2 files changed, 25 insertions, 34 deletions
diff --git a/packages/instant/src/util/big_number_input.ts b/packages/instant/src/util/big_number_input.ts
deleted file mode 100644
index 370d91a0a..000000000
--- a/packages/instant/src/util/big_number_input.ts
+++ /dev/null
@@ -1,34 +0,0 @@
-import { BigNumber } from '@0x/utils';
-import * as _ from 'lodash';
-
-/**
- *  A BigNumber extension that is more flexible about decimal strings.
- *  Such as allowing:
- *  new BigNumberInput('0.') => 0
- *  new BigNumberInput('1.') => 1
- *  new BigNumberInput('1..') => still throws
- */
-export class BigNumberInput extends BigNumber {
-    private readonly _isEndingWithDecimal: boolean;
-    constructor(numberOrString: string | number) {
-        if (_.isString(numberOrString)) {
-            const hasDecimalPeriod = _.endsWith(numberOrString, '.');
-            let internalString = numberOrString;
-            if (hasDecimalPeriod) {
-                internalString = numberOrString.slice(0, -1);
-            }
-            super(internalString);
-            this._isEndingWithDecimal = hasDecimalPeriod;
-        } else {
-            super(numberOrString);
-            this._isEndingWithDecimal = false;
-        }
-    }
-    public toDisplayString(): string {
-        const internalString = super.toString();
-        if (this._isEndingWithDecimal) {
-            return `${internalString}.`;
-        }
-        return internalString;
-    }
-}
diff --git a/packages/instant/src/util/maybe_big_number.ts b/packages/instant/src/util/maybe_big_number.ts
new file mode 100644
index 000000000..113ba552f
--- /dev/null
+++ b/packages/instant/src/util/maybe_big_number.ts
@@ -0,0 +1,25 @@
+import { BigNumber } from '@0x/utils';
+import * as _ from 'lodash';
+
+import { MaybeBigNumber } from '../types';
+
+export const maybeBigNumberUtil = {
+    // converts a string to a MaybeBigNumber
+    // if string is a NaN, considered undefined
+    stringToMaybeBigNumber: (stringValue: string): MaybeBigNumber => {
+        let validBigNumber: BigNumber;
+        try {
+            validBigNumber = new BigNumber(stringValue);
+        } catch {
+            return undefined;
+        }
+
+        return validBigNumber.isNaN() ? undefined : validBigNumber;
+    },
+    areMaybeBigNumbersEqual: (val1: MaybeBigNumber, val2: MaybeBigNumber): boolean => {
+        if (!_.isUndefined(val1) && !_.isUndefined(val2)) {
+            return val1.equals(val2);
+        }
+        return _.isUndefined(val1) && _.isUndefined(val2);
+    },
+};