Change particle handles and linking to be a little more robust. Should help with some cases where duplicate particles happen

src/main/java/com/minelittlepony/unicopia/ability/magic/SpellContainer.java

@@ -1,6 +1,7 @@
 package com.minelittlepony.unicopia.ability.magic;
 
 import java.util.Optional;
+import java.util.UUID;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
@@ -30,8 +31,18 @@ public interface SpellContainer {
         public boolean forEach(Function<Spell, Operation> action, boolean update) {
             return false;
         }
+
+        @Override
+        public boolean contains(UUID id) {
+            return false;
+        }
     };
 
+    /**
+     * Checks if a spell with the given uuid is present.
+     */
+    boolean contains(UUID id);
+
     /**
      * Gets the active effect for this caster updating it if needed.
      */
@@ -79,6 +90,11 @@ public interface SpellContainer {
 
         SpellContainer delegate();
 
+        @Override
+        default boolean contains(UUID id) {
+            return delegate().contains(id);
+        }
+
         @Override
         default <T extends Spell> Optional<T> get(@Nullable SpellPredicate<T> type, boolean update) {
             return delegate().get(type, update);

src/main/java/com/minelittlepony/unicopia/ability/magic/spell/JoustingSpell.java

@@ -54,10 +54,10 @@ public class JoustingSpell extends AbstractSpell {
         }
 
         if (source.isClient()) {
-            particlEffect.ifAbsent(source, spawner -> {
+            particlEffect.ifAbsent(getUuid(), source, spawner -> {
                 spawner.addParticle(UParticles.RAINBOOM_TRAIL, source.getOriginVector(), Vec3d.ZERO);
                 spawner.addParticle(new OrientedBillboardParticleEffect(UParticles.RAINBOOM_RING, source.getPhysics().getMotionAngle()), source.getOriginVector(), Vec3d.ZERO);
-            }).ifPresent(p -> p.attach(source));
+            });
         }
 
         LivingEntity owner = source.getMaster();

src/main/java/com/minelittlepony/unicopia/ability/magic/spell/PlaceableSpell.java

@@ -82,10 +82,9 @@ public class PlaceableSpell extends AbstractDelegatingSpell {
 
             return super.tick(source, Situation.GROUND);
         } else if (situation == Situation.GROUND_ENTITY) {
-            particlEffect.ifAbsent(source, spawner -> {
+            particlEffect.ifAbsent(getUuid(), source, spawner -> {
                 spawner.addParticle(new OrientedBillboardParticleEffect(UParticles.MAGIC_RUNES, 90, 0), source.getOriginVector(), Vec3d.ZERO);
             }).ifPresent(p -> {
-                p.attach(source);
                 p.setAttribute(1, spell.getType().getColor());
             });
         }

src/main/java/com/minelittlepony/unicopia/ability/magic/spell/effect/DarkVortexSpell.java

@@ -55,10 +55,9 @@ public class DarkVortexSpell extends AttractiveSpell {
 
         float radius = (float)getDrawDropOffRange(source) / 2;
 
-        particlEffect.ifAbsent(source, spawner -> {
+        particlEffect.ifAbsent(getUuid(), source, spawner -> {
             spawner.addParticle(new SphereParticleEffect(getType().getColor(), 0.99F, radius), source.getOriginVector(), Vec3d.ZERO);
         }).ifPresent(p -> {
-            p.attach(source);
             p.setAttribute(0, radius);
         });
     }

src/main/java/com/minelittlepony/unicopia/ability/magic/spell/effect/ShieldSpell.java

@@ -70,10 +70,9 @@ public class ShieldSpell extends AbstractSpell {
             source.addParticle(new MagicParticleEffect(getType().getColor()), pos, Vec3d.ZERO);
         });
 
