From 2b13d774c17df6f797113bab89cb4406ff40d092 Mon Sep 17 00:00:00 2001
From: Menyin Chang <menyin_chang@hotmail.com>
Date: Wed, 13 May 2026 14:48:14 -0300
Subject: [PATCH 1/3] fix(sv/nit): align check digit logic with Python
 reference implementation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The TypeScript NIT validator diverged from the upstream python-stdnum
implementation in two places, causing valid NITs to be rejected.

1. Old-vs-new NIT branch selection

   The condition used strict equality against the sequential block:

       value.substr(10, 3) === '100'

   The Python reference uses a lexicographic comparison:

       number[10:13] <= '100'

   As a result, any "old" NIT whose sequential block was below '100'
   (i.e. '000'–'099') was being validated with the new-NIT formula and
   incorrectly flagged as InvalidChecksum. Changed to `<= '100'` to
   match.

2. New-NIT check digit edge case

   The formula was:

       (11 - weightedSum(...)) % 10

   The Python equivalent is:

       (-total % 11) % 10

   which, expanded, is `((11 - total % 11) % 11) % 10`. The outer `% 11`
   matters: when the weighted sum is divisible by 11, Python returns 0
   while the TS version returned 1, rejecting otherwise-valid numbers.
   Added the missing `% 11` step.

No changes to weights, length/format/component checks, or the SV-prefix
handling. Verified against the docstring fixture `0614-050707-104-8`.
---
 src/sv/nit.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/sv/nit.ts b/src/sv/nit.ts
index 8e3fce36..238877d0 100644
--- a/src/sv/nit.ts
+++ b/src/sv/nit.ts
@@ -84,7 +84,7 @@ const impl: Validator = {
     let sum;
     const [front, check] = strings.splitAt(value, 13);
 
-    if (value.substr(10, 3) === '100') {
+    if (value.substr(10, 3) <= '100') {
       sum =
         weightedSum(front, {
           weights: [14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2],
@@ -92,11 +92,12 @@ const impl: Validator = {
         }) % 10;
     } else {
       sum =
-        (11 -
+        ((11 -
           weightedSum(front, {
             weights: [2, 7, 6, 5, 4, 3, 2, 7, 6, 5, 4, 3, 2],
             modulus: 11,
           })) %
+          11)%
         10;
     }
 

From f75a72aeabe141b24d9cdc8f4cbf0288b1d3af77 Mon Sep 17 00:00:00 2001
From: Menyin Chang <menyin_chang@hotmail.com>
Date: Wed, 13 May 2026 14:53:49 -0300
Subject: [PATCH 2/3] Update src/sv/nit.ts

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
---
 src/sv/nit.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sv/nit.ts b/src/sv/nit.ts
index 238877d0..e3c62453 100644
--- a/src/sv/nit.ts
+++ b/src/sv/nit.ts
@@ -84,7 +84,7 @@ const impl: Validator = {
     let sum;
     const [front, check] = strings.splitAt(value, 13);
 
-    if (value.substr(10, 3) <= '100') {
+    if (value.slice(10, 13) <= '100') {
       sum =
         weightedSum(front, {
           weights: [14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2],

From 5ab61679599de7ed84cc747209c494e58349f2f2 Mon Sep 17 00:00:00 2001
From: Menyin Chang <menyin_chang@hotmail.com>
Date: Wed, 13 May 2026 14:54:31 -0300
Subject: [PATCH 3/3] Update src/sv/nit.ts

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
---
 src/sv/nit.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sv/nit.ts b/src/sv/nit.ts
index e3c62453..631dfec2 100644
--- a/src/sv/nit.ts
+++ b/src/sv/nit.ts
@@ -97,7 +97,7 @@ const impl: Validator = {
             weights: [2, 7, 6, 5, 4, 3, 2, 7, 6, 5, 4, 3, 2],
             modulus: 11,
           })) %
-          11)%
+          11) %
         10;
     }