blockgame/mods/bg_tree/decompose.lua

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

-- NODE NAMES

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



local decompose_time_speed = 1
-- TODO: add setting for this as well.
minetest.register_chatcommand(modname .. ":set_decompose_time_speed", {
	params = "<value>",
	description = "set the speed at which decomposition happens.",
	privs = {
		control_time = true,
	},
	func = function (player_name, speed)
		speed = tonumber(speed)
		if speed == nil then
			minetest.chat_send_player(player_name, "time speed must be a number.")
			return
		end
		if speed < 0 or speed > 256 then
			minetest.chat_send_player(player_name, "time speed must be between 0 and 256 (inclusive).")
			return
		end

		decompose_time_speed = speed
		minetest.chat_send_all(player_name .. " set the leaves decomposition time speed to " .. speed .. ".")
	end,
})



local decompose_scores = {
	dirty = 100,
	leaves_decomposing = 20,
}

local start_decompose_cost = 4000

blockgame.register_increasing_abm({
	id = modname .. ":begin_decompose",
	label = "decompose leaves",
	nodenames = {leaves},
	neighbors = {"group:dirty", leaves_decomposing},
	interval = 15,
	chance = 8,
	rate = function (pos, node, data)
		local score = blockgame.score_nearby_nodes(pos, 2, decompose_scores, function (gain, distance)
			return math.floor(gain / (distance ^ 3))
		end)

		return data.value + score * decompose_time_speed
	end,
	check = function (pos, node, data)
		return data.value >= start_decompose_cost
	end,
	action = function (pos, node, data)
		-- NOTE: might wanna access the 4 from somewhere, instead of directly knowing it.
		-- that way this won't have to change if decomposing leaves max levels change.
		local level = math.random(1, 4)
		minetest.set_node(pos, {name = leaves_decomposing .. "_" .. level})
	end,
})

local decompose_cost = 30000
local average_leaves_per_dirt = 4

blockgame.register_increasing_abm({
	id = modname .. ":decompose",
	label = "decompose leaves",
	nodenames = {"group:leaves_decomposing"},
	neighbors = {"group:dirty"},
	interval = 15,
	chance = 10,
	rate = function (pos, node, data)
		local score = 20

		local bonus = blockgame.score_nearby_nodes(pos, 4, decompose_scores, function (gain, distance)
			return math.floor(gain / (distance ^ 3))
		end)

		score = score + bonus
		return data.value + score * decompose_time_speed
	end,
	check = function (pos, node, data)
		return data.value >= decompose_cost
	end,
	action = function (pos, node, data)
		-- currently, larger leaf piles have a greater chance of turning into dirt instead of disappearing.
		-- might wanna make it so that instead, dirt is layered as well?
		local def = minetest.registered_nodes[node.name]
		local dirt_chance = def.level_max - def.level + 1

		if blockgame.chance(dirt_chance * average_leaves_per_dirt) then
			minetest.set_node(pos, {name = "bg_terrain:dirt"})
		else
			minetest.remove_node(pos)
			minetest.check_for_falling(pos)
		end
	end,
})