local startPos = npos.getPosition()
local exiting = false

function isUnloadRequired()
	for i=1,16,1 do
		if(turtle.getItemDetail(i) == nil) then
			return false
		end
	end
	return true
end

function selectEmptySlot()
	for i=1,16,1 do
		if(turtle.getItemDetail(i) == nil) then
			turtle.select(i)
			return true
		end
	end
	return false
end

function blockCheck()
	local cpos = npos.getPosition()

	if(turtle.getFuelLevel() < 5000 or isUnloadRequired()) then
		print("Making a drop and refuel run")
		npos.moveTo(startPos)

		-- Spit everything out.
		npos.setOrientation(npos.orientations.SOUTH)
		for dx=1,16,1 do
			turtle.select(dx)
			if(turtle.drop() == false) then
				print("Can't drop anymore. stopping...")
				exiting = true
				return true
			end
		end

		-- Check if we need to refuel.
		npos.setOrientation(npos.orientations.WEST)
		if(turtle.getFuelLevel() < 5000) then
			selectEmptySlot()
			while(turtle.getFuelLevel() < 15000) do
				if(turtle.suck() == true) then
					turtle.refuel()
				else
					print("Couldn't refuel anymore, stopping...")
					exiting = true
					return true
				end
			end
		end
	end

	-- Resume where we left off.
	npos.moveTo(cpos)
	npos.setOrientation(cpos.o)
end

function excavateChunk()
	local isForward = true
	local startPos = npos.getPosition()

	w = 16
	h = 16
	l = 16

	for ch=1,16,1 do
		for cw=1,16,1 do
			for cl=1,15,1 do
				npos.move(npos.directions.FORWARD, true)
				blockCheck()

				if(exiting == true) then return true end
			end

			if(cw < w) then
				if(isForward) then
					npos.turnRight()
					npos.move(npos.directions.FORWARD, true)
					blockCheck()
					if(exiting == true) then return true end
					npos.turnRight()

					isForward = false
				else
					npos.turnLeft()
					npos.move(npos.directions.FORWARD, true)
					blockCheck()
					if(exiting == true) then return true end
					npos.turnLeft()

					isForward = true
				end
			end
		end

		if(ch < h) then
			npos.move(npos.directions.UP, true)
			blockCheck()
			if(exiting == true) then return true end
			npos.turnLeft()
			npos.turnLeft()
		end
	end

	for rl=1,h-1,1 do
		npos.move(npos.directions.DOWN, true)
	end

	npos.setOrientation(startPos.o)

	if(curX ~= startPos.x) then
		npos.turnLeft()
		for rsw=1,w-1,1 do npos.move(npos.directions.FORWARD, true) end
		npos.turnLeft()
		for rsl=1,l-1,1 do npos.move(npos.directions.FORWARD, true) end
		npos.setOrientation(startPos.o)
	end
end

print("Kicking off excavation...")
excavateChunk()
print("Done.")