Merge pull request #474 from Concordium/fix-token-amount-parsing

Fix token amount parsing

Author: DOBEN

packages/sdk/CHANGELOG.md

@@ -49,6 +49,10 @@
 
 ## 10.0.0-alpha.? (Unreleased)
 
+### Fixed
+
+- Fix conversion in `TokenAmount.fromDecimals` function when used with large `tokenAmount` values with small `decimal` values.
+
 ## 10.0.0-alpha.15
 
 ### Fixed

packages/sdk/src/plt/TokenAmount.ts

@@ -146,6 +146,18 @@ export function instanceOf(value: unknown): value is TokenAmount {
     return value instanceof TokenAmount;
 }
 
+/**
+ * Get decimal places from a Big {@linkcode Big}.
+ *
+ * @param big The number to get the decimal places.
+ * @returns {number} The number of decimal places in above number.
+ */
+function getDecimalPlaces(big: Big): number {
+    // `b.c` is an array of single digits (coefficient), `b.e` is the exponent (0-based index of highest digit)
+    const decimals = big.c.length - (big.e + 1);
+    return decimals > 0 ? decimals : 0;
+}
+
 /**
  * Creates a TokenAmount from a number, string, {@linkcode Big}, or bigint.
  *
@@ -163,8 +175,7 @@ export function fromDecimal(amount: BigSource | bigint, decimals: number): Token
     }
 
     const bigAmount = Big(parsed);
-    const parsedDecimals = bigAmount.toString().split('.')[1]?.length ?? 0;
-
+    const parsedDecimals = getDecimalPlaces(bigAmount);
     if (parsedDecimals > decimals) {
         throw new Error('The amount has more decimal places than the specified decimals.');
     }

packages/sdk/test/ci/plt/TokenAmount.test.ts

@@ -12,6 +12,7 @@ describe('PLT TokenAmount', () => {
         expect(TokenAmount.fromDecimal('15.002456687544126548', 18)).toEqual(
             TokenAmount.create(15002456687544126548n, 18)
         );
+        expect(TokenAmount.fromDecimal(MAX_U64, 0)).toEqual(TokenAmount.create(MAX_U64, 0));
     });
 
     test('Parses large decimal values correctly', () => {
@@ -26,7 +27,21 @@ describe('PLT TokenAmount', () => {
 
     test('Token amounts with invalid values throws', () => {
         expect(() => TokenAmount.create(-504n, 0)).toThrow(TokenAmount.Err.negative());
+        expect(() => TokenAmount.create(-504n, 1)).toThrow(TokenAmount.Err.negative());
+        expect(() => TokenAmount.fromDecimal(-504n, 0)).toThrow(TokenAmount.Err.negative());
+        expect(() => TokenAmount.fromDecimal(-504n, 1)).toThrow(TokenAmount.Err.negative());
         expect(() => TokenAmount.create(MAX_U64 + 1n, 0)).toThrow(TokenAmount.Err.exceedsMaxValue());
+        expect(() => TokenAmount.create(99999999999999999999999999n, 1)).toThrow(TokenAmount.Err.exceedsMaxValue());
+        expect(() => TokenAmount.fromDecimal(MAX_U64 + 1n, 0)).toThrow(TokenAmount.Err.exceedsMaxValue());
+        expect(() => TokenAmount.fromDecimal(99999999999999999999999999n, 1)).toThrow(
+            TokenAmount.Err.exceedsMaxValue()
+        );
+    });
+
+    test('Token amounts with more decimals than specified throws', () => {
+        expect(() => TokenAmount.fromDecimal('1.000003', 0)).toThrow(
+            'The amount has more decimal places than the specified decimals.'
+        );
     });
 
     test('Returns expected amount', () => {