export type LayoutSurfaces = Record<string, string>;
export declare const isValidHex: (value?: string | null) => boolean;
export type LayoutSurfaceInput = {
    /** The variant's own `backgroundStyle`. */
    base: LayoutSurfaces | undefined;
    /** `chatWindow.backgroundColor` as the deployment set it. */
    chosen: string | undefined | null;
    /** The variant's name; only Neptune is treated specially, and only for its wash. */
    variant: string;
};
/**
 * True when the variant's own colours are the page, so a deployment colour cannot be substituted
 * underneath them. Luna and Neptune pick their text, panels and accents against a fixed page;
 * Erebus washes a gradient it derives from whatever colour it is given.
 */
export declare const variantOwnsItsPage: (base: LayoutSurfaces | undefined, variant: string) => boolean;
/**
 * A variant either owns its page or derives the whole of it from the chosen colour — never both.
 *
 * Painting one surface with the chosen colour and leaving the rest at the variant's values is
 * what produced the half-states: Neptune with a white background kept its near-white body text
 * and black panels, so one half was unreadable and the other belonged to a different design.
 */
export declare function resolveLayoutSurfaces(input: LayoutSurfaceInput): LayoutSurfaces;