Support preview API (#85)

Adds a `preview` boolean option that will switch the host to pull from the preview API

Author: bechatman

.env

@@ -1,2 +1,3 @@
 accessToken=b4c0n73n7fu1
 spaceId=cfexampleapi
+previewToken=e5e8d4c5c122cf28fc1af3ff77d28bef78a3952957f15067bbc29f2f0dde0b50

.gitignore

@@ -1,3 +1,5 @@
 node_modules
 .DS_Store
 .nyc_output
+test/fixtures/error/public/*
+test/fixtures/template/public/*

README.md

@@ -171,6 +171,46 @@ Your template must use the `item` variable as seen below. Also note that this fe
 <p>{{item.title}}</p>
 ```
 
+### Preview Environment
+
+Using [Spike Environments](https://spike.readme.io/docs/environments), you can change your default `app.js` to use [Contentful's preview API](https://www.contentful.com/developers/docs/references/content-preview-api/) by using your project's preview key (in this example, `yyy`).
+
+```js
+new Contentful({
+  addDataTo: locals,
+  accessToken: 'yyy',
+  preview: true;
+  spaceId: 'xxx'
+})
+```
+
+Then set your `app.production.js` to:
+
+```js
+new Contentful({
+  addDataTo: locals,
+  accessToken: 'xxx',
+  preview: false;
+  spaceId: 'xxx'
+})
+```
+From there, running `spike compile` will use the preview API, and `spike compile -e production` will use the regular content delivery API.
+
+This can also be accomplished with a single `app.js` with the help of [Dotenv](https://www.npmjs.com/package/dotenv).
+
+Require Dotenv in your `app.js` file, then modify the Contentful call to use your preview key (in this example, `yyy`).
+
+```js
+const env = process.env.SPIKE_ENV;
+
+new Contentful({
+  addDataTo: locals,
+  accessToken: env !== 'production' ? 'yyy' : 'xxx' ,
+  preview: env !== 'production';
+  spaceId: 'xxx'
+})
+```
+
 ### JSON Output
 
 Finally, if you'd like to have the output written locally to a JSON file so that it's cached locally, you can pass the name of the file, resolved relative to your project's output, as a `json` option to the plugin. For example:

lib/index.js

@@ -19,7 +19,8 @@ class Contentful {
     // initialize the contentful api client
     this.client = contentful.createClient({
       accessToken: this.accessToken,
-      space: this.spaceId
+      space: this.spaceId,
+      host: this.preview ? 'preview.contentful.com' : ''
     })
     bindAllClass(this, ['apply', 'run'])
   }
@@ -128,6 +129,7 @@ function validate(opts = {}) {
   const schema = Joi.object().keys({
     accessToken: Joi.string().required(),
     spaceId: Joi.string().required(),
+    preview: Joi.boolean(),
     addDataTo: Joi.object().required(),
     json: Joi.string(),
     includeLevel: Joi.number().default(1),

test/index.js

@@ -138,6 +138,32 @@ test.cb('returns valid content', t => {
   })
 })
 
+test.cb('returns valid preview content', (t) => {
+  const locals = {}
+  const api = new Contentful({
+    accessToken: process.env.previewToken,
+    spaceId: process.env.spaceId,
+    preview: true,
+    addDataTo: locals,
+    contentTypes: [
+      {
+        name: 'cats',
+        id: 'cat'
+      },
+      {
+        name: 'dogs',
+        id: 'dog'
+      }
+    ]
+  })
+
+  api.run(undefined, () => {
+    t.is(locals.contentful.dogs.length, 2)
+    t.is(locals.contentful.cats.length, 3)
+    t.end()
+  })
+})
+
 test.cb('defaults id to name if not present', t => {
   const locals = {}
   const api = new Contentful({