Mossy farm

function scheduleHomeRun()
  refuelScheduled = true
end

function refuel()
  if turtle.getFuelLevel == "unlimited" then return true end
  if turtle.getFuelLevel() < 50 then
    turtle.select(5)
    turtle.refuel(1)
    if turtle.getItemCount(5) == 0 then scheduleHomeRun() end
  end
end

function goStraight()
  while turtle.detect() == false do
    turtle.forward()
    refuel()
  end
end

refuelScheduled = false

function replace()
  turtle.digDown()
  turtle.select(4)
  turtle.placeDown()
  turtle.select(3)
end

function digRow()
  while turtle.detect() == false do
    turtle.forward()
    refuel()
    turtle.select(3)
    if turtle.compareDown() then
      replace()
    end
  end
end

function findHome()
    goStraight()
    turtle.select(1)
    if turtle.compare() then
      turtle.turnRight()
      goStraight()
      turtle.turnRight()
    else
      turtle.turnLeft()
      goStraight()
      turtle.turnLeft()
      turtle.turnLeft()
    end
end

function doRoute()
  while true do
    digRow()
    turtle.turnRight()
    turtle.forward()
    refuel()
    turtle.turnRight()
    goStraight()
    turtle.turnLeft()
    turtle.forward()
    refuel()
    if turtle.detect() then
      findHome()
      turtle.turnLeft()
      turtle.turnLeft()
      turtle.select(3)
      turtle.drop(turtle.getItemCount(3)-1)
      turtle.select(4)
      turtle.suck()
      turtle.turnLeft()
      turtle.turnLeft()
    else
      turtle.turnLeft()
    end
  end
end
findHome()
while true do
  doRoute()
end