/*
    * Copyright (C) 2012 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.util.concurrent;
  
  import static java.lang.reflect.Modifier.isStatic;
  import static java.util.concurrent.TimeUnit.MICROSECONDS;
  import static java.util.concurrent.TimeUnit.MILLISECONDS;
  import static java.util.concurrent.TimeUnit.NANOSECONDS;
  import static java.util.concurrent.TimeUnit.SECONDS;
  
  import com.google.common.collect.ImmutableClassToInstanceMap;
  import com.google.common.collect.ImmutableSet;
  import com.google.common.collect.Lists;
  import com.google.common.testing.NullPointerTester;
  import com.google.common.testing.NullPointerTester.Visibility;
  import com.google.common.util.concurrent.RateLimiter.SleepingStopwatch;
  
  import junit.framework.TestCase;
  
  import org.easymock.EasyMock;
  import org.mockito.Mockito;
  
  import java.lang.reflect.Method;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Random;
  import java.util.concurrent.TimeUnit;
  
  /**
   * Tests for RateLimiter.
   *
   * @author Dimitris Andreou
   */
  public class RateLimiterTest extends TestCase {
    private static final double EPSILON = 1e-8;
  
    private final FakeStopwatch stopwatch = new FakeStopwatch();
  
    public void testSimple() {
      RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
      limiter.acquire(); // R0.00, since it's the first request
      limiter.acquire(); // R0.20
      limiter.acquire(); // R0.20
      assertEvents("R0.00", "R0.20", "R0.20");
    }
  
    public void testImmediateTryAcquire() {
      RateLimiter r = RateLimiter.create(1);
      assertTrue("Unable to acquire initial permit", r.tryAcquire());
      assertFalse("Capable of acquiring secondary permit", r.tryAcquire());
    }
  
    public void testSimpleRateUpdate() {
      RateLimiter limiter = RateLimiter.create(5.0, 5, SECONDS);
      assertEquals(5.0, limiter.getRate());
      limiter.setRate(10.0);
      assertEquals(10.0, limiter.getRate());
  
      try {
        limiter.setRate(0.0);
        fail();
      } catch (IllegalArgumentException expected) {}
      try {
        limiter.setRate(-10.0);
        fail();
      } catch (IllegalArgumentException expected) {}
    }
  
    public void testAcquireParameterValidation() {
      RateLimiter limiter = RateLimiter.create(999);
      try {
        limiter.acquire(0);
        fail();
      } catch (IllegalArgumentException expected) {
      }
      try {
        limiter.acquire(-1);
        fail();
      } catch (IllegalArgumentException expected) {
      }
      try {
        limiter.tryAcquire(0);
        fail();
      } catch (IllegalArgumentException expected) {
      }
     try {
       limiter.tryAcquire(-1);
       fail();
     } catch (IllegalArgumentException expected) {
     }
     try {
       limiter.tryAcquire(0, 1, SECONDS);
       fail();
     } catch (IllegalArgumentException expected) {
     }
     try {
       limiter.tryAcquire(-1, 1, SECONDS);
       fail();
     } catch (IllegalArgumentException expected) {
     }
   }
 
   public void testSimpleWithWait() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     limiter.acquire();          // R0.00
     stopwatch.sleepMillis(200);    // U0.20, we are ready for the next request...
     limiter.acquire();          // R0.00, ...which is granted immediately
     limiter.acquire();          // R0.20
     assertEvents("R0.00", "U0.20", "R0.00", "R0.20");
   }
 
   public void testSimpleAcquireReturnValues() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     assertEquals(0.0, limiter.acquire(), EPSILON);  // R0.00
     stopwatch.sleepMillis(200);                     // U0.20, we are ready for the next request...
     assertEquals(0.0, limiter.acquire(), EPSILON);  // R0.00, ...which is granted immediately
     assertEquals(0.2, limiter.acquire(), EPSILON);  // R0.20
     assertEvents("R0.00", "U0.20", "R0.00", "R0.20");
   }
 
