/*
 * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include "DatabaseWorkerPool.h"
#include "AdhocStatement.h"
#include "Common.h"
#include "Errors.h"
#include "IoContext.h"
#include "Implementation/LoginDatabase.h"
#include "Implementation/WorldDatabase.h"
#include "Implementation/CharacterDatabase.h"
#include "Implementation/HotfixDatabase.h"
#include "Log.h"
#include "MySQLPreparedStatement.h"
#include "PreparedStatement.h"
#include "ProducerConsumerQueue.h"
#include "QueryCallback.h"
#include "QueryHolder.h"
#include "QueryResult.h"
#include "Transaction.h"
#include "MySQLWorkaround.h"
#include <boost/asio/use_future.hpp>
#include <mysqld_error.h>
#include <utility>
#ifdef TRINITY_DEBUG
#include <boost/stacktrace.hpp>
#endif

static consteval uint32 ParseVersionString(std::string_view chars)
{
    uint32 result = 0;
    uint32 partialResult = 0;
    uint32 multiplier = 10000;
    for (std::size_t i =  0; i < chars.length(); ++i)
    {
        char c = chars[i];
        if (c == '.')
        {
            if (multiplier < 100)
                throw "Too many . characters in version string";

            result += partialResult * multiplier;
            multiplier /= 100;
            partialResult = 0;
        }
        else if (c >= '0' && c <= '9')
        {
            partialResult *= 10;
            partialResult += c - '0';
        }
        else
            throw "Invalid input character";
    }

    result += partialResult * multiplier;

    return result;
}

namespace
{
#ifdef TRINITY_DEBUG
template<typename Database>
thread_local bool WarnSyncQueries = false;
#endif
}

template<typename T>
struct DatabaseWorkerPool<T>::QueueSizeTracker
{
    explicit QueueSizeTracker(DatabaseWorkerPool* pool) : _pool(pool)
    {
        ++_pool->_queueSize;
    }

    QueueSizeTracker(QueueSizeTracker const& other) : _pool(other._pool) { ++_pool->_queueSize; }
    QueueSizeTracker(QueueSizeTracker&& other) noexcept : _pool(std::exchange(other._pool, nullptr)) { }

    QueueSizeTracker& operator=(QueueSizeTracker const& other)
    {
        if (this != &other)
        {
            if (_pool != other._pool)
            {
                if (_pool)
                    --_pool->_queueSize;
                if (other._pool)
                    ++other._pool->_queueSize;
            }
            _pool = other._pool;
        }
        return *this;
    }
    QueueSizeTracker& operator=(QueueSizeTracker&& other) noexcept
    {
        if (this != &other)
        {
            if (_pool != other._pool)
            {
                if (_pool)
                    --_pool->_queueSize;
            }
            _pool = std::exchange(other._pool, nullptr);
        }
        return *this;
    }

    ~QueueSizeTracker()
    {
        if (_pool)
            --_pool->_queueSize;
    }

private:
    DatabaseWorkerPool* _pool;
};

template <class T>
DatabaseWorkerPool<T>::DatabaseWorkerPool()
    : _async_threads(0), _synch_threads(0)
{
    // We only need check compiled version match on Windows
    // because on other platforms ABI compatibility is ensured by SOVERSION
    // and Windows MySQL releases don't even have abi-version-like component in their dll file name
#if TRINITY_PLATFORM == TRINITY_PLATFORM_WINDOWS
#if defined(LIBMARIADB) && MARIADB_PACKAGE_VERSION_ID >= 30200
#define TRINITY_COMPILED_CLIENT_VERSION MARIADB_PACKAGE_VERSION_ID
#else
#define TRINITY_COMPILED_CLIENT_VERSION MYSQL_VERSION_ID
#endif
    WPFatal(mysql_get_client_version() == TRINITY_COMPILED_CLIENT_VERSION, "Used " TRINITY_MYSQL_FLAVOR " library version (%s id %lu) does not match the version id used to compile TrinityCore (id %u). Search on forum for TCE00011.", mysql_get_client_info(), mysql_get_client_version(), TRINITY_COMPILED_CLIENT_VERSION);
#undef TRINITY_COMPILED_CLIENT_VERSION
#endif
}

template <class T>
DatabaseWorkerPool<T>::~DatabaseWorkerPool()
{
}

template <class T>
void DatabaseWorkerPool<T>::SetConnectionInfo(std::string const& infoString,
    uint8 const asyncThreads, uint8 const synchThreads)
{
    _connectionInfo = std::make_unique<MySQLConnectionInfo>(infoString);

    _async_threads = asyncThreads;
    _synch_threads = synchThreads;
}

template <class T>
uint32 DatabaseWorkerPool<T>::Open()
{
    WPFatal(_connectionInfo.get(), "Connection info was not set!");

