New general artificial water API

Now nodes other than sponges (i.e. downstream
mods) can create artificial temporary water sources
similar to sponge squeezing.

The API allows specifying a source node and position,
so the water will dissipate if the source node is
removed.  A min/max TTL can also be specified, so
like the sponge, it can require external triggering to
maintain the water flow as well as the presence of
the node.

mods/nc_sponge/squeeze.lua

@@ -16,19 +16,6 @@ local watersrc = "nc_terrain:water_gray_source"
 local waterflow = "nc_terrain:water_gray_flowing"
 local spongewet = modname .. ":sponge_wet"
 
-local spongecache = {}
-
-local function mkwater(pos, srcpos, new)
-	if new then nodecore.set_loud(pos, {name = watersrc}) end
-	local meta = minetest.get_meta(pos)
-	local data = {
-		srcpos = srcpos,
-		expire = nodecore.gametime + 10
-	}
-	meta:set_string(modname, minetest.serialize(data))
-	spongecache[minetest.hash_node_position(pos)] = data
-end
-
 nodecore.register_craft({
 		label = "squeeze sponge",
 		action = "pummel",
@@ -44,36 +31,17 @@ nodecore.register_craft({
 			for _, d in pairs(spongedirs) do
 				local p = vector.add(pos, d)
 				local nn = minetest.get_node(p).name
-				if nn == "air" or nn == watersrc
-				or nn == waterflow then
-					mkwater(p, pos, nn ~= watersrc)
+				local def = minetest.registered_nodes[nn] or {}
+				if nn == watersrc or nn == waterflow or def.air_equivalent then
+					nodecore.artificial_water(p, {
+							matchpos = pos,
+							match = spongewet,
+							minttl = 1,
+							maxttl = 10
+						})
 					found = true
 				end
 			end
 			if found then nodecore.node_sound(pos, "dig") end
 		end
 	})
-
-local function rmwater(pos)
-	nodecore.node_sound(pos, "dig")
-	return minetest.set_node(pos, {name = waterflow, param2 = 7})
-end
-
-nodecore.register_limited_abm({
-		label = "sponge water check",
-		interval = 1,
-		chance = 1,
-		nodenames = {watersrc},
-		action = function(pos)
-			local data = spongecache[minetest.hash_node_position(pos)]
-			if not data then
-				data = minetest.get_meta(pos):get_string(modname)
-				data = data and data ~= "" and minetest.deserialize(data)
-			end
-			if not data then return rmwater(pos) end
-			local snode = minetest.get_node(data.srcpos)
-			if snode.name == "ignore" then return end
-			if snode.name ~= spongewet then return rmwater(pos) end
-			if nodecore.gametime > data.expire then return rmwater(pos) end
-		end
-	})

mods/nc_terrain/api.lua

@@ -1,12 +1,15 @@
 -- LUALOCALS < ---------------------------------------------------------
 local math, minetest, nodecore
     = math, minetest, nodecore
-local math_floor, math_pow
-    = math.floor, math.pow
+local math_floor, math_pow, math_random
+    = math.floor, math.pow, math.random
 -- LUALOCALS > ---------------------------------------------------------
 
 local modname = minetest.get_current_modname()
 
+------------------------------------------------------------------------
+-- Hard Stone Strata
+
 nodecore.hard_stone_strata = 7
 
 function nodecore.hard_stone_tile(n)
@@ -23,6 +26,9 @@ function nodecore.hard_stone_tile(n)
 	.. o .. ")"
 end
 
+------------------------------------------------------------------------
+-- Dirt Leaching
+
 function nodecore.register_dirt_leaching(fromnode, tonode, rate)
 	local function waterat(pos, dx, dy, dz)
 		pos = {x = pos.x + dx, y = pos.y + dy, z = pos.z + dz}
@@ -54,3 +60,77 @@ function nodecore.register_dirt_leaching(fromnode, tonode, rate)
 			end
 		})
 end
+
+------------------------------------------------------------------------
+-- Artificial Water
+
+local graywatersrc = "nc_terrain:water_gray_source"
+local graywaterflow = "nc_terrain:water_gray_flowing"
+local graywatercache = {}
+
+local function rmwater(pos)
+	nodecore.node_sound(pos, "dig")
+	return minetest.set_node(pos, {name = graywaterflow, param2 = 7})
+end
+function nodecore.artificial_water_check(pos)
+	local data = graywatercache[minetest.hash_node_position(pos)]
+	if not data then
+		data = minetest.get_meta(pos):get_string(modname)
+		data = data and data ~= "" and minetest.deserialize(data)
+	end
+	if not data then return rmwater(pos) end
+
+	if data.recheck and nodecore.gametime < data.recheck then
+		return nodecore.dnt_set(pos, graywatersrc, data.recheck - nodecore.gametime)
+	end
+	if data.expire and nodecore.gametime >= data.expire then
+		return rmwater(pos)
+	end
+
+	if data.matchpos and data.match then
+		local mnode = minetest.get_node(data.matchpos)
+		if mnode.name ~= "ignore" and not nodecore.match(mnode, data.match) then
+			return rmwater(pos)
+		end
+	end
+
+	return nodecore.dnt_set(pos, graywatersrc, 1 + math_random())
+end
+
+nodecore.register_dnt({
+		name = graywatersrc,
+		nodenames = {graywatersrc},
+		action = function(pos) return nodecore.artificial_water_check(pos) end
+	})
+
+nodecore.register_limited_abm({
+		label = "artificial water check",
+		interval = 1,
+		chance = 1,
+		nodenames = {graywatersrc},
+		action = function(pos) return nodecore.artificial_water_check(pos) end
+	})
+
+--[[
+artificial water def:
+- matchpos = position of node that's producing the water
+- match = match criteria to check that water-producing node is still present
+- minttl = minimum amount of time water must be there before rechecking for valid source
+- maxttl = maximum amount of time water will remain without being updated
+--]]
+function nodecore.artificial_water(pos, def)
+	local nn = minetest.get_node(pos).name
+	if nn ~= graywatersrc and nn ~= graywaterflow then
+		nodecore.set_loud(pos, {name = graywatersrc})
+	end
+	local meta = minetest.get_meta(pos)
+	local data = {
+		match = def.match,
+		matchpos = def.matchpos,
+		recheck = def.minttl and nodecore.gametime + def.minttl,
+		expire = def.maxttl and nodecore.gametime + def.maxttl
+	}
+	meta:set_string(modname, minetest.serialize(data))
+	graywatercache[minetest.hash_node_position(pos)] = data
+	return nodecore.dnt_set(pos, graywatersrc, def.minttl or 1)
+end