From 746432c3cc534213cd15347a8bc98eee0bdbfdc5 Mon Sep 17 00:00:00 2001
From: dev-rb <43100342+dev-rb@users.noreply.github.com>
Date: Sat, 24 Aug 2024 20:55:30 -0400
Subject: [PATCH] fix(number-field): precision handling with floating point
 offsets and value snapping (#468)

---
 .../src/number-field/number-field-root.tsx    | 65 +++++++++++++++++--
 packages/utils/src/number.ts                  | 11 ++++
 2 files changed, 71 insertions(+), 5 deletions(-)

diff --git a/packages/core/src/number-field/number-field-root.tsx b/packages/core/src/number-field/number-field-root.tsx
index de3b68b0..fcb5de71 100644
--- a/packages/core/src/number-field/number-field-root.tsx
+++ b/packages/core/src/number-field/number-field-root.tsx
@@ -2,8 +2,10 @@ import {
 	type ValidationState,
 	access,
 	createGenerateId,
+	getPrecision,
 	mergeDefaultProps,
 	mergeRefs,
+	snapValueToStep,
 } from "@kobalte/utils";
 import {
 	type JSX,
@@ -308,11 +310,33 @@ export function NumberFieldRoot<T extends ValidComponent = "div">(
 			batch(() => {
 				let newValue = rawValue;
 
-				if (rawValue % 1 === 0) {
-					newValue += offset;
-				} else {
-					if (offset > 0) newValue = Math.ceil(newValue);
-					else newValue = Math.floor(newValue);
+				const operation = offset > 0 ? "+" : "-";
+				const localStep = Math.abs(offset);
+				// If there was no min or max provided, don't use our default values
+				// use NaN instead to help with the calculation which will use 0
+				// instead for a NaN value
+				const min =
+					props.minValue === undefined ? Number.NaN : context.minValue();
+				const max =
+					props.maxValue === undefined ? Number.NaN : context.maxValue();
+
+				// Try to snap the value to the nearest step
+				newValue = snapValueToStep(rawValue, min, max, localStep);
+
+				// If the value didn't change in the direction we wanted to,
+				// then add the step and snap that value
+				if (
+					!(
+						(operation === "+" && newValue > rawValue) ||
+						(operation === "-" && newValue < rawValue)
+					)
+				) {
+					newValue = snapValueToStep(
+						handleDecimalOperation(operation, rawValue, localStep),
+						min,
+						max,
+						localStep,
+					);
 				}
 
 				context.setValue(newValue);
@@ -352,3 +376,34 @@ export function NumberFieldRoot<T extends ValidComponent = "div">(
 		</FormControlContext.Provider>
 	);
 }
+
+function handleDecimalOperation(
+	operator: "-" | "+",
+	value1: number,
+	value2: number,
+): number {
+	let result = operator === "+" ? value1 + value2 : value1 - value2;
+	if (
+		Number.isFinite(value1) &&
+		Number.isFinite(value2) &&
+		(value2 % 1 !== 0 || value1 % 1 !== 0)
+	) {
+		const offsetPrecision = getPrecision(value2);
+		const valuePrecision = getPrecision(value1);
+
+		const multiplier = 10 ** Math.max(offsetPrecision, valuePrecision);
+
+		const multipliedOffset = Math.round(value2 * multiplier);
+		const multipliedValue = Math.round(value1 * multiplier);
+
+		const next =
+			operator === "+"
+				? multipliedValue + multipliedOffset
+				: multipliedValue - multipliedOffset;
+
+		// Undo multiplier to get the new value
+		result = next / multiplier;
+	}
+
+	return result;
+}
diff --git a/packages/utils/src/number.ts b/packages/utils/src/number.ts
index 9b777147..4646fd15 100644
--- a/packages/utils/src/number.ts
+++ b/packages/utils/src/number.ts
@@ -51,3 +51,14 @@ export function snapValueToStep(
 
 	return snappedValue;
 }
+
+export const getPrecision = (n: number) => {
+	let e = 1;
+	let precision = 0;
+	while (Math.round(n * e) / e !== n) {
+		e *= 10;
+		precision++;
+	}
+
+	return precision;
+};