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

local deepth = tArgs[1];

-- left: 1
-- forward: 2
-- right: 3

local direction = 2;
local xPos = -1;
local yPos = 0;
local zPos = 0;

local function turnLeft()
	if (direction == 1) then
		return false
	end
	turtle.turnLeft();
	direction = direction - 1;	
	return true;
end

local function turnRight()
	if (direction == 3) then
		return false
	end
	turtle.turnRight();
	direction = direction + 1;
	return true;
end

local function perforate()
	local result = turtle.dig();
	turtle.drop();
	os.sleep(0.8);
	return result;
end

local function perforateDown()
	local result = turtle.digDown();
	turtle.drop();
	os.sleep(0.8);
	return result;
end

local function advance()
	if (turtle.detect()) then
		if (not perforate()) then
			return false;
		end		
	end
	turtle.forward();
	if (direction == 2) then
		xPos = xPos + 1;
	elseif (direction == 1) then
		yPos = yPos - 1;
	elseif (direction == 3) then
		yPos = yPos + 1;
	end		
	return true;
end

local function advanceUp()
	turtle.up();
	zPos = zPos + 1;
	return true;
end

local function advanceDown()
	if (turtle.detectDown()) then
		if (not perforateDown()) then
			return false;
		end		
	end

	turtle.down();
	zPos = zPos - 1;
	return true;
end

local isDown = true;
local done     = false;

turnRight();


local movement = {}
movement[0] = advance;
movement[1] = advanceUp;
movement[2] = advanceDown;
movement[3] = turnLeft;
movement[4] = turnRight;

local blockUp = {3,0,2,3,0,0,0,4,4,1,0,0,0,3,3,1,0,0,0,4,4,1,0,0,0};
local blockDown = {3,2,0,3,0,0,0,2,4,4,0,0,0,2,3,3,0,0,0,2,4,4,0,0,0};

while (not done) do
	local block;
	if (isDown) then
		block = blockUp;
	else
		block = blockDown;
	end
	
	for n = 1,#block do
		local mov = block[n];
		if (not movement[mov]()) then
			print("failed at ",n,isDown);
			done = true;
			break;
		end
	end
	isDown = not isDown;
	deepth = deepth - 1;
	if (deepth == 0) then
		break;
	end
end

print("Ended with no errors!");