Simple mining Drill revisited

-- pastebin get dNmedzr3 drill
-- pastebin run dNmedzr3
function dig()
    return turtle.dig()
end

local blacklist = {
  "minecraft:stone",
  "minecraft:cobblestone",
  "minecraft:dirt",
  "minecraft:grass",
  -- and so on
}
local _blist = {}

local firsthit = false
local fill = 0
local drill = true
local depth = 0

-- Inverse blacklist for fast hashmap lookup
for i = 1, #blacklist do
  _blist[blacklist[i]] = true
end


while drill do
    turtle.select(2)
    temp, data = turtle.inspectDown()
    if data.name == "minecraft:bedrock" then
        for i=0,depth-1 do
            turtle.up()
            if i >= (depth - (fill)) then
                turtle.select(2)
                turtle.placeDown()
            end
        end
        drill = false
    else
        if not turtle.detectDown() then
            if not firsthit then
                firsthit=true
                fill = depth + 1
            end
        end
        turtle.digDown()
        if turtle.down() then depth = depth + 1 end
        for j=1,4 do
            temp, block = turtle.inspect()
            if _blist[block["name"]] then
                --do nothing
            else
                dig()
            end
            turtle.turnLeft()
        end
    end
end