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

local Topic = {}
local items = {
    [{2670,10}] = 10000
}

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)
    for v, x in ipairs(items) do
        if (msgcontains(msg, "hello") or msgcontains(msg, "hi")) and (not npcHandler:isFocused(cid)) then
            if getPlayerItemCount(cid, v[1]) >= v[2] then
                npcHandler:say("Hello " .. getCreatureName(cid) .. ". Would you like to {exchange} 10 shrimp for some experience?", cid)
                Topic[cid] = 1
            else
                npcHandler:say("Hmm...don't think I can help you.", cid)
                Topic[cid] = 0
            end
            npcHandler:addFocus(cid)
        elseif(not npcHandler:isFocused(cid)) then
            return false
        elseif Topic[cid] == 1 then
            if msgcontains(msg, "exchange") then
                npcHandler:say("Are you sure you want to exchange " .. v[2] .. "x " .. getItemInfo(v[1]).name .. " for " .. x .. " experience points?", cid)
                Topic[cid] = 2
            else
                npcHandler:say("What was that? I don't understand you.", cid)
                Topic[cid] = 1
            end
        elseif Topic[cid] == 2 then
            if msgcontains(msg, "yes") then
                if doPlayerRemoveItem(cid, v[1], v[2] or 1) then
                    npcHandler:say("Great! Here you are.", cid)
                    doSendMagicEffect(getThingPos(cid), CONST_ME_MAGIC_BLUE)
                    doPlayerAddExperience(cid, x)
                    Topic[cid] = 0
                else
                    npcHandler:say("You do not have the item with you.", cid)
                    Topic[cid] = 0
                end
            elseif msgcontains(msg, "no") then
                npcHandler:say("Well, then leave.", cid)
                Topic[cid] = 0
            end
        elseif msgcontains(msg, "bye") or msgcontains(msg, "farewell") and npcHandler:isFocused(cid) then
            npcHandler:say("Good bye.", cid, TRUE)
            Topic[cid] = nil
            npcHandler:releaseFocus(cid)
        end

        return true
    end
end

npcHandler:setCallback(CALLBACK_MESSAGE_DEFAULT, creatureSayCallback)
npcHandler:setMessage(MESSAGE_WALKAWAY, "Have a good day!")