Make mushrooms spread over time

mods/ITEMS/mcl_mushrooms/small.lua

@@ -114,4 +114,66 @@ minetest.register_craft({
 	recipe = {'mcl_core:bowl', 'mcl_mushrooms:mushroom_brown', 'mcl_mushrooms:mushroom_red'}
 })
 
+--[[ Mushroom spread and death
+Code based on information gathered from Minecraft Wiki
+<http://minecraft.gamepedia.com/Tutorials/Mushroom_farming#Videos>
+]]
+minetest.register_abm({
+	label = "Mushroom spread",
+	nodenames = {"mcl_mushrooms:mushroom_brown", "mcl_mushrooms:mushroom_red"},
+	interval = 11,
+	chance = 50,
+	action = function(pos, node)
+		if minetest.get_node_light(pos, nil) > 12 then
+			minetest.remove_node(pos)
+			return
+		end
 
+		local pos0 = vector.add(pos, {x=-4, y=-1, z=-4})
+		local pos1 = vector.add(pos, {x=4, y=1, z=4})
+
+		-- Stop mushroom spread if a 9×3×9 box is too crowded
+		if #minetest.find_nodes_in_area(pos0, pos1, node.name) >= 5 then
+			return
+		end
+
+		local selected_pos = table.copy(pos)
+
+		-- Do two random selections which may place the new mushroom in a 5×5×5 cube
+		local random = {
+			x = selected_pos.x + math.random(-1, 1),
+			y = selected_pos.y + math.random(0, 1) - math.random(0, 1),
+			z = selected_pos.z + math.random(-1, 1)
+		}
+		local random_node = minetest.get_node_or_nil(random)
+		if not random_node or random_node.name ~= "air" then
+			return
+		end
+		local node_under = minetest.get_node_or_nil({x = random.x, y = random.y - 1, z = random.z})
+		if not node_under then
+			return
+		end
+
+		if minetest.get_node_light(random, 0.5) > 12 or (minetest.get_item_group(node_under.name, "opaque") == 0) then
+			return
+		end
+		local random2 = {
+			x = random.x + math.random(-1, 1),
+			y = random.y,
+			z = random.z + math.random(-1, 1)
+		}
+		random_node = minetest.get_node_or_nil(random2)
+		if not random_node or random_node.name ~= "air" then
+			return
+		end
+		node_under = minetest.get_node_or_nil({x = random2.x, y = random2.y - 1, z = random2.z})
+		if not node_under then
+			return
+		end
+		if minetest.get_node_light(random2, 0.5) > 12 or (minetest.get_item_group(node_under.name, "opaque") == 0) then
+			return
+		end
+
+		minetest.set_node(random2, {name = node.name})
+	end
+})