Digger

-- -----------------------------
-- Digger
-- pastebin get F2HSytaa digger
-- -----------------------------

function checkFuel()
  print('checkFuel')
  while turtle.getFuelLevel() < 10 do
    turtle.select(1)
    turtle.refuel(1)
    if turtle.getFuelLevel() < 10 then
      sleep(5)
    end
    if turtle.getItemCount(1) < 2 then
      goHome()
      goBack()
    end
  end
end

function forward()
  print('forward')
  checkFuel()
  while not turtle.forward() do
    if turtle.detect() then
      turtle.dig()
    else
      turtle.attack()
    end
  end
  if not skip_tracing then
    if direction == 0 then
      x_coord = x_coord + 1
    elseif direction == 1 then
      y_coord = y_coord + 1
    elseif direction == 2 then
      x_coord = x_coord - 1
    elseif direction == 3 then
      y_coord = y_coord - 1
    end
  end
end

function down()
  print('down')
  checkFuel()
  attempts = 0
  for i=1,3 do
    while not turtle.down() do
      if turtle.detectDown() then
        if attempts == 5 then
          goHome()
          exit()
        end
        attempts = attempts + 1
        turtle.digDown()
      else
        turtle.attackDown()
      end
    end
  end
  if not skip_tracing then
    z_coord = z_coord + 1
  end
end

function up()
  print('left')
  checkFuel()
  for i=1,3 do
    while not turtle.up() do
      if turtle.detectUp() then
        turtle.digUp()
      else
        turtle.attackUp()
      end
    end
  end
  if not skip_tracing then
    z_coord = z_coord - 1
  end
end

function right()
  print('right')
  turtle.turnRight()
  direction = direction + 1
  if direction == 4 then
    direction = 0
  end
end

function left()
  print('left')
  turtle.turnLeft()
  direction = direction - 1
  if direction == -1 then
    direction = 3
  end
end

function goHome()
  print('goHome')
  skip_tracing = true
  if direction == 0 then
    turtle.turnLeft()
  elseif direction == 1 then
    turtle.turnLeft()
    turtle.turnLeft()
  elseif direction == 2 then
    turtle.turnRight()
  end
  if z_coord > 1 then
    for i = 1, z_coord - 1 do
      up()
    end
  end
  if y_coord > 1 then
    for i = 1, y_coord do
      forward()
    end
  end
  turtle.turnLeft()
  if x_coord > 1 then
    for i = 1, x_coord do
      forward()
    end
  end
  for i = 2, 16 do
    turtle.select(i)
    turtle.drop()
  end
  turtle.select(1)
  turtle.suckUp()
  turtle.select(2)
  turtle.dropUp()
end

function goBack()
  print('goBack')
  turtle.turnLeft()
  turtle.turnLeft()
  if x_coord > 1 then
    for i = 1, x_coord do
      forward()
    end
  end
  turtle.turnRight()
  if y_coord > 1 then
    for i = 1, y_coord do
      forward()
    end
  end
  if z_coord > 1 then
    for i = 1, z_coord - 1 do
      down()
    end
  end
  if direction == 0 then
    turtle.turnLeft()
  elseif direction == 2 then
    turtle.turnRight()
  elseif direction == 3 then
    turtle.turnRight()
    turtle.turnRight()
  end
  skip_tracing = false
end

function dig()
  print('dig')
  turtle.digDown()
  turtle.digUp()
  turtle.dig()
  if turtle.getItemCount(16) > 0 then
    goHome()
    goBack()
  end
end

term.clear()
term.setCursorPos(1,1)
print("Place fuel in slot 1")
print("Place chest with fuel above the turtle")
print("Place chest for loot behind the turtle")

write("Please enter quarry size ")
lenth = read()
x_coord = 0
y_coord = 0
z_coord = 1
direction = 0
even = true
finished = false
skip_tracing = false
layer_changed = true
forward()
while not finished do
  dig()
  forward()
  if x_coord == tonumber(lenth) or x_coord == 0 then
    if (y_coord == tonumber(lenth) or y_coord == 0) and not layer_changed then
      -- Go to next layer
      down()
      right()
      right()
      layer_changed = true
    else
      -- Go to next line
      layer_changed = false
      if even then
        right()
      else
        left()
      end
      dig()
      forward()
      if even then
        right()
      else
        left()
      end
      even = not even
    end
  end
end
goHome()