stdnum/src/dk/cpr.ts

Standard Number Validation

/**
 * CPR (personnummer, the Danish citizen number).
 *
 * The CPR is the national number to identify Danish citizens and is stored in
 * the Det Centrale Personregister (Civil Registration System). The number
 * consists of 10 digits in the format DDMMYY-SSSS where the first part
 * represents the birth date and the second a sequence number. The first digit
 * of the sequence number indicates the century.
 *
 * The numbers used to validate using a checksum but since the sequence numbers
 * ran out this was abandoned in 2007. It is also not possible to use the
 * checksum only for numbers that have a birth date before that because the
 * numbers are also assigned to immigrants.
 *
 * More information:
 *
 * https://en.wikipedia.org/wiki/Personal_identification_number_(Denmark)
 * https://da.wikipedia.org/wiki/CPR-nummer
 * https://cpr.dk/
 */

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

export function getBirthDate(value: string): Date {
  const [dob] = strings.splitAt(value, 6);
  const [day, month, yearStr] = strings.splitAt(dob, 2, 4);

  let year = parseInt(yearStr);

  if ('5678'.includes(value[6]) && year >= 58) {
    year += 1800;
  } else if (
    '0123'.includes(value[6]) ||
    ('49'.includes(value[6]) && year >= 37)
  ) {
    year += 1900;
  } else {
    year += 2000;
  }

  const d = buildDate(String(year), month, day);

  if (d === null || !isValidDate(String(year), month, day)) {
    throw new exceptions.InvalidComponent(
      'The number does not contain valid birth date information.',
    );
  }

  return d;
}

function clean(input: string): ReturnType<typeof strings.cleanUnicode> {
  const [value, err] = strings.cleanUnicode(input, ' -');
  if (err !== null) {
    return [value, err];
  }

  return [value, null];
}

const impl: Validator = {
  name: 'Danish Citizen Number',
  localName: 'Personnummer',
  abbreviation: 'CPR',
  compact(input: string): string {
    const [value, err] = clean(input);

    if (err) {
      throw err;
    }

    return value;
  },

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

    return strings.splitAt(value, 6).join('-');
  },

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

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

    try {
      const date = getBirthDate(value);
      if (!validBirthdate(date)) {
        return {
          isValid: false,
          error: new exceptions.InvalidComponent(
            'The birth date information is valid, but this person has not been born yet.',
          ),
        };
      }
    } catch (err) {
      if (err instanceof exceptions.ValidationError) {
        return {
          isValid: false,
          error: err,
        };
      }
      return {
        isValid: false,
        error: new exceptions.InvalidComponent(String(err)),
      };
    }

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

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