minetest.register_chatcommand("maze", {
	params = "<size_x> <size_y> <#floors> <material_floor> <material_wall> <material_ceiling>",
	privs = {server = true},
	description = "Create a maze near your position",
	func = function(name, param)
		local t1 = os.clock()
		math.randomseed(os.time())
		local player_pos = minetest.get_player_by_name(name):getpos()
		local found, _, maze_size_x_st, maze_size_y_st, maze_size_l_st, material_floor, material_wall, material_ceiling = param:find("(%d+)%s+(%d+)%s+(%d+)%s+([^%s]+)%s+([^%s]+)%s+([^%s]+)")
		local min_size = 11
		local maze_size_x = tonumber(maze_size_x_st)
		maze_size_x = maze_size_x or 20
		maze_size_x = math.max(maze_size_x, min_size)
		local maze_size_y = tonumber(maze_size_y_st)
		maze_size_y = maze_size_y or 20
		maze_size_y = math.max(maze_size_y, min_size)
		local maze_size_l = tonumber(maze_size_l_st)
		maze_size_l = maze_size_l or 3
		maze_size_l = math.max(maze_size_l, 1)
		-- check if chosen material exists
		if not minetest.registered_nodes[material_floor] then
			material_floor = "default:cobble"
		end
		material_floor = material_floor or "default:cobble"
		if not minetest.registered_nodes[material_wall] then
			material_wall = "default:cobble"
		end
		material_wall = material_wall or "default:cobble"
		if not minetest.registered_nodes[material_ceiling] then
			material_ceiling = "default:cobble"
		end
		material_ceiling = material_ceiling or "default:cobble"

		minetest.chat_send_player(name, "Try to build " .. maze_size_x .. " * " .. maze_size_y .. " * " .. maze_size_l .. " maze.  F:" .. material_floor .. " W:" .. material_wall .. " C:" .. material_ceiling)

		local maze = {}
		for l = 0, maze_size_l-1 do
			maze[l] = {}
			for x = 0, maze_size_x-1 do
				maze[l][x] = {}
				for y = 0, maze_size_y-1 do
					maze[l][x][y] = true -- everywhere walls
				end
			end
		end

