a few changes to make A/B testing easier

server/routes/download.js

@@ -0,0 +1,38 @@
+const storage = require('../storage');
+const mozlog = require('../log');
+const log = mozlog('send.download');
+
+function validateID(route_id) {
+  return route_id.match(/^[0-9a-fA-F]{10}$/) !== null;
+}
+
+module.exports = async function(req, res) {
+  const id = req.params.id;
+  if (!validateID(id)) {
+    return res.sendStatus(404);
+  }
+
+  try {
+    const meta = await storage.metadata(id);
+    const contentLength = await storage.length(id);
+    res.writeHead(200, {
+      'Content-Disposition': `attachment; filename=${meta.filename}`,
+      'Content-Type': 'application/octet-stream',
+      'Content-Length': contentLength,
+      'X-File-Metadata': JSON.stringify(meta)
+    });
+    const file_stream = storage.get(id);
+
+    file_stream.on('end', async () => {
+      try {
+        await storage.forceDelete(id);
+      } catch (e) {
+        log.info('DeleteError:', id);
+      }
+    });
+
+    file_stream.pipe(res);
+  } catch (e) {
+    res.sendStatus(404);
+  }
+};