/*
Copyright (C) 2003-2004 Ryan C. Gordon. and James Bentler

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.

Originally written by Ryan C. Gordon. (icculus@clutteredmind.org)
Adapted to work with JonoF's port by James Bentler (bentler@cs.umn.edu)

*/
#include <stdlib.h>
#include <string.h>

#include "dsl.h"
#include "compat.h"
#ifdef USE_OPENAL
#include "openal.h"
#endif
#include "SDL.h"
#include "SDL_mixer.h"

extern int MV_MixPage;

int DSL_ErrorCode = DSL_Ok;

static int mixer_initialized;

static void(*_CallBackFunc)(void);
static volatile char *_BufferStart;
static int _BufferSize;
static int _NumDivisions;
static int _SampleRate;
static int _remainder;

static Mix_Chunk *blank;
static unsigned char *blank_buf;

/*
possible todo ideas: cache sdl/sdl mixer error messages.
*/

char *DSL_ErrorString(int ErrorNumber)
{
    char *ErrorString;

    switch (ErrorNumber)
    {
    case DSL_Warning:
    case DSL_Error:
        ErrorString = DSL_ErrorString(DSL_ErrorCode);
        break;

    case DSL_Ok:
        ErrorString = "SDL Driver ok.";
        break;

    case DSL_SDLInitFailure:
        ErrorString = "SDL Audio initialization failed.";
        break;

    case DSL_MixerActive:
        ErrorString = "SDL Mixer already initialized.";
        break;

    case DSL_MixerInitFailure:
        ErrorString = "SDL Mixer initialization failed.";
        break;

    default:
        ErrorString = "Unknown SDL Driver error.";
        break;
    }

    return ErrorString;
}

static void DSL_SetErrorCode(int ErrorCode)
{
    DSL_ErrorCode = ErrorCode;
}

int DSL_Init(void)
{
    DSL_SetErrorCode(DSL_Ok);

    if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0)
    {
        DSL_SetErrorCode(DSL_SDLInitFailure);

        return DSL_Error;
    }

    return DSL_Ok;
}

void DSL_Shutdown(void)
{
    DSL_StopPlayback();
}

static void mixer_callback(int chan, void *stream, int len, void *udata)
{
    Uint8 *stptr;
    Uint8 *fxptr;
    int copysize;

    /* len should equal _BufferSize, else this is screwed up */

    stptr = (Uint8 *)stream;

    if (_remainder > 0)
    {
        copysize = min(len, _remainder);

        fxptr = (Uint8 *)(&_BufferStart[MV_MixPage *
                                        _BufferSize]);

        memcpy(stptr, fxptr+(_BufferSize-_remainder), copysize);

        len -= copysize;
        _remainder -= copysize;

        stptr += copysize;
    }

    while (len > 0)
    {
        /* new buffer */

#ifdef USE_OPENAL
        AL_Update();
#endif

        _CallBackFunc();

        fxptr = (Uint8 *)(&_BufferStart[MV_MixPage *
                                        _BufferSize]);

        copysize = min(len, _BufferSize);

        memcpy(stptr, fxptr, copysize);

        len -= copysize;

        stptr += copysize;
    }

    _remainder = len;
}

int   DSL_BeginBufferedPlayback(char *BufferStart,
                                int BufferSize, int NumDivisions, unsigned SampleRate,
                                int MixMode, void(*CallBackFunc)(void))
{
    Uint16 format;
    int channels;
    int chunksize;

    if (mixer_initialized)
    {
        DSL_SetErrorCode(DSL_MixerActive);

        return DSL_Error;
    }

    _CallBackFunc = CallBackFunc;
    _BufferStart = BufferStart;
    _BufferSize = (BufferSize / NumDivisions);
    _NumDivisions = NumDivisions;
    _SampleRate = SampleRate;

    _remainder = 0;

    format = (MixMode & SIXTEEN_BIT) ? AUDIO_S16SYS : AUDIO_U8;
    channels = (MixMode & STEREO) ? 2 : 1;

    /*
       23ms is typically ideal (11025,22050,44100)
       46ms isn't bad
    */

    chunksize = 512;

    if (SampleRate >= 16000) chunksize *= 2;
    if (SampleRate >= 32000) chunksize *= 2;

    /*
    // SDL mixer does this already
       if (MixMode & SIXTEEN_BIT) chunksize *= 2;
       if (MixMode & STEREO) chunksize *= 2;
    */

    if (Mix_OpenAudio(SampleRate, format, channels, chunksize) < 0)
    {
        DSL_SetErrorCode(DSL_MixerInitFailure);

        return DSL_Error;
    }

    /*
       Mix_SetPostMix(mixer_callback, NULL);
    */
    /* have to use a channel because postmix will overwrite the music... */
    Mix_RegisterEffect(0, mixer_callback, NULL, NULL);

    /* create a dummy sample just to allocate that channel */
    blank_buf = (Uint8 *)malloc(4096);
    memset(blank_buf, 0, 4096);

    blank = Mix_QuickLoad_RAW(blank_buf, 4096);

    Mix_PlayChannel(0, blank, -1);

    mixer_initialized = 1;

    return DSL_Ok;
}

void DSL_StopPlayback(void)
{
    if (mixer_initialized)
    {
        Mix_HaltChannel(0);
    }

    if (blank != NULL)
    {
        Mix_FreeChunk(blank);
    }

    blank = NULL;

    if (blank_buf  != NULL)
    {
        free(blank_buf);
    }

    blank_buf = NULL;

    if (mixer_initialized)
    {
        Mix_CloseAudio();
    }

    mixer_initialized = 0;
}

unsigned DSL_GetPlaybackRate(void)
{
    return _SampleRate;
}

int DisableInterrupts(void)
{
    SDL_LockAudio();
    return(0);
}
 
int RestoreInterrupts(int flags)
{
    SDL_UnlockAudio();
    return(0);
}