/*
 * 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/bsl.
 *
 * Change Date: 2019-07-01
 *
 * 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 <query_classifier.h>
#include <log_manager.h>
#include <modules.h>
#include <modutil.h>
#include <maxscale/alloc.h>

//#define QC_TRACE_ENABLED
#undef QC_TRACE_ENABLED

#if defined(QC_TRACE_ENABLED)
#define QC_TRACE() MXS_NOTICE(__func__)
#else
#define QC_TRACE()
#endif

static const char default_qc_name[] = "qc_sqlite";

static QUERY_CLASSIFIER* classifier;


bool qc_init(const char* plugin_name, const char* plugin_args)
{
    QC_TRACE();
    ss_dassert(!classifier);

    if (!plugin_name || (*plugin_name == 0))
    {
        MXS_NOTICE("No query classifier specified, using default '%s'.", default_qc_name);
        plugin_name = default_qc_name;
    }

    bool success = false;
    classifier = qc_load(plugin_name);

    if (classifier)
    {
        success = classifier->qc_init(plugin_args);
    }

    return success;
}

void qc_end(void)
{
    QC_TRACE();
    ss_dassert(classifier);

    classifier->qc_end();
    classifier = NULL;
}

QUERY_CLASSIFIER* qc_load(const char* plugin_name)
{
    void* module = load_module(plugin_name, MODULE_QUERY_CLASSIFIER);

    if (module)
    {
        MXS_INFO("%s loaded.", plugin_name);
    }
    else
    {
        MXS_ERROR("Could not load %s.", plugin_name);
    }

    return (QUERY_CLASSIFIER*) module;
}

void qc_unload(QUERY_CLASSIFIER* classifier)
{
    // TODO: The module loading/unloading needs an overhaul before we
    // TODO: actually can unload something.
}

bool qc_thread_init(void)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_thread_init();
}

void qc_thread_end(void)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_thread_end();
}

/**
 * Parses the query in the provided buffer and returns a value specifying
 * to what extent the query could be parsed.
 *
 * There is no need to call this function explicitly before calling any of
 * the other functions; e.g. qc_get_type. When some particular property of
 * a query is asked for, the query will be parsed if it has not been parsed
 * yet. Also, if the query in the provided buffer has been parsed already
 * then this function will only return the result of that parsing; the query
 * will not be parsed again.
 *
 * @param query A GWBUF containing an SQL statement.
 * @result To what extent the query could be parsed.
 */
qc_parse_result_t qc_parse(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_parse(query);
}

/**
 * Returns a bitmask specifying the type(s) of the query.
 * The result should be tested against specific qc_query_type_t values
 * using the bitwise & operator, never using the == operator.
 *
 * @param query A buffer containing a query.
 *
 * @return A bitmask of type bits.
 */
uint32_t qc_get_type(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_get_type(query);
}

qc_query_op_t qc_get_operation(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_get_operation(query);
}

char* qc_get_created_table_name(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_get_created_table_name(query);
}

bool qc_is_drop_table_query(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_is_drop_table_query(query);
}

bool qc_is_real_query(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_is_real_query(query);
}

char** qc_get_table_names(GWBUF* query, int* tblsize, bool fullnames)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_get_table_names(query, tblsize, fullnames);
}

char* qc_get_canonical(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    char *rval;

    if (classifier->qc_get_canonical)
    {
        rval = classifier->qc_get_canonical(query);
    }
    else
    {
        rval = modutil_get_canonical(query);
    }

    if (rval)
    {
        squeeze_whitespace(rval);
    }

    return rval;
}

bool qc_query_has_clause(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_query_has_clause(query);
}

/**
 * Generate a string of query type value.
 * Caller must free the memory of the resulting string.
 *
 * @param   qtype   Query type value, combination of values listed in
 *                  query_classifier.h
 *
 * @return  string representing the query type value
 */
char* qc_get_qtype_str(qc_query_type_t qtype)
{
    QC_TRACE();
    int t1 = (int) qtype;
    int t2 = 1;
    qc_query_type_t t = QUERY_TYPE_UNKNOWN;
    char* qtype_str = NULL;