    TC_LOG_INFO("sql.driver", "Opening DatabasePool '{}'. "
        "Asynchronous connections: {}, synchronous connections: {}.",
        GetDatabaseName(), _async_threads, _synch_threads);

    _ioContext = std::make_unique<Trinity::Asio::IoContext>(_async_threads);

    uint32 error = OpenConnections(IDX_ASYNC, _async_threads);

    if (error)
        return error;

    error = OpenConnections(IDX_SYNCH, _synch_threads);

    if (error)
        return error;

    for (std::unique_ptr<T> const& connection : _connections[IDX_ASYNC])
        connection->StartWorkerThread(_ioContext.get());

    TC_LOG_INFO("sql.driver", "DatabasePool '{}' opened successfully. "
        "{} total connections running.", GetDatabaseName(),
        (_connections[IDX_SYNCH].size() + _connections[IDX_ASYNC].size()));

    return 0;
}

template <class T>
void DatabaseWorkerPool<T>::Close()
{
    TC_LOG_INFO("sql.driver", "Closing down DatabasePool '{}'.", GetDatabaseName());

    if (_ioContext)
        _ioContext->stop();

    //! Closes the actualy MySQL connection.
    _connections[IDX_ASYNC].clear();

    _ioContext.reset();

    TC_LOG_INFO("sql.driver", "Asynchronous connections on DatabasePool '{}' terminated. "
                "Proceeding with synchronous connections.",
        GetDatabaseName());

    //! Shut down the synchronous connections
    //! There's no need for locking the connection, because DatabaseWorkerPool<>::Close
    //! should only be called after any other thread tasks in the core have exited,
    //! meaning there can be no concurrent access at this point.
    _connections[IDX_SYNCH].clear();

    TC_LOG_INFO("sql.driver", "All connections on DatabasePool '{}' closed.", GetDatabaseName());
}

template <class T>
bool DatabaseWorkerPool<T>::PrepareStatements()
{
    for (auto& connections : _connections)
    {
        for (auto& connection : connections)
        {
            connection->LockIfReady();
            if (!connection->PrepareStatements())
            {
                connection->Unlock();
                Close();
                return false;
            }
            else
                connection->Unlock();

            size_t const preparedSize = connection->m_stmts.size();
            if (_preparedStatementSize.size() < preparedSize)
                _preparedStatementSize.resize(preparedSize);

            for (size_t i = 0; i < preparedSize; ++i)
            {
                // already set by another connection
                // (each connection only has prepared statements of it's own type sync/async)
                if (_preparedStatementSize[i] > 0)
                    continue;

                if (MySQLPreparedStatement * stmt = connection->m_stmts[i].get())
                {
                    uint32 const paramCount = stmt->GetParameterCount();

                    // TC only supports uint8 indices.
                    ASSERT(paramCount < std::numeric_limits<uint8>::max());

                    _preparedStatementSize[i] = static_cast<uint8>(paramCount);
                }
            }
        }
    }

    return true;
}

template <class T>
QueryResult DatabaseWorkerPool<T>::Query(char const* sql, T* connection /*= nullptr*/)
{
    if (!connection)
        connection = GetFreeConnection();

    QueryResult result = BasicStatementTask::Query(connection, sql);
    connection->Unlock();

    return result;
}

template <class T>
PreparedQueryResult DatabaseWorkerPool<T>::Query(PreparedStatement<T>* stmt)
{
    T* connection = GetFreeConnection();
    PreparedQueryResult ret = PreparedStatementTask::Query(connection, stmt);
    connection->Unlock();

    //! Delete proxy-class. Not needed anymore
    delete stmt;

    return ret;
}

template <class T>
QueryCallback DatabaseWorkerPool<T>::AsyncQuery(char const* sql)
{
    std::future<QueryResult> result = boost::asio::post(_ioContext->get_executor(), boost::asio::use_future([this, sql = std::string(sql), tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        return BasicStatementTask::Query(conn, sql.c_str());
    }));
    return QueryCallback(std::move(result));
}

template <class T>
QueryCallback DatabaseWorkerPool<T>::AsyncQuery(PreparedStatement<T>* stmt)
{
    std::future<PreparedQueryResult> result = boost::asio::post(_ioContext->get_executor(), boost::asio::use_future([this, stmt = std::unique_ptr<PreparedStatement<T>>(stmt), tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        return PreparedStatementTask::Query(conn, stmt.get());
    }));
    return QueryCallback(std::move(result));
}

template <class T>
SQLQueryHolderCallback DatabaseWorkerPool<T>::DelayQueryHolder(std::shared_ptr<SQLQueryHolder<T>> holder)
{
    std::future<void> result = boost::asio::post(_ioContext->get_executor(), boost::asio::use_future([this, holder, tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        SQLQueryHolderTask::Execute(conn, holder.get());
    }));
    return { std::move(holder), std::move(result) };
}

