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// 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
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// KIND, either express or implied.  See the License for the
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using Org.Apache.REEF.Tang.Annotations;
using Org.Apache.REEF.Wake.Remote;
using System;
using System.Linq;

namespace Org.Apache.REEF.Network.Group.Pipelining
{
    /// <summary>
    /// The codec for PipelineMessage
    /// </summary>
    /// <typeparam name="T">The message type</typeparam>
    public sealed class PipelineMessageCodec<T> : ICodec<PipelineMessage<T>>
    {
        /// <summary>
        /// Creates new PipelineMessageCodec
        /// </summary>
        /// <param name="baseCodec">The codec for actual message in PipelineMessage</param>
        [Inject]
        private PipelineMessageCodec(ICodec<T> baseCodec)
        {
            BaseCodec = baseCodec;
        }

        /// <summary>Encodes the given object into a Byte Array</summary>
        /// <param name="obj"></param>
        /// <returns>a byte[] representation of the object</returns>
        public byte[] Encode(PipelineMessage<T> obj)
        {
            var baseCoding = BaseCodec.Encode(obj.Data);
            var result = new byte[baseCoding.Length + sizeof(bool)];
            Buffer.BlockCopy(baseCoding, 0, result, 0, baseCoding.Length);
            Buffer.BlockCopy(BitConverter.GetBytes(obj.IsLast), 0, result, baseCoding.Length, sizeof(bool));
            return result;
        }

        /// <summary>Decodes the given byte array into a PipelineMessage object</summary>
        /// <param name="data"></param>
        /// <returns>the decoded PipelineMessage object</returns>
        public PipelineMessage<T> Decode(byte[] data)
        {
            var message = BaseCodec.Decode(data.Take(data.Length - sizeof(bool)).ToArray());
            var isLast = BitConverter.ToBoolean(data, data.Length - sizeof(bool));
            return new PipelineMessage<T>(message, isLast);
        }
                
        /// <summary>
        /// Codec for actual message T
        /// </summary>
        public ICodec<T> BaseCodec { get; private set; }
    }
}