/*
 * comb.c
 * Comb filter the input and send it to the output.
 *
 * Author: Christopher Dobrian
 *
 * This program uses the PortAudio Portable Audio Library.
 * For more information see: http://www.portaudio.com
 *
 */

#include <stdio.h>
#include <math.h>
#include "portaudio.h"

#define NUM_SECONDS   (10)
#define SAMPLE_RATE   (44100)
#define BUFFER_SIZE   (256)
#define PIPE_SIZE (512)

typedef struct {
	int saved_current_address;
	float leftpipe[PIPE_SIZE];
	float rightpipe[PIPE_SIZE];
	int left_delaysamps;
	int right_delaysamps;
} paAudioData;

/* This routine will be called by the PortAudio engine when audio is
needed. */

static int combCallback( void *inputBuffer, void *outputBuffer, unsigned
long framesPerBuffer, PaTimestamp outTime, void *userData )
{

/* Cast data passed through stream to the format of the local structure. */
	paAudioData *data = (paAudioData*)userData;
	float *in = (float*)inputBuffer;
	float *out = (float*)outputBuffer;

	unsigned int i;
	int current_address;
	int left_delayedaddress;
	int right_delayedaddress;

	current_address = data->saved_current_address; // get saved current
address from data structure
	left_delayedaddress = current_address - data->left_delaysamps;
	while ( left_delayedaddress < 0 ) left_delayedaddress += PIPE_SIZE;
	right_delayedaddress = current_address - data->right_delaysamps;
	while ( right_delayedaddress < 0 ) right_delayedaddress += PIPE_SIZE;

	for( i = 0 ; i < framesPerBuffer ; i++ )
	{

		current_address = (current_address+1)%PIPE_SIZE;
		left_delayedaddress = (left_delayedaddress+1)%PIPE_SIZE;
		right_delayedaddress = (right_delayedaddress+1)%PIPE_SIZE;
		data->leftpipe[current_address] = *in++;
		data->rightpipe[current_address] = *in++;

		*out++ =
((data->leftpipe[current_address])+(data->leftpipe[left_delayedaddress]))*0.5;		/*
left */
		*out++ =
((data->rightpipe[current_address])+(data->rightpipe[right_delayedaddress]))*0.5;		/*
right */

	}
	data->saved_current_address = current_address; // save the current
address for use in the next callback

	return 0;
}

/*******************************************************************/

static paAudioData data;

int main(void);

int main(void)
{
	PortAudioStream *stream;
	PaError err;

	unsigned int i;

	printf("PortAudio: Simple Comb Filter.\n");

/* Initialize data for use by callback. */
	data.saved_current_address = 0;
	data.left_delaysamps = SAMPLE_RATE*0.002;
	data.right_delaysamps = SAMPLE_RATE*0.0025;
	for ( i = 0 ; i < PIPE_SIZE ; i++ ) {
		data.leftpipe[i] = 0.0;
		data.rightpipe[i] = 0.0;
	}

/* Initialize library before making any other calls. */
	err = Pa_Initialize();
	if( err != paNoError ) goto error;

/* Open an audio I/O stream. */
	err = Pa_OpenDefaultStream(
				&stream,
				2,              /* two input channels */
				2,              /* stereo output */
				paFloat32,      /* 32 bit floating point output */
				SAMPLE_RATE,
				BUFFER_SIZE,            /* frames per buffer */
				0,              /* number of buffers, if zero then use default minimum */
				combCallback,
				&data );
	if( err != paNoError ) goto error;

	err = Pa_StartStream( stream );
	if( err != paNoError ) goto error;

/* Sleep for several seconds. */
	Pa_Sleep(NUM_SECONDS*1000);

	err = Pa_StopStream( stream );
	if( err != paNoError ) goto error;

	err = Pa_CloseStream( stream );
	if( err != paNoError ) goto error;

	Pa_Terminate();
	printf("Finished.\n");
	return err;

error:
	Pa_Terminate();
	fprintf( stderr, "An error occured while using the portaudio stream.\n" );
	fprintf( stderr, "Error number: %d\n", err );
	fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
	return err;
}