   public void testSimpleAcquireEarliestAvailableIsInPast() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     assertEquals(0.0, limiter.acquire(), EPSILON);
     stopwatch.sleepMillis(400);
     assertEquals(0.0, limiter.acquire(), EPSILON);
     assertEquals(0.0, limiter.acquire(), EPSILON);
     assertEquals(0.2, limiter.acquire(), EPSILON);
   }
 
   public void testOneSecondBurst() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     stopwatch.sleepMillis(1000); // max capacity reached
     stopwatch.sleepMillis(1000); // this makes no difference
     limiter.acquire(1); // R0.00, since it's the first request
 
     limiter.acquire(1); // R0.00, from capacity
     limiter.acquire(3); // R0.00, from capacity
     limiter.acquire(1); // R0.00, concluding a burst of 5 permits
 
     limiter.acquire(); // R0.20, capacity exhausted
     assertEvents("U1.00", "U1.00",
         "R0.00", "R0.00", "R0.00", "R0.00", // first request and burst
         "R0.20");
   }
 
   public void testCreateWarmupParameterValidation() {
     RateLimiter.create(1.0, 1, NANOSECONDS);
     RateLimiter.create(1.0, 0, NANOSECONDS);
 
     try {
       RateLimiter.create(0.0, 1, NANOSECONDS);
       fail();
     } catch (IllegalArgumentException expected) {
     }
 
     try {
       RateLimiter.create(1.0, -1, NANOSECONDS);
       fail();
     } catch (IllegalArgumentException expected) {
     }
   }
 
   public void testWarmUp() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 2.0, 4000, MILLISECONDS);
     for (int i = 0; i < 8; i++) {
       limiter.acquire(); // #1
     }
     stopwatch.sleepMillis(500); // #2: to repay for the last acquire
     stopwatch.sleepMillis(4000); // #3: becomes cold again
     for (int i = 0; i < 8; i++) {
       limiter.acquire(); // // #4
     }
     stopwatch.sleepMillis(500); // #5: to repay for the last acquire
     stopwatch.sleepMillis(2000); // #6: didn't get cold! It would take another 2 seconds to go cold
     for (int i = 0; i < 8; i++) {
       limiter.acquire(); // #7
     }
     assertEvents(
         "R0.00, R1.38, R1.13, R0.88, R0.63, R0.50, R0.50, R0.50", // #1
         "U0.50", // #2
         "U4.00", // #3
         "R0.00, R1.38, R1.13, R0.88, R0.63, R0.50, R0.50, R0.50", // #4
         "U0.50", // #5
         "U2.00", // #6
         "R0.00, R0.50, R0.50, R0.50, R0.50, R0.50, R0.50, R0.50"); // #7
   }
 
   public void testWarmUpAndUpdate() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 2.0, 4000, MILLISECONDS);
     for (int i = 0; i < 8; i++) {
       limiter.acquire(); // // #1
     }
     stopwatch.sleepMillis(4500); // #2: back to cold state (warmup period + repay last acquire)
     for (int i = 0; i < 3; i++) { // only three steps, we're somewhere in the warmup period
       limiter.acquire(); // #3
     }
 
     limiter.setRate(4.0); // double the rate!
     limiter.acquire(); // #4, we repay the debt of the last acquire (imposed by the old rate)
     for (int i = 0; i < 4; i++) {
       limiter.acquire(); // #5
     }
     stopwatch.sleepMillis(4250); // #6, back to cold state (warmup period + repay last acquire)
     for (int i = 0; i < 11; i++) {
       limiter.acquire(); // #7, showing off the warmup starting from totally cold
     }
 
