Added support for Twitch's Chat Replies (#3722)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/messages/MessageThread.cpp

@@ -0,0 +1,61 @@
+#include "MessageThread.hpp"
+
+#include "messages/Message.hpp"
+#include "util/DebugCount.hpp"
+
+#include <utility>
+
+namespace chatterino {
+
+MessageThread::MessageThread(std::shared_ptr<const Message> rootMessage)
+    : rootMessageId_(rootMessage->id)
+    , rootMessage_(std::move(rootMessage))
+{
+    DebugCount::increase("message threads");
+}
+
+MessageThread::~MessageThread()
+{
+    DebugCount::decrease("message threads");
+}
+
+void MessageThread::addToThread(const std::shared_ptr<const Message> &message)
+{
+    this->replies_.emplace_back(message);
+}
+
+void MessageThread::addToThread(const std::weak_ptr<const Message> &message)
+{
+    this->replies_.push_back(message);
+}
+
+size_t MessageThread::liveCount() const
+{
+    size_t count = 0;
+    for (auto reply : this->replies_)
+    {
+        if (!reply.expired())
+        {
+            ++count;
+        }
+    }
+
+    return count;
+}
+
+size_t MessageThread::liveCount(
+    const std::shared_ptr<const Message> &exclude) const
+{
+    size_t count = 0;
+    for (auto reply : this->replies_)
+    {
+        if (!reply.expired() && reply.lock() != exclude)
+        {
+            ++count;
+        }
+    }
+
+    return count;
+}
+
+}  // namespace chatterino