/*
 * This file is distributed as part of MaxScale.  It 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,
 * version 2.
 *
 * 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, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Copyright MariaDB Corporation Ab 2014
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dcb.h>
#include <buffer.h>
#include <gw_protocol.h>
#include <service.h>
#include <session.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <router.h>
#include <maxscale/poll.h>
#include <atomic.h>
#include <gw.h>
#include <adminusers.h>
#include <skygw_utils.h>
#include <log_manager.h>
#include <modinfo.h>
#include <maxscaled.h>

MODULE_INFO info =
{
    MODULE_API_PROTOCOL,
    MODULE_GA,
    GWPROTOCOL_VERSION,
    "A maxscale protocol for the administration interface"
};

/**
 * @file maxscaled.c - MaxScale administration protocol
 *
 *
 * @verbatim
 * Revision History
 * Date         Who                     Description
 * 13/06/2014   Mark Riddoch            Initial implementation
 * 07/07/15     Martin Brampton         Correct failure handling
 *
 * @endverbatim
 */

static char *version_str = "V1.0.0";

static int maxscaled_read_event(DCB* dcb);
static int maxscaled_write_event(DCB *dcb);
static int maxscaled_write(DCB *dcb, GWBUF *queue);
static int maxscaled_error(DCB *dcb);
static int maxscaled_hangup(DCB *dcb);
static int maxscaled_accept(DCB *dcb);
static int maxscaled_close(DCB *dcb);
static int maxscaled_listen(DCB *dcb, char *config);

/**
 * The "module object" for the maxscaled protocol module.
 */
static GWPROTOCOL MyObject =
{
    maxscaled_read_event,           /**< Read - EPOLLIN handler        */
    maxscaled_write,                /**< Write - data from gateway     */
    maxscaled_write_event,          /**< WriteReady - EPOLLOUT handler */
    maxscaled_error,                /**< Error - EPOLLERR handler      */
    maxscaled_hangup,               /**< HangUp - EPOLLHUP handler     */
    maxscaled_accept,               /**< Accept                        */
    NULL,                           /**< Connect                       */
    maxscaled_close,                /**< Close                         */
    maxscaled_listen,               /**< Create a listener             */
    NULL,                           /**< Authentication                */
    NULL                            /**< Session                       */
};

/**
 * Implementation of the mandatory version entry point
 *
 * @return version string of the module
 */
char*  version()
{
    return version_str;
}

/**
 * The module initialisation routine, called when the module
 * is first loaded.
 */
void ModuleInit()
{
    MXS_INFO("Initialise MaxScaled Protocol module.");;
}

/**
 * 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
 */
GWPROTOCOL* GetModuleObject()
{
    return &MyObject;
}

/**
 * Read event for EPOLLIN on the maxscaled protocol module.
 *
 * @param dcb   The descriptor control block
 * @return
 */
static int maxscaled_read_event(DCB* dcb)
{
    int n;
    GWBUF *head = NULL;
    SESSION *session = dcb->session;
    MAXSCALED *maxscaled = (MAXSCALED *)dcb->protocol;
    char *password;

    if ((n = dcb_read(dcb, &head, 0)) != -1)
    {
        if (head)
        {
            if (GWBUF_LENGTH(head))
            {
                switch (maxscaled->state)
                {
                case MAXSCALED_STATE_LOGIN:
                    maxscaled->username = strndup(GWBUF_DATA(head), GWBUF_LENGTH(head));
                    maxscaled->state = MAXSCALED_STATE_PASSWD;
                    dcb_printf(dcb, "PASSWORD");
                    while ((head = gwbuf_consume(head, GWBUF_LENGTH(head))) != NULL);
                    break;
                case MAXSCALED_STATE_PASSWD:
                    password = strndup(GWBUF_DATA(head), GWBUF_LENGTH(head));
                    if (admin_verify(maxscaled->username, password))
                    {
                        dcb_printf(dcb, "OK----");
                        maxscaled->state = MAXSCALED_STATE_DATA;
                    }
                    else
                    {
                        dcb_printf(dcb, "FAILED");
                        maxscaled->state = MAXSCALED_STATE_LOGIN;
                    }
                    while ((head = gwbuf_consume(head, GWBUF_LENGTH(head))) != NULL)
                    {
                        ;
                    }
                    free(password);
                    break;
                case MAXSCALED_STATE_DATA:
                    SESSION_ROUTE_QUERY(session, head);
                    dcb_printf(dcb, "OK");
                    break;
                }
            }
            else
            {
                // Force the free of the buffer header
                while ((head = gwbuf_consume(head, GWBUF_LENGTH(head))) != NULL)
                {
                    ;
                }
            }
        }
    }
    return n;
}

