import type { ChatStatus } from "../types/index.js";
export interface UseVirtualStickToBottomParams {
    /** Total number of rows rendered by the list, including non-message header rows. */
    rowCount: number;
    /** Whether a response is currently streaming (keep pinned to the growing last row). */
    isStreaming?: boolean;
    status?: ChatStatus;
    /** Current number of messages (drives auto-scroll on new messages). */
    messagesCount: number;
    /** Stable id of the first message - used to distinguish prepends (load older) from appends. */
    firstMessageId?: string;
    /** Number of non-message rows rendered before the messages (e.g. the load-more trigger). */
    headerOffset?: number;
    /**
     * Value that changes whenever the streaming (last) row's content updates - typically the
     * last message reference. react-window only fires `onRowsRendered` when the set of visible
     * rows changes, not when an already-mounted row is re-measured taller, so an explicit signal
     * is needed to keep pinning to the bottom while a single row grows in place.
     */
    streamingSignal?: unknown;
    /** Value that changes when a trailing non-message row appears or disappears. */
    trailingContentSignal?: unknown;
}
/**
 * Stick-to-bottom / reverse-scroll behavior for the virtualized message list.
 *
 * Replaces the MutationObserver-based {@link useSmartScroll} (which cannot work under
 * virtualization, since off-screen rows are not in the DOM and the scroll container is owned
 * by react-window).
 *
 * Off-screen row heights are only estimates in react-window, so neither `scrollHeight` nor a single
 * `scrollToRow` call is reliable on its own. Both corrections here are therefore re-applied across a
 * few frames (until measured heights settle), and prepend preservation anchors to a real rendered
 * row (`data-message-id`) near the viewport rather than to the distant, still-estimated bottom:
 * - keeps the last row pinned to the bottom while streaming, unless the user scrolled up;
 * - preserves the on-screen position of the top visible message when older messages are prepended.
 */
export declare function useVirtualStickToBottom({ rowCount, isStreaming, status, messagesCount, firstMessageId, headerOffset, streamingSignal, trailingContentSignal, }: UseVirtualStickToBottomParams): {
    listRef: import("react").Dispatch<import("react").SetStateAction<import("react-window", { with: { "resolution-mode": "import" } }).ListImperativeAPI | null | undefined>>;
    isPrepending: boolean;
};