/* 
 * FreeSWITCH Modular Media Switching Software Library / Soft-Switch Application
 * Copyright (C) 2008, Eric des Courtis <eric.des.courtis@benbria.com>
 *
 * Version: MPL 1.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * Eric des Courtis <eric.des.courtis@benbria.com>
 * Copyright (C) Benbria. All Rights Reserved.
 *
 * Contributor(s):
 * 
 * Eric des Courtis <eric.des.courtis@benbria.com>
 *
 *
 * mod_vmd.c -- Voicemail Detection Module
 *
 * This module detects voicemail beeps at any frequency in O(1) time.
 * 
 */

#include <switch.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#ifdef WIN32
#include <float.h>
#define ISNAN(x) (!!(_isnan(x)))
#else
#define ISNAN(x) ((x)== NAN)
#endif

/* Number of points for beep detection */
#define POINTS 32

/* Number of valid points required for beep detection */
#define VALID 22

/* Maximum number of invalid points 
 * to declare beep has stopped */
#define MAX_CHIRP 22

/* Minimum time for a beep */
#define MIN_TIME 8000

/* Minimum amplitude of the signal */
#define MIN_AMPL 0.10

/* Minimum beep frequency */
#define MIN_FREQ (600)

/* Maximum beep frequency */
#define MAX_FREQ (1100)

/* PSI function for amplitude calculation*/
#define PSI(x) (x[1]*x[1]-x[2]*x[0])

/* Sample rate */
#define F (8000)

/* Conversion of frequency to Hz */
#define TO_HZ(f) ((F * f) / (2.0 * M_PI))

/* Number of points in discreet energy separation */
#define P (5)

/* Maximum signed value of int16_t 
 * DEPRECATED */
#define ADJUST (32768)
/* Same as above times two 
 * DEPRECATED */
#define ADJUST_MAX (65536)

/* Discreet energy separation tolerance to error */
#define TOLERANCE (0.20)

/* Maximum value within tolerance */
#define TOLERANCE_T(m) (m + (m * TOLERANCE))

/* Minimum value within tolerance */
#define TOLERANCE_B(m) (m - (m * TOLERANCE))

/* Syntax of the API call */
#define VMD_SYNTAX "<uuid> <command>"

/* Number of expected parameters in api call */
#define VMD_PARAMS 2

/* FreeSWITCH CUSTOM event type */
#define VMD_EVENT_BEEP "vmd::beep"

/* Prototypes */
SWITCH_MODULE_SHUTDOWN_FUNCTION(mod_vmd_shutdown);
SWITCH_STANDARD_API(vmd_api_main);

SWITCH_MODULE_LOAD_FUNCTION(mod_vmd_load);
SWITCH_MODULE_DEFINITION(mod_vmd, mod_vmd_load, NULL, NULL);
SWITCH_STANDARD_APP(vmd_start_function);

/* Type that holds state information about the beep */
typedef enum vmd_state{
    BEEP_DETECTED, BEEP_NOT_DETECTED
} vmd_state_t;

/* Type that holds data for 5 points of discreet energy separation */
typedef struct vmd_point{
    double freq;
    double ampl;
} vmd_point_t;

/* Type that holds codec information */
typedef struct vmd_codec_info{
    int rate;
    int channels;
} vmd_codec_info_t;

/* Type that holds session information pertinent to the vmd module */
typedef struct vmd_session_info{
    /* State of the session */
    vmd_state_t state;
    /* Snapshot of DESA samples */
    vmd_point_t points[POINTS];
    /* Internal FreeSWITCH session */
    switch_core_session_t *session;
    /* Codec information for the session */
    vmd_codec_info_t vmd_codec;
    /* Current position in the snapshot */
    unsigned int pos;
    /* Frequency aproximation of a detected beep */
    double beep_freq;
    /* A count of how long a distinct beep was detected by
     * by the discreet energy separation algorithm */
    switch_size_t timestamp;
} vmd_session_info_t;

static switch_bool_t process_data(vmd_session_info_t *vmd_info, switch_frame_t *frame);
static switch_bool_t vmd_callback(switch_media_bug_t *bug, void *user_data, switch_abc_type_t type);
static double freq_estimator(double *x);
static double ampl_estimator(double *x);
static void convert_pts(int16_t *i_pts, double *d_pts, int16_t max);
static void find_beep(vmd_session_info_t *vmd_info, switch_frame_t *frame);
static double median(double *m, int n);

