Custom Potion Mixes

paper-api/src/main/java/io/papermc/paper/potion/PotionMix.java

@@ -0,0 +1,103 @@
+package io.papermc.paper.potion;
+
+import java.util.Objects;
+import java.util.function.Predicate;
+import org.bukkit.Keyed;
+import org.bukkit.NamespacedKey;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.RecipeChoice;
+import org.jetbrains.annotations.Contract;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Represents a potion mix made in a Brewing Stand.
+ */
+@NullMarked
+public final class PotionMix implements Keyed {
+
+    private final NamespacedKey key;
+    private final ItemStack result;
+    private final RecipeChoice input;
+    private final RecipeChoice ingredient;
+
+    /**
+     * Creates a new potion mix. Add it to the server with {@link org.bukkit.potion.PotionBrewer#addPotionMix(PotionMix)}.
+     *
+     * @param key a unique key for the mix
+     * @param result the resulting itemstack that will appear in the 3 bottom slots
+     * @param input the input placed into the bottom 3 slots
+     * @param ingredient the ingredient placed into the top slot
+     */
+    public PotionMix(final NamespacedKey key, final ItemStack result, final RecipeChoice input, final RecipeChoice ingredient) {
+        this.key = key;
+        this.result = result;
+        this.input = input;
+        this.ingredient = ingredient;
+    }
+
+    /**
+     * Create a {@link RecipeChoice} based on a Predicate. These RecipeChoices are only
+     * valid for {@link PotionMix}, not anywhere else RecipeChoices may be used.
+     *
+     * @param stackPredicate a predicate for an itemstack.
+     * @return a new RecipeChoice
+     */
+    @Contract(value = "_ -> new", pure = true)
+    public static RecipeChoice createPredicateChoice(final Predicate<? super ItemStack> stackPredicate) {
+        return new PredicateRecipeChoice(stackPredicate);
+    }
+
+    @Override
+    public NamespacedKey getKey() {
+        return this.key;
+    }
+
+    /**
+     * Gets the resulting itemstack after the brew has finished.
+     *
+     * @return the result itemstack
+     */
+    public ItemStack getResult() {
+        return this.result;
+    }
+
+    /**
+     * Gets the input for the bottom 3 slots in the brewing stand.
+     *
+     * @return the bottom 3 slot ingredients
+     */
+    public RecipeChoice getInput() {
+        return this.input;
+    }
+
+    /**
+     * Gets the ingredient in the top slot of the brewing stand.
+     *
+     * @return the top slot input
+     */
+    public RecipeChoice getIngredient() {
+        return this.ingredient;
+    }
+
+    @Override
+    public String toString() {
+        return "PotionMix{" +
+            "result=" + this.result +
+            ", base=" + this.input +
+            ", addition=" + this.ingredient +
+            '}';
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) return true;
+        if (o == null || this.getClass() != o.getClass()) return false;
+        final PotionMix potionMix = (PotionMix) o;
+        return this.key.equals(potionMix.key) && this.result.equals(potionMix.result) && this.input.equals(potionMix.input) && this.ingredient.equals(potionMix.ingredient);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(this.key, this.result, this.input, this.ingredient);
+    }
+}

paper-api/src/main/java/io/papermc/paper/potion/PredicateRecipeChoice.java

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+package io.papermc.paper.potion;
+
+import java.util.function.Predicate;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.RecipeChoice;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+@ApiStatus.Internal
+@NullMarked
+record PredicateRecipeChoice(Predicate<? super ItemStack> itemStackPredicate) implements RecipeChoice, Cloneable {
+
+    @Override
+    @Deprecated
+    public ItemStack getItemStack() {
+        throw new UnsupportedOperationException("PredicateRecipeChoice does not support this");
+    }
+
+    @Override
+    public RecipeChoice clone() {
+        try {
+            return (PredicateRecipeChoice) super.clone();
+        } catch (final CloneNotSupportedException ex) {
+            throw new AssertionError(ex);
+        }
+    }
+
+    @Override
+    public boolean test(final ItemStack itemStack) {
+        return this.itemStackPredicate.test(itemStack);
+    }
+}