feat(breaking change): use stream on stats.bw

src/stats/bw.js

@@ -2,20 +2,15 @@
 
 const promisify = require('promisify-es6')
 const streamToValue = require('../utils/stream-to-value')
+const { Transform } = require('readable-stream')
 
-const transform = function (res, callback) {
-  streamToValue(res, (err, data) => {
-    if (err) {
-      return callback(err)
-    }
-
-    callback(null, {
-      totalIn: data[0].TotalIn,
-      totalOut: data[0].TotalOut,
-      rateIn: data[0].RateIn,
-      rateOut: data[0].RateOut
-    })
-  })
+const transformChunk = (chunk) => {
+  return {
+    totalIn: chunk.TotalIn,
+    totalOut: chunk.TotalOut,
+    rateIn: chunk.RateIn,
+    rateOut: chunk.RateOut
+  }
 }
 
 module.exports = (send) => {
@@ -28,6 +23,28 @@ module.exports = (send) => {
     send.andTransform({
       path: 'stats/bw',
       qs: opts
-    }, transform, callback)
+    }, (res, callback) => {
+      if (!opts.poll) {
+        // If not polling, just send the result.
+        return streamToValue(res, (err, data) => {
+          if (err) {
+            return callback(err)
+          }
+
+          callback(null, transformChunk(data[0]))
+        })
+      }
+
+      // If polling, return a readable stream.
+      const output = new Transform({
+        objectMode: true,
+        transform(chunk, encoding, cb) {
+          cb(null, transformChunk(chunk))
+        }
+      })
+
+      res.pipe(output)
+      callback(null, output)
+    }, callback)
   })
 }