Move various gravitation/force/physics stuff to a utility class

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

@@ -17,6 +17,13 @@ public interface SpellPredicate<T extends Spell> extends Predicate<Spell> {
     SpellPredicate<AbstractDisguiseSpell> IS_DISGUISE = s -> s instanceof AbstractDisguiseSpell;
     SpellPredicate<ShieldSpell> IS_SHIELD_LIKE = spell -> spell instanceof ShieldSpell;
 
+    default SpellPredicate<T> and(SpellPredicate<T> predicate) {
+        SpellPredicate<T> self = this;
+        return s -> {
+            return self.test(s) && predicate.test(s);
+        };
+    }
+
     default boolean isOn(Caster<?> caster) {
         return caster.getSpellSlot().contains(this);
     }

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

@@ -0,0 +1,62 @@
+package com.minelittlepony.unicopia.ability.magic.spell.effect;
+
+import com.minelittlepony.unicopia.entity.player.Pony;
+import com.minelittlepony.unicopia.item.enchantment.UEnchantments;
+
+import net.minecraft.enchantment.EnchantmentHelper;
+import net.minecraft.entity.Entity;
+import net.minecraft.entity.LivingEntity;
+import net.minecraft.util.math.MathHelper;
+import net.minecraft.util.math.Vec3d;
+
+public interface AttractionUtils {
+
+    static double getAttractiveForce(double wellMass, Vec3d wellPosition, Entity target) {
+        return (wellMass * AttractionUtils.getMass(target)) / MathHelper.square(wellPosition.distanceTo(target.getPos()));
+    }
+
+    static double getMass(Entity entity) {
+        return entity.getWidth() * entity.getHeight();
+    }
+
+    /**
+     * Applies a force to the given entity relative to a given center position
+     */
+    static void applyForce(Vec3d center, Entity target, double force, double yChange, boolean clampVelocity) {
+        if (clampVelocity) {
+            target.setVelocity(target.getVelocity().multiply(Math.min(1, 1 - force)));
+        }
+        center = target.getPos().subtract(center).normalize().multiply(force);
+
+        if (target instanceof LivingEntity) {
+            center = center.multiply(1 / (1 + EnchantmentHelper.getEquipmentLevel(UEnchantments.HEAVY, (LivingEntity)target)));
+        }
+
+        target.addVelocity(
+                center.x,
+                center.y + yChange,
+                center.z
+        );
+    }
+
+    /**
+     * Returns a force to apply based on the given player's given race.
+     */
+    static double getForceAdjustment(Entity entity) {
+        return Pony.of(entity).map(pony -> {
+            double force = 0.75;
+
+            if (pony.getSpecies().canUseEarth()) {
+                force /= 2;
+
+                if (pony.getMaster().isSneaking()) {
+                    force /= 6;
+                }
+            } else if (pony.getSpecies().canFly()) {
+                force *= 2;
+            }
+
+            return force;
+        }).orElse(1D);
+    }
+}

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

@@ -4,7 +4,6 @@ import com.minelittlepony.unicopia.ability.magic.Caster;
 import com.minelittlepony.unicopia.ability.magic.spell.ProjectileSpell;
 import com.minelittlepony.unicopia.ability.magic.spell.trait.SpellTraits;
 import com.minelittlepony.unicopia.ability.magic.spell.trait.Trait;
-import com.minelittlepony.unicopia.entity.player.Pony;
 import com.minelittlepony.unicopia.particle.FollowingParticleEffect;
 import com.minelittlepony.unicopia.particle.MagicParticleEffect;
 import com.minelittlepony.unicopia.particle.UParticles;
@@ -13,7 +12,6 @@ import com.minelittlepony.unicopia.util.shape.Sphere;
 
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.ItemEntity;
-import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.util.math.MathHelper;
 import net.minecraft.util.math.Vec3d;
 
@@ -53,15 +51,15 @@ public class AttractiveSpell extends ShieldSpell implements ProjectileSpell {
 
         boolean isGood = isFriendlyTogether(source);
 
-        if (isGood && target instanceof PlayerEntity) {
+        if (isGood) {
-            force *= calculateAdjustedForce(Pony.of((PlayerEntity)target));
+            force *= AttractionUtils.getForceAdjustment(target);
         }
 
         if (!isGood && source.getWorld().random.nextInt(4500) == 0) {
             source.getEntity().damage(MagicalDamageSource.create("vortex"), 4);
         }
 
-        applyForce(getOrigin(source), target, -force, 0);
+        AttractionUtils.applyForce(getOrigin(source), target, -force, 0, false);
 
         float maxVel = !isFriendlyTogether(source) ? 1 : 1.6f;
 

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

@@ -189,7 +189,7 @@ public class DarkVortexSpell extends AttractiveSpell implements ProjectileSpell
     }
 
     private double getAttractiveForce(Caster<?> source, Entity target) {
-        return (getMass() * getMass(target)) / Math.pow(getOrigin(source).distanceTo(target.getPos()), 2);
+        return AttractionUtils.getAttractiveForce(getMass(), getOrigin(source), target);
     }
 
     private double getMass() {
@@ -197,10 +197,6 @@ public class DarkVortexSpell extends AttractiveSpell implements ProjectileSpell
         return 10 + Math.min(15, Math.min(0.5F + pulse, (float)Math.exp(age) / 8F - 90) + accumulatedMass / 10F) + pulse;
     }
 
-    private double getMass(Entity entity) {
-        return entity.getWidth() * entity.getHeight();
-    }
-
     @Override
     protected void applyRadialEffect(Caster<?> source, Entity target, double distance, double radius) {
 