-- create maze map
		local start_x = 0
		local start_y = math.floor(maze_size_y/2)
		local start_l = 0
		local pos_x = start_x
		local pos_y = start_y
		local pos_l = start_l
		maze[pos_l][pos_x][pos_y] = false -- the entrance
		local moves = {}
		local updowns = {}
		local possible_ways = {}
		local direction = ""
		local pos = {x = 0, y = 0, l = 0}
		local forward = true
		local return_count = 0
		local treasure_x = 0
		local treasure_y = 0
		local treasure_l = 0
		local dead_end = {}
		table.insert(moves, {x = pos_x, y = pos_y, l = pos_l})
		-- print(#moves .. " " .. moves[1].x .. " " .. moves[1].y)
		repeat
			possible_ways = {}
			-- is D possible?
			if 
				pos_x > 1 and pos_x < maze_size_x - 1 and pos_y > 1 and pos_y < maze_size_y - 1 and
				pos_l < maze_size_l - 1 and
				maze[pos_l + 1][pos_x - 1][pos_y - 1] and
				maze[pos_l + 1][pos_x - 1][pos_y] and
				maze[pos_l + 1][pos_x - 1][pos_y + 1] and
				maze[pos_l + 1][pos_x][pos_y - 1] and
				maze[pos_l + 1][pos_x][pos_y] and
				maze[pos_l + 1][pos_x][pos_y + 2] and
				maze[pos_l + 1][pos_x + 1][pos_y - 1] and
				maze[pos_l + 1][pos_x + 1][pos_y] and
				maze[pos_l + 1][pos_x + 1][pos_y + 1]
			then
				table.insert(possible_ways, "D")
			end
			-- is U possible?
			if
				pos_x > 1 and pos_x < maze_size_x - 1 and pos_y > 1 and pos_y < maze_size_y - 1 and
				pos_l > 0 and
				maze[pos_l - 1][pos_x - 1][pos_y - 1] and
				maze[pos_l - 1][pos_x - 1][pos_y] and
				maze[pos_l - 1][pos_x - 1][pos_y + 1] and
				maze[pos_l - 1][pos_x][pos_y - 1] and
				maze[pos_l - 1][pos_x][pos_y] and
				maze[pos_l - 1][pos_x][pos_y + 2] and
				maze[pos_l - 1][pos_x + 1][pos_y - 1] and
				maze[pos_l - 1][pos_x + 1][pos_y] and
				maze[pos_l - 1][pos_x + 1][pos_y + 1]
			then
				table.insert(possible_ways, "U")
			end
			-- is N possible?
			if
				pos_y - 2 >= 0 and pos_x - 1 >= 0 and pos_x + 1 < maze_size_x and 
				maze[pos_l][pos_x][pos_y - 1] and -- N is wall
				maze[pos_l][pos_x][pos_y - 2] and -- N from N is wall
				maze[pos_l][pos_x - 1][pos_y - 2] and -- NW from N is wall
				maze[pos_l][pos_x + 1][pos_y - 2] and -- NE from N is wall
				maze[pos_l][pos_x - 1][pos_y - 1] and -- W from N is wall
				maze[pos_l][pos_x + 1][pos_y - 1] -- E from N is wall
			then
				table.insert(possible_ways, "N")
				table.insert(possible_ways, "N") -- twice as possible as U and D
			end
			-- is E possible?
			if
				pos_x + 2 < maze_size_x and pos_y - 1 >= 0 and pos_y + 1 < maze_size_y and 
				maze[pos_l][pos_x + 1][pos_y] and -- E is wall
				maze[pos_l][pos_x + 2][pos_y] and -- E from E is wall
				maze[pos_l][pos_x + 2][pos_y - 1] and -- NE from E is wall
				maze[pos_l][pos_x + 2][pos_y + 1] and -- SE from E is wall
				maze[pos_l][pos_x + 1][pos_y - 1] and -- N from E is wall
				maze[pos_l][pos_x + 1][pos_y + 1] -- S from E is wall
			then
				table.insert(possible_ways, "E")
				table.insert(possible_ways, "E") -- twice as possible as U and D
			end
			-- is S possible?
			if
				pos_y + 2 < maze_size_y and pos_x - 1 >= 0 and pos_x + 1 < maze_size_x and 
				maze[pos_l][pos_x][pos_y + 1] and -- S is wall
				maze[pos_l][pos_x][pos_y + 2] and -- S from S is wall
				maze[pos_l][pos_x - 1][pos_y + 2] and -- SW from S is wall
				maze[pos_l][pos_x + 1][pos_y + 2] and -- SE from S is wall
				maze[pos_l][pos_x - 1][pos_y + 1] and -- W from S is wall
				maze[pos_l][pos_x + 1][pos_y + 1] -- E from S is wall
			then
				table.insert(possible_ways, "S")
				table.insert(possible_ways, "S") -- twice as possible as U and D
			end
			-- is W possible?
			if
				pos_x - 2 >= 0 and pos_y - 1 >= 0 and pos_y + 1 < maze_size_y and 
				maze[pos_l][pos_x - 1][pos_y] and -- W is wall
				maze[pos_l][pos_x - 2][pos_y] and -- W from W is wall
				maze[pos_l][pos_x - 2][pos_y - 1] and -- NW from W is wall
