local items = {

	["nomedoitem"] = {itemid = xxx , cost = xxx},
	["nomedoitem"] = {itemid = xxx , cost = xxx},

}

local coins = 6527

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


	msg = msg:lower()

	local item_name = items[msg]

    if msgcontains(msg, item_name) then
    	selfSay("you are sure ?", cid)
    	talkState[talkUser] = 1
    end

	if msgcontains(msg, "yes") and talkState[talkUser] == 1 then
		doPlayerAddItem(cid, items[msg].itemid, 1)
		doPlayerRemoveItem(cid, coins, items[msg].cost)
		selfSay("you received "..items[msg]..".", cid)
		talkState[talkUser] = 0
	elseif msgcontains(msg, "no") and talkState[talkUser] == 1 then
		selfSay("Bye!!", cid)
		talkState[talkUser] = 0
	end

	return true
end

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