/** Göteborg municipality postcodes used for delivery validation. */
const GOTHENBURG_POSTCODE_PREFIXES = ['41', '42', '43'] as const;

const GOTHENBURG_NAME_PATTERNS = [
  'göteborg',
  'gothenburg',
  'goteborg',
  'göteborgs stad',
  'goteborgs stad',
] as const;

export interface DeliverableAddressFields {
  city?: string;
  municipality?: string;
  postcode?: string;
  countryCode?: string;
  formatted?: string;
}

function normalize(value: string): string {
  return value.trim().toLowerCase();
}

function matchesGothenburgName(value: string): boolean {
  const normalized = normalize(value);
  return GOTHENBURG_NAME_PATTERNS.some((pattern) => normalized.includes(pattern));
}

function hasGothenburgPostcode(postcode?: string): boolean {
  if (!postcode) return false;
  const digits = postcode.replace(/\s/g, '');
  return GOTHENBURG_POSTCODE_PREFIXES.some((prefix) => digits.startsWith(prefix));
}

export function isGothenburgDeliveryAddress(fields: DeliverableAddressFields): boolean {
  if (fields.countryCode && normalize(fields.countryCode) !== 'se') return false;

  if (matchesGothenburgName(fields.city ?? '')) return true;
  if (matchesGothenburgName(fields.municipality ?? '')) return true;
  if (hasGothenburgPostcode(fields.postcode)) return true;

  const formatted = normalize(fields.formatted ?? '');
  if (
    formatted.includes('göteborg') ||
    formatted.includes('gothenburg') ||
    formatted.includes('goteborg')
  ) {
    return (
      hasGothenburgPostcode(fields.postcode) ||
      /\b41\d{3}\b|\b42\d{3}\b|\b43\d{3}\b/.test(formatted)
    );
  }

  return false;
}