     // make sure the areas (times) remain the same, while permits are different
     assertEvents(
         "R0.00, R1.38, R1.13, R0.88, R0.63, R0.50, R0.50, R0.50", // #1
         "U4.50", // #2
         "R0.00, R1.38, R1.13", // #3, after that the rate changes
         "R0.88", // #4, this is what the throttling would be with the old rate
         "R0.34, R0.28, R0.25, R0.25", // #5
         "U4.25", // #6
         "R0.00, R0.72, R0.66, R0.59, R0.53, R0.47, R0.41", // #7
         "R0.34, R0.28, R0.25, R0.25"); // #7 (cont.), note, this matches #5
   }
 
   public void testBurstyAndUpdate() {
     RateLimiter rateLimiter = RateLimiter.create(stopwatch, 1.0);
     rateLimiter.acquire(1); // no wait
     rateLimiter.acquire(1); // R1.00, to repay previous
 
     rateLimiter.setRate(2.0); // update the rate!
 
     rateLimiter.acquire(1); // R1.00, to repay previous (the previous was under the old rate!)
     rateLimiter.acquire(2); // R0.50, to repay previous (now the rate takes effect)
     rateLimiter.acquire(4); // R1.00, to repay previous
     rateLimiter.acquire(1); // R2.00, to repay previous
     assertEvents("R0.00", "R1.00", "R1.00", "R0.50", "R1.00", "R2.00");
   }
 
   public void testTryAcquire_noWaitAllowed() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     assertTrue(limiter.tryAcquire(0, SECONDS));
     assertFalse(limiter.tryAcquire(0, SECONDS));
     assertFalse(limiter.tryAcquire(0, SECONDS));
     stopwatch.sleepMillis(100);
     assertFalse(limiter.tryAcquire(0, SECONDS));
   }
 
   public void testTryAcquire_someWaitAllowed() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     assertTrue(limiter.tryAcquire(0, SECONDS));
     assertTrue(limiter.tryAcquire(200, MILLISECONDS));
     assertFalse(limiter.tryAcquire(100, MILLISECONDS));
     stopwatch.sleepMillis(100);
     assertTrue(limiter.tryAcquire(100, MILLISECONDS));
   }
 
   public void testTryAcquire_overflow() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     assertTrue(limiter.tryAcquire(0, MICROSECONDS));
     stopwatch.sleepMillis(100);
     assertTrue(limiter.tryAcquire(Long.MAX_VALUE, MICROSECONDS));
   }
 
   public void testTryAcquire_negative() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 5.0);
     assertTrue(limiter.tryAcquire(5, 0, SECONDS));
     stopwatch.sleepMillis(900);
     assertFalse(limiter.tryAcquire(1, Long.MIN_VALUE, SECONDS));
     stopwatch.sleepMillis(100);
     assertTrue(limiter.tryAcquire(1, -1, SECONDS));
   }
 
   public void testSimpleWeights() {
     RateLimiter rateLimiter = RateLimiter.create(stopwatch, 1.0);
     rateLimiter.acquire(1); // no wait
     rateLimiter.acquire(1); // R1.00, to repay previous
     rateLimiter.acquire(2); // R1.00, to repay previous
     rateLimiter.acquire(4); // R2.00, to repay previous
     rateLimiter.acquire(8); // R4.00, to repay previous
     rateLimiter.acquire(1); // R8.00, to repay previous
     assertEvents("R0.00", "R1.00", "R1.00", "R2.00", "R4.00", "R8.00");
   }
 
   public void testInfinity_Bursty() {
     RateLimiter limiter = RateLimiter.create(stopwatch, Double.POSITIVE_INFINITY);
     limiter.acquire(Integer.MAX_VALUE / 4);
     limiter.acquire(Integer.MAX_VALUE / 2);
     limiter.acquire(Integer.MAX_VALUE);
     assertEvents("R0.00", "R0.00", "R0.00"); // no wait, infinite rate!
 
     limiter.setRate(2.0);
     limiter.acquire();
     limiter.acquire();
     limiter.acquire();
     limiter.acquire();
     limiter.acquire();
     assertEvents(
         "R0.00", // First comes the saved-up burst, which defaults to a 1-second burst (2 requests).
         "R0.00",
         "R0.00", // Now comes the free request.
         "R0.50", // Now it's 0.5 seconds per request.
         "R0.50");
 
     limiter.setRate(Double.POSITIVE_INFINITY);
     limiter.acquire();
     limiter.acquire();
     limiter.acquire();
     assertEvents("R0.50", "R0.00", "R0.00"); // we repay the last request (.5sec), then back to +oo
   }
 
