/*
 * Copyright 2016 LinkedIn Corp. 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.
 */

package com.github.ambry.store;

import com.github.ambry.utils.MockTime;
import com.github.ambry.utils.Throttler;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ThreadLocalRandom;
import org.junit.Test;

import static org.junit.Assert.*;


public class DiskIOSchedulerTest {
  /**
   * Test that the correct throttlers are used for different job types.
   * @throws Exception
   */
  @Test
  public void basicTest() throws Exception {
    final int numJobTypes = 5;
    Map<String, Throttler> throttlers = new HashMap<>();
    for (int i = 0; i < numJobTypes; i++) {
      String jobType = Integer.toString(i);
      throttlers.put(jobType, new MockThrottler());
    }
    DiskIOScheduler scheduler = new DiskIOScheduler(throttlers);

    // recognized job types
    for (int i = 0; i < numJobTypes; i++) {
      String jobType = Integer.toString(i);
      Long usedSinceLastCall = ThreadLocalRandom.current().nextLong(Long.MAX_VALUE);
      assertEquals("Unexpected i/o slice availability returned", Long.MAX_VALUE,
          scheduler.getSlice(jobType, "job", usedSinceLastCall));
      MockThrottler throttler = (MockThrottler) throttlers.get(jobType);
      assertTrue("maybeThrottle should have been called for this jobType", throttler.called);
      assertEquals("observed units passed to throttler not as expected", usedSinceLastCall, throttler.observedUnits,
          0.0);
    }
    for (Throttler throttler : throttlers.values()) {
      ((MockThrottler) throttler).reset();
    }

    // unrecognized job type
    String jobType = Integer.toString(numJobTypes);
    assertEquals("Unexpected i/o slice availability returned", Long.MAX_VALUE, scheduler.getSlice(jobType, "job", 0));
    for (Throttler throttler : throttlers.values()) {
      assertFalse("maybeThrottle should not have been called for this jobType", ((MockThrottler) throttler).called);
    }

    // closing scheduler
    scheduler.close();
    for (Throttler throttler : throttlers.values()) {
      assertTrue("Throttler should be closed.", ((MockThrottler) throttler).closed);
    }
  }

  /**
   * Test for correct behavior when a null throttler map is passed in.
   * @throws Exception
   */
  @Test
  public void nullThrottlersTest() throws Exception {
    DiskIOScheduler scheduler = new DiskIOScheduler(null);
    assertEquals("Unexpected i/o slice availability returned", Long.MAX_VALUE, scheduler.getSlice("jobType", "job", 0));
    scheduler.close();
  }

  /**
   * A mock of {@link Throttler} for testing purposes.
   */
  private static class MockThrottler extends Throttler {
    boolean called;
    boolean closed;
    double observedUnits;

    /**
     * Build a {@link MockThrottler}.
     */
    private MockThrottler() {
      super(0, 0, false, new MockTime());
      reset();
    }

    @Override
    public void maybeThrottle(double observed) {
      called = true;
      observedUnits = observed;
    }

    @Override
    public void close() {
      closed = true;
    }

    /**
     * Reset the testing related variables to their default values.
     */
    private void reset() {
      called = false;
      observedUnits = Double.MIN_VALUE;
      closed = false;
    }
  }
}