Improve arguments parsing

Doesn't assume callback is always provided (as a last argument). (preliminary for promise support)

spread arguments instead of passing - `findAPortInUse` used to pass its `arguments` object to `findAPortWithStatus` as a single parameter. It's better to actually spread it like arguments naturally do, also makes it easy to extend them.

More verbose for clarity.

lib/portscanner.js

@@ -26,16 +26,20 @@ var async = require('async')
  * // scans 3000 and 3002 only, not 3001.
  * portscanner.findAPortInUse([3000, 3002], console.log)
  */
-function findAPortInUse (params) {
-  findAPortWithStatus('open', arguments)
+function findAPortInUse () {
+  var params = [].slice.call(arguments)
+  params.unshift('open')
+  return findAPortWithStatus.apply(null, params)
 }
 
 /**
  * Finds the first port with a status of 'closed', implying the port is not in
  * use. Accepts identical parameters as {@link findAPortInUse}
  */
-function findAPortNotInUse (params) {
-  findAPortWithStatus('closed', arguments)
+function findAPortNotInUse () {
+  var params = [].slice.call(arguments)
+  params.unshift('closed')
+  return findAPortWithStatus.apply(null, params)
 }
 
 /**
@@ -53,25 +57,33 @@ function findAPortNotInUse (params) {
  * @param {Number} [opts.timeout=400] - Connection timeout in ms.
  * @param {checkPortCallback} callback - Function to call back with error or results.
  */
-function checkPortStatus (port, arg2, arg3) {
-  var options = {}
-  var callback
+function checkPortStatus (port) {
+  var args, host, opts, callback
 
-  if (typeof arg2 === 'string') {
-    // Assume this param is the host option
-    options = { host: arg2 }
+  args = [].slice.call(arguments, 1)
+
+  if (typeof args[0] === 'string') {
+    host = args[0]
+  } else if (typeof args[0] === 'object') {
+    opts = args[0]
+  } else if (typeof args[0] === 'function') {
+    callback = args[0]
+  }
+
+  if (typeof args[1] === 'object') {
+    opts = args[1]
+  } else if (typeof args[1] === 'function') {
+    callback = args[1]
+  }
+
+  if (typeof args[2] === 'function') {
+    callback = args[2]
   }
+  opts = opts || {}
 
-  /**
-   * Callback for {@link checkPortStatus}
-   * @callback checkPortCallback
-   * @param {Error|null} error - Any error that occurred while port scanning, or null.
-   * @param {String} status - Status: 'open' if the port is in use, 'closed' if the port is available.
-   */
-  callback = Array.prototype.slice.call(arguments).slice(-1)[0]
+  host = host || opts.host || '127.0.0.1'
 
-  var host = options.host || '127.0.0.1'
-  var timeout = options.timeout || 400
+  var timeout = opts.timeout || 400
   var connectionRefused = false
 
   var socket = new Socket()
@@ -111,6 +123,12 @@ function checkPortStatus (port, arg2, arg3) {
 
   socket.connect(port, host)
 }
+/**
+ * Callback for {@link checkPortStatus}
+ * @callback checkPortCallback
+ * @param {Error|null} error - Any error that occurred while port scanning, or null.
+ * @param {String} status - Status: 'open' if the port is in use, 'closed' if the port is available.
+ */
 
 /**
  * Internal helper function used by {@link findAPortInUse} and {@link findAPortNotInUse}
@@ -120,36 +138,45 @@ function checkPortStatus (port, arg2, arg3) {
  * @param {String} status - Status to check.
  * @param {...params} params - Params as passed exactly to {@link findAPortInUse} and {@link findAPortNotInUse}.
  */
-function findAPortWithStatus (status, params) {
-  var host, callback
-
-  if (typeof params[0] === 'object') {
-    var ports = params[0]
-    host = typeof params[1] === 'string' ? params[1] : null
-  } else if (typeof params[0] === 'number') {
-    var startPort = params[0]
-    var endPort = params[1]
-    host = typeof params[2] === 'string' ? params[2] : null
+function findAPortWithStatus (status) {
+  var params, startPort, endPort, portList, host, callback
+
+  params = [].slice.call(arguments, 1)
+
+  if (typeof params[0] === 'number') {
+    startPort = params[0]
+  } else if (params[0] instanceof Array) {
+    portList = params[0]
+  }
+
+  if (typeof params[1] === 'number') {
+    endPort = params[1]
+  } else if (typeof params[1] === 'string') {
+    host = params[1]
+  } else if (typeof params[1] === 'function') {
+    callback = params[1]
+  }
+
+  if (typeof params[2] === 'string') {
+    host = params[2]
+  } else if (typeof params[2] === 'function') {
+    callback = params[2]
   }
 
-  /**
-   * Callback for {@link findAPortWithStatus}, and by that extension, for {@link findAPortInUse} and {@link findAPortNotInUse}.
-   * @callback findPortCallback
-   * @param {Error|null} error - Any error that occurred while port scanning, or null.
-   * @param {Number|Boolean} port - The first open port found. Note, this is the first port that returns status as 'open', not necessarily the first open port checked. If no open port is found, the value is false.
-   */
-  callback = Array.prototype.slice.call(params).slice(-1)[0]
+  if (typeof params[3] === 'function') {
+    callback = params[3]
+  }
 
   endPort = endPort || 65535
 
   var foundPort = false
   var numberOfPortsChecked = 0
-  var port = ports ? ports[0] : startPort
+  var port = portList ? portList[0] : startPort
 
   // Returns true if a port with matching status has been found or if checked
   // the entire range of ports
   var hasFoundPort = function () {
-    return foundPort || numberOfPortsChecked === (ports ? ports.length : endPort - startPort + 1)
+    return foundPort || numberOfPortsChecked === (portList ? portList.length : endPort - startPort + 1)
   }
 
   // Checks the status of the port
@@ -160,7 +187,7 @@ function findAPortWithStatus (status, params) {
         foundPort = true
         callback(error)
       } else {
-        port = ports ? ports[numberOfPortsChecked] : port + 1
+        port = portList ? portList[numberOfPortsChecked] : port + 1
         callback(null)
       }
     })
@@ -178,6 +205,12 @@ function findAPortWithStatus (status, params) {
     }
   })
 }
+/**
+ * Callback for {@link findAPortWithStatus}, and by that extension, for {@link findAPortInUse} and {@link findAPortNotInUse}.
+ * @callback findPortCallback
+ * @param {Error|null} error - Any error that occurred while port scanning, or null.
+ * @param {Number|Boolean} port - The first open port found. Note, this is the first port that returns status as 'open', not necessarily the first open port checked. If no open port is found, the value is false.
+ */
 
 /**
  * @exports portscanner