3x3 Tunnel

-- 3x3 tunnel script by cowslaw. (Nov. 29, 2015)
-- Usage: tunnel <distance> <offset> <torch>.

-- Arguments:
--   distance: Distance turtle will dig.
--   offset: Distance between starting point and start of tunnel.
--   torch: How far apart torches are placed (default 10).

-- Slottage:
--   Slot 1: Fuel (preferably coal)
--   Slot 2: Torches (optional)

-- Variables (do not change):
turtle.select(1)
tArgs      = { ... }

if #tArgs ~= 3 then
  print("Usage:\n  tunnel <distance> <offset> <torch>\n    Edit for argument descriptions.")
  return
end

togo       = tonumber(tArgs[1]) or 1
offset     = tonumber(tArgs[2]) or 0
placement  = (((tonumber(tArgs[3])) or 10) + 1) or 6
torch      = 0
amount     = 0
percentage = 0
outcome    = 0

-- Functions
function digForward()
  checkFuel()

  repeat
    turtle.dig()
    sleep(0.25)
  until turtle.detect() == false

  checkFront()
end

function checkFuel()
  if turtle.getFuelLevel() <= 500 then
    turtle.select(1)
    turtle.refuel(1)
  end
end

function turnAround()
  turtle.turnRight()
  turtle.turnRight()
end

function checkTopBottom()
  if turtle.detectUp() then
    turtle.digUp()
  end
  if turtle.detectDown() then
    turtle.digDown()
  end
end

function checkFront()
  if turtle.forward() == false then
    repeat
      turtle.attack()
      turtle.dig()
      sleep(0.25)
    until turtle.forward() == true
  end
end

function checkInventoryFull(currentDistance)
  if turtle.getItemCount(16) > 0 then
    turnAround()

    for b = 1, currentDistance do
      checkFuel()
      checkFront()
    end

    for e = 3, 16 do
      turtle.select(e)
      turtle.dropDown()
    end

    turnAround()

    for b = 1, currentDistance do
      checkFuel()
      checkFront()
    end
  end
end

-- Main Script
checkFuel()

if offset > 0 then
  for o = 1, offset do
    turtle.forward()
  end
end

for i = 1, togo do
  amount = amount + 1
  torch = torch + 1
  percentage = percentage + 1
  outcome = percentage / togo * 100
  term.clear()
  term.setCursorPos(1, 1)
  print("On block " .. amount .. " of " .. togo .. ".")
  print(math.floor(outcome, 3) .. "% complete.")
  checkFuel()
  digForward()
  checkTopBottom()
  turtle.turnRight()
  digForward()
  checkTopBottom()
  turnAround()
  checkFront()
  digForward()
  checkTopBottom()
  turnAround()
  checkFront()
  turtle.turnLeft()

  if torch == placement then
    turtle.select(2)
    turtle.down()
    turnAround()
    turtle.place()
    turnAround()
    turtle.up()
    turtle.select(1)
    torch = 0
  end

  checkInventoryFull((offset + amount))

  outcome = 0
end

turnAround()

for b = 1, (togo + offset) do
  checkFuel()
  checkFront()
end

for e = 3, 16 do
  turtle.select(e)
  turtle.dropDown()
end

turnAround()

print("Tunnel finished.")