Modernizing and using flowtype

.babelrc

@@ -1,3 +1,4 @@
 {
-	"presets": ["es2015"]
+  "presets": ["es2015", "flow"],
+  "plugins": [ "transform-object-rest-spread" ]
 }

.flowconfig

@@ -0,0 +1,12 @@
+[ignore]
+
+[include]
+src/
+
+[libs]
+
+[lints]
+
+[options]
+
+[strict]

package.json

@@ -8,6 +8,7 @@
     "url": "git://github.com/Simperium/node-simperium.git"
   },
   "scripts": {
+    "flow": "flow",
     "test": "mocha --compilers js:babel-core/register --require test/helper test/**",
     "prepublish": "babel -q -d lib/ src/"
   },
@@ -21,8 +22,12 @@
     "babel-cli": "^6.2.0",
     "babel-core": "^6.2.0",
     "babel-eslint": "^8.2.1",
-    "babel-preset-es2015": "^6.2.0",
+    "babel-plugin-transform-object-rest-spread": "^6.26.0",
+    "babel-preset-es2015": "^6.24.1",
+    "babel-preset-flow": "^6.23.0",
     "eslint": "^4.17.0",
-    "mocha": "^2.3.4"
+    "flow": "^0.2.3",
+    "flow-bin": "^0.65.0",
+    "mocha": "^2.5.3"
   }
 }

src/simperium/auth.js

@@ -1,67 +1,116 @@
-import { EventEmitter } from 'events'
-import User from './user'
-import { format, inherits } from 'util'
-import https from 'https'
+// @flow
+import events from 'events'
+import { request } from 'https'
 import url from 'url'
 
+// @flow
+type User = {
+	options: {},
+	access_token: string,
+};
+
+const fromJSON = ( json: string ): User => {
+	const data: {} = JSON.parse( json );
+	if ( ! data.access_token && typeof data.access_token !== 'string' ) {
+		throw new Error( 'access_token not present' );
+	}
+	return {
+		options: data,
+		access_token: new String( data.access_token ).toString()
+	};
+};
+
+const { EventEmitter } = events;
+
 const URL = 'https://auth.simperium.com/1';
 
-export default function Auth( appId, appSecret ) {
-	this.appId = appId;
-	this.appSecret = appSecret;
+export class AuthError extends Error {
+	underlyingError: Error
+
+	constructor( underlyingError: Error ) {
+		super( 'Failed to authenticate user.' );
+		this.underlyingError = underlyingError;
+	}
 }
 
-inherits( Auth, EventEmitter );
+/**
+ * Client for creating and authenticating Simperium.com user accounts.
+ */
+export class Auth extends EventEmitter {
+	appId: string
+	appSecret: string
 
-Auth.prototype.authorize = function( username, password ) {
-	var body = JSON.stringify( { username: username, password: password } ),
-		promise = this.request( 'authorize/', body );
+	/**
+	 * Creates an instance of the Auth client
+	 *
+	 * @param {string} appId - Simperium.com application ID
+	 * @param {string} appSecret - Simperium.com application secret
+	 */
+	constructor( appId: string, appSecret: string ) {
+		super();
+		this.appId = appId;
+		this.appSecret = appSecret;
+	}
 
-	return promise;
-}
+	/**
+	 * Authorizes a user account with username and password
+	 *
+	 * @param {string} username account username
+	 * @param {string} password account password
+	 * @returns {Promise<User>} user account data
+	 */
+	authorize( username: string, password: string ) {
+		const body = JSON.stringify( { username: username, password: password } );
+		return this.request( 'authorize/', body );
+	}
 
-Auth.prototype.create = function( username, password, provider ) {
-	var userData = { username, password };
-	if ( provider ) {
-		userData.provider = provider;
+	create( username: String, password: String, provider: ?String ) {
+		const userData: { username: String, password: String, provider?: String } = { username, password };
+		if ( provider ) {
+			userData.provider = provider;
+		}
+		const body = JSON.stringify( userData );
+		return this.request( 'create/', body );
 	}
-	var body = JSON.stringify( userData ),
-	    promise = this.request( 'create/', body );
 
-	return promise;
-}
+	getUrlOptions( path: string ) {
+		const options = url.parse( `${URL}/${ this.appId }/${ path}` );
+		return {
+			... options,
+			method: 'POST',
+			headers: {'X-Simperium-API-Key': this.appSecret }
+		};
+	}
 
-Auth.prototype.getUrlOptions = function( path ) {
-	const options = url.parse( format( '%s/%s/%s', URL, this.appId, path ) );
-	return Object.assign( options, { method: 'POST', headers: {'X-Simperium-API-Key': this.appSecret}} );
-}
+	request( endpoint: string, body: string ): Promise<User> {
+		return new Promise( ( resolve, reject ) => {
+			const req = request( this.getUrlOptions( endpoint ), ( res ) => {
+				let responseData = '';
 
-Auth.prototype.request = function( endpoint, body ) {
-	return new Promise( ( resolve, reject ) => {
-		const req = https.request( this.getUrlOptions( endpoint ), ( res ) => {
-			var responseData = '';
+				res.on( 'data', ( data ) => {
+					responseData += data.toString();
+				} );
 
-			res.on( 'data', ( data ) => {
-				responseData += data.toString();
+				res.on( 'end', () => {
+					try {
+						const user = fromJSON( responseData );
+						resolve( user );
+						this.emit( 'authorize', user );
+					} catch ( error ) {
+						return reject( new AuthError( error ) );
+					}
+				} );
 			} );
 
-			res.on( 'end', () => {
-				var user;
-
-				try {
-					user = User.fromJSON( responseData );
-				} catch ( e ) {
-					return reject( new Error( responseData ) );
-				}
-				this.emit( 'authorize', user );
-				resolve( user );
+			req.on( 'error', ( e ) => {
+				reject( e );
 			} );
-		} );
 
-		req.on( 'error', ( e ) => {
-			reject( e );
+			req.end( body );
 		} );
+	}
+};
 
-		req.end( body );
-	} );
-}
+export default ( appId: string, appSecret: string ) => {
+	return new Auth( appId, appSecret );
+};