/*
 * Copyright (c) 2016 MariaDB Corporation Ab
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
 *
 * Change Date: 2020-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2 or later of the General
 * Public License.
 */

#include <maxscale/queryclassifier.hh>
#include <maxscale/query_classifier.h>
#include <maxscale/protocol/mysql.h>

namespace maxscale
{

QueryClassifier::QueryClassifier(MXS_SESSION* pSession,
                                 mxs_target_t use_sql_variables_in)
    : m_pSession(pSession)
    , m_use_sql_variables_in(use_sql_variables_in)
    , m_load_data_state(LOAD_DATA_INACTIVE)
    , m_have_tmp_tables(false)
    , m_large_query(false)
{
}

uint32_t QueryClassifier::get_route_target(uint8_t command, uint32_t qtype)
{
    bool trx_active = session_trx_is_active(m_pSession);
    uint32_t target = TARGET_UNDEFINED;
    bool load_active = (m_load_data_state != LOAD_DATA_INACTIVE);

    /**
     * Prepared statements preparations should go to all servers
     */
    if (qc_query_is_type(qtype, QUERY_TYPE_PREPARE_STMT) ||
        qc_query_is_type(qtype, QUERY_TYPE_PREPARE_NAMED_STMT) ||
        command == MXS_COM_STMT_CLOSE ||
        command == MXS_COM_STMT_RESET)
    {
        target = TARGET_ALL;
    }
    /**
     * These queries should be routed to all servers
     */
    else if (!load_active &&
             (qc_query_is_type(qtype, QUERY_TYPE_SESSION_WRITE) ||
              /** Configured to allow writing user variables to all nodes */
              (m_use_sql_variables_in == TYPE_ALL &&
               qc_query_is_type(qtype, QUERY_TYPE_USERVAR_WRITE)) ||
              qc_query_is_type(qtype, QUERY_TYPE_GSYSVAR_WRITE) ||
              /** enable or disable autocommit are always routed to all */
              qc_query_is_type(qtype, QUERY_TYPE_ENABLE_AUTOCOMMIT) ||
              qc_query_is_type(qtype, QUERY_TYPE_DISABLE_AUTOCOMMIT)))
    {
        /**
         * This is problematic query because it would be routed to all
         * backends but since this is SELECT that is not possible:
         * 1. response set is not handled correctly in clientReply and
         * 2. multiple results can degrade performance.
         *
         * Prepared statements are an exception to this since they do not
         * actually do anything but only prepare the statement to be used.
         * They can be safely routed to all backends since the execution
         * is done later.
         *
         * With prepared statement caching the task of routing
         * the execution of the prepared statements to the right server would be
         * an easy one. Currently this is not supported.
         */
        if (qc_query_is_type(qtype, QUERY_TYPE_READ))
        {
            MXS_WARNING("The query can't be routed to all "
                        "backend servers because it includes SELECT and "
                        "SQL variable modifications which is not supported. "
                        "Set use_sql_variables_in=master or split the "
                        "query to two, where SQL variable modifications "
                        "are done in the first and the SELECT in the "
                        "second one.");

            target = TARGET_MASTER;
        }
        target |= TARGET_ALL;
    }
    /**
     * Hints may affect on routing of the following queries
     */
    else if (!trx_active && !load_active &&
             !qc_query_is_type(qtype, QUERY_TYPE_MASTER_READ) &&
             !qc_query_is_type(qtype, QUERY_TYPE_WRITE) &&
             (qc_query_is_type(qtype, QUERY_TYPE_READ) ||
              qc_query_is_type(qtype, QUERY_TYPE_SHOW_TABLES) ||
              qc_query_is_type(qtype, QUERY_TYPE_USERVAR_READ) ||
              qc_query_is_type(qtype, QUERY_TYPE_SYSVAR_READ) ||
              qc_query_is_type(qtype, QUERY_TYPE_GSYSVAR_READ)))
    {
        if (qc_query_is_type(qtype, QUERY_TYPE_USERVAR_READ))
        {
            if (m_use_sql_variables_in == TYPE_ALL)
            {
                target = TARGET_SLAVE;
            }
        }
        else if (qc_query_is_type(qtype, QUERY_TYPE_READ) || // Normal read
                 qc_query_is_type(qtype, QUERY_TYPE_SHOW_TABLES) || // SHOW TABLES
                 qc_query_is_type(qtype, QUERY_TYPE_SYSVAR_READ) || // System variable
                 qc_query_is_type(qtype, QUERY_TYPE_GSYSVAR_READ)) // Global system variable
        {
            target = TARGET_SLAVE;
        }

        /** If nothing matches then choose the master */
        if ((target & (TARGET_ALL | TARGET_SLAVE | TARGET_MASTER)) == 0)
        {
            target = TARGET_MASTER;
        }
    }
    else if (session_trx_is_read_only(m_pSession))
    {
        /* Force TARGET_SLAVE for READ ONLY transaction (active or ending) */
        target = TARGET_SLAVE;
    }
    else
    {
        ss_dassert(trx_active || load_active ||
                   (qc_query_is_type(qtype, QUERY_TYPE_WRITE) ||
                    qc_query_is_type(qtype, QUERY_TYPE_MASTER_READ) ||
                    qc_query_is_type(qtype, QUERY_TYPE_SESSION_WRITE) ||
                    (qc_query_is_type(qtype, QUERY_TYPE_USERVAR_READ) &&
                     m_use_sql_variables_in == TYPE_MASTER) ||
                    (qc_query_is_type(qtype, QUERY_TYPE_SYSVAR_READ) &&
                     m_use_sql_variables_in == TYPE_MASTER) ||
                    (qc_query_is_type(qtype, QUERY_TYPE_GSYSVAR_READ) &&
                     m_use_sql_variables_in == TYPE_MASTER) ||
                    (qc_query_is_type(qtype, QUERY_TYPE_GSYSVAR_WRITE) &&
                     m_use_sql_variables_in == TYPE_MASTER) ||
                    (qc_query_is_type(qtype, QUERY_TYPE_USERVAR_WRITE) &&
                     m_use_sql_variables_in == TYPE_MASTER) ||
                    qc_query_is_type(qtype, QUERY_TYPE_BEGIN_TRX) ||
                    qc_query_is_type(qtype, QUERY_TYPE_ENABLE_AUTOCOMMIT) ||
                    qc_query_is_type(qtype, QUERY_TYPE_DISABLE_AUTOCOMMIT) ||
                    qc_query_is_type(qtype, QUERY_TYPE_ROLLBACK) ||
                    qc_query_is_type(qtype, QUERY_TYPE_COMMIT) ||
                    qc_query_is_type(qtype, QUERY_TYPE_EXEC_STMT) ||
                    qc_query_is_type(qtype, QUERY_TYPE_CREATE_TMP_TABLE) ||
                    qc_query_is_type(qtype, QUERY_TYPE_READ_TMP_TABLE) ||
                    qc_query_is_type(qtype, QUERY_TYPE_UNKNOWN)) ||
                   qc_query_is_type(qtype, QUERY_TYPE_EXEC_STMT));

        target = TARGET_MASTER;
    }

    return target;
}

}