/**
 * The extras a client asks for, by name: `true` asks for a plain extra, a list of keys asks for a
 * group (`facets: ['status', 'tag']`), `false` switches a default off.
 */
export type TExtraRequest = Record<string, boolean | ReadonlyArray<string>>;
/**
 * What may come back for `Extra`: a group keyed by the keys asked for. Every entry is optional - a
 * route that offers no extras, or an older server, answers none - and the route may add defaults.
 */
export type TExtraResult<Extra extends TExtraRequest> = {
    [K in keyof Extra as Extra[K] extends false ? never : K]?: Extra[K] extends ReadonlyArray<infer Key extends string> ? Record<Key, unknown> : unknown;
} & Record<string, unknown>;
/** The client half of the list-extras contract: what goes in `x-request-extra`. */
export declare class HttpExtraRequest {
    /**
     * The header value for what a call asks for - `name`, `-name`, `name(key,key)` - led by `-*` when
     * the call wants the rows alone, every default off. `undefined` when it asks for nothing.
     */
    static toHeader(opts: {
        extra?: TExtraRequest;
        isEveryDefaultOff?: boolean;
    }): string | undefined;
    /** The header name, for a client that sets headers itself. */
    static readonly HEADER: "x-request-extra";
}
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