export function toCents(price: string | number): number {
  const n = typeof price === 'string' ? parseFloat(price) : price;
  if (Number.isNaN(n) || n < 0) {
    throw new Error('invalid price');
  }
  return Math.round(n * 100);
}

export function formatPrice(cents: number): string {
  return `$${(cents / 100).toFixed(2)}`;
}

// RFC 5321 caps an address at 254 characters; reject anything longer up front so
// validation cost stays bounded regardless of what a client posts.
const MAX_EMAIL_LENGTH = 254;

// Both patterns are anchored single character classes with no overlapping
// alternatives, so they match in linear time. Splitting on '@' and '.' in code
// rather than in one combined pattern avoids the ambiguous (and backtracking)
// `[^\s@]+\.[^\s@]+` domain match.
const LOCAL_PART_RE = /^[^\s@]+$/;
const DOMAIN_LABEL_RE = /^[^\s@.]+$/;

export function isValidEmail(email: string): boolean {
  const trimmed = email.trim();
  if (trimmed.length === 0 || trimmed.length > MAX_EMAIL_LENGTH) {
    return false;
  }

  const at = trimmed.indexOf('@');
  if (at === -1 || at !== trimmed.lastIndexOf('@')) {
    return false;
  }

  if (!LOCAL_PART_RE.test(trimmed.slice(0, at))) {
    return false;
  }

  const labels = trimmed.slice(at + 1).split('.');
  return labels.length >= 2 && labels.every((label) => DOMAIN_LABEL_RE.test(label));
}

// antd's preset Tag colours. Kept as the single source of truth for tag
// colours so the admin palette picker and the auto-assignment below can never
// drift apart — the frontend renders whatever string lands in tags.color.
export const TAG_COLORS = [
  'magenta', 'red', 'volcano', 'orange', 'gold', 'lime',
  'green', 'cyan', 'blue', 'geekblue', 'purple'
];

// Tags get a colour the moment they're created inline from the item form, with
// no prompt. Deriving it from the name (rather than picking at random or
// round-robining on insert order) means the same tag name always lands on the
// same colour, so a tag deleted and re-added doesn't silently change colour.
// The admin can still override it afterwards.
export function tagColorFor(name: string): string {
  const normalized = name.trim().toLowerCase();
  // djb2 — cheap, well-spread for short strings, and stable across Node
  // versions. `| 0` keeps it in int32 range instead of drifting into float.
  let hash = 5381;
  for (let i = 0; i < normalized.length; i++) {
    hash = ((hash << 5) + hash + normalized.charCodeAt(i)) | 0;
  }
  return TAG_COLORS[Math.abs(hash) % TAG_COLORS.length];
}

export const MARKETING_CONSENT_TEXT =
  'I want to receive occasional emails about new one-of-a-kind items from Redefined Designs. I can unsubscribe at any time.';