/*
 *  Copyright 2013. Lawrence Livermore National Security, LLC.
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Steven Smith <smith84@llnl.gov>
 */

/**
 * @file
 * @ingroup mpi
 * Declaration of class ns3::MpiInterface.
 */

#ifndef NS3_MPI_INTERFACE_H
#define NS3_MPI_INTERFACE_H

#include "ns3/nstime.h"
#include "ns3/packet.h"

#include <mpi.h>

namespace ns3
{
/**
 * @defgroup mpi MPI Distributed Simulation
 */

/**
 * @ingroup mpi
 * @ingroup tests
 * @defgroup mpi-tests MPI Distributed Simulation tests
 */

class ParallelCommunicationInterface;

/**
 * @ingroup mpi
 *
 * @brief Singleton used to interface to the communications infrastructure
 * when running NS3 in parallel.
 *
 * Delegates the implementation to the specific parallel
 * infrastructure being used.  Implementation is defined in the
 * ParallelCommunicationInterface virtual base class; this API mirrors
 * that interface.  This singleton is responsible for instantiating an
 * instance of the communication interface based on
 * SimulatorImplementationType attribute in ns3::GlobalValues.  The
 * attribute must be set before Enable is invoked.
 */
class MpiInterface
{
  public:
    /**
     * @brief Deletes storage used by the parallel environment.
     */
    static void Destroy();
    /**
     * @brief Get the id number of this rank.
     *
     * When running a sequential simulation this will return a systemID of 0.
     *
     * @return system identification
     */
    static uint32_t GetSystemId();
    /**
     * @brief Get the number of ranks used by ns-3.
     *
     * Returns the size (number of MPI ranks) of the communicator used by
     * ns-3.  When running a sequential simulation this will return a
     * size of 1.
     *
     * @return number of parallel tasks
     */
    static uint32_t GetSize();
    /**
     * @brief Returns enabled state of parallel environment.
     *
     * @return true if parallel communication is enabled
     */
    static bool IsEnabled();
    /**
     * @brief Setup the parallel communication interface.
     *
     * There are two ways to setup the communications interface.  This
     * Enable method is the easiest method and should be used in most
     * situations.
     *
     * Disable() must be invoked at end of an ns-3 application to
     * properly cleanup the parallel communication interface.
     *
     * This method will call MPI_Init and configure ns-3 to use the
     * MPI_COMM_WORLD communicator.
     *
     * For more complex situations, such as embedding ns-3 with other
     * MPI simulators or libraries, the Enable(MPI_Comm communicator)
     * may be used if MPI is initialized externally or if ns-3 needs to
     * be run unique communicator.  For example if there are two
     * parallel simulators and the goal is to run each simulator on a
     * different set of ranks.
     *
     * @note The `SimulatorImplementationType` attribute in
     * ns3::GlobalValues must be set before calling Enable()
     *
     * @param pargc number of command line arguments
     * @param pargv command line arguments
     */
    static void Enable(int* pargc, char*** pargv);
    /**
     * @brief Setup the parallel communication interface using the specified communicator.
     *
     * See @ref Enable (int* pargc, char*** pargv) for additional information.
     *
     * @param communicator MPI Communicator that should be used by ns-3
     */
    static void Enable(MPI_Comm communicator);
    /**
     * @brief Clean up the ns-3 parallel communications interface.
     *
     * MPI_Finalize will be called only if Enable (int* pargc, char***
     * pargv) was called.
     */
    static void Disable();
    /**
     * @brief Send a packet to a remote node.
     *
     * @param p packet to send
     * @param rxTime received time at destination node
     * @param node destination node
     * @param dev destination device
     *
     * Serialize and send a packet to the specified node and net device
     */
    static void SendPacket(Ptr<Packet> p, const Time& rxTime, uint32_t node, uint32_t dev);

    /**
     * @brief Return the communicator used to run ns-3.
     *
     * The communicator returned will be MPI_COMM_WORLD if Enable (int*
     * pargc, char*** pargv) is used to enable or the user specified
     * communicator if Enable (MPI_Comm communicator) is used.
     *
     * @return The MPI Communicator.
     */
    static MPI_Comm GetCommunicator();

  private:
    /**
     * Common enable logic.
     */
    static void SetParallelSimulatorImpl();

    /**
     * Static instance of the instantiated parallel controller.
     */
    static ParallelCommunicationInterface* g_parallelCommunicationInterface;
};

} // namespace ns3

#endif /* NS3_MPI_INTERFACE_H */