#include <mutex>
#include <fstream>
#include <mysql/mysql.h>

class AutoMysqlLibraryDeinit
{
public:
    AutoMysqlLibraryDeinit()
    {
        mysql_library_init(0, nullptr, nullptr);
    }
    ~AutoMysqlLibraryDeinit()
    {
        mysql_library_end();
    }
};

class AutoMysqlClose
{
public:
    AutoMysqlClose(MYSQL* pCon) : m_pCon(pCon) {}
    ~AutoMysqlClose()
    {
        if(m_pCon)
        {
            mysql_close(m_pCon);
            m_pCon = nullptr;
        }
    }
private:
    MYSQL* m_pCon;
};

std::mutex mut;
std::ofstream out("$errors.txt", std::ios::app);

void MyThreadFunction()
{
    auto* pCon = mysql_init(nullptr);
    if(!pCon)
    {
        std::lock_guard<std::mutex> oLock(mut);
        out << "Failed mysql_init" << std::endl;
        return;
    }
    AutoMysqlClose amc(pCon);
    
    auto* pCon2 = mysql_real_connect(pCon, "localhost", "root", "<pwd>", "pstest", 3306, nullptr, CLIENT_MULTI_STATEMENTS);
    if(pCon != pCon2)
    {
        std::lock_guard<std::mutex> oLock(mut);
        out << "Failed mysql_real_connect" << std::endl;
        return;
    }
    const char szQuery[] = "CALL pstest_procedure()";
    const size_t nLen = strlen(szQuery);
    for(int i = 0; i < 100; ++i)
    {
        const auto nRes = mysql_real_query(pCon, szQuery, nLen);
        if(nRes)
        {
            const char* szErr = mysql_error(pCon);
            std::lock_guard<std::mutex> oLock(mut);
            out << szErr << std::endl;
            continue;
        }
        do
        {
            auto* pRes = mysql_store_result(pCon);
            mysql_free_result(pRes);
        }while(mysql_next_result(pCon));
    }
}

long Run()
{
    AutoMysqlLibraryDeinit amld;
    std::vector<std::thread> vecThreads;
    const size_t nThreads = 20;
    vecThreads.reserve(nThreads);
    for(size_t i = 0; i < nThreads; ++i)
    {
        vecThreads.emplace_back(std::thread(MyThreadFunction));
    }
    for(auto& oThread : vecThreads)
    {
        oThread.join();
    }
    
    return 0;
}

int main()
{
	Run();
	return 0;
}