/*
#define PRINT(a) do{ switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_WARNING, a); }while(0)
#define PRINT2(a, b) do{ switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_WARNING, a, b); }while(0)
*/

static switch_bool_t vmd_callback(switch_media_bug_t *bug, 
								  void *user_data,
								  switch_abc_type_t type)
{
	vmd_session_info_t *vmd_info;
	switch_codec_t *read_codec;
	switch_frame_t *frame;

	vmd_info = (vmd_session_info_t *)user_data;
	if(vmd_info == NULL) {
		return SWITCH_FALSE;
	}

	switch(type){

	case SWITCH_ABC_TYPE_INIT:
		read_codec = switch_core_session_get_read_codec(vmd_info->session);
		vmd_info->vmd_codec.rate = read_codec->implementation->samples_per_second;
		vmd_info->vmd_codec.channels = read_codec->implementation->number_of_channels;
		break;

	case SWITCH_ABC_TYPE_READ_PING:
	case SWITCH_ABC_TYPE_CLOSE:
	case SWITCH_ABC_TYPE_READ:
	case SWITCH_ABC_TYPE_WRITE:
		break;

	case SWITCH_ABC_TYPE_READ_REPLACE:
		frame = switch_core_media_bug_get_read_replace_frame(bug);
		return process_data(vmd_info, frame);

	case SWITCH_ABC_TYPE_WRITE_REPLACE:
		break;
	}

	return SWITCH_TRUE;
}

static switch_bool_t process_data(vmd_session_info_t *vmd_info, 
								  switch_frame_t *frame)
{
	uint32_t i;
	unsigned int j;
	double pts[P];
	int16_t *data;
	int16_t max;
	switch_ssize_t len;

	len = frame->samples * sizeof(int16_t);
	data = (int16_t *)frame->data;

	for(max = (int16_t)abs(data[0]), i = 1; i < frame->samples; i++) {
		if ((int16_t)abs(data[i]) > max) {
			max = (int16_t)abs(data[i]);
		}
	}

/*
    if(vmd_info->data_len != len){
	vmd_info->data_len = len;
	if(vmd_info->data != NULL) free(vmd_info->data);
	vmd_info->data = (int16_t *)malloc(len);
	if(vmd_info->data == NULL) return SWITCH_FALSE;
    } 

    (void)memcpy(vmd_info->data, data, len);
    for(i = 2; i < frame->samples; i++){
	vmd_info->data[i] = 
	    0.0947997 * data[i] 
	    - 
	    0.0947997 * data[i - 2] 
	    - 
	    1.4083405 * vmd_info->data[i - 1] 
	    + 
	    0.8104005 * vmd_info->data[i - 2];
    }
*/

    for(i = 0, j = vmd_info->pos; i < frame->samples; j++, j %= POINTS, i += 5) {
	/*	convert_pts(vmd_info->data + i, pts); */
		convert_pts(data + i, pts, max);
		vmd_info->points[j].freq = TO_HZ(freq_estimator(pts));
		vmd_info->points[j].ampl = ampl_estimator(pts);
		vmd_info->pos = j % POINTS;
		find_beep(vmd_info, frame);
    }

    return SWITCH_TRUE;
}

static void find_beep(vmd_session_info_t *vmd_info, switch_frame_t *frame)
{
	int i;
	int c;
	double m[POINTS];
	double med;
	unsigned int j = (vmd_info->pos + 1) % POINTS;
	unsigned int k = j;
	switch_event_t *event;
	switch_status_t status;
	switch_event_t *event_copy;
	switch_channel_t *channel = switch_core_session_get_channel(vmd_info->session); 

	switch(vmd_info->state){
	case BEEP_DETECTED:
		for(c = 0, i = 0; i < POINTS; j++, j %= POINTS, i++){
			vmd_info->timestamp++;
			if (vmd_info->points[j].freq < TOLERANCE_T(vmd_info->beep_freq) &&
				vmd_info->points[j].freq > TOLERANCE_B(vmd_info->beep_freq)) {
					c++;
					vmd_info->beep_freq = (vmd_info->beep_freq * 0.95) + (vmd_info->points[j].freq * 0.05);
			}
		}

