harvester

function save(data,source)
  local file = fs.open(source,"w")
  file.write(textutils.serialize(data))
  file.close()
end

function load(source)
  local file = fs.open(source,"r")
  local data = file.readAll()
  file.close()
  return textutils.unserialize(data)
end

function rotate(dir)
  facing = load("facing")
  while facing ~= dir do
    turtle.turnRight()
    if facing == 3 then
      facing = 0
    else
      facing = facing+1
    end
  end
  save(dir,"facing")
end

fuel = vector.new(-775,72,467)

n=0
while true do
  count = load("count")
  n = n+1
  if count==0 then
    n=0
  elseif not fs.exists("buffer"..tostring(n)) then
    if n>count then
      n=0
    end
  else
    target = load("buffer"..tostring(n))
    fs.delete("buffer"..tostring(n))
    if count==n then
      save(0,"count")
      n=0
    end

    pos = vector.new(gps.locate())

    turtle.up()

    if pos.x < target.x then
      rotate(3)
    elseif pos.x > target.x then
      rotate(1)
    end

    i=0
    while i ~= math.abs(pos.x - target.x) do
      turtle.forward()
      i = i+1
    end

    if pos.z < target.z then
      rotate(0)
    elseif pos.z > target.z then
      rotate(2)
    end

    i=0
    while i ~= math.abs(pos.z - target.z) do
      turtle.forward()
      i = i+1
    end

    turtle.down()

    turtle.select(1)
    turtle.digDown()

    for i=1,16 do
      turtle.select(i)
      turtle.placeDown()
    end

    if turtle.getFuelLevel()<100 then
      pos = vector.new(gps.locate())
      rotate(2)
      turtle.up()
      for i=1,math.abs(pos.x - fuel.x) do
        turtle.forward()
      end
      rotate(3)
      for i=1,math.abs(pos.z - fuel.z) do
        turtle.forward()
      end
      turtle.down()

      turtle.select(16)
      turtle.suckDown(32)
      turtle.refuel()

      rotate(0)
      turtle.forward()

      for i=1,16 do
        turtle.select(i)
        turtle.dropDown()
      end

      turtle.select(1)
    end
  end
  sleep(5)
end