/*
    * Copyright (C) 2008 The Guava Authors
    *
    * 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.google.common.testing;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  
  import junit.framework.TestCase;
  
  import java.util.EnumSet;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  
  /**
   * Unit test for {@link FakeTicker}.
   *
   * @author Jige Yu
   */
  @GwtCompatible(emulated = true)
  public class FakeTickerTest extends TestCase {
  
    @GwtIncompatible("NullPointerTester")
    public void testNullPointerExceptions() {
      NullPointerTester tester = new NullPointerTester();
      tester.testAllPublicInstanceMethods(new FakeTicker());
    }
  
    public void testAdvance() {
      FakeTicker ticker = new FakeTicker();
      assertEquals(0, ticker.read());
      assertSame(ticker, ticker.advance(10));
      assertEquals(10, ticker.read());
      ticker.advance(1, TimeUnit.MILLISECONDS);
      assertEquals(1000010L, ticker.read());
    }
  
    public void testAutoIncrementStep_returnsSameInstance() {
      FakeTicker ticker = new FakeTicker();
      assertSame(ticker, ticker.setAutoIncrementStep(10, TimeUnit.NANOSECONDS));
    }
  
    public void testAutoIncrementStep_nanos() {
      FakeTicker ticker = new FakeTicker().setAutoIncrementStep(10, TimeUnit.NANOSECONDS);
      assertEquals(0, ticker.read());
      assertEquals(10, ticker.read());
      assertEquals(20, ticker.read());
    }
  
    public void testAutoIncrementStep_millis() {
      FakeTicker ticker = new FakeTicker().setAutoIncrementStep(1, TimeUnit.MILLISECONDS);
      assertEquals(0, ticker.read());
      assertEquals(1000000, ticker.read());
      assertEquals(2000000, ticker.read());
    }
  
    public void testAutoIncrementStep_seconds() {
      FakeTicker ticker = new FakeTicker().setAutoIncrementStep(3, TimeUnit.SECONDS);
      assertEquals(0, ticker.read());
      assertEquals(3000000000L, ticker.read());
      assertEquals(6000000000L, ticker.read());
    }
  
    public void testAutoIncrementStep_resetToZero() {
      FakeTicker ticker = new FakeTicker().setAutoIncrementStep(10, TimeUnit.NANOSECONDS);
      assertEquals(0, ticker.read());
      assertEquals(10, ticker.read());
      assertEquals(20, ticker.read());
  
      for (TimeUnit timeUnit : EnumSet.allOf(TimeUnit.class)) {
        ticker.setAutoIncrementStep(0, timeUnit);
        assertEquals(
            "Expected no auto-increment when setting autoIncrementStep to 0 " + timeUnit,
            30, ticker.read());
      }
    }
  
    public void testAutoIncrement_negative() {
      FakeTicker ticker = new FakeTicker();
      try {
        ticker.setAutoIncrementStep(-1, TimeUnit.NANOSECONDS);
        fail("Expected IllegalArgumentException");
      } catch (IllegalArgumentException expected) {
     }
   }
 
   @GwtIncompatible("concurrency")
 
   public void testConcurrentAdvance() throws Exception {
     final FakeTicker ticker = new FakeTicker();
 
     int numberOfThreads = 64;
     runConcurrentTest(numberOfThreads,
         new Callable<Void>() {
           @Override
           public Void call() throws Exception {
             // adds two nanoseconds to the ticker
             ticker.advance(1L);
             Thread.sleep(10);
             ticker.advance(1L);
             return null;
           }
         });
 
     assertEquals(numberOfThreads * 2, ticker.read());
   }
 
   @GwtIncompatible("concurrency")
 
   public void testConcurrentAutoIncrementStep() throws Exception {
     int incrementByNanos = 3;
     final FakeTicker ticker =
         new FakeTicker().setAutoIncrementStep(incrementByNanos, TimeUnit.NANOSECONDS);
 
     int numberOfThreads = 64;
     runConcurrentTest(numberOfThreads,
         new Callable<Void>() {
           @Override
           public Void call() throws Exception {
             ticker.read();
             return null;
           }
         });
 
     assertEquals(incrementByNanos * numberOfThreads, ticker.read());
   }
 
   /**
    * Runs {@code callable} concurrently {@code numberOfThreads} times.
    */
   @GwtIncompatible("concurrency")
   private void runConcurrentTest(int numberOfThreads, final Callable<Void> callable)
       throws Exception {
     ExecutorService executorService = Executors.newFixedThreadPool(numberOfThreads);
     final CountDownLatch startLatch = new CountDownLatch(numberOfThreads);
     final CountDownLatch doneLatch = new CountDownLatch(numberOfThreads);
     for (int i = numberOfThreads; i > 0; i--) {
       executorService.submit(new Callable<Void>() {
         @Override
         public Void call() throws Exception {
           startLatch.countDown();
           startLatch.await();
           callable.call();
           doneLatch.countDown();
           return null;
         }
       });
     }
     doneLatch.await();
   }
 }