add network detection in private key and tests

PrivateKey.js

@@ -1,6 +1,7 @@
 var imports            = require('soop').imports();
 
 var parent = imports.parent || require('./util/VersionedData');
+var networks= imports.networks || require('./networks');
 
 //compressed is true if public key is compressed; false otherwise
 function PrivateKey(version, buf, compressed) {
@@ -61,4 +62,19 @@ PrivateKey.prototype.compressed = function(compressed) {
   }
 };
 
+PrivateKey.prototype.network = function() {
+  var version = this.version();
+
+  var livenet = networks.livenet;
+  var testnet = networks.testnet;
+
+  var answer;
+  if (version === livenet.keySecret)
+    answer = livenet;
+  else if (version === testnet.keySecret)
+    answer = testnet;
+
+  return answer;
+};
+
 module.exports = require('soop')(PrivateKey);

test/test.PrivateKey.js

@@ -29,4 +29,24 @@ describe('PrivateKey', function() {
 
     privkey.as('base58').should.equal('cTpB4YiyKiBcPxnefsDpbnDxFDffjqJob8wGCEDXxgQ7zQoMXJdH');
   });
+
+  it('should be able to detect network from privatekey', function() {
+    var a = new PrivateKey('cMu64LfQqrPC83SjJqde4mZ5jzC48zyeKbUZbTjQdh6pa1h48TdM');
+    a.network().name.should.equal('testnet');
+    var a = new PrivateKey('cS62Ej4SobZnpFQYN1PEEBr2KWf5sgRYYnELtumcG6WVCfxno39V');
+    a.network().name.should.equal('testnet');
+
+    //compress flag = on
+    var a = new PrivateKey('KwHXRTLNWKzxy2NUnnhFtxricC3Dod4Dd3D7RKzVkKDtWrZhuDHs');
+    a.network().name.should.equal('livenet');
+    var a = new PrivateKey('KwaLX8oyJNNCL9tcyYakQHJDTnrPAmZ2M1YK7NhEcT9j55LWqMZz');
+    a.network().name.should.equal('livenet');
+
+    //compress flag = off
+    var a = new PrivateKey('5KS4jw2kT3VoEFUfzgSpX3GVi7qRYkTfwTBU7qxPKyvbGuiVj33');
+    a.network().name.should.equal('livenet');
+    var a = new PrivateKey('5JZsbYcnYN8Dz2YeSLZr6aswrVevedMUSFWxpie6SPpYRb2E4Gi');
+    a.network().name.should.equal('livenet');
+  });
+ 
 });