Record redirect events (github#16181)

* Record redirect events

* Update index.js

* Update record-redirect.js

* Only run when it can send to Hydro

* Update record-redirect.js

lib/hydro.js

@@ -21,6 +21,13 @@ module.exports = class Hydro {
     this.schemas = SCHEMAS
   }
 
+  /**
+   * Can check if it can actually send to Hydro
+   */
+  maySend () {
+    return Boolean(this.secret && this.endpoint)
+  }
+
   /**
    * Generate a SHA256 hash of the payload using the secret
    * to authenticate with Hydro

middleware/index.js

@@ -16,6 +16,9 @@ module.exports = function (app) {
   app.use(require('morgan')('dev', { skip: (req, res) => !isDevelopment }))
   app.use(require('./rate-limit'))
   if (isDevelopment) app.use(require('./webpack'))
+  app.use(require('./cookie-parser'))
+  app.use(require('./req-utils'))
+  app.use(require('./record-redirect'))
   app.use(require('./redirects/external'))
   app.use(require('./redirects/help-to-docs'))
   app.use(require('./set-fastly-cache-headers'))
@@ -24,9 +27,7 @@ module.exports = function (app) {
   app.use(require('./cors'))
   app.use(require('./csp'))
   app.use(require('helmet')())
-  app.use(require('./req-utils'))
   app.use(require('./robots'))
-  app.use(require('./cookie-parser'))
   app.use(express.json()) // Must come before ./csrf
   app.use(require('./csrf'))
   app.use(require('./handle-csrf-errors'))

middleware/record-redirect.js

@@ -0,0 +1,27 @@
+const { v4: uuidv4 } = require('uuid')
+const { inRange } = require('lodash')
+
+module.exports = function (req, res, next) {
+  if (!req.hydro.maySend()) return next()
+
+  res.on('finish', async function recordRedirect () {
+    if (!inRange(res.statusCode, 300, 400)) return
+    const schemaName = req.hydro.schemas.redirect
+    const redirectEvent = {
+      context: {
+        user: req.cookies['_docs-events'] || uuidv4(),
+        event_id: uuidv4(),
+        version: '1.0.0',
+        created: new Date().toISOString(),
+        path: req.path,
+        referrer: req.get('referer')
+      },
+      redirect_from: req.originalUrl,
+      redirect_to: res.get('location')
+    }
+    const hydroRes = await req.hydro.publish(schemaName, redirectEvent)
+    if (!hydroRes.ok) console.log('Failed to record redirect to Hydro')
+  })
+
+  return next()
+}