Turtle Tunnel v1.0

local args = {...}

local width = tonumber(args[1])
local height = tonumber(args[2])
local depth = tonumber(args [3])

if table.getn(args) < 3 then
  print('Usage: ' .. shell.getRunningProgram() .. ' <width> <height> <depth>')
  error()
end

if width == nil or height == nil or depth == nil then
  print('Dimensions must be numbers')
  error()
end

if width ~= math.floor(width) or height ~= math.floor(height) or depth ~= math.floor(depth) then
  print('Dimensions must be whole numbers')
  error()
end

if width < 1 or height < 1 or depth < 1 then
  print('All dimensions must be at least 1')
  error()
end

local x = 0
local y = 0 --in minecraft y is really z but the turtles coords are relative to itself so it doesnt matter
local z = 0
local orient = 1

local xDiff = {0, 1, 0, -1}
local yDiff = {1, 0, -1, 0}

function forward()
  x = x + xDiff[orient + 1]
  y = y + yDiff[orient + 1]
  repeat
    moved = turtle.forward()
    if moved == false then
      turtle.dig()
    end
  until moved == true
end

function left()
  orient = orient - 1
  orient = (orient % 4)
  turtle.turnLeft()
end

function right()
  orient = orient + 1
  orient = (orient % 4)
  turtle.turnRight()
end

function up()
  turtle.up()
  z = z + 1
end

function down()
  turtle.down()
  z = z - 1
end

function getCorner() -- 1, 2, 3, 4 = topL, topR, bottomL, bottomR
  if y ~= 0 and z ~= 0 then return 1 end
  if y == 0 and z ~= 0 then return 2 end
  if y ~= 0 and z == 0 then return 3 end
  if y == 0 and z == 0 then return 4 end
end


function digRow()
  if width > 1 then
    repeat
        turtle.dig()
         print(z ~= depth)
         print(getcorner ~= 4)
         if z ~= depth then forward() end
     until y == width - 1 or y == 0
  end
end

function digLayer()
 if height > 1 then
  corner = getCorner()

  if corner == 1 or corner == 3 then
    right()
  else
    left()
  end

  repeat
    digRow()
    left()
    left()

    if corner > 2 then
      if z ~= height then
        turtle.digUp()
        up()
      end
    end

    if corner < 3 then
      if z ~= 0 then
        turtle.digDown()
        down()
      end
    end
  until z == 0 or z == height -1

  digRow()

  while orient ~= 1 do
    if orient == 2 then left()
    else right()
    end
  end
end
end

function digTunnel()
 for n = 1, depth do
   digLayer()
 end
end

digTunnel()