/*
    * Copyright (C) 2011 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.collect;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkPositionIndexes;
  import static com.google.common.collect.BoundType.CLOSED;
  
  import com.google.common.primitives.Ints;
  
  import javax.annotation.Nullable;
  
  /**
   * An immutable sorted multiset with one or more distinct elements.
   *
   * @author Louis Wasserman
   */
  @SuppressWarnings("serial") // uses writeReplace, not default serialization
  final class RegularImmutableSortedMultiset<E> extends ImmutableSortedMultiset<E> {
    private final transient RegularImmutableSortedSet<E> elementSet;
    private final transient int[] counts;
    private final transient long[] cumulativeCounts;
    private final transient int offset;
    private final transient int length;
  
    RegularImmutableSortedMultiset(
        RegularImmutableSortedSet<E> elementSet,
        int[] counts,
        long[] cumulativeCounts,
        int offset,
        int length) {
      this.elementSet = elementSet;
      this.counts = counts;
      this.cumulativeCounts = cumulativeCounts;
      this.offset = offset;
      this.length = length;
    }
  
    @Override
    Entry<E> getEntry(int index) {
      return Multisets.immutableEntry(
          elementSet.asList().get(index),
          counts[offset + index]);
    }
  
    @Override
    public Entry<E> firstEntry() {
      return getEntry(0);
    }
  
    @Override
    public Entry<E> lastEntry() {
      return getEntry(length - 1);
    }
  
    @Override
    public int count(@Nullable Object element) {
      int index = elementSet.indexOf(element);
      return (index == -1) ? 0 : counts[index + offset];
    }
  
    @Override
    public int size() {
      long size = cumulativeCounts[offset + length] - cumulativeCounts[offset];
      return Ints.saturatedCast(size);
    }
  
    @Override
    public ImmutableSortedSet<E> elementSet() {
      return elementSet;
    }
  
    @Override
    public ImmutableSortedMultiset<E> headMultiset(E upperBound, BoundType boundType) {
      return getSubMultiset(0, elementSet.headIndex(upperBound, checkNotNull(boundType) == CLOSED));
    }
  
    @Override
    public ImmutableSortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType) {
      return getSubMultiset(elementSet.tailIndex(lowerBound, checkNotNull(boundType) == CLOSED),
          length);
    }
  
    ImmutableSortedMultiset<E> getSubMultiset(int from, int to) {
      checkPositionIndexes(from, to, length);
      if (from == to) {
        return emptyMultiset(comparator());
     } else if (from == 0 && to == length) {
       return this;
     } else {
       RegularImmutableSortedSet<E> subElementSet =
           (RegularImmutableSortedSet<E>) elementSet.getSubSet(from, to);
       return new RegularImmutableSortedMultiset<E>(
           subElementSet, counts, cumulativeCounts, offset + from, to - from);
     }
   }
 
   @Override
   boolean isPartialView() {
     return offset > 0 || length < counts.length;
   }
 }