    /**
     * Test values (bits) and clear matching bits from t1 one by one until
     * t1 is completely cleared.
     */
    while (t1 != 0)
    {
        if (t1 & t2)
        {
            t = (qc_query_type_t) t2;

            if (qtype_str == NULL)
            {
                qtype_str = MXS_STRDUP_A(STRQTYPE(t));
            }
            else
            {
                size_t len = strlen(STRQTYPE(t));
                /** reallocate space for delimiter, new string and termination */
                qtype_str = (char *) MXS_REALLOC(qtype_str, strlen(qtype_str) + 1 + len + 1);
                MXS_ABORT_IF_NULL(qtype_str);
                snprintf(qtype_str + strlen(qtype_str), 1 + len + 1, "|%s", STRQTYPE(t));
            }

            /** Remove found value from t1 */
            t1 &= ~t2;
        }

        t2 <<= 1;
    }

    return qtype_str;
}

char* qc_get_affected_fields(GWBUF* query)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_get_affected_fields(query);
}

char** qc_get_database_names(GWBUF* query, int* sizep)
{
    QC_TRACE();
    ss_dassert(classifier);

    return classifier->qc_get_database_names(query, sizep);
}

/**
 * Returns the string representation of a query operation.
 *
 * @param op An operation.
 * @return The corresponding string.
 *         NOTE: The returned string is statically allocated
 *               and must *not* be freed.
 */
const char* qc_op_to_string(qc_query_op_t op)
{
    switch (op)
    {
    case QUERY_OP_UNDEFINED:
	return "QUERY_OP_UNDEFINED";

    case QUERY_OP_SELECT:
	return "QUERY_OP_SELECT";

    case QUERY_OP_UPDATE:
	return "QUERY_OP_UPDATE";

    case QUERY_OP_INSERT:
	return "QUERY_OP_INSERT";

    case QUERY_OP_DELETE:
	return "QUERY_OP_DELETE";

    case QUERY_OP_TRUNCATE:
	return "QUERY_OP_TRUNCATE";

    case QUERY_OP_ALTER:
	return "QUERY_OP_ALTER";

    case QUERY_OP_CREATE:
	return "QUERY_OP_CREATE";

    case QUERY_OP_DROP:
	return "QUERY_OP_DROP";

    case QUERY_OP_CHANGE_DB:
	return "QUERY_OP_CHANGE_DB";

    case QUERY_OP_LOAD:
	return "QUERY_OP_LOAD";

    case QUERY_OP_GRANT:
	return "QUERY_OP_GRANT";

    case QUERY_OP_REVOKE:
	return "QUERY_OP_REVOKE";

    default:
        return "UNKNOWN_QUERY_OP";
    }
}

struct type_name_info
{
    const char* name;
    size_t name_len;
};

struct type_name_info type_to_type_name_info(qc_query_type_t type)
{
    struct type_name_info info;

    switch (type)
    {
    case QUERY_TYPE_UNKNOWN:
        {
            static const char name[] = "QUERY_TYPE_UNKNOWN";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_LOCAL_READ:
        {
            static const char name[] = "QUERY_TYPE_LOCAL_READ";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_READ:
        {
            static const char name[] = "QUERY_TYPE_READ";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_WRITE:
        {
            static const char name[] = "QUERY_TYPE_WRITE";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_MASTER_READ:
        {
            static const char name[] = "QUERY_TYPE_MASTER_READ";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_SESSION_WRITE:
        {
            static const char name[] = "QUERY_TYPE_SESSION_WRITE";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

        /** Not implemented yet */
        //case QUERY_TYPE_USERVAR_WRITE:
    case QUERY_TYPE_USERVAR_READ:
        {
            static const char name[] = "QUERY_TYPE_USERVAR_READ";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_SYSVAR_READ:
        {
            static const char name[] = "QUERY_TYPE_SYSVAR_READ";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

        /** Not implemented yet */
        //case QUERY_TYPE_SYSVAR_WRITE:
    case QUERY_TYPE_GSYSVAR_READ:
        {
            static const char name[] = "QUERY_TYPE_GSYSVAR_READ";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_GSYSVAR_WRITE:
        {
            static const char name[] = "QUERY_TYPE_GSYSVAR_WRITE";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_BEGIN_TRX:
        {
            static const char name[] = "QUERY_TYPE_BEGIN_TRX";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_ENABLE_AUTOCOMMIT:
        {
            static const char name[] = "QUERY_TYPE_ENABLE_AUTOCOMMIT";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_DISABLE_AUTOCOMMIT:
        {
            static const char name[] = "QUERY_TYPE_DISABLE_AUTOCOMMIT";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_ROLLBACK:
        {
            static const char name[] = "QUERY_TYPE_ROLLBACK";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_COMMIT:
        {
            static const char name[] = "QUERY_TYPE_COMMIT";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_PREPARE_NAMED_STMT:
        {
            static const char name[] = "QUERY_TYPE_PREPARE_NAMED_STMT";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_PREPARE_STMT:
        {
            static const char name[] = "QUERY_TYPE_PREPARE_STMT";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_EXEC_STMT:
        {
            static const char name[] = "QUERY_TYPE_EXEC_STMT";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_CREATE_TMP_TABLE:
        {
            static const char name[] = "QUERY_TYPE_CREATE_TMP_TABLE";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_READ_TMP_TABLE:
        {
            static const char name[] = "QUERY_TYPE_READ_TMP_TABLE";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_SHOW_DATABASES:
        {
            static const char name[] = "QUERY_TYPE_SHOW_DATABASES";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    case QUERY_TYPE_SHOW_TABLES:
        {
            static const char name[] = "QUERY_TYPE_SHOW_TABLES";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;

