Break circular dependency between core and util (#379)

* Break circular dependency between core and util

Created a new :common project and moved a minimum
number of classes to break the circular dependency
between the two projects. This gets rid of the
gradle lint dependency warnings.

Also separated api classes and testing helpers into
separate source sets in :common so that testing
classes may be restricted to test configurations.

common/src/testing/java/google/registry/testing/FakeClock.java

@@ -0,0 +1,68 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.testing;
+
+import static google.registry.util.DateTimeUtils.START_OF_TIME;
+import static org.joda.time.DateTimeZone.UTC;
+import static org.joda.time.Duration.millis;
+
+import google.registry.util.Clock;
+import java.util.concurrent.atomic.AtomicLong;
+import javax.annotation.concurrent.ThreadSafe;
+import org.joda.time.DateTime;
+import org.joda.time.ReadableDuration;
+import org.joda.time.ReadableInstant;
+
+/** A mock clock for testing purposes that supports telling, setting, and advancing the time. */
+@ThreadSafe
+public final class FakeClock implements Clock {
+
+  private static final long serialVersionUID = 675054721685304599L;
+
+  // Clock isn't a thread synchronization primitive, but tests involving
+  // threads should see a consistent flow.
+  private final AtomicLong currentTimeMillis = new AtomicLong();
+
+  /** Creates a FakeClock that starts at START_OF_TIME. */
+  public FakeClock() {
+    this(START_OF_TIME);
+  }
+
+  /** Creates a FakeClock initialized to a specific time. */
+  public FakeClock(ReadableInstant startTime) {
+    setTo(startTime);
+  }
+
+  /** Returns the current time. */
+  @Override
+  public DateTime nowUtc() {
+    return new DateTime(currentTimeMillis.get(), UTC);
+  }
+
+  /** Advances clock by one millisecond. */
+  public void advanceOneMilli() {
+    advanceBy(millis(1));
+  }
+
+  /** Advances clock by some duration. */
+  public void advanceBy(ReadableDuration duration) {
+    currentTimeMillis.addAndGet(duration.getMillis());
+  }
+
+  /** Sets the time to the specified instant. */
+  public void setTo(ReadableInstant time) {
+    currentTimeMillis.set(time.getMillis());
+  }
+}

common/src/testing/java/google/registry/testing/FakeSleeper.java

@@ -0,0 +1,51 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.testing;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import google.registry.util.Sleeper;
+import java.io.Serializable;
+import javax.annotation.concurrent.ThreadSafe;
+import org.joda.time.ReadableDuration;
+
+/** Sleeper implementation for unit tests that advances {@link FakeClock} rather than sleep. */
+@ThreadSafe
+public final class FakeSleeper implements Sleeper, Serializable {
+
+  private static final long serialVersionUID = -8975804222581077291L;
+
+  private final FakeClock clock;
+
+  public FakeSleeper(FakeClock clock) {
+    this.clock = checkNotNull(clock, "clock");
+  }
+
+  @Override
+  public void sleep(ReadableDuration duration) throws InterruptedException {
+    checkArgument(duration.getMillis() >= 0);
+    if (Thread.interrupted()) {
+      throw new InterruptedException();
+    }
+    clock.advanceBy(duration);
+  }
+
+  @Override
+  public void sleepUninterruptibly(ReadableDuration duration) {
+    checkArgument(duration.getMillis() >= 0);
+    clock.advanceBy(duration);
+  }
+}

common/src/testing/java/google/registry/testing/SystemInfo.java

@@ -0,0 +1,64 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.testing;
+
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import com.google.common.flogger.FluentLogger;
+import java.io.IOException;
+import java.util.concurrent.ExecutionException;
+import javax.annotation.concurrent.ThreadSafe;
+
+/** Utility class for getting system information in tests. */
+@ThreadSafe
+public final class SystemInfo {
+
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private static final LoadingCache<String, Boolean> hasCommandCache =
+      CacheBuilder.newBuilder()
+          .build(
+              new CacheLoader<String, Boolean>() {
+                @Override
+                public Boolean load(String cmd) throws InterruptedException {
+                  try {
+                    Process pid = Runtime.getRuntime().exec(cmd);
+                    pid.getOutputStream().close();
+                    pid.waitFor();
+                  } catch (IOException e) {
+                    logger.atWarning().withCause(e).log("%s command not available", cmd);
+                    return false;
+                  }
+                  return true;
+                }
+              });
+
+  /**
+   * Returns {@code true} if system command can be run from path.
+   *
+   * <p><b>Warning:</b> The command is actually run! So there could be side-effects. You might
+   * need to specify a version flag or something. Return code is ignored.
+   *
+   * <p>This result is a memoized. If multiple therads try to get the same result at once, the
+   * heavy lifting will only be performed by the first thread and the rest will wait.
+   *
+   * @throws ExecutionException
+   */
+  public static boolean hasCommand(String cmd) throws ExecutionException {
+    return hasCommandCache.get(cmd);
+  }
+
+}