better mod10

Author: alexanbj

packages/validation/src/no.ts

@@ -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).
@@ -122,7 +122,7 @@ type PersonalIdentityNumberOptions = ValidatorOptions;
  */
 export function validateNationalIdentityNumber(
   value: string,
-  options: PersonalIdentityNumberOptions = {},
+  options: NationalIdentityNumberOptions = {},
 ): boolean {
   if (options.allowFormatting) {
     // biome-ignore lint/style/noParameterAssign:

packages/validation/src/se.ts

@@ -84,7 +84,9 @@ export function validateOrganizationNumber(
   return /^\d{10}$/.test(value);
 }
 
-type PersonalIdentityNumberOptions = ValidatorOptions;
+type NationalIdenityNumberOptions = ValidatorOptions & {
+  format?: ['long', 'short'];
+};
 
 /**
  * Validates that the input value is a Swedish national identity number (personnummer or samordningsnummer).
@@ -102,31 +104,32 @@ type PersonalIdentityNumberOptions = ValidatorOptions;
  */
 export function validateNationalIdentityNumber(
   value: string,
-  options: PersonalIdentityNumberOptions = {},
+  options: NationalIdenityNumberOptions = {},
 ): boolean {
   if (options.allowFormatting) {
     // biome-ignore lint/style/noParameterAssign:
     value = stripFormatting(value);
   }
 
-  const controlDigitCheck = mod10(value);
-  if (!controlDigitCheck) {
-    return false;
-  }
+  // this allows us to handle both YYYYMMDD and YYMMDD when extracting the date
+  const offset = value.length === 12 ? 2 : 0;
 
-  let add = 0;
-  if (value.length === 12) {
-    add = 2;
+  // when verifying the value, we must always use the short format.
+  // because the long format would generate a different checksum
+  const isValid = mod10(offset ? value.substring(2) : value);
+  if (!isValid) {
+    return false;
   }
 
   // copy/inspiration from NAV https://github.com/navikt/fnrvalidator/blob/77e57f0bc8e3570ddc2f0a94558c58d0f7259fe0/src/validator.ts#L108
-  let year = Number(value.substring(0, 2 + add));
-  const month = Number(value.substring(2 + add, 4 + add));
-  let day = Number(value.substring(4 + add, 6 + add));
+  let year = Number(value.substring(0, 2 + offset));
+  const month = Number(value.substring(2 + offset, 4 + offset));
+  let day = Number(value.substring(4 + offset, 6 + offset));
 
   // 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.
-  if (year === 0) {
+  // if (options.format === 'short' && year === 0) {
+  if (value.length === 10 && year === 0) {
     year = 2000;
   }
 

packages/validation/src/utils.ts

@@ -29,15 +29,17 @@ export function mod11(value: string, weights: number[]): boolean {
 
 /**
  * Also known as Luhn's algorithm.
- * Used to validate Swedish national identity numbers.
- * See https://no.wikipedia.org/wiki/MOD10
+ * 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;
 
-  for (let i = 0; i < value.length; ++i) {
-    const weight = 2 - (i % 2);
-
+  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;
@@ -51,6 +53,8 @@ export function mod10(value: string): boolean {
     }
 
     sum += number;
+    // alternate between 1 and 2 for the weight
+    weight = weight === 1 ? 2 : 1;
   }
 
   return sum % 10 === 0;
@@ -66,7 +70,7 @@ export function isValidDate(year: number, month: number, day: number): boolean {
   return (
     date &&
     // cannot do this for Norway
-    // maybe do it for Sweden?
+    // maybe do it for Sweden for long format?
     // date.getUTCFullYear() === year &&
     date.getUTCMonth() === month &&
     date.getUTCDate() === day

packages/validation/src/validation.test.ts

@@ -180,7 +180,17 @@ describe('se', () => {
     expect(se.validateObosMembershipNumber(input, options)).toBe(expected);
   });
 
-  test('validateNationalIdentityNumber() - validates leap years', () => {
+  test('test with leap years', () => {
+    expect(
+      se.validateOrganizationNumber('000229-3017', { allowFormatting: true }),
+    ).toBe(true);
+
+    expect(
+      se.validateOrganizationNumber('000229-5855', { allowFormatting: true }),
+    ).toBe(true);
+  });
+
+  test('validateNationalIdentityNumber() - validates short format personnummer', () => {
     for (let i = 0; i < 1000; ++i) {
       const pnr = swedishPersonNummer({ format: 'short' });
       expect(
@@ -189,4 +199,16 @@ describe('se', () => {
       ).toBe(true);
     }
   });
+
+  // 204101052241
+  // 211802018075
+  // 196304076083
+  test.only('validateNationalIdentityNumber() - validates long format personnummer', () => {
+    for (let i = 0; i < 1000; ++i) {
+      const pnr = swedishPersonNummer({ format: 'long' });
+      expect(se.validateNationalIdentityNumber(pnr), `${pnr} is valid`).toBe(
+        true,
+      );
+    }
+  });
 });