addEventHandler("onPlayerJoin", root,
    function ()
        Backpack:create(source)
    end
)

addCommandHandler("put",
    function (player, cmd, itemname, amount)
        if not itemname or itemname:len() == 0 then
            outputChatBox(("Syntax: /put <item> (optional: <amount>)"):format(itemname), player, 255, 100, 100)
        elseif not Item.exists(itemname) then
            outputChatBox(("* The item %q does not exist"):format(itemname), player, 255, 100, 100)
        else
            local backpack = Backpack(player)
            amount = amount and tonumber(amount) or 1

            if backpack:addItem(Item(itemname), amount) then
                outputChatBox(("* Added %d %s to your backpack [Weight: %d]"):format(amount, itemname, backpack:getWeight()), player, 0, 255, 0)
            else
                outputChatBox(("* Could not add %d %s to your backpack"):format(amount, itemname), player, 255, 100, 100)
            end
        end
    end
)

addCommandHandler("items",
    function (player)
        local items = Backpack(player):getItems(true)

        if #items == 0 then
            outputChatBox("* You have no items in your backpack", player, 255, 100, 100)
        else
            outputChatBox("* Your backpack items:", player, 0, 255, 0)

            for index, slot in pairs(items) do
                outputChatBox(("  %dx %s (%s)"):format(slot.amount, slot.item:getName(), slot.item:getCategory()), player, 130, 130, 130)
            end
        end
    end
)