From 28cca74755da3413722663948ceef33902e983e2 Mon Sep 17 00:00:00 2001
From: Lauren Liberda <laura@selfisekai.rocks>
Date: Fri, 23 Jul 2021 18:31:11 +0200
Subject: [PATCH] ean13: fix edge case on checksum calculating

---
 src/items/ean/ean.service.ts | 2 +-
 src/items/ean/ean.spec.ts    | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/items/ean/ean.service.ts b/src/items/ean/ean.service.ts
index 6ad46ee..e0600e9 100644
--- a/src/items/ean/ean.service.ts
+++ b/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;
diff --git a/src/items/ean/ean.spec.ts b/src/items/ean/ean.spec.ts
index 78b25fa..e7b699e 100644
--- a/src/items/ean/ean.spec.ts
+++ b/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);
+    }
+  });
 });