function getItemSlots()
  local slots = 16
  for i = 1, 16 do
    if turtle.getItemCount(i) > 0 then
      slots = slots - 1
    end
  end
  return slots
end

function autoRefuel()
  if turtle.getFuelLevel() <= 80 do
    turtle.refuel()
  end
end

function dropAllItems()
  for i = 1, 16 do
    turtle.select(i)
    turtle.drop()
  end
end

while true do
  while getItemSlots() > 0 do
    while turtle.dig() do end
    while turtle.digUp() do end
    autoRefuel()
    turtle.forward()
  end
  --Turtle ran out of space
  turtle.turnRight()
  turtle.turnRight()
  --Turn Back
  while true do
    local _,data = turtle.inspect()
    if data.name == "minecraft:chest" then break end
    autoRefuel()
    turtle.forward()
  end
  dropAllItems()
  turtle.turnRight()
  turtle.forward()
  turtle.turnRight()
end