/* 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 "memory/Allocator.h"
#include "net/ConverterV15.h"
#include "util/Identity.h"
#include "wire/SwitchHeader.h"
#include "wire/DataHeader.h"
#include "net/SessionManager.h"
#include "wire/ContentType.h"
#include "wire/Headers.h"
#include "util/Checksum.h"
#include "wire/RouteHeader.h"

//#include "util/Hex.h"

struct ConverterV15_pvt
{
    struct ConverterV15 pub;
    struct SessionManager* sm;
    uint8_t myIp6[16];
    struct Log* log;
    Identity
};

/**
 * Incoming packet with a SessionManager header followed by a ContentHeader and then whatever
 * content.
 */
static Iface_DEFUN incomingFromUpperDistributorIf(struct Message* msg,
                                                  struct Iface* upperDistributorIf)
{
    struct ConverterV15_pvt* conv =
        Identity_containerOf(upperDistributorIf, struct ConverterV15_pvt, pub.upperDistributorIf);

    Assert_true(msg->length >= DataHeader_SIZE + RouteHeader_SIZE);

    struct RouteHeader* hdr = (struct RouteHeader*) msg->bytes;
    struct SessionManager_Session* sess = SessionManager_sessionForIp6(hdr->ip6, conv->sm);
    if (hdr->version_be && Endian_bigEndianToHost32(hdr->version_be) < 16) {
        // definitely old
    } else if (!hdr->version_be && sess && sess->version && sess->version < 16) {
        // session thinks it's old
    } else {
        // nothing is known about a node, fuckit, assume it's new !
        return Iface_next(&conv->pub.sessionManagerIf, msg);
    }

    struct DataHeader* dh = (struct DataHeader*) &hdr[1];
    enum ContentType type = DataHeader_getContentType(dh);

    if (type > 257) {
        Log_debug(conv->log, "DROP unconvertible type [%d]", type);
        return NULL;
    }

    //      My fears, come alive,
    // in this place where I once died
    //        demons dreamin',
    //          Knowing I,
    //        I just needed to
    //          _RE_ALIGN_
    Message_shift(msg, -(DataHeader_SIZE + RouteHeader_SIZE), NULL);
    if (type == ContentType_CJDHT) {
        // push a udp header and then an ip header and then checksum the udp
        Message_shift(msg, Headers_UDPHeader_SIZE, NULL);
    }
    if (type != ContentType_IPTUN) {
        Message_shift(msg, Headers_IP6Header_SIZE, NULL);
    }
    Message_shift(msg, RouteHeader_SIZE, NULL);
    Bits_memmove(msg->bytes, hdr, RouteHeader_SIZE);
    hdr = (struct RouteHeader*) msg->bytes;


    if (type == ContentType_IPTUN) {
        return Iface_next(&conv->pub.sessionManagerIf, msg);
    }

    struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) &hdr[1];
    Bits_memset(ip6, 0, Headers_IP6Header_SIZE);
    Headers_setIpVersion(ip6);
    ip6->hopLimit = 42;
    ip6->nextHeader = type;
    ip6->payloadLength_be = Endian_hostToBigEndian16(
        msg->length - RouteHeader_SIZE - Headers_IP6Header_SIZE);
    Bits_memcpyConst(ip6->destinationAddr, hdr->ip6, 16);
    Bits_memcpyConst(ip6->sourceAddr, conv->myIp6, 16);

    if (type == ContentType_CJDHT) {
        struct Headers_UDPHeader* udp = (struct Headers_UDPHeader*) &ip6[1];
        ip6->nextHeader = 17;
        ip6->hopLimit = 0;
        udp->srcPort_be = 0;
        udp->destPort_be = 0;
        udp->length_be = Endian_hostToBigEndian16(msg->length -
                                                  RouteHeader_SIZE -
                                                  Headers_IP6Header_SIZE -
                                                  Headers_UDPHeader_SIZE);
        udp->checksum_be = 0;
        udp->checksum_be =
            Checksum_udpIp6(ip6->sourceAddr,
                            (uint8_t*) udp,
                            msg->length - RouteHeader_SIZE - Headers_IP6Header_SIZE);

