ADD unit tests, split and refactor source code

src/assets/untar.js

@@ -0,0 +1,25 @@
+const tar = require('tar');
+const zlib = require('zlib');
+
+/**
+ * Unzip strategy for resources using `.tar.gz`.
+ *
+ * First we will Un-GZip, then we will untar. So once untar is completed,
+ * binary is downloaded into `binPath`. Verify the binary and call it good.
+ */
+function untar({ opts, req, onSuccess, onError }) {
+
+  const ungz = zlib.createGunzip();
+  const untar = tar.Extract({ path: opts.binPath });
+
+  ungz.on('error', onError);
+  untar.on('error', onError);
+
+  // First we will Un-GZip, then we will untar. So once untar is completed,
+  // binary is downloaded into `binPath`. Verify the binary and call it good
+  untar.on('end', onSuccess);
+
+  req.pipe(ungz).pipe(untar);
+}
+
+module.exports = untar;