/* vim: set expandtab ts=4 sw=4: */
/*
 * You may redistribute this program and/or modify it under the terms of
 * the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */
#include "interface/tuntap/BSDMessageTypeWrapper.h"
#include "interface/Interface.h"
#include "interface/InterfaceWrapper.h"
#include "util/platform/Sockaddr.h"
#include "memory/Allocator.h"
#include "util/Assert.h"
#include "util/Identity.h"
#include "wire/Ethernet.h"
#include "wire/Message.h"
#include "wire/Error.h"

/**
 * OSX and BSD is expect you to send the platform dependent address family type
 * rather than the ethertype, this InterfaceWrapper converts AF_INET and AF_INET6 to the
 * corrisponding ethertypes and back.
 */

struct BSDMessageTypeWrapper_pvt
{
    struct Interface generic;
    struct Interface* const wrapped;
    const uint16_t afInet_be;
    const uint16_t afInet6_be;
    struct Log* const logger;
    Identity
};

static uint8_t receiveMessage(struct Message* msg, struct Interface* iface)
{
    struct BSDMessageTypeWrapper_pvt* ctx =
        Identity_cast((struct BSDMessageTypeWrapper_pvt*)iface->receiverContext);

    if (msg->length < 4) {
        return Error_NONE;
    }

    uint16_t afType_be = ((uint16_t*) msg->bytes)[1];
    uint16_t ethertype = 0;
    if (afType_be == ctx->afInet_be) {
        ethertype = Ethernet_TYPE_IP4;
    } else if (afType_be == ctx->afInet6_be) {
        ethertype = Ethernet_TYPE_IP6;
    } else {
        Log_debug(ctx->logger, "Message of unhandled aftype [0x%04x]",
                  Endian_bigEndianToHost16(afType_be));
        return Error_NONE;
    }
    ((uint16_t*) msg->bytes)[0] = 0;
    ((uint16_t*) msg->bytes)[1] = ethertype;

    return Interface_receiveMessage(&ctx->generic, msg);
}

static uint8_t sendMessage(struct Message* msg, struct Interface* iface)
{
    struct BSDMessageTypeWrapper_pvt* ctx = Identity_cast((struct BSDMessageTypeWrapper_pvt*)iface);

    Assert_true(msg->length >= 4);

    uint16_t ethertype = ((uint16_t*) msg->bytes)[1];
    uint16_t afType_be = 0;
    if (ethertype == Ethernet_TYPE_IP6) {
        afType_be = ctx->afInet6_be;
    } else if (ethertype == Ethernet_TYPE_IP4) {
        afType_be = ctx->afInet_be;
    } else {
        Assert_always(!"Unsupported ethertype");
    }
    ((uint16_t*) msg->bytes)[0] = 0;
    ((uint16_t*) msg->bytes)[1] = afType_be;

    return Interface_sendMessage(ctx->wrapped, msg);
}

struct Interface* BSDMessageTypeWrapper_new(struct Interface* wrapped, struct Log* logger)
{
    struct BSDMessageTypeWrapper_pvt* context =
        Allocator_clone(wrapped->allocator, (&(struct BSDMessageTypeWrapper_pvt) {
            .wrapped = wrapped,
            .afInet6_be = Endian_hostToBigEndian16(Sockaddr_AF_INET6),
            .afInet_be = Endian_hostToBigEndian16(Sockaddr_AF_INET),
            .logger = logger
        }));
    Identity_set(context);

    InterfaceWrapper_wrap(wrapped, sendMessage, receiveMessage, &context->generic);

    return &context->generic;
}