local blacklist = {
	["minecraft:bedrock"] = true,
	["minecraft:stone"] = true,
	["minecraft:cobblestone"] = true,
	["minecraft:dirt"] = true,
	["minecraft:grass"] = true,
	["minecraft:gravel"] = true,
	["minecraft:sand"] = true,
	["minecraft:water"] = true,
	["minecraft:flowing_water"] = true,
	["minecraft:lava"] = true,
	["minecraft:flowing_lava"] = true
}

local tArgs = {...}
if #tArgs ~= 1 then
	print("Usage: ShaftMiner <distance>")
	return
end

local length = tonumber(tArgs[1])
local dist = 0
local dir = 0

local function refuel()
	if turtle.getFuelLevel() < 100 then
		turtle.refuel(1)
	end
end

local function turn(to)
	local rel = (to + 4 - dir) % 4

	if rel == 1 then
		turtle.turnRight()
	elseif rel == 2 then
		turtle.turnRight()
		turtle.turnRight()
	elseif rel == 3 then
		turtle.turnLeft()
	end

	dir = to
end

local function reverse(to)
	if to < 4 then
		return (to + 2) % 4
	elseif to == 4 then
		return 5
	elseif to == 5 then
		return 4
	end
end

local function trymove(to)
	refuel()
	if to < 4 then
		turn(to)
		return turtle.forward()
	elseif to == 4 then
		return turtle.up()
	elseif to == 5 then
		return turtle.down()
	end
end

local function move(to)
	refuel()
	while not trymove(to) do end
end

local function dig(to)
	refuel()
	if to < 4 then
		turn(to)
		turtle.dig()
	elseif to == 4 then
		turtle.digUp()
	elseif to == 5 then
		turtle.digDown()
	end
end

local function moveDig(to)
	while not trymove(to) do dig(to) end
end

local function inspect(to)
	refuel()
	if to < 4 then
		turn(to)
		return turtle.inspect()
	elseif to == 4 then
		return turtle.inspectUp()
	elseif to == 5 then
		return turtle.inspectDown()
	end
end

local function unload()
	print("Unloading items...")

	for n=2,16 do
		turtle.select(n)
		turtle.drop()
	end

	turtle.select(1)

	print("Unloaded!")
end

local function checkFull()
	if turtle.getItemCount(16) > 0 then
		print("Inventory full, returning home...")
		return true
	else
		return false
	end
end

local function dropoff()
	for n=1,dist do move(2) end
	unload()
	for n=1,dist do move(0) end
end

local function mineVein()
	local n = 1
	local stack = {}

	while n > 0 do
		local cur = (stack[n] or -1) + 1
		stack[n] = cur
		if cur < 6 then
			local success, data = inspect(cur)
			if success and not blacklist[data.name] then
				moveDig(cur)
				n = n + 1
			end
		else
			stack[n] = nil
			n = n - 1
			if n > 0 then moveDig(reverse(stack[n])) end
		end
		if checkFull() then
			for i=n-1,1,-1 do moveDig(reverse(stack[i])) end
			dropoff()
			for i=1,n-1 do moveDig(stack[i]) end
		end
	end
end

while dist < length do
	moveDig(0)
	dist = dist + 1
	if checkFull() then dropoff() end
	mineVein()
end

print("Finished shaft, returning home!")

for i=1,dist do move(2) end
unload()
turn(0)

print("Finished!")