/// Version 1.0.0
/// Last modified 24.5.2014
///
/// Copyright (C) 2014 Veli-Mikko Puupponen
///
/// Halyri-system is a prototype emergency call system. Its purpose is to
/// demonstrate the use of the advanced capabilities available in the current
/// generation smartphones in facilitating the emergency service dispatcher's
/// capability to determine the nature of the emergency and to dispatch help.
///
/// For more information, see the README file of this package.
///
/// The MIT License (MIT)
///
/// Permission is hereby granted, free of charge, to any person obtaining a copy
/// of this software and associated documentation files (the "Software"), to
/// deal in the Software without restriction, including without limitation the
/// rights to use, copy, modify, merge, publish, distribute, sublicense,
/// and/or sell copies of the Software, and to permit persons to whom the
/// Software is furnished to do so, subject to the following conditions:
///
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
///
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
/// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
/// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
/// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
/// IN THE SOFTWARE.
///

using System;
using NSpeex;

namespace Hake_WPF.AudioVideoManagers
{
    /// <author>Veli-Mikko Puupponen</author>
    /// <summary>
    /// The class provides static methods for compression and decompression of
    /// speex encoded audio segments.
    /// </summary>
    class SpeexCompression
    {
        /// <summary>
        /// The function decompresses the provided MediaPackets of payload data using the 
        /// provided SpeexDecoder.It returns the resulting PCM samples in a byte array.
        /// 
        /// The SpeexDecodes is assumed to operate in the BandMode.Wide and the
        /// encoded data to conform to this format.
        /// 
        /// If the decompression fails, it returns an empty array.
        /// </summary>
        /// <param name="decoder">SpeexDecodes instance used to decode the speex encoding.</param>
        /// <param name="data">Speex encoded audio.</param>
        /// <param name="originatingLength">The count of 16 bit PCM samples that were 
        /// encoded to produce the provided encoded data.</param>
        /// <returns>The resulting PCM samples or an empty array.</returns>
        public static byte[] DecompressSpeex(SpeexDecoder decoder, byte[] data, int originatingLength) 
        {
            if (decoder == null || data == null)
                return new byte[0];
            short[] decodedData = new short[originatingLength];
            try
            {
                decoder.Decode(data, 0, data.Length, decodedData, 0, false);
            }
            catch (Exception) //TODO could be more specific, would need checking NSpeex code
            {
                return new byte[0];
            }
            byte[] decodedBytes = new byte[decodedData.Length * 2];
            int byteIndex = 0;
            for (int i = 0; i < decodedData.Length; i++, byteIndex += 2)
            {
                byte[] bytes = BitConverter.GetBytes(decodedData[i]);
                decodedBytes[byteIndex] = bytes[0];
                decodedBytes[byteIndex + 1] = bytes[1];
            }
            return decodedBytes;
        }

        /// <summary>
        /// The function encodes the provided PCM samples using the provided SpeexEncoder.
        /// The resulting encoded bytes are put into the compressed array.
        /// It returns the count of 16 bit samples that was used as the input of the
        /// speex encoder.
        /// 
        /// If the count of the PCM samples is not a multiple of 320, the differece 
        /// is padded with silence after the samples.
        /// 
        /// The SpeexEncoder is assumed to be operating in the BandMode.Wide and
        /// sampleSizeBytes is assumed to be 2, i.e. 16bit PCM.
        /// </summary>
        /// <param name="pcmSegment">16Bit PCM samples to be encode into speex</param>
        /// <param name="sampleSizeBytes">The size of the PCM samples in bytes, it should be 2.</param>
        /// <param name="encoder">SpeexEncoder used to encode the data</param>
        /// <param name="compressed">The target array for the resulting speex encoded audio.</param>
        /// <returns>The count of 16Bit PCM samples compressed.</returns>
        public static int CompressSpeex(byte[] pcmSegment, int pcmByteCount, int sampleSizeBytes, SpeexEncoder encoder, out byte[] compressed)
        {
            compressed = new byte[0];
            if (pcmSegment == null || pcmByteCount == 0 || encoder == null)
                return 0;
            int audioDataLength = pcmByteCount / sampleSizeBytes;
            int remainsFromCompletePackets = audioDataLength % encoder.FrameSize;
            short[] compressibleData;
            if (remainsFromCompletePackets == 0)
                compressibleData = new short[audioDataLength];
            else
                compressibleData = new short[(audioDataLength - remainsFromCompletePackets) + encoder.FrameSize];
            int compressibleDataIndex = 0;
            for (int i = 0; i < pcmByteCount; i += 2, compressibleDataIndex++)
                compressibleData[compressibleDataIndex] = BitConverter.ToInt16(pcmSegment, i);
            byte[] compressedData = new byte[pcmByteCount];
            int actualCompressedByteCount = 0;
            try
            {
                actualCompressedByteCount = encoder.Encode(compressibleData, 0, compressibleData.Length,
                    compressedData, 0, compressibleData.Length);
            }
            catch (Exception) //TODO could be more specific, would need checking NSpeex code
            {
                return 0;
            }
            if (actualCompressedByteCount > 0)
            {
                compressed = new byte[actualCompressedByteCount];
                Array.Copy(compressedData, 0, compressed, 0, compressed.Length);
            }
            return compressibleData.Length;
        }
    }
}