template <class T>
SQLTransaction<T> DatabaseWorkerPool<T>::BeginTransaction()
{
    return std::make_shared<Transaction<T>>();
}

template <class T>
void DatabaseWorkerPool<T>::CommitTransaction(SQLTransaction<T> transaction)
{
#ifdef TRINITY_DEBUG
    //! Only analyze transaction weaknesses in Debug mode.
    //! Ideally we catch the faults in Debug mode and then correct them,
    //! so there's no need to waste these CPU cycles in Release mode.
    switch (transaction->GetSize())
    {
    case 0:
        TC_LOG_DEBUG("sql.driver", "Transaction contains 0 queries. Not executing.");
        return;
    case 1:
        TC_LOG_DEBUG("sql.driver", "Warning: Transaction only holds 1 query, consider removing Transaction context in code.");
        break;
    default:
        break;
    }
#endif // TRINITY_DEBUG

    boost::asio::post(_ioContext->get_executor(), [this, transaction, tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        TransactionTask::Execute(conn, transaction);
    });
}

template <class T>
TransactionCallback DatabaseWorkerPool<T>::AsyncCommitTransaction(SQLTransaction<T> transaction)
{
#ifdef TRINITY_DEBUG
    //! Only analyze transaction weaknesses in Debug mode.
    //! Ideally we catch the faults in Debug mode and then correct them,
    //! so there's no need to waste these CPU cycles in Release mode.
    switch (transaction->GetSize())
    {
        case 0:
            TC_LOG_DEBUG("sql.driver", "Transaction contains 0 queries. Not executing.");
            break;
        case 1:
            TC_LOG_DEBUG("sql.driver", "Warning: Transaction only holds 1 query, consider removing Transaction context in code.");
            break;
        default:
            break;
    }
#endif // TRINITY_DEBUG

    std::future<bool> result = boost::asio::post(_ioContext->get_executor(), boost::asio::use_future([this, transaction, tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        return TransactionTask::Execute(conn, transaction);
    }));
    return TransactionCallback(std::move(result));
}

template <class T>
void DatabaseWorkerPool<T>::DirectCommitTransaction(SQLTransaction<T>& transaction)
{
    T* connection = GetFreeConnection();
    int errorCode = connection->ExecuteTransaction(transaction);
    if (!errorCode)
    {
        connection->Unlock();      // OK, operation succesful
        return;
    }

    //! Handle MySQL Errno 1213 without extending deadlock to the core itself
    /// @todo More elegant way
    if (errorCode == ER_LOCK_DEADLOCK)
    {
        //todo: handle multiple sync threads deadlocking in a similar way as async threads
        uint8 loopBreaker = 5;
        for (uint8 i = 0; i < loopBreaker; ++i)
        {
            if (!connection->ExecuteTransaction(transaction))
                break;
        }
    }

    //! Clean up now.
    transaction->Cleanup();

    connection->Unlock();
}

template <class T>
PreparedStatement<T>* DatabaseWorkerPool<T>::GetPreparedStatement(PreparedStatementIndex index)
{
    return new PreparedStatement<T>(index, _preparedStatementSize[index]);
}

template <class T>
void DatabaseWorkerPool<T>::EscapeString(std::string& str)
{
    if (str.empty())
        return;

    char* buf = new char[str.size() * 2 + 1];
    EscapeString(buf, str.c_str(), uint32(str.size()));
    str = buf;
    delete[] buf;
}

template <class T>
void DatabaseWorkerPool<T>::KeepAlive()
{
    //! Ping synchronous connections
    for (auto& connection : _connections[IDX_SYNCH])
    {
        if (connection->LockIfReady())
        {
            connection->Ping();
            connection->Unlock();
        }
    }

    //! Assuming all worker threads are free, every worker thread will receive 1 ping operation request
    //! If one or more worker threads are busy, the ping operations will not be split evenly, but this doesn't matter
    //! as the sole purpose is to prevent connections from idling.
    auto const count = _connections[IDX_ASYNC].size();
    for (uint8 i = 0; i < count; ++i)
    {
        boost::asio::post(_ioContext->get_executor(), [this, tracker = QueueSizeTracker(this)]
        {
            T* conn = GetAsyncConnectionForCurrentThread();
            conn->Ping();
        });
    }
}

