-- Fetch beginning position.
local startPos = npos.getPosition()

-- Find refuel/stop waypoint position.
local forwardStart = 5
for fscnt=1,forwardStart,1 do
	npos.move(npos.directions.FORWARD, true)
end
local routeWaypoint = npos.getPosition()
npos.moveTo(startPos)

local exiting = false

-- Get back to our house safely.
function navigateHome()
	npos.moveTo(routeWaypoint)
	npos.moveTo(startPos)
end

-- Get out of our house.
function exitHome()
	npos.moveTo(routeWaypoint)
end

-- Check if we need to unload.
function isUnloadRequired()
	for i=1,16,1 do
		if(turtle.getItemDetail(i) == nil) then
			return false
		end
	end
	return true
end

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

-- Check our inventory/fuel status.
function blockCheck()
	local cpos = npos.getPosition()

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

		-- Spit everything out.
		npos.setOrientation(npos.orientations.SOUTH)
		print("Dropping items...")
		for dx=1,16,1 do
			turtle.select(dx)

			if(turtle.getItemDetail(dx) == nil) then
				print(dx .. ": Nothing here, cant drop...")
			else
				if(turtle.drop() == false) then
					print(dx .. ": Can't drop anymore. stopping...")
					exiting = true
					return true
				else
					print(dx .. ": Dropped")
				end
			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
					local refuelSuccess = false
					for rfi=1,16,1 do
						turtle.select(rfi)
						if(turtle.refuel()) then
							refuelSuccess = true
						end
					end

					if(refuelSuccess == false) then
						print("Couldn't refuel after fetching from fuel chest")
						exiting = true
						return true
					end
				else
					print("Couldn't refuel anymore, stopping...")
					exiting = true
					return true
				end
			end
		end
	end

	-- Resume where we left off.
	exitHome()
	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

	print("Looks like we're done with this chunk, going home.")
	navigateHome()
end

local args = { ... }
local chunkForward = tonumber(args[1])
local chunkLateral = tonumber(args[2])

-- Leave the comfort of our warm, warm home.
exitHome()

-- Move right the given amount of chunks we're mining from here.
if(chunkLateral > 0) then
	print("Moving laterally a chunk or so")
	npos.turnRight()
	for cl=1,chunkLateral,1 do
		for cli=1,16,1 do
			npos.move(npos.directions.FORWARD, true)
		end
	end
	npos.setOrientation(startPos.o)
	npos.turnLeft()
end

-- Move forward the given amount of chunks we're mining from here.
if(chunkForward > 0) then
	for cf=1,chunkForward,1 do
		print("Moving forward a chunk or so")
		for cfi=1,16,1 do
			npos.move(npos.directions.FORWARD, true)
		end
	end
end

-- Move backwards our 'forward start' amount.
print("Resetting to pre-forward start offset")
npos.turnLeft()
npos.turnLeft()
for fsr=1,forwardStart,1 do npos.move(npos.directions.FORWARD, true) end
npos.turnLeft()
npos.turnLeft()

-- We good to go.
print("Kicking off excavation...")
excavateChunk()
print("Done.")