//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2018 Ripple Labs Inc.

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
#include <xrpl/beast/asio/io_latency_probe.h>
#include <xrpl/beast/unit_test.h>

#include <xrpl/beast/test/yield_to.h>

#include <boost/asio/basic_waitable_timer.hpp>
#include <boost/asio/deadline_timer.hpp>
#include <boost/asio/io_service.hpp>

#include <algorithm>
#include <chrono>
#include <mutex>
#include <numeric>
#include <optional>
#include <thread>
#include <vector>

using namespace std::chrono_literals;

class io_latency_probe_test : public beast::unit_test::suite,
                              public beast::test::enable_yield_to
{
    using MyTimer =
        boost::asio::basic_waitable_timer<std::chrono::steady_clock>;

#ifdef RIPPLED_RUNNING_IN_CI
    /**
     * @brief attempt to measure inaccuracy of asio waitable timers
     *
     * This class is needed in some VM/CI environments where
     * timer inaccuracy impacts the io_probe tests below.
     *
     */
    template <
        class Clock,
        class MeasureClock = std::chrono::high_resolution_clock>
    struct measure_asio_timers
    {
        using duration = typename Clock::duration;
        using rep = typename MeasureClock::duration::rep;

        std::vector<duration> elapsed_times_;

        measure_asio_timers(duration interval = 100ms, size_t num_samples = 50)
        {
            using namespace std::chrono;
            boost::asio::io_service ios;
            std::optional<boost::asio::io_service::work> work{ios};
            std::thread worker{[&] { ios.run(); }};
            boost::asio::basic_waitable_timer<Clock> timer{ios};
            elapsed_times_.reserve(num_samples);
            std::mutex mtx;
            std::unique_lock<std::mutex> mainlock{mtx};
            std::condition_variable cv;
            bool done = false;
            boost::system::error_code wait_err;

            while (--num_samples)
            {
                auto const start{MeasureClock::now()};
                done = false;
                timer.expires_after(interval);
                timer.async_wait([&](boost::system::error_code const& ec) {
                    if (ec)
                        wait_err = ec;
                    auto const end{MeasureClock::now()};
                    elapsed_times_.emplace_back(end - start);
                    std::lock_guard lk{mtx};
                    done = true;
                    cv.notify_one();
                });
                cv.wait(mainlock, [&done] { return done; });
            }
            work.reset();
            worker.join();
            if (wait_err)
                boost::asio::detail::throw_error(wait_err, "wait");
        }

        template <class D>
        auto
        getMean()
        {
            double sum = {0};
            for (auto const& v : elapsed_times_)
            {
                sum += static_cast<double>(
                    std::chrono::duration_cast<D>(v).count());
            }
            return sum / elapsed_times_.size();
        }

        template <class D>
        auto
        getMax()
        {
            return std::chrono::duration_cast<D>(
                       *std::max_element(
                           elapsed_times_.begin(), elapsed_times_.end()))
                .count();
        }

        template <class D>
        auto
        getMin()
        {
            return std::chrono::duration_cast<D>(
                       *std::min_element(
                           elapsed_times_.begin(), elapsed_times_.end()))
                .count();
        }
    };
#endif

    struct test_sampler
    {
        beast::io_latency_probe<std::chrono::steady_clock> probe_;
        std::vector<std::chrono::steady_clock::duration> durations_;

        test_sampler(
            std::chrono::milliseconds interval,
            boost::asio::io_service& ios)
            : probe_(interval, ios)
        {
        }

        void
        start()
        {
            probe_.sample(std::ref(*this));
        }

        void
        start_one()
        {
            probe_.sample_one(std::ref(*this));
        }

        void
        operator()(std::chrono::steady_clock::duration const& elapsed)
        {
            durations_.push_back(elapsed);
        }
    };

    void
    testSampleOne(boost::asio::yield_context& yield)
    {
        testcase << "sample one";
        boost::system::error_code ec;
        test_sampler io_probe{100ms, get_io_service()};
        io_probe.start_one();
        MyTimer timer{get_io_service(), 1s};
        timer.async_wait(yield[ec]);
        if (!BEAST_EXPECTS(!ec, ec.message()))
            return;
        BEAST_EXPECT(io_probe.durations_.size() == 1);
        io_probe.probe_.cancel_async();
    }

    void
    testSampleOngoing(boost::asio::yield_context& yield)
    {
        testcase << "sample ongoing";
        boost::system::error_code ec;
        using namespace std::chrono;
        auto interval = 99ms;
        auto probe_duration = 1s;

        size_t expected_probe_count_max = (probe_duration / interval);
        size_t expected_probe_count_min = expected_probe_count_max;
#ifdef RIPPLED_RUNNING_IN_CI
        // adjust min expected based on measurements
        // if running in CI/VM environment
        measure_asio_timers<steady_clock> tt{interval};
        log << "measured mean for timers: " << tt.getMean<milliseconds>()
            << "ms\n";
        log << "measured max for timers: " << tt.getMax<milliseconds>()
            << "ms\n";
        expected_probe_count_min =
            static_cast<size_t>(
                duration_cast<milliseconds>(probe_duration).count()) /
            static_cast<size_t>(tt.getMean<milliseconds>());
#endif
        test_sampler io_probe{interval, get_io_service()};
        io_probe.start();
        MyTimer timer{get_io_service(), probe_duration};
        timer.async_wait(yield[ec]);
        if (!BEAST_EXPECTS(!ec, ec.message()))
            return;
        auto probes_seen = io_probe.durations_.size();
        BEAST_EXPECTS(
            probes_seen >= (expected_probe_count_min - 1) &&
                probes_seen <= (expected_probe_count_max + 1),
            std::string("probe count is ") + std::to_string(probes_seen));
        io_probe.probe_.cancel_async();
        // wait again in order to flush the remaining
        // probes from the work queue
        timer.expires_from_now(1s);
        timer.async_wait(yield[ec]);
    }

    void
    testCanceled(boost::asio::yield_context& yield)
    {
        testcase << "canceled";
        test_sampler io_probe{100ms, get_io_service()};
        io_probe.probe_.cancel_async();
        except<std::logic_error>([&io_probe]() { io_probe.start_one(); });
        except<std::logic_error>([&io_probe]() { io_probe.start(); });
    }

public:
    void
    run() override
    {
        yield_to([&](boost::asio::yield_context& yield) {
            testSampleOne(yield);
            testSampleOngoing(yield);
            testCanceled(yield);
        });
    }
};

BEAST_DEFINE_TESTSUITE(io_latency_probe, asio, beast);
