Fixed casting

src/main/java/com/minelittlepony/unicopia/ability/UnicornCastingAbility.java

@@ -7,7 +7,6 @@ import org.jetbrains.annotations.Nullable;
 import com.google.common.collect.Streams;
 import com.minelittlepony.unicopia.Race;
 import com.minelittlepony.unicopia.ability.data.Hit;
-import com.minelittlepony.unicopia.ability.magic.spell.Spell;
 import com.minelittlepony.unicopia.ability.magic.spell.effect.CustomisedSpellType;
 import com.minelittlepony.unicopia.ability.magic.spell.effect.SpellType;
 import com.minelittlepony.unicopia.entity.player.Pony;
@@ -117,11 +116,14 @@ public class UnicornCastingAbility implements Ability<Hit> {
             if (newSpell.getResult() != ActionResult.FAIL) {
                 CustomisedSpellType<?> spell = newSpell.getValue();
 
-                player.subtractEnergyCost(spell.isEmpty() ? 2 : 4);
+                boolean remove = player.getSpellSlot().removeIf(spell, true);
+                player.subtractEnergyCost(remove ? 2 : 4);
+                if (!remove) {
                     spell.apply(player);
                 }
             }
         }
+    }
 
     private TypedActionResult<ItemStack> getAmulet(Pony player) {
 
@@ -139,12 +141,11 @@ public class UnicornCastingAbility implements Ability<Hit> {
     }
 
     private TypedActionResult<CustomisedSpellType<?>> getNewSpell(Pony player) {
-        final SpellType<?> current = player.getSpellSlot().get(true).map(Spell::getType).orElse(SpellType.empty());
         return Streams.stream(player.getMaster().getItemsHand())
                 .filter(GemstoneItem::isEnchanted)
-                .map(stack -> GemstoneItem.consumeSpell(stack, player.getMaster(), current, null))
+                .map(stack -> GemstoneItem.consumeSpell(stack, player.getMaster(), null, null))
                 .findFirst()
-                .orElse(TypedActionResult.<CustomisedSpellType<?>>pass((current == SpellType.EMPTY_KEY ? SpellType.SHIELD : SpellType.EMPTY_KEY).withTraits()));
+                .orElse(TypedActionResult.<CustomisedSpellType<?>>pass(SpellType.SHIELD.withTraits()));
     }
 
     @Override

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

@@ -22,7 +22,9 @@ public interface SpellContainer {
         public void clear() { }
 
         @Override
-        public void removeIf(Predicate<Spell> effect, boolean update) { }
+        public boolean removeIf(Predicate<Spell> effect, boolean update) {
+            return false;
+        }
 
         @Override
         public boolean forEach(Function<Spell, Operation> action, boolean update) {
@@ -56,8 +58,10 @@ public interface SpellContainer {
 
     /**
      * Removes all matching active effects.
+     *
+     * @return True if the collection was changed
      */
-    void removeIf(Predicate<Spell> test, boolean update);
+    boolean removeIf(Predicate<Spell> test, boolean update);
 
     /**
      * Iterates active spells and optionally removes matching ones.
@@ -86,8 +90,8 @@ public interface SpellContainer {
         }
 
         @Override
-        default void removeIf(Predicate<Spell> effect, boolean update) {
-            delegate().removeIf(effect, update);
+        default boolean removeIf(Predicate<Spell> effect, boolean update) {
+            return delegate().removeIf(effect, update);
         }
 
         @Override

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

@@ -3,11 +3,11 @@ package com.minelittlepony.unicopia.ability.magic.spell.effect;
 import org.jetbrains.annotations.Nullable;
 
 import com.minelittlepony.unicopia.ability.magic.Caster;
+import com.minelittlepony.unicopia.ability.magic.SpellPredicate;
 import com.minelittlepony.unicopia.ability.magic.spell.Spell;
 import com.minelittlepony.unicopia.ability.magic.spell.trait.SpellTraits;
 
-public class CustomisedSpellType<T extends Spell> {
-
+public class CustomisedSpellType<T extends Spell> implements SpellPredicate<T> {
     private final SpellType<T> type;
     private final SpellTraits traits;
 
@@ -28,4 +28,9 @@ public class CustomisedSpellType<T extends Spell> {
     public T apply(Caster<?> caster) {
         return type.apply(caster, traits);
     }
+
+    @Override
+    public boolean test(Spell spell) {
+        return type.test(spell);
+    }
 }

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

@@ -1,7 +1,6 @@
 package com.minelittlepony.unicopia.network.datasync;
 
 import java.util.Optional;
-import java.util.function.Consumer;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
@@ -61,28 +60,27 @@ public class EffectSync implements SpellContainer {
     }
 
     @Override
-    public void removeIf(Predicate<Spell> test, boolean update) {
-        forEach(effect -> {
-            if (test.test(effect)) {
-                spells.removeReference(effect);
+    public boolean removeIf(Predicate<Spell> test, boolean update) {
+        return reduce((initial, effect) -> {
+            if (!test.test(effect)) {
+                return initial;
             }
+            spells.removeReference(effect);
+            return true;
         });
     }
 
     @Override
     public boolean forEach(Function<Spell, Operation> test, boolean update) {
-        boolean[] matched = new boolean[1];
-
-        forEach(effect -> {
+        return reduce((initial, effect) -> {
             Operation op = test.apply(effect);
             if (op == Operation.REMOVE) {
                 spells.removeReference(effect);
             } else {
-                matched[0] |= op != Operation.SKIP;
+                initial |= op != Operation.SKIP;
             }
+            return initial;
         });
-
-        return matched[0];
     }
 
     @Override
@@ -103,10 +101,16 @@ public class EffectSync implements SpellContainer {
         return spells.getReferences();
     }
 
-    public void forEach(Consumer<Spell> consumer) {
+    public boolean reduce(Alteration alteration) {
         spells.fromNbt(owner.getEntity().getDataTracker().get(param));
-        spells.getReferences().toList().forEach(consumer);
+
+        boolean initial = false;
+        for (Spell i : spells.getReferences().toList()) {
+            initial = alteration.apply(initial, i);
+        }
+
         write();
+        return initial;
     }
 
     private void write() {
@@ -118,4 +122,8 @@ public class EffectSync implements SpellContainer {
     public interface UpdateCallback {
         void onSpellSet(@Nullable Spell spell);
     }
+
+    private interface Alteration {
+        boolean apply(boolean initial, Spell item);
+    }
 }