: number;
};
export declare const getGapFromBottom: (geometry: ScrollGeometry) => number;
export declare const getScrollProgress: (geometry: ScrollGeometry) => number;
/**
 * When content grows under an actively downward-scrolling user, keep the
 * scrollbar from losing normalized progress through the now-taller viewport.
 */
export declare const preserveMinimumScrollProgressTarget: ({ previous, current, minAdjustmentPx }: PreserveMinimumScrollProgressArgs) => number | null;
/**
 * Preserve the user's scrollbar trajectory through late layout growth.
 * - Downward input should not lose normalized scroll progress.
 * - Upward input should not gain normalized scroll progress.
 */
export declare const preserveDirectionalScrollProgressTarget: ({ direction, previous, current, minAdjustmentPx }: PreserveDirectionalScrollProgressArgs) => number | null;
export declare class ChatScrollProgressPreserver {
    #private;
    constructor(options?: ChatScrollProgressPreserverOptions);
    recordScrollIntent({ direction, current, now }: RecordScrollIntentArgs): void;
    recordUserScroll({ previousScrollTop, current, now }: RecordUserScrollArgs): void;
    getPreservationTarget({ current, now }: GetProgressPreservationTargetArgs): number | null;
    isActive(now: number): boolean;
    commitAdjustment(current: ScrollGeometry, now: number): void;
    reset(): void;
}