Add moon phases

mods/ENVIRONMENT/mcl_moon/API.md

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+# `mcl_moon` API
+This API has one function:
+
+## `mcl_moon.get_moon_phase()`
+
+Returns current moon phase (0-7).
+
+* 0 = Full Moon
+* 1 = Waning Gibbous
+* 2 = Last Quarter
+* 3 = Waning Crescent
+* 4 = New Moon
+* 5 = Waxing Crescent
+* 6 = First Quarter
+* 7 = Waxing Gibbous 

mods/ENVIRONMENT/mcl_moon/init.lua

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+local MOON_PHASES = 8
+local MOON_PHASES_HALF = MOON_PHASES / 2
+local SHEET_W = 4
+local SHEET_H = 2
+
+mcl_moon = {}
+mcl_moon.MOON_PHASES = MOON_PHASES
+
+mcl_moon.get_moon_phase = function()
+	local after_midday = 0
+	local tod = minetest.get_timeofday()
+	if tod > 0.5 then
+		after_midday = 1
+	end
+	return (minetest.get_day_count() + after_midday) % MOON_PHASES
+end
+
+local get_moon_texture = function()
+	local phase = mcl_moon.get_moon_phase()
+	local x = phase % MOON_PHASES_HALF
+	local y
+	if phase >= MOON_PHASES_HALF then
+		y = 1
+	else
+		y = 0
+	end
+	return "mcl_moon_moon_phases.png^[sheet:"..SHEET_W.."x"..SHEET_H..":"..x..","..y
+end
+
+local timer = 0
+local last_reported_phase = nil
+minetest.register_globalstep(function(dtime)
+	timer = timer + dtime
+	if timer < 5 then
+		return
+	end
+	timer = 0
+	local phase = mcl_moon.get_moon_phase()
+	-- No-op when moon phase didn't change yet
+	if last_reported_phase == phase then
+		return
+	end
+	minetest.log("info", "[mcl_moon] New moon phase: "..phase)
+	last_reported_phase = phase
+	local moon_arg = {texture = get_moon_texture()}
+	local players = minetest.get_connected_players()
+	for p=1, #players do
+		players[p]:set_moon(moon_arg)
+	end
+end)
+
+minetest.register_on_joinplayer(function(player)
+	player:set_moon({texture = get_moon_texture(), scale=3.75})
+end)

mods/ENVIRONMENT/mcl_moon/mod.conf

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+name = mcl_moon
+description = Adds moon phases to the game