/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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 Lice`nse 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 androidx.test.rule;

import android.os.Debug;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

/**
 * The {@code DisableOnAndroidDebug} Rule allows you to label certain rules to be disabled when
 * debugging.
 *
 * <p>The most illustrative use case is for tests that make use of the <a
 * href="http://junit.org/apidocs/org/junit/rules/Timeout.html"><code>Timeout</code></a> rule, when
 * ran in debug mode the test may terminate on timeout abruptly during debugging. Developers may
 * disable the timeout, or increase the timeout by making a code change on tests that need debugging
 * and remember revert the change afterwards or rules such as <a
 * href="http://junit.org/apidocs/org/junit/rules/Timeout.html"><code>Timeout</code></a> that may be
 * disabled during debugging may be wrapped in a {@code DisableOnDebug}.
 *
 * <p>The important benefit of this feature is that you can disable such rules without any making
 * any modifications to your test class to remove them during debugging.
 *
 * <p>This does nothing to tackle timeouts or time sensitive code under test when debugging and may
 * make this less useful in such circumstances.
 *
 * <p>Example usage:
 *
 * <pre>
 * public static class DisableTimeoutOnDebugSampleTest {
 *
 *     &#064;Rule
 *     public TestRule timeout = new DisableOnAndroidDebug(new Timeout(20));
 *
 *     &#064;Test
 *     public void myTest() {
 *         int i = 0;
 *         assertEquals(0, i); // suppose you had a break point here to inspect i
 *     }
 * }
 * </pre>
 */
// NOTE The docs and API of this class is copied from JUnit 4.12. The implementation is not.
public class DisableOnAndroidDebug implements TestRule {
  private final TestRule rule;

  /**
   * Wrap another {@link TestRule} and conditionally disable it when a debugger is attached.
   *
   * @param rule to disable during debugging
   */
  public DisableOnAndroidDebug(TestRule rule) {
    this.rule = rule;
  }

  /** {@inheritDoc} */
  @Override
  public final Statement apply(final Statement base, Description description) {
    if (isDebugging()) {
      return base;
    }
    return rule.apply(base, description);
  }

  /**
   * Returns {@code true} if the VM has a debugger connected. This method may be used by test
   * classes to take additional action to disable code paths that interfere with debugging if
   * required.
   *
   * @return {@code true} if a debugger is connected, {@code false} otherwise
   */
  public boolean isDebugging() {
    return Debug.isDebuggerConnected();
  }
}