cc turtle excavator

function digPlane(x,y)
    for i=0,y-1 do
        for i=0,x-1 do
            invCheck()
            turtle.dig()
            turtle.forward()
        end
        if i==y then
            if y%2==0 then
                turtle.turnLeft()
            else
                for j=0,x do
                    turtle.back()
                end
                turtle.turnRight()
            end
            for j=0,y do
                turtle.forward()
            end
            turtle.turnLeft()
        elseif i%2==0 then
            turtle.turnLeft()
            turtle.dig()
            turtle.forward()
            turtle.turnLeft()
        else
            turtle.turnRight()
            turtle.dig()
            turtle.forward()
            turtle.turnRight()
        end
    end
end

function digVolume(x,y,z)
    for i=0,z-1 do
        if fuelCheck(x+y+z) and turtle.digDown() then
            turtle.down()
            digPlane(x,y)
        else
            break
        end
    end
end

function fuelCheck(threshold)
    fuel = turtle.getFuelLevel()
    print("Current fuel: ",fuel)
    if fuel <= threshold then
        print("Fuel low!")
        return turtle.refuel()
    end
    return true
end

function invCheck()
    if turtle.getItemDetail(14) ~= nil then
        turtle.up()
        turtle.select(16)
        turtle.placeUp()
        for i=2,15 do
            turtle.select(i)
            turtle.dropUp()
        end
        turtle.select(1)
        turtle.down()
    end
end