/**
 * Sanitizes a user-supplied URL to prevent phishing and script injection.
 *
 * Rules:
 * - Only allows https:// and http:// schemes
 * - Blocks javascript:, data:, vbscript:, and all other schemes
 * - Returns null for invalid / unsafe URLs (caller should hide the link)
 *
 * VPN/Tor users are unaffected — this validates the URL scheme & structure,
 * not the user's network origin.
 */
export function sanitizeUrl(url: string | undefined | null): string | null {
  if (!url) return null;

  const trimmed = url.trim();
  if (!trimmed) return null;

  try {
    const parsed = new URL(trimmed);
    // Only allow safe schemes
    if (parsed.protocol !== 'https:' && parsed.protocol !== 'http:') {
      return null;
    }
    return parsed.href;
  } catch {
    // Not a valid URL
    return null;
  }
}

/**
 * Extracts just the hostname for display (e.g. "Opens: example.com")
 */
export function urlDomain(url: string): string {
  try {
    return new URL(url).hostname.replace(/^www\./, '');
  } catch {
    return url;
  }
}

/**
 * Sanitizes a tel: or mailto: href.
 * Only allows the specific scheme, strips anything else.
 */
export function sanitizeTel(value: string | undefined | null): string | null {
  if (!value) return null;
  const trimmed = value.trim();
  // Allow digits, +, -, spaces, parentheses only
  const digits = trimmed.replace(/[^0-9+\-\s().]/g, '');
  return digits.length >= 5 ? `tel:${digits}` : null;
}

export function sanitizeEmail(value: string | undefined | null): string | null {
  if (!value) return null;
  const trimmed = value.trim();
  // Basic email pattern
  if (/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(trimmed)) {
    return `mailto:${trimmed}`;
  }
  return null;
}