/*
 * 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.
 */

/**
 * @file cdc.c - Change Data Capture Listener protocol module
 *
 * The change data capture protocol module is intended as a mechanism to allow connections
 * into maxscale for the purpose of accessing information within
 * the maxscale with a Change Data Capture API interface (supporting Avro right now)
 * databases.
 *
 * In the first instance it is intended to connect, authenticate and retieve data in the Avro format
 * as requested by compatible clients.
 *
 * @verbatim
 * Revision History
 * Date     Who         Description
 * 11/01/2016   Massimiliano Pinto  Initial implementation
 *
 * @endverbatim
 */

#define MXS_MODULE_NAME "CDC"

#include <cdc.h>
#include <maxscale/alloc.h>
#include <maxscale/modinfo.h>
#include <maxscale/log_manager.h>
#include <maxscale/protocol.h>
#include <maxscale/modinfo.h>
#include <maxscale/poll.h>

#define ISspace(x) isspace((int)(x))
#define CDC_SERVER_STRING "MaxScale(c) v.1.0.0"

static int cdc_read_event(DCB* dcb);
static int cdc_write_event(DCB *dcb);
static int cdc_write(DCB *dcb, GWBUF *queue);
static int cdc_error(DCB *dcb);
static int cdc_hangup(DCB *dcb);
static int cdc_accept(DCB *dcb);
static int cdc_close(DCB *dcb);
static int cdc_listen(DCB *dcb, char *config);
static CDC_protocol *cdc_protocol_init(DCB* dcb);
static void cdc_protocol_done(DCB* dcb);
static int do_auth(DCB *dcb, GWBUF *buffer, void *data);
static void write_auth_ack(DCB *dcb);
static void write_auth_err(DCB *dcb);

static char* cdc_default_auth()
{
    return "CDCPlainAuth";
}

/**
 * The module entry point routine. It is this routine that
 * must populate the structure that is referred to as the
 * "module object", this is a structure with the set of
 * external entry points for this module.
 *
 * @return The module object
 */
MXS_MODULE* MXS_CREATE_MODULE()
{
    static MXS_PROTOCOL MyObject =
    {
        cdc_read_event, /* Read - EPOLLIN handler        */
        cdc_write, /* Write - data from gateway     */
        cdc_write_event, /* WriteReady - EPOLLOUT handler */
        cdc_error, /* Error - EPOLLERR handler      */
        cdc_hangup, /* HangUp - EPOLLHUP handler     */
        cdc_accept, /* Accept                        */
        NULL, /* Connect                       */
        cdc_close, /* Close                         */
        cdc_listen, /* Create a listener             */
        NULL, /* Authentication                */
        NULL, /* Session                       */
        cdc_default_auth /* default authentication */
    };

    static MXS_MODULE info =
    {
        MXS_MODULE_API_PROTOCOL,
        MXS_MODULE_IN_DEVELOPMENT,
        MXS_PROTOCOL_VERSION,
        "A Change Data Capture Listener implementation for use in binlog events retrieval",
        "V1.0.0",
        &MyObject,
        NULL, /* Process init. */
        NULL, /* Process finish. */
        NULL, /* Thread init. */
        NULL, /* Thread finish. */
        {
            {MXS_END_MODULE_PARAMS}
        }
    };

    return &info;
}

/**
 * Read event for EPOLLIN on the CDC protocol module.
 *
 * @param dcb    The descriptor control block
 * @return
 */
static int
cdc_read_event(DCB* dcb)
{
    MXS_SESSION *session = dcb->session;
    CDC_protocol *protocol = (CDC_protocol *) dcb->protocol;
    int n, auth_val, rc = 0;
    GWBUF *head = NULL;
    CDC_session *client_data = (CDC_session *) dcb->data;

    if ((n = dcb_read(dcb, &head, 0))  > 0)
    {
        switch (protocol->state)
        {
        case CDC_STATE_WAIT_FOR_AUTH:
            if (CDC_STATE_AUTH_OK == (
                    /* Fill CDC_session from incoming packet */
                    auth_val = dcb->authfunc.extract(dcb, head)))
            {
                /* Call protocol authentication */
                auth_val = dcb->authfunc.authenticate(dcb);
            }