   /** https://code.google.com/p/guava-libraries/issues/detail?id=1791 */
   public void testInfinity_BustyTimeElapsed() {
     RateLimiter limiter = RateLimiter.create(stopwatch, Double.POSITIVE_INFINITY);
     stopwatch.instant += 1000000;
     limiter.setRate(2.0);
     for (int i = 0; i < 5; i++) {
       limiter.acquire();
     }
     assertEvents(
         "R0.00", // First comes the saved-up burst, which defaults to a 1-second burst (2 requests).
         "R0.00",
         "R0.00", // Now comes the free request.
         "R0.50", // Now it's 0.5 seconds per request.
         "R0.50");
   }
 
   public void testInfinity_WarmUp() {
     RateLimiter limiter = RateLimiter.create(
         stopwatch, Double.POSITIVE_INFINITY, 10, SECONDS);
     limiter.acquire(Integer.MAX_VALUE / 4);
     limiter.acquire(Integer.MAX_VALUE / 2);
     limiter.acquire(Integer.MAX_VALUE);
     assertEvents("R0.00", "R0.00", "R0.00");
 
     limiter.setRate(1.0);
     limiter.acquire();
     limiter.acquire();
     limiter.acquire();
     assertEvents("R0.00", "R1.00", "R1.00");
 
     limiter.setRate(Double.POSITIVE_INFINITY);
     limiter.acquire();
     limiter.acquire();
     limiter.acquire();
     assertEvents("R1.00", "R0.00", "R0.00");
   }
 
   public void testInfinity_WarmUpTimeElapsed() {
     RateLimiter limiter = RateLimiter.create(stopwatch, Double.POSITIVE_INFINITY, 10, SECONDS);
     stopwatch.instant += 1000000;
     limiter.setRate(1.0);
     for (int i = 0; i < 5; i++) {
       limiter.acquire();
     }
     assertEvents("R0.00", "R1.00", "R1.00", "R1.00", "R1.00");
   }
 
   /**
    * Make sure that bursts can never go above 1-second-worth-of-work for the current
    * rate, even when we change the rate.
    */
   public void testWeNeverGetABurstMoreThanOneSec() {
     RateLimiter limiter = RateLimiter.create(stopwatch, 1.0);
     int[] rates = { 1000, 1, 10, 1000000, 10, 1};
     for (int rate : rates) {
       int oneSecWorthOfWork = rate;
       stopwatch.sleepMillis(rate * 1000);
       limiter.setRate(rate);
       long burst = measureTotalTimeMillis(limiter, oneSecWorthOfWork, new Random());
       // we allow one second worth of work to go in a burst (i.e. take less than a second)
       assertTrue(burst <= 1000);
       long afterBurst = measureTotalTimeMillis(limiter, oneSecWorthOfWork, new Random());
       // but work beyond that must take at least one second
       assertTrue(afterBurst >= 1000);
     }
   }
 
   /**
    * This neat test shows that no matter what weights we use in our requests, if we push X
    * amount of permits in a cool state, where X = rate * timeToCoolDown, and we have
    * specified a timeToWarmUp() period, it will cost as the prescribed amount of time. E.g.,
    * calling [acquire(5), acquire(1)] takes exactly the same time as
    * [acquire(2), acquire(3), acquire(1)].
    */
   public void testTimeToWarmUpIsHonouredEvenWithWeights() {
     Random random = new Random();
     int maxPermits = 10;
     double[] qpsToTest = { 4.0, 2.0, 1.0, 0.5, 0.1 };
     for (int trial = 0; trial < 100; trial++) {
       for (double qps : qpsToTest) {
         // Since we know that: maxPermits = 0.5 * warmup / stableInterval;
         // then if maxPermits == 10, we have:
         // warmupSeconds = 20 / qps
         long warmupMillis = (long) ((2 * maxPermits / qps) * 1000.0);
         RateLimiter rateLimiter = RateLimiter.create(
             stopwatch, qps, warmupMillis, MILLISECONDS);
         assertEquals(warmupMillis, measureTotalTimeMillis(rateLimiter, maxPermits, random));
       }
     }
   }
 
