/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.solr.store.blockcache;

import java.math.BigDecimal;
import java.util.Map;

import org.apache.lucene.util.LuceneTestCase;
import org.apache.lucene.util.TestUtil;
import org.apache.solr.metrics.MetricsMap;
import org.apache.solr.metrics.SolrMetricManager;
import org.junit.Before;
import org.junit.Test;

public class BufferStoreTest extends LuceneTestCase {
  private final static int blockSize = 1024;

  private Metrics metrics;
  private MetricsMap metricsMap;

  private Store store;

  @Before
  public void setup() {
    metrics = new Metrics();
    SolrMetricManager metricManager = new SolrMetricManager();
    String registry = TestUtil.randomSimpleString(random(), 2, 10);
    String scope = TestUtil.randomSimpleString(random(), 2, 10);
    metrics.initializeMetrics(metricManager, registry, scope);
    metricsMap = (MetricsMap) metricManager.registry(registry).getMetrics().get("CACHE." + scope + ".hdfsBlockCache");
    BufferStore.initNewBuffer(blockSize, blockSize, metrics);
    store = BufferStore.instance(blockSize);
  }

  @Test
  public void testBufferTakePut() {
    byte[] b1 = store.takeBuffer(blockSize);

    assertGaugeMetricsChanged(false, false);

    byte[] b2 = store.takeBuffer(blockSize);
    byte[] b3 = store.takeBuffer(blockSize);

    assertRawMetricCounts(2, 0);
    assertGaugeMetricsChanged(true, false);

    store.putBuffer(b1);

    assertGaugeMetricsChanged(false, false);

    store.putBuffer(b2);
    store.putBuffer(b3);

    assertRawMetricCounts(0, 2);
    assertGaugeMetricsChanged(false, true);
  }

  private void assertRawMetricCounts(int allocated, int lost) {
    assertEquals("Buffer allocation count is wrong.", allocated,
        metrics.shardBuffercacheAllocate.get());
    assertEquals("Lost buffer count is wrong", lost,
        metrics.shardBuffercacheLost.get());
  }

  /**
   * Stateful method to verify whether the amount of buffers allocated and lost
   * since the last call has changed.
   *
   * @param allocated
   *          whether buffers should have been allocated since the last call
   * @param lost
   *          whether buffers should have been lost since the last call
   */
  private void assertGaugeMetricsChanged(boolean allocated, boolean lost) {
    Map<String,Object> stats = metricsMap.getValue();

    assertEquals("Buffer allocation metric not updating correctly.",
        allocated, isMetricPositive(stats, "buffercache.allocations"));
    assertEquals("Buffer lost metric not updating correctly.",
        lost, isMetricPositive(stats, "buffercache.lost"));
  }

  private boolean isMetricPositive(Map<String,Object> stats, String metric) {
    return new BigDecimal(stats.get(metric).toString()).compareTo(BigDecimal.ZERO) > 0;
  }

}