-- Defines the border of a world
local world_border = tonumber(minetest.settings:get("world_border")) or 500

-- Stop sign entities
local north = nil
local south = nil
local west = nil
local east = nil

-- add_remove_border (stop sign)
-- Adds entity if within 10 blocks of the player position
function add_remove_border(entity, player_pos, entity_pos, is_rotated)
	if vector.distance(player_pos, entity_pos) < 10 then
		if not entity then
			entity = minetest.add_entity(entity_pos, "simpleworldborder:border", nil)
			if is_rotated then entity:set_rotation({x = 0, y = math.pi/2, z = 0 }) end
		else
			-- within range but entity already exists
		end
	else
		-- out of range
		if entity then
			-- remove entity
			entity:remove()
			return nil
		end
	end
	return entity
end

-- worldborder:border item
-- represents "stop sign" for border
minetest.register_entity("simpleworldborder:border", {
	initial_properties = {
        collide_with_objects = false,
		is_visible = true,
    	visual = "upright_sprite",
    	textures = {
			"simpleworldborder_stopsign.png",
			"simpleworldborder_stopsign.png"
		},
 		visual_size = {
			x = 10,
			y = 10
		},
		backface_culling = false,
		glow = -1,
		shaded = false,
		static_save = false,
		use_texture_alpha = true
	}
})

minetest.register_globalstep(function(dtime)
	local players = minetest.get_connected_players()
	for i, player in ipairs(players) do
		local has_player_moved = false
		local name = player:get_player_name()
		local pos = vector.round(player:getpos())

		-- Check if player is close world border. If so, spawn worldborder entity!
		local northpos = vector.new(pos.x, pos.y, world_border)
		local southpos = vector.new(pos.x, pos.y, -world_border)
		local eastpos = vector.new(world_border, pos.y, pos.z)
		local westpos = vector.new(-world_border, pos.y, pos.z)

		north = add_remove_border(north, pos, northpos, false)
		south = add_remove_border(south, pos, southpos, false)
		east = add_remove_border(east, pos, eastpos, true)
		west = add_remove_border(west, pos, westpos, true)

		-- calculate new position of player
		if pos.x > world_border then
			pos.x = world_border
			has_player_moved = true
		elseif pos.x < -world_border then
			pos.x = -world_border
			has_player_moved = true
		end

		if pos.z > world_border then
			pos.z = world_border
			has_player_moved = true
		elseif pos.z < -world_border then
			pos.z = -world_border
			has_player_moved = true
		end

		-- move player if needed
		if pos and has_player_moved then
			player:setpos(pos)
		end

		-- move stop sign entities
		if east then
			east:moveto({x = world_border + 1, y = pos.y, z = pos.z})
		end
		if west then
			west:moveto({x = -world_border - 1, y = pos.y, z = pos.z})
		end
		if north then
			north:moveto({x = pos.x, y = pos.y, z = world_border + 1})
		end
		if south then
			south:moveto({x = pos.x, y = pos.y, z = -world_border - 1})
		end
	end
end)