code: /*
   * 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 io.reactivex.rxjava3.subscribers;
  
  import java.util.concurrent.atomic.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.FlowableSubscriber;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.observers.BaseTestConsumer;
  
  /**
   * A {@link Subscriber} implementation that records events and allows making assertions about them.
   *
   * <p>You can override the {@link #onSubscribe(Subscription)}, {@link #onNext(Object)}, {@link #onError(Throwable)} and
   * {@link #onComplete()} methods but not the others (this is by design).
   *
   * <p>When calling the default request method, you are requesting on behalf of the
   * wrapped actual {@link Subscriber} if any.
   *
   * @param <T> the value type
   */
  public class TestSubscriber<T>
  extends BaseTestConsumer<T, TestSubscriber<T>>
  implements FlowableSubscriber<T>, Subscription {
      /** The actual subscriber to forward events to. */
      private final Subscriber<? super T> downstream;
  
      /** Makes sure the incoming Subscriptions get cancelled immediately. */
      private volatile boolean cancelled;
  
      /** Holds the current subscription if any. */
      private final AtomicReference<Subscription> upstream;
  
      /** Holds the requested amount until a subscription arrives. */
      private final AtomicLong missedRequested;
  
      /**
       * Creates a {@code TestSubscriber} with {@link Long#MAX_VALUE} initial request amount.
       * @param <T> the value type
       * @return the new {@code TestSubscriber} instance.
       * @see #create(long)
       */
      @NonNull
      public static <T> TestSubscriber<T> create() {
          return new TestSubscriber<>();
      }
  
      /**
       * Creates a {@code TestSubscriber} with the given initial request amount.
       * @param <T> the value type
       * @param initialRequested the initial requested amount
       * @return the new {@code TestSubscriber} instance.
       */
      @NonNull
      public static <T> TestSubscriber<T> create(long initialRequested) {
          return new TestSubscriber<>(initialRequested);
      }
  
      /**
       * Constructs a forwarding {@code TestSubscriber}.
       * @param <T> the value type received
       * @param delegate the actual {@link Subscriber} to forward events to
       * @return the new TestObserver instance
       */
      public static <T> TestSubscriber<T> create(@NonNull Subscriber<? super T> delegate) {
          return new TestSubscriber<>(delegate);
      }
  
      /**
       * Constructs a non-forwarding {@code TestSubscriber} with an initial request value of {@link Long#MAX_VALUE}.
       */
      public TestSubscriber() {
          this(EmptySubscriber.INSTANCE, Long.MAX_VALUE);
      }
  
      /**
       * Constructs a non-forwarding {@code TestSubscriber} with the specified initial request value.
       * <p>The {@code TestSubscriber} doesn't validate the {@code initialRequest} amount so one can
       * test sources with invalid values as well.
       * @param initialRequest the initial request amount
       */
      public TestSubscriber(long initialRequest) {
          this(EmptySubscriber.INSTANCE, initialRequest);
      }
  
      /**
       * Constructs a forwarding {@code TestSubscriber} but leaves the requesting to the wrapped {@link Subscriber}.
       * @param downstream the actual {@code Subscriber} to forward events to
       */
      public TestSubscriber(@NonNull Subscriber<? super T> downstream) {
          this(downstream, Long.MAX_VALUE);
      }
  
      /**
       * Constructs a forwarding {@code TestSubscriber} with the specified initial request amount
       * and an actual {@link Subscriber} to forward events to.
       * <p>The {@code TestSubscriber} doesn't validate the initialRequest value so one can
       * test sources with invalid values as well.
       * @param actual the actual {@code Subscriber} to forward events to
       * @param initialRequest the initial request amount
       */
      public TestSubscriber(@NonNull Subscriber<? super T> actual, long initialRequest) {
          super();
          if (initialRequest < 0) {
              throw new IllegalArgumentException("Negative initial request not allowed");
          }
          this.downstream = actual;
          this.upstream = new AtomicReference<>();
          this.missedRequested = new AtomicLong(initialRequest);
      }
  
