/* Copyright (c) 2006-2011 Skype Limited. All Rights Reserved
   Ported to C# by Logan Stromberg

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

   - Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

   - Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

   - Neither the name of Internet Society, IETF or IETF Trust, nor the
   names of specific contributors, may be used to endorse or promote
   products derived from this software without specific prior written
   permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

namespace Concentus.Silk
{
    using Concentus.Common;
    using Concentus.Common.CPlusPlus;
    using Concentus.Silk.Enums;
    using Concentus.Silk.Structs;
    using System.Diagnostics;

    internal static class GainQuantization
    {
        private static readonly int OFFSET = ((SilkConstants.MIN_QGAIN_DB * 128) / 6 + 16 * 128);
        private static readonly int SCALE_Q16 = ((65536 * (SilkConstants.N_LEVELS_QGAIN - 1)) / (((SilkConstants.MAX_QGAIN_DB - SilkConstants.MIN_QGAIN_DB) * 128) / 6));
        private static readonly int INV_SCALE_Q16 = ((65536 * (((SilkConstants.MAX_QGAIN_DB - SilkConstants.MIN_QGAIN_DB) * 128) / 6)) / (SilkConstants.N_LEVELS_QGAIN - 1));

        /// <summary>
        /// Gain scalar quantization with hysteresis, uniform on log scale
        /// </summary>
        /// <param name="ind">O    gain indices [MAX_NB_SUBFR]</param>
        /// <param name="gain_Q16">I/O  gains (quantized out) [MAX_NB_SUBFR]</param>
        /// <param name="prev_ind">I/O  last index in previous frame. [Porting note] original implementation passed this as an int8*</param>
        /// <param name="conditional">I    first gain is delta coded if 1</param>
        /// <param name="nb_subfr">I    number of subframes</param>
        internal static void silk_gains_quant(
            sbyte[] ind,
            int[] gain_Q16,
            BoxedValueSbyte prev_ind,
            int conditional,
            int nb_subfr)
        {
            int k, double_step_size_threshold;

            for (k = 0; k < nb_subfr; k++)
            {
                // Debug.WriteLine("2a 0x{0:x}", (uint)gain_Q16[k]);
                /* Convert to log scale, scale, floor() */
                ind[k] = (sbyte)(Inlines.silk_SMULWB(SCALE_Q16, Inlines.silk_lin2log(gain_Q16[k]) - OFFSET));

                /* Round towards previous quantized gain (hysteresis) */
                if (ind[k] < prev_ind.Val)
                {
                    ind[k]++;
                }

                ind[k] = (sbyte)(Inlines.silk_LIMIT_int(ind[k], 0, SilkConstants.N_LEVELS_QGAIN - 1));

                /* Compute delta indices and limit */
                if (k == 0 && conditional == 0)
                {
                    /* Full index */
                    ind[k] = (sbyte)(Inlines.silk_LIMIT_int(ind[k], prev_ind.Val + SilkConstants.MIN_DELTA_GAIN_QUANT, SilkConstants.N_LEVELS_QGAIN - 1));
                    prev_ind.Val = ind[k];
                }
                else
                {
                    /* Delta index */
                    ind[k] = (sbyte)(ind[k] - prev_ind.Val);

                    /* Double the quantization step size for large gain increases, so that the max gain level can be reached */
                    double_step_size_threshold = 2 * SilkConstants.MAX_DELTA_GAIN_QUANT - SilkConstants.N_LEVELS_QGAIN + prev_ind.Val;
                    if (ind[k] > double_step_size_threshold)
                    {
                        ind[k] = (sbyte)(double_step_size_threshold + Inlines.silk_RSHIFT(ind[k] - double_step_size_threshold + 1, 1));
                    }

                    ind[k] = (sbyte)(Inlines.silk_LIMIT_int(ind[k], SilkConstants.MIN_DELTA_GAIN_QUANT, SilkConstants.MAX_DELTA_GAIN_QUANT));

                    /* Accumulate deltas */
                    if (ind[k] > double_step_size_threshold)
                    {
                        prev_ind.Val += (sbyte)(Inlines.silk_LSHIFT(ind[k], 1) - double_step_size_threshold);
                    }
                    else
                    {
                        prev_ind.Val += ind[k];
                    }

                    /* Shift to make non-negative */
                    ind[k] -= SilkConstants.MIN_DELTA_GAIN_QUANT;
                    // Debug.WriteLine("2b 0x{0:x}", (uint)ind[k]);
                }

                /* Scale and convert to linear scale */
                gain_Q16[k] = Inlines.silk_log2lin(Inlines.silk_min_32(Inlines.silk_SMULWB(INV_SCALE_Q16, prev_ind.Val) + OFFSET, 3967)); /* 3967 = 31 in Q7 */
            }
        }

        /// <summary>
        /// Gains scalar dequantization, uniform on log scale
        /// </summary>
        /// <param name="gain_Q16">O    quantized gains [MAX_NB_SUBFR]</param>
        /// <param name="ind">I    gain indices [MAX_NB_SUBFR]</param>
        /// <param name="prev_ind">I/O  last index in previous frame [Porting note] original implementation passed this as an int8*</param>
        /// <param name="conditional">I    first gain is delta coded if 1</param>
        /// <param name="nb_subfr">I    number of subframes</param>
        internal static void silk_gains_dequant(
            int[] gain_Q16,
            sbyte[] ind,
            BoxedValueSbyte prev_ind,
            int conditional,
            int nb_subfr)
        {
            int k, ind_tmp, double_step_size_threshold;

            for (k = 0; k < nb_subfr; k++)
            {
                if (k == 0 && conditional == 0)
                {
                    /* Gain index is not allowed to go down more than 16 steps (~21.8 dB) */
                    prev_ind.Val = (sbyte)(Inlines.silk_max_int(ind[k], prev_ind.Val - 16));
                }
                else
                {
                    /* Delta index */
                    ind_tmp = ind[k] + SilkConstants.MIN_DELTA_GAIN_QUANT;

                    /* Accumulate deltas */
                    double_step_size_threshold = 2 * SilkConstants.MAX_DELTA_GAIN_QUANT - SilkConstants.N_LEVELS_QGAIN + prev_ind.Val;
                    if (ind_tmp > double_step_size_threshold)
                    {
                        prev_ind.Val += (sbyte)(Inlines.silk_LSHIFT(ind_tmp, 1) - double_step_size_threshold);
                    }
                    else
                    {
                        prev_ind.Val += (sbyte)(ind_tmp);
                    }
                }

                prev_ind.Val = (sbyte)(Inlines.silk_LIMIT_int(prev_ind.Val, 0, SilkConstants.N_LEVELS_QGAIN - 1));

                /* Scale and convert to linear scale */
                gain_Q16[k] = Inlines.silk_log2lin(Inlines.silk_min_32(Inlines.silk_SMULWB(INV_SCALE_Q16, prev_ind.Val) + OFFSET, 3967)); /* 3967 = 31 in Q7 */
            }
        }

        /// <summary>
        /// Compute unique identifier of gain indices vector
        /// </summary>
        /// <param name="ind">I    gain indices [MAX_NB_SUBFR]</param>
        /// <param name="nb_subfr">I    number of subframes</param>
        /// <returns>unique identifier of gains</returns>
        internal static int silk_gains_ID(sbyte[] ind, int nb_subfr)
        {
            int k;
            int gainsID;

            gainsID = 0;
            for (k = 0; k < nb_subfr; k++)
            {
                gainsID = Inlines.silk_ADD_LSHIFT32(ind[k], gainsID, 8);
            }

            return gainsID;
        }
    }
}
