add validation of Swedish national identity number (#33)

Author: alexanbj

packages/validation/README.md

@@ -40,7 +40,6 @@ The methods are "strict" by default, meaning no formatting characters in the inp
 This is preferrable, for instance when doing server-side validation, where the input is often expected to be a "clean" value.
 
 If you want to allow formatting characters in the input, you can pass `allowFormatting: true` in the options object to the method.
-Note that this currently allows any formatting characters, not just the just the "expected" ones for the input type.
 
 
 ```js

packages/validation/package.json

@@ -31,6 +31,7 @@
     "build": "bunchee"
   },
   "devDependencies": {
-    "nav-faker": "3.2.4"
+    "@personnummer/generate": "^1.0.3",
+    "nav-faker": "^3.2.4"
   }
 }

packages/validation/src/no.ts

@@ -1,5 +1,5 @@
 import type { ValidatorOptions } from './types';
-import { mod11, stripFormatting } from './utils';
+import { isValidDate, mod11, stripFormatting } from './utils';
 
 type PostalCodeOptions = ValidatorOptions;
 
@@ -104,7 +104,7 @@ export function validateObosMembershipNumber(
   return /^\d{7}$/.test(value);
 }
 
-type PersonalIdentityNumberOptions = ValidatorOptions;
+type NationalIdentityNumberOptions = ValidatorOptions;
 
 /**
  * Validates that the input value is a Norwegian national identity number (fødselsnummer or d-nummer).
@@ -113,16 +113,12 @@ type PersonalIdentityNumberOptions = ValidatorOptions;
  *
  * @example
  * ```
- * // Fødselsnummer
- * validatePersonalIdentityNumber('21075417753') // => true
- *
- * // D-nummer
- * validatePersonalIdentityNumber('53097248016') // => true
+ * validatePersonalIdentityNumber('DDMMYYXXXXX') // => true
  * ```
  */
 export function validateNationalIdentityNumber(
   value: string,
-  options: PersonalIdentityNumberOptions = {},
+  options: NationalIdentityNumberOptions = {},
 ): boolean {
   if (options.allowFormatting) {
     // biome-ignore lint/style/noParameterAssign:
@@ -161,8 +157,5 @@ export function validateNationalIdentityNumber(
     day = day - 40;
   }
 
-  // important to use UTC so the user's timezone doesn't affect the validation
-  const date = new Date(Date.UTC(year, month - 1, day));
-
-  return date && date.getUTCMonth() === month - 1 && date.getUTCDate() === day;
+  return isValidDate(year, month, day);
 }

packages/validation/src/se.ts

@@ -1,5 +1,5 @@
 import type { ValidatorOptions } from './types';
-import { stripFormatting } from './utils';
+import { isValidDate, mod10, stripFormatting } from './utils';
 
 type PostalCodeOptions = ValidatorOptions;
 
@@ -84,5 +84,101 @@ export function validateOrganizationNumber(
   return /^\d{10}$/.test(value);
 }
 
+type NationalIdentityNumberFormat = 'short' | 'long';
+type NationalIdentityNumberOptions = ValidatorOptions & {
+  /** Specify this if you want to format to be only long (12 digits) or short (10 digits). By default, both formats are allowed */
+  format?: NationalIdentityNumberFormat;
+};
+
+// the first two digts are optional, as they're the century in the long format version
+const PERSONNUMMER_FORMAT = /^(\d{2}){0,1}(\d{2})(\d{2})(\d{2})([+-]?)(\d{4})$/;
+
+/**
+ * Validates that the input value is a Swedish national identity number (personnummer or samordningsnummer).
+ *
+ * It validates the control digits and checks if the date of birth is valid.
+ *
+ * @example
+ * ```
+ * // Short format
+ * validatePersonalIdentityNumber('YYMMDDXXXX') // => true
+ * validatePersonalIdentityNumber('YYMMDD-XXXX', { allowFormatting: true }) // => true
+ *
+ * // Long format
+ * validatePersonalIdentityNumber('YYYYMMDDXXXX') // => true
+ * validatePersonalIdentityNumber('YYYYMMDD-XXXX', { allowFormatting: true }) // => true
