1 files changed, 103 insertions, 0 deletions
diff --git a/server/src/core/rateLimiter.js b/server/src/core/rateLimiter.js
new file mode 100644
index 0000000..0c2a384
--- /dev/null
+++ b/server/src/core/rateLimiter.js
@@ -0,0 +1,103 @@
+/**
+  * Tracks frequency of occurances based on `id` (remote address), then allows or
+  * denies command execution based on comparison with `threshold`
+  *
+  * Version: v2.0.0
+  * Developer: Marzavec ( https://github.com/marzavec )
+  * License: WTFPL ( http://www.wtfpl.net/txt/copying/ )
+  *
+  */
+
+class Police {
+  /**
+   * Create a ratelimiter instance.
+   */
+  constructor () {
+    this._records = {};
+    this._halflife = 30 * 1000; // milliseconds
+    this._threshold = 25;
+    this._hashes = [];
+  }
+
+  /**
+    * Finds current score by `id`
+    *
+    * @param {String} id target id / address
+    * @public
+    *
+    * @memberof Police
+    */
+  search (id) {
+    let record = this._records[id];
+
+    if (!record) {
+      record = this._records[id] = {
+        time: Date.now(),
+        score: 0
+      }
+    }
+
+    return record;
+  }
+
+  /**
+    * Adjusts the current ratelimit score by `deltaScore`
+    *
+    * @param {String} id target id / address
+    * @param {Number} deltaScore amount to adjust current score by
+    * @public
+    *
+    * @memberof Police
+    */
+  frisk (id, deltaScore) {
+    let record = this.search(id);
+
+    if (record.arrested) {
+      return true;
+    }
+
+    record.score *= Math.pow(2, -(Date.now() - record.time ) / this._halflife);
+    record.score += deltaScore;
+    record.time = Date.now();
+
+    if (record.score >= this._threshold) {
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+    * Statically set server to no longer accept traffic from `id`
+    *
+    * @param {String} id target id / address
+    * @public
+    *
+    * @memberof Police
+    */
+  arrest (id, hash) {
+    let record = this.search(id);
+
+    record.arrested = true;
+    this._hashes[hash] = id;
+  }
+
+  /**
+    * Remove statically assigned limit from `id`
+    *
+    * @param {String} id target id / address
+    * @public
+    *
+    * @memberof Police
+    */
+  pardon (id) {
+    if (typeof this._hashes[id] !== 'undefined') {
+      id = this._hashes[id];
+    }
+    
+    let record = this.search(id);
+    record.arrested = false;
+  }
+}
+
+module.exports = Police;