more code cleanup, and another async/await example

docs/images/photos/credits.md

@@ -0,0 +1,2 @@
+Credit: [By Brickset](https://www.flickr.com/photos/brickset/19522560551/in/gallery-ryanthescooterguy-72157651051047402/)
+Credit: [By Sonja](https://www.flickr.com/photos/8308527@N02/5650500453/)

src/auth.callbacks.js

@@ -1,6 +1,6 @@
 // EXAMPLE: CALLBACKS
 const {hashString}     = require('./lib/crypto')
-const {auditLog}       = require('./lib/log')
+const {logEvent}       = require('./lib/log')
 const {getModels}      = require('./lib/db')
 
 function auth(username, password, callback) {
@@ -13,13 +13,13 @@ function auth(username, password, callback) {
     const {users} = models
     hashString(password, function _hashed(err, hash) {
       if (err) return callback(err)
-      users.findOne({username, password: hash}, function _find(err, results) {
+      users.findOne({username, password: hash}, function _find(err, user) {
         if (err) return callback(err)
-        if (!results) {
+        if (!user) {
           return callback(new Error('No users matched. Login failed'))
         }
-        auditLog({event: 'login', username}, function _noOp() {/* do nothing */})
-        callback(null, results)
+        logEvent({event: 'login', username}, function _noOp() {/* do nothing */})
+        callback(null, user)
       })
     })
   })

src/auth.fp.await.js

@@ -0,0 +1,32 @@
+// EXAMPLE: FUNCTIONAL PROMISES
+const Promise           = require('bluebird')
+const {hashString}      = require('./lib/crypto')
+const {logEventAsync}   = require('./lib/log')
+const {getModel}        = require('./lib/db')
+
+module.exports = {auth}
+
+async function auth({username, password}) {
+  if (_isInputValid({username, password})) {
+    logEventAsync({event: 'login', username})()
+    const user = await _loginUser({username, password})
+    if (user && user._id) {
+      return user
+    }
+    throw new Error('User Not found!')
+  }
+}
+
+async function _loginUser({username, password}) {
+  let query = {
+    username,
+    password: await hashString(password)
+  }
+  return await getModel('users').findOneAsync(query)
+}
+
+function _isInputValid({username, password}) {
+  if (!username || username.length < 1) throw new Error('Invalid username.')
+  if (!password || password.length < 6) throw new Error('Invalid password.')
+  return {username, password}
+}