//---------------------------------------------------------------------------
// NEOPOP : Emulator as in Dreamland
//
// Copyright (c) 2001-2002 by neopop_uk
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
//	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 2 of the License, or
//	(at your option) any later version. See also the license.txt file for
//	additional informations.
//---------------------------------------------------------------------------

/*
//---------------------------------------------------------------------------
//=========================================================================

	sound.c

//=========================================================================
//---------------------------------------------------------------------------

  History of changes:
  ===================

20 JUL 2002 - neopop_uk
=======================================
- Cleaned and tidied up for the source release

28 JUL 2002 - neopop_uk
=======================================
- Added clearer explanation of sound volume when debugging.

31 JUL 2002 - neopop_uk
=======================================
- Converted sound buffer to use unsigned data.

01 AUG 2002 - neopop_uk
=======================================
- Even with frameskipping, sound still gets choppy. I've removed
	the "optimisation" that I copied from MAME, 
	and didn't really understand.

03 AUG 2002 - neopop_uk
=======================================
- Add dac_update to fill the dac buffer.
- Removed the dac freq-dup as the O/S will mix the speeds.
- Improved mono mixing to match stereo volume.
- Converted DAC to mono, it never gets used in stereo.

03 AUG 2002 - neopop_uk
=======================================
- Increased the DAC buffer size, "Puyo Pop" was causing an overflow.
- DAC writes are ignored when mute is enabled.

09 AUG 2002 - neopop_uk
=======================================
- Mono chip mixing is now fake, the sound buffer is always stereo.
- Fixed & optimised dac_update if data buffer runs out during sound update.

16 AUG 2002 - neopop_uk
=======================================
- Fixed the sound chips so one is for noises, and the the other for tones.
	This sounds correct (verified from Sonic Adventure MP3 file I have).
- Removed stereo option.

//---------------------------------------------------------------------------
*/

/************************************************************************
 *                                                                      *
 *	Portions, but not all of this source file are based on MAME v0.60	*
 *	File "sn76496.c". All copyright goes to the original author.		*
 *	The remaining parts, including DAC processing, by neopop_uk			*
 *                                                                      *
 ************************************************************************/

#include "neopop.h"
#include "mem.h"
#include "sound.h"

//=============================================================================

BOOL mute;

SoundChip toneChip;
SoundChip noiseChip;

//==== DAC
#define DAC_BUFFERSIZE		256 * 1024

int dacBufferRead, dacBufferWrite, dacBufferCount;
_u8 dacBufferL[DAC_BUFFERSIZE];

//=============================================================================

#define SOUNDCHIPCLOCK	(3072000)	//Unverified / sounds correct

#define MAX_OUTPUT 0x7fff
#define STEP 0x10000		//Fixed point adjuster

static _u32 VolTable[16];
static _u32 UpdateStep;	//Number of steps during one sample.

/* Formulas for noise generator */
/* bit0 = output */

/* noise feedback for white noise mode (verified on real SN76489 by John Kortink) */
#define FB_WNOISE 0x14002	/* (16bits) bit16 = bit0(out) ^ bit2 ^ bit15 */

/* noise feedback for periodic noise mode */
#define FB_PNOISE 0x08000	/* 15bit rotate */

