/*
 * Copyright (C) 1997-2001 Id Software, Inc.
 * Copyright (C) 2010 Yamagi Burmeister
 * Copyright (C) 2005 Ryan C. Gordon
 *
 * 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.
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
 * USA.
 *
 * =======================================================================
 *
 * The lower layer of the sound system. It utilizes SDL for writing the
 * sound data to the device. This file was rewritten by Yamagi to solve
 * a lot problems arrising from the old Icculus Quake 2 SDL backend like
 * stuttering and cracking. This implementation is based on ioQuake3s
 * snd_sdl.c.
 *
 * =======================================================================
 */  

#include <SDL.h>
#include "../client/header/client.h"
#include "../client/sound/header/local.h"

/* Global stuff */
int snd_inited = 0;
static int dmapos = 0;
static int dmasize = 0;
static dma_t *dmabackend;

/* The callback */
static void 
sdl_audio_callback(void *data, Uint8 *stream, int length)
{
	int length1;
	int length2;
	int pos = (dmapos * (dmabackend->samplebits / 8));

	if (pos >= dmasize)
	{
		dmapos = pos = 0;
	}

	/* This can't happen! */
	if (!snd_inited)
	{
		memset(stream, '\0', length);
		return;
	}

	int tobufferend = dmasize - pos;

	if (length > tobufferend)
	{
		length1 = tobufferend;
		length2 = length - length1;
	}
	else
	{
		length1= length;
		length2 = 0;
	}

	memcpy(stream, dmabackend->buffer + pos, length1);

	/* Set new position */
	if (length2 <= 0)
	{
		dmapos += (length1 / (dmabackend->samplebits / 8));
	}
	else
	{
		memcpy(stream + length1, dmabackend->buffer, length2);
		dmapos = (length2 / (dmabackend->samplebits / 8));
	}

    if (dmapos >= dmasize)
	{
		dmapos = 0;
	}
}

qboolean
SNDDMA_Init(void)
{
	char drivername[128];
	SDL_AudioSpec desired;
	SDL_AudioSpec obtained;
	int tmp, val;

	/* This should never happen,
	   but this is Quake 2 ... */
	if (snd_inited)
	{
		return 1;
	}

	int sndbits = (Cvar_Get("sndbits", "16", CVAR_ARCHIVE))->value;
	int sndfreq = (Cvar_Get("s_khz", "44", CVAR_ARCHIVE))->value;
	int sndchans = (Cvar_Get("sndchannels", "2", CVAR_ARCHIVE))->value;

	Com_Printf("Starting SDL audio callback.\n");

	if (!SDL_WasInit(SDL_INIT_AUDIO))
	{
		if (SDL_Init(SDL_INIT_AUDIO) == -1)
		{
			Com_Printf ("Couldn't init SDL audio: %s.\n", SDL_GetError ());
			return 0;
		}
	}
	
	if (SDL_AudioDriverName(drivername, sizeof(drivername)) == NULL)
	{
		strcpy(drivername, "(UNKNOW)");
	}

	Com_Printf("SDL audio driver is \"%s\".\n", drivername);

	memset(&desired, '\0', sizeof(desired));
	memset(&obtained, '\0', sizeof(obtained));

	/* Users are stupid */
	if ((sndbits != 16) && (sndbits != 8))
	{
		sndbits = 16;
	}

	if (sndfreq == 48)
	{
		desired.freq = 48000;
	}
	else if (sndfreq == 44)
	{
		desired.freq = 44100;
	}
	else if (sndfreq == 22)
	{
		desired.freq = 22050;
	}
	else if (sndfreq == 11)
	{
		desired.freq = 11025;
	}

	desired.format = ((sndbits == 16) ? AUDIO_S16SYS : AUDIO_U8);

	if (desired.freq <= 11025)
	{
		desired.samples = 256;
	}
	else if (desired.freq <= 22050)
	{
		desired.samples = 512;
	}
	else if (desired.freq <= 44100)
	{
		desired.samples = 1024;
	}
	else
	{
		desired.samples = 2048;
	}

	desired.channels = sndchans;
	desired.callback = sdl_audio_callback;

	/* Okay, let's try our luck */
	if (SDL_OpenAudio(&desired, &obtained) == -1)
	{
		Com_Printf("SDL_OpenAudio() failed: %s\n", SDL_GetError());
		SDL_QuitSubSystem(SDL_INIT_AUDIO);
		return 0;
	}

	/* This points to the frontend */
	dmabackend = &dma;

	dmapos = 0;
	dmabackend->samplebits = obtained.format & 0xFF;
	dmabackend->channels = obtained.channels;

	tmp = (obtained.samples * obtained.channels) * 10;
	if (tmp & (tmp - 1))
	{	/* make it a power of two */
		val = 1;
		while (val < tmp)
			val <<= 1;

		tmp = val;
	}
	dmabackend->samples = tmp;

	dmabackend->submission_chunk = 1;
	dmabackend->speed = obtained.freq;
	dmasize = (dmabackend->samples * (dmabackend->samplebits / 8));
	dmabackend->buffer = calloc(1, dmasize);

	SDL_PauseAudio(0);

	Com_Printf("SDL audio initialized.\n");
	snd_inited = 1;
	return 1;
}

int
SNDDMA_GetDMAPos(void)
{
	return dmapos;
}

void
SNDDMA_Shutdown(void)
{
	Com_Printf("Closing SDL audio device...\n");
    SDL_PauseAudio(1);
    SDL_CloseAudio();
    SDL_QuitSubSystem(SDL_INIT_AUDIO);
    free(dmabackend->buffer);
    dmabackend->buffer = NULL;
    dmapos = dmasize = 0;
    snd_inited = 0;
    Com_Printf("SDL audio device shut down.\n");
}

/* 
 * This sends the sound to the device.
 * In the SDL backend it's useless and
 * only implemented for compatiblity.
 */
void
SNDDMA_Submit(void)
{
	SDL_UnlockAudio();
}

void
SNDDMA_BeginPainting(void)
{
	SDL_LockAudio();
}