/** Deterministic identity visuals: initials + a stable hue from the name. */

export function initials(name: string): string {
  const words = name.trim().split(/\s+/).filter((w) => w !== '')
  if (words.length === 0) return '?'
  const first = words[0]!.charAt(0)
  const second = words.length > 1 ? words[1]!.charAt(0) : ''
  return (first + second).toUpperCase()
}

/** FNV-1a over the name → hue bucket; same name always gets the same colour. */
export function avatarHue(name: string): number {
  let h = 0x811c9dc5
  for (let i = 0; i < name.length; i++) {
    h ^= name.charCodeAt(i)
    h = Math.imul(h, 0x01000193)
  }
  return (h >>> 0) % 360
}

/** Soft tinted background + readable foreground for both themes. */
export function avatarColors(name: string): { bg: string; fg: string } {
  const h = avatarHue(name)
  return {
    bg: `hsl(${h} 42% 50% / 0.16)`,
    fg: `light-dark(hsl(${h} 45% 34%), hsl(${h} 45% 74%))`,
  }
}