/*
 * Copyright 2020 Max Planck Institute for Software Systems
 *
 * 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 <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <unistd.h>

#include <netsim.h>
#include "internal.h"

static uint64_t current_epoch = 0;

int netsim_init(struct netsim_interface *nsif,
        const char *eth_socket_path, int *sync_eth)
{
    struct cosim_eth_proto_dev_intro di;
    struct cosim_eth_proto_net_intro ni;
    int cfd, shm_fd;
    void *p;

    if ((cfd = uxsocket_connect(eth_socket_path)) < 0) {
        return -1;
    }

    memset(&ni, 0, sizeof(ni));

    if (*sync_eth)
        ni.flags |= COSIM_ETH_PROTO_FLAGS_NI_SYNC;

    if (send(cfd, &ni, sizeof(ni), 0) != sizeof(ni)) {
        perror("sending net intro failed");
        return -1;
    }

    if (uxsocket_recv(cfd, &di, sizeof(di), &shm_fd)) {
        return -1;
    }

    if ((p = shm_map(shm_fd)) == NULL) {
        return -1;
    }
    close(shm_fd);

    if ((di.flags & COSIM_ETH_PROTO_FLAGS_DI_SYNC) == 0) {
        *sync_eth = 0;
        nsif->sync = 0;
    } else {
        nsif->sync = *sync_eth;
    }

    nsif->d2n_queue = (uint8_t *) p + di.d2n_offset;
    nsif->n2d_queue = (uint8_t *) p + di.n2d_offset;
    nsif->d2n_elen = di.d2n_elen;
    nsif->n2d_elen = di.n2d_elen;
    nsif->d2n_enum = di.d2n_nentries;
    nsif->n2d_enum = di.n2d_nentries;
    nsif->d2n_pos = nsif->n2d_pos = 0;
    nsif->d2n_timestamp = nsif->n2d_timestamp = 0;

    return 0;
}

void netsim_cleanup(struct netsim_interface *nsif)
{
    fprintf(stderr, "netsim_cleanup: TODO\n");
    abort();
}

volatile union cosim_eth_proto_d2n *netsim_d2n_poll(
        struct netsim_interface *nsif, uint64_t timestamp)
{
    volatile union cosim_eth_proto_d2n *msg =
        (volatile union cosim_eth_proto_d2n *)
        (nsif->d2n_queue + nsif->d2n_pos * nsif->d2n_elen);

    /* message not ready */
    if ((msg->dummy.own_type & COSIM_ETH_PROTO_D2N_OWN_MASK) !=
            COSIM_ETH_PROTO_D2N_OWN_NET)
        return NULL;

    /* if in sync mode, wait till message is ready */
    nsif->d2n_timestamp = msg->dummy.timestamp;
    if (nsif->sync && nsif->d2n_timestamp > timestamp)
        return NULL;

    nsif->d2n_pos = (nsif->d2n_pos + 1) % nsif->d2n_enum;
    return msg;
}

void netsim_d2n_done(struct netsim_interface *nsif,
        volatile union cosim_eth_proto_d2n *msg)
{
    msg->dummy.own_type = (msg->dummy.own_type & COSIM_ETH_PROTO_D2N_MSG_MASK)
        | COSIM_ETH_PROTO_D2N_OWN_DEV;
}

volatile union cosim_eth_proto_n2d *netsim_n2d_alloc(
        struct netsim_interface *nsif, uint64_t timestamp,
        uint64_t latency)
{
    volatile union cosim_eth_proto_n2d *msg =
        (volatile union cosim_eth_proto_n2d *)
        (nsif->n2d_queue + nsif->n2d_pos * nsif->n2d_elen);

    if ((msg->dummy.own_type & COSIM_ETH_PROTO_N2D_OWN_MASK) !=
            COSIM_ETH_PROTO_N2D_OWN_NET)
    {
        return NULL;
    }

    msg->dummy.timestamp = timestamp + latency;
    nsif->n2d_timestamp = timestamp;

    nsif->n2d_pos = (nsif->n2d_pos + 1) % nsif->n2d_enum;
    return msg;
}

int netsim_n2d_sync(struct netsim_interface *nsif, uint64_t timestamp,
        uint64_t latency, uint64_t sync_delay, int sync_mode)
{
    volatile union cosim_eth_proto_n2d *msg;
    volatile struct cosim_eth_proto_n2d_sync *sync;
    int do_sync;

    if (!nsif->sync)
        return 0;

    switch (sync_mode) {
    case SYNC_MODES:
        do_sync = nsif->n2d_timestamp == 0 ||
            timestamp - nsif->n2d_timestamp >= sync_delay;
        break;
    case SYNC_BARRIER:
        do_sync = current_epoch == 0 ||
            timestamp - current_epoch >= sync_delay;
        break;
    default:
        fprintf(stderr, "unsupported sync mode=%u\n", sync_mode);
        return 0;
    }

    if (!do_sync) {
        return 0;
    }

    msg = netsim_n2d_alloc(nsif, timestamp, latency);
    if (msg == NULL)
        return -1;

    sync = &msg->sync;
    // WMB();
    sync->own_type = COSIM_ETH_PROTO_N2D_MSG_SYNC | COSIM_ETH_PROTO_N2D_OWN_DEV;

    return 0;
}

void netsim_advance_epoch(uint64_t timestamp, uint64_t sync_delay, int sync_mode)
{
    if (sync_mode == SYNC_BARRIER) {
        if (timestamp - current_epoch >= sync_delay) {
            current_epoch = timestamp;
        }
    }
}

uint64_t netsim_advance_time(uint64_t timestamp, uint64_t sync_delay, int sync_mode)
{
    switch (sync_mode) {
    case SYNC_MODES:
        return timestamp;
    case SYNC_BARRIER:
        return timestamp < current_epoch + sync_delay ?
            timestamp : current_epoch + sync_delay;
    default:
        fprintf(stderr, "unsupported sync mode=%u\n", sync_mode);
        return timestamp;
    }
}