				maze[pos_l][pos_x - 2][pos_y + 1] and -- SW from W is wall
				maze[pos_l][pos_x - 1][pos_y - 1] and -- N from W is wall
				maze[pos_l][pos_x - 1][pos_y + 1] -- S from W is wall
			then
				table.insert(possible_ways, "W")
				table.insert(possible_ways, "W") -- twice as possible as U and D
			end
			if #possible_ways > 0 then
				forward = true
				direction = possible_ways[math.random(# possible_ways)]
				if direction == "N" then 
					pos_y = pos_y - 1
				elseif direction == "E" then 
					pos_x = pos_x + 1
				elseif direction == "S" then 
					pos_y = pos_y + 1
				elseif direction == "W" then 
					pos_x = pos_x - 1
				elseif direction == "D" then 
					table.insert(updowns, {x = pos_x, y = pos_y, l = pos_l}) -- mark way down
					pos_l = pos_l + 1
				elseif direction == "U" then 
					pos_l = pos_l - 1
					table.insert(updowns, {x = pos_x, y = pos_y, l = pos_l}) -- mark way up = down from level above
				end
				table.insert(moves, {x = pos_x, y = pos_y, l = pos_l})
				maze[pos_l][pos_x][pos_y] = false
				-- print(# possible_ways .. " " .. direction)
			else -- there is no possible way forward
				if forward then -- the last step was forward, now back, so we're in a dead end
					-- mark dead end for possible braid
					if not maze[pos_l][pos_x - 1][pos_y] then -- dead end to E, only way is W
						table.insert(dead_end, {x = pos_x, y = pos_y, l = pos_l, dx = 1, dy = 0})
					elseif not maze[pos_l][pos_x + 1][pos_y] then -- dead end to W, only way is E
						table.insert(dead_end, {x = pos_x, y = pos_y, l = pos_l, dx = -1, dy = 0})
					elseif not maze[pos_l][pos_x][pos_y - 1] then -- dead end to S, only way is N
						table.insert(dead_end, {x = pos_x, y = pos_y, l = pos_l, dx = 0, dy = 1})
					elseif not maze[pos_l][pos_x][pos_y + 1] then -- dead end to N, only way is S
						table.insert(dead_end, {x = pos_x, y = pos_y, l = pos_l, dx = 0, dy = -1})
					end
					-- third time returning is location of treasure, if there are three ways back else it's somewhere before
					if return_count <= 3 then
						-- print("place treasure")
						treasure_x = pos_x
						treasure_y = pos_y
						treasure_l = pos_l
					end
					return_count = return_count + 1
					forward = false
				end
				pos = table.remove(moves)
				pos_x = pos.x
				pos_y = pos.y
				pos_l = pos.l
				-- print("get back to " .. pos_x .. " / " .. pos_y .. " / " .. pos_l .. " to find another way from there")
			end
		until pos_x == start_x and pos_y == start_y
-- create partial braid maze, about 20%
		for _, braid_pos in pairs(dead_end) do
			if braid_pos.x ~= treasure_x or braid_pos.y ~= treasure_y or braid_pos.l ~= treasure_l then -- treasure remains in dead end
				-- print(braid_pos.x.."/"..braid_pos.y.."/"..braid_pos.l.." "..braid_pos.dx.."/"..braid_pos.dy)
				x = braid_pos.x + braid_pos.dx * 2
				y = braid_pos.y + braid_pos.dy * 2
				if math.random(5) == 1 and x > 0 and x < maze_size_x - 1 and y > 0 and y < maze_size_y - 1 and not maze[braid_pos.l][x][y] then
					-- remove wall if behind is corridor with 20% chance
					maze[braid_pos.l][braid_pos.x + braid_pos.dx][braid_pos.y + braid_pos.dy] = false
					print("removed "..braid_pos.l.."/"..braid_pos.x + braid_pos.dx.."/"..braid_pos.y + braid_pos.dy)
				end
			end
		end
-- create exit on opposite end of maze and make sure it is reachable
		local exit_x = maze_size_x - 1 -- exit always on opposite side of maze
		local exit_y = math.random(maze_size_y - 3) + 1
		local exit_l = math.random(maze_size_l) - 1
		local exit_reachable = false
		repeat
			maze[exit_l][exit_x][exit_y] = false
			exit_reachable = not maze[exit_l][exit_x - 1][exit_y] or not maze[exit_l][exit_x][exit_y - 1] or not maze[exit_l][exit_x][exit_y + 1]
			exit_x = exit_x - 1
		until exit_reachable

