introduce the aircraft scheduler to receive new messages from the backend

threading-concepts are used to avoid unnecessary main thread action

include/aman/com/AircraftScheduler.h

@@ -0,0 +1,75 @@
+/*
+ * @brief Defines the aircraft scheduling notifier module to receive plans from the backend
+ * @file aman/com/AircraftScheduler.h
+ * @author Sven Czarnian <devel@svcz.de>
+ * @copyright Copyright 2021 Sven Czarnian
+ * @license This project is published under the GNU General Public License v3 (GPLv3)
+ */
+
+#pragma once
+
+#include <thread>
+#include <zmq.hpp>
+
+#include <aman/types/Communication.h>
+
+#include "protobuf/AircraftSchedule.pb.h"
+
+namespace aman {
+    /**
+     * @brief Defines the aircraft scheduling notification class to receive scheduling sequences
+     * @ingroup com
+     */
+    class AircraftScheduler {
+    private:
+        std::unique_ptr<zmq::socket_t> m_socket;
+        std::thread                    m_receiverThread;
+        std::atomic_bool               m_stopReceiver;
+
+        AircraftScheduler() noexcept;
+
+        template <typename T>
+        bool setSocketKey(const std::string& key, T entry) {
+            try {
+                this->m_socket->set(entry, key);
+                return true;
+            }
+            catch (std::exception&) {
+                return false;
+            }
+        }
+        void run();
+
+    public:
+        AircraftScheduler(const AircraftScheduler&) = delete;
+        AircraftScheduler(AircraftScheduler&&) = delete;
+        AircraftScheduler& operator=(const AircraftScheduler&) = delete;
+        AircraftScheduler& operator=(AircraftScheduler&&) = delete;
+
+        /**
+         * @brief Initializes the aircraft scheduler
+         * @param[in] configuration The current AMAM communication configuration
+         * @return True if the initialization is done, else false
+         */
+        bool initialize(const Communication& configuration);
+        /**
+         * @brief Terminates the scheduler connection
+         */
+        bool deinitialize();
+        /**
+         * @brief Checks if the scheduler is initialized
+         * @return True if it is initialized, else false
+         */
+        bool initialized() const noexcept;
+        /**
+         * @brief Receives a new scheduling message
+         * @return The new scheduling message or a nullptr
+         */
+        std::unique_ptr<aman::AircraftSchedule> receive();
+        /**
+         * @brief Returns the scheduling instance
+         * @return The system-wide instance
+         */
+        static AircraftScheduler& instance() noexcept;
+    };
+}