net = {}
net.id = computer.address():sub(1,8)
net.delay = 2
net.np = 4957
net.cache = true
net.cache_time = 16
net.log = false
if cdlib and relib then
spawn("ncd",function() print(pcall(function()

 local olog = log
 local function log(...)
  if net.log then
   for k,v in ipairs({...}) do
    olog("[ncd] " .. tostring(v))
   end
  end
 end

 local mtab = {} -- modem table
 local lkr = {} -- LKR cache, contains copper_name = {modem="modem address last received from",addr="address last received from"}
 local rpackets = {} -- packets that have already been seen
 local pqueue = {} -- queue for packets to be sent. same format as relib.encode accepts. contains:
-- packet_id = {
--  pid = "3 char string of random data, same as packet_id",
--  addr = "address to send to",
--  port = #port number, 0-65535,
--  msg = "the packet data",
--  wf = "packet ID to wait till ack'd"
--  at = #attempts,
--  lst = #time of last attempt (USE UPTIME, NOT os.time() BECAUSE WINDOWS IS DUMB)
-- }

 for modem in component.list("modem") do
  mtab[#mtab+1] = modem
  log("added "..modem)
  component.invoke(modem,"open",net.np)
 end

 local function send(addr,msg,hops,src)
  log("sending packet "..msg.." to "..addr)
  local src=src or net.id
  local hops=hops or 0
  if lkr[addr] and net.cache then
   component.invoke(lkr[addr].modem,"send",lkr[addr].addr,net.np,"copper",cdlib.encode(hops,src,addr,msg))
  else
   for _,modem in ipairs(mtab) do
--    log(modem,"broadcast",net.np,hops,net.id,addr,msg,cdlib.encode(hops,net.id,addr,msg))
    component.invoke(modem,"broadcast",net.np,"copper",cdlib.encode(hops,net.id,addr,msg))
   end
  end
 end
 local function enqueue(addr,port,msg,waitfor)
  local qp = {}
  qp.msg = msg
  qp.addr = addr
  qp.port = port
  qp.wf = waitfor
  qp.pid = os.gensalt(3)
  qp.at = 0
  qp.pt = 1
  qp.lst = 0
  pqueue[qp.pid] = qp
  for k,v in pairs(qp) do log(k.." = "..tostring(v)) end
  return qp.pid
 end
 net.send = enqueue

 local function ppacket(hops,src,dst,data)
  if not rpackets[src..dst..data] then
   if dst == net.id then
    log("packet addressed here")
    event.push("net_rmsg",src,data)
    local pd = relib.decode(data)
    log(pd)
    if pd then
     log("valid relib packet")
     for k,v in pairs(pd) do log(k.." = "..v) end
     if pd.port and pd.pid and pd.at and pd.pt then
      if pd.pt == 0 then
       log("unreliable packet")
       event.push("net_msg",src,pd.port,pd.msg)
      elseif pd.pt == 1 then
       log("reliable packet, sending ack")
       event.push("net_msg",src,pd.port,pd.msg)
       pd.pt = 2
       pd.addr = src
       pd.lst = 0
       pd.msg = ""
       pd.unreliable=true
       pqueue[pd.pid] = pd
       for k,v in pairs(pqueue[pd.pid]) do log(k.." = "..tostring(v)) end
      elseif pd.pt == 2 then
       log("ack packet: "..pd.pid)
       pqueue[pd.pid] = nil
      end
     end
    end
   elseif src ~= net.id then
    if hops < 255 then
     send(dst,data,hops+1,src)
    end
   end
   rpackets[src..dst..data] = computer.uptime()
  end
 end

 while true do
  local ev = {event.pull()}

  if ev[1] == "rsendmsg" or ev[1] == "sendmsg" or ev[1] == "modem_message" then
--   log(table.unpack(ev))
  end

  if ev[1] == "rsendmsg" then
   send(ev[2],ev[3])
  elseif ev[1] == "sendmsg" then
   table.remove(ev,1)
   enqueue(table.unpack(ev))
  elseif ev[1] == "modem_message" and ev[4] == net.np and ev[6] == "copper" then
   local hops,src,dst,data = cdlib.decode(ev[7])
   if hops and src and dst and data then
    if lkr[src] ~= ev[3] then
     log("lkr["..tostring(src).."] = "..tostring(ev[3]))
     lkr[src] = {modem=ev[2],addr=ev[3],time=computer.uptime()}
    end
    ppacket(hops,src,dst,data)
   end
  end

  for k,v in pairs(pqueue) do
   if computer.uptime() > v.lst+net.delay and pqueue[v.wf] == nil then
    send(v.addr,relib.encode(v))
    v.lst = computer.uptime()
    v.at = v.at+1
    if v.at > 254 then
     pqueue[k] = nil
    end
    if v.unreliable then pqueue[k] = nil end
   end
  end

  for k,v in pairs(lkr) do
   if computer.uptime() > v.time+net.cache_time then
    lkr[k] = nil
   end
  end
  for k,v in pairs(rpackets) do
   if computer.uptime() > v+net.cache_time then
    rpackets[k] = nil
   end
  end

 end
end)) end)
end