            /* Discard input buffer */
            gwbuf_free(head);

            if (auth_val == CDC_STATE_AUTH_OK)
            {
                /* start a real session */
                session = session_alloc(dcb->service, dcb);

                if (session != NULL)
                {
                    protocol->state = CDC_STATE_HANDLE_REQUEST;

                    write_auth_ack(dcb);

                    MXS_INFO("%s: Client [%s] authenticated with user [%s]",
                             dcb->service->name, dcb->remote != NULL ? dcb->remote : "",
                             client_data->user);
                }
                else
                {
                    auth_val = CDC_STATE_AUTH_NO_SESSION;
                }
            }

            if (auth_val != CDC_STATE_AUTH_OK)
            {
                protocol->state = CDC_STATE_AUTH_ERR;

                write_auth_err(dcb);
                MXS_ERROR("%s: authentication failure from [%s], user [%s]",
                          dcb->service->name, dcb->remote != NULL ? dcb->remote : "",
                          client_data->user);

                /* force the client connection close */
                dcb_close(dcb);

            }
            break;

        case CDC_STATE_HANDLE_REQUEST:
            // handle CLOSE command, it shoudl be routed as well and client connection closed after last transmission
            if (strncmp((char*)GWBUF_DATA(head), "CLOSE", GWBUF_LENGTH(head)) == 0)
            {
                MXS_INFO("%s: Client [%s] has requested CLOSE action",
                         dcb->service->name, dcb->remote != NULL ? dcb->remote : "");

                // gwbuf_set_type(head, GWBUF_TYPE_CDC);
                // the router will close the client connection
                //rc = MXS_SESSION_ROUTE_QUERY(session, head);

                // buffer not handled by router right now, consume it
                gwbuf_free(head);

                /* right now, just force the client connection close */
                dcb_close(dcb);
            }
            else
            {
                MXS_INFO("%s: Client [%s] requested [%.*s] action",
                         dcb->service->name, dcb->remote != NULL ? dcb->remote : "",
                         (int)GWBUF_LENGTH(head), (char*)GWBUF_DATA(head));

                // gwbuf_set_type(head, GWBUF_TYPE_CDC);
                rc = MXS_SESSION_ROUTE_QUERY(session, head);
            }
            break;

        default:
            MXS_INFO("%s: Client [%s] in unknown state %d", dcb->service->name,
                     dcb->remote != NULL ? dcb->remote : "", protocol->state);
            gwbuf_free(head);

            break;
        }
    }

    return rc;
}

/**
 * EPOLLOUT handler for the CDC protocol module.
 *
 * @param dcb    The descriptor control block
 * @return
 */
static int
cdc_write_event(DCB *dcb)
{
    return dcb_drain_writeq(dcb);
}

/**
 * Write routine for the CDC protocol module.
 *
 * Writes the content of the buffer queue to the socket
 * observing the non-blocking principles of the gateway.
 *
 * @param dcb   Descriptor Control Block for the socket
 * @param queue Linked list of buffes to write
 */
static int
cdc_write(DCB *dcb, GWBUF *queue)
{
    int rc;
    rc = dcb_write(dcb, queue);
    return rc;
}

/**
 * Handler for the EPOLLERR event.
 *
 * @param dcb    The descriptor control block
 */
static int
cdc_error(DCB *dcb)
{
    dcb_close(dcb);
    return 0;
}

/**
 * Handler for the EPOLLHUP event.
 *
 * @param dcb    The descriptor control block
 */
static int
cdc_hangup(DCB *dcb)
{
    dcb_close(dcb);
    return 0;
}