      @Override
      public void onSubscribe(@NonNull Subscription s) {
          lastThread = Thread.currentThread();
  
          if (s == null) {
              errors.add(new NullPointerException("onSubscribe received a null Subscription"));
              return;
          }
          if (!upstream.compareAndSet(null, s)) {
              s.cancel();
              if (upstream.get() != SubscriptionHelper.CANCELLED) {
                  errors.add(new IllegalStateException("onSubscribe received multiple subscriptions: " + s));
              }
              return;
          }
  
          downstream.onSubscribe(s);
  
          long mr = missedRequested.getAndSet(0L);
          if (mr != 0L) {
              s.request(mr);
          }
  
          onStart();
      }
  
      /**
       * Called after the onSubscribe is called and handled.
       */
      protected void onStart() {
  
      }
  
      @Override
      public void onNext(@NonNull T t) {
          if (!checkSubscriptionOnce) {
              checkSubscriptionOnce = true;
              if (upstream.get() == null) {
                  errors.add(new IllegalStateException("onSubscribe not called in proper order"));
              }
          }
          lastThread = Thread.currentThread();
  
          values.add(t);
  
          if (t == null) {
              errors.add(new NullPointerException("onNext received a null value"));
          }
  
          downstream.onNext(t);
      }
  
      @Override
      public void onError(@NonNull Throwable t) {
          if (!checkSubscriptionOnce) {
              checkSubscriptionOnce = true;
              if (upstream.get() == null) {
                  errors.add(new IllegalStateException("onSubscribe not called in proper order"));
              }
          }
          try {
              lastThread = Thread.currentThread();
  
              if (t == null) {
                  errors.add(new NullPointerException("onError received a null Throwable"));
              } else {
                  errors.add(t);
              }
  
              downstream.onError(t);
          } finally {
              done.countDown();
          }
      }
  
      @Override
      public void onComplete() {
          if (!checkSubscriptionOnce) {
              checkSubscriptionOnce = true;
              if (upstream.get() == null) {
                  errors.add(new IllegalStateException("onSubscribe not called in proper order"));
              }
          }
          try {
              lastThread = Thread.currentThread();
              completions++;
  
              downstream.onComplete();
          } finally {
              done.countDown();
          }
      }
  
      @Override
      public final void request(long n) {
          SubscriptionHelper.deferredRequest(upstream, missedRequested, n);
      }
  
      @Override
      public final void cancel() {
          if (!cancelled) {
              cancelled = true;
              SubscriptionHelper.cancel(upstream);
          }
      }
  
      /**
       * Returns true if this {@code TestSubscriber} has been cancelled.
       * @return true if this {@code TestSubscriber} has been cancelled
       */
      public final boolean isCancelled() {
          return cancelled;
      }
  
      @Override
      protected final void dispose() {
          cancel();
      }
  
      @Override
      protected final boolean isDisposed() {
          return cancelled;
      }
  
      // state retrieval methods
  
      /**
       * Returns true if this {@code TestSubscriber} received a {@link Subscription} via {@link #onSubscribe(Subscription)}.
       * @return true if this {@code TestSubscriber} received a {@link Subscription} via {@link #onSubscribe(Subscription)}
       */
      public final boolean hasSubscription() {
          return upstream.get() != null;
      }
  
      // assertion methods
  
      /**
       * Assert that the {@link #onSubscribe(Subscription)} method was called exactly once.
       * @return this
       */
      @Override
      protected final TestSubscriber<T> assertSubscribed() {
          if (upstream.get() == null) {
              throw fail("Not subscribed!");
          }
          return this;
      }
  
      /**
       * Calls {@link #request(long)} and returns this.
       * <p>History: 2.0.1 - experimental
       * @param n the request amount
       * @return this
       * @since 2.1
       */
      public final TestSubscriber<T> requestMore(long n) {
          request(n);
          return this;
      }
  
      /**
       * A subscriber that ignores all events and does not report errors.
       */
      enum EmptySubscriber implements FlowableSubscriber<Object> {
          INSTANCE;
  
          @Override
          public void onSubscribe(Subscription s) {
          }
  
          @Override
          public void onNext(Object t) {
          }
  
          @Override
          public void onError(Throwable t) {
          }
  
          @Override
          public void onComplete() {
          }
      }
  }
  