#ifdef TRINITY_DEBUG
template <class T>
void DatabaseWorkerPool<T>::WarnAboutSyncQueries([[maybe_unused]] bool warn)
{
    WarnSyncQueries<T> = warn;
}
#endif

template <class T>
uint32 DatabaseWorkerPool<T>::OpenConnections(InternalIndex type, uint8 numConnections)
{
    for (uint8 i = 0; i < numConnections; ++i)
    {
        // Create the connection
        constexpr std::array<ConnectionFlags, IDX_SIZE> flags = { { CONNECTION_ASYNC, CONNECTION_SYNCH } };

        std::unique_ptr<T> connection = std::make_unique<T>(*_connectionInfo, flags[type]);

        if (uint32 error = connection->Open())
        {
            // Failed to open a connection or invalid version, abort and cleanup
            _connections[type].clear();
            return error;
        }
        else if (uint32 serverVersion = connection->GetServerVersion(); serverVersion < ParseVersionString(TRINITY_REQUIRED_MYSQL_VERSION))
        {
            TC_LOG_ERROR("sql.driver", "TrinityCore does not support " TRINITY_MYSQL_FLAVOR " versions below " TRINITY_REQUIRED_MYSQL_VERSION " (found id {}, need id >= {}), please update your " TRINITY_MYSQL_FLAVOR " server", serverVersion, ParseVersionString(TRINITY_REQUIRED_MYSQL_VERSION));
            return 1;
        }
        else
        {
            _connections[type].push_back(std::move(connection));
        }
    }

    // Everything is fine
    return 0;
}

template <class T>
unsigned long DatabaseWorkerPool<T>::EscapeString(char* to, char const* from, unsigned long length)
{
    if (!to || !from || !length)
        return 0;

    return _connections[IDX_SYNCH].front()->EscapeString(to, from, length);
}

template <class T>
size_t DatabaseWorkerPool<T>::QueueSize() const
{
    return _queueSize;
}

template <class T>
T* DatabaseWorkerPool<T>::GetFreeConnection()
{
#ifdef TRINITY_DEBUG
    if (WarnSyncQueries<T>)
    {
        TC_LOG_WARN("sql.performances", "Sync query at:\n{}", boost::stacktrace::to_string(boost::stacktrace::stacktrace()));
    }
#endif

    uint8 i = 0;
    auto const num_cons = _connections[IDX_SYNCH].size();
    T* connection = nullptr;
    //! Block forever until a connection is free
    for (;;)
    {
        connection = _connections[IDX_SYNCH][i++ % num_cons].get();
        //! Must be matched with t->Unlock() or you will get deadlocks
        if (connection->LockIfReady())
            break;
    }

    return connection;
}

template <class T>
T* DatabaseWorkerPool<T>::GetAsyncConnectionForCurrentThread() const
{
    std::thread::id id = std::this_thread::get_id();
    for (auto&& connection : _connections[IDX_ASYNC])
        if (connection->GetWorkerThreadId() == id)
            return connection.get();

    return nullptr;
}

template <class T>
char const* DatabaseWorkerPool<T>::GetDatabaseName() const
{
    return _connectionInfo->database.c_str();
}

template <class T>
void DatabaseWorkerPool<T>::Execute(char const* sql)
{
    if (!sql)
        return;

    boost::asio::post(_ioContext->get_executor(), [this, sql = std::string(sql), tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        BasicStatementTask::Execute(conn, sql.c_str());
    });
}

template <class T>
void DatabaseWorkerPool<T>::Execute(PreparedStatement<T>* stmt)
{
    boost::asio::post(_ioContext->get_executor(), [this, stmt = std::unique_ptr<PreparedStatement<T>>(stmt), tracker = QueueSizeTracker(this)]
    {
        T* conn = GetAsyncConnectionForCurrentThread();
        PreparedStatementTask::Execute(conn, stmt.get());
    });
}

template <class T>
void DatabaseWorkerPool<T>::DirectExecute(char const* sql)
{
    if (!sql)
        return;

    T* connection = GetFreeConnection();
    BasicStatementTask::Execute(connection, sql);
    connection->Unlock();
}

template <class T>
void DatabaseWorkerPool<T>::DirectExecute(PreparedStatement<T>* stmt)
{
    T* connection = GetFreeConnection();
    PreparedStatementTask::Execute(connection, stmt);
    connection->Unlock();

    //! Delete proxy-class. Not needed anymore
    delete stmt;
}

template <class T>
void DatabaseWorkerPool<T>::ExecuteOrAppend(SQLTransaction<T>& trans, char const* sql)
{
    if (!trans)
        Execute(sql);
    else
        trans->Append(sql);
}

template <class T>
void DatabaseWorkerPool<T>::ExecuteOrAppend(SQLTransaction<T>& trans, PreparedStatement<T>* stmt)
{
    if (!trans)
        Execute(stmt);
    else
        trans->Append(stmt);
}

template class TC_DATABASE_API DatabaseWorkerPool<LoginDatabaseConnection>;
template class TC_DATABASE_API DatabaseWorkerPool<WorldDatabaseConnection>;
template class TC_DATABASE_API DatabaseWorkerPool<CharacterDatabaseConnection>;
template class TC_DATABASE_API DatabaseWorkerPool<HotfixDatabaseConnection>;