/*
   Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com>
   This file is part of GlusterFS.

   This file is licensed to you under your choice of the GNU Lesser
   General Public License, version 3 or any later version (LGPLv3 or
   later), or the GNU General Public License, version 2 (GPLv2), in all
   cases as published by the Free Software Foundation.
*/

#include "changelog-ev-handle.h"
#include "changelog-rpc-common.h"
#include "changelog-helpers.h"

struct rpc_clnt_program changelog_ev_program;

#define NR_IOVEC (MAX_IOVEC - 3)
struct ev_rpc_vec {
    int count;
    struct iovec vector[NR_IOVEC];

    /* sequence number */
    unsigned long seq;
};

struct ev_rpc {
    rbuf_list_t *rlist;
    struct rpc_clnt *rpc;
    struct ev_rpc_vec vec;
};

/**
 * As of now this just does the minimal (retval logging). Going further
 * un-acknowledges sequence numbers can be retransmitted and other
 * intelligence can be built into the server.
 */
int
changelog_event_dispatch_cbk(struct rpc_req *req, struct iovec *iov, int count,
                             void *myframe)
{
    return 0;
}

/* dispatcher RPC */
int
changelog_dispatch_vec(call_frame_t *frame, xlator_t *this,
                       struct rpc_clnt *rpc, struct ev_rpc_vec *vec)
{
    struct timeval tv = {
        0,
    };
    changelog_event_req req = {
        0,
    };

    (void)gettimeofday(&tv, NULL);

    /**
     * Event dispatch RPC header contains a sequence number for each
     * dispatch. This allows the receiver to order the request before
     * processing.
     */
    req.seq = vec->seq;
    req.tv_sec = tv.tv_sec;
    req.tv_usec = tv.tv_usec;

    return changelog_rpc_sumbit_req(
        rpc, (void *)&req, frame, &changelog_ev_program,
        CHANGELOG_REV_PROC_EVENT, vec->vector, vec->count, NULL, this,
        changelog_event_dispatch_cbk, (xdrproc_t)xdr_changelog_event_req);
}

int
changelog_event_dispatch_rpc(call_frame_t *frame, xlator_t *this, void *data)
{
    int idx = 0;
    int count = 0;
    int ret = 0;
    unsigned long sequence = 0;
    rbuf_iovec_t *rvec = NULL;
    struct ev_rpc *erpc = NULL;
    struct rlist_iter riter = {
        {
            0,
        },
    };

    /* dispatch NR_IOVEC IO vectors at a time. */

    erpc = data;
    sequence = erpc->rlist->seq[0];

    rlist_iter_init(&riter, erpc->rlist);

    rvec_for_each_entry(rvec, &riter)
    {
        idx = count % NR_IOVEC;
        if (++count == NR_IOVEC) {
            erpc->vec.vector[idx] = rvec->iov;
            erpc->vec.seq = sequence++;
            erpc->vec.count = NR_IOVEC;

            ret = changelog_dispatch_vec(frame, this, erpc->rpc, &erpc->vec);
            if (ret)
                break;
            count = 0;
            continue;
        }

        erpc->vec.vector[idx] = rvec->iov;
    }

    if (ret)
        goto error_return;

    idx = count % NR_IOVEC;
    if (idx) {
        erpc->vec.seq = sequence;
        erpc->vec.count = idx;

        ret = changelog_dispatch_vec(frame, this, erpc->rpc, &erpc->vec);
    }

error_return:
    return ret;
}

int
changelog_rpc_notify(struct rpc_clnt *rpc, void *mydata, rpc_clnt_event_t event,
                     void *data)
{
    xlator_t *this = NULL;
    changelog_rpc_clnt_t *crpc = NULL;
    changelog_clnt_t *c_clnt = NULL;
    changelog_priv_t *priv = NULL;
    changelog_ev_selector_t *selection = NULL;
    uint64_t clntcnt = 0;
    uint64_t xprtcnt = 0;

    crpc = mydata;
    this = crpc->this;
    c_clnt = crpc->c_clnt;

    priv = this->private;

    switch (event) {
        case RPC_CLNT_CONNECT:
            selection = &priv->ev_selection;
            GF_ATOMIC_INC(priv->clntcnt);

