/* monitor.c: Monitoring component.
 *
 * Copyright (C) 2011 VMware, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <arpa/inet.h>
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <zmq.h>

#define ERR_EXIT(what) { \
    fprintf (stderr, "error in %s: %s\n", what, zmq_strerror (errno)); \
    exit (EXIT_FAILURE); \
    }

int main (int argc, char *argv [])
{
    void *ctx;
    const char *client_ep, *service_ep, *notifier_host;
    char notifier_ep[1024];
    char msg_buf[1024];
    char hostname[1024];
    void *client_socket, *service_socket, *notifier_socket;
    int rc;
   
    if (argc != 4) {
        fprintf (stderr,
	    "usage: monitor "\
            "<notifier-host> <client-bind-ep> <service-connect-ep>\n");
	exit (EXIT_FAILURE);
    }
    notifier_host = argv [1];
    sprintf (notifier_ep, "tcp://%s:7770", notifier_host);
    client_ep = argv [2];
    service_ep = argv [3];

    rc = gethostname(hostname, sizeof hostname);
    assert (rc == 0);

    ctx = zmq_init (1);
    if (!ctx)
	ERR_EXIT ("zmq_init");

    client_socket = zmq_socket (ctx, ZMQ_XPUB);
    if (!client_socket)
	ERR_EXIT ("zmq_socket");

    rc = zmq_bind (client_socket, client_ep);
    if (rc < 0)
	ERR_EXIT ("zmq_bind");

    service_socket = zmq_socket (ctx, ZMQ_XSUB);
    if (!service_socket)
	ERR_EXIT ("zmq_socket");
    
    rc = zmq_connect (service_socket, service_ep);
    if (rc < 0)
	ERR_EXIT ("zmq_connect");

    notifier_socket = zmq_socket (ctx, ZMQ_PUB);
    if (!notifier_socket)
	ERR_EXIT ("zmq_socket");
    
    rc = zmq_connect (notifier_socket, notifier_ep);
    if (rc < 0)
	ERR_EXIT ("zmq_bind");

    int64_t more;
    size_t moresz;
    uint32_t seq_no = 0;
    
    zmq_msg_t msg;
    rc = zmq_msg_init (&msg);
    assert (rc == 0);

    zmq_pollitem_t items [2];
    items [0].socket = client_socket;
    items [0].fd = 0;
    items [0].events = ZMQ_POLLIN;
    items [0].revents = 0;
    items [1].socket = service_socket;
    items [1].fd = 0;
    items [1].events = ZMQ_POLLIN;
    items [1].revents = 0;

    while (1) {

        /*  Wait for either upstream subscriptions or messages. */
        rc = zmq_poll (&items [0], 2, -1);
        if (rc < 0)
	    ERR_EXIT ("zmq_poll");

        /*  Process an upstream subscription. */
        if (items [0].revents & ZMQ_POLLIN) {
            while (1) {

                rc = zmq_recvmsg (client_socket, &msg, 0);
                if (rc < 0)
		    ERR_EXIT ("zmq_recvmsg");
                
                moresz = sizeof (more);
                rc = zmq_getsockopt (client_socket, ZMQ_RCVMORE, &more, &moresz);
                if (rc < 0)
		    ERR_EXIT ("zmq_getsockopt");

                rc = zmq_sendmsg (service_socket, &msg, more ? ZMQ_SNDMORE : 0);
                if (rc < 0)
		    ERR_EXIT ("zmq_sendmsg");

                if (!more)
                    break;
            }
        }

        /*  Process a downstream message. */
        if (items [1].revents & ZMQ_POLLIN) {
            while (1) {

                rc = zmq_recvmsg (service_socket, &msg, 0);
                if (rc < 0)
		    ERR_EXIT ("zmq_recvmsg");
                
                moresz = sizeof (more);
                rc = zmq_getsockopt (service_socket, ZMQ_RCVMORE, &more, &moresz);
                if (rc < 0)
		    ERR_EXIT ("zmq_getsockopt");

                rc = zmq_sendmsg (client_socket, &msg, more ? ZMQ_SNDMORE : 0);
                if (rc < 0)
		    ERR_EXIT ("zmq_sendmsg");

                if (!more) {
		    /*  For each complete message, publish the sequence number
		        (# of messages sent) to the notifier socket. */
                    uint32_t seq_no_wire;

                    seq_no++;
                    seq_no_wire = htonl (seq_no);
                    sprintf(msg_buf, "VALUE %s monitor %u", hostname, seq_no);
                    rc = zmq_send (notifier_socket, msg_buf, strlen(msg_buf), 0);
		    if (rc != strlen(msg_buf))
			ERR_EXIT ("zmq_send");

                    break;
                }
            }
        }

    }

    exit (EXIT_SUCCESS);
}