@@ -227,20 +223,21 @@ public class DarkVortexSpell extends AttractiveSpell implements ProjectileSpell
                 return;
             }
 
-            accumulatedMass += getMass(target);
+            double massOfTarget = AttractionUtils.getMass(target);
+
+            accumulatedMass += massOfTarget;
             setDirty();
             target.damage(MagicalDamageSource.create("black_hole"), Integer.MAX_VALUE);
             if (!(target instanceof PlayerEntity)) {
                 target.discard();
             }
 
-            source.subtractEnergyCost(-getMass(target) * 10);
+            source.subtractEnergyCost(-massOfTarget * 10);
             source.getWorld().playSound(null, source.getOrigin(), USounds.AMBIENT_DARK_VORTEX_MOOD, SoundCategory.AMBIENT, 2, 0.02F);
         } else {
             double force = getAttractiveForce(source, target);
 
-            target.setVelocity(target.getVelocity().multiply(Math.min(1, 1 - force)));
+            AttractionUtils.applyForce(getOrigin(source), target, -force, 0, true);
-            applyForce(getOrigin(source), target, -force, 0);
 
             source.subtractEnergyCost(-2);
         }

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

@@ -7,8 +7,6 @@ import com.minelittlepony.unicopia.ability.magic.Caster;
 import com.minelittlepony.unicopia.ability.magic.spell.Situation;
 import com.minelittlepony.unicopia.ability.magic.spell.trait.SpellTraits;
 import com.minelittlepony.unicopia.ability.magic.spell.trait.Trait;
-import com.minelittlepony.unicopia.entity.player.Pony;
-import com.minelittlepony.unicopia.item.enchantment.UEnchantments;
 import com.minelittlepony.unicopia.particle.MagicParticleEffect;
 import com.minelittlepony.unicopia.particle.ParticleHandle;
 import com.minelittlepony.unicopia.particle.SphereParticleEffect;
@@ -16,7 +14,6 @@ import com.minelittlepony.unicopia.particle.UParticles;
 import com.minelittlepony.unicopia.projectile.ProjectileUtil;
 import com.minelittlepony.unicopia.util.shape.Sphere;
 
-import net.minecraft.enchantment.EnchantmentHelper;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.EyeOfEnderEntity;
 import net.minecraft.entity.FallingBlockEntity;
@@ -24,7 +21,6 @@ import net.minecraft.entity.LivingEntity;
 import net.minecraft.entity.TntEntity;
 import net.minecraft.entity.Entity.RemovalReason;
 import net.minecraft.entity.decoration.ArmorStandEntity;
-import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.entity.vehicle.AbstractMinecartEntity;
 import net.minecraft.entity.vehicle.BoatEntity;
 import net.minecraft.util.math.Vec3d;
@@ -160,50 +156,13 @@ public class ShieldSpell extends AbstractSpell {
         } else if (target instanceof LivingEntity) {
             double force = Math.max(0.1, radius / 4);
 
-            if (isFriendlyTogether(source) && target instanceof PlayerEntity) {
+            if (isFriendlyTogether(source)) {
-                force *= calculateAdjustedForce(Pony.of((PlayerEntity)target));
+                force *= AttractionUtils.getForceAdjustment(target);
             } else {
                 force *= 0.75;
             }
 
-            applyForce(pos, target, force, distance);
+            AttractionUtils.applyForce(pos, target, force, (distance < 1 ? distance : 0), false);
         }
     }
-
-    /**
-     * Applies a force to the given entity based on distance from the source.
-     */
-    protected void applyForce(Vec3d pos, Entity target, double force, double distance) {
-        pos = target.getPos().subtract(pos).normalize().multiply(force);
-
-        if (target instanceof LivingEntity) {
-            pos = pos.multiply(1 / (1 + EnchantmentHelper.getEquipmentLevel(UEnchantments.HEAVY, (LivingEntity)target)));
-        }
-
-        target.addVelocity(
-                pos.x,
-                pos.y + (distance < 1 ? distance : 0),
-                pos.z
-        );
-    }
-
-    /**
-     * Returns a force to apply based on the given player's given race.
-     */
-    protected double calculateAdjustedForce(Pony player) {
-        double force = 0.75;
-
-        if (player.getSpecies().canUseEarth()) {
-            force /= 2;
-
-            if (player.getMaster().isSneaking()) {
-                force /= 6;
-            }
-        } else if (player.getSpecies().canFly()) {
-            force *= 2;
-        }
-
-        return force;
-    }
-
 }

src/main/java/com/minelittlepony/unicopia/entity/EntityReference.java

@@ -62,6 +62,10 @@ public class EntityReference<T extends Entity> implements NbtSerialisable {
         return pos;
     }
 
+    public boolean referenceEquals(Entity entity) {
+        return entity != null && entity.getUuid().equals(uuid.orElse(null));
+    }
+
     public boolean isPresent(World world) {
         return getOrEmpty(world).isPresent();
     }

src/main/java/com/minelittlepony/unicopia/entity/player/Pony.java

@@ -598,6 +598,10 @@ public class Pony extends Living<PlayerEntity> implements Transmittable, Copieab
         return player == null ? null : ((PonyContainer<Pony>)player).get();
     }
 
+    public static Optional<Pony> of(Entity entity) {
+        return entity instanceof PlayerEntity ? PonyContainer.of(entity).map(a -> (Pony)a.get()) : Optional.empty();
+    }
+
     public static boolean equal(GameProfile one, GameProfile two) {
         return one == two || (one != null && two != null && one.getId().equals(two.getId()));
     }