/**
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0.
 */

#include <aws/testing/AwsCppSdkGTestSuite.h>
#include <aws/core/utils/threading/Executor.h>
#include <aws/core/utils/threading/ReaderWriterLock.h>
#include <aws/core/utils/memory/stl/AWSString.h>

using namespace Aws::Utils::Threading;

class ReaderWriterLockTest : public Aws::Testing::AwsCppSdkGTestSuite
{
};

TEST_F(ReaderWriterLockTest, MultipleReadersMultipleWriters)
{
    Aws::String resource = "It's still Day One";
    std::atomic<size_t> resourceLength { resource.length() };
    const int ITERATIONS = 100;
    const int READER_THREADS = 100;
    const int WRITER_THREADS = 20;
    Semaphore ev(0, READER_THREADS + WRITER_THREADS);
    ReaderWriterLock rwlock;
    {
        DefaultExecutor exec;
        auto reader = [&] {
            ev.WaitOne();
            for(int i = 0; i < ITERATIONS; i++)
            {
                ReaderLockGuard guard(rwlock);
                ASSERT_GE(resource.length(), resourceLength);
            }
        };
        auto writer = [&] {
            ev.WaitOne();
            for(int i = 0; i < ITERATIONS; i++)
            {
                WriterLockGuard guard(rwlock);
                resource += "!";
                resourceLength = resource.length();
            }
        };

        for(int i = 0; i < WRITER_THREADS; i++)
        {
            exec.Submit(writer);
        }

        for(int i = 0; i < READER_THREADS; i++)
        {
            exec.Submit(reader);
        }

        ev.ReleaseAll();
    }
}

TEST_F(ReaderWriterLockTest, NoReadersMultipleWriters)
{
    Aws::String resource = "It's still Day One";
    const auto originalLength = resource.length();
    const int THREADS_NUM = 8;
    const int ITERATIONS = 100;
    Semaphore ev(0, 100);
    ReaderWriterLock rwlock;
    {
        DefaultExecutor exec;
        auto writer = [&] {
            ev.WaitOne();
            for(int i = 0; i < ITERATIONS; i++)
            {
                WriterLockGuard guard(rwlock);
                resource += "!";
            }
        };

        for(int i = 0; i < THREADS_NUM; i++)
        {
            exec.Submit(writer);
        }

        ev.ReleaseAll();
    }

    ASSERT_EQ(originalLength + THREADS_NUM * ITERATIONS, resource.length());
}