stdnum/src/be/vat.ts

Standard Number Validation

/**
 * BTW, TVA, NWSt, ondernemingsnummer (Belgian enterprise number).
 *
 * The enterprise number (ondernemingsnummer) is a unique identifier of
 * companies within the Belgian administrative services. It was previously
 * the VAT ID number. The number consists of 10 digits.
 *
 * ENTITY
 */

import * as exceptions from '../exceptions';
import { strings } from '../util';
import { Validator, ValidateReturn } from '../types';

function clean(input: string): ReturnType<typeof strings.cleanUnicode> {
  // eslint-disable-next-line prefer-const
  let [value, err] = strings.cleanUnicode(input, ' -.');

  if (err !== null) {
    return [value, err];
  }
  if (value.startsWith('BE')) {
    value = value.substr(2);
  }
  if (value.startsWith('(0)')) {
    value = `0${value.substr(3)}`;
  }
  if (value.length === 9) {
    value = `0${value}`;
  }

  return [value, null];
}

const impl: Validator = {
  name: 'Belgian VAT Number',
  localName: 'Ondernemingsnummer',
  abbreviation: 'BTW, NWSt',
  compact(input: string): string {
    const [value, err] = clean(input);

    if (err) {
      throw err;
    }

    return value;
  },

  format(input: string): string {
    const [value] = clean(input);

    return value;
  },

  validate(input: string): ValidateReturn {
    const [value, error] = clean(input);

    if (error) {
      return { isValid: false, error };
    }
    if (value.length !== 10) {
      return { isValid: false, error: new exceptions.InvalidLength() };
    }
    if (!strings.isdigits(value)) {
      return { isValid: false, error: new exceptions.InvalidFormat() };
    }

    const [front, sum] = strings.splitAt(value, -2);

    if (97 - (parseInt(front, 10) % 97) !== parseInt(sum, 10)) {
      return { isValid: false, error: new exceptions.InvalidChecksum() };
    }

    return {
      isValid: true,
      compact: value,
      isIndividual: false,
      isCompany: true,
    };
  },
};

export const { name, localName, abbreviation, validate, format, compact } =
  impl;