--DNS
term_x, term_y = term.getSize()
id = os.computerID()
version = "v 1.0"
modemSide = ""
sides = {"top", "bottom", "left", "right", "front", "back"}
privateKey = 30679223
modN = 43888321
PackageIdentifier = "_GOO.pack"
pack_pos = 1;


function findModem()
  for i = 1, #sides, 1 do
    if (peripheral.getType(sides[i]) == "modem") then
      modemSide = sides[i]
    end
  end
  if (modemSide == "") then return false end
  return true
end

function readBytesFromPack(d, b)
  s = string.sub(d, pack_pos, pack_pos + b)
  pack_pos = pack_pos +b +1
  return s
end

function isValidPackage(s)
  head = readBytesFromPack(s, string.len(PackageIdentifier))
  if (head == PackageIdentifier) then
    return true
  end
  return false
end

function resolveAddr(a)
  f = fs.open("servers.ls", "r")
  for line in file:lines() do
    s,e = string.find (line, a)
	if (s ~= nil) then
	  return string.sub(line, e+1)
	end
  end

end

function parsePackage(data, sId, dis)
  packId = toNumber(readBytesFromPack(data, 3))
  if (packId == 01) then --DNS REQ
    l = toNumber(readBytesFromPack(data, 2))
	addr = readBytesFromPack(data, l)
	res = resolveAddr(addr)
	print(res)
  end
end

------------------------------------

term.clear()
term.setCursorPos(1,1)
print("Google DNS id: "..id)
if (findModem() == false) then print("No modem found!") os.shutdown() end
print("Found modem at side: "..modemSide);
rednet.open(modemSide)
print("Rednet opened")
print("operating...")

while true do
  _event, _senderId, _data, _distance = os.pullEvent("rednet_message")
  pack_pos = 1;
  if (isValidPackage(_data)) then
    parsePackage(_data, _senderId, _distance)
   end
 end