            LOCK(&c_clnt->wait_lock);
            {
                LOCK(&c_clnt->active_lock);
                {
                    changelog_select_event(this, selection, crpc->filter);
                    list_move_tail(&crpc->list, &c_clnt->active);
                }
                UNLOCK(&c_clnt->active_lock);
            }
            UNLOCK(&c_clnt->wait_lock);

            break;
        case RPC_CLNT_DISCONNECT:
            rpc_clnt_disable(crpc->rpc);

            /* rpc_clnt_disable doesn't unref the rpc. It just marks
             * the rpc as disabled and cancels reconnection timer.
             * Hence unref the rpc object to free it.
             */
            rpc_clnt_unref(crpc->rpc);

            if (priv)
                selection = &priv->ev_selection;

            LOCK(&crpc->lock);
            {
                if (selection)
                    changelog_deselect_event(this, selection, crpc->filter);
                changelog_set_disconnect_flag(crpc, _gf_true);
            }
            UNLOCK(&crpc->lock);
            LOCK(&c_clnt->active_lock);
            {
                list_del_init(&crpc->list);
            }
            UNLOCK(&c_clnt->active_lock);

            break;
        case RPC_CLNT_MSG:
        case RPC_CLNT_DESTROY:
            /* Free up mydata */
            changelog_rpc_clnt_unref(crpc);
            clntcnt = GF_ATOMIC_DEC(priv->clntcnt);
            xprtcnt = GF_ATOMIC_GET(priv->xprtcnt);
            if (this->cleanup_starting) {
                if (!clntcnt && !xprtcnt)
                    changelog_process_cleanup_event(this);
            }
            break;
        case RPC_CLNT_PING:
            break;
    }

    return 0;
}

void *
changelog_ev_connector(void *data)
{
    xlator_t *this = NULL;
    changelog_clnt_t *c_clnt = NULL;
    changelog_rpc_clnt_t *crpc = NULL;

    c_clnt = data;
    this = c_clnt->this;

    while (1) {
        pthread_mutex_lock(&c_clnt->pending_lock);
        {
            while (list_empty(&c_clnt->pending))
                pthread_cond_wait(&c_clnt->pending_cond, &c_clnt->pending_lock);
            crpc = list_first_entry(&c_clnt->pending, changelog_rpc_clnt_t,
                                    list);
            crpc->rpc = changelog_rpc_client_init(this, crpc, crpc->sock,
                                                  changelog_rpc_notify);
            if (!crpc->rpc) {
                gf_smsg(this->name, GF_LOG_ERROR, 0,
                        CHANGELOG_MSG_RPC_CONNECT_ERROR,
                        "failed to connect back", "path=%s", crpc->sock, NULL);
                crpc->cleanup(crpc);
                goto mutex_unlock;
            }

            LOCK(&c_clnt->wait_lock);
            {
                list_move_tail(&crpc->list, &c_clnt->waitq);
            }
            UNLOCK(&c_clnt->wait_lock);
        }
    mutex_unlock:
        pthread_mutex_unlock(&c_clnt->pending_lock);
    }

    return NULL;
}

void
changelog_ev_cleanup_connections(xlator_t *this, changelog_clnt_t *c_clnt)
{
    changelog_rpc_clnt_t *crpc = NULL;

    /* cleanup active connections */
    LOCK(&c_clnt->active_lock);
    {
        list_for_each_entry(crpc, &c_clnt->active, list)
        {
            rpc_clnt_disable(crpc->rpc);
        }
    }
    UNLOCK(&c_clnt->active_lock);
}

/**
 * TODO: granularize lock
 *
 * If we have multiple threads dispatching events, doing it this way is
 * a performance bottleneck.
 */

static changelog_rpc_clnt_t *
get_client(changelog_clnt_t *c_clnt, struct list_head **next)
{
    changelog_rpc_clnt_t *crpc = NULL;

