Use standard precondition checks

lib/message.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var bitcore = require('bitcore');
+var _ = require('lodash');
 var PrivateKey = bitcore.PrivateKey;
 var PublicKey = bitcore.PublicKey;
 var Address = bitcore.Address;
@@ -9,20 +10,19 @@ var ECDSA = bitcore.crypto.ECDSA;
 var Signature = bitcore.crypto.Signature;
 var sha256sha256 = bitcore.crypto.Hash.sha256sha256;
 var JSUtil = bitcore.util.js;
+var $ = bitcore.util.preconditions;
 
 /**
- * Will construct a new message to sign and verify.
- * 
+ * constructs a new message to sign and verify.
+ *
  * @param {String} message
  * @returns {Message}
  */
 var Message = function Message(message) {
   if (!(this instanceof Message)) {
     return new Message(message);
-  }  
-  if (typeof message !== 'string') {
-    throw new TypeError('First argument should be a string');
   }
+  $.checkArgument(_.isString(message), new TypeError('First argument should be a string'));
   this.message = message;
 
   return this;
@@ -40,9 +40,8 @@ Message.prototype.magicHash = function magicHash() {
 };
 
 Message.prototype._sign = function _sign(privateKey) {
-  if (!(privateKey instanceof PrivateKey)) {
-    throw new TypeError('First argument should be an instance of PrivateKey');
-  }
+  $.checkArgument(privateKey instanceof PrivateKey,
+    new TypeError('First argument should be an instance of PrivateKey'));
   var hash = this.magicHash();
   var ecdsa = new ECDSA();
   ecdsa.hashbuf = hash;
@@ -55,7 +54,7 @@ Message.prototype._sign = function _sign(privateKey) {
 
 /**
  * Will sign a message with a given bitcoin private key.
- * 
+ *
  * @param {PrivateKey} privateKey - An instance of PrivateKey
  * @returns {String} A base64 encoded compact signature
  */
@@ -82,12 +81,18 @@ Message.prototype._verify = function _verify(publicKey, signature) {
 /**
  * Will return a boolean of the signature is valid for a given bitcoin address.
  * If it isn't the specific reason is accessible via the "error" member.
- * 
- * @param {String} bitcoinAddress - A bitcoin address
+ *
+ * @param {Address|String} bitcoinAddress - A bitcoin address
  * @param {String} signatureString - A base64 encoded compact signature
  * @returns {Boolean}
  */
 Message.prototype.verify = function verify(bitcoinAddress, signatureString) {
+  $.checkArgument(bitcoinAddress);
+  $.checkArgument(signatureString && _.isString(signatureString));
+
+  if (_.isString(bitcoinAddress)) {
+    bitcoinAddress = Address.fromString(bitcoinAddress);
+  }
   var signature = Signature.fromCompact(new Buffer(signatureString, 'base64'));
 
   // recover the public key
@@ -96,11 +101,10 @@ Message.prototype.verify = function verify(bitcoinAddress, signatureString) {
   ecdsa.sig = signature;
   var publicKey = ecdsa.toPublicKey();
 
-  var expectedAddress = Address.fromString(bitcoinAddress);
-  var signatureAddress = Address.fromPublicKey(publicKey, expectedAddress.network);
+  var signatureAddress = Address.fromPublicKey(publicKey, bitcoinAddress.network);
 
   // check that the recovered address and specified address match
-  if (expectedAddress.toString() !== signatureAddress.toString()) {
+  if (bitcoinAddress.toString() !== signatureAddress.toString()) {
     this.error = 'The signature did not match the message digest';
     return false;
   }

package.json

@@ -23,7 +23,8 @@
     "url": "https://github.com/bitpay/bitcore-message.git"
   },
   "dependencies": {
-    "bitcore": "^0.9.4"
+    "bitcore": "^0.9.4",
+    "lodash": "^3.1.0"
   },
   "devDependencies": {
     "bitcore-build": "bitpay/bitcore-build",

test/message.js

@@ -26,7 +26,7 @@ describe('Message', function() {
   it('will error with incorrect message type', function() {
     expect(function(){
       return new Message(new Date());
-    }).to.throw(TypeError);
+    }).to.throw('First argument should be a string');
   });
 
   it('will instantiate without "new"', function() {
@@ -49,7 +49,7 @@ describe('Message', function() {
     expect(function(){
       var message3 = new Message(text);
       return message3.sign('not a private key');
-    }).to.throw(TypeError);
+    }).to.throw('First argument should be an instance of PrivateKey');
   });
 
   it('can verify a message with signature', function() {