import md5 from 'md5'

const gravatarCache = new Map<string, string>()

/**
 * Returns Gravatar avatar URL for the given email, or empty string if no email.
 * Gravatar expects: trim, lowercase, then MD5 hex. Use empty string to show a placeholder (e.g. initial letter) in the UI.
 * Results are memoized by (email, size) to avoid recomputing MD5 on every render.
 *
 * @param email - User email (optional)
 * @param size - Avatar size in pixels (default 64; navbar 32, drawer 40, profile 64–80)
 */
export function useGravatarUrl(email: string | undefined, size?: number): string {
  const normalized = email?.trim().toLowerCase()
  if (!normalized) return ''
  const s = size ?? 64
  const key = `${normalized}\n${s}`
  const cached = gravatarCache.get(key)
  if (cached !== undefined) return cached
  const hash = md5(normalized)
  const url = `https://www.gravatar.com/avatar/${hash}?s=${s}&d=identicon`
  gravatarCache.set(key, url)
  return url
}