import type { AlphaValue, Hex, Hex8, HSL } from './types';
/**
 * * Applies an opacity value to a color string.
 * @param color The color string in hex to apply opacity to.
 * @param opacity The opacity value as a percentage (0-100).
 * @returns The color string with the opacity value applied.
 */
export declare const _applyOpacity: (color: Hex, opacity: string) => Hex8;
/**
 * * Helper function to generate a random HSL color.
 *
 * @returns A random HSL color string.
 */
export declare const _generateRandomHSL: () => HSL;
/**
 * * Helper function to check if the new color is visually too similar to the previous one.
 * * It compares the hue, saturation, and lightness difference between the new color and the last one generated.
 *
 * @param recentColors - Array of recently generated colors.
 * @param newColor - The new color to compare.
 * @returns `Boolean` : `true` if the new color is similar to the previous one.
 */
export declare const _isSimilarToLast: (recentColors: string[], newColor: string) => boolean;
/**
 * @private Checks if a number is valid alpha value.
 *
 * @param value Alpha value to check.
 * @returns `true` if it's a valid alpha value, `false` if not.
 */
export declare function _isValidAlpha(value: number): value is AlphaValue;
/** @private Validates RGB component (0–255). */
export declare function _isValidRGBComponent(value: number): boolean;
/** @private Validates HSL hue (0–360). */
export declare function _isValidHue(value: number): boolean;
/** @private Validates HSL percentage components (0–100). */
export declare function _isValidPercentage(value: number): boolean;