Refactor code of snowed nodes

mods/ITEMS/mcl_core/functions.lua

@@ -1107,3 +1107,77 @@ minetest.register_abm({
 	end
 })
 
+---- Functions for snowed dirt-like blocks. ----
+
+-- Lookup tables
+mcl_core.snowed_nodes = {}
+mcl_core.snowed_nodes_reverse = {}
+
+-- Registers a snowed variant of a dirtlike node (e.g. grass block, podzol, mycelium).
+-- * itemstring_snowed: Itemstring of the snowed node to add
+-- * itemstring_clear: Itemstring of the original “clear” node without snow
+-- * tiles: Optional custom tiles
+mcl_core.register_snowed_node = function(itemstring_snowed, itemstring_clear, tiles)
+	local def = table.copy(minetest.registered_nodes[itemstring_clear])
+	-- Just some group clearing
+	def.description = nil
+	def._doc_items_longdesc = nil
+	def._doc_items_usagehelp = nil
+	def._doc_items_create_entry = false
+	def.groups.not_in_creative_inventory = 1
+
+	-- Enderman must never take this because this block is supposed to be always buried below snow.
+	def.groups.enderman_takable = nil
+
+	if not tiles then
+		def.tiles = {"default_snow.png", "default_dirt.png", "mcl_core_grass_side_snowed.png"}
+	end
+
+	-- Register stuff
+	minetest.register_node(itemstring_snowed, def)
+
+	mcl_core.snowed_nodes[itemstring_snowed] = itemstring_clear
+	mcl_core.snowed_nodes_reverse[itemstring_clear] = itemstring_snowed
+
+	if minetest.get_modpath("doc") then
+		doc.add_entry_alias("nodes", itemstring_clear, "nodes", itemstring_snowed)
+	end
+end
+
+-- Reverts a snowed dirtlike node at pos to its original snow-less form.
+-- This function assumes there is no snow cover node above. This function
+-- MUST NOT be called if there is a snow cover node above pos.
+mcl_core.clear_snow_dirt = function(pos, node)
+	if mcl_core.snowed_nodes[node.name] then
+		minetest.swap_node(pos, {name=mcl_core.snowed_nodes[node.name]})
+	end
+end
+
+
+-- Functions for snow cover nodes. A snow cover node is a node which turns a snowed dirtlike
+-- node into its snowed form while it is placed above.
+-- MCL2's snow cover nodes are Top Snow (mcl_core:snow) and Snow (mcl_core:snowblock).
+
+-- Always add the following functions to snow cover nodes:
+
+-- on_construct
+mcl_core.on_snow_construct = function(pos)
+	local npos = {x=pos.x, y=pos.y-1, z=pos.z}
+	local node = minetest.get_node(npos)
+	if mcl_core.snowed_nodes_reverse[node.name] then
+		minetest.swap_node(npos, {name=mcl_core.snowed_nodes_reverse[node.name]})
+	end
+end
+-- after_destruct
+-- Clears snowed dirtlike node below.
+mcl_core.after_snow_destruct = function(pos)
+	local nn = minetest.get_node(pos).name
+	-- No-op if snow was replaced with snow
+	if minetest.get_item_group(nn, "snow_cover") == 1 then
+		return
+	end
+	local npos = {x=pos.x, y=pos.y-1, z=pos.z}
+	local node = minetest.get_node(npos)
+	mcl_core.clear_snow_dirt(npos, node)
+end
+