   public void testNulls() {
     NullPointerTester tester = new NullPointerTester()
         .setDefault(SleepingStopwatch.class, stopwatch)
         .setDefault(int.class, 1);
     tester.testStaticMethods(RateLimiter.class, Visibility.PACKAGE);
     tester.testInstanceMethods(RateLimiter.create(stopwatch, 5.0), Visibility.PACKAGE);
   }
 
   private long measureTotalTimeMillis(RateLimiter rateLimiter, int permits, Random random) {
     long startTime = stopwatch.instant;
     while (permits > 0) {
       int nextPermitsToAcquire = Math.max(1, random.nextInt(permits));
       permits -= nextPermitsToAcquire;
       rateLimiter.acquire(nextPermitsToAcquire);
     }
     rateLimiter.acquire(1); // to repay for any pending debt
     return NANOSECONDS.toMillis(stopwatch.instant - startTime);
   }
 
   private void assertEvents(String... events) {
     assertEquals(Arrays.toString(events), stopwatch.readEventsAndClear());
   }
 
   /**
    * The stopwatch gathers events and presents them as strings.
    * R0.6 means a delay of 0.6 seconds caused by the (R)ateLimiter
    * U1.0 means the (U)ser caused the stopwatch to sleep for a second.
    */
   static class FakeStopwatch extends SleepingStopwatch {
     long instant = 0L;
     final List<String> events = Lists.newArrayList();
 
     @Override
     public long readMicros() {
       return NANOSECONDS.toMicros(instant);
     }
 
     void sleepMillis(int millis) {
       sleepMicros("U", MILLISECONDS.toMicros(millis));
     }
 
     void sleepMicros(String caption, long micros) {
       instant += MICROSECONDS.toNanos(micros);
       events.add(caption + String.format("%3.2f", (micros / 1000000.0)));
     }
 
     @Override
     void sleepMicrosUninterruptibly(long micros) {
       sleepMicros("R", micros);
     }
 
     String readEventsAndClear() {
       try {
         return events.toString();
       } finally {
         events.clear();
       }
     }
 
     @Override
     public String toString() {
       return events.toString();
     }
   }
 
   public void testMocking() throws Exception {
     RateLimiter mockito = Mockito.mock(RateLimiter.class);
     RateLimiter easyMock = EasyMock.createNiceMock(RateLimiter.class);
     EasyMock.replay(easyMock);
     for (Method method : RateLimiter.class.getMethods()) {
       if (!isStatic(method.getModifiers())
           && !NOT_WORKING_ON_MOCKS.contains(method.getName())
           && !method.getDeclaringClass().equals(Object.class)) {
         method.invoke(mockito, arbitraryParameters(method));
         method.invoke(easyMock, arbitraryParameters(method));
       }
     }
   }
 
   private static Object[] arbitraryParameters(Method method) {
     Class<?>[] parameterTypes = method.getParameterTypes();
     Object[] params = new Object[parameterTypes.length];
     for (int i = 0; i < parameterTypes.length; i++) {
       params[i] = PARAMETER_VALUES.get(parameterTypes[i]);
     }
     return params;
   }
 
   private static final ImmutableSet<String> NOT_WORKING_ON_MOCKS =
       ImmutableSet.of("latestPermitAgeSec", "setRate");
 
   // We would use ArbitraryInstances, but it returns 0, invalid for many RateLimiter methods.
   private static final ImmutableClassToInstanceMap<Object> PARAMETER_VALUES =
       ImmutableClassToInstanceMap.builder()
           .put(int.class, 1)
           .put(long.class, 1L)
           .put(double.class, 1.0)
           .put(TimeUnit.class, SECONDS)
           .build();
 }