+ * ```
+ */
+export function validateNationalIdentityNumber(
+  value: string,
+  options: NationalIdentityNumberOptions = {},
+): boolean {
+  const match = PERSONNUMMER_FORMAT.exec(value);
+
+  if (!match) {
+    return false;
+  }
+
+  const [_, centuryStr, yearStr, monthStr, dayStr, separator, rest] = match;
+
+  if (centuryStr && options.format === 'short') {
+    return false;
+  }
+
+  if (!centuryStr && options.format === 'long') {
+    return false;
+  }
+
+  if (separator && !options.allowFormatting) {
+    return false;
+  }
+
+  // when verifying the value, we must always use the short format, discarding the century
+  // if we include the century it would generate a different checksum
+  const isValid = mod10(`${yearStr}${monthStr}${dayStr}${rest}`);
+  if (!isValid) {
+    return false;
+  }
+
+  let year = 0;
+  switch (true) {
+    // if we have the long format version, we already have the full year
+    case !!centuryStr:
+      year = Number(centuryStr + yearStr);
+      break;
+    // otherwise, we can use the separator to determine the century of the personnummer
+    // if the separator is '+', we know person is over a 100 years old
+    // we can then calculate the full year
+    case !!separator: {
+      const date = new Date();
+      const baseYear =
+        separator === '+' ? date.getUTCFullYear() - 100 : date.getUTCFullYear();
+      year =
+        baseYear - ((baseYear - Number.parseInt(yearStr as string, 10)) % 100);
+      break;
+    }
+    // if it's the short format, without a separator, we need to special handle the year for the date validation.
+    // 1900 isn't a leap year, but 2000 is. Since JS two digits years to the Date constructor is an offset from the year 1900
+    // we need to special handle that case. For other cases it doesn't really matter if the year is 1925 or 2025.
+    case yearStr === '00':
+      year = 2000;
+      break;
+    // short version without separator
+    default:
+      year = Number(yearStr);
+  }
+
+  const month = Number(monthStr);
+
+  let day = Number(dayStr);
+  // for a samordningsnummer the day is increased by 60. Eg the 31st of a month would be 91, or the 3rd would be 63.
+  // thus we need to subtract 60 to get the correct day of the month
+  if (day > 60) {
+    day = day - 60;
+  }
+
+  return isValidDate(year, month, day, Boolean(centuryStr || separator));
+}
+
 // just reexport the no method for API feature parity
 export { validateObosMembershipNumber } from './no';

packages/validation/src/utils.ts

@@ -26,3 +26,59 @@ export function mod11(value: string, weights: number[]): boolean {
 
   return controlNumber === Number(value[value.length - 1]);
 }
+
+/**
+ * Also known as Luhn's algorithm.
+ * Used to validate Swedish national identity numbers and Norwegian KID numbers
+ *
+ * See https://no.wikipedia.org/wiki/MOD10 and https://sv.wikipedia.org/wiki/Luhn-algoritmen#Kontroll_av_nummer
+ */
+export function mod10(value: string): boolean {
+  let sum = 0;
+
+  let weight = 1;
+  // loop in reverse, starting with 1 as the weight for the last digit
+  // which is control digit
+  for (let i = value.length - 1; i >= 0; --i) {
+    let number = Number(value[i]);
+
+    number = weight * number;
+
+    // if the number is greater than 9, ie more than one digit, we reduce it to a single digit by adding the individual digits together
+    // 7 * 2 => 14 => 1 + 4 => 5
+    // instead of adding the digits together, we can subtract 9 for the same result
+    // 7 * 2 => 14 => 14 - 9 => 5
+    if (number > 9) {
+      number = number - 9;
+    }
+
+    sum += number;
+    // alternate between 1 and 2 for the weight
+    weight = weight === 1 ? 2 : 1;
+  }
+
+  return sum % 10 === 0;
