Use thumbnail image host from process.env

Limit built process.env to keys in src/env.json, which serves as a source for defaults.

src/components/carousel/carousel.jsx

@@ -33,7 +33,7 @@ module.exports = React.createClass({
             <Slider className={'carousel ' + this.props.className} {... this.props.settings}>
                 {this.props.items.map(function (item) {
                     var thumbnailUrl = (
-                        '//cdn2.scratch.mit.edu/get_image/' + item.type + '/' + item.id + '_' +
+                        process.env.IMAGE_HOST + '/get_image/' + item.type + '/' + item.id + '_' +
                         this.typeDimensions[item.type][0] + 'x' + this.typeDimensions[item.type][1] + '.png' +
                         '?v=' + item.thumbnailVersion
                     );

src/env.json

@@ -0,0 +1,3 @@
+{
+    "IMAGE_HOST": "//cdn2.scratch.mit.edu"
+}

webpack.config.js

@@ -1,6 +1,7 @@
 var path = require('path');
 var webpack = require('webpack');
 var routes = require('./server/routes.json');
+var buildEnv = require('./src/env.json');
 
 // Prepare all entry points
 var entry = {
@@ -48,6 +49,12 @@ module.exports = {
         ]
     },
     plugins: [
+        new webpack.DefinePlugin({
+            'process.env': Object.keys(buildEnv).reduce(function (env, key) {
+                env[key] = JSON.stringify(process.env[key] || env[key]);
+                return env;
+            }, buildEnv)
+        }),
         new webpack.optimize.UglifyJsPlugin({
             compress: {
                 warnings: false