-------------------------------------
-- Maze generation script
-------------------------------------
-- A test by @Starbeamrainbowlabs

local M = {}

-- Intelligent table printing function: http://coronalabs.com/blog/2014/09/02/tutorial-printing-table-contents/

-- if arg[1] ~= nil then
--         width = tonumber(arg[1])
-- else
--         width = 35
-- end
-- if arg[2] ~= nil then
--         height = tonumber(arg[2])
-- else
--         height = 15
-- end

----------------------------------
-- function to print out the world
----------------------------------
function M.printspace(space, w, h)
        for y = 0, h - 1, 1 do
                local line = ""
                for x = 0, w - 1, 1 do
                        line = line .. space[y][x]
                end
                print(line)
        end
end

-- Initialise the world

function M.generate_maze(seed, width, height)
    start_time = os.clock()
	-- minetest.log("action", "width: "..width..", height: "..height)
	math.randomseed(seed) -- seed the random number generator with the system clock

	width = width - 1
	height = height - 1

	local world = {}
	for y = 0, height, 1 do
		world[y] = {}
		for x = 0, width, 1 do
			world[y][x] = "#"
		end
	end

	-- do a random walk to create pathways
	local nodes = {} -- the nodes left that we haven't investigated
	local curnode = 1 -- the node we are currently operating on
	local cx, cy = 1, 1 -- our current position
	table.insert(nodes, { x = cx, y = cy })
	world[cy][cx] = " "
	while #nodes > 0 do
		-- io.write("Nodes left: " .. curnode .. "\r")
		--print("Nodes left: " .. #nodes)
		--print("Currently at (" .. cx .. ", " .. cy .. ")")

		local directions = "" -- the different directions we can move
		if cy - 2 > 0 and world[cy - 2][cx] == "#" then
			directions = directions .. "u"
		end
		if cy + 2 < height and world[cy + 2][cx] == "#" then
			directions = directions .. "d"
		end
		if cx - 2 > 0 and world[cy][cx - 2] == "#" then
			directions = directions .. "l"
		end
		if cx + 2 < width and world[cy][cx + 2] == "#" then
			directions = directions .. "r"
		end
		--print("radar output: '" .. directions .. "' (length: " .. #directions .. "), curnode: " .. curnode)
		if #directions > 0 then
			-- we still have somewhere that we can go
			--print("This node is not a dead end yet.")
			local curdirnum = math.random(1, #directions)
			local curdir = string.sub(directions, curdirnum, curdirnum)
			if curdir == "u" then
				world[cy - 1][cx] = " "
				world[cy - 2][cx] = " "
				cy = cy - 2
			elseif curdir == "d" then
				world[cy + 1][cx] = " "
				world[cy + 2][cx] = " "
				cy = cy + 2
			elseif curdir == "l" then
				world[cy][cx - 1] = " "
				world[cy][cx - 2] = " "
				cx = cx - 2
			elseif curdir == "r" then
				world[cy][cx + 1] = " "
				world[cy][cx + 2] = " "
				cx = cx + 2
			end

			table.insert(nodes, { x = cx, y = cy })
		else
			--print("The node at " .. curnode .. " is a dead end.")
			table.remove(nodes, curnode)
			if #nodes > 0 then
				--print("performing teleport.");
				curnode = math.random(1, #nodes)
				--print("New node: " .. curnode)
				-- print("Nodes table: ")
				-- print_r(nodes)
				cx = nodes[curnode]["x"]
				cy = nodes[curnode]["y"]
			else
				--print("Maze generation complete, no teleportation necessary.")
			end
		end
		--printspace(world, width, height)
	end
    
    end_time = os.clock()
    
	return world, (end_time - start_time) * 1000
end

-- local world, time   = generate_maze(os.time(), width, height)
-- printspace(world, width, height)
-- print("Generation completed in " .. time .. "s.")

return M