From 492003bc2e66af0351c8dc03fd8505bada79126c Mon Sep 17 00:00:00 2001
From: Damir Zainullin <zaidamilda@gmail.com>
Date: Mon, 2 Dec 2024 00:42:47 +0100
Subject: [PATCH] Top 10 ports - Introduce TopPorts class

---
 input/topPorts.hpp | 58 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 input/topPorts.hpp

diff --git a/input/topPorts.hpp b/input/topPorts.hpp
new file mode 100644
index 00000000..d42716c0
--- /dev/null
+++ b/input/topPorts.hpp
@@ -0,0 +1,58 @@
+/**
+ * \file topPorts.hpp
+ * \brief Template class implementing the most popular ports.
+ * \author Damir Zainullin <zaidamilda@gmail.com>
+ * \date 2024
+ */
+#pragma once
+
+#include <array>
+#include <cstdint>
+#include <functional>
+#include <limits>
+
+namespace ipxp {
+/**
+ * \brief Top ports counter.
+ * \tparam TopPortsCount Number of the most popular ports to store.
+ */
+template<std::size_t TopPortsCount>
+class TopPorts {
+public:
+    /**
+     * \brief Increments number of times given port has been seen.
+     * \param port Port to increment its frequency.
+     */
+    void increment_frequency(uint16_t port) noexcept
+    {
+        m_port_frequencies[port]++;
+    }
+
+    /**
+     * \brief Get the top ports.
+     * \return Pair of the top ports array and their count.
+     */
+    std::pair<std::array<std::pair<uint16_t, size_t>, TopPortsCount>, size_t>
+    get_top_ports() const noexcept
+    {
+        std::array<std::pair<uint16_t, size_t>, TopPortsCount> res{};
+        size_t ports_inserted = 0;
+        std::for_each(m_port_frequencies.begin(), m_port_frequencies.end(),[&, port = 0](size_t count) mutable {
+            auto port_pos = std::lower_bound(res.begin(), res.end(), count, [](const std::pair<uint16_t, size_t>& portCount, size_t count) {
+                return portCount.second >= count;
+            });
+            if (port_pos != res.end()) {
+                std::copy_backward(port_pos, std::prev(res.end()), res.end());
+                *port_pos = std::make_pair(port, count);
+                ports_inserted = std::min(TopPortsCount, ports_inserted + 1);
+            }
+            port++;
+        });
+        return {res, ports_inserted};
+    }
+
+private:
+    std::array<std::size_t, std::numeric_limits<uint16_t>::max() + 1> m_port_frequencies {};
+};
+
+} // namespace ipxp