/* noise generator start preset (for periodic noise) */
#define NG_PRESET 0x0f35

//=============================================================================

static _u16 sample_chip_tone(void)
{
//	int i;
//
//	int vol[4];
//	unsigned int out;
//	int left;
//
//	/* vol[] keeps track of how long each square wave stays */
//	/* in the 1 position during the sample period. */
//	vol[0] = vol[1] = vol[2] = vol[3] = 0;
//
//	for (i = 0; i < 3; i++)
//	{
//		if (toneChip.Output[i]) vol[i] += toneChip.Count[i];
//		toneChip.Count[i] -= STEP;
//
//		/* Period[i] is the half period of the square wave. Here, in each */
//		/* loop I add Period[i] twice, so that at the end of the loop the */
//		/* square wave is in the same status (0 or 1) it was at the start. */
//		/* vol[i] is also incremented by Period[i], since the wave has been 1 */
//		/* exactly half of the time, regardless of the initial position. */
//		/* If we exit the loop in the middle, Output[i] has to be inverted */
//		/* and vol[i] incremented only if the exit status of the square */
//		/* wave is 1. */
//
//		while (toneChip.Count[i] <= 0)
//		{
//			toneChip.Count[i] += toneChip.Period[i];
//			if (toneChip.Count[i] > 0)
//			{
//				toneChip.Output[i] ^= 1;
//				if (toneChip.Output[i]) vol[i] += toneChip.Period[i];
//				break;
//			}
//			toneChip.Count[i] += toneChip.Period[i];
//			vol[i] += toneChip.Period[i];
//		}
//		if (toneChip.Output[i]) vol[i] -= toneChip.Count[i];
//	}
//
//	left = STEP;
//	do
//	{
//		int nextevent;
//
//		if (toneChip.Count[3] < left) nextevent = toneChip.Count[3];
//		else nextevent = left;
//
//		if (toneChip.Output[3]) vol[3] += toneChip.Count[3];
//		toneChip.Count[3] -= nextevent;
//		if (toneChip.Count[3] <= 0)
//		{
//			if (toneChip.RNG & 1) toneChip.RNG ^= toneChip.NoiseFB;
//			toneChip.RNG >>= 1;
//			toneChip.Output[3] = toneChip.RNG & 1;
//			toneChip.Count[3] += toneChip.Period[3];
//			if (toneChip.Output[3]) vol[3] += toneChip.Period[3];
//		}
//		if (toneChip.Output[3]) vol[3] -= toneChip.Count[3];
//
//		left -= nextevent;
//	} while (left > 0);
//
//
//	out = vol[0] * toneChip.Volume[0] + vol[1] * toneChip.Volume[1] +
//		vol[2] * toneChip.Volume[2];
//
//	if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP;
//
//	return out / STEP;
}

//=============================================================================

static _u16 sample_chip_noise(void)
{
//	int i;
//
//	int vol[4];
//	unsigned int out;
//	int left;
//
//	/* vol[] keeps track of how long each square wave stays */
//	/* in the 1 position during the sample period. */
//	vol[0] = vol[1] = vol[2] = vol[3] = 0;
//
//	for (i = 0; i < 3; i++)
//	{
//		if (noiseChip.Output[i]) vol[i] += noiseChip.Count[i];
//		noiseChip.Count[i] -= STEP;
//
//		/* Period[i] is the half period of the square wave. Here, in each */
//		/* loop I add Period[i] twice, so that at the end of the loop the */
//		/* square wave is in the same status (0 or 1) it was at the start. */
//		/* vol[i] is also incremented by Period[i], since the wave has been 1 */
//		/* exactly half of the time, regardless of the initial position. */
//		/* If we exit the loop in the middle, Output[i] has to be inverted */
//		/* and vol[i] incremented only if the exit status of the square */
//		/* wave is 1. */
//
//		while (noiseChip.Count[i] <= 0)
//		{
//			noiseChip.Count[i] += noiseChip.Period[i];
//			if (noiseChip.Count[i] > 0)
//			{
//				noiseChip.Output[i] ^= 1;
//				if (noiseChip.Output[i]) vol[i] += noiseChip.Period[i];
//				break;
//			}
//			noiseChip.Count[i] += noiseChip.Period[i];
//			vol[i] += noiseChip.Period[i];
//		}
//		if (noiseChip.Output[i]) vol[i] -= noiseChip.Count[i];
//	}
//
//	left = STEP;
//	do
//	{
//		int nextevent;
//
//		if (noiseChip.Count[3] < left) nextevent = noiseChip.Count[3];
//		else nextevent = left;
//
//		if (noiseChip.Output[3]) vol[3] += noiseChip.Count[3];
//		noiseChip.Count[3] -= nextevent;
//		if (noiseChip.Count[3] <= 0)
//		{
//			if (noiseChip.RNG & 1) noiseChip.RNG ^= noiseChip.NoiseFB;
//			noiseChip.RNG >>= 1;
//			noiseChip.Output[3] = noiseChip.RNG & 1;
//			noiseChip.Count[3] += noiseChip.Period[3];
//			if (noiseChip.Output[3]) vol[3] += noiseChip.Period[3];
//		}
//		if (noiseChip.Output[3]) vol[3] -= noiseChip.Count[3];
//
//		left -= nextevent;
//	} while (left > 0);
//
//
//	out = vol[3] * noiseChip.Volume[3];
//
//	if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP;
//
//	return out / STEP;
}

