// Emacs style mode select   -*- C++ -*-
//-----------------------------------------------------------------------------
//
// Copyright(C) 2007 Simon Howard
//
// 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.
//
// DESCRIPTION:
//    PC speaker interface.
//
//-----------------------------------------------------------------------------

// NSM: reworked to function without sdl_mixer (needs new i_sound.c)

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h>

#include "SDL.h"

#include "pcsound.h"

//e6y
#include "lprintf.h"

#include "i_sound.h" // snd_samplerate

#define SQUARE_WAVE_AMP 0x2000

static pcsound_callback_func callback;

// Output sound format

static int mixing_freq;
//static Uint16 mixing_format;
//static int mixing_channels;

// Currently playing sound
// current_remaining is the number of remaining samples that must be played
// before we invoke the callback to get the next frequency.

static int current_remaining;
static int current_freq;

static int phase_offset = 0;

static int pcsound_inited = 0;

// Mixer function that does the PC speaker emulation

void PCSound_Mix_Callback(void *udata, Uint8 *stream, int len)
{
    Sint16 *leftptr;
    Sint16 *rightptr;
    Sint16 this_value;
    int oldfreq;
    int i;
    int nsamples;

    // safe to call even if not active
    if (!pcsound_inited)
      return;


    // Number of samples is quadrupled, because of 16-bit and stereo

    nsamples = len / 4;

    leftptr = (Sint16 *) stream;
    rightptr = ((Sint16 *) stream) + 1;

    // Fill the output buffer

    for (i=0; i<nsamples; ++i)
    {
        // Has this sound expired? If so, invoke the callback to get
        // the next frequency.

        while (current_remaining == 0)
        {
            oldfreq = current_freq;

            // Get the next frequency to play

            callback(&current_remaining, &current_freq);

            if (current_freq != 0)
            {
                // Adjust phase to match to the new frequency.
                // This gives us a smooth transition between different tones,
                // with no impulse changes.

                phase_offset = (phase_offset * oldfreq) / current_freq;
            }

            current_remaining = (current_remaining * mixing_freq) / 1000;
        }

        // Set the value for this sample.

        if (current_freq == 0)
        {
            // Silence

            this_value = 0;
        }
        else
        {
            int frac;

            // Determine whether we are at a peak or trough in the current
            // sound.  Multiply by 2 so that frac % 2 will give 0 or 1
            // depending on whether we are at a peak or trough.

            frac = (phase_offset * current_freq * 2) / mixing_freq;

            if ((frac % 2) == 0)
            {
                this_value = SQUARE_WAVE_AMP;
            }
            else
            {
                this_value = -SQUARE_WAVE_AMP;
            }

            ++phase_offset;
        }

        --current_remaining;

        // Use the same value for the left and right channels.

        *leftptr += this_value;
        *rightptr += this_value;

        leftptr += 2;
        rightptr += 2;
    }
}

static int PCSound_SDL_Init(pcsound_callback_func callback_func)
{
    mixing_freq = snd_samplerate;

    callback = callback_func;
    current_freq = 0;
    current_remaining = 0;
    pcsound_inited = 1;

    return 1;
}

static void PCSound_SDL_Shutdown(void)
{
    pcsound_inited = 0;
}

pcsound_driver_t pcsound_sdl_driver =
{
    "SDL",
    PCSound_SDL_Init,
    PCSound_SDL_Shutdown,
};

