/* 
  exampleecho.c: Example echo plugin for XMMS.

  Note that this plugin is very simple and doesn't allow for much
  customization. See the echo.c in the XMMS tarball for a better echo
  plugin.

    exampleecho: simple XMMS echo plugin, made as an example.
    Copyright (C) 2006  Kumar Appaiah <akumar [*AT] ee.iitm.ac.in>

    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

*/

#include <xmms/plugin.h>
#include <xmms/configfile.h>
#include <xmms/util.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>

#define ECHO_SCALE 0.4

void
about(void);

void
query(AFormat *afmt, gint *s_rate, gint *n_channels);

void
init(void);

void
cleanup(void);

void
configure(void);

gint
mod_samples(gpointer * d, gint length, AFormat afmt, gint srate, gint nch);

/* The plugin details for XMMS. */
EffectPlugin e_plugin = {
	NULL,
	NULL,
	"Example Echo plugin",
	init,
	cleanup,
	about,
	configure,
	mod_samples,
	query};

EffectPlugin *
get_eplugin_info(void)
{
	return &e_plugin;
}

#define BUFFER_LENGTH 16384 /* For about 0.37 seconds delay */

/* Buffers: used as circular buffers. */
static gfloat *buffer_left = NULL;
static gfloat *buffer_right = NULL;

/* Circular buffer indices. */
static guint left_index = 0;
static guint right_index = 0;


static char *about_text =
"An example echo plugin";

void
about(void)
{
	static GtkWidget *about_dialog = NULL;
	if (about_dialog != NULL)
		return;
	/* Convenient function for dialog boxes */
	about_dialog = xmms_show_message("About Example Echo Plugin",
					 about_text, "Ok", FALSE,
					 NULL, NULL);
	gtk_signal_connect(GTK_OBJECT(about_dialog), "destroy",
			   GTK_SIGNAL_FUNC(gtk_widget_destroyed),
			   &about_dialog);
}

void
query(AFormat *afmt, gint *s_rate, gint *n_channels) {
	*afmt = FMT_S16_LE;
	*s_rate = 44100;
	*n_channels = 2;
}

void init(void)
{
	if (buffer_left == NULL) {
		buffer_left = g_malloc0(sizeof(gfloat) * BUFFER_LENGTH);
	}
	if (buffer_right == NULL) {
		buffer_right = g_malloc0(sizeof(gfloat) *
		BUFFER_LENGTH);
	}
}

void
cleanup(void)
{
	g_free(buffer_left);
	buffer_left = NULL;
	g_free(buffer_right);
	buffer_right = NULL;
}

void
configure(void)
{
	/* Configuration dialog box goes here. */
}

gint
mod_samples(gpointer * d, gint length, AFormat afmt, gint srate, gint nch)
{
	/* Read data as 16 bit values */
	gint16 *data = (gint16 *) * d;
	gint i;

	/* We have "length" bytes, so "length / 2" samples */
	for (i = 0; i < length / 2; i += 2) {
		gfloat echo_val;

		/* For the left sample */
		echo_val = buffer_left[left_index]; /* Retrieve delayed value */
		buffer_left[left_index++] = data[i]; /* Store latest sample */
		data[i] = (1 - ECHO_SCALE) * data[i] + ECHO_SCALE * echo_val; /* Set the echoed value */
		left_index = left_index % BUFFER_LENGTH; /* Circular buffer shift */
		/* Do the same for the right channel samples */
		echo_val = buffer_right[right_index]; /* Retrieve delayed value */
		buffer_right[right_index++] = data[i + 1]; /* Store latest sample */
		data[i + 1] = (1 - ECHO_SCALE) * data[i + 1] + ECHO_SCALE * echo_val; /* Set the echoed value */
		right_index = right_index % BUFFER_LENGTH; /* Circular buffer shift */
	}
	return length; /* Amount of data we have processed. */
}