//=============================================================================

void sound_update(_u16* chip_buffer, int length_bytes)
{
  //MY REM!!!
//	while (length_bytes > 0)
//	{
//		//Mix a mono track out of: (Tone + Noise) >> 1
//		//Write it to the sound buffer
//		*(chip_buffer++) = (sample_chip_tone() + sample_chip_noise()) >> 1;
//
//		length_bytes -= 2;	// 2 bytes = 16 bits
//	}
}

//=============================================================================

void WriteSoundChip(SoundChip* chip, _u8 data)
{
//	//Command
//	if (data & 0x80)
//	{
//		int r = (data & 0x70) >> 4;
//		int c = r/2;
//
//		chip->LastRegister = r;
//		chip->Register[r] = (chip->Register[r] & 0x3f0) | (data & 0x0f);
//	
//		switch(r)
//		{
//		case 0:	/* tone 0 : frequency */
//		case 2:	/* tone 1 : frequency */
//		case 4:	/* tone 2 : frequency */
//			chip->Period[c] = UpdateStep * chip->Register[r];
//			if (chip->Period[c] == 0) chip->Period[c] = UpdateStep;
//			if (r == 4)
//			{
//				/* update noise shift frequency */
//				if ((chip->Register[6] & 0x03) == 0x03)
//					chip->Period[3] = 2 * chip->Period[2];
//			}
//			break;
//
//		case 1:	/* tone 0 : volume */
//		case 3:	/* tone 1 : volume */
//		case 5:	/* tone 2 : volume */
//		case 7:	/* noise  : volume */
//#ifdef NEOPOP_DEBUG
//			if (filter_sound)
//			{
//				if (chip == &toneChip)
//					system_debug_message("sound (T): Set Tone %d Volume to %d (0 = min, 15 = max)", c, 15 - (data & 0xF));
//				else
//					system_debug_message("sound (N): Set Tone %d Volume to %d (0 = min, 15 = max)", c, 15 - (data & 0xF));
//			}
//#endif
//			chip->Volume[c] = VolTable[data & 0xF];
//			break;
//
//		case 6:	/* noise  : frequency, mode */
//			{
//				int n = chip->Register[6];
//#ifdef NEOPOP_DEBUG
//	if (filter_sound)
//	{
//		char *pm, *nm = "White";
//		if ((n & 4)) nm = "Periodic";
//
//		switch(n & 3)
//		{
//		case 0: pm = "N/512"; break;
//		case 1: pm = "N/1024"; break;
//		case 2: pm = "N/2048"; break;
//		case 3: pm = "Tone#2"; break;
//		}
//			
//		if (chip == &toneChip)
//			system_debug_message("sound (T): Set Noise Mode to %s, Period = %s", nm, pm);
//		else
//			system_debug_message("sound (N): Set Noise Mode to %s, Period = %s", nm, pm);
//	}
//#endif
//				chip->NoiseFB = (n & 4) ? FB_WNOISE : FB_PNOISE;
//				n &= 3;
//				/* N/512,N/1024,N/2048,Tone #2 output */
//				chip->Period[3] = (n == 3) ? 2 * chip->Period[2] : (UpdateStep << (5+n));
//
//				/* reset noise shifter */
//				chip->RNG = NG_PRESET;
//				chip->Output[3] = chip->RNG & 1;
//
//			}
//			break;
//		}
//	}
//	else
//	{
//		int r = chip->LastRegister;
//		int c = r/2;
//
//		switch (r)
//		{
//			case 0:	/* tone 0 : frequency */
//			case 2:	/* tone 1 : frequency */
//			case 4:	/* tone 2 : frequency */
//				chip->Register[r] = (chip->Register[r] & 0x0f) | ((data & 0x3f) << 4);
//				chip->Period[c] = UpdateStep * chip->Register[r];
//				if (chip->Period[c] == 0) chip->Period[c] = UpdateStep;
//				if (r == 4)
//				{
//					/* update noise shift frequency */
//					if ((chip->Register[6] & 0x03) == 0x03)
//						chip->Period[3] = 2 * chip->Period[2];
//				}
//#ifdef NEOPOP_DEBUG
//	if (filter_sound)
//	{
//		if (chip == &toneChip)
//			system_debug_message("sound (T): Set Tone %d Frequency to %d", c, chip->Register[r]);
//		else
//			system_debug_message("sound (N): Set Tone %d Frequency to %d", c, chip->Register[r]);
//	}
//#endif
//				break;
//		}
//	}
}

