Compressence

local direction = "up"
local emptyflag = 0

local function suck()
    if direction == "up" then
        turtle.suckDown(1)
    else
        turtle.suckUp(1)
    end
end

local function move_items(pos1,pos2)
    turtle.select(pos1)
    turtle.transferTo(pos2)
end

local function drop(side)
  turtle.select(1)
  if side == "up" then
    turtle.dropUp()
  elseif side == "down" then
    turtle.dropDown()
  else
    for i=1,16 do
      if i~=6 then
        turtle.select(i)
        turtle.drop()
      end
    end
  end
end

local function fillCraft()
    turtle.select(2)
    suck()
    turtle.select(5)
    suck()
    turtle.select(7)
    suck()
    turtle.select(10)
    suck()
end

-- Main Code

turtle.select(1)
turtle.turnLeft()
turtle.turnLeft()
while turtle.suck() == true do
    turtle.dropDown()
end
turtle.turnLeft()
turtle.turnLeft()

while true do
  fillCraft()
  turtle.select(1)
  if turtle.craft(1) == false then
    drop("forward")
    emptyflag = emptyflag + 1
    if direction == "up" then
      direction = "down"
    else
      direction = "up"
    end
  else
    emptyflag = 0
    drop(direction)
  end
  if emptyflag > 2 then
    break
  end
end