-        particlEffect.ifAbsent(source, spawner -> {
+        particlEffect.ifAbsent(getUuid(), source, spawner -> {
             spawner.addParticle(new SphereParticleEffect(getType().getColor(), 0.3F, radius), source.getOriginVector(), Vec3d.ZERO);
         }).ifPresent(p -> {
-            p.attach(source);
             p.setAttribute(0, radius);
             p.setAttribute(1, getType().getColor());
         });

src/main/java/com/minelittlepony/unicopia/client/particle/RainbowTrailParticle.java

@@ -2,6 +2,7 @@ package com.minelittlepony.unicopia.client.particle;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 import com.minelittlepony.unicopia.ability.magic.Caster;
 import com.minelittlepony.unicopia.entity.player.Pony;
@@ -22,7 +23,7 @@ public class RainbowTrailParticle extends AbstractBillboardParticle implements A
 
     private final List<Segment> segments = new ArrayList<>();
 
-    private final Link link = new Link();
+    private Optional<Link> link = Optional.empty();
 
     public RainbowTrailParticle(DefaultParticleType effect, ClientWorld world, double x, double y, double z, double velocityX, double velocityY, double velocityZ) {
         super(world, x, y, z, velocityX, velocityY, velocityZ);
@@ -41,13 +42,13 @@ public class RainbowTrailParticle extends AbstractBillboardParticle implements A
     }
 
     @Override
-    public void attach(Caster<?> caster) {
+    public void attach(Link link) {
-        link.attach(caster);
+        this.link = Optional.of(link);
     }
 
     @Override
     public void detach() {
-        link.detach();
+        link = Optional.empty();
     }
 
     @Override
@@ -90,9 +91,9 @@ public class RainbowTrailParticle extends AbstractBillboardParticle implements A
     public void tick() {
         super.tick();
 
-        if (link.linked()) {
+        if (link.isPresent()) {
             age = 0;
-            link.ifAbsent(() -> {}).ifPresent(this::follow);
+            link.flatMap(Link::get).ifPresent(this::follow);
         } else if (!dead) {
             follow(Pony.of(MinecraftClient.getInstance().player));
         }

src/main/java/com/minelittlepony/unicopia/client/particle/RunesParticle.java

@@ -1,5 +1,7 @@
 package com.minelittlepony.unicopia.client.particle;
 
+import java.util.Optional;
+
 import com.minelittlepony.common.util.Color;
 import com.minelittlepony.unicopia.ability.magic.Caster;
 import com.minelittlepony.unicopia.particle.OrientedBillboardParticleEffect;
@@ -33,7 +35,7 @@ public class RunesParticle extends OrientedBillboardParticle implements Attachme
     private float prevRotationAngle;
     private float rotationAngle;
 
-    private final Link link = new Link();
+    private Optional<Link> link = Optional.empty();
 
     private int stasisAge = -1;
 
@@ -52,18 +54,18 @@ public class RunesParticle extends OrientedBillboardParticle implements Attachme
     }
 
     @Override
-    public void attach(Caster<?> caster) {
+    public void attach(Link link) {
-        link.attach(caster);
+        this.link = Optional.of(link);
         velocityX = 0;
         velocityY = 0;
         velocityZ = 0;
-        Vec3d pos = caster.getOriginVector();
+        Vec3d pos = link.get().map(Caster::getOriginVector).orElse(Vec3d.ZERO);
         setPos(pos.x, pos.y, pos.z);
     }
 
     @Override
     public void detach() {
-        link.detach();
+        link = Optional.empty();
     }
 
     @Override
@@ -135,16 +137,14 @@ public class RunesParticle extends OrientedBillboardParticle implements Attachme
     public void tick() {
         super.tick();
 
