implemented amplitude metrics (#1141)

server/routes/delete.js

@@ -1,9 +1,20 @@
 const storage = require('../storage');
+const { statDeleteEvent } = require('../amplitude');
 
 module.exports = async function(req, res) {
   try {
-    await storage.del(req.params.id);
+    const id = req.params.id;
+    const meta = req.meta;
+    const ttl = await storage.ttl(id);
+    await storage.del(id);
     res.sendStatus(200);
+    statDeleteEvent({
+      id,
+      ip: req.ip,
+      owner: meta.owner,
+      download_count: meta.dl,
+      ttl
+    });
   } catch (e) {
     res.sendStatus(404);
   }