Exp Npc

[Antagoreon]

Im Using the TFS 0.3.3 (Crying Damson) and i want a npc to change nuggets for exp i have this script but not work anyone can repair it plx?

local keywordHandler = KeywordHandler:new()
local npcHandler = NpcHandler:new(keywordHandler)
NpcSystem.parseParameters(npcHandler)
local talkState = {}

function onCreatureAppear(cid)                npcHandler:onCreatureAppear(cid)            end
function onCreatureDisappear(cid)            npcHandler:onCreatureDisappear(cid)            end
function onCreatureSay(cid, type, msg)            npcHandler:onCreatureSay(cid, type, msg)        end
function onThink()                    npcHandler:onThink()                    end

function creatureSayCallback(cid, type, msg)
    if(not npcHandler:isFocused(cid)) then
        return false
    end

	local talkUser = NPCHANDLER_CONVBEHAVIOR == CONVERSATION_DEFAULT and 0 or cid

	if msgcontains(msg, 'change') or msgcontains(msg, 'exchange') then
		if doPlayerRemoveItem(cid, 2157, 1) then
			selfSay('Would you like to change 1 nugget for 1000000 experience?', cid)
			talkState[talkUser] = 1
		end
	end	

	if talkState[talkUser] == 1 then
		if msgcontains(msg, 'yes') then
				doPlayerAddExp(cid, 1000000)
				selfSay('You have received 100000 experience!', cid)
				talkState[talkUser] = 0
			else
				selfSay('Then not', cid)
				talkState[talkUser] = 0
			end
		end
	end
	return TRUE
end

npcHandler:setCallback(CALLBACK_MESSAGE_DEFAULT, creatureSayCallback)
npcHandler:addModule(FocusModule:new())