local lib = {}
lib.blocks = {}

lib.blocks["minecraft:cobble"] = "path"
lib.blocks["minecraft:stone"] = "refuel"
lib.blocks["minecraft:sand"] = "tree"
lib.blocks["minecraft:gravel"] = "clear"
lib.blocks["minecraft:clay"] = "left"
lib.blocks["minecraft:pumpkin"] = "right"
lib.blocks["minecraft:bedrock"] = "stop"
lib.tree_distance = 3
lib.tree_size = 5
lib.needed_fuel = 800

lib.tick = 1

function lib.coal_to_get()
	fuel_stock = turtle.getFuel()
	fuel_to_get = needed_fuel - fuel_stock
	coal_to_get = math.ceil(fuel_to_get/80)
	return math.max(coal_to_get, 0)
end

function lib.refuel()
	turtle.turnLeft()
	turtle.select(1)
	to_get = lib.coal_to_get()
	while to_get > 0 do
		while not turtle.suck(to_get) do sleep(lib.tick) end
		turtle.refuel()
		to_get = lib.coal_to_get()
	turtle.turnRight()
end

function lib.clear()
	turtle.turnLeft()
	for i = 1, 16 do
		turtle.select(i)
		turtle.drop()
	end
	turtle.turnRight()
end

function lib.tree()
	turtle.turnLeft()
	for i=1, lib.tree_distance do lib.digForward() end
	for i=1, lib.tree_size do lib.digUp() end
	for i=1, lib.tree_size do turtle.down() end
	for i=1, lib.tree_distance do turtle.back() end
	turtle.turnRight()
end

function lib.analyse(meta)
	if meta == nil then return "unknown" end
	bind = lib.blocks[meta.name]
	if bind == nil then return "unknown" end
	return bind
end

function lib.getBlock()
	res, meta = turtle.inspectDown()
	return lib.analyse(meta)
end

function lib.inspect()
	res, meta = turtle.inspect()
	return lib.analyse(meta)
end

function lib.init()
	while not(turtle.detectDown()) do turtle.down() end

	block = lib.getBlock()
	while block == "unknown" do
		turtle.back()
		block = lib.getBlock()
	end

	if block == "stop" then
		return false
	elseif block == "tree" then
		turtle.turnRight()
	elseif block == "refuel" or block == "clear" then
		while not(lib.inspect() == "chest") then turtle.turnLeft() end
		turtle.turnRight()
	else
		turtle.forward()
		sblock = lib.getBlock()
		while not(sblock == "flag") then
			turtle.back()
			turtle.turnRight()
			turtle.forward()
			sblock = lib.getBlock()
		end
	end
	return true
end

function lib.execute()
	block = lib.getBlock()
	if block == "tree" then lib.tree()
	elseif block == "left" then turtle.turnLeft()
	elseif block == "right" then turtle.turnRight()
	elseif block == "refuel" then lib.refuel()
	elseif block == "clear" then lib.clear()
	else block == "stop" then return false end
	turtle.forward()
	return true
end

function lib.loop()
	running = lib.init()
	while running do
		running = lib.execute()
	end
end

lib.loop()