import * as React from 'react';
import type { AgMessage } from '../types.js';
export interface ThreadScrollApi {
    scrollToBottom(options?: {
        behavior?: ScrollBehavior | undefined;
    }): void;
    scrollToMessage(id: string, options?: {
        block?: ScrollLogicalPosition | undefined;
    }): void;
    isPinned(): boolean;
}
type ScrollToKey = (key: React.Key, o?: {
    align?: 'start' | 'center' | 'end' | 'auto';
}) => void;
/** REQ-SURF-110: true while any message streams (message status, a text or
    reasoning part still streaming, or a tool input still streaming). */
export declare const isStreaming: (messages: readonly AgMessage[]) => boolean;
/**
 * REQ-SURF-108..110. Pinned while `scrollHeight − scrollTop − clientHeight ≤
 * pinThreshold`. While pinned, any growth of the log content (new messages,
 * streaming text inside the last message, late layout) assigns
 * `scrollTop = scrollHeight` at most once per animation frame. A user
 * scroll-up unpins; a new `user` message re-pins. Prepending history while
 * unpinned keeps the first visible message at the same offset. Never
 * `scrollIntoView`; smooth scrolling only for the explicit jump at motion full,
 * and never while any message streams (every scroll is then `auto`). Frames
 * go through the shared motion ticker (REQ-MAT-51), not requestAnimationFrame.
 */
export declare function useThreadScroll(viewportRef: React.RefObject<HTMLElement | null>, contentRef: React.RefObject<HTMLElement | null>, opts: {
    messages: readonly AgMessage[];
    pinThreshold: number;
    /** Present only when the thread is virtualized (REQ-SURF-110). */
    scrollToKey?: ScrollToKey | undefined;
    /** motion === 'full' → the jump pill scrolls smoothly. */
    smoothJump: boolean;
    newMessagesText: (n: number) => string;
}): {
    pinned: React.RefObject<boolean>;
    unpinnedCount: number;
    onScroll: () => void;
    onUserInput: () => void;
    scrollToBottom: (options?: {
        behavior?: ScrollBehavior | undefined;
    }) => void;
    jumpToLatest: () => void;
    api: ThreadScrollApi;
};
export {};
//# sourceMappingURL=useThreadScroll.d.ts.map