/**
    * Copyright (c) 2016-present, RxJava Contributors.
    *
    * 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 com.github.davidmoten.rx2.flowable;
  
  import java.util.Arrays;
  import java.util.List;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.reactivestreams.Subscriber;
  import org.reactivestreams.Subscription;
  
  import io.reactivex.Flowable;
  import io.reactivex.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.internal.util.BackpressureHelper;
  
  /**
   * Creates {@link Flowable} of a number of items followed by either an error or
   * completion. Cancellation has no effect on preventing emissions until the
   * currently outstanding requests have been met. The primary purpose for the
   * existence of this class is testing that an operator that calls `onError` when
   * processing `onNext` for instance does not emit multiple terminal events.
   * 
   * @param <T>
   *            the value type
   */
  public final class Burst<T> extends Flowable<T> {
  
      private final List<T> items;
      private final Throwable error;
  
      private Burst(Throwable error, List<T> items) {
          if (items.isEmpty()) {
              throw new IllegalArgumentException("items cannot be empty");
          }
          for (T item : items) {
              if (item == null) {
                  throw new IllegalArgumentException("items cannot include null");
              }
          }
          this.error = error;
          this.items = items;
      }
  
      @Override
      protected void subscribeActual(final Subscriber<? super T> subscriber) {
          subscriber.onSubscribe(new Subscription() {
  
              final Queue<T> q = new ConcurrentLinkedQueue<T>(items);
              final AtomicLong requested = new AtomicLong();
              volatile boolean cancelled;
  
              @Override
              public void request(long n) {
                  if (cancelled) {
                      // required by reactive-streams-jvm 3.6
                      return;
                  }
                  if (SubscriptionHelper.validate(n)) {
                      // just for testing, don't care about perf
                      // so no attempt made to reduce volatile reads
                      if (BackpressureHelper.add(requested, n) == 0) {
                          if (q.isEmpty()) {
                              return;
                          }
                          while (!q.isEmpty() && requested.get() > 0) {
                              T item = q.poll();
                              requested.decrementAndGet();
                              subscriber.onNext(item);
                          }
                          if (q.isEmpty()) {
                              if (error != null) {
                                  subscriber.onError(error);
                              } else {
                                  subscriber.onComplete();
                              }
                          }
                      }
                  }
              }
  
              @Override
              public void cancel() {
                  cancelled = true;
              }
          });
  
      }
 
     @SuppressWarnings("unchecked")
     public static <T> Builder<T> item(T item) {
         return items(item);
     }
 
     public static <T> Builder<T> items(T... items) {
         return new Builder<T>(Arrays.asList(items));
     }
 
     public static final class Builder<T> {
 
         private final List<T> items;
         private Throwable error;
 
         private Builder(List<T> items) {
             this.items = items;
         }
 
         public Flowable<T> error(Throwable e) {
             this.error = e;
             return create();
         }
 
         public Flowable<T> create() {
             return new Burst<T>(error, items);
         }
 
     }
 
 }