Tree farm

function makeTree()
  turtle.select(1)
  turtle.place()
  turtle.select(2)
  turtle.place()
end

function cutTree()
  turtle.dig()
  turtle.forward()
  while turtle.detectUp() do
    turtle.digUp()
    turtle.up()
  end
  while not turtle.detectDown() do
    turtle.down()
  end
  turtle.back()
end

function depositWood()
  turtle.select(3)
  turtle.dropDown()
  turtle.select(4)
  turtle.dropDown()
end

function everything()
  fuel = turtle.getFuelLevel()
  sapLevel = turtle.getItemCount(1)
  mealLevel = turtle.getItemCount(2)
  while sapLevel>0 and mealLevel>0 and fuel>0 do
    makeTree()
    cutTree()
    depositWood()
  end
  if sapLevel == 0 then
    turtle.select(1)
    turtle.turnRight()
    turtle.suck()
    turtle.turnLeft()
  elseif mealLevel == 0 then
    turtle.select(2)
    turtle.turnRight()
    turtle.turnRight()
    turtle.suck()
    turtle.turnRight()
    turtle.turnRight()
  elseif fuel == 0 then
    turtle.select(16)
    turtle.turnLeft()
    turtle.suck()
    turtle.turnRight()
    turtle.refuel()
  end
end

everything()