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

/**
 * Write routine for the maxscaled protocol module.
 *
 * Writes the content of the buffer queue to the socket
 * observing the non-blocking principles of MaxScale.
 *
 * @param dcb   Descriptor Control Block for the socket
 * @param queue Linked list of buffes to write
 */
static int maxscaled_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 maxscaled_error(DCB *dcb)
{
    return 0;
}

/**
 * Handler for the EPOLLHUP event.
 *
 * @param dcb   The descriptor control block
 */
static int maxscaled_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
 * @return The number of new connections created
 */
static int maxscaled_accept(DCB *dcb)
{
    int n_connect = 0;

    while (1)
    {
        int so;
        struct sockaddr_in addr;
        socklen_t addrlen = sizeof(struct sockaddr);
        DCB *client_dcb;
        MAXSCALED *maxscaled_pr = NULL;

        so = accept(dcb->fd, (struct sockaddr *)&addr, &addrlen);

        if (so == -1)
        {
            return n_connect;
        }
        else
        {
            atomic_add(&dcb->stats.n_accepts, 1);
            client_dcb = dcb_alloc(DCB_ROLE_REQUEST_HANDLER);
            if (client_dcb == NULL)
            {
                close(so);
                return n_connect;
            }
            client_dcb->listen_ssl = dcb->listen_ssl;
            client_dcb->fd = so;
            client_dcb->remote = strdup(inet_ntoa(addr.sin_addr));
            memcpy(&client_dcb->func, &MyObject, sizeof(GWPROTOCOL));
            if ((maxscaled_pr = (MAXSCALED *)malloc(sizeof(MAXSCALED))) == NULL)
            {
                client_dcb->protocol = NULL;
                close(so);
                dcb_close(client_dcb);
                return n_connect;
            }
            maxscaled_pr->username = NULL;
            spinlock_init(&maxscaled_pr->lock);
            client_dcb->protocol = (void *)maxscaled_pr;

            client_dcb->session = session_alloc(dcb->session->service, client_dcb);

            if (NULL == client_dcb->session || poll_add_dcb(client_dcb))
            {
                dcb_close(dcb);
                return n_connect;
            }
            n_connect++;
            maxscaled_pr->state = MAXSCALED_STATE_LOGIN;
            dcb_printf(client_dcb, "USER");
        }
    }
    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 maxscaled_close(DCB *dcb)
{
    MAXSCALED *maxscaled = dcb->protocol;

    if (!maxscaled)
    {
        return 0;
    }

    spinlock_acquire(&maxscaled->lock);
    if (maxscaled->username)
    {
        free(maxscaled->username);
        maxscaled->username = NULL;
    }
    spinlock_release(&maxscaled->lock);

    return 0;
}

/**
 * Maxscale daemon listener entry point
 *
 * @param       listener        The Listener DCB
 * @param       config          Configuration (ip:port)
 */
static int maxscaled_listen(DCB *listener, char *config)
{
    struct sockaddr_in addr;
    int one = 1;
    int rc;

    memcpy(&listener->func, &MyObject, sizeof(GWPROTOCOL));

    if (!parse_bindconfig(config, 6033, &addr))
    {
        return 0;
    }

    if ((listener->fd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
        return 0;
    }

    // socket options
    if (setsockopt(listener->fd, SOL_SOCKET, SO_REUSEADDR, (char *)&one, sizeof(one)))
    {
        MXS_ERROR("Unable to set SO_REUSEADDR on maxscale listener.");
    }
    // set NONBLOCKING mode
    setnonblocking(listener->fd);
    // bind address and port
    if (bind(listener->fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
    {
        return 0;
    }

    rc = listen(listener->fd, SOMAXCONN);

    if (rc == 0)
    {
        MXS_NOTICE("Listening maxscale connections at %s", config);
    }
    else
    {
        int eno = errno;
        errno = 0;
        char errbuf[STRERROR_BUFLEN];
        MXS_ERROR("Failed to start listening for maxscale admin connections "
                  "due error %d, %s",
                  eno, strerror_r(eno, errbuf, sizeof(errbuf)));
        return 0;
    }

    if (poll_add_dcb(listener) == -1)
    {
        return 0;
    }
    return 1;
}