building.lua

function selectItemRow(i)
    currentSlot = 1 + ((i-1) * 4)
    turtle.select(currentSlot)
    while turtle.getItemCount(currentSlot) == 0 do
        if currentSlot + 1 == 1 + i * 4 do
            error("no items!")
        end
        currentSlot = currentSlot + 1
        turtle.select(currentSlot)
    end
end

function turnDir(row)
    if dir % 2 == 0 then
        turtle.turnRight()
    else
        turtle.turnLeft()
    end
end

function nextRow(dir, row)
    turnDir(row)
    if dir == 0 then
        turtle.up()
    elseif dir == 1 then
        turtle.forward()
    elseif dir == 2 then
        turtle.up()
        turtle.forward()
    end
    turnDir(row)
    turtle.forward()
end

materials = {1, 2}
offset = {0, 0, 2, 0, 2, 2, 1, 2}

for n=0, 9 do
    currentMaterial = 1
    if n == 1 or n == 2 then
        currentMaterial = 2
    end
    for len=0, 20 do
        turtle.selectItemRow(currentMaterial)
        turtle.placeDown()
        turtle.forward()
    end
    nextRow(offset[n], n)
end
while not turttle.detectDown() do
    turtle.down()
end