/**
 * WCAG 2.1 Contrast Ratio Utilities
 *
 * Pure math functions for calculating contrast ratios between colors.
 * Used for automated accessibility testing of theme color tokens.
 *
 * @see https://www.w3.org/TR/WCAG21/#contrast-minimum
 */
/**
 * Check if a string is a valid hex color (#fff, #ffffff, #fffa, #ffffff80).
 * Rejects rgba(), hsl(), named colors, etc.
 */
export function isHexColor(value) {
    return /^#([0-9a-fA-F]{3,8})$/.test(value);
}
/**
 * Check if a string is an opaque hex color (#rgb or #rrggbb only).
 * Rejects alpha-bearing hex (#rgba, #rrggbbaa) since contrast
 * calculation requires compositing against a known background.
 */
export function isOpaqueHexColor(value) {
    return /^#([0-9a-fA-F]{3}|[0-9a-fA-F]{6})$/.test(value);
}
/**
 * Parse a hex color string to RGB tuple.
 * Handles shorthand (#fff), full (#ffffff), and alpha (#ffffff80).
 * Strips alpha channel — contrast calculation uses only RGB.
 *
 * @throws {Error} If input is not a valid hex color
 */
export function hexToRgb(hex) {
    if (!isHexColor(hex)) {
        throw new Error(`Not a hex color: "${hex}". Only #rgb, #rrggbb, #rrggbbaa formats supported.`);
    }
    let h = hex.slice(1); // Remove #
    // Expand shorthand: #fff → ffffff, #fffa → ffffffaa
    if (h.length === 3 || h.length === 4) {
        h = h
            .slice(0, 3)
            .split('')
            .map((c) => c + c)
            .join('');
    }
    else {
        // Strip alpha from 8-digit hex
        h = h.slice(0, 6);
    }
    const num = parseInt(h, 16);
    return [(num >> 16) & 0xff, (num >> 8) & 0xff, num & 0xff];
}
/**
 * Calculate relative luminance per WCAG 2.1.
 * Applies sRGB linearization then weighted sum.
 *
 * @see https://www.w3.org/TR/WCAG21/#dfn-relative-luminance
 */
export function relativeLuminance(r, g, b) {
    const [rs, gs, bs] = [r, g, b].map((c) => {
        const s = c / 255;
        return s <= 0.04045 ? s / 12.92 : Math.pow((s + 0.055) / 1.055, 2.4);
    });
    return 0.2126 * rs + 0.7152 * gs + 0.0722 * bs;
}
/**
 * Calculate WCAG 2.1 contrast ratio between two hex colors.
 * Returns a number >= 1, where 21:1 is maximum (black on white).
 *
 * @example contrastRatio('#000000', '#ffffff') // 21
 */
export function contrastRatio(color1, color2) {
    const [r1, g1, b1] = hexToRgb(color1);
    const [r2, g2, b2] = hexToRgb(color2);
    const l1 = relativeLuminance(r1, g1, b1);
    const l2 = relativeLuminance(r2, g2, b2);
    const lighter = Math.max(l1, l2);
    const darker = Math.min(l1, l2);
    return (lighter + 0.05) / (darker + 0.05);
}
const WCAG_THRESHOLDS = {
    AA: 4.5,
    'AA-large': 3.0,
    AAA: 7.0,
};
/**
 * Check whether a foreground/background pair meets a WCAG contrast level.
 *
 * - AA: 4.5:1 (normal text < 18pt)
 * - AA-large: 3.0:1 (large text >= 18pt, UI components)
 * - AAA: 7.0:1 (enhanced contrast)
 */
export function meetsWCAG(fg, bg, level) {
    return contrastRatio(fg, bg) >= WCAG_THRESHOLDS[level];
}
//# sourceMappingURL=contrast.js.map