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 perforate()
    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 blockEnd = 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 = blockDown;
    else
        block = blockUp;
    end

    for n = 1,#block do
        local mov = block[n];
        if (not movement[mov]()) then
            done = true;
            break;
        end
    end
    deepth = deepth - 1;
    if (deepth == 0) then
        break;
    end
end

print("Ended with no errors!");