From f7f659ddc3fd22bd446878af6fd0cdb7ee221165 Mon Sep 17 00:00:00 2001
From: Emma Hamilton <git@emmas.town>
Date: Fri, 13 Sep 2024 13:56:37 +1000
Subject: [PATCH] Remove decimal.js-light dependency (#1309)

---
 .changeset/fast-eagles-change.md              |  5 ++++
 packages/keystatic/package.json               |  1 -
 .../src/form/fields/number/isAtStep.test.ts   | 28 +++++++++++++++++++
 .../src/form/fields/number/validateNumber.tsx | 20 +++++++++++--
 pnpm-lock.yaml                                |  7 -----
 5 files changed, 50 insertions(+), 11 deletions(-)
 create mode 100644 .changeset/fast-eagles-change.md
 create mode 100644 packages/keystatic/src/form/fields/number/isAtStep.test.ts

diff --git a/.changeset/fast-eagles-change.md b/.changeset/fast-eagles-change.md
new file mode 100644
index 000000000..012d58385
--- /dev/null
+++ b/.changeset/fast-eagles-change.md
@@ -0,0 +1,5 @@
+---
+'@keystatic/core': patch
+---
+
+Remove unnecessary dependency
diff --git a/packages/keystatic/package.json b/packages/keystatic/package.json
index 5597ea964..348307f5c 100644
--- a/packages/keystatic/package.json
+++ b/packages/keystatic/package.json
@@ -141,7 +141,6 @@
     "@urql/exchange-graphcache": "^7.1.2",
     "@urql/exchange-persisted": "^4.3.0",
     "cookie": "^0.5.0",
-    "decimal.js-light": "^2.5.1",
     "emery": "^1.4.1",
     "escape-string-regexp": "^4.0.0",
     "fast-deep-equal": "^3.1.3",
diff --git a/packages/keystatic/src/form/fields/number/isAtStep.test.ts b/packages/keystatic/src/form/fields/number/isAtStep.test.ts
new file mode 100644
index 000000000..f004e8981
--- /dev/null
+++ b/packages/keystatic/src/form/fields/number/isAtStep.test.ts
@@ -0,0 +1,28 @@
+import { isAtStep } from './validateNumber';
+import { test, expect } from '@jest/globals';
+
+for (const [value, step] of [
+  [5, 1],
+  [5, 0.1],
+  [5, 0.5],
+  [5, 5e-3],
+  [5.1, 0.1],
+  [5.1, 1e-6],
+  [5.1, 1e-7],
+  [5.1, 1e-200],
+  [300, 3e-200],
+]) {
+  test(`value: ${value}, step: ${step} should be true`, () => {
+    expect(isAtStep(value, step)).toBe(true);
+  });
+}
+
+for (const [value, step] of [
+  [5.1, 1],
+  [5.1, 0.5],
+  [5.1, 3e-200],
+]) {
+  test(`value: ${value}, step: ${step} should be false`, () => {
+    expect(isAtStep(value, step)).toBe(false);
+  });
+}
diff --git a/packages/keystatic/src/form/fields/number/validateNumber.tsx b/packages/keystatic/src/form/fields/number/validateNumber.tsx
index 09afd036b..7bb075f18 100644
--- a/packages/keystatic/src/form/fields/number/validateNumber.tsx
+++ b/packages/keystatic/src/form/fields/number/validateNumber.tsx
@@ -1,5 +1,3 @@
-import Decimal from 'decimal.js-light';
-
 export function validateNumber(
   validation:
     | {
@@ -31,9 +29,25 @@ export function validateNumber(
     if (
       step !== undefined &&
       validation?.validateStep !== undefined &&
-      new Decimal(value).mod(new Decimal(step)).toNumber() !== 0
+      !isAtStep(value, step)
     ) {
       return `${label} must be a multiple of ${step}`;
     }
   }
 }
+
+function decimalPlaces(value: number) {
+  const stringified = value.toString();
+  const indexOfDecimal = stringified.indexOf('.');
+  if (indexOfDecimal === -1) {
+    const indexOfE = stringified.indexOf('e-');
+    return indexOfE === -1 ? 0 : parseInt(stringified.slice(indexOfE + 2));
+  }
+  return stringified.length - indexOfDecimal - 1;
+}
+
+export function isAtStep(value: number, step: number) {
+  const dc = Math.max(decimalPlaces(step), decimalPlaces(value));
+  const base = Math.pow(10, dc);
+  return (value * base) % (step * base) === 0;
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index afd1f22ed..bbab4bf2b 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1204,9 +1204,6 @@ importers:
       cookie:
         specifier: ^0.5.0
         version: 0.5.0
-      decimal.js-light:
-        specifier: ^2.5.1
-        version: 2.5.1
       emery:
         specifier: ^1.4.1
         version: 1.4.2
@@ -15097,10 +15094,6 @@ packages:
     engines: {node: '>=0.10.0'}
     dev: false
 
-  /decimal.js-light@2.5.1:
-    resolution: {integrity: sha512-qIMFpTMZmny+MMIitAB6D7iVPEorVw6YQRWkvarTkT4tBeSLLiHzcwj6q0MmYSFCiVpiqPJTJEYIrpcPzVEIvg==}
-    dev: false
-
   /decimal.js@10.4.3:
     resolution: {integrity: sha512-VBBaLc1MgL5XpzgIP7ny5Z6Nx3UrRkIViUkPUdtl9aya5amy3De1gsUUSB1g3+3sExYNjCAsAznmukyxCb1GRA==}
     dev: false