    default:
        {
            static const char name[] = "UNKNOWN_QUERY_TYPE";
            info.name = name;
            info.name_len = sizeof(name) - 1;
	}
	break;
    }

    return info;
}



/**
 * Returns the string representation of a query type.
 *
 * @param type A specific type (not a bitmask of several).
 * @return The corresponding string.
 *         NOTE: The returned string is statically allocated
 *               and must *not* be freed.
 */
const char* qc_type_to_string(qc_query_type_t type)
{
    return type_to_type_name_info(type).name;
}

static const qc_query_type_t QUERY_TYPES[] =
{
    /* Excluded by design */
    //QUERY_TYPE_UNKNOWN,
    QUERY_TYPE_LOCAL_READ,
    QUERY_TYPE_READ,
    QUERY_TYPE_WRITE,
    QUERY_TYPE_MASTER_READ,
    QUERY_TYPE_SESSION_WRITE,
    /** Not implemented yet */
    //QUERY_TYPE_USERVAR_WRITE,
    QUERY_TYPE_USERVAR_READ,
    QUERY_TYPE_SYSVAR_READ,
    /** Not implemented yet */
    //QUERY_TYPE_SYSVAR_WRITE,
    QUERY_TYPE_GSYSVAR_READ,
    QUERY_TYPE_GSYSVAR_WRITE,
    QUERY_TYPE_BEGIN_TRX,
    QUERY_TYPE_ENABLE_AUTOCOMMIT,
    QUERY_TYPE_DISABLE_AUTOCOMMIT,
    QUERY_TYPE_ROLLBACK,
    QUERY_TYPE_COMMIT,
    QUERY_TYPE_PREPARE_NAMED_STMT,
    QUERY_TYPE_PREPARE_STMT,
    QUERY_TYPE_EXEC_STMT,
    QUERY_TYPE_CREATE_TMP_TABLE,
    QUERY_TYPE_READ_TMP_TABLE,
    QUERY_TYPE_SHOW_DATABASES,
    QUERY_TYPE_SHOW_TABLES,
};

static const int N_QUERY_TYPES = sizeof(QUERY_TYPES) / sizeof(QUERY_TYPES[0]);
static const int QUERY_TYPE_MAX_LEN = 29; // strlen("QUERY_TYPE_PREPARE_NAMED_STMT");

/**
 * Returns the string representation of a bitmask of query types.
 *
 * @param type Bitmask of several qc_query_type_t values.
 * @return The corresponding string.
 *         NOTE: The returned string is dynamically allocated
 *               and *must* be freed by the caller.
 */
char* qc_types_to_string(uint32_t types)
{
    int len = 0;

    // First calculate how much space will be needed.
    for (int i = 0; i < N_QUERY_TYPES; ++i)
    {
        if (types & QUERY_TYPES[i])
        {
            if (len != 0)
            {
                ++len; // strlen("|");
            }

            len += QUERY_TYPE_MAX_LEN;
        }
    }

    ++len;

    // Then make one allocation and build the string.
    char* s = (char*) MXS_MALLOC(len);

    if (s)
    {
        if (len > 1)
        {
            char* p = s;

            for (int i = 0; i < N_QUERY_TYPES; ++i)
            {
                qc_query_type_t type = QUERY_TYPES[i];

                if (types & type)
                {
                    if (p != s)
                    {
                        strcpy(p, "|");
                        ++p;
                    }

                    struct type_name_info info = type_to_type_name_info(type);

                    strcpy(p, info.name);
                    p += info.name_len;
                }
            }
        }
        else
        {
            *s = 0;
        }
    }

    return s;
}