feat(frontend): validateConvertAmount util

src/frontend/src/lib/utils/convert.utils.ts

@@ -0,0 +1,41 @@
+import { ZERO } from '$lib/constants/app.constants';
+import type { ConvertAmountErrorType } from '$lib/types/convert';
+import { formatToken } from '$lib/utils/format.utils';
+import { isNullish, nonNullish } from '@dfinity/utils';
+import { BigNumber } from '@ethersproject/bignumber';
+import { Utils } from 'alchemy-sdk';
+
+export const validateConvertAmount = ({
+	userAmount,
+	decimals,
+	balance,
+	totalFee
+}: {
+	userAmount: BigNumber;
+	decimals: number;
+	balance?: BigNumber;
+	totalFee?: bigint;
+}): ConvertAmountErrorType => {
+	if (isNullish(totalFee)) {
+		return;
+	}
+	// We should align balance and userAmount to avoid issues caused by comparing formatted and unformatted BN
+	const parsedSendBalance = nonNullish(balance)
+		? Utils.parseUnits(
+				formatToken({
+					value: balance,
+					unitName: decimals,
+					displayDecimals: decimals
+				}),
+				decimals
+			)
+		: ZERO;
+
+	if (userAmount.gt(parsedSendBalance)) {
+		return 'insufficient-funds';
+	}
+
+	if (nonNullish(totalFee) && userAmount.add(totalFee).gt(parsedSendBalance)) {
+		return 'insufficient-funds-for-fee';
+	}
+};

src/frontend/src/tests/lib/utils/convert.utils.spec.ts

@@ -0,0 +1,53 @@
+import { validateConvertAmount } from '$lib/utils/convert.utils';
+import { BigNumber } from 'alchemy-sdk';
+import { describe } from 'vitest';
+
+describe('validateConvertAmount', () => {
+	const userAmount = BigNumber.from(200000n);
+	const decimals = 8;
+	const balance = BigNumber.from(9000000n);
+	const totalFee = 10000n;
+
+	it('should return undefined if all data satisfies the conditions', () => {
+		expect(
+			validateConvertAmount({
+				userAmount,
+				decimals,
+				balance,
+				totalFee
+			})
+		).toBeUndefined();
+	});
+
+	it('should return undefined if totalFee is undefined', () => {
+		expect(
+			validateConvertAmount({
+				userAmount,
+				decimals,
+				balance
+			})
+		).toBeUndefined();
+	});
+
+	it('should return insufficient funds error', () => {
+		expect(
+			validateConvertAmount({
+				userAmount: balance.add(userAmount),
+				decimals,
+				balance,
+				totalFee
+			})
+		).toBe('insufficient-funds');
+	});
+
+	it('should return insufficient funds for fee error', () => {
+		expect(
+			validateConvertAmount({
+				userAmount: balance.sub(BigNumber.from(totalFee).div(2)),
+				decimals,
+				balance,
+				totalFee
+			})
+		).toBe('insufficient-funds-for-fee');
+	});
+});