content: /*
   * Copyright (C) 2020 ActiveJ LLC.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package io.activej.async.function;
  
  import io.activej.async.process.AsyncExecutor;
  import io.activej.async.process.AsyncExecutors;
  import io.activej.promise.Promise;
  import io.activej.promise.Promises;
  import org.jetbrains.annotations.Contract;
  import org.jetbrains.annotations.Nullable;
  
  public final class AsyncRunnables {
  
  	@Contract(pure = true)
  	public static AsyncRunnable reuse(AsyncRunnable actual) {
  		return new AsyncRunnable() {
  			@Nullable Promise<Void> runningPromise;
  
  			@Override
  			public Promise<Void> run() {
  				if (runningPromise != null) return runningPromise;
  				runningPromise = actual.run();
  				Promise<Void> runningPromise = this.runningPromise;
  				runningPromise.whenComplete(() -> this.runningPromise = null);
  				return runningPromise;
  			}
  		};
  	}
  
  	@Contract(pure = true)
  	public static AsyncRunnable coalesce(AsyncRunnable actual) {
  		AsyncFunction<Void, Void> fn = Promises.coalesce(() -> null, (a, v) -> {}, a -> actual.run());
  		return () -> fn.apply(null);
  	}
  
  	@Contract(pure = true)
  	public static AsyncRunnable buffer(AsyncRunnable actual) {
  		return buffer(1, Integer.MAX_VALUE, actual);
  	}
  
  	@Contract(pure = true)
  	public static AsyncRunnable buffer(int maxParallelCalls, int maxBufferedCalls, AsyncRunnable runnable) {
  		return ofExecutor(AsyncExecutors.buffered(maxParallelCalls, maxBufferedCalls), runnable);
  	}
  
  	@Contract(pure = true)
  	public static AsyncRunnable ofExecutor(AsyncExecutor executor, AsyncRunnable runnable) {
  		return () -> executor.execute(runnable::run);
  	}
  }
  