        //Log_debug(conv->log, "Converted CJDHT->v15");
    }

    //Log_debug(conv->log, "send [%s]", Hex_print(ip6, 32, msg->alloc));

    return Iface_next(&conv->pub.sessionManagerIf, msg);
}

//// --------------- Incoming, convert v15 to v16 --------------- ////

#define tryConvertDHT_OVERHEAD \
    (RouteHeader_SIZE + Headers_IP6Header_SIZE + Headers_UDPHeader_SIZE)
static inline bool tryConvertDHT(struct Message* msg)
{
    if (msg->length < tryConvertDHT_OVERHEAD) { return false; }
    struct RouteHeader* bih = (struct RouteHeader*) msg->bytes;
    struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) &bih[1];
    struct Headers_UDPHeader* udp = (struct Headers_UDPHeader*) &ip6[1];
    if (udp->srcPort_be || udp->destPort_be) { return false; }
    Message_shift(msg, -tryConvertDHT_OVERHEAD, NULL);
    struct DataHeader dh = {
        .contentType_be = Endian_hostToBigEndian16(ContentType_CJDHT),
        .versionAndFlags = DataHeader_CURRENT_VERSION << 4
    };
    Message_push(msg, &dh, DataHeader_SIZE, NULL);
    Message_shift(msg, RouteHeader_SIZE, NULL);
    Bits_memmoveConst(msg->bytes, bih, RouteHeader_SIZE);
    return true;
}

/**
 * Incoming packet with a SessionManager header and under that either an ipv6 or ipv4 header
 * depending on whether it's destine for TUN/DHT or IpTunnel.
 */
static Iface_DEFUN incomingFromSessionManagerIf(struct Message* msg, struct Iface* sessionManagerIf)
{
    struct ConverterV15_pvt* conv =
        Identity_containerOf(sessionManagerIf, struct ConverterV15_pvt, pub.sessionManagerIf);

    if (msg->length < RouteHeader_SIZE + DataHeader_SIZE) {
        Log_debug(conv->log, "DROP runt");
        return NULL;
    }

    struct RouteHeader* bih = (struct RouteHeader*) msg->bytes;

    uint8_t* ipPtr = (uint8_t*) &bih[1];

    //Log_debug(conv->log, "recv [%s]", Hex_print(ipPtr, 32, msg->alloc));

    int ipVer = Headers_getIpVersion(ipPtr);
    if (ipVer == DataHeader_CURRENT_VERSION) {
        return Iface_next(&conv->pub.upperDistributorIf, msg);
    }

    if (ipVer == 0) {
        if (msg->length < RouteHeader_SIZE + Headers_IP6Header_SIZE) {
            Log_debug(conv->log, "DROP runt");
            return NULL;
        }
        struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) ipPtr;
        if (ip6->sourceAddr[0] == 0xfc && ip6->destinationAddr[0] == 0xfc) {
            if (tryConvertDHT(msg)) {
                return Iface_next(&conv->pub.upperDistributorIf, msg);
            }
        }
    } else if (ipVer == 6) {
        if (msg->length < RouteHeader_SIZE + Headers_IP6Header_SIZE) {
            Log_debug(conv->log, "DROP runt");
            return NULL;
        }
        struct Headers_IP6Header* ip6 = (struct Headers_IP6Header*) ipPtr;
        if (ip6->sourceAddr[0] == 0xfc && ip6->destinationAddr[0] == 0xfc) {
            Message_pop(msg, NULL, RouteHeader_SIZE + Headers_IP6Header_SIZE, NULL);
            struct DataHeader dh = {
                .contentType_be = Endian_hostToBigEndian16(ip6->nextHeader),
                .versionAndFlags = DataHeader_CURRENT_VERSION << 4
            };
            Message_push(msg, &dh, DataHeader_SIZE, NULL);
            Message_shift(msg, RouteHeader_SIZE, NULL);
            Bits_memmoveConst(msg->bytes, bih, RouteHeader_SIZE);
            return Iface_next(&conv->pub.upperDistributorIf, msg);
        }
    } else if (ipVer != 4) {
        Log_debug(conv->log, "DROP unknown packet ip version");
        return NULL;
    }

    Message_shift(msg, DataHeader_SIZE, NULL);
    Bits_memmoveConst(msg->bytes, bih, RouteHeader_SIZE);

    bih = (struct RouteHeader*) msg->bytes;

    struct DataHeader* dh = (struct DataHeader*) &bih[1];
    Bits_memset(dh, 0, DataHeader_SIZE);
    dh->contentType_be = Endian_hostToBigEndian16(ContentType_IPTUN);
    dh->versionAndFlags = DataHeader_CURRENT_VERSION << 4;
    return Iface_next(&conv->pub.upperDistributorIf, msg);
}

struct ConverterV15* ConverterV15_new(struct Allocator* allocator,
                                      struct Log* log,
                                      struct SessionManager* sm,
                                      uint8_t myIp6[16])
{
    struct Allocator* alloc = Allocator_child(allocator);
    struct ConverterV15_pvt* out = Allocator_calloc(alloc, sizeof(struct ConverterV15_pvt), 1);
    out->pub.upperDistributorIf.send = incomingFromUpperDistributorIf;
    out->pub.sessionManagerIf.send = incomingFromSessionManagerIf;
    out->log = log;
    out->sm = sm;
    Bits_memcpyConst(out->myIp6, myIp6, 16);
    Identity_set(out);
    return &out->pub;
}