-- get transform factors to place the maze in "look_dir" of player
		local player_dir = minetest.get_player_by_name(name):get_look_dir()
		local cosine = 1
		local sine = 0
		if math.abs(player_dir.x) > math.abs(player_dir.z) then 
			if player_dir.x > 0 then 
				cosine = 1
				sine = 0
			else
				cosine = -1
				sine = 0
			end
		else
			if player_dir.z < 0 then 
				cosine = 0
				sine = -1
			else
				cosine = 0
				sine = 1
			end
		end
		-- print (cosine .. " " .. sine)

-- build maze in minetest-world
		local offset_x = 1
		local offset_y = 1
		local line = ""
		local pos = {x = 0, y = 0, z = 0}
		local change_level_down = false
		local change_level_up = false
		local ladder_direction = 2
		for l = maze_size_l-1, 0, -1 do
			for y = 0, maze_size_y-1 do
				if l == 0 and y == math.floor(maze_size_y / 2) then line = "<-" else line = "  " end
				for x = 0, maze_size_x - 1, 1 do
					-- rotate the maze in players view-direction and move it to his position
					pos.x = cosine * (x + 2) - sine * (y - math.floor(maze_size_y / 2)) + player_pos.x
					pos.z = sine * (x + 2) + cosine * (y - math.floor(maze_size_y / 2)) + player_pos.z
					pos.y = math.floor(player_pos.y + 0.5) - 1 - 3 * l
					
					change_level_down = false
					change_level_up = false
					for i, v in ipairs(updowns) do
						if v.x == x and v.y == y and v.l == l then 
							change_level_down = true
							-- find direction for the ladders
							ladder_direction = 2
							if maze[l][x - 1][y] and maze[l + 1][x - 1][y] then ladder_direction = 3 end
							if maze[l][x + 1][y] and maze[l + 1][x + 1][y] then ladder_direction = 2 end
							if maze[l][x][y - 1] and maze[l + 1][x][y - 1] then ladder_direction = 5 end
							if maze[l][x][y + 1] and maze[l + 1][x][y + 1] then ladder_direction = 4 end
						end
						if v.x == x and v.y == y and v.l == l - 1 then
							change_level_up = true
							-- find direction for the ladders
							ladder_direction = 2
							if maze[l][x - 1][y] then ladder_direction = 3 end
							if maze[l][x + 1][y] then ladder_direction = 2 end
							if maze[l][x][y - 1] then ladder_direction = 5 end
							if maze[l][x][y + 1] then ladder_direction = 4 end
						end
					end
					-- rotate direction for the ladders
					if cosine == -1 then
						if ladder_direction == 2 then ladder_direction = 3
						elseif ladder_direction == 3 then ladder_direction = 2
						elseif ladder_direction == 4 then ladder_direction = 5
						elseif ladder_direction == 5 then ladder_direction = 4 end
					end
					if sine == -1 then
						if ladder_direction == 2 then ladder_direction = 5
						elseif ladder_direction == 3 then ladder_direction = 4
						elseif ladder_direction == 4 then ladder_direction = 2
						elseif ladder_direction == 5 then ladder_direction = 3 end
					end
					if sine == 1 then
						if ladder_direction == 2 then ladder_direction = 4
						elseif ladder_direction == 3 then ladder_direction = 5
						elseif ladder_direction == 4 then ladder_direction = 3
						elseif ladder_direction == 5 then ladder_direction = 2 end
					end
					if not change_level_down then 
						minetest.add_node(pos, {type = "node", name = material_floor})
					end
					if maze[l][x][y] then 
						line = "X" .. line
						pos.y = pos.y + 1
						minetest.add_node(pos, {type = "node", name = material_wall})
						pos.y = pos.y + 1
						minetest.add_node(pos, {type = "node", name = material_wall})
					else
						line = " " .. line
						pos.y = pos.y + 1
						minetest.add_node(pos, {type = "node", name = "air"})
						-- if change_level_down then minetest.add_node(pos, {type = "node", name = "default:ladder", param2 = ladder_direction}) end
						if change_level_up then minetest.add_node(pos, {type = "node", name = "default:ladder", param2 = ladder_direction}) end
						pos.y = pos.y + 1
						minetest.add_node(pos, {type = "node", name = "air"})
						if change_level_up then 
							minetest.add_node(pos, {type = "node", name = "default:ladder", param2 = ladder_direction}) 
						else 
							if change_level_down then 
								minetest.add_node(pos, {type = "node", name = "default:torch", param2 = ladder_direction})
							elseif (math.random(20) == 1) then 
								minetest.add_node(pos, {type = "node", name = "default:torch", param2 = 6}) 
							end
						end
					end
					pos.y = pos.y + 1
					if change_level_up then 
						minetest.add_node(pos, {type = "node", name = "air"})
						minetest.add_node(pos, {type = "node", name = "default:ladder", param2 = ladder_direction})
					else
						minetest.add_node(pos, {type = "node", name = material_ceiling})
					end
				end
				if l==exit_l and y==exit_y then line = "<-" .. line else line = "  " .. line end
				print(line)
			end
		end
		-- if exit is underground, dig a hole to surface
		pos.x = cosine * (maze_size_x + 2) - sine * (exit_y - math.floor(maze_size_y / 2)) + player_pos.x
		pos.z = sine * (maze_size_x + 2) + cosine * (exit_y - math.floor(maze_size_y / 2)) + player_pos.z
		pos.y = math.floor(player_pos.y + 0.5) - 3 * exit_l
		ladder_direction = 2
		if cosine == -1 then ladder_direction = 3 end
		if sine == -1 then ladder_direction = 5 end
		if sine == 1 then ladder_direction = 4 end
		local is_air  = minetest.get_node_or_nil(pos)
		while is_air ~= nil
		and is_air.name ~= "air" do
			minetest.add_node(pos, {name = "default:ladder", param2 = ladder_direction})
			pos.y = pos.y + 1
			is_air  = minetest.get_node_or_nil(pos)
		end
-- place a chest as treasure
		pos.x = cosine * (treasure_x + 2) - sine * (treasure_y - math.floor(maze_size_y / 2)) + player_pos.x
		pos.z = sine * (treasure_x + 2) + cosine * (treasure_y - math.floor(maze_size_y / 2)) + player_pos.z
		pos.y = math.floor(player_pos.y + 0.5) - 3 * treasure_l
		local items = 0
		for name, item in pairs(minetest.registered_items) do 
			local nBegin, nEnd = string.find(name, "default:")
			if nBegin ~= nil then 
				items = items + 1 
			end
		end
		minetest.add_node(pos, {name = "default:chest", inv = invcontent})
		local meta = minetest.get_meta(pos)
		local inv = meta:get_inventory()
		for name, item in pairs(minetest.registered_items) do
			local nBegin, nEnd = string.find(name, "default:")
			if nBegin ~= nil then 
				if math.random(items / 5) == 1 then 
					inv:add_item('main', name .. " 1")
				end
			end
		end
-- place a closer-stone to seal the entrance and exit
		pos.x = cosine * (start_x + 2) - sine * (start_y - math.floor(maze_size_y / 2)) + player_pos.x
		pos.z = sine * (start_x + 2) + cosine * (start_y - math.floor(maze_size_y / 2)) + player_pos.z
		pos.y = math.floor(player_pos.y + 0.5) - 3 * start_l - 1
		minetest.add_node(pos, {type = "node", name = "maze:closer"})
		pos.x = cosine * (maze_size_x + 1) - sine * (exit_y - math.floor(maze_size_y / 2)) + player_pos.x
		pos.z = sine * (maze_size_x + 1) + cosine * (exit_y - math.floor(maze_size_y / 2)) + player_pos.z
		pos.y = math.floor(player_pos.y + 0.5) - 3 * exit_l - 1
		minetest.add_node(pos, {type = "node", name = "maze:closer"})
		print(string.format("[maze] done after ca. %.2fs", os.clock() - t1))
	end,
})

