using System.Collections.Generic;

namespace Lucene.Net.Index
{
    /*
     * 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.
     */

    /// <summary>
    /// This <see cref="IndexDeletionPolicy"/> implementation that
    /// keeps only the most recent commit and immediately removes
    /// all prior commits after a new commit is done.  This is
    /// the default deletion policy.
    /// </summary>

    public sealed class KeepOnlyLastCommitDeletionPolicy : IndexDeletionPolicy
    {
        /// <summary>
        /// Sole constructor. </summary>
        public KeepOnlyLastCommitDeletionPolicy()
        {
        }

        /// <summary>
        /// Deletes all commits except the most recent one.
        /// </summary>
        public override void OnInit<T>(IList<T> commits)
        {
            // Note that commits.size() should normally be 1:
            OnCommit(commits);
        }

        /// <summary>
        /// Deletes all commits except the most recent one.
        /// </summary>
        public override void OnCommit<T>(IList<T> commits)
        {
            // Note that commits.size() should normally be 2 (if not
            // called by onInit above):
            int size = commits.Count;
            for (int i = 0; i < size - 1; i++)
            {
                commits[i].Delete();
            }
        }
    }
}