Fuel up your turtle with ease!

	------------------------------------------------------------------
--			  Turtle Automatic Lava Collection
--			   By Scott Chamberlain (leftler)
-- Usage: place bucket in inventory and call with the
--  arguments <blocks> [drop]
--
-- The turtle travels 'blocks' forward and sucks all lava as
-- fuel in then makes a U-turn and attempts to retreive lava on
-- the way back. The seccond parameter will tell the turtle to
-- drop that many blocks after moving forward once.
--
-- if the turtle is a mining turtle it will break any blocks
-- blocking it's path
------------------------------------------------------------------

local tArgs = { ... }

if #tArgs == 0 then
  print("Usage: <blocks> [drop]")
  return
end

turtle.refuel()

if turtle.getFuelLevel() == 0 then
  print("The turtle must have at least some fuel to start with.")
  return
elseif turtle.getFuelLevel() == "unlimited" then
  print("This turtle does not use fuel to move")
  return
end

--Number of blocks to travel to get the lava
local maxDistance = tArgs[1]

--How deep to go to gather the lava
local drop = 0
if #tArgs >= 2 then
  drop = tonumber(tArgs[2])
end  

--local counter for how far the turtle has travle
local traveled = 0

--A helper function to try and move forward, it will attempt to dig if it is blocked.
local function moveForward()
  if turtle.forward() == false then
	--Failed to move, see if we can dig our way forward
	while turtle.dig() do
		  --Keep digging till we can't dig any more, in case gravel is falling.
		end
		if turtle.forward() == false then
		  print("I am either blocked or out of fuel.")
		  return false
		end
  end
  return true  
end

--A helper function to try and move down, it will attempt to dig if it is blocked.
local function moveDown()
  if turtle.down() == false then
	--Failed to move, see if we can dig our way down
	turtle.digDown()
		if turtle.down() == false then
		  print("I am either blocked or out of fuel.")
		  return false
		end
  end
  return true  
end

--A helper function to try and move down, it will attempt to dig if it is blocked.
local function moveUp()
  if turtle.up() == false then
	--Failed to move, see if we can dig our way down
	while turtle.digUp() do
		  --Keep digging till we can't dig any more, in case gravel is falling.
		end
		if turtle.up() == false then
		  print("I am either blocked or out of fuel.")
		  return false
		end
  end
  return true  
end

dropDone = false

--Attempt to travel to max distance for getting lava
for i = 1, maxDistance do
  if moveForward() == false then
	print("Could not move forward the full requested distance, starting U-Turn early.")
	   break
  end
  traveled = traveled + 1

  --drop to the requested depth
  if(dropDone == false) then
	for j = 1, drop do
		  if moveDown() == false then
			print("Could not drop the full distance")
				drop = j - 1
				end
		end
		dropDone = true
  end

  --grab the fule
  turtle.placeDown()
  if turtle.refuel() == false then
	--Whatever we picked up is invalid for fuel, put it back down
	turtle.placeDown()
  end
end

--Turn around move a block over and get more lava
turtle.turnRight()
moveForward()
turtle.turnRight()

--Travel back the same number of blocks we came
for i = 1, traveled do
  turtle.placeDown()
  turtle.refuel()

  --Check to see if we need to go up yet
  if i == traveled then
	for j = 1, drop do
		  moveUp()
		end
  end

  if moveForward() == false then
   --We are stuck, attempt to go up a level to get home
	   if drop > 0 then
		 repeat
		   moveUp()
		   drop = drop - 1
			   lastMove = moveForward()
		  until lastMove == true or drop == 0
	  
		 if lastMove == false then
			print("I am stuck!")
		 end
	  end
  end
end
  
turtle.turnRight()
moveForward()
turtle.turnRight()