import { describe, it, expect } from 'vitest';
import { AVATAR_PALETTE } from './avatarPalette';

// ─── WCAG 2.1 relative-luminance / contrast (1.4.3) ──────────────────────────
// White initials sit on every palette color (DESIGN_RULES §5). The avatar
// background is theme-invariant (same hex in light and dark), so a single
// white-on-color check covers both themes.

function srgbToLinear(channel: number): number {
	const c = channel / 255;
	return c <= 0.03928 ? c / 12.92 : Math.pow((c + 0.055) / 1.055, 2.4);
}

function relativeLuminance(hex: string): number {
	const r = parseInt(hex.slice(1, 3), 16);
	const g = parseInt(hex.slice(3, 5), 16);
	const b = parseInt(hex.slice(5, 7), 16);
	return 0.2126 * srgbToLinear(r) + 0.7152 * srgbToLinear(g) + 0.0722 * srgbToLinear(b);
}

function contrastRatio(a: string, b: string): number {
	const la = relativeLuminance(a);
	const lb = relativeLuminance(b);
	const [hi, lo] = la > lb ? [la, lb] : [lb, la];
	return (hi + 0.05) / (lo + 0.05);
}

const WHITE = '#ffffff';

describe('AVATAR_PALETTE', () => {
	it('has exactly 10 colors (DESIGN_RULES §5)', () => {
		expect(AVATAR_PALETTE).toHaveLength(10);
	});

	it('is all lowercase 6-digit hex', () => {
		for (const c of AVATAR_PALETTE) {
			expect(c).toMatch(/^#[0-9a-f]{6}$/);
		}
	});

	it('has no duplicate colors (each person color is distinct)', () => {
		expect(new Set(AVATAR_PALETTE).size).toBe(AVATAR_PALETTE.length);
	});

	it('every color meets WCAG AA (>=4.5:1) against white initials in both themes', () => {
		for (const c of AVATAR_PALETTE) {
			expect(contrastRatio(c, WHITE)).toBeGreaterThanOrEqual(4.5);
		}
	});
});