/****************************************************************************

  emu2149.c -- YM2149/AY-3-8910 emulator by Mitsutaka Okazaki 2001-2016

  2001 04-28 : Version 1.00beta -- 1st Beta Release.
  2001 08-14 : Version 1.10
  2001 10-03 : Version 1.11     -- Added PSG_set_quality().
  2002 03-02 : Version 1.12     -- Removed PSG_init & PSG_close.
  2002 10-13 : Version 1.14     -- Fixed the envelope unit.
  2003 09-19 : Version 1.15     -- Added PSG_setMask and PSG_toggleMask
  2004 01-11 : Version 1.16     -- Fixed the envelope problem where the envelope 
                                   frequency register is written before key-on.
  2015 12-13 : Version 1.17     -- Changed own integer types to C99 stdint.h types.
  2016 09-06 : Version 1.20     -- Support per-channel output.
  2021 09-29 : Version 1.30     -- Fix some envelope generator problems (issue #2).

  References:
    psg.vhd        -- 2000 written by Kazuhiro Tsujikawa.
    s_fme7.c       -- 1999,2000 written by Mamiya (NEZplug).
    ay8910.c       -- 1998-2001 Author unknown (MAME).
    MSX-Datapack   -- 1991 ASCII Corp.
    AY-3-8910 data sheet
    
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "emu2149.h"

static uint32_t voltbl[2][32] = {
  {0x00, 0x01, 0x01, 0x02, 0x02, 0x03, 0x03, 0x04, 0x05, 0x06, 0x07, 0x09,
   0x0B, 0x0D, 0x0F, 0x12,
   0x16, 0x1A, 0x1F, 0x25, 0x2D, 0x35, 0x3F, 0x4C, 0x5A, 0x6A, 0x7F, 0x97,
   0xB4, 0xD6, 0xFF, 0xFF},
  {0x00, 0x00, 0x03, 0x03, 0x04, 0x04, 0x06, 0x06, 0x09, 0x09, 0x0D, 0x0D,
   0x12, 0x12, 0x1D, 0x1D,
   0x22, 0x22, 0x37, 0x37, 0x4D, 0x4D, 0x62, 0x62, 0x82, 0x82, 0xA6, 0xA6,
   0xD0, 0xD0, 0xFF, 0xFF}
};

static uint8_t regmsk[16] = {
    0xff, 0x0f, 0xff, 0x0f, 0xff, 0x0f, 0x1f, 0x3f, 
    0x1f, 0x1f, 0x1f, 0xff, 0xff, 0x0f, 0xff, 0xff
};

#define GETA_BITS 24

static void
internal_refresh (PSG * psg)
{
  if (psg->quality)
  {
    psg->base_incr = 1 << GETA_BITS;
    psg->realstep = (uint32_t) ((1 << 31) / psg->rate);
    psg->psgstep = (uint32_t) ((1 << 31) / (psg->clk / 16));
    psg->psgtime = 0;
  }
  else
  {
    psg->base_incr =
      (uint32_t) ((double) psg->clk * (1 << GETA_BITS) / (16 * psg->rate));
  }
}

void
PSG_set_rate (PSG * psg, uint32_t r)
{
  psg->rate = r ? r : 44100;
  internal_refresh (psg);
}

void
PSG_set_quality (PSG * psg, uint32_t q)
{
  psg->quality = q;
  internal_refresh (psg);
}

PSG *
PSG_new (uint32_t c, uint32_t r)
{
  PSG *psg;

  psg = (PSG *) malloc (sizeof (PSG));
  if (psg == NULL)
    return NULL;

  PSG_setVolumeMode (psg, EMU2149_VOL_DEFAULT);
  psg->clk = c;
  psg->rate = r ? r : 44100;
  PSG_set_quality (psg, 0);

  return psg;
}

void
PSG_setVolumeMode (PSG * psg, int type)
{
  switch (type)
  {
  case 1:
    psg->voltbl = voltbl[EMU2149_VOL_YM2149];
    break;
  case 2:
    psg->voltbl = voltbl[EMU2149_VOL_AY_3_8910];
    break;
  default:
    psg->voltbl = voltbl[EMU2149_VOL_DEFAULT];
    break;
  }
}

uint32_t
PSG_setMask (PSG *psg, uint32_t mask)
{
  uint32_t ret = 0;
  if(psg)
  {
    ret = psg->mask;
    psg->mask = mask;
  }  
  return ret;
}

uint32_t
PSG_toggleMask (PSG *psg, uint32_t mask)
{
  uint32_t ret = 0;
  if(psg)
  {
    ret = psg->mask;
    psg->mask ^= mask;
  }
  return ret;
}

void
PSG_reset (PSG * psg)
{
  int i;

  psg->base_count = 0;

  for (i = 0; i < 3; i++)
  {
    psg->count[i] = 0x1000;
    psg->freq[i] = 0;
    psg->edge[i] = 0;
    psg->volume[i] = 0;
    psg->ch_out[i] = 0;
  }

  psg->mask = 0;

  for (i = 0; i < 16; i++)
    psg->reg[i] = 0;
  psg->adr = 0;

  psg->noise_seed = 0xffff;
  psg->noise_count = 0x40;
  psg->noise_freq = 0;

  psg->env_volume = 0;
  psg->env_ptr = 0;
  psg->env_freq = 0;
  psg->env_count = 0;
  psg->env_pause = 1;

  psg->out = 0;

