CCTweaked: Refill with lava in nether

local cx = 0
local cy = 0
local cz = 0
local objective = turtle.getFuelLimit()

objective = objective - 300

function clearConsole()
    term.clear()
    term.setCursorPos(1,1)
end

function fillAndDrink()
    turtle.placeDown()
    if turtle.getItemCount(1) == 0 then
        return false
    end
    turtle.select(1)
    turtle.refuel()
    clearConsole()
    print("----------")
    print("fuel: " .. turtle.getFuelLevel() .. "/" .. objective)
    print("----------")
    return true
end

function isDrinkable()
    local success, data = turtle.inspectDown()
    return not success or data.name == "minecraft:lava"
end

function findFloor()
    local originalY = cy
    while isDrinkable() and turtle.getFuelLevel() < objective do
        turtle.down()
        cy = cy - 1
        fillAndDrink()
    end

    while cy < originalY do
        turtle.up()
        cy = cy + 1
    end
    return turtle.getFuelLevel() >= objective
end

function line()
    local originalX = cx
    while cx < 50 and turtle.getFuelLevel() < objective do
        turtle.forward()
        cx = cx + 1
        if findFloor() then
            break
        end
    end

    while cx > originalX do
        turtle.back()
        cx = cx - 1
    end
end

function goBackToSpawn()
    while cx > 0 do
        turtle.back()
        cx = cx - 1
    end
    while cy > 0 do
        turtle.up()
        cy = cy + 1
    end
    while cz > 0 do
        turtle.back()
        cz = cz - 1
    end
end

while turtle.getFuelLevel() < objective do
    line()
    if cx > 25 then
        break
    end
end
goBackToSpawn()