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>
    /// An <see cref="IndexDeletionPolicy"/> which keeps all index commits around, never
    /// deleting them. This class is a singleton and can be accessed by referencing
    /// <see cref="INSTANCE"/>.
    /// </summary>
    public sealed class NoDeletionPolicy : IndexDeletionPolicy
    {
        /// <summary>
        /// The single instance of this class. </summary>
        public static readonly IndexDeletionPolicy INSTANCE = new NoDeletionPolicy();

        private NoDeletionPolicy()
        {
            // keep private to avoid instantiation
        }

        public override void OnCommit<T>(IList<T> commits)
        {
        }

        public override void OnInit<T>(IList<T> commits)
        {
        }

        public override object Clone()
        {
            return this;
        }
    }
}