/*
** Nofrendo (c) 1998-2000 Matthew Conte (matt@conte.com)
**
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of version 2 of the GNU Library General 
** Public License as published by the Free Software Foundation.
**
** 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 
** Library General Public License for more details.  To obtain a 
** copy of the GNU Library General Public License, write to the Free 
** Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Any permitted reproduction of these routines, in whole or in part,
** must bear this legend.
**
**
** mmc5_snd.c
**
** Nintendo MMC5 sound emulation
** $Id$
*/

#include <string.h>
#include "types.h"
#include "mmc5_snd.h"
#include "nes_apu.h"

/* TODO: encapsulate apu/mmc5 rectangle */

#define  APU_OVERSAMPLE
#define  APU_VOLUME_DECAY(x)  ((x) -= ((x) >> 7))


typedef struct mmc5dac_s
{
  int32 output;
  boolean enabled;
} mmc5dac_t;


/* look up table madness */
static int32 decay_lut[16];
static int vbl_lut[32];

/* various sound constants for sound emulation */
/* vblank length table used for rectangles, triangle, noise */
static const uint8 vbl_length[32] = {
  5, 127, 10, 1, 19, 2, 40, 3, 80, 4, 30, 5, 7, 6, 13, 7,
  6, 8, 12, 9, 24, 10, 48, 11, 96, 12, 36, 13, 8, 14, 16, 15
};

/* ratios of pos/neg pulse for rectangle waves
** 2/16 = 12.5%, 4/16 = 25%, 8/16 = 50%, 12/16 = 75% 
** (4-bit adder in rectangles, hence the 16)
*/
static const int duty_lut[4] = {
  2, 4, 8, 12
};


static int32 mmc5_incsize;
static uint8 mul[2];
static mmc5rectangle_t mmc5rect[2];
static mmc5dac_t mmc5dac;

#define  MMC5_RECTANGLE_OUTPUT   chan->output_vol
static int32
mmc5_rectangle (mmc5rectangle_t * chan)
{
  int32 output;

#ifdef APU_OVERSAMPLE
  int num_times;
  int32 total;
#endif /* APU_OVERSAMPLE */

  /* reg0: 0-3=volume, 4=envelope, 5=hold, 6-7=duty cycle
   ** reg1: 0-2=sweep shifts, 3=sweep inc/dec, 4-6=sweep length, 7=sweep on
   ** reg2: 8 bits of freq
   ** reg3: 0-2=high freq, 7-4=vbl length counter
   */

  APU_VOLUME_DECAY (chan->output_vol);

  if (FALSE == chan->enabled || 0 == chan->vbl_length)
    return MMC5_RECTANGLE_OUTPUT;

  /* vbl length counter */
  if (FALSE == chan->holdnote)
    chan->vbl_length--;

  /* envelope decay at a rate of (env_delay + 1) / 240 secs */
  chan->env_phase -= 4;         /* 240/60 */
  while (chan->env_phase < 0) {
    chan->env_phase += chan->env_delay;

    if (chan->holdnote)
      chan->env_vol = (chan->env_vol + 1) & 0x0F;
    else if (chan->env_vol < 0x0F)
      chan->env_vol++;
  }

  if (chan->freq < APU_TO_FIXED (4))
    return MMC5_RECTANGLE_OUTPUT;

  chan->phaseacc -= mmc5_incsize;       /* # of cycles per sample */
  if (chan->phaseacc >= 0)
    return MMC5_RECTANGLE_OUTPUT;

#ifdef APU_OVERSAMPLE
  num_times = total = 0;

  if (chan->fixed_envelope)
    output = chan->volume << 8; /* fixed volume */
  else
    output = (chan->env_vol ^ 0x0F) << 8;
#endif

  while (chan->phaseacc < 0) {
    chan->phaseacc += chan->freq;
    chan->adder = (chan->adder + 1) & 0x0F;

#ifdef APU_OVERSAMPLE
    if (chan->adder < chan->duty_flip)
      total += output;
    else
      total -= output;

    num_times++;
#endif
  }

#ifdef APU_OVERSAMPLE
  chan->output_vol = total / num_times;
#else
  if (chan->fixed_envelope)
    output = chan->volume << 8; /* fixed volume */
  else
    output = (chan->env_vol ^ 0x0F) << 8;

  if (0 == chan->adder)
    chan->output_vol = output;
  else if (chan->adder == chan->duty_flip)
    chan->output_vol = -output;
#endif

  return MMC5_RECTANGLE_OUTPUT;
}

static uint8
mmc5_read (uint32 address)
{
  uint32 retval;

  retval = (uint32) (mul[0] * mul[1]);

  switch (address) {
    case 0x5205:
      return (uint8) retval;

    case 0x5206:
      return (uint8) (retval >> 8);

    default:
      return 0xFF;
  }
}

/* mix vrcvi sound channels together */
static int32
mmc5_process (void)
{
  int32 accum;

  accum = mmc5_rectangle (&mmc5rect[0]);
  accum += mmc5_rectangle (&mmc5rect[1]);
  if (mmc5dac.enabled)
    accum += mmc5dac.output;

  return accum;
}

/* write to registers */
static void
mmc5_write (uint32 address, uint8 value)
{
  int chan;

  switch (address) {
      /* rectangles */
    case MMC5_WRA0:
    case MMC5_WRB0:
      chan = (address & 4) ? 1 : 0;
      mmc5rect[chan].regs[0] = value;

