/* 
 * 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.
 */

using System;

using Directory = Lucene.Net.Store.Directory;

namespace Lucene.Net.Index
{
	
	/// <summary> <p/>Expert: represents a single commit into an index as seen by the
	/// {@link IndexDeletionPolicy} or {@link IndexReader}.<p/>
	/// 
	/// <p/> Changes to the content of an index are made visible
	/// only after the writer who made that change commits by
	/// writing a new segments file
	/// (<code>segments_N</code>). This point in time, when the
	/// action of writing of a new segments file to the directory
	/// is completed, is an index commit.<p/>
	/// 
	/// <p/>Each index commit point has a unique segments file
	/// associated with it. The segments file associated with a
	/// later index commit point would have a larger N.<p/>
	/// 
	/// <p/><b>WARNING</b>: This API is a new and experimental and
	/// may suddenly change. <p/>
	/// </summary>
	
	public abstract class IndexCommit : IndexCommitPoint
	{
		
		/// <summary> Get the segments file (<code>segments_N</code>) associated 
		/// with this commit point.
		/// </summary>
		public abstract System.String GetSegmentsFileName();
		
		/// <summary> Returns all index files referenced by this commit point.</summary>
		public abstract System.Collections.Generic.ICollection<string> GetFileNames();
		
		/// <summary> Returns the {@link Directory} for the index.</summary>
		public abstract Directory GetDirectory();
		
		/// <summary> Delete this commit point.  This only applies when using
		/// the commit point in the context of IndexWriter's
		/// IndexDeletionPolicy.
		/// <p/>
		/// Upon calling this, the writer is notified that this commit 
		/// point should be deleted. 
		/// <p/>
		/// Decision that a commit-point should be deleted is taken by the {@link IndexDeletionPolicy} in effect
		/// and therefore this should only be called by its {@link IndexDeletionPolicy#onInit onInit()} or 
		/// {@link IndexDeletionPolicy#onCommit onCommit()} methods.
		/// </summary>
		public virtual void  Delete()
		{
			throw new System.NotSupportedException("This IndexCommit does not support this method.");
		}
		
		public virtual bool IsDeleted()
		{
			throw new System.NotSupportedException("This IndexCommit does not support this method.");
		}
		
		/// <summary> Returns true if this commit is an optimized index.</summary>
		public virtual bool IsOptimized()
		{
			throw new System.NotSupportedException("This IndexCommit does not support this method.");
		}
		
		/// <summary> Two IndexCommits are equal if both their Directory and versions are equal.</summary>
		public  override bool Equals(System.Object other)
		{
			if (other is IndexCommit)
			{
				IndexCommit otherCommit = (IndexCommit) other;
				return otherCommit.GetDirectory().Equals(GetDirectory()) && otherCommit.GetVersion() == GetVersion();
			}
			else
				return false;
		}
		
		public override int GetHashCode()
		{
			return GetDirectory().GetHashCode() + GetSegmentsFileName().GetHashCode();
		}
		
		/// <summary>Returns the version for this IndexCommit.  This is the
		/// same value that {@link IndexReader#getVersion} would
		/// return if it were opened on this commit. 
		/// </summary>
		public virtual long GetVersion()
		{
			throw new System.NotSupportedException("This IndexCommit does not support this method.");
		}
		
		/// <summary>Returns the generation (the _N in segments_N) for this
		/// IndexCommit 
		/// </summary>
		public virtual long GetGeneration()
		{
			throw new System.NotSupportedException("This IndexCommit does not support this method.");
		}
		
		/// <summary>Convenience method that returns the last modified time
		/// of the segments_N file corresponding to this index
		/// commit, equivalent to
		/// getDirectory().fileModified(getSegmentsFileName()). 
		/// </summary>
		public virtual long GetTimestamp()
		{
			return GetDirectory().FileModified(GetSegmentsFileName());
		}
		
		/// <summary>Returns userData, previously passed to {@link
		/// IndexWriter#Commit(Map)} for this commit.  Map is
		/// String -> String. 
		/// </summary>
        public virtual System.Collections.Generic.IDictionary<string, string> GetUserData()
		{
			throw new System.NotSupportedException("This IndexCommit does not support this method.");
		}
	}
}