Rate limit outgoing JOIN messages (#3115)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>
Co-authored-by: Tal Neoran <talneoran@gmail.com>

src/util/RatelimitBucket.cpp

@@ -0,0 +1,45 @@
+#include "RatelimitBucket.hpp"
+
+#include <QTimer>
+
+namespace chatterino {
+
+RatelimitBucket::RatelimitBucket(int budget, int cooldown,
+                                 std::function<void(QString)> callback,
+                                 QObject *parent)
+    : QObject(parent)
+    , budget_(budget)
+    , cooldown_(cooldown)
+    , callback_(callback)
+{
+}
+
+void RatelimitBucket::send(QString channel)
+{
+    this->queue_.append(channel);
+
+    if (this->budget_ > 0)
+    {
+        this->handleOne();
+    }
+}
+
+void RatelimitBucket::handleOne()
+{
+    if (queue_.isEmpty())
+    {
+        return;
+    }
+
+    auto item = queue_.takeFirst();
+
+    this->budget_--;
+    callback_(item);
+
+    QTimer::singleShot(cooldown_, this, [this] {
+        this->budget_++;
+        this->handleOne();
+    });
+}
+
+}  // namespace chatterino

src/util/RatelimitBucket.hpp

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <QList>
+#include <QObject>
+#include <QString>
+
+namespace chatterino {
+
+class RatelimitBucket : public QObject
+{
+public:
+    RatelimitBucket(int budget, int cooldown,
+                    std::function<void(QString)> callback, QObject *parent);
+
+    void send(QString channel);
+
+private:
+    /**
+     * @brief budget_ denotes the amount of calls that can be handled before we need to wait for the cooldown
+     **/
+    int budget_;
+
+    /**
+     * @brief This is the amount of time in milliseconds it takes for one used up budget to be put back into the bucket for use elsewhere
+     **/
+    const int cooldown_;
+
+    std::function<void(QString)> callback_;
+    QList<QString> queue_;
+
+    /**
+     * @brief Run the callback on one entry in the queue.
+     *
+     * This will start a timer that runs after cooldown_ milliseconds that
+     * gives back one "token" to the bucket and calls handleOne again.
+     **/
+    void handleOne();
+};
+
+}  // namespace chatterino