Restore Zero Length frozen Age time

src/main/java/net/dnorberg/rivencraft/Rivencraft.java

@@ -13,6 +13,7 @@ import net.dnorberg.rivencraft.config.RivencraftConfig;
 import net.dnorberg.rivencraft.config.RivencraftClientConfig;
 import net.dnorberg.rivencraft.book.AgeDimensionService;
 import net.dnorberg.rivencraft.book.AgeWeatherService;
+import net.dnorberg.rivencraft.book.AgeCelestialService;
 import net.neoforged.bus.api.IEventBus;
 import net.neoforged.fml.ModContainer;
 import net.neoforged.fml.common.Mod;
@@ -38,6 +39,7 @@ public final class Rivencraft {
         ModCreativeTabs.register(modEventBus);
         NeoForge.EVENT_BUS.addListener(BookStandConversionHandler::onRightClickBlock);
         NeoForge.EVENT_BUS.addListener(AgeWeatherService::onLevelTickPost);
+        NeoForge.EVENT_BUS.addListener(AgeCelestialService::onLevelTickPost);
         LOGGER.info("Initializing Rivencraft");
     }
 }

src/main/java/net/dnorberg/rivencraft/book/AgeCelestialService.java

@@ -0,0 +1,31 @@
+package net.dnorberg.rivencraft.book;
+
+import java.util.Map;
+import java.util.WeakHashMap;
+import net.minecraft.server.level.ServerLevel;
+import net.neoforged.neoforge.event.tick.LevelTickEvent;
+
+/** Holds Zero Length Age clocks without changing the server-wide daylight gamerule. */
+public final class AgeCelestialService {
+    private static final Map<ServerLevel, Long> FROZEN_TIMES = new WeakHashMap<>();
+
+    private AgeCelestialService() {
+    }
+
+    public static void freezeAt(ServerLevel level, long dayTime) {
+        FROZEN_TIMES.put(level, dayTime);
+    }
+
+    public static void unfreeze(ServerLevel level) {
+        FROZEN_TIMES.remove(level);
+    }
+
+    public static void onLevelTickPost(LevelTickEvent.Post event) {
+        if (event.getLevel() instanceof ServerLevel level) {
+            Long frozenTime = FROZEN_TIMES.get(level);
+            if (frozenTime != null && level.getDayTime() != frozenTime) {
+                level.setDayTime(frozenTime);
+            }
+        }
+    }
+}

src/main/java/net/dnorberg/rivencraft/book/AgeDefinition.java

@@ -21,7 +21,7 @@ public record AgeDefinition(
     public static final ResourceLocation RANDOM_VANILLA_PROFILE = ResourceLocation.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "random_vanilla"
     );
-    public static final int CURRENT_GENERATION_VERSION = 6;
+    public static final int CURRENT_GENERATION_VERSION = 7;
 
     public AgeDefinition {
         Objects.requireNonNull(id, "id");

src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java

@@ -103,12 +103,21 @@ public final class AgeDimensionService {
     }
 
     private static void applyCelestialClock(ServerLevel level, AgeDefinition age) {
-        level.setDayTimePerTick((float)(1.0D / age.traits().celestialPeriod()));
+        if (age.traits().hasStoppedCelestialCycle()) {
+            level.setDayTimePerTick(-1.0F);
+            AgeCelestialService.freezeAt(level, level.getDayTime());
+        } else {
+            AgeCelestialService.unfreeze(level);
+            level.setDayTimePerTick((float)(1.0D / age.traits().celestialPeriod()));
+        }
     }
 
     private static void applyInitialCelestialPhase(ServerLevel level, AgeDefinition age) {
         long phaseTime = (long)(age.traits().celestialPhase() * Level.TICKS_PER_DAY);
         level.setDayTime(phaseTime);
+        if (age.traits().hasStoppedCelestialCycle()) {
+            AgeCelestialService.freezeAt(level, phaseTime);
+        }
     }
 
