sugar

local richtung = 0

function forceForward()
  while not turtle.forward() do
    turtle.dig()
  end
end

function saveState(mode)
  local f = io.open("sugar.sav", "w")
  f:write(tostring(mode).."\n")
  f:write(tostring(richtung))
  f:close()
end

function init()
  local f = fs.open("sugar.sav", "r")

  local mode = f:readLine()
  local tmpRichtung = f:readLine()

  write(mode)
  write(tmpRichtung)

  f:close()

  if (mode) and (tonumber(mode) == 1) then
    returnToStart()
  else
    if (tmpRichtung) then
      richtung = tonumber(tmpRichtung)
    end

    turtle.select(16)
    if not turtle.compareDown() then
      turtle.back()
    end
  end

  saveState(0)
end

function waitForRefuel()
  while turtle.getFuelLevel() < 1000 do
    sleep(0.5)
  end
end

function turn()
  if richtung % 4 < 2 then
    turtle.turnRight()
  elseif richtung % 4 <= 3 then
    turtle.turnLeft()
  end

  if richtung < 3 then
    richtung = richtung + 1
  else
    richtung = 0
  end

  saveState(0)
end

function returnToStart()
  turtle.select(15)
  while not turtle.compareDown() do
    forceForward()
  end

  for i=1, 14, 1 do
    turtle.select(i)
    turtle.drop()
  end

  turtle.turnRight()
  waitForRefuel()
  richtung = 0
end

function go()
  turtle.select(15)
  if (turtle.compare()) then
    turtle.turnRight()
    saveState(1)
    returnToStart()
    saveState(0)
  end

  turtle.select(16)
  if (turtle.compare()) or not (turtle.detect()) then
    turtle.dig()

    if (turtle.forward()) then
      if not turtle.compareDown() then
        turtle.back()
        turn()
        go()
      end
    else
      turn()
      go()
    end
  else
    turn()
    go()
  end
end

init()
while true do
  go()
end