Stairs

local holeWidth = 5
local height = 4
local lend = false

function forward()
    while turtle.detect() do
        turtle.dig()
    end
    while turtle.attack() do
    end
    turtle.forward()
end

function selectItem(name)
    for i=1,16 do
        turtle.select(i)
        local data = turtle.getItemDetail()
        if data and data.name == name then
            return
        end
    end
end

function doHeight()
    for i=1,(height - 1) do
        if turtle.detectUp() then
            turtle.digUp()
        end
        turtle.up()
    end
    for i=1,(height - 1) do
        turtle.down()
    end
end

function goDown()
    local success, data = turtle.inspectDown()

    if success and data.name == "minecraft:bedrock" then
        lend = true
        print("hit bedrock")
    elseif turtle.detectDown() then
        turtle.digDown()
        turtle.down()
    else
        turtle.down()
    end
end

while not lend do
    for i=1,holeWidth do
        if not lend then
            doHeight()
            forward()
            turtle.turnRight()
            turtle.turnRight()
            selectItem("minecraft:oak_stairs")
            turtle.place()
            turtle.turnLeft()
            turtle.turnLeft()
            goDown()
        end
    end
    if not lend then
        doHeight()
        forward()
        turtle.turnRight()
        turtle.turnRight()
        selectItem("minecraft:oak_stairs")
        turtle.place()
        turtle.turnLeft()
        turtle.turnLeft()
        for i=1,3 do
            doHeight()
            turtle.turnRight()
            for j=1,holeWidth+1 do
                forward()
                doHeight()
            end
        end

        turtle.turnRight()
    end
end