Expand PotionMeta Api to allow getting effective potion colour and effects (#12390)

paper-api/src/main/java/io/papermc/paper/datacomponent/item/PotionContents.java

@@ -60,6 +60,27 @@ public interface PotionContents {
     @Contract(pure = true)
     @Nullable String customName();
 
+    /**
+     * All effects that this component applies.
+     * <p>
+     * This is a combination of the base potion type and any custom effects.
+     *
+     * @return an unmodifiable list of all effects.
+     */
+    @Contract(pure = true)
+    @Unmodifiable List<PotionEffect> allEffects();
+
+    /**
+     * Computes the effective colour of this potion contents component.
+     * <p>
+     * This blends all custom effects, or uses a default fallback colour.
+     * It may or may not have an alpha channel, used for tipped arrows.
+     *
+     * @return the effective colour this component would display with.
+     */
+    @Contract(pure = true)
+    Color computeEffectiveColor();
+
     @ApiStatus.Experimental
     @ApiStatus.NonExtendable
     interface Builder extends DataComponentBuilder<PotionContents> {

paper-api/src/main/java/org/bukkit/inventory/meta/PotionMeta.java

@@ -8,6 +8,7 @@ import org.bukkit.potion.PotionEffectType;
 import org.bukkit.potion.PotionType;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.Unmodifiable;
 
 /**
  * Represents a potion or item that can have custom effects.
@@ -74,6 +75,16 @@ public interface PotionMeta extends ItemMeta {
     @NotNull
     List<PotionEffect> getCustomEffects();
 
+    /**
+     * All effects that this potion meta holds.
+     * <p>
+     * This is a combination of the base potion type and any custom effects.
+     *
+     * @return an unmodifiable list of all effects.
+     */
+    @NotNull
+    @Unmodifiable List<PotionEffect> getAllEffects();
+
     /**
      * Adds a custom potion effect to this potion.
      *
@@ -146,6 +157,16 @@ public interface PotionMeta extends ItemMeta {
      */
     void setColor(@Nullable Color color);
 
+    /**
+     * Computes the effective colour of this potion meta.
+     * <p>
+     * This blends all custom effects, or uses a default fallback color.
+     *
+     * @return the effective potion color
+     */
+    @NotNull
+    Color computeEffectiveColor();
+
     /**
      * Checks for existence of a custom potion name translation suffix.
      *

paper-server/src/main/java/io/papermc/paper/datacomponent/item/PaperPotionContents.java

@@ -5,6 +5,8 @@ import io.papermc.paper.util.MCUtil;
 import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
 import net.minecraft.world.effect.MobEffectInstance;
 import org.bukkit.Color;
 import org.bukkit.craftbukkit.potion.CraftPotionType;
@@ -48,6 +50,19 @@ public record PaperPotionContents(
         return this.impl.customName().orElse(null);
     }
 
+    @Override
+    public @Unmodifiable List<PotionEffect> allEffects() {
+        //noinspection SimplifyStreamApiCallChains - explicity want it unmodifiable, as toList() api doesnt guarantee this.
+        return StreamSupport.stream(this.impl.getAllEffects().spliterator(), false)
+            .map(CraftPotionUtil::toBukkit)
+            .collect(Collectors.toUnmodifiableList());
+    }
+
+    @Override
+    public Color computeEffectiveColor() {
+        return Color.fromARGB(this.impl.getColor());
+    }
+
     static final class BuilderImpl implements PotionContents.Builder {
 
         private final List<MobEffectInstance> customEffects = new ObjectArrayList<>();

paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaPotion.java

@@ -1,6 +1,7 @@
 package org.bukkit.craftbukkit.inventory;
 
 import com.google.common.base.Preconditions;
+import com.google.common.collect.Collections2;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap.Builder;
 import java.util.ArrayList;
@@ -25,6 +26,7 @@ import org.bukkit.potion.PotionData;
 import org.bukkit.potion.PotionEffect;
 import org.bukkit.potion.PotionEffectType;
 import org.bukkit.potion.PotionType;
+import org.jetbrains.annotations.NotNull;
 
 @DelegateDeserialization(SerializableMeta.class)
 class CraftMetaPotion extends CraftMetaItem implements PotionMeta {
@@ -202,6 +204,19 @@ class CraftMetaPotion extends CraftMetaItem implements PotionMeta {
         return ImmutableList.of();
     }
 
+    @Override
+    @NotNull
+    public List<PotionEffect> getAllEffects() {
+        final ImmutableList.Builder<PotionEffect> builder = ImmutableList.builder();
+        if (this.hasBasePotionType()) {
+            builder.addAll(this.getBasePotionType().getPotionEffects());
+        }
+        if (this.hasCustomEffects()) {
+            builder.addAll(this.customEffects);
+        }
+        return builder.build();
+    }
+
     @Override
     public boolean addCustomEffect(PotionEffect effect, boolean overwrite) {
         Preconditions.checkArgument(effect != null, "Potion effect cannot be null");
@@ -305,6 +320,17 @@ class CraftMetaPotion extends CraftMetaItem implements PotionMeta {
         this.color = color == null ? null : color.asRGB();
     }
 
+    @Override
+    @NotNull
+    public Color computeEffectiveColor() {
+        if (hasColor()) return getColor();
+
+        return Color.fromRGB(
+            PotionContents.getColorOptional(Collections2.transform(getAllEffects(), CraftPotionUtil::fromBukkit))
+                .orElse(PotionContents.BASE_POTION_COLOR) & 0xFFFFFF
+        );
+    }
+
     @Override
     public boolean hasCustomPotionName() {
         return this.customName != null;