/**
 * Handler for the EPOLLIN event when the DCB refers to the listening
 * socket for the protocol.
 *
 * @param dcb    The descriptor control block
 */
static int
cdc_accept(DCB *listener)
{
    int n_connect = 0;
    DCB *client_dcb;

    while ((client_dcb = dcb_accept(listener)) != NULL)
    {
        CDC_session *client_data = NULL;
        CDC_protocol *protocol = NULL;

        /* allocating CDC protocol */
        protocol = cdc_protocol_init(client_dcb);
        if (protocol == NULL)
        {
            client_dcb->protocol = NULL;
            dcb_close(client_dcb);
            continue;
        }

        client_dcb->protocol = (CDC_protocol *) protocol;

        /* Dummy session */
        client_dcb->session = session_set_dummy(client_dcb);

        if (NULL == client_dcb->session || poll_add_dcb(client_dcb))
        {
            dcb_close(client_dcb);
            continue;
        }

        /* create the session data for CDC */
        /* this coud be done in anothe routine, let's keep it here for now */
        client_data = (CDC_session *) MXS_CALLOC(1, sizeof(CDC_session));
        if (client_data == NULL)
        {
            dcb_close(client_dcb);
            continue;
        }

        client_dcb->data = client_data;

        /* client protocol state change to CDC_STATE_WAIT_FOR_AUTH */
        protocol->state = CDC_STATE_WAIT_FOR_AUTH;

        MXS_NOTICE("%s: new connection from [%s]", client_dcb->service->name,
                   client_dcb->remote != NULL ? client_dcb->remote : "");

        n_connect++;
    }

    return n_connect;
}

/**
 * The close handler for the descriptor. Called by the gateway to
 * explicitly close a connection.
 *
 * @param dcb   The descriptor control block
 */
static int
cdc_close(DCB *dcb)
{
    CDC_protocol *p = (CDC_protocol *) dcb->protocol;

    if (!p)
    {
        return 0;
    }

    /* Add deallocate protocol items*/
    cdc_protocol_done(dcb);

    return 1;
}

/**
 * CDC protocol listener entry point
 *
 * @param   listener    The Listener DCB
 * @param   config      Configuration (ip:port)
 */
static int
cdc_listen(DCB *listener, char *config)
{
    return (dcb_listen(listener, config, "CDC") < 0) ? 0 : 1;
}

/**
 * Allocate a new CDC protocol structure
 *
 * @param  dcb    The DCB where protocol is added
 * @return        New allocated protocol or NULL on errors
 *
 */
static CDC_protocol *
cdc_protocol_init(DCB* dcb)
{
    CDC_protocol* p;

    p = (CDC_protocol *) MXS_CALLOC(1, sizeof(CDC_protocol));

    if (p == NULL)
    {
        return NULL;
    }

    p->state = CDC_ALLOC;

    spinlock_init(&p->lock);

    /* memory allocation here */
    p->state = CDC_STATE_WAIT_FOR_AUTH;

#ifdef SS_DEBUG
    p->protocol_chk_tail = p->protocol_chk_top = CHK_NUM_PROTOCOL;
#endif

    CHK_PROTOCOL(p);

    return p;
}

/**
 * Free resources in CDC protocol
 *
 * @param dcb    DCB with allocateid protocol
 *
 */
static void
cdc_protocol_done(DCB* dcb)
{
    CDC_protocol* p = (CDC_protocol *) dcb->protocol;

    if (!p)
    {
        return;
    }

    p = (CDC_protocol *) dcb->protocol;

    spinlock_acquire(&p->lock);

    /* deallocate memory here */

    p->state = CDC_STATE_CLOSE;

    spinlock_release(&p->lock);
}

/**
 * Writes Authentication ACK, success
 *
 * @param dcb    Current client DCB
 *
 */
static void
write_auth_ack(DCB *dcb)
{
    dcb_printf(dcb, "OK\n");
}

/**
 * Writes Authentication ERROR
 *
 * @param dcb    Current client DCB
 *
 */
static void
write_auth_err(DCB *dcb)
{
    dcb_printf(dcb, "ERROR: Authentication failed\n");
}