CC Advanced Lumberjack

tArgs = {...}
if #tArgs ~= 1 then
  print("Usage: lumberjack <length>")
  return
end

length = tonumber(tArgs[1])
if length < 3 then
  print("Length must be greater than 2")
  return
end

length = length - 1

depth = 0
xPos, zPos = 0, 0
xDir, zDir = 0, 1

function readProgress()
  if not fs.exists("/tmp/prog.sav") then
    return 1, 1
  end

  local file = fs.open("/tmp/prog.sav", "r")

  local i = tonumber(file.readLine())
  local j = tonumber(file.readLine())

  length = tonumber(file.readLine())
  depth = tonumber(file.readLine())
  xPos = tonumber(file.readLine())
  zPos = tonumber(file.readLine())
  xDir = tonumber(file.readLine())
  zDir = tonumber(file.readLine())

  file.close()

  return i, j
end

function writeProgress(i, j)
  if not fs.exists("/tmp/") then
    fs.makeDir("/tmp/")
  end

  local file = fs.open("/tmp/prog.sav", "w")

  file.writeLine(i)
  file.writeLine(j)
  file.writeLine(length)
  file.writeLine(depth)
  file.writeLine(xPos)
  file.writeLine(zPos)
  file.writeLine(xDir)
  file.writeLine(zDir)

  file.close()
end

function isItemLeaves(item)
  local i = string.find(item.name, ":") + 1
  local name = string.sub(item.name, i)
  return name == "leaves"
end

function isLeaves()
  local success, item = turtle.inspect()
  if success then
    return isItemLeaves(item)
  else
    return false
  end
end

function isLeavesUp()
  local success, item = turtle.inspectUp()
  if success then
    return isItemLeaves(item)
  else
    return false
  end
end

function isLeavesDown()
  local success, item = turtle.inspectDown()
  if success then
    return isItemLeaves(item)
  else
    return false
  end
end

function itemIsDirt(item)
  local i = string.find(item.name, ":") + 1
  local name = string.sub(item.name, i)
  return name == "dirt"
end

function isItemALog(item)
  local i = string.find(item.name, ":") + 1
  local name = string.sub(item.name, i)
  return name == "log"
end

function isLog()
  local success, item = turtle.inspect()
  if success then
    return isItemALog(item)
  else
    return false
  end
end

function isLogUp()
  local success, item = turtle.inspectUp()
  if success then
    return isItemALog(item)
  else
    return false
  end
end

function isLogDown()
  local success, item = turtle.inspectDown()
  if success then
    return isItemALog(item)
  else
    return false
  end
end

function forward()
  return turtle.forward()
end

function back()
  return turtle.back()
end

function up()
  local success = turtle.up()
  if success then
    depth = depth + 1
  end
  return success
end

function down()
  local success = turtle.down()
  if success then
    depth = depth - 1
  end
  return success
end

function turnLeft()
  xDir, zDir = -zDir, xDir
  return turtle.turnLeft()
end

function turnRight()
  xDir, zDir = zDir, -xDir
  return turtle.turnRight()
end

function toGround()
  while down() do end
end

function startFelling()
  while isLog() do
    turtle.digDown()
    down()
  end

  up()
  for i = 1, 16 do
    if itemIsDirt(turtle.getItemDetail(i)) then
      turtle.select(i)
      turtle.placeDown()
      break
    end
  end

  if isLog() then
    turtle.dig()
    forward()
  end

  while isLogUp() do
    turtle.digUp()
    up()
  end

  toGround()

  while isLogDown() do
    turtle.digDown()
    down()
  end

  back()
end

function tryForward()
  while not forward() do
    if isLog() then
      startFelling()
    elseif isLeaves() then
      turtle.dig()
    elseif turtle.detectUp() and not isLogUp() then
      turtle.digUp()
      up()
    elseif not turtle.detectUp() then
      up()
    elseif isLogUp() then
      back()
      turtle.digUp()
      up()
      turtle.startFelling()
    end
  end

  xPos = xPos + xDir
  zPos = zPos + zDir
  toGround()
end

function edgeTurnRight()
  turnRight()
  tryForward()
  toGround()
  turnRight()
end

function edgeTurnLeft()
  turnLeft()
  tryForward()
  toGround()
  turnLeft()
end

function ai()
  local startI, startJ = readProgress()

  for i = startI, length + 1 do
    for j = startJ, length do
      tryForward()
      writeProgress(i, j)
    end

    startJ = 1
    if i ~= length + 1 then
      if i % 2 == 0 then
        edgeTurnLeft()
      else
        edgeTurnRight()
      end
    end

    writeProgress(i, 1)
  end
end

function goto(x, y, z, xD, zD)
  while depth ~= y do
    if depth > y then
      if not down() then
        turtle.digDown()
        turtle.attackDown()
      end
    else
      if not up() then
        turtle.digUp()
        turtle.attackUp()
      end
    end
  end
  if xPos > x then
    while xDir ~= -1 do
      turnLeft()
    end
    while xPos > x do
      if forward() then
        xPos = xPos - 1
      else
        turtle.dig()
            turtle.attack()
      end
    end
  elseif xPos < x then
    while xDir ~= 1 do
      turnLeft()
    end
    while xPos > x do
      if forward() then
        xPos = xPos - 1
      else
        turtle.dig()
        turtle.attack()
      end
    end
  end
  if zPos > z then
    while zDir ~= -1 do
      turnLeft()
    end
    while zPos > z do
      if forward() then
        zPos = zPos - 1
      else
        turtle.dig()
            turtle.attack()
      end
    end
  elseif zPos < z then
    while zDir ~= 1 do
      turnLeft()
    end
    while zPos > z do
      if forward() then
        zPos = zPos - 1
      else
        turtle.dig()
            turtle.attack()
      end
    end
  end
  while zDir ~= zD or xDir ~= xD do
     turnLeft()
  end
end

function dumpInv()
  goto(0, 0, 0, 0, -1)
  for i = 16, 1, -1 do
    turtle.select(i)
    if turtle.getItemCount() ~= 0 then
      if itemIsDirt(turtle.getItemDetail()) then
        if i == 1 then
          if turtle.getItemCount() > 10 then
            turtle.drop(turtle.getItemCount() - 10)
          end
        else
          turtle.transferTo(1)
        end
      else
        turtle.drop()
      end
    end
  end
end

ai()
fs.delete("/tmp/prog.sav")
dumpInv()
turtle.select(1)
goto(0, 0, 0, 0, -1)