     private static void synchronizeImmersivePortals(MinecraftServer server) {

src/main/java/net/dnorberg/rivencraft/book/AgeTraits.java

@@ -13,6 +13,7 @@ public record AgeTraits(
 ) {
     public static final double MIN_CELESTIAL_PERIOD = 0.2D;
     public static final double MAX_CELESTIAL_PERIOD = 2.0D;
+    public static final double STOPPED_CELESTIAL_PERIOD = 0.0D;
     public static final float MIN_CELESTIAL_ANGLE = 0.0F;
     public static final float MAX_CELESTIAL_ANGLE = 360.0F;
     public static final float MIN_CELESTIAL_PHASE = 0.0F;
@@ -27,7 +28,8 @@ public record AgeTraits(
         if (biomeDistribution == null || lighting == null || weather == null) {
             throw new IllegalArgumentException("Age trait choices cannot be null");
         }
-        if (celestialPeriod < MIN_CELESTIAL_PERIOD || celestialPeriod > MAX_CELESTIAL_PERIOD) {
+        if (celestialPeriod != STOPPED_CELESTIAL_PERIOD
+                && (celestialPeriod < MIN_CELESTIAL_PERIOD || celestialPeriod > MAX_CELESTIAL_PERIOD)) {
             throw new IllegalArgumentException("Celestial period is outside the legacy range");
         }
         if (celestialAngle < MIN_CELESTIAL_ANGLE || celestialAngle >= MAX_CELESTIAL_ANGLE) {
@@ -40,17 +42,27 @@ public record AgeTraits(
 
     public static AgeTraits select(long seed) {
         Random random = new Random(seed ^ 0x524956454E435241L);
+        BiomeDistribution biomeDistribution = randomChoice(random, BiomeDistribution.values());
+        Lighting lighting = randomChoice(random, Lighting.values());
+        Weather weather = randomChoice(random, Weather.values());
+        // Legacy's PERIOD_BASIC grammar gives ModZero rank 2 and its other
+        // three length modifiers rank 1, producing an effective 1-in-7 weight.
+        boolean stopped = random.nextInt(7) == 0;
         return new AgeTraits(
-                randomChoice(random, BiomeDistribution.values()),
-                randomChoice(random, Lighting.values()),
-                randomChoice(random, Weather.values()),
-                MIN_CELESTIAL_PERIOD
+                biomeDistribution,
+                lighting,
+                weather,
+                stopped ? STOPPED_CELESTIAL_PERIOD : MIN_CELESTIAL_PERIOD
                         + random.nextDouble() * (MAX_CELESTIAL_PERIOD - MIN_CELESTIAL_PERIOD),
                 random.nextFloat() * MAX_CELESTIAL_ANGLE,
                 random.nextFloat()
         );
     }
 
+    public boolean hasStoppedCelestialCycle() {
+        return celestialPeriod == STOPPED_CELESTIAL_PERIOD;
+    }
+
     public static <E extends Enum<E>> E parseOrDefault(String value, E fallback) {
         try {
             @SuppressWarnings("unchecked")

src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java

@@ -121,7 +121,8 @@ public final class LinkingGameTests {
                 "New Ages must record the current generation algorithm version");
         helper.assertValueEqual(first.traits(), AgeTraits.select(first.seed()),
                 "A page-free book must persist the deterministic traits selected from its seed");
-        helper.assertTrue(first.traits().celestialPeriod() >= AgeTraits.MIN_CELESTIAL_PERIOD
+        helper.assertTrue(first.traits().hasStoppedCelestialCycle()
+                        || first.traits().celestialPeriod() >= AgeTraits.MIN_CELESTIAL_PERIOD
                         && first.traits().celestialPeriod() <= AgeTraits.MAX_CELESTIAL_PERIOD,
                 "The celestial period must remain inside Mystcraft Legacy's random range");
         helper.assertTrue(first.seed() != another.seed(), "Distinct Age UUIDs must receive distinct random seeds");
@@ -186,9 +187,14 @@ public final class LinkingGameTests {
                     ? 0.25F : 0.0F;
             helper.assertTrue(Math.abs(level.dimensionType().ambientLight() - expectedAmbientLight) < 0.0001F,
                     "The runtime dimension must apply the persisted lighting trait");
-            float expectedDaySpeed = (float)(1.0D / definition.traits().celestialPeriod());
-            helper.assertTrue(Math.abs(level.getDayTimePerTick() - expectedDaySpeed) < 0.0001F,
-                    "The runtime dimension must apply the persisted celestial period");
+            if (definition.traits().hasStoppedCelestialCycle()) {
+                helper.assertTrue(level.getDayTimePerTick() < 0.0F,
+                        "A Zero Length Age must leave vanilla clock advancement under the freeze controller");
+            } else {
+                float expectedDaySpeed = (float)(1.0D / definition.traits().celestialPeriod());
+                helper.assertTrue(Math.abs(level.getDayTimePerTick() - expectedDaySpeed) < 0.0001F,
+                        "The runtime dimension must apply the persisted celestial period");
+            }
         }
         helper.succeed();
     }