Nether Turtle

local pos = 0
local fuel = "minecraft:lava_bucket"
local keep = {
    [fuel] = true,
    ["minecraft:bucket"] = true,
    ["minecraft:ancient_debris"] = true,
    ["minecraft:diamond_ore"] = true,
    ["minecraft:diamond"] = true,
    ["minecraft:gold_ore"] = true,
    ["minecraft:raw_gold"] = true,
    ["minecraft:gold_nugget"] = true,
    ["minecraft:coal"] = true,
    ["minecraft:bucket"] = true
}

local badFluid = "minecraft:lava"
local turtle = turtle
local dir = 1
local length = 16

local function refuel()
    for i = 1, 16 do -- for each slot in the chest
        local item = turtle.getItemDetail(i, false)
        if item then -- if there is an item in this slot
            if (string.format("%s", item.name) == fuel) then -- if the item is in the blacklist
                turtle.select(i)
            end
        end
    end
    while(turtle.getFuelLevel() < 160) do
        turtle.refuel(1)
    end
end

local function checkInv()
    for i = 1, 16 do -- for each slot in the chest
        local item = turtle.getItemDetail(i, false)
        if item then -- if there is an item in this slot
            if not keep[string.format("%s", item.name)] then -- if the item is in the blacklist
                turtle.select(i)
                turtle.drop()
            end
        end
    end
end

local function select()
    for i = 1, 16 do -- for each slot in the chest
        local item = turtle.getItemDetail(i, false)
        if item then -- if there is an item in this slot
            if not keep[string.format("%s", item.name)] then -- if the item is NOT in the blacklist
                turtle.select(i)
            end
        end
    end
end

local function lava()
    local isBlock,block = turtle.inspectUp()
    if isBlock then
        if block.name == "minecraft:lava" then
            turtle.up()
            isBlock,block = turtle.inspectUp()
            if isBlock then
                if block.name == "minecraft:lava" then
                    select()
                    turtle.placeUp()
                end
            end
            turtle.down()
        end
    end
    isBlock,block = turtle.inspectDown()
    if isBlock then
        if block.name == "minecraft:lava" then
            turtle.down()
            isBlock,block = turtle.inspectDown()
            if isBlock then
                if block.name == "minecraft:lava" then
                    select()
                    turtle.placeDown()
                end
            end
            turtle.up()
        end
    end
end

local function loop()
    local ready = true

    lava()

    while ready do
        while turtle.detect() do
            turtle.dig()
            print("block in front")
        end
        while turtle.detectUp() do
            turtle.digUp()
            print("block on top")
        end
        while turtle.detectDown() do
            turtle.digDown()
            print("block on botem")
        end

        if not turtle.detect() then
            ready = false
        end
    end
    lava()
    turtle.forward()
end

while true do

    if(pos == length) then
        pos = -1
    end

    refuel()

    loop()

    if(pos == -1) then

        if(dir == 1) then
            turtle.turnRight()
            dir = 0
            loop()
            turtle.turnRight()
        else
            turtle.turnLeft()
            dir = 1
            loop()
            turtle.turnLeft()
        end
        checkInv()
    end
    pos = pos +1
end