import { IZFilterMetadata, IZFilterSubject } from './filter-subject.mjs';
/**
 * The operators for an {@link IZFilterUnary} filter.
 */
export declare enum ZOperatorUnary {
    /**
     * Is null.
     */
    IsNull = "null",
    /**
     * Is not null.
     */
    IsNotNull = "is-not-null"
}
/**
 * Represents a yes/no style filter.
 */
export type IZFilterUnary = IZFilterSubject<ZOperatorUnary>;
/**
 * Represents a builder for a UnaryFilter object.
 */
export declare class ZFilterUnaryBuilder {
    /**
     * The __type__ identifier for an {@link IZFilterUnary} object.
     */
    static readonly Type = "unary";
    private _filter;
    /**
     * Initializes a new instance of this object.
     */
    constructor();
    /**
     * Sets the subject.
     *
     * @param val -
     *        The value to set.
     *
     * @returns
     *        This object.
     */
    subject(val: string): this;
    /**
     * Sets the operator.
     *
     * @param val -
     *        The operator to set.
     *
     * @returns
     *        This object.
     */
    operator(val: ZOperatorUnary): this;
    /**
     * Sets the operator to is null.
     *
     * @returns
     *        This object.
     */
    isNull: () => this;
    /**
     * Sets the operator to is null.
     *
     * @returns
     *        This object.
     */
    isNotNull: () => this;
    /**
     * Returns a copy of the built filter.
     *
     * @returns
     *        A copy of the current filter.
     */
    build(): IZFilterUnary;
}
/**
 * Type guard for determining if a target filter is a unary filter.
 *
 * @param filter -
 *        The filter to test.
 *
 * @returns
 *        True if filters type is a unary filter.  False otherwise.
 */
export declare function isUnaryFilter(filter: IZFilterMetadata | null | undefined): filter is IZFilterUnary;
/**
 * A list of all unary operators.
 */
export declare const ZOperatorsUnary: ZOperatorUnary[];
/**
 * Gets whether a candidate string represents a unary operator.
 *
 * @returns
 *        Type guard true if candidate is a unary operator, false
 *        otherwise.
 */
export declare function isUnaryOperator(candidate: string | null | undefined): candidate is ZOperatorUnary;
/**
 * Comparators for unary operators.
 */
export declare const ZUnaryComparators: Record<ZOperatorUnary, (data: any) => boolean>;