		if (c < (POINTS - MAX_CHIRP)) {
			vmd_info->state = BEEP_NOT_DETECTED;
			if (vmd_info->timestamp < MIN_TIME) {
				break;
			}

			status = switch_event_create_subclass(&event, SWITCH_EVENT_CUSTOM, VMD_EVENT_BEEP);
			if (status != SWITCH_STATUS_SUCCESS) {
				return;
			}

			switch_event_add_header_string(event, SWITCH_STACK_BOTTOM, "Beep-Status", "stop");
			switch_event_add_header(event, SWITCH_STACK_BOTTOM, "Beep-Time", "%d", (int)vmd_info->timestamp / POINTS);
			switch_event_add_header(event, SWITCH_STACK_BOTTOM, "Unique-ID",
				"%s", switch_core_session_get_uuid(vmd_info->session));
			switch_event_add_header(event, SWITCH_STACK_BOTTOM, "Frequency", "%6.4lf", vmd_info->beep_freq);
			switch_event_add_header_string(event, SWITCH_STACK_BOTTOM, "call-command", "vmd");

			if ((switch_event_dup(&event_copy, event)) != SWITCH_STATUS_SUCCESS) {
				return;
			}

			switch_core_session_queue_event(vmd_info->session, &event);
			switch_event_fire(&event_copy);

			switch_log_printf(
				SWITCH_CHANNEL_LOG,
				SWITCH_LOG_INFO,
				"<<< VMD - Beep Detected >>>\n"
				);
			switch_channel_set_variable(channel, "vmd_detect", "TRUE");

			vmd_info->timestamp = 0;
		}

		break;

	case BEEP_NOT_DETECTED:

		for(i = 0; i < POINTS; k++, k %= POINTS, i++){
			m[i] = vmd_info->points[k].freq;
			if (ISNAN(m[i])) {
				m[i] = 0.0;
			}
		}

		med = median(m, POINTS);
		if (ISNAN(med)){
			for(i = 0; i < POINTS; i++){
				if (!ISNAN(m[i])){
					med = m[i];
					break;
				}
			}
		}

		for(c = 0, i = 0; i < POINTS; j++, j %= POINTS, i++){
			if (vmd_info->points[j].freq < TOLERANCE_T(med) &&
				vmd_info->points[j].freq > TOLERANCE_B(med)){
					if (vmd_info->points[j].ampl > MIN_AMPL &&
						vmd_info->points[j].freq > MIN_FREQ &&
						vmd_info->points[j].freq < MAX_FREQ){
							c++;
					}
			}
		}

		if(c >= VALID){
			vmd_info->state = BEEP_DETECTED;
			vmd_info->beep_freq = med;
			vmd_info->timestamp = 0;
		}

		break;
	}
}

/* Find the median of an array of doubles */
static double median(double *m, int n)
{
	int i;
	int less;
	int greater;
	int equal;
	double min;
	double max;
	double guess;
	double maxltguess;
	double mingtguess;

	min = max = m[0] ;

	for (i = 1; i < n; i++) {
		if(m[i] < min) min = m[i];
		if(m[i] > max) max = m[i];
	}

	for(;;) {
		guess = ( min + max ) / 2;
		less = 0;
		greater = 0;
		equal = 0;
		maxltguess = min;
		mingtguess = max;

		for(i = 0; i < n; i++) {
			if (m[i] < guess) {
				less++;
				if(m[i] > maxltguess) {
					maxltguess = m[i];
				}
			} else if (m[i] > guess) {
				greater++;
				if(m[i] < mingtguess) {
					mingtguess = m[i];
				}
			} else {
				equal++;
			}
		}

		if (less <= ( n + 1 ) / 2 && greater <= ( n + 1 ) / 2) {
			break;
		} else if (less > greater) {
			max = maxltguess;
		} else {
			min = mingtguess;
		}
	}

	if (less >= ( n + 1 ) / 2) {
		return maxltguess;
	} else if (less + equal >= ( n + 1 ) / 2) {
		return guess;
	}

	return mingtguess;
}

/* Convert many points for Signed L16 to relative floating point */
static void convert_pts(int16_t *i_pts, double *d_pts, int16_t max)
{
    int i;
	for(i = 0; i < P; i++) {
		/* Signed L16 to relative floating point conversion */
		d_pts[i] = ((((double)(i_pts[i]) + (double)max) / (double)(2 * max)) - 0.5) * 2.0;
	}
}

