feat: support half-written decimal numbers in BigNumberInput

1 files changed, 29 insertions, 0 deletions

diff --git a/packages/instant/src/util/big_number.ts b/packages/instant/src/util/big_number.ts
new file mode 100644
index 000000000..773eb0cb4
--- /dev/null
+++ b/packages/instant/src/util/big_number.ts
@@ -0,0 +1,29 @@
+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 _hasDecimalPeriod: boolean;
+    constructor(bigNumberString: string) {
+        const hasDecimalPeriod = _.endsWith(bigNumberString, '.');
+        let internalString = bigNumberString;
+        if (hasDecimalPeriod) {
+            internalString = bigNumberString.slice(0, bigNumberString.length - 1);
+        }
+        super(internalString);
+        this._hasDecimalPeriod = hasDecimalPeriod;
+    }
+    public toString(): string {
+        const internalString = super.toString();
+        if (this._hasDecimalPeriod) {
+            return `${internalString}.`;
+        }
+        return internalString;
+    }
+}