Add API to weather mod

Co-authored-by: Till Affeldt <t.affeldt@tu-braunschweig.de>

mods/weather/api.lua

@@ -0,0 +1,32 @@
+local CYCLE = 8 -- Time period of cyclic clouds update in seconds
+
+weather = {}
+
+-- default implementation is empty
+function weather.get(player)
+	return {}
+end
+
+local function do_update()
+	for _, player in ipairs(minetest.get_connected_players()) do
+		local params = weather.get(player)
+		assert(params ~= nil, "weather.get() must not return nil")
+		if params.clouds then
+			player:set_clouds(params.clouds)
+		end
+		if params.lighting then
+			player:set_lighting(params.lighting)
+		end
+	end
+end
+
+local function cyclic_update()
+	do_update()
+	minetest.after(CYCLE, cyclic_update)
+end
+minetest.after(0, cyclic_update)
+
+-- Update on player join to instantly alter clouds from the default
+minetest.register_on_joinplayer(function(player)
+	do_update()
+end)