/*
 * SPDX-License-Identifier: GPL-2.0-only
 */

#include "ns3/core-module.h"

#include <chrono>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <iostream>

using namespace ns3;

/**
 * @ingroup system-tests-perf
 *
 * Check the performance of writing to file.
 *
 * @param file The file to write to.
 * @param n The number of writes to perform.
 * @param buffer The buffer to write.
 * @param size The buffer size.
 */
void
PerfFile(FILE* file, uint32_t n, const char* buffer, uint32_t size)
{
    for (uint32_t i = 0; i < n; ++i)
    {
        if (std::fwrite(buffer, 1, size, file) != size)
        {
            NS_ABORT_MSG("PerfFile():  fwrite error");
        }
    }
}

/**
 * @ingroup system-tests-perf
 *
 * Check the performance of writing to an output stream.
 *
 * @param stream The output stream to write to.
 * @param n The number of writes to perform.
 * @param buffer The buffer to write.
 * @param size The buffer size.
 */
void
PerfStream(std::ostream& stream, uint32_t n, const char* buffer, uint32_t size)
{
    for (uint32_t i = 0; i < n; ++i)
    {
        stream.write(buffer, size);
    }
}

int
main(int argc, char* argv[])
{
    uint32_t n = 100000;
    uint32_t iter = 50;
    bool doStream = false;
    bool binmode = true;

    CommandLine cmd(__FILE__);
    cmd.AddValue("n", "How many times to write (defaults to 100000", n);
    cmd.AddValue("iter", "How many times to run the test looking for a min (defaults to 50)", iter);
    cmd.AddValue("doStream", "Run the C++ I/O benchmark otherwise the C I/O ", doStream);
    cmd.AddValue("binmode",
                 "Select binary mode for the C++ I/O benchmark (defaults to true)",
                 binmode);
    cmd.Parse(argc, argv);

    auto minResultNs =
        std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::nanoseconds::max());

    char buffer[1024];

    if (doStream)
    {
        //
        // This will probably run on a machine doing other things.  Run it some
        // relatively large number of times and try to find a minimum, which
        // will hopefully represent a time when it runs free of interference.
        //
        for (uint32_t i = 0; i < iter; ++i)
        {
            std::ofstream stream;
            if (binmode)
            {
                stream.open("streamtest", std::ios_base::binary | std::ios_base::out);
            }
            else
            {
                stream.open("streamtest", std::ios_base::out);
            }

            auto start = std::chrono::steady_clock::now();
            PerfStream(stream, n, buffer, 1024);
            auto end = std::chrono::steady_clock::now();
            auto resultNs = std::chrono::duration_cast<std::chrono::nanoseconds>(end - start);
            resultNs = std::min(resultNs, minResultNs);
            stream.close();
            std::cout << ".";
            std::cout.flush();
        }

        std::cout << std::endl;
    }
    else
    {
        //
        // This will probably run on a machine doing other things.  Run it some
        // relatively large number of times and try to find a minimum, which
        // will hopefully represent a time when it runs free of interference.
        //
        for (uint32_t i = 0; i < iter; ++i)
        {
            FILE* file = fopen("filetest", "w");

            auto start = std::chrono::steady_clock::now();
            PerfFile(file, n, buffer, 1024);
            auto end = std::chrono::steady_clock::now();
            auto resultNs = std::chrono::duration_cast<std::chrono::nanoseconds>(end - start);
            resultNs = std::min(resultNs, minResultNs);
            fclose(file);
            file = nullptr;
            std::cout << ".";
            std::cout.flush();
        }
        std::cout << std::endl;
    }

    std::cout << argv[0] << ": " << minResultNs.count() << "ns" << std::endl;

    return 0;
}