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

local Topic = {}
local items = {
    ["shrimp"] = { 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 m, v in ipairs(items) do
        if (msgcontains(msg, "hello") or msgcontains(msg, "hi")) and (not npcHandler:isFocused(cid)) then
            for i = 1, #v do
                if getPlayerItemCount(cid, v[1][i]) >= 1 then
                    npcHandler:say("Hello " .. getCreatureName(cid) .. ". How can I help you?", cid)
                    Topic[cid] == 1
                else
                    npcHandler:say("How can I help you?", cid)
                    Topic[cid] = nil
                end

                break
            end
            npcHandler:addFocus(cid)
        elseif(not npcHandler:isFocused(cid)) then
            return false
        elseif Topic[cid] == 1 then
            for i = 1, #m do
                if msgcontains(msg, m[i]) then
                    npcHandler:say("Do you want to trade " .. m[i] .. " for experience?", cid)
                    Topic[cid] = 2
                else
                    npcHandler:say("Sorry, what was that?", cid)
                    Topic[cid] = 0
                end

                break
            end
        elseif Topic[cid] == 2 then
            if msgcontains(cid, "yes") then
                for i = 1, #v do
                    if doPlayerRemoveItem(cid, v[1][i], v[2][i] or 1) then
                        npcHandler:say("Here you are!", cid)
                        doPlayerAddExperience(cid, v[3][i])
                        doSendMagicEffect(getThingPos(cid), CONST_ME_MAGIC_BLUE)
                        Topic[cid] = 0
                    else
                        npcHandler:say("You don't have the items!", cid)
                        Topic[cid] = 0
                    end

                    break
                end
            elseif msgcontains(cid, "no") then
                npcHandler:say("Then not.", 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, "How rude!")