/*
   Copyright (C) 2015-2017 Pascal Gauthier.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA

   The code is based on ppplay https://github.com/stohrendorf/ppplay and opl3
   math documentation :
   https://github.com/gtaylormb/opl3_fpga/blob/master/docs/opl3math/opl3math.pdf

*/

#include "EngineMkI.h"
#define _USE_MATH_DEFINES
#include <cmath>
#include <cstdlib>

#include "sin.h"
#include "exp2.h"

#ifdef DEBUG
#include "time.h"
//#define MKIDEBUG
#endif

#ifdef _WIN32
#if _MSC_VER < 1800
FRAC_NUM log2(FRAC_NUM n)  {
  //return log(n) / log(2.0);
  return LOG_FUNC(n) / LOG_FUNC(2.0);
}
FRAC_NUM round(FRAC_NUM n) {
  return n < 0.0 ? ceil(n - 0.5) : floor(n + 0.5);
}
#endif
__declspec(align(16)) const int zeros[N] = {0};
#else
const int32_t __attribute__ ((aligned(16))) zeros[_N_] = {0};
#endif

static const uint16_t NEGATIVE_BIT = 0x8000;
static const uint16_t ENV_BITDEPTH = 14;

static const uint16_t SINLOG_BITDEPTH = 10;
static const uint16_t SINLOG_TABLESIZE = 1 << SINLOG_BITDEPTH;
static uint16_t sinLogTable[SINLOG_TABLESIZE];

static const uint16_t SINEXP_BITDEPTH = 10;
static const uint16_t SINEXP_TABLESIZE = 1 << SINEXP_BITDEPTH;
static uint16_t sinExpTable[SINEXP_TABLESIZE];

const uint16_t ENV_MAX = 1 << ENV_BITDEPTH;

static inline uint16_t sinLog(uint16_t phi) {
  const uint16_t SINLOG_TABLEFILTER = SINLOG_TABLESIZE - 1;
  const uint16_t index = (phi & SINLOG_TABLEFILTER);

  switch ( ( phi & (SINLOG_TABLESIZE * 3) ) ) {
    case 0:
      return sinLogTable[index];
    case SINLOG_TABLESIZE:
      return sinLogTable[index ^ SINLOG_TABLEFILTER];
    case SINLOG_TABLESIZE * 2 :
      return sinLogTable[index] | NEGATIVE_BIT;
    default:
      return sinLogTable[index ^ SINLOG_TABLEFILTER] | NEGATIVE_BIT;
  }
}

EngineMkI::EngineMkI() {
  float bitReso = SINLOG_TABLESIZE;

  for (int i = 0; i < SINLOG_TABLESIZE; i++) {
    //float x1 = sin(((0.5+i)/bitReso) * M_PI/2.0);
    float x1 = SIN_FUNC(((0.5 + i) / bitReso) * M_PI / 2.0);
    sinLogTable[i] = round(-1024 * log2(x1));
  }

  bitReso = SINEXP_TABLESIZE;
  for (int i = 0; i < SINEXP_TABLESIZE; i++) {
    float x1 = (pow(2, float(i) / bitReso) - 1) * 4096;
    sinExpTable[i] = round(x1);
  }

#ifdef MKIDEBUG
  char buffer[4096];
  int pos = 0;

  for (int i = 0; i < SINLOG_TABLESIZE; i++) {
    pos += sprintf(buffer + pos, "%d ", sinLogTable[i]);
    if ( pos > 90 ) {
      buffer[0] = 0;
      pos = 0;
    }
  }
  buffer[0] = 0;
  pos = 0;
  for (int i = 0; i < SINEXP_TABLESIZE; i++) {
    pos += sprintf(buffer + pos, "%d ", sinExpTable[i]);
    if ( pos > 90 ) {
      buffer[0] = 0;
      pos = 0;
    }
  }
#endif
}

inline int32_t mkiSin(int32_t phase, uint16_t env) {
  uint16_t expVal = sinLog(phase >> (22 - SINLOG_BITDEPTH)) + (env);
  //int16_t expValShow = expVal;

  const bool isSigned = expVal & NEGATIVE_BIT;
  expVal &= ~NEGATIVE_BIT;

  const uint16_t SINEXP_FILTER = 0x3FF;
  uint16_t result = 4096 + sinExpTable[( expVal & SINEXP_FILTER ) ^ SINEXP_FILTER];

