ean13: fix edge case on checksum calculating

src/items/ean/ean.service.ts

@@ -11,7 +11,7 @@ export class EANService {
       .map((d) => parseInt(d, 10))
       .map((d, i) => d * (i % 2 === 0 ? 1 : 3))
       .reduce((s, d) => s + d, 0);
-    while (sum >= 10) {
+    while (sum > 10) {
       sum -= 10;
     }
     return 10 - sum;

src/items/ean/ean.spec.ts

@@ -6,4 +6,13 @@ describe('EANService', () => {
     const sum = eans.calcChecksum('400638133393');
     expect(sum).toBe(1);
   });
+
+  test('always returns num of correct length', () => {
+    const initial = 140000000000n;
+    for (let i = 0; i < 100; i += 1) {
+      const ean = eans.fromID((initial + BigInt(i)).toString(10));
+      if (ean.length !== 13) console.log(ean);
+      expect(ean.length).toBe(13);
+    }
+  });
 });