local maze_closer = {} -- list of all closer stones

-- closer stone definition
minetest.register_node("maze:closer", {
	tile_images = {"default_cobble.png"},
	inventory_image = minetest.inventorycube("default_cobble.png"),
	drop = '',
	material = { diggability = "not"},
	description = "Closestone",
})

-- detect player walk over closer stone (abm isn't fast enough)
minetest.register_globalstep(function(dtime)
	local players  = minetest.get_connected_players()
	for _,pos in pairs(maze_closer) do
		for _,player in pairs(players) do
			local player_pos = player:getpos()
			local dist = math.sqrt( (pos.x - player_pos.x)^2 + (pos.y - (player_pos.y - 0.5))^2 + (pos.z - player_pos.z)^2 )
			if dist<3 then -- 2.2 would be enough, just make sure
				local meta = minetest.get_meta(pos)
				if dist<0.5 then
					meta:set_string("trap", "triggered")
				elseif dist > 1 then -- 0.71 would be enough, at least one node away
					if meta:get_string("trap") == "triggered" then
						meta:set_string("trap", "")
						for i = 0,2 do
							minetest.add_node({x = pos.x, y = pos.y+i, z = pos.z},{name="default:cobble"})
						end
					end
				end
			end
		end
	end
end)

-- create list of all closer stones (walk over detection now in globalstep, because abm isn't called often enough
minetest.register_abm(
	{nodenames = {"maze:closer"},
	interval = 1,
	chance = 1,
	action = function(pos)
		for _,closer_pos in pairs(maze_closer) do
			if closer_pos.x == pos.x
			and closer_pos.y == pos.y
			and closer_pos.z == pos.z then
				return
			end
		end
		table.insert(maze_closer, pos)
	end,
})