  //uint16_t resultB4 = result;
  result >>= ( expVal >> 10 ); // exp

#ifdef MKIDEBUG
  if ( ( time(NULL) % 5 ) == 0 ) {
    if ( expValShow < 0 ) {
      expValShow = (expValShow + 0x7FFF) * -1;
    }
  }
#endif

  if ( isSigned )
    return (-result - 1) << 13;
  else
    return result << 13;
}

void EngineMkI::compute(int32_t *output, const int32_t *input,
                        int32_t phase0, int32_t freq,
                        int32_t gain1, int32_t gain2, bool add) {
  int32_t dgain = (gain2 - gain1 + (_N_ >> 1)) >> LG_N;
  int32_t gain = gain1;
  int32_t phase = phase0;
  const int32_t *adder = add ? output : zeros;

  for (int i = 0; i < _N_; i++) {
    gain += dgain;
    int32_t y = mkiSin((phase + input[i]), gain);
    output[i] = y + adder[i];
    phase += freq;
  }

}

void EngineMkI::compute_pure(int32_t *output, int32_t phase0, int32_t freq,
                             int32_t gain1, int32_t gain2, bool add) {
  int32_t dgain = (gain2 - gain1 + (_N_ >> 1)) >> LG_N;
  int32_t gain = gain1;
  int32_t phase = phase0;
  const int32_t *adder = add ? output : zeros;

  for (int i = 0; i < _N_; i++) {
    gain += dgain;
    int32_t y = mkiSin(phase , gain);
    output[i] = y + adder[i];
    phase += freq;
  }
}

void EngineMkI::compute_fb(int32_t *output, int32_t phase0, int32_t freq,
                           int32_t gain1, int32_t gain2,
                           int32_t *fb_buf, int fb_shift, bool add) {
  int32_t dgain = (gain2 - gain1 + (_N_ >> 1)) >> LG_N;
  int32_t gain = gain1;
  int32_t phase = phase0;
  const int32_t *adder = add ? output : zeros;
  int32_t y0 = fb_buf[0];
  int32_t y = fb_buf[1];

  for (int i = 0; i < _N_; i++) {
    gain += dgain;
    int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);
    y0 = y;
    y = mkiSin((phase + scaled_fb), gain);
    output[i] = y + adder[i];
    phase += freq;
  }

  fb_buf[0] = y0;
  fb_buf[1] = y;
}

// exclusively used for ALGO 6 with feedback
void EngineMkI::compute_fb2(int32_t *output, FmOpParams *parms, int32_t gain01, int32_t gain02, int32_t *fb_buf, int fb_shift) {
  int32_t dgain[2];
  int32_t gain[2];
  int32_t phase[2];
  int32_t y0 = fb_buf[0];
  int32_t y = fb_buf[1];

  phase[0] = parms[0].phase;
  phase[1] = parms[1].phase;

  parms[1].gain_out = (ENV_MAX - (parms[1].level_in >> (28 - ENV_BITDEPTH)));

  gain[0] = gain01;
  gain[1] = parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out;

  dgain[0] = (gain02 - gain01 + (_N_ >> 1)) >> LG_N;
  dgain[1] = (parms[1].gain_out - (parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out));

  for (int i = 0; i < _N_; i++) {
    int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);

    // op 0
    gain[0] += dgain[0];
    y0 = y;
    y = mkiSin(phase[0] + scaled_fb, gain[0]);
    phase[0] += parms[0].freq;

    // op 1
    gain[1] += dgain[1];
    y = mkiSin(phase[1] + y, gain[1]);
    phase[1] += parms[1].freq;

    output[i] = y;
  }
  fb_buf[0] = y0;
  fb_buf[1] = y;
}

// exclusively used for ALGO 4 with feedback
void EngineMkI::compute_fb3(int32_t *output, FmOpParams *parms, int32_t gain01, int32_t gain02, int32_t *fb_buf, int fb_shift) {
  int32_t dgain[3];
  int32_t gain[3];
  int32_t phase[3];
  int32_t y0 = fb_buf[0];
  int32_t y = fb_buf[1];

  phase[0] = parms[0].phase;
  phase[1] = parms[1].phase;
  phase[2] = parms[2].phase;

