/*  Starshatter OpenSource Distribution
     Copyright (c) 1997-2004, Destroyer Studios LLC.
     All Rights Reserved.

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     modification, are permitted provided that the following conditions are met:

     * Redistributions of source code must retain the above copyright notice,
        this list of conditions and the following disclaimer.
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        this list of conditions and the following disclaimer in the documentation
        and/or other materials provided with the distribution.
     * Neither the name "Destroyer Studios" nor the names of its contributors
        may be used to endorse or promote products derived from this software
        without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
     AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
     LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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     SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.

     SUBSYSTEM:    NetEx.lib
     FILE:         NetLink.cpp
     AUTHOR:       John DiCamillo


     OVERVIEW
     ========
     Network (IP) Socket Wrapper Implementation
*/


#include "MemDebug.h"
#include "NetLink.h"
#include "NetGram.h"
#include "NetMsg.h"
#include "NetPeer.h"
#include "NetLayer.h"

// +-------------------------------------------------------------------+

DWORD WINAPI NetLinkProc(LPVOID link);

const DWORD UDP_HEADER_SIZE = 34;

// +-------------------------------------------------------------------+
// client-side ctor
NetLink::NetLink()
    : hnet(0), shutdown(false), traffic_time(50), resend_time(300),
      packets_sent(0), packets_recv(0), bytes_sent(0), bytes_recv(0), retries(0), drops(0), lag(100)
{
    ZeroMemory(lag_samples, sizeof(lag_samples));
    lag_index = 0;

    DWORD thread_id = 0;
    hnet = CreateThread(0, 4096, NetLinkProc, (LPVOID) this, 0, &thread_id);
}

// server-side ctor
NetLink::NetLink(NetAddr& a)
    : addr(a), hnet(0), shutdown(false), traffic_time(50), resend_time(300),
      packets_sent(0), packets_recv(0), bytes_sent(0), bytes_recv(0), retries(0), drops(0), lag(100)
{
    ZeroMemory(lag_samples, sizeof(lag_samples));
    lag_index = 0;

    sock.bind(addr);
    DWORD thread_id = 0;
    hnet = CreateThread(0, 4096, NetLinkProc, (LPVOID) this, 0, &thread_id);
}

NetLink::~NetLink()
{
    if (!shutdown) {
        shutdown = true;
    }

    if (hnet) {
        WaitForSingleObject(hnet, 2000);
        CloseHandle(hnet);
    }

    send_list.destroy();    // packets waiting to be ack'ed must be destroyed
    recv_list.clear();      // received messages are owned by the peers
    peer_list.destroy();    // but the net link owns the peers!
}

// +--------------------------------------------------------------------+

static DWORD base_netid = 1000;

DWORD
NetLink::AddPeer(const char* a, WORD p)
{
    return AddPeer(NetAddr(a, p));
}

DWORD
NetLink::AddPeer(DWORD a, WORD p)
{
    return AddPeer(NetAddr(a, p));
}

DWORD
NetLink::AddPeer(const NetAddr& a)
{
    if (!a.IPAddr())
        return 0;

    AutoThreadSync auto_sync(sync);

    NetPeer* peer = FindPeer(a);

    if (!peer) {
        peer = new(__FILE__, __LINE__) NetPeer(a, base_netid++);
        if (peer)
            peer_list.append(peer);
    }

    if (peer)
        return peer->NetID();

    return 0;
}

// +--------------------------------------------------------------------+

bool
NetLink::SendMessage(DWORD nid, void* d, int l, BYTE f)
{
    return SendMessage(new(__FILE__,__LINE__) NetMsg(nid, d, l, f));
}

bool
NetLink::SendMessage(DWORD nid, BYTE type, const char* text, int len, BYTE f)
{
    return SendMessage(new(__FILE__,__LINE__) NetMsg(nid, type, text, len, f));
}

bool
NetLink::SendMessage(NetMsg* msg)
{
    if (msg) {
        if (msg->Type() != NetMsg::INVALID  &&
             msg->Type() <  NetMsg::RESERVED &&
             msg->NetID()) {