      mmc5rect[chan].volume = value & 0x0F;
      mmc5rect[chan].env_delay = decay_lut[value & 0x0F];
      mmc5rect[chan].holdnote = (value & 0x20) ? TRUE : FALSE;
      mmc5rect[chan].fixed_envelope = (value & 0x10) ? TRUE : FALSE;
      mmc5rect[chan].duty_flip = duty_lut[value >> 6];
      break;

    case MMC5_WRA1:
    case MMC5_WRB1:
      break;

    case MMC5_WRA2:
    case MMC5_WRB2:
      chan = (address & 4) ? 1 : 0;
      mmc5rect[chan].regs[2] = value;
      if (mmc5rect[chan].enabled)
        mmc5rect[chan].freq =
            APU_TO_FIXED ((((mmc5rect[chan].regs[3] & 7) << 8) + value) + 1);
      break;

    case MMC5_WRA3:
    case MMC5_WRB3:
      chan = (address & 4) ? 1 : 0;
      mmc5rect[chan].regs[3] = value;

      if (mmc5rect[chan].enabled) {
        mmc5rect[chan].vbl_length = vbl_lut[value >> 3];
        mmc5rect[chan].env_vol = 0;
        mmc5rect[chan].freq =
            APU_TO_FIXED ((((value & 7) << 8) + mmc5rect[chan].regs[2]) + 1);
        mmc5rect[chan].adder = 0;
      }
      break;

    case MMC5_SMASK:
      if (value & 0x01)
        mmc5rect[0].enabled = TRUE;
      else {
        mmc5rect[0].enabled = FALSE;
        mmc5rect[0].vbl_length = 0;
      }

      if (value & 0x02)
        mmc5rect[1].enabled = TRUE;
      else {
        mmc5rect[1].enabled = FALSE;
        mmc5rect[1].vbl_length = 0;
      }

      break;

    case 0x5010:
      if (value & 0x01)
        mmc5dac.enabled = TRUE;
      else
        mmc5dac.enabled = FALSE;
      break;

    case 0x5011:
      mmc5dac.output = (value ^ 0x80) << 8;
      break;

    case 0x5205:
      mul[0] = value;
      break;

    case 0x5206:
      mul[1] = value;
      break;

    default:
      break;
  }
}

/* reset state of vrcvi sound channels */
static void
mmc5_reset (void)
{
  int i;

  /* get the phase period from the apu */
  mmc5_incsize = apu_getcyclerate ();

  for (i = 0x5000; i < 0x5008; i++)
    mmc5_write (i, 0);

  mmc5_write (0x5010, 0);
  mmc5_write (0x5011, 0);
}

static void
mmc5_init (void)
{
  int i;
  int num_samples = apu_getcontext ()->num_samples;

  /* lut used for enveloping and frequency sweeps */
  for (i = 0; i < 16; i++)
    decay_lut[i] = num_samples * (i + 1);

  /* used for note length, based on vblanks and size of audio buffer */
  for (i = 0; i < 32; i++)
    vbl_lut[i] = vbl_length[i] * num_samples;
}

/* TODO: bleh */
static void
mmc5_shutdown (void)
{
}

static apu_memread mmc5_memread[] = {
  {0x5205, 0x5206, mmc5_read},
  {-1, -1, NULL}
};

static apu_memwrite mmc5_memwrite[] = {
  {0x5000, 0x5015, mmc5_write},
  {0x5205, 0x5206, mmc5_write},
  {-1, -1, NULL}
};

apuext_t mmc5_ext = {
  mmc5_init,
  mmc5_shutdown,
  mmc5_reset,
  mmc5_process,
  mmc5_memread,
  mmc5_memwrite
};

/*
** $Log$
** Revision 1.3  2008/03/25 15:56:11  slomo
** Patch by: Andreas Henriksson <andreas at fatal dot set>
** * gst/nsf/Makefile.am:
** * gst/nsf/dis6502.h:
** * gst/nsf/fds_snd.c:
** * gst/nsf/fds_snd.h:
** * gst/nsf/fmopl.c:
** * gst/nsf/fmopl.h:
** * gst/nsf/gstnsf.c:
** * gst/nsf/log.c:
** * gst/nsf/log.h:
** * gst/nsf/memguard.c:
** * gst/nsf/memguard.h:
** * gst/nsf/mmc5_snd.c:
** * gst/nsf/mmc5_snd.h:
** * gst/nsf/nes6502.c:
** * gst/nsf/nes6502.h:
** * gst/nsf/nes_apu.c:
** * gst/nsf/nes_apu.h:
** * gst/nsf/nsf.c:
** * gst/nsf/nsf.h:
** * gst/nsf/osd.h:
** * gst/nsf/types.h:
** * gst/nsf/vrc7_snd.c:
** * gst/nsf/vrc7_snd.h:
** * gst/nsf/vrcvisnd.c:
** * gst/nsf/vrcvisnd.h:
** Update our internal nosefart to nosefart-2.7-mls to fix segfaults
** on some files. Fixes bug #498237.
** Remove some // comments, fix some compiler warnings and use pow()
** instead of a slow, selfmade implementation.
**
** Revision 1.1  2003/04/08 20:53:01  ben
** Adding more files...
**
** Revision 1.6  2000/07/04 04:51:41  matt
** cleanups
**
** Revision 1.5  2000/07/03 02:18:53  matt
** much better external module exporting
**
** Revision 1.4  2000/06/28 22:03:51  matt
** fixed stupid oversight
**
** Revision 1.3  2000/06/20 20:46:58  matt
** minor cleanups
**
** Revision 1.2  2000/06/20 04:06:16  matt
** migrated external sound definition to apu module
**
** Revision 1.1  2000/06/20 00:06:47  matt
** initial revision
**
*/