Turtle buildBox

-- pastebin get QfSCbRgH buildBox

-- Ask how each side is
print("How many blocks per side?")
local side = io.read()
side = tonumber(side)

local blocksNeeded = (side * 2) + ((side - 2) * 2)

print("I will need " .. blocksNeeded .. " blocks.")
print("Type 'Start' when ready")

local go = io.read()

local blockCount = side - 1
local selected = 1
local fuel = 16 -- Put some coal into the bottom-right cell
local itemCount = turtle.getItemCount(selected)

--[[
* Check to see if refueling is needed
]]
local function ifRefuel()
	if turtle.getFuelLevel() < side then
		turtle.select(fuel)
		turtle.refuel(1)
		turtle.select(selected)
	end
end

if go == "Start" then
	-- Do we need to step up?
	if turtle.detectDown() then
		ifRefuel()
		turtle.up()
	end

	-- Select the starting cell
	turtle.select(selected)

	local s = 0
	local j = 0
	while s < 4 do
		-- Prepare turtle ro do one side of the box
		turtle.select(selected)
		ifRefuel()

		if s == 3 then
			-- Last side
			blockCount = blockCount - 1
		end

		j = 0
		while j < blockCount do
			-- Are we clear to place something?
			if turtle.detectDown() then
				turtle.digDown()
			end

			-- Place block
			turtle.placeDown()

			-- Step forward
			if turtle.detect() then
				turtle.dig()
			end

			turtle.forward()

			itemCount = turtle.getItemCount(selected)

			if itemCount == 0 then
				-- Out of items; Switch cells
				selected = selected + 1
				turtle.select(selected)
			end

			j = j + 1
		end

		if s < 3 then
			-- Prepare for the next side
			turtle.turnLeft()
		end

		s = s + 1
	end

	-- Place the last block to complete the box
	if turtle.detectDown() then
		turtle.digDown()
	end

	turtle.placeDown()
	turtle.forward()
else
	print("Terminating")
end