            NetPeer* p = FindPeer(msg->NetID());
            if (p)
                return p->SendMessage(msg);
        }

        delete msg;
    }

    return false;
}

// +--------------------------------------------------------------------+

NetMsg*
NetLink::GetMessage(DWORD netid)
{
    NetMsg* msg = 0;

    // receive from specific host:
    if (netid) {
        NetPeer* p = FindPeer(netid);
        if (p) {
            msg = p->GetMessage();

            sync.acquire();
            recv_list.remove(msg);
            sync.release();
        }
    }

    return msg;
}

// +--------------------------------------------------------------------+

NetMsg*
NetLink::GetMessage()
{
    NetMsg* msg = 0;

    // get first available packet:

    // Double-checked locking:
    if (recv_list.size()) {
        sync.acquire();
        if (recv_list.size()) {
            msg = recv_list.removeIndex(0);
        }
        sync.release();

        if (msg && msg->NetID()) {
            NetPeer* p = FindPeer(msg->NetID());
            if (p) {
                p->GetMessage();  // remove message from peer's list
                                  // don't do this inside of sync block -
                                  // it might cause a deadlock
            }
        }
    }

    return msg;
}

// +--------------------------------------------------------------------+

void
NetLink::Shutdown()
{
    shutdown = true;
}

// +--------------------------------------------------------------------+

DWORD WINAPI NetLinkProc(LPVOID link)
{
    NetLink* netlink = (NetLink*) link;

    if (netlink)
        return netlink->DoSendRecv();

    return (DWORD) E_POINTER;
}

DWORD
NetLink::DoSendRecv()
{
    while (!shutdown) {
        ReadPackets();
        SendPackets();

        // discard reeeeally old peers:
        sync.acquire();

        ListIter<NetPeer> iter = peer_list;
        while (!shutdown && ++iter) {
            NetPeer* peer = iter.value();

            if ((NetLayer::GetUTC() - peer->LastReceiveTime()) > 300)
                delete iter.removeItem();
        }

        sync.release();
        Sleep(traffic_time);
    }

    return 0;
}

void
NetLink::ReadPackets()
{
    while (!shutdown && sock.select(NetSock::SELECT_READ) > 0) {
        NetGram* gram = RecvNetGram();

        if (gram && gram->IsReliable()) {
            if (gram->IsAck()) {
                ProcessAck(gram);
                delete gram;
            }
            else {
                AckNetGram(gram);
                QueueNetGram(gram);
            }
        }
        else {
            QueueNetGram(gram);
        }
    }
}

void
NetLink::SendPackets()
{
    if (shutdown)
        return;

    if (sock.select(NetSock::SELECT_WRITE) > 0) {
        DoRetries();
    }

    AutoThreadSync auto_sync(sync);

    ListIter<NetPeer> iter = peer_list;
    while (!shutdown && ++iter) {
        NetPeer* p = iter.value();
        NetGram* g = 0;

        do {
            if (sock.select(NetSock::SELECT_WRITE) > 0) {
                g = p->ComposeGram();
                if (g) {
                    SendNetGram(g);
                }
            }
            else {
                g = 0;
            }
        }
        while (!shutdown && g);
    }
}

