/*
 * 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 javax.annotation.Nullable;

import com.google.common.primitives.Ints;

/**
 * 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;
	}
}
