Add toUnitAmount and toBaseUnitAmount static helpers and tests

2 files changed, 39 insertions, 0 deletions

diff --git a/src/ts/0x.js.ts b/src/ts/0x.js.ts
index 1cc2d8b44..b71c691d5 100644
--- a/src/ts/0x.js.ts
+++ b/src/ts/0x.js.ts
@@ -50,4 +50,30 @@ export class ZeroEx {
         const salt = randomNumber.times(factor).round();
         return salt;
     }
+    /*
+     * A unit amount is defined as the amount of a token above the specified decimal places (integer part).
+     * E.g: If a currency has 18 decimal places, 1e18 or one quintillion of the currency is equivalent
+     * to 1 unit.
+    */
+    public static toUnitAmount(amount: BigNumber.BigNumber, decimals: number): BigNumber.BigNumber {
+        assert.isBigNumber('amount', amount);
+        assert.isNumber('decimals', decimals);
+
+        const aUnit = new BigNumber(10).pow(decimals);
+        const unit = amount.div(aUnit);
+        return unit;
+    }
+    /*
+     * A baseUnit is defined as the smallest denomination of a token. An amount expressed in baseUnits
+     * is the amount expressed in the smallest denomination.
+     * E.g: 1 unit of a token with 18 decimal places is expressed in baseUnits as 1000000000000000000
+    */
+    public static toBaseUnitAmount(amount: BigNumber.BigNumber, decimals: number): BigNumber.BigNumber {
+        assert.isBigNumber('amount', amount);
+        assert.isNumber('decimals', decimals);
+
+        const unit = new BigNumber(10).pow(decimals);
+        const baseUnitAmount = amount.times(unit);
+        return baseUnitAmount;
+    }
 }
diff --git a/src/ts/globals.d.ts b/src/ts/globals.d.ts
index 659638a1e..974b4b26d 100644
--- a/src/ts/globals.d.ts
+++ b/src/ts/globals.d.ts
@@ -1,3 +1,5 @@
+declare module 'chai-bignumber';
+
 declare type ETHPublicKey = string;
 declare type ETHAddressHex = string;
 declare type ETHAddressBuff = Buffer;
@@ -6,6 +8,17 @@ declare interface Schema {
     id: string;
 }
 
+// HACK: In order to merge the bignumber declaration added by chai-bignumber to the chai Assertion
+// interface we must use `namespace` as the Chai definitelyTyped definition does. Since we otherwise
+// disallow `namespace`, we disable tslint for the following.
+/* tslint:disable */
+declare namespace Chai {
+    interface Assertion {
+        bignumber: Assertion;
+    }
+}
+/* tslint:enable */
+
 declare module 'ethereumjs-util' {
     const toBuffer: (data: string) => Buffer;
     const hashPersonalMessage: (msg: Buffer) => Buffer;