/*  Project nGenEx
    Destroyer Studios LLC
    Copyright © 1997-2004. All Rights Reserved.

    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;
}