feat(pxtorem): add configuration interface and validation for rootValue and unitPrecision

Author: felixicaza

packages/pxtorem/src/contracts/config.type.ts

@@ -0,0 +1,4 @@
+export interface Config {
+  rootValue: number
+  unitPrecision: number
+}

packages/pxtorem/src/index.ts

@@ -1,11 +1,38 @@
 import { type LengthValue, type LengthUnit } from 'lightningcss'
+import { validatePositiveInteger } from './utils/errorHandler'
+import type { Config } from './contracts/config.type'
+
+const defultConfig: Config = {
+  rootValue: 16,
+  unitPrecision: 4
+}
+
+/**
+ * Convert pixel units to rem units.
+ * @param {Object} config - The configuration object.
+ * @param {number} [config.rootValue=16] - The root value for conversion. (default is 16)
+ * @param {number} [config.unitPrecision=4] - The decimal precision for the converted value. (default is 4)
+ * @returns {Function} `Length` function to convert pixel values to rem values used by LightningCSS.
+ */
+function pxtorem(config: Partial<Config> = {}) {
+  const { rootValue, unitPrecision } = { ...defultConfig, ...config }
+
+  validatePositiveInteger(rootValue, 'rootValue')
+  validatePositiveInteger(unitPrecision, 'unitPrecision')
+
+  const toFixed = (value: number, precision: number): number => {
+    const factor = Math.pow(10, precision)
+
+    return Math.round(value * factor) / factor
+  }
 
-export default () => {
   return {
     Length({ unit, value }: LengthValue): { unit: LengthUnit, value: number } | undefined {
       if (unit === 'px') {
-        return { unit: 'rem', value: value / 16 }
+        return { unit: 'rem', value: toFixed(value / rootValue, unitPrecision) }
       }
     }
   }
 }
+
+export default pxtorem

packages/pxtorem/src/utils/errorHandler.ts

@@ -0,0 +1,13 @@
+export function validatePositiveInteger(value: number | undefined, name: string) {
+  if (typeof value !== 'number' || isNaN(value)) {
+    throw new Error(`Invalid ${name}: must be a valid number.`)
+  }
+
+  if (value < 0) {
+    throw new Error(`Invalid ${name}: must not be negative.`)
+  }
+
+  if (!Number.isInteger(value)) {
+    throw new Error(`Invalid ${name}: must not be a decimal.`)
+  }
+}