-        if (link.linked()) {
+        link.flatMap(Link::get).map(Caster::getEntity).ifPresentOrElse(e -> {
-            link.ifAbsent(this::detach).map(Caster::getEntity).ifPresent(e -> {
             if (getAlphaScale() >= 0.9F) {
                 if (stasisAge < 0) {
                     stasisAge = age;
                 }
                 age = stasisAge;
             }
-            });
+        }, this::detach);
-        }
 
         prevBaseSize = baseSize;
         if (baseSize < 3) {

src/main/java/com/minelittlepony/unicopia/client/particle/SphereParticle.java

@@ -17,6 +17,9 @@ import com.minelittlepony.unicopia.particle.ParticleHandle.Attachment;
 import com.minelittlepony.unicopia.particle.ParticleHandle.Link;
 import com.minelittlepony.unicopia.util.ColorHelper;
 import com.mojang.blaze3d.systems.RenderSystem;
+
+import java.util.Optional;
+
 import com.minelittlepony.common.util.Color;
 
 public class SphereParticle extends Particle implements Attachment {
@@ -28,7 +31,7 @@ public class SphereParticle extends Particle implements Attachment {
     protected float lerpIncrement;
     protected float toRadius;
 
-    private final Link link = new Link();
+    private Optional<Link> link = Optional.empty();
 
     private static final SphereModel MODEL = new SphereModel();
 
@@ -58,9 +61,9 @@ public class SphereParticle extends Particle implements Attachment {
     }
 
     @Override
-    public void attach(Caster<?> caster) {
+    public void attach(Link link) {
         setMaxAge(50000);
-        link.attach(caster);
+        this.link = Optional.of(link);
     }
 
     @Override
@@ -92,14 +95,14 @@ public class SphereParticle extends Particle implements Attachment {
     public void tick() {
         super.tick();
 
-        if (link.linked()) {
+        if (link.isPresent()) {
-            link.ifAbsent(this::markDead).map(Caster::getEntity).ifPresent(e -> {
+            link.flatMap(Link::get).map(Caster::getEntity).ifPresentOrElse(e -> {
                 setPos(e.getX(), e.getY() + 0.5, e.getZ());
 
                 prevPosX = e.lastRenderX;
                 prevPosY = e.lastRenderY + 0.5;
                 prevPosZ = e.lastRenderZ;
-            });
+            }, this::detach);
 
             if (steps-- > 0) {
                 radius += lerpIncrement;

src/main/java/com/minelittlepony/unicopia/network/datasync/EffectSync.java

@@ -1,6 +1,7 @@
 package com.minelittlepony.unicopia.network.datasync;
 
 import java.util.Optional;
+import java.util.UUID;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -39,6 +40,11 @@ public class EffectSync implements SpellContainer {
         this.param = param;
     }
 
+    @Override
+    public boolean contains(UUID id) {
+        return spells.containsReference(id);
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public <T extends Spell> Optional<T> get(@Nullable SpellPredicate<T> type, boolean update) {

src/main/java/com/minelittlepony/unicopia/network/datasync/NetworkedReferenceSet.java

@@ -34,6 +34,10 @@ public class NetworkedReferenceSet<T> {
         this.factory = factory;
     }
 
+    public boolean containsReference(UUID id) {
+        return ids.contains(id);
+    }
+
     public Stream<T> getReferences() {
         return ids.stream().map(id -> values.get(id))
                 .map(a -> a.getReference())

src/main/java/com/minelittlepony/unicopia/particle/ParticleHandle.java

@@ -1,17 +1,18 @@
 package com.minelittlepony.unicopia.particle;
 
+import java.lang.ref.WeakReference;
+import java.util.Map;
 import java.util.Optional;
 import java.util.UUID;
+import java.util.WeakHashMap;
 import java.util.function.Consumer;
 
 import com.minelittlepony.unicopia.ability.magic.Caster;
-import com.minelittlepony.unicopia.ability.magic.spell.Spell;
 
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 import net.minecraft.client.MinecraftClient;
 import net.minecraft.client.particle.Particle;
-import net.minecraft.entity.Entity;
 import net.minecraft.particle.ParticleEffect;
 import net.minecraft.util.math.Vec3d;
 
@@ -19,30 +20,41 @@ import net.minecraft.util.math.Vec3d;
  * A connection class for updating and persisting an attached particle effect.
  */
 public class ParticleHandle {
+    private Optional<WeakReference<Attachment>> particleEffect = Optional.empty();
 
