[Soroban] Add token parsing/formatting functions

src/walletSdk/Utils/soroban.ts

@@ -1,4 +1,5 @@
 import { Operation, StrKey, scValToNative, xdr } from "@stellar/stellar-sdk";
+import BigNumber from "bignumber.js";
 
 import {
   ArgsForTokenInvocation,
@@ -82,3 +83,85 @@ export const getTokenInvocationArgs = (
     ...opArgs,
   };
 };
+
+// Adopted from https://github.com/ethers-io/ethers.js/blob/master/packages/bignumber/src.ts/fixednumber.ts#L27
+/*
+  This function formats an integer amount (e.g. a bigint value which is broadly
+  used in the soroban env) to a stringfied floating amount. This function is
+  basically the counterpart of the 'parseTokenAmount' function below.
+
+  E.g: formatTokenAmount(BigInt(10000001234567), 7) => "1000000.1234567"  
+*/
+export const formatTokenAmount = (
+  amount: bigint | BigNumber | number | string,
+  decimals: number,
+): string => {
+  const bigNumberAmount = new BigNumber(amount.toString());
+
+  let formatted = bigNumberAmount.toString();
+
+  if (decimals > 0) {
+    formatted = bigNumberAmount
+      .shiftedBy(-decimals)
+      .toFixed(decimals)
+      .toString();
+
+    // Trim trailing zeros
+    while (formatted[formatted.length - 1] === "0") {
+      formatted = formatted.substring(0, formatted.length - 1);
+    }
+
+    if (formatted.endsWith(".")) {
+      formatted = formatted.substring(0, formatted.length - 1);
+    }
+  }
+
+  return formatted;
+};
+
+/*
+  This function parses a floating amount to a bigint amount, which is broadly
+  used in the soroban env. This function is basically the counterpart of the
+  'formatTokenAmount' function above.
+
+  E.g: parseTokenAmount("1000000.1234567", 7) => BigInt(10000001234567)
+*/
+export const parseTokenAmount = (
+  amount: string | number | BigNumber | bigint,
+  decimals: number,
+): bigint => {
+  const comps = amount.toString().split(".");
+
+  let whole = comps[0];
+  let fraction = comps[1];
+  if (!whole) {
+    whole = "0";
+  }
+  if (!fraction) {
+    fraction = "0";
+  }
+
+  // Trim trailing zeros
+  while (fraction[fraction.length - 1] === "0") {
+    fraction = fraction.substring(0, fraction.length - 1);
+  }
+
+  // If decimals is 0, we have an empty string for fraction
+  if (fraction === "") {
+    fraction = "0";
+  }
+
+  // Fully pad the string with zeros to get to value
+  while (fraction.length < decimals) {
+    fraction += "0";
+  }
+
+  const wholeValue = new BigNumber(whole);
+  const fractionValue = new BigNumber(fraction);
+
+  // This basically appends the 'whole' and 'fraction' values into
+  // an integer value
+  const parsed = wholeValue.shiftedBy(decimals).plus(fractionValue);
+
+  return BigInt(parsed.toString());
+};

test/soroban.test.ts

@@ -6,8 +6,13 @@ import {
   Transaction,
   TransactionBuilder,
 } from "@stellar/stellar-sdk";
+import BigNumber from "bignumber.js";
 
-import { getTokenInvocationArgs } from "../src/walletSdk/Utils";
+import {
+  formatTokenAmount,
+  getTokenInvocationArgs,
+  parseTokenAmount,
+} from "../src/walletSdk/Utils";
 import { SorobanTokenInterface } from "../src/walletSdk/Types";
 
 const transactions = {
@@ -73,4 +78,42 @@ describe("Soroban Utils", () => {
 
     expect(args).toBe(null);
   });
+
+  it("should format different types of token amount values", () => {
+    const formatted = "1000000.1234567";
+
+    const value1 = BigInt(10000001234567);
+    expect(formatTokenAmount(value1, 7)).toStrictEqual(formatted);
+
+    const value2 = new BigNumber("10000001234567");
+    expect(formatTokenAmount(value2, 7)).toStrictEqual(formatted);
+
+    const value3 = Number("10000001234567");
+    expect(formatTokenAmount(value3, 7)).toStrictEqual(formatted);
+
+    const value4 = 10000001234567;
+    expect(formatTokenAmount(value4, 7)).toStrictEqual(formatted);
+
+    const value5 = "10000001234567";
+    expect(formatTokenAmount(value5, 7)).toStrictEqual(formatted);
+  });
+
+  it("should parse different types of token amount values", () => {
+    const parsed = BigInt(10000001234567);
+
+    const value5 = "1000000.1234567";
+    expect(parseTokenAmount(value5, 7) === parsed).toBeTruthy();
+
+    const value4 = 1000000.1234567;
+    expect(parseTokenAmount(value4, 7) === parsed).toBeTruthy();
+
+    const value3 = Number("1000000.1234567");
+    expect(parseTokenAmount(value3, 7) === parsed).toBeTruthy();
+
+    const value2 = new BigNumber("1000000.1234567");
+    expect(parseTokenAmount(value2, 7) === parsed).toBeTruthy();
+
+    const value1 = BigInt("123");
+    expect(parseTokenAmount(value1, 3) === BigInt(123000)).toBeTruthy();
+  });
 });