/*
 * COPIED FROM APACHE LUCENE 4.7.2
 *
 * Git URL: git@github.com:apache/lucene.git, tag: releases/lucene-solr/4.7.2, path: lucene/core/src/java
 *
 * (see https://issues.apache.org/jira/browse/OAK-10786 for details)
 */

package org.apache.lucene.util.packed;

/*
 * 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.
 */


/**
 * Utility class to buffer a list of signed longs in memory. This class only
 * supports appending and is optimized for non-negative numbers with a uniform distribution over a fixed (limited) range
 *
 * @lucene.internal
 */
public final class AppendingPackedLongBuffer extends AbstractAppendingLongBuffer {

  /**{@link AppendingPackedLongBuffer}
   * @param initialPageCount        the initial number of pages
   * @param pageSize                the size of a single page
   * @param acceptableOverheadRatio an acceptable overhead ratio per value
   */
  public AppendingPackedLongBuffer(int initialPageCount, int pageSize, float acceptableOverheadRatio) {
    super(initialPageCount, pageSize, acceptableOverheadRatio);
  }

  /**
   * Create an {@link AppendingPackedLongBuffer} with initialPageCount=16,
   * pageSize=1024 and acceptableOverheadRatio={@link PackedInts#DEFAULT}
   */
  public AppendingPackedLongBuffer() {
    this(16, 1024, PackedInts.DEFAULT);
  }

  /**
   * Create an {@link AppendingPackedLongBuffer} with initialPageCount=16,
   * pageSize=1024
   */
  public AppendingPackedLongBuffer(float acceptableOverheadRatio) {
    this(16, 1024, acceptableOverheadRatio);
  }

  @Override
  long get(int block, int element) {
    if (block == valuesOff) {
      return pending[element];
    } else {
      return values[block].get(element);
    }
  }

  @Override
  int get(int block, int element, long[] arr, int off, int len) {
    if (block == valuesOff) {
      int sysCopyToRead = Math.min(len, pendingOff - element);
      System.arraycopy(pending, element, arr, off, sysCopyToRead);
      return sysCopyToRead;
    } else {
      /* packed block */
      return values[block].get(element, arr, off, len);
    }
  }

  @Override
  void packPendingValues() {
    // compute max delta
    long minValue = pending[0];
    long maxValue = pending[0];
    for (int i = 1; i < pendingOff; ++i) {
      minValue = Math.min(minValue, pending[i]);
      maxValue = Math.max(maxValue, pending[i]);
    }


    // build a new packed reader
    final int bitsRequired = minValue < 0 ? 64 : PackedInts.bitsRequired(maxValue);
    final PackedInts.Mutable mutable = PackedInts.getMutable(pendingOff, bitsRequired, acceptableOverheadRatio);
    for (int i = 0; i < pendingOff; ) {
      i += mutable.set(i, pending, i, pendingOff - i);
    }
    values[valuesOff] = mutable;

  }

}