  parms[1].gain_out = (ENV_MAX - (parms[1].level_in >> (28 - ENV_BITDEPTH)));
  parms[2].gain_out = (ENV_MAX - (parms[2].level_in >> (28 - ENV_BITDEPTH)));

  gain[0] = gain01;
  gain[1] = parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out;
  gain[2] = parms[2].gain_out == 0 ? (ENV_MAX - 1) : parms[2].gain_out;

  dgain[0] = (gain02 - gain01 + (_N_ >> 1)) >> LG_N;
  dgain[1] = (parms[1].gain_out - (parms[1].gain_out == 0 ? (ENV_MAX - 1) : parms[1].gain_out));
  dgain[2] = (parms[2].gain_out - (parms[2].gain_out == 0 ? (ENV_MAX - 1) : parms[2].gain_out));


  for (int i = 0; i < _N_; i++) {
    int32_t scaled_fb = (y0 + y) >> (fb_shift + 1);

    // op 0
    gain[0] += dgain[0];
    y0 = y;
    y = mkiSin(phase[0] + scaled_fb, gain[0]);
    phase[0] += parms[0].freq;

    // op 1
    gain[1] += dgain[1];
    y = mkiSin(phase[1] + y, gain[1]);
    phase[1] += parms[1].freq;

    // op 2
    gain[2] += dgain[2];
    y = mkiSin(phase[2] + y, gain[2]);
    phase[2] += parms[2].freq;

    output[i] = y;
  }
  fb_buf[0] = y0;
  fb_buf[1] = y;
}

void EngineMkI::render(int32_t *output, FmOpParams *params, int algorithm, int32_t *fb_buf, int32_t feedback_shift) {
  const int kLevelThresh = ENV_MAX - 100;
  FmAlgorithm alg = algorithms[algorithm];
  bool has_contents[3] = { true, false, false };
  bool fb_on = feedback_shift < 16;

  switch (algorithm) {
    case 3 : case 5 :
      if ( fb_on )
        alg.ops[0] = 0xc4;
  }

  for (int op = 0; op < 6; op++) {
    int flags = alg.ops[op];
    bool add = (flags & OUT_BUS_ADD) != 0;
    FmOpParams &param = params[op];
    int inbus = (flags >> 4) & 3;
    int outbus = flags & 3;
    int32_t *outptr = (outbus == 0) ? output : buf_[outbus - 1].get();
    int32_t gain1 = param.gain_out == 0 ? (ENV_MAX - 1) : param.gain_out;
    int32_t gain2 = ENV_MAX - (param.level_in >> (28 - ENV_BITDEPTH));
    param.gain_out = gain2;

    if (gain1 <= kLevelThresh || gain2 <= kLevelThresh) {

      if (!has_contents[outbus]) {
        add = false;
      }

      if (inbus == 0 || !has_contents[inbus]) {
        // PG: this is my 'dirty' implementation of FB for 2 and 3 operators...
        if ((flags & 0xc0) == 0xc0 && fb_on) {
          switch ( algorithm ) {
            // three operator feedback, process exception for ALGO 4
            case 3 :
              compute_fb3(outptr, params, gain1, gain2, fb_buf, min((feedback_shift + 2), 16));
              params[1].phase += params[1].freq << LG_N; // hack, we already processed op-5 - op-4
              params[2].phase += params[2].freq << LG_N; // yuk yuk
              op += 2; // ignore the 2 other operators
              break;
            // two operator feedback, process exception for ALGO 6
            case 5 :
              compute_fb2(outptr, params, gain1, gain2, fb_buf, min((feedback_shift + 2), 16));
              params[1].phase += params[1].freq << LG_N;  // yuk, hack, we already processed op-5
              op++; // ignore next operator;
              break;
            default:
              // one operator feedback, normal proces
              compute_fb(outptr, param.phase, param.freq, gain1, gain2, fb_buf, feedback_shift, add);
              break;
          }
        } else {
          compute_pure(outptr, param.phase, param.freq, gain1, gain2, add);
        }
      } else {
        compute(outptr, buf_[inbus - 1].get(), param.phase, param.freq, gain1, gain2, add);
      }

      has_contents[outbus] = true;
    } else if (!add) {
      has_contents[outbus] = false;
    }
    param.phase += param.freq << LG_N;
  }
}