// +--------------------------------------------------------------------+

void
NetLink::SendNetGram(NetGram* gram)
{
    if (gram) {
        if (gram->IsReliable()) {
            send_list.append(gram);
        }

        int err = sock.sendto(gram->Body(), gram->Address());

        if (err < 0) {
            err = NetLayer::GetLastError();
        }
        else {
            packets_sent += 1;
            bytes_sent   += gram->Size() + UDP_HEADER_SIZE;
        }
    
        if (!gram->IsReliable())
            delete gram;
    }
}

NetGram*
NetLink::RecvNetGram()
{
    NetAddr from;
    Text msg = sock.recvfrom(&from);

    packets_recv += 1;
    bytes_recv   += msg.length() + UDP_HEADER_SIZE;

    return new(__FILE__, __LINE__) NetGram(from, msg);
}

// +--------------------------------------------------------------------+

void
NetLink::AckNetGram(NetGram* gram)
{
    if (gram) {
        NetGram ack = gram->Ack();

        int err = sock.sendto(ack.Body(), gram->Address());
        if (err < 0)
            err = NetLayer::GetLastError();
    }
    else {
        Print("NetLink::AckNetGram( NULL!!! )\n");
    }
}

void
NetLink::ProcessAck(NetGram* gram)
{
    if (!shutdown && send_list.size()) {
        AutoThreadSync auto_sync(sync);

        // remove the ack flag:
        gram->ClearAck();

        // find a matching outgoing packet:
        int sent = send_list.index(gram);
        if (sent >= 0) {
            NetGram* orig = send_list.removeIndex(sent);
            DWORD    time = NetLayer::GetTime();
            DWORD    msec = time - orig->SendTime();
            double   dlag = 0.75 * lag + 0.25 * msec;

            if (lag_index >= 10) lag_index = 0;
            lag_samples[lag_index++] = msec;

            NetPeer* peer = FindPeer(orig->Address());
            if (peer)
                peer->SetLastReceiveTime(NetLayer::GetUTC());

            delete orig;

            lag = (DWORD) dlag;

            if (lag > 100)
                resend_time = 3 * lag;
            else
                resend_time = 300;
        }
    }
}

void
NetLink::QueueNetGram(NetGram* gram)
{
    if (!shutdown) {
        AutoThreadSync auto_sync(sync);

        DWORD    sequence = 0;
        NetPeer* peer     = FindPeer(gram->Address());

        if (peer) {
            sequence = peer->Sequence();
        }
        else {
            peer = new(__FILE__, __LINE__) NetPeer(gram->Address(), base_netid++);
            if (peer)
                peer_list.append(peer);
        }

        if (!gram->IsReliable()) {
            if (gram->Sequence() < sequence) {  // discard, too old
                delete gram;
                return;
            }
        }

        // sort this gram into the recv list(s) based on sequence:
        if (peer) {
            peer->ReceiveGram(gram, &recv_list);
        }
    }
}

// +--------------------------------------------------------------------+

void
NetLink::DoRetries()
{
    if (!shutdown) {
        AutoThreadSync auto_sync(sync);

        if (send_list.size()) {
            int time = (int) NetLayer::GetTime();

            ListIter<NetGram> iter = send_list;
            while (!shutdown && ++iter) {
                NetGram* gram = iter.value();

                // still trying ?
                if (gram->Retries() > 0) {
                    DWORD last_send = gram->SendTime();
                    DWORD delta     = time - last_send;

                    if (delta > resend_time) {
                        gram->Retry();
                        sock.sendto(gram->Body(), gram->Address());
                        retries++;
                    }
                }

                // oh, give it up:
                else {
                    iter.removeItem();
                    delete gram;
                    drops++;
                }
            }
        }
    }
}

// +--------------------------------------------------------------------+

NetPeer*
NetLink::FindPeer(DWORD netid)
{
    AutoThreadSync auto_sync(sync);
    NetPeer* peer = 0;

    ListIter<NetPeer> iter = peer_list;
    while (++iter && !peer) {
        NetPeer* p = iter.value();

        if (p->NetID() == netid)
            peer = p;
    }

    return peer;
}

NetPeer*
NetLink::FindPeer(const NetAddr& a)
{
    AutoThreadSync auto_sync(sync);
    NetPeer* peer = 0;

    ListIter<NetPeer> iter = peer_list;
    while (++iter && !peer) {
        NetPeer* p = iter.value();

        if (p->Address() == a)
            peer = p;
    }

    return peer;
}