shaft

local wallItem = 1 --Top left slot
local ladder = 2 --Top middle slot
local invStart = 3 --Top right slot

local function unload( _bKeepOneFuelStack )
	print( "Unloading items..." )
	for n=invStart,16 do
		if n ~= placeItem then
			turtle.select(n)
			turtle.refuel(0)
			turtle.drop()
		end
	end
end

local function isFull()
	for n=invStart,16 do
		if turtle.getItemCount(n) == 0 then
			--Empty slots
			return false;
		end
	end
	print( "No empty slots left." )
	return true;
end

function refuel( ammount )
	local fuelLevel = turtle.getFuelLevel()
	if fuelLevel == "unlimited" then
		return true
	end

	if turtle.getFuelLevel() < 1 then
		for n=invStart,16 do
			turtle.select(n)
			if turtle.refuel(0) then
				return true
			end
		end
		return false
	end

	return true
end

local function wallAround( slot )
	turtle.select(slot)
	for n=1,4 do
		if not turtle.detect() then
			if turtle.getItemCount() == 0 then
				print("Out of wall items")
				error("Out of wall items")
			else
				turtle.place()
			end
		end
		turtle.turnLeft()
	end
end

local function tryDown()
	if not refuel() then
		print( "Not enough Fuel" )
	end

	while not turtle.down() do
		if not turtle.digDown() then
			if isFull() then
				unload()
			elseif turtle.attackDown() then
				-- Do Nothing
			else
				sleep( 0.5 )
			end
		end
	end
	return true
end

-----------------------------------------------------------------------------
--Main Program
-----------------------------------------------------------------------------

local tArgs = { ... }
if #tArgs ~= 1 then
	print( "My Version Usage: shaft depth" )
	return
end

local depth = tonumber( tArgs[1] )

if not refuel() then
	print( "Out of Fuel" )
	return
end

print( "Digging a shaft" )
for shaftDepth=1,depth do
	print("Shafting " .. shaftDepth .. " / " .. depth)

	wallAround(wallItem)
	tryDown()

	turtle.select(ladder)
	turtle.placeUp()
end

print( "Done" )