/**
 * @factory/ui — deterministic name → hue mapping (PURE).
 *
 * `hashNameToHue` maps any name to a stable hue in [0, 359] so avatars get a
 * consistent color across sessions (FNV-1a, case-insensitive, trimmed).
 * The AVATAR itself is rendered as `hsl(hue 60% 80%)`-style CSS with the hue
 * inlined — this is the one sanctioned exception to the "no hard-coded colors"
 * rule, because avatar colors are user-derived, not theme tokens.
 */

/** FNV-1a 32-bit hash of a string (case-insensitive, whitespace-trimmed). */
export function hashString(s: string): number {
  let h = 0x811c9dc5;
  const text = s.trim().toLowerCase();
  for (let i = 0; i < text.length; i += 1) {
    h ^= text.charCodeAt(i);
    h = Math.imul(h, 0x01000193);
  }
  return h >>> 0;
}

/** Deterministic hue 0–359 for a name (stable across sessions and themes). */
export function hashNameToHue(name: string): number {
  if (name.trim().length === 0) return 0;
  return hashString(name) % 360;
}

/** CSS color string for an avatar from a name: light fill + darker text. */
export function avatarHsl(name: string, lightness = 82): string {
  const hue = hashNameToHue(name);
  return `hsl(${hue} 55% ${lightness}%)`;
}