Support array of preferred ports (#21)

index.js

@@ -1,28 +1,38 @@
 'use strict';
 const net = require('net');
 
-const getPort = options => new Promise((resolve, reject) => {
-	// For backwards compatibility with number-only input
-	// TODO: Remove this in the next major version
-	if (typeof options === 'number') {
-		options = {
-			port: options
-		};
-	}
-
+const isAvailable = options => new Promise((resolve, reject) => {
 	const server = net.createServer();
-
 	server.unref();
 	server.on('error', reject);
-
 	server.listen(options, () => {
-		const port = server.address().port;
+		const {port} = server.address();
 		server.close(() => {
 			resolve(port);
 		});
 	});
 });
 
+const getPort = options => new Promise((resolve, reject) => {
+	// For backwards compatibility with number-only input
+	// TODO: Remove this in the next major version
+	if (typeof options === 'number') {
+		options = {port: options};
+	}
+
+	if (typeof options.port === 'number') {
+		options.port = [options.port];
+	}
+
+	options.port.reduce((seq, port) => {
+		return seq.catch(() => {
+			return isAvailable(Object.assign({}, options, {port}))
+				.then(port => port)
+				.catch(Promise.reject.bind(Promise));
+		});
+	}, Promise.reject()).then(resolve).catch(reject);
+});
+
 module.exports = options => options ?
 	getPort(options).catch(() => getPort(0)) :
 	getPort(0);

readme.md

@@ -21,7 +21,7 @@ getPort().then(port => {
 });
 ```
 
-Optionally, pass in a preferred port:
+To pass in a preferred port:
 
 ```js
 getPort({port: 3000}).then(port => {
@@ -30,6 +30,14 @@ getPort({port: 3000}).then(port => {
 });
 ```
 
+To pass in an array of preferred ports:
+
+```js
+getPort({port: [3000, 3001, 3002]}).then(port => {
+	console.log(port);
+	// Will use any element in the preferred ports array if available, otherwise fall back to a random port
+});
+```
 
 ## API
 
@@ -43,9 +51,9 @@ Type: `Object`
 
 ##### port
 
-Type: `number`
+Type: `number` `number[]`
 
-The preferred port to use.
+A preferred port or an array of preferred ports to use.
 
 ##### host
 

test.js

@@ -54,3 +54,44 @@ test('preferred port given IPv4 host', async t => {
 
 	t.is(port, desiredPort);
 });
+
+test('preferred ports', async t => {
+	const desiredPorts = [9910, 9912, 9913];
+	const port = await m({
+		port: desiredPorts,
+		host: '0.0.0.0'
+	});
+
+	t.is(port, desiredPorts[0]);
+});
+
+test('first port in preferred ports array is unavailable', async t => {
+	const desiredPorts = [9090, 9091];
+
+	const server = net.createServer();
+	await pify(server.listen.bind(server))(desiredPorts[0]);
+
+	const port = await m({
+		port: desiredPorts
+	});
+
+	t.is(port, desiredPorts[1]);
+});
+
+test('all preferred ports in array are unavailable', async t => {
+	const desiredPorts = [9990, 9991];
+
+	const server1 = net.createServer();
+	await pify(server1.listen.bind(server1))(desiredPorts[0]);
+	const server2 = net.createServer();
+	await pify(server2.listen.bind(server2))(desiredPorts[1]);
+
+	const port = await m({
+		port: desiredPorts
+	});
+
+	t.is(typeof port, 'number');
+	t.true(port > 0 && port < 65536);
+	t.not(port, desiredPorts[0]);
+	t.not(port, desiredPorts[1]);
+});