    LOCK(&c_clnt->active_lock);
    {
        if (*next == &c_clnt->active)
            goto unblock;
        crpc = list_entry(*next, changelog_rpc_clnt_t, list);
        /* ref rpc as DISCONNECT might unref the rpc asynchronously */
        changelog_rpc_clnt_ref(crpc);
        rpc_clnt_ref(crpc->rpc);
        *next = (*next)->next;
    }
unblock:
    UNLOCK(&c_clnt->active_lock);

    return crpc;
}

static void
put_client(changelog_clnt_t *c_clnt, changelog_rpc_clnt_t *crpc)
{
    LOCK(&c_clnt->active_lock);
    {
        rpc_clnt_unref(crpc->rpc);
        changelog_rpc_clnt_unref(crpc);
    }
    UNLOCK(&c_clnt->active_lock);
}

void
_dispatcher(rbuf_list_t *rlist, void *arg)
{
    xlator_t *this = NULL;
    changelog_clnt_t *c_clnt = NULL;
    changelog_rpc_clnt_t *crpc = NULL;
    struct ev_rpc erpc = {
        0,
    };
    struct list_head *next = NULL;

    c_clnt = arg;
    this = c_clnt->this;

    erpc.rlist = rlist;
    next = c_clnt->active.next;

    while (1) {
        crpc = get_client(c_clnt, &next);
        if (!crpc)
            break;
        erpc.rpc = crpc->rpc;
        (void)changelog_invoke_rpc(this, crpc->rpc, &changelog_ev_program,
                                   CHANGELOG_REV_PROC_EVENT, &erpc);
        put_client(c_clnt, crpc);
    }
}

/** this is called under rotbuff's lock */
void
sequencer(rbuf_list_t *rlist, void *mydata)
{
    unsigned long range = 0;
    changelog_clnt_t *c_clnt = 0;

    c_clnt = mydata;

    range = (RLIST_ENTRY_COUNT(rlist)) / NR_IOVEC;
    if ((RLIST_ENTRY_COUNT(rlist)) % NR_IOVEC)
        range++;
    RLIST_STORE_SEQ(rlist, c_clnt->sequence, range);

    c_clnt->sequence += range;
}

void *
changelog_ev_dispatch(void *data)
{
    int ret = 0;
    void *opaque = NULL;
    xlator_t *this = NULL;
    changelog_clnt_t *c_clnt = NULL;
    struct timeval tv = {
        0,
    };

    c_clnt = data;
    this = c_clnt->this;

    while (1) {
        /* TODO: change this to be pthread cond based.. later */

        tv.tv_sec = 1;
        tv.tv_usec = 0;
        select(0, NULL, NULL, NULL, &tv);

        ret = rbuf_get_buffer(c_clnt->rbuf, &opaque, sequencer, c_clnt);
        if (ret != RBUF_CONSUMABLE) {
            if (ret != RBUF_EMPTY)
                gf_smsg(this->name, GF_LOG_WARNING, 0,
                        CHANGELOG_MSG_BUFFER_STARVATION_ERROR,
                        "Failed to get buffer for RPC dispatch",
                        "rbuf_retval=%d", ret, NULL);
            continue;
        }

        ret = rbuf_wait_for_completion(c_clnt->rbuf, opaque, _dispatcher,
                                       c_clnt);
        if (ret)
            gf_msg(this->name, GF_LOG_WARNING, 0,
                   CHANGELOG_MSG_PUT_BUFFER_FAILED,
                   "failed to put buffer after consumption");
    }

    return NULL;
}

void
changelog_ev_queue_connection(changelog_clnt_t *c_clnt,
                              changelog_rpc_clnt_t *crpc)
{
    pthread_mutex_lock(&c_clnt->pending_lock);
    {
        list_add_tail(&crpc->list, &c_clnt->pending);
        pthread_cond_signal(&c_clnt->pending_cond);
    }
    pthread_mutex_unlock(&c_clnt->pending_lock);
}

struct rpc_clnt_procedure changelog_ev_procs[CHANGELOG_REV_PROC_MAX] = {
    [CHANGELOG_REV_PROC_NULL] = {"NULL", NULL},
    [CHANGELOG_REV_PROC_EVENT] = {"EVENT DISPATCH",
                                  changelog_event_dispatch_rpc},
};

struct rpc_clnt_program changelog_ev_program = {
    .progname = "CHANGELOG EVENT DISPATCHER",
    .prognum = CHANGELOG_REV_RPC_PROCNUM,
    .progver = CHANGELOG_REV_RPC_PROCVER,
    .numproc = CHANGELOG_REV_PROC_MAX,
    .proctable = changelog_ev_procs,
};