From 247b892d7ba82318d8749c166395cbd2e3a4c56b Mon Sep 17 00:00:00 2001
From: megawac <megawac@gmail.com>
Date: Tue, 8 Nov 2016 23:13:33 -0500
Subject: [PATCH] Initial token bucket implementation (#1314)

---
 lib/internal/TokenBucket.js | 39 +++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 lib/internal/TokenBucket.js

diff --git a/lib/internal/TokenBucket.js b/lib/internal/TokenBucket.js
new file mode 100644
index 000000000..993036301
--- /dev/null
+++ b/lib/internal/TokenBucket.js
@@ -0,0 +1,39 @@
+import DLL from './DoublyLinkedList';
+
+/**
+ * An internal implementation of [Token Bucket](https://en.wikipedia.org/wiki/Token_bucket)
+ * for rate-limiting/traffic shaping.
+ *
+ * @param {Number} bucketSize - the maximum number of items (inclusive) which can be queued in
+ * a interval of time.
+ * @param {Number} interval - the period in miliseconds to stop tracking a sent item
+ */
+export function TokenBucket(bucketSize, interval) {
+    this.bucketSize = bucketSize;
+    this.interval = interval;
+    this.queue = new DLL();
+    this.queued = 0; // Number of items sent + size of queue
+}
+
+/**
+ * Enqueue an operation to be executed
+ */
+TokenBucket.prototype.enqueue = function(operation) {
+    this.queued++;
+    if (this.queued <= this.bucketSize) {
+        operation();
+    } else {
+        this.queue.push(operation);
+    }
+
+    // after interval, decrement the queued count and call a queued operation (if bucket is full)
+    setTimeout(onIntervalComplete, this.interval, this);
+}
+
+function onIntervalComplete(bucket) {
+    bucket.queued--;
+    if (bucket.queue.length > 0) {
+        // call first queued operation
+        (bucket.queue.shift())();
+    }
+}