// License: Apache 2.0. See LICENSE file in root directory.
// Copyright(c) 2021 Intel Corporation. All Rights Reserved.

#include <unit-tests/test.h>
#include <rsutils/time/timer.h>
#include <rsutils/concurrency/concurrency.h>

#include <algorithm>
#include <vector>
#include <iostream>

using namespace rsutils::time;

// We use this function as a CPU stress test function
int fibo( int num )
{
    if( num < 2 )
        return 1;
    return fibo( num - 1 ) + fibo( num - 2 );
}

TEST_CASE( "dispatcher main flow" )
{
    dispatcher d(3);
    std::atomic_bool run = { false };
    auto func = [&](dispatcher::cancellable_timer c) 
    {
        c.try_sleep(std::chrono::seconds(1));
        run = true;
    };

    d.start();
    REQUIRE(d.empty());
    // We want to make sure that if we invoke some functions, the dispatcher is not empty.
    // We add 2 functions that take some time so that even if the first one pop,
    // the second will still be in the queue and it will not be empty
    d.invoke(func);
    d.invoke(func);
    REQUIRE_FALSE(d.empty());
    REQUIRE(d.flush());
    REQUIRE(run);
    d.stop();   
}

TEST_CASE( "invoke and wait" )
{
    dispatcher d(2);

    std::atomic_bool run = { false };
    auto func = [&](dispatcher::cancellable_timer c)
    {
        std::this_thread::sleep_for(std::chrono::seconds(3));
        run = true;
    };

    d.start();
    stopwatch sw;
    d.invoke_and_wait(func, []() {return false; }, true);
    REQUIRE( sw.get_elapsed() > std::chrono::seconds( 3 ) ); // verify we get here only after the function call ended
    d.stop();
}

TEST_CASE("verify stop() not consuming high CPU usage")
{
    // using shared_ptr because no copy constructor is allowed for a dispatcher.
    std::vector<std::shared_ptr<dispatcher>> dispatchers;

    for (int i = 0 ; i < 32; ++i)
    {
        dispatchers.push_back(std::make_shared<dispatcher>(10));
    }

    for (auto &&dispatcher : dispatchers)
    {
        dispatcher->start();
    }

    for (auto&& dispatcher : dispatchers)
    {
        dispatcher->stop();
    }

  
    // Allow some time for all threads to do some work
    std::this_thread::sleep_for(std::chrono::seconds(5));

    stopwatch sw;

    // Do some stress work
    REQUIRE(fibo(40) == 165580141);
    // Verify the stress test did not take too long.
    // We had an issue that stop() call cause a high CPU usage and therefore other operations stall, 
    // This test took > 9 seconds on an 8 cores PC, after the fix it took ~1.5 sec on 1 core run (on release configuration).
    // We allow 9 seconds to support debug configuration as well
    REQUIRE( sw.get_elapsed() < std::chrono::seconds( 9 ) );
}

TEST_CASE("stop() notify flush to finish")
{
    // On this test we check that if during a flush() another thread call stop(),
    // than the flush CV will be triggered to exit and not wait a full timeout
    dispatcher dispatcher( 10 );
    dispatcher.start();

    stopwatch sw;
    std::atomic_bool dispatched_end_verifier{ false };
    dispatcher.invoke( [&]( dispatcher::cancellable_timer c ) {
        //std::cout << "Sleeping from inside invoke" << std::endl;
        std::this_thread::sleep_for( std::chrono::seconds( 3 ) );
        //std::cout << "Sleeping from inside invoke - Done" << std::endl;
        dispatched_end_verifier = true;
    } );

    // Make sure the above invoke function is dispatched
    std::this_thread::sleep_for( std::chrono::milliseconds( 100 ) );

    std::thread stop_thread( [&]() {
        // Make sure we postpone the stop to after the flush call
        std::this_thread::sleep_for( std::chrono::milliseconds( 100 ) );
        //std::cout << "Stopping dispatcher" << std::endl;
        dispatcher.stop();
    } );

    auto timeout = std::chrono::seconds(5);
    //std::cout << "Flushing dispatcher" << std::endl;
    CHECK(!dispatcher.flush(timeout));
    // We expect that flush will be triggered by stop only after the dispatched function end.
    CHECK(dispatched_end_verifier);
    //std::cout << "Flushing is done" << std::endl;
    CHECK( sw.get_elapsed() < timeout );
    stop_thread.join();
}