//=============================================================================

void dac_write(void)
{
//	if (mute) return;	// Ignore	
//
//	//Write to buffer
//	dacBufferL[dacBufferWrite] = ram[0xA2];
//	dacBufferWrite++;
//	if (dacBufferWrite == DAC_BUFFERSIZE)
//		dacBufferWrite = 0;
//
//	//Overflow?
//	dacBufferCount++;
//	if (dacBufferCount == DAC_BUFFERSIZE)
//	{
//		system_message("dac_write: DAC buffer overflow\nPlease report this to the author.");
//		dacBufferCount = 0;
//	}
}
	
void dac_update(_u8* dac_buffer, int length_bytes)
{
//	while (length_bytes > 0)
//	{
//		//Copy then clear DAC data
//		*(dac_buffer++) = dacBufferL[dacBufferRead];
//		dacBufferL[dacBufferRead] = 0x80;
//			
//		length_bytes --;	// 1 byte = 8 bits
//
//		if (dacBufferCount > 0)
//		{
//			dacBufferCount --;
//
//			//Advance the DAC read
//			dacBufferRead++;
//			if (dacBufferRead == DAC_BUFFERSIZE)
//				dacBufferRead = 0;
//		}
//	}
}

//=============================================================================

//Resets the sound chips, also used whenever sound options are changed
void sound_init(int SampleRate)
{
	int i;
	double out;

	/* the base clock for the tone generators is the chip clock divided by 16; */
	/* for the noise generator, it is clock / 256. */
	/* Here we calculate the number of steps which happen during one sample */
	/* at the given sample rate. No. of events = sample rate / (clock/16). */
	/* STEP is a multiplier used to turn the fraction into a fixed point */
	/* number. */
	UpdateStep = (_u32)(((double)STEP * SampleRate * 16) / SOUNDCHIPCLOCK);

	//Initialise Left Chip
	memset(&toneChip, 0, sizeof(SoundChip));

	//Initialise Right Chip
	memset(&noiseChip, 0, sizeof(SoundChip));

	//Default register settings
	for (i = 0;i < 8;i+=2)
	{
		toneChip.Register[i] = 0;
		toneChip.Register[i + 1] = 0x0f;	/* volume = 0 */
		noiseChip.Register[i] = 0;
		noiseChip.Register[i + 1] = 0x0f;	/* volume = 0 */
	}

	for (i = 0;i < 4;i++)
	{
		toneChip.Output[i] = 0;
		toneChip.Period[i] = toneChip.Count[i] = UpdateStep;
		noiseChip.Output[i] = 0;
		noiseChip.Period[i] = noiseChip.Count[i] = UpdateStep;
	}

	//Build the volume table
	out = MAX_OUTPUT / 3;

	/* build volume table (2dB per step) */
	for (i = 0;i < 15;i++)
	{
		VolTable[i] = (_u32)out;
		out /= 1.258925412;	/* = 10 ^ (2/20) = 2dB */
	}
	VolTable[15] = 0;


	//Clear the DAC buffer
	for (i = 0; i < DAC_BUFFERSIZE; i++)
		dacBufferL[i] = 0x80;

	dacBufferCount = 0;
	dacBufferRead = 0; 
	dacBufferWrite = 0;
}

//=============================================================================