feat(api): bossbar platform implementation

api/src/main/java/net/kyori/adventure/bossbar/BossBarImpl.java

@@ -27,6 +27,7 @@
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.BiConsumer;
@@ -35,8 +36,11 @@
 import java.util.stream.Stream;
 import net.kyori.adventure.internal.Internals;
 import net.kyori.adventure.text.Component;
+import net.kyori.adventure.util.Services;
 import net.kyori.examination.ExaminableProperty;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import static java.util.Objects.requireNonNull;
 
@@ -48,6 +52,26 @@ final class BossBarImpl extends HackyBossBarPlatformBridge implements BossBar {
   private Color color;
   private Overlay overlay;
   private final Set<Flag> flags = EnumSet.noneOf(Flag.class);
+  @Nullable BossBarImplementation implementation;
+
+  @ApiStatus.Internal
+  static final class ImplementationAccessor {
+    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    private static final Optional<BossBarImplementation.Provider> SERVICE = Services.service(BossBarImplementation.Provider.class);
+
+    private ImplementationAccessor() {
+    }
+
+    @SuppressWarnings("OptionalGetWithoutIsPresent")
+    static @NotNull <I extends BossBarImplementation> I get(final @NotNull BossBar bar, final @NotNull Class<I> type) {
+      @Nullable BossBarImplementation implementation = ((BossBarImpl) bar).implementation;
+      if (implementation == null) {
+        implementation = SERVICE.get().create(bar);
+        ((BossBarImpl) bar).implementation = implementation;
+      }
+      return type.cast(implementation);
+    }
+  }
 
   BossBarImpl(final @NotNull Component name, final float progress, final @NotNull Color color, final @NotNull Overlay overlay) {
     this.name = requireNonNull(name, "name");

api/src/main/java/net/kyori/adventure/bossbar/BossBarImplementation.java

@@ -0,0 +1,67 @@
+/*
+ * This file is part of adventure, licensed under the MIT License.
+ *
+ * Copyright (c) 2017-2022 KyoriPowered
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package net.kyori.adventure.bossbar;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * {@link BossBar} internal implementation.
+ *
+ * @since 4.12.0
+ */
+@ApiStatus.Internal
+public interface BossBarImplementation {
+  /**
+   * Gets an implementation, and casts it to {@code type}.
+   *
+   * @param bar the bossbar
+   * @param type the implementation type
+   * @param <I> the implementation type
+   * @return a {@code I}
+   * @since 4.12.0
+   */
+  @ApiStatus.Internal
+  static <I extends BossBarImplementation> @NotNull I get(final @NotNull BossBar bar, final @NotNull Class<I> type) {
+    return BossBarImpl.ImplementationAccessor.get(bar, type);
+  }
+
+  /**
+   * A {@link BossBarImplementation} service provider.
+   *
+   * @since 4.12.0
+   */
+  @ApiStatus.Internal
+  interface Provider {
+    /**
+     * Gets an implementation.
+     *
+     * @param bar the bossbar
+     * @return a {@code I}
+     * @since 4.12.0
+     */
+    @ApiStatus.Internal
+    @NotNull BossBarImplementation create(final @NotNull BossBar bar);
+  }
+}