From ac22b59a40cd7607ab19ff334a7f524f6f943667 Mon Sep 17 00:00:00 2001
From: Michael Carlberg <c@rlberg.se>
Date: Tue, 21 Jun 2016 04:16:55 +0200
Subject: [PATCH] feat: EventThrottler

---
 include/services/event_throttler.hpp | 31 +++++++++++++++++++++
 src/CMakeLists.txt                   |  1 +
 src/services/event_throttler.cpp     | 40 ++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+)
 create mode 100644 include/services/event_throttler.hpp
 create mode 100644 src/services/event_throttler.cpp

diff --git a/include/services/event_throttler.hpp b/include/services/event_throttler.hpp
new file mode 100644
index 00000000..cd3c0040
--- /dev/null
+++ b/include/services/event_throttler.hpp
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <chrono>
+#include <deque>
+#include <memory>
+#include <string>
+
+namespace event_throttler
+{
+  typedef std::chrono::duration<double, std::milli> timewindow_t;
+  typedef std::chrono::high_resolution_clock timepoint_clock_t;
+  typedef event_throttler::timepoint_clock_t::time_point timepoint_t;
+  typedef std::deque<event_throttler::timepoint_t> queue_t;
+  typedef std::size_t limit_t;
+}
+
+class EventThrottler
+{
+  event_throttler::queue_t event_queue;
+  event_throttler::limit_t passthrough_limit;
+  event_throttler::timewindow_t timewindow;
+
+  protected:
+    void expire();
+
+  public:
+    explicit EventThrottler(int limit, event_throttler::timewindow_t timewindow)
+      : passthrough_limit(limit), timewindow(timewindow) {}
+
+    bool passthrough();
+};
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 9967d678..1d223aab 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -43,6 +43,7 @@ set(SOURCE_FILES
   "src/modules/text.cpp"
   "src/services/builder.cpp"
   "src/services/command.cpp"
+  "src/services/event_throttler.cpp"
   "src/services/inotify.cpp"
   "src/services/logger.cpp"
   # "src/services/store.cpp"
diff --git a/src/services/event_throttler.cpp b/src/services/event_throttler.cpp
new file mode 100644
index 00000000..688aa8fd
--- /dev/null
+++ b/src/services/event_throttler.cpp
@@ -0,0 +1,40 @@
+#include <thread>
+
+#include "services/event_throttler.hpp"
+#include "services/logger.hpp"
+
+using namespace event_throttler;
+
+bool EventThrottler::passthrough()
+{
+  // Remove expired frames from the queue
+  this->expire();
+
+  // Place the new frame in the bottom of the deck
+  this->event_queue.emplace_back(timepoint_clock_t::now());
+
+  // Check if the limit has been reached
+  if (this->event_queue.size() >= this->passthrough_limit) {
+    // std::this_thread::sleep_for(this->timewindow * this->event_queue.size());
+    std::this_thread::sleep_for(this->timewindow);
+
+    if (this->event_queue.size() - 1 >= this->passthrough_limit) {
+      log_trace("Event passthrough throttled");
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void EventThrottler::expire()
+{
+  auto now = timepoint_clock_t::now();
+
+  while (this->event_queue.size() > 0) {
+    if ((now - this->event_queue.front()) < this->timewindow)
+      break;
+
+    this->event_queue.pop_front();
+  }
+}