Add assertions library and add them for all function args

2 files changed, 37 insertions, 0 deletions

diff --git a/src/ts/0x.js.ts b/src/ts/0x.js.ts
index dd67c49a0..acbdd01e2 100644
--- a/src/ts/0x.js.ts
+++ b/src/ts/0x.js.ts
@@ -1,4 +1,6 @@
+import * as BigNumber from 'bignumber.js';
 import * as ethUtil from 'ethereumjs-util';
+import {assert} from './utils/assert';
 
 /**
  * Elliptic Curve signature
@@ -15,6 +17,10 @@ export class ZeroEx {
      * by signing `data` with the private key corresponding to the `signer` address.
      */
     public static isValidSignature(data: string, signature: ECSignature, signer: ETHAddressHex): boolean {
+        assert.isString('data', data);
+        assert.isObject('signature', signature);
+        assert.isETHAddressHex('signer', signer);
+
         const dataBuff = ethUtil.toBuffer(data);
         const msgHashBuff = ethUtil.hashPersonalMessage(dataBuff);
         try {
diff --git a/src/ts/utils/assert.ts b/src/ts/utils/assert.ts
new file mode 100644
index 000000000..a29ae922d
--- /dev/null
+++ b/src/ts/utils/assert.ts
@@ -0,0 +1,31 @@
+import * as _ from 'lodash';
+import * as BigNumber from 'bignumber.js';
+import Web3 = require('web3');
+
+export const assert = {
+    isBigNumber(variableName: string, value: BigNumber.BigNumber) {
+        const isBigNumber = _.isObject(value) && value.isBigNumber;
+        this.assert(isBigNumber, this.typeAssertionMessage(variableName, 'BigNumber', value));
+    },
+    isString(variableName: string, value: string) {
+        this.assert(_.isString(value), this.typeAssertionMessage(variableName, 'string', value));
+    },
+    isETHAddressHex(variableName: string, value: ETHAddressHex) {
+        const web3 = new Web3();
+        this.assert(web3.isAddress(value), this.typeAssertionMessage(variableName, 'ETHAddressHex', value));
+    },
+    isObject(variableName: string, value: object) {
+        this.assert(_.isObject(value), this.typeAssertionMessage(variableName, 'object', value));
+    },
+    isNumber(variableName: string, value: number) {
+        this.assert(_.isFinite(value), this.typeAssertionMessage(variableName, 'number', value));
+    },
+    assert(condition: boolean, message: string) {
+        if (!condition) {
+            throw new Error(message);
+        }
+    },
+    typeAssertionMessage(variableName: string, type: string, value: any) {
+        return `Expected ${variableName} to be of type ${type}, encountered: ${value}`;
+    },
+};