---------------------------------------------------------
--- UDP based messaging protocol with handshake to identify packets
---------------------------------------------------------

local os = require('os')
local math = require('math')

local VERSION = "001"

return function(ZD)

  ZD.ZDP = function(port, noDebug)
    local zdp = {}

    zdp.port = port
    zdp.peers = {}
    zdp.listener = {}
    zdp.debug = not noDebug

    zdp.on = function(zdp, packet, func)
      if not zdp.listener[packet] then
        zdp.listener[packet] = {}
      end
      table.insert(zdp.listener[packet], func)
    end

    zdp.call = function(zdp, packet, ...)
      if not zdp.listener[packet] then
        return
      end
      local rets = {}
      for k,v in pairs(zdp.listener[packet]) do
        if type(v) == "function" then
          local ret = v(...)
          if ret then
            table.insert(rets, ret)
          end
        end
      end
      return unpack(rets)
    end

    zdp.udp = ZD.UDP(zdp.port, function(client, msg)
      if not msg then return end

      if msg == "ZDP HANDSHAKE " .. VERSION then -- CHECK FOR SAME VERSION

        math.randomseed(os.time())
        local id = msg .. client.address .. client.port .. os.time() .. math.random()  -- GENERATE UNIQUE ID
        id = ZD.md5.sumhexa(id)
        local nid = ZD.md5.sumhexa(id)

        if zdp.debug then
          print("Received Handshake from", client.address, client.port)
          print("ID:", id)
        end

        client:send("ZDP HANDSHAKE " .. VERSION .. " /" .. id, function()
            client.lastHeartbeat = os.time()
            client.id = id
            client.nid = nid
            zdp.peers[id] = client
            zdp.call("authenticated", client)
        end)
        return
      end

      local packet = ZD.json:decode(msg)
      if type(packet) ~= "table" then return zdp.call("message", packet) end
      if not packet.id or not zdp.peers[packet.id] then return zdp.call("packet", packet) end

      if packet.name and packet.data then
        zdp.call(packet.name, zdp.peers[packet.id], packet.data)
      elseif packet.data then
        zdp.call("data", zdp.peers[packet.id], packet.data)
      end
    end)


    return zdp
  end

end