/*
	(c) 2003 Martin Voelkle & Stephane Magnenat
*/
#include <SDL/SDL.h>
#include <SDL/SDL_audio.h>
#include <vorbis/codec.h>
#include <vorbis/vorbisfile.h>
#include <stdlib.h>

int files;
int* gains;
OggVorbis_File *vfs;
int run;

#define CLAMP(a, b, c) { if ((a)<(b)) (a)=(b); else if ((a)>(c)) (a)=(c); }

void mixaudio(void *unused, Uint8 *stream, int len)
{
	static int current_section;
	char current[len];
	Sint32 final[len];

	for (int j=0; j<(len>>1); j++)
	{
		final[j]=0;
	}

	for (int i=0; i<files; i++)
	{
		// read ogg
		long rest = len;
		char *p = current;
		while(rest>0)
		{
			long ret = ov_read (&(((OggVorbis_File *)vfs)[i]), p, rest, 0, 2, 1, &current_section);
			if (ret == 0)
			{
				/* EOF */
				run = 0;
			}
			else if (ret < 0)
			{
				/* error in the stream.  Not a problem, just reporting it in
				case we (the app) cares.  In this case, we don't. */
			}
			rest -= ret;
			p += ret;
		}

		// sum sample
		for (int j=0; j<(len>>1); j++)
		{
			final[j] += ((Sint32)((Sint16 *)current)[j]) * gains[i];
		}
	}

	for (int j=0; j<(len>>1); j++)
	{
		((Sint16*)stream)[j] = (Sint16)(final[j] / (files<<8));
	}
}

void redisplay(SDL_Surface *s)
{
	for (int i=0; i<files; i++)
	{
		SDL_Rect sel = {i*30, 255-gains[i], 30, gains[i]};
		SDL_FillRect(s, &sel, SDL_MapRGB(s->format, 255, 20, 20));
		SDL_Rect black = {i*30, 0, 30, 255-gains[i]};
		SDL_FillRect(s, &black, SDL_MapRGB(s->format, 50, 50, 50));
	}
	SDL_Flip(s);
}

int main(int argc, char **argv)
{
	SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO);

	files = argc - 1;
	vfs = (OggVorbis_File *)malloc(files * sizeof(OggVorbis_File));
	gains = (int*)malloc(files * sizeof(int));

	for (int i=0; i<files; i++)
	{
		FILE* f = fopen(argv[i+1], "rb");
		if (ov_open (f, &(vfs[i]), NULL, 0) < 0)
		{
			fprintf (stderr, "Input does not appear to be an Ogg bitstream.\n");
			exit (1);
		}
		gains[i] = 128;
	}

	SDL_AudioSpec fmt;
	// Set 16-bit stereo audio at 44Khz
	fmt.freq = 44100;
	fmt.format = AUDIO_S16;
	fmt.channels = 2;
	fmt.samples = 4096;
	fmt.callback = mixaudio;
	fmt.userdata = vfs;

	// Open the audio device and start playing sound!
	if (SDL_OpenAudio(&fmt, NULL) < 0)
	{
		fprintf(stderr, "Unable to open audio: %s\n", SDL_GetError());
		exit(1);
	}

	// Init video
	SDL_Surface *screen;
    screen = SDL_SetVideoMode(files*30, 256, 32, SDL_HWSURFACE|SDL_DOUBLEBUF);
    if ( screen == NULL )
	{
		fprintf(stderr, "Unable to set 640x480 video: %s\n", SDL_GetError());
		exit(1);
	}
	redisplay(screen);

	run = 1;
	SDL_PauseAudio(0);

	SDL_Event event;
	while (run)
	{
		SDL_Delay(20);
		while (SDL_PollEvent(&event))
		{
			if (event.type == SDL_QUIT)
			{
				run = 0;
			}
			else if (event.type == SDL_MOUSEBUTTONDOWN)
			{
				int id = event.button.x/30;
				int gain = 255-event.button.y;
				CLAMP(id, 0, files-1);
				CLAMP(gain, 0, 255);
				gains[id] = gain;
				redisplay(screen);
			}
			else if (event.type == SDL_MOUSEMOTION)
			{
				if (event.motion.state)
				{
					int id = event.motion.x/30;
					int gain = 255-event.motion.y;
					CLAMP(id, 0, files-1);
					CLAMP(gain, 0, 255);
					gains[id] = gain;
					redisplay(screen);
				}
			}
		}
	}

	for(int i=0; i<files; i++)
	{
		ov_clear (&vfs[i]);
	}

	SDL_CloseAudio();
	SDL_Quit();
}