parseSignature - fix no args case

Fixes #35

lib/index.js

@@ -76,27 +76,22 @@ function parseNumber (arg) {
   }
 }
 
+// someMethod()
 // someMethod(bytes,uint)
 // someMethod(bytes,uint):(boolean)
-function parseSignature (sig) {
-  var tmp = /^(\w+)\((.+)\)$/.exec(sig)
-  if (tmp.length !== 3) {
+function parseSignature (sigString) {
+  var methodEndIndex = sigString.indexOf('(')
+  if (methodEndIndex === -1) {
     throw new Error('Invalid method signature')
   }
-
-  var args = /^(.+)\):\((.+)$/.exec(tmp[2])
-
-  if (args !== null && args.length === 3) {
-    return {
-      method: tmp[1],
-      args: args[1].split(','),
-      retargs: args[2].split(',')
-    }
-  } else {
-    return {
-      method: tmp[1],
-      args: tmp[2].split(',')
-    }
+  var methodName = sigString.slice(0,methodEndIndex)
+  var allArgs = sigString.slice(methodEndIndex+1,-1)
+  var [ inputArgs, outputArgs ] = allArgs.split(':')
+
+  return {
+    method: methodName,
+    args: (inputArgs ? inputArgs.split(',') : []),
+    retargs: (outputArgs ? outputArgs.split(',') : null),
   }
 }