From c62bf0868bf49af43569e5186211c70094fde67c Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Fri, 8 Aug 2025 08:09:42 -0700
Subject: [PATCH] Improve unit conversion.

---
 src/lib/tools.ts    | 73 +++++++++++++++++++++++++++------------------
 test/test.tools.mjs |  2 +-
 2 files changed, 45 insertions(+), 30 deletions(-)

diff --git a/src/lib/tools.ts b/src/lib/tools.ts
index 8bf22bf..4f66a7b 100644
--- a/src/lib/tools.ts
+++ b/src/lib/tools.ts
@@ -21,51 +21,66 @@ type SweepResult = {
 /**
 * Converts a decimal amount of nano from one unit divider to another.
 *
-* @param {bigint|string} amount - Decimal amount to convert
+* @param {(bigint|string)} amount - Decimal amount to convert
 * @param {string} inputUnit - Current denomination
 * @param {string} outputUnit - Desired denomination
 */
-export async function convert (amount: bigint | string, inputUnit: string, outputUnit: string): Promise<string> {
-	if (typeof amount === 'bigint') {
-		amount = amount.toString()
+export async function convert (amount: bigint | string, inputUnit: string, outputUnit: string): Promise<string>
+export async function convert (amount: unknown, inputUnit: unknown, outputUnit: unknown): Promise<string> {
+	if (typeof amount !== 'bigint' && typeof amount !== 'string') {
+		throw new Error('Invalid amount', { cause: typeof amount })
 	}
-	if (typeof amount !== 'string' || amount === '' || !/^[0-9]*\.?[0-9]*$/.test(amount)) {
-		throw new Error('Invalid amount')
+	if (typeof amount === 'string' && !/^[0-9]+\.?[0-9]*$/.test(amount)) {
+		throw new Error('Invalid amount', { cause: amount })
 	}
-	let [i = '', f = ''] = amount.toString().split('.')
-	i = i.replace(/^0*/g, '')
-	f = f.replace(/0*$/g, '')
-
-	inputUnit = inputUnit.toUpperCase()
-	outputUnit = outputUnit.toUpperCase()
-	if (!(inputUnit in UNITS)) {
+	if (typeof inputUnit !== 'string') {
+		throw new TypeError('Invalid input unit', { cause: typeof inputUnit })
+	}
+	if (typeof outputUnit !== 'string') {
+		throw new TypeError('Invalid output unit', { cause: typeof outputUnit })
+	}
+	if (typeof inputUnit !== 'string' || UNITS[inputUnit.toUpperCase()] == null) {
 		throw new Error(`Unknown denomination ${inputUnit}, expected one of the following: ${Object.keys(UNITS)}`)
 	}
-	if (!(outputUnit in UNITS)) {
+	if (typeof outputUnit !== 'string' || UNITS[outputUnit.toUpperCase()] == null) {
 		throw new Error(`Unknown denomination ${outputUnit}, expected one of the following: ${Object.keys(UNITS)}`)
 	}
 
+	let i = '0', f = '0'
+	if (typeof amount === 'bigint') {
+		i = amount.toString()
+	} else {
+		[i, f] = amount.split('.')
+	}
+
 	// convert to raw
-	i = `${i}${f.slice(0, UNITS[inputUnit])}`.padEnd(i.length + UNITS[inputUnit], '0')
-	f = f.slice(UNITS[inputUnit])
-	if (i.length > 39) {
-		throw new Error('Amount exceeds Nano limits')
+	const inUnit = UNITS[inputUnit.toUpperCase()]
+	i = i.padEnd(i.length + inUnit, '0')
+	let int = BigInt(i)
+	if (f != null) {
+		f = f.padEnd(f.length + inUnit, '0')
+		let frac = BigInt(f)
+		const remainder = frac % (10n ** BigInt(inUnit))
+		if (remainder > 0n) {
+			throw new Error('Amount contains fractional raw', { cause: remainder })
+		}
+		frac /= 10n ** BigInt(f.length - inUnit)
+		int += frac
 	}
-	if (i.length < 1) {
-		throw new Error('Amount must be at least 1 raw')
+	if (int > MAX_SUPPLY) {
+		throw new Error('Amount exceeds available supply')
 	}
-	if (f.length > 0) {
-		throw new Error('Amount contains fractional raw')
+	if (int < 1n) {
+		throw new Error('Amount must be at least 1 raw')
 	}
+	i = int.toString().padStart(40, '0')
 
 	// convert to desired denomination
-	if (UNITS[outputUnit] !== 0) {
-		f = i.padStart(40, '0').slice(-UNITS[outputUnit]) + f
-		i = i.slice(0, -UNITS[outputUnit])
-	}
-	i = i.replace(/^0*/g, '') ?? '0'
-	f = f.replace(/0*$/g, '')
-	return `${i}${f ? '.' : ''}${f}`
+	const outUnit = UNITS[outputUnit.toUpperCase()]
+	f = i.slice(40 - outUnit).replace(/0*$/g, '')
+	i = i.slice(0, 40 - outUnit).replace(/^0*/g, '')
+
+	return `${i === '' ? '0' : i}${f === '' ? '' : '.'}${f}`
 }
 
 function hash (data: string | string[], encoding?: 'hex'): Uint8Array<ArrayBuffer>
diff --git a/test/test.tools.mjs b/test/test.tools.mjs
index 5d05c97..1df3913 100644
--- a/test/test.tools.mjs
+++ b/test/test.tools.mjs
@@ -49,7 +49,7 @@ await Promise.all([
 
 		await test('should convert 1 raw to 10^-29 nano', async () => {
 			const result = await Tools.convert('1', 'RAW', 'NANO')
-			assert.equal(result, '.000000000000000000000000000001')
+			assert.equal(result, '0.000000000000000000000000000001')
 		})
 
 		await test('should ignore leading and trailing zeros', async () => {
-- 
2.47.3