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.testsupport;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.operators.QueueDisposable;
  import io.reactivex.rxjava3.operators.QueueFuseable;
  
  /**
   * An  extended test Observer that records events and allows making assertions about them.
   *
   * <p>You can override the onSubscribe, onNext, onError, onComplete, onSuccess and
   * cancel methods but not the others (this is by design).
   *
   * <p>The TestObserver implements Disposable for convenience where dispose calls cancel.
   *
   * @param <T> the value type
   */
  public class TestObserverEx<T>
  extends BaseTestConsumerEx<T, TestObserverEx<T>>
  implements Observer<T>, Disposable, MaybeObserver<T>, SingleObserver<T>, CompletableObserver {
      /** The actual observer to forward events to. */
      private final Observer<? super T> downstream;
  
      /** Holds the current subscription if any. */
      private final AtomicReference<Disposable> upstream = new AtomicReference<>();
  
      private QueueDisposable<T> qd;
  
      /**
       * Constructs a non-forwarding TestObserver.
       */
      public TestObserverEx() {
          this(EmptyObserver.INSTANCE);
      }
  
      /**
       * Constructs a forwarding TestObserver.
       * @param downstream the actual Observer to forward events to
       */
      public TestObserverEx(Observer<? super T> downstream) {
          this.downstream = downstream;
      }
  
      /**
       * Constructs a TestObserverEx with the given initial fusion mode.
       * @param fusionMode the fusion mode, see {@link QueueFuseable}
       */
      public TestObserverEx(int fusionMode) {
          this();
          setInitialFusionMode(fusionMode);
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public void onSubscribe(Disposable d) {
          lastThread = Thread.currentThread();
  
          if (d == null) {
              errors.add(new NullPointerException("onSubscribe received a null Subscription"));
              return;
          }
          if (!upstream.compareAndSet(null, d)) {
              d.dispose();
              if (upstream.get() != DisposableHelper.DISPOSED) {
                  errors.add(new IllegalStateException("onSubscribe received multiple subscriptions: " + d));
              }
              return;
          }
  
          if (initialFusionMode != 0) {
              if (d instanceof QueueDisposable) {
                  qd = (QueueDisposable<T>)d;
  
                  int m = qd.requestFusion(initialFusionMode);
                  establishedFusionMode = m;
  
                  if (m == QueueFuseable.SYNC) {
                      checkSubscriptionOnce = true;
                      lastThread = Thread.currentThread();
                      try {
                          T t;
                          while ((t = qd.poll()) != null) {
                              values.add(t);
                          }
                          completions++;
  
                          upstream.lazySet(DisposableHelper.DISPOSED);
                      } catch (Throwable ex) {
                          errors.add(ex);
                      }
                      return;
                  }
              }
          }
  
          downstream.onSubscribe(d);
      }
  
      @Override
      public void onNext(T t) {
          if (!checkSubscriptionOnce) {
              checkSubscriptionOnce = true;
              if (upstream.get() == null) {
                  errors.add(new IllegalStateException("onSubscribe not called in proper order"));
              }
          }
  
          lastThread = Thread.currentThread();
  
          if (establishedFusionMode == QueueFuseable.ASYNC) {
              try {
                  while ((t = qd.poll()) != null) {
                      values.add(t);
                  }
              } catch (Throwable ex) {
                  errors.add(ex);
                  qd.dispose();
              }
              return;
          }
  
          values.add(t);
  
          if (t == null) {
              errors.add(new NullPointerException("onNext received a null value"));
          }
  
          downstream.onNext(t);
      }
  
      @Override
      public void onError(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 dispose() {
          DisposableHelper.dispose(upstream);
      }
  
      @Override
      public final boolean isDisposed() {
          return DisposableHelper.isDisposed(upstream.get());
      }
  
      // state retrieval methods
      /**
       * Returns true if this TestObserver received a subscription.
       * @return true if this TestObserver received a subscription
       */
      public final boolean hasSubscription() {
          return upstream.get() != null;
      }
  
      /**
       * Assert that the onSubscribe method was called exactly once.
       * @return this;
       */
      @Override
      public final TestObserverEx<T> assertSubscribed() {
          if (upstream.get() == null) {
              throw fail("Not subscribed!");
          }
          return this;
      }
  
      /**
       * Assert that the onSubscribe method hasn't been called at all.
       * @return this;
       */
      public final TestObserverEx<T> assertNotSubscribed() {
          if (upstream.get() != null) {
              throw fail("Subscribed!");
          } else
          if (!errors.isEmpty()) {
              throw fail("Not subscribed but errors found");
          }
          return this;
      }
  
      /**
       * Sets the initial fusion mode if the upstream supports fusion.
       * <p>Package-private: avoid leaking the now internal fusion properties into the public API.
       * Use ObserverFusion to work with such tests.
       * @param mode the mode to establish, see the {@link QueueDisposable} constants
       * @return this
       */
      public final TestObserverEx<T> setInitialFusionMode(int mode) {
          this.initialFusionMode = mode;
          return this;
      }
  
      /**
       * Asserts that the given fusion mode has been established
       * <p>Package-private: avoid leaking the now internal fusion properties into the public API.
       * Use ObserverFusion to work with such tests.
       * @param mode the expected mode
       * @return this
       */
      public final TestObserverEx<T> assertFusionMode(int mode) {
          int m = establishedFusionMode;
          if (m != mode) {
              if (qd != null) {
                  throw new AssertionError("\nexpected: " + fusionModeToString(mode)
                  + "\ngot: " + fusionModeToString(m) + "; Fusion mode different");
              } else {
                  throw fail("Upstream is not fuseable");
              }
          }
          return this;
      }
  
      /**
       * Assert that the upstream is a fuseable source.
       * <p>Package-private: avoid leaking the now internal fusion properties into the public API.
       * Use ObserverFusion to work with such tests.
       * @return this
       */
      public final TestObserverEx<T> assertFuseable() {
          if (qd == null) {
              throw new AssertionError("Upstream is not fuseable.");
          }
          return this;
      }
  
      /**
       * Assert that the upstream is not a fuseable source.
       * <p>Package-private: avoid leaking the now internal fusion properties into the public API.
       * Use ObserverFusion to work with such tests.
       * @return this
       */
      public final TestObserverEx<T> assertNotFuseable() {
          if (qd != null) {
              throw new AssertionError("Upstream is fuseable.");
          }
          return this;
      }
  
      @Override
      public void onSuccess(T value) {
          onNext(value);
          onComplete();
      }
  
      /**
       * An observer that ignores all events and does not report errors.
       */
      enum EmptyObserver implements Observer<Object> {
          INSTANCE;
  
          @Override
          public void onSubscribe(Disposable d) {
          }
  
          @Override
          public void onNext(Object t) {
          }
  
          @Override
          public void onError(Throwable t) {
          }
  
          @Override
          public void onComplete() {
          }
      }
  }
  