/**
 * 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.hadoop.hbase.io.util;

import static org.junit.Assert.*;

import java.math.BigInteger;
import java.util.Arrays;
import java.util.Random;

import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.SmallTests;
import org.apache.hadoop.hbase.util.Bytes;
import org.junit.Before;
import org.junit.Test;
import org.junit.experimental.categories.Category;

/**
 * Tests LRUDictionary
 */
@Category(SmallTests.class)
public class TestLRUDictionary {
  LRUDictionary testee;

  @Before
  public void setUp() throws Exception {
    testee = new LRUDictionary();
    testee.init(Short.MAX_VALUE);
  }

  @Test
  public void TestContainsNothing() {
    assertTrue(isDictionaryEmpty(testee));
  }

  /**
   * Assert can't add empty array.
   */
  @Test
  public void testPassingEmptyArrayToFindEntry() {
    assertEquals(Dictionary.NOT_IN_DICTIONARY,
      testee.findEntry(HConstants.EMPTY_BYTE_ARRAY, 0, 0));
    assertEquals(Dictionary.NOT_IN_DICTIONARY,
      testee.addEntry(HConstants.EMPTY_BYTE_ARRAY, 0, 0));
  }

  @Test
  public void testPassingSameArrayToAddEntry() {
    // Add random predefined byte array, in this case a random byte array from
    // HConstants.  Assert that when we add, we get new index.  Thats how it
    // works.
    int len = HConstants.CATALOG_FAMILY.length;
    int index = testee.addEntry(HConstants.CATALOG_FAMILY, 0, len);
    assertFalse(index == testee.addEntry(HConstants.CATALOG_FAMILY, 0, len));
    assertFalse(index == testee.addEntry(HConstants.CATALOG_FAMILY, 0, len));
  }

  @Test
  public void testBasic() {
    Random rand = new Random();
    byte[] testBytes = new byte[10];
    rand.nextBytes(testBytes);

    // Verify that our randomly generated array doesn't exist in the dictionary
    assertEquals(testee.findEntry(testBytes, 0, testBytes.length), -1);

    // now since we looked up an entry, we should have added it to the
    // dictionary, so it isn't empty

    assertFalse(isDictionaryEmpty(testee));

    // Check if we can find it using findEntry
    short t = testee.findEntry(testBytes, 0, testBytes.length);

    // Making sure we do find what we're looking for
    assertTrue(t != -1);

    byte[] testBytesCopy = new byte[20];

    Bytes.putBytes(testBytesCopy, 10, testBytes, 0, testBytes.length);

    // copy byte arrays, make sure that we check that equal byte arrays are
    // equal without just checking the reference
    assertEquals(testee.findEntry(testBytesCopy, 10, testBytes.length), t);

    // make sure the entry retrieved is the same as the one put in
    assertTrue(Arrays.equals(testBytes, testee.getEntry(t)));

    testee.clear();

    // making sure clear clears the dictionary
    assertTrue(isDictionaryEmpty(testee));
  }

  @Test
  public void TestLRUPolicy(){
    //start by filling the dictionary up with byte arrays
    for (int i = 0; i < Short.MAX_VALUE; i++) {
      testee.findEntry((BigInteger.valueOf(i)).toByteArray(), 0,
          (BigInteger.valueOf(i)).toByteArray().length);
    }

    // check we have the first element added
    assertTrue(testee.findEntry(BigInteger.ZERO.toByteArray(), 0,
        BigInteger.ZERO.toByteArray().length) != -1);

    // check for an element we know isn't there
    assertTrue(testee.findEntry(BigInteger.valueOf(Integer.MAX_VALUE).toByteArray(), 0,
        BigInteger.valueOf(Integer.MAX_VALUE).toByteArray().length) == -1);

    // since we just checked for this element, it should be there now.
    assertTrue(testee.findEntry(BigInteger.valueOf(Integer.MAX_VALUE).toByteArray(), 0,
        BigInteger.valueOf(Integer.MAX_VALUE).toByteArray().length) != -1);

    // test eviction, that the least recently added or looked at element is
    // evicted.  We looked at ZERO so it should be in the dictionary still.
    assertTrue(testee.findEntry(BigInteger.ZERO.toByteArray(), 0,
      BigInteger.ZERO.toByteArray().length) != -1);
    // Now go from beyond 1 to the end.
    for(int i = 1; i < Short.MAX_VALUE; i++) {
      assertTrue(testee.findEntry(BigInteger.valueOf(i).toByteArray(), 0,
          BigInteger.valueOf(i).toByteArray().length) == -1);
    }

    // check we can find all of these.
    for (int i = 0; i < Short.MAX_VALUE; i++) {
      assertTrue(testee.findEntry(BigInteger.valueOf(i).toByteArray(), 0,
          BigInteger.valueOf(i).toByteArray().length) != -1);
    }
  }

  static private boolean isDictionaryEmpty(LRUDictionary dict) {
    try {
      dict.getEntry((short)0);
      return false;
    } catch (IndexOutOfBoundsException ioobe) {
      return true;
    }
  }
}