+}
+
+export function isValidDate(
+  year: number,
+  month: number,
+  day: number,
+  /** Whether to check the year as part of the date validation. */
+  validateYear = false,
+): boolean {
+  // biome-ignore lint/style/noParameterAssign: months are zero index 🤷‍♂️
+  month -= 1;
+
+  // important to use UTC so the user's timezone doesn't affect the validation
+  const date = new Date(Date.UTC(year, month, day));
+
+  const validYear = validateYear ? date.getUTCFullYear() === year : true;
+
+  return (
+    date &&
+    validYear &&
+    date.getUTCMonth() === month &&
+    date.getUTCDate() === day
+  );
+}

packages/validation/src/validation.test.ts

@@ -1,3 +1,4 @@
+import swedishPersonNummer from '@personnummer/generate';
 import navfaker from 'nav-faker/dist/index';
 import { describe, expect, test } from 'vitest';
 import * as no from './no';
@@ -178,4 +179,87 @@ describe('se', () => {
   ])('validateObosMembershipNumber(%s) -> %s', (input, expected, options) => {
     expect(se.validateObosMembershipNumber(input, options)).toBe(expected);
   });
+
+  test('validateNationalIdentityNumber() - validates short format (YYMMDDXXXX) personnummer', () => {
+    for (let i = 0; i < 1000; ++i) {
+      const pnrWithSeparator = swedishPersonNummer({ format: 'short' });
+      const pnrWithoutSeparator = pnrWithSeparator.replace(/[-+]/, '');
+
+      expect(
+        se.validateNationalIdentityNumber(pnrWithSeparator, {
+          allowFormatting: true,
+          format: 'short',
+        }),
+        `${pnrWithSeparator} is valid with separator`,
+      ).toBe(true);
+
+      expect(
+        se.validateNationalIdentityNumber(pnrWithoutSeparator, {
+          format: 'short',
+        }),
+        `${pnrWithSeparator} is valid without separator`,
+      ).toBe(true);
+    }
+  });
+
+  test('validateNationalIdentityNumber() - validates long format (YYYYMMDDXXXX) personnummer', () => {
+    for (let i = 0; i < 1000; ++i) {
+      const pnr = swedishPersonNummer({ format: 'long' });
+
+      expect(
+        se.validateNationalIdentityNumber(pnr, { format: 'long' }),
+        `${pnr} is valid`,
+      ).toBe(true);
+    }
+  });
+
+  test('validateNationalIdentityNumber() - handles separator/leap years', () => {
+    // 29th of February is the best way to test whether the separator and long/short handling works correctly.
+    // The 29th of February year 2000 is valid a valid date, while the 29th of February year 1900 is not.
+    // That means we get different results based on the separator.
+    expect(se.validateNationalIdentityNumber('0002297422')).toBe(true);
+    expect(
+      se.validateNationalIdentityNumber('000229-7422', {
+        allowFormatting: true,
+      }),
+    ).toBe(true);
+
+    expect(
+      se.validateNationalIdentityNumber('000229+7422', {
+        allowFormatting: true,
+      }),
+    ).toBe(false);
+
+    expect(se.validateNationalIdentityNumber('190002297422')).toBe(false);
+  });
+
+  test('validateNationalIdentityNumber() - validates samordningsnummer', () => {
+    expect(
+      se.validateNationalIdentityNumber('701063-2391', {
+        allowFormatting: true,
+      }),
+    ).toBe(true);
+  });
+
+  test('validateNationalIdentityNumber() - respects format modifier', () => {
+    expect(
+      se.validateNationalIdentityNumber(
+        swedishPersonNummer({ format: 'short' }),
+        {
+          allowFormatting: true,
+          format: 'long',
+        },
+      ),
+    ).toBe(false);
+
+    expect(
+      se.validateNationalIdentityNumber(
+        swedishPersonNummer({ format: 'long' }),
+        {
+          allowFormatting: true,
+          format: 'short',
+        },
+      ),
+    ).toBe(false);
+  });
 });