-    private Optional<Attachment> particleEffect = Optional.empty();
+    public Optional<Attachment> ifAbsent(UUID id, ParticleSource source, Consumer<ParticleSpawner> constructor) {
-
+        return get().or(() -> {
-    public Optional<Attachment> ifAbsent(ParticleSource source, Consumer<ParticleSpawner> constructor) {
-        particleEffect.filter(Attachment::isStillAlive).orElseGet(() -> {
             if (source.getWorld().isClient) {
-                constructor.accept(this::addParticle);
+                constructor.accept((effect, pos, vel) -> new ClientHandle().addParticle(id, source, effect, pos, vel));
             }
-            return null;
+            return get();
         });
-
-        return particleEffect;
     }
 
     public void destroy() {
-        particleEffect.ifPresent(Attachment::detach);
+        get().ifPresent(Attachment::detach);
     }
 
+    private Optional<Attachment> get() {
+        return particleEffect.map(WeakReference::get).filter(Attachment::isStillAlive);
+    }
+
+    private final class ClientHandle {
+        private static final Map<UUID, Particle> SPAWNED_PARTICLES = new WeakHashMap<>();
+
         @Environment(EnvType.CLIENT)
-    private void addParticle(ParticleEffect effect, Vec3d pos, Vec3d vel) {
+        private void addParticle(UUID id, ParticleSource source, ParticleEffect effect, Vec3d pos, Vec3d vel) {
-        Particle p = MinecraftClient.getInstance().particleManager.addParticle(effect, pos.x, pos.y, pos.z, vel.x, vel.y, vel.z);
+            Particle p = SPAWNED_PARTICLES.computeIfAbsent(id, i -> {
+                Particle pp = MinecraftClient.getInstance().particleManager.addParticle(effect, pos.x, pos.y, pos.z, vel.x, vel.y, vel.z);
+                if (pp instanceof Attachment && source instanceof Caster<?>) {
+                    ((Attachment) pp).attach(new Link(id, (Caster<?>)source));
+                }
+                return pp;
+            });
 
             if (p instanceof Attachment) {
-            particleEffect = Optional.of((Attachment)p);
+                particleEffect = Optional.of(new WeakReference<>((Attachment)p));
+            }
         }
     }
 
@@ -50,7 +62,7 @@ public class ParticleHandle {
 
         boolean isStillAlive();
 
-        void attach(Caster<?> caster);
+        void attach(Link link);
 
         void detach();
 
@@ -58,41 +70,17 @@ public class ParticleHandle {
     }
 
     public static final class Link {
-
+        private Optional<WeakReference<Caster<?>>> caster = Optional.empty();
-        private Optional<Caster<?>> caster = Optional.empty();
         private UUID effect;
-        private boolean linked;
 
-        public void attach(Caster<?> caster) {
+        private Link(UUID effect, Caster<?> caster) {
-            this.linked = true;
+            this.caster = Optional.of(new WeakReference<>(caster));
-            this.caster = Optional.of(caster);
+            this.effect = effect;
-            this.effect = caster.getSpellSlot().get(false).map(Spell::getUuid).orElse(null);
         }
 
-        public void detach() {
+        public Optional<Caster<?>> get() {
-            caster = Optional.empty();
+            caster = caster.filter(r -> r.get() != null && r.get().getSpellSlot().contains(effect));
-        }
+            return caster.map(WeakReference::get);
-
-        public boolean linked() {
-            return linked;
-        }
-
-        public Optional<Caster<?>> ifAbsent(Runnable action) {
-            caster = caster.filter(c -> {
-                Entity e = c.getEntity();
-
-                return Caster.of(e).orElse(null) == c
-                        && c.getSpellSlot().get(false)
-                            .filter(s -> s.getUuid().equals(effect))
-                            .isPresent()
-                        && e != null
-                        && c.getWorld().getEntityById(e.getId()) != null;
-            });
-            if (!caster.isPresent()) {
-                action.run();
-            }
-
-            return caster;
         }
     }
 }