tbt_mine_torch.lua

local MaxTorchDistance = 14

function getIndexOf(item)
    for i = 1, 16 do
        local item = turtle.getItemDetail(i, false)
        if item["name"] == item then
            return i
        end
    end

    return -1
end

function refuel()
    if turtle.getFuelLevel() == 0 then
        for i = 1, 16 do
            turtle.select(i)
            if turtle.refuel(0) then
                return true
            end
        end

        print("No fuel found!")
        return false
    else
        return true
    end
end

function main()
    local torchDistance = 0
    local indexOfTorches = getIndexOf("minecraft:torch")

    if indexOfTorches == -1 then
        print("No torches found!")
        return
    end

    if indexOfTorches ~= 0 then
        turtle.select(indexOfTorches)
        turtle.transferTo(0)
    end

    while true do
        if refuel() then
            turtle.dig()
            turtle.forward()
            turtle.digDown()

            torchDistance = torchDistance + 1
            if torchDistance == MaxTorchDistance then
                turtle.placeDown()
                torchDistance = 0
            end

            turtle.dig("left")
            turtle.dig("right")
            turtle.down()
            turtle.dig("left")
            turtle.dig("right")
            turtle.up()
            turtle.up()
            turtle.dig("left")
            turtle.dig("right")
            turtle.down()
        else
            break
        end
    end
end

main()