Treekill 1.1

-- TreeKilla v1.1
-- Usage: treekill
-- TreeKilla will pull and store the first block
-- it finds. It then moves into the tree and
-- begins to chop its way up, harvesting logs
-- and leaves on the way.
-- Once TreeKilla no longer finds logs above
-- itself, it will move back down.
-- If TreeKilla is set to tear down a 2x2 tree,
-- it will move to the other corner of the trunk
-- before coming down.

local function spindig()
  for i=1,4 do
    turtle.dig()
    turtle.turnLeft()
  end
end

local y = 0
local s = 0
local f = 0
local isBig = false
local treeDir = 0 -- 0 for other log is left, 1 for other log is right
local fuel

while turtle.getFuelLevel() <= 400 do
  turtle.select(1) -- Refuel from slot 1
  turtle.refuel(1)
end
fuel = turtle.getFuelLevel() -- We'll tell how much fuel we used

turtle.select(2)
turtle.dig()
turtle.forward() -- The turtle is now inside the tree.
f = f + 1 -- We moved forward one block.

-- Detect "big" tree - is there a block ahead?
if turtle.detect() then
  isBig = true
  turtle.turnLeft()
  if turtle.detect() then
    treeDir = 0
  else
    treeDir = 1
  end
  turtle.turnRight()
  spindig()
else
  spindig() -- We'll always spindig.
end

-- Until we encounter air above our tree, go up.
while turtle.detectUp() ~= false do
  turtle.digUp()
  turtle.up()
  spindig()
  y = y + 1
end

if isBig then
  if treeDir == 0 then
    turtle.turnLeft()
    turtle.forward()
    turtle.dig()
    turtle.forward()
    turtle.turnRight()
  else
    turtle.turnRight()
    turtle.forward()
    turtle.dig()
    turtle.forward()
    turtle.turnLeft()
  end
  spindig()
  turtle.forward()
  spindig()

  -- Descend.
  while y ~= 0 do
    turtle.digDown()
    turtle.down()
    spindig()
    y = y - 1
  end
else
  while y ~= 0 do
    turtle.down()
    y = y - 1
  end
end

if isBig then
  if treeDir == 0 then
    turtle.turnRight()
    turtle.forward()
    turtle.forward()
    turtle.turnRight()
    turtle.forward()
    turtle.forward()
    turtle.turnLeft()
    turtle.turnLeft()
  else
    turtle.turnLeft()
    turtle.forward()
    turtle.forward()
    turtle.turnLeft()
    turtle.forward()
    turtle.forward()
    turtle.turnRight()
    turtle.turnRight()
  end
else
  turtle.back()
end

print("We used " .. fuel - turtle.getFuelLevel() .. " units of fuel")