blockgame/mods/bg_tree/decompose.lua

local modname = minetest.get_current_modname()
local api = blockgame.tree
local vec = blockgame.vector

-- NODE NAMES

local leaves = modname .. ":leaves"
local leaves_decomposing = modname .. ":leaves_decomposing"

-- END OF NODE NAMES

blockgame.register_increasing_abm({
	id = modname .. ":begin_decompose",
	label = "decompose leaves",
	nodenames = {leaves},
	neighbors = {"group:dirty"},
	interval = 15,
	chance = 4,
	rate = function (pos, node, data)
		return data.value + math.random(4, 6)
	end,
	check = function (pos, node, data)
		return data.value >= 20
	end,
	action = function (pos, node, data)
		minetest.set_node(pos, {name = leaves_decomposing})
	end,
})

blockgame.register_increasing_abm({
	id = modname .. ":decompose",
	label = "decompose leaves",
	nodenames = {leaves_decomposing},
	neighbors = {"group:dirty"},
	interval = 20,
	chance = 8,
	rate = function (pos, node, data)
		-- TODO: decompose faster depending on surrounding dirty nodes & other decomposing leaves.
		-- can probably do that with a flood fill that counts up a "score" depending on the nodes it encounters.
		return data.value + math.random(1, 9)
	end,
	check = function (pos, node, data)
		return data.value >= 25
	end,
	action = function (pos, node, data)
		minetest.set_node(pos, {name = "bg_terrain:dirt"})
	end,
})