using Lucene.Net.Support;
using System;

namespace Lucene.Net.Store
{
    /*
     * 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>
    /// Simple implementation of <see cref="ChecksumIndexInput"/> that wraps
    /// another input and delegates calls.
    /// </summary>
    public class BufferedChecksumIndexInput : ChecksumIndexInput
    {
        internal readonly IndexInput main;
        internal readonly IChecksum digest;

        /// <summary>
        /// Creates a new <see cref="BufferedChecksumIndexInput"/> </summary>
        public BufferedChecksumIndexInput(IndexInput main)
            : base("BufferedChecksumIndexInput(" + main + ")")
        {
            this.main = main;
            this.digest = new BufferedChecksum(new CRC32());
        }

        public override byte ReadByte()
        {
            byte b = main.ReadByte();
            digest.Update(b);
            return b;
        }

        public override void ReadBytes(byte[] b, int offset, int len)
        {
            main.ReadBytes(b, offset, len);
            digest.Update(b, offset, len);
        }

        public override long Checksum => digest.Value;

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                main.Dispose();
            }
        }

        public override long GetFilePointer()
        {
            return main.GetFilePointer();
        }

        public override long Length => main.Length;

        public override object Clone()
        {
            throw new NotSupportedException();
        }
    }
}