Beginning work on asset downloads

app/assets/js/assetdownload.js

@@ -0,0 +1,43 @@
+const fs = require('fs')
+const request = require('request')
+const path = require('path')
+var mkpath = require('mkdirp');
+
+function Asset(from, to, size){
+    this.from = from
+    this.to = to
+    this.size = size
+}
+
+exports.getMojangAssets = function(version, basePath){
+    const name = version + '.json'
+    const indexURL = 'https://s3.amazonaws.com/Minecraft.Download/indexes/' + name
+    const resourceURL = 'http://resources.download.minecraft.net/'
+    const localPath = path.join(basePath, 'assets')
+    const indexPath = path.join(localPath, 'indexes')
+    const objectPath = path.join(localPath, 'objects')
+
+    request.head(indexURL, function (err, res, body) {
+        console.log('Downloading ' + version + ' asset index.')
+        mkpath.sync(indexPath)
+        let stream = request(indexURL).pipe(fs.createWriteStream(path.join(indexPath, name)))
+        stream.on('finish', function() {
+            let data = JSON.parse(fs.readFileSync(path.join(indexPath, name), 'utf-8'))
+            let assetArr = []
+            Object.keys(data['objects']).forEach(function(key, index){
+                let ob = data['objects'][key]
+                let hash = String(ob['hash'])
+                let assetName = path.join(hash.substring(0, 2), hash)
+                let urlName = hash.substring(0, 2) + "/" + hash
+                let ast = new Asset(resourceURL + urlName, path.join(objectPath, assetName), ob['size'])
+                assetArr.push(ast)
+            })
+            assetArr.forEach(function(item, index){
+                mkpath.sync(path.join(item.to, ".."))
+                console.log("downloading asset from " + item.from + " to " + item.to)
+                request(item.from).pipe(fs.createWriteStream(item.to))
+
+            })
+        })
+    })
+}