}

void
PSG_delete (PSG * psg)
{
  free (psg);
}

uint8_t
PSG_readIO (PSG * psg)
{
  return (uint8_t) (psg->reg[psg->adr]);
}

uint8_t
PSG_readReg (PSG * psg, uint32_t reg)
{
  return (uint8_t) (psg->reg[reg & 0x1f]);

}

void
PSG_writeIO (PSG * psg, uint32_t adr, uint32_t val)
{
  if (adr & 1)
    PSG_writeReg (psg, psg->adr, val);
  else
    psg->adr = val & 0x1f;
}

static inline void
update_output (PSG * psg)
{

  int i, noise;
  uint32_t incr;

  psg->base_count += psg->base_incr;
  incr = (psg->base_count >> GETA_BITS);
  psg->base_count &= (1 << GETA_BITS) - 1;

  /* Envelope */
  psg->env_count += incr;
  while (psg->env_count>=0x10000)
  {
    if (!psg->env_pause)
    {
      if(psg->env_face)
        psg->env_ptr = (psg->env_ptr + 1) & 0x3f ; 
      else
        psg->env_ptr = (psg->env_ptr + 0x3f) & 0x3f;
    }

    if (psg->env_ptr & 0x20) /* if carry or borrow */
    {
      if (psg->env_continue)
      {
        if (psg->env_alternate^psg->env_hold) psg->env_face ^= 1;
        if (psg->env_hold) psg->env_pause = 1;
        psg->env_ptr = psg->env_face?0:0x1f;       
      }
      else
      {
        psg->env_pause = 1;
        psg->env_ptr = 0;
      }
    }

    psg->env_count -= psg->env_freq?psg->env_freq:1; /* env_freq 0 is the same as 1. */
  }

  /* Noise */
  psg->noise_count += incr;
  if (psg->noise_count & 0x40)
  {
    if (psg->noise_seed & 1)
      psg->noise_seed ^= 0x24000;
    psg->noise_seed >>= 1;
    psg->noise_count -= psg->noise_freq?psg->noise_freq:(1<<1);
  }
  noise = psg->noise_seed & 1;

  /* Tone */
  for (i = 0; i < 3; i++)
  {
    psg->count[i] += incr;
    if (psg->count[i] & 0x1000)
    {
      if (psg->freq[i] > 1)
      {
        psg->edge[i] = !psg->edge[i];
        psg->count[i] -= psg->freq[i];
      }
      else
      {
        psg->edge[i] = 1;
      }
    }

    if (psg->mask&PSG_MASK_CH(i))
      continue;

    if ((psg->tmask[i]||psg->edge[i]) && (psg->nmask[i]||noise))
    {
      if (!(psg->volume[i] & 32)) 
        psg->ch_out[i] += (psg->voltbl[psg->volume[i] & 31] << 4);
      else 
        psg->ch_out[i] += (psg->voltbl[psg->env_ptr] << 4);
    }

    psg->ch_out[i] >>= 1;

  }

}

static inline int16_t 
mix_output(PSG *psg) {
  return (int16_t)(psg->out = psg->ch_out[0] + psg->ch_out[1] + psg->ch_out[2]);
}

int16_t
PSG_calc (PSG * psg)
{
  if (!psg->quality) {
    update_output(psg);
    return mix_output(psg);
  }

  /* Simple rate converter */
  while (psg->realstep > psg->psgtime)
  {
    psg->psgtime += psg->psgstep;
    update_output(psg);
  }
  psg->psgtime = psg->psgtime - psg->realstep;

  return mix_output(psg);
}

void
PSG_writeReg (PSG * psg, uint32_t reg, uint32_t val)
{
  int c;

  if (reg > 15) return;

  val &= regmsk[reg];

  psg->reg[reg] = (uint8_t) (val & 0xff);
  switch (reg)
  {
  case 0:
  case 2:
  case 4:
  case 1:
  case 3:
  case 5:
    c = reg >> 1;
    psg->freq[c] = ((psg->reg[c * 2 + 1] & 15) << 8) + psg->reg[c * 2];
    break;

  case 6:
    psg->noise_freq = (val & 31) << 1;
    break;

  case 7:
    psg->tmask[0] = (val & 1);
    psg->tmask[1] = (val & 2);
    psg->tmask[2] = (val & 4);
    psg->nmask[0] = (val & 8);
    psg->nmask[1] = (val & 16);
    psg->nmask[2] = (val & 32);
    break;

  case 8:
  case 9:
  case 10:
    psg->volume[reg - 8] = val << 1;
    break;
 
  case 11:
  case 12:
    psg->env_freq = (psg->reg[12] << 8) + psg->reg[11];
    psg->env_count = 0x10000 - psg->env_freq;
    break;

  case 13:
    psg->env_continue = (val >> 3) & 1;
    psg->env_attack = (val >> 2) & 1;
    psg->env_alternate = (val >> 1) & 1;
    psg->env_hold = val & 1;
    psg->env_face = psg->env_attack;
    psg->env_pause = 0;
    psg->env_count = 0x10000 - psg->env_freq;
    psg->env_ptr = psg->env_face?0:0x1f;
    break;

  case 14:
  case 15:
  default:
    break;
  }

  return;
}