/* Amplitude estimator for DESA-2 */
double ampl_estimator(double *x)
{
    double freq_sq;

    freq_sq = freq_estimator(x);
    freq_sq *= freq_sq;

    return sqrt( PSI(x) / sin(freq_sq) ); 
}

/* The DESA-2 algorithm */
double freq_estimator(double *x)
{
    return 0.5 * acos(
	(((x[2] * x[2]) - (x[0] * x[4]))
	-
	( (x[1] * x[1]) - (x[0] * x[2]))
	-
	( (x[3] * x[3]) - (x[2] * x[4])))
	/
	(2.0 * ((x[2] * x[2]) - (x[1] * x[3])))
 
    );
}


SWITCH_MODULE_LOAD_FUNCTION(mod_vmd_load)
{
    switch_application_interface_t *app_interface;
    switch_api_interface_t *api_interface;
    /* connect my internal structure to the blank pointer passed to me */
    *module_interface = 
	switch_loadable_module_create_module_interface(pool, modname);
    
    switch_log_printf(
	SWITCH_CHANNEL_LOG, 
	SWITCH_LOG_NOTICE, 
	"Voicemail detection enabled\n"
    );

    SWITCH_ADD_APP(app_interface, "vmd", "Detect beeps", "Detect voicemail beeps", 
	vmd_start_function, "[start] [stop]", SAF_NONE);
    
    SWITCH_ADD_API(api_interface, "vmd", "Detected voicemail beeps", 
	vmd_api_main, VMD_SYNTAX);

    /* indicate that the module should continue to be loaded */
    return SWITCH_STATUS_SUCCESS;
}

/* Same as api function see it for comments */
SWITCH_STANDARD_APP(vmd_start_function)
{
	switch_media_bug_t *bug;
	switch_status_t status;
	switch_channel_t *channel;
	vmd_session_info_t *vmd_info;
	int i;

	if (session == NULL) return;

	channel = switch_core_session_get_channel(session);

	/* Is this channel already set? */
	bug = (switch_media_bug_t *) switch_channel_get_private(channel, "_vmd_");
	/* If yes */
	if (bug != NULL){
		/* If we have a stop remove audio bug */
		if(strcasecmp(data, "stop") == 0){
			switch_channel_set_private(channel, "_vmd_", NULL);
			switch_core_media_bug_remove(session, &bug);
			return;
		}

		/* We have already started */
		switch_log_printf(
			SWITCH_CHANNEL_LOG, 
			SWITCH_LOG_WARNING, 
			"Cannot run 2 at once on the same channel!\n"
			);

		return;
	}

	vmd_info = (vmd_session_info_t *)switch_core_session_alloc(
		session, 
		sizeof(vmd_session_info_t)
		);

	vmd_info->state = BEEP_NOT_DETECTED;
	vmd_info->session = session;
	vmd_info->pos = 0;
	/*
	vmd_info->data = NULL;
	vmd_info->data_len = 0;
	*/
	for(i = 0; i < POINTS; i++){
		vmd_info->points[i].freq = 0.0;
		vmd_info->points[i].ampl = 0.0;
	}

	status = switch_core_media_bug_add(
		session, 
		vmd_callback, 
		vmd_info,
		0, 
		SMBF_READ_REPLACE, 
		&bug
		);

	if(status != SWITCH_STATUS_SUCCESS){
		switch_log_printf(
			SWITCH_CHANNEL_LOG,
			SWITCH_LOG_ERROR,
			"Failure hooking to stream\n"
			);
		return;
	}

	switch_channel_set_private(channel, "_vmd_", bug);

}

/* Called when the system shuts down */
SWITCH_MODULE_SHUTDOWN_FUNCTION(mod_vmd_shutdown)
{
    switch_log_printf(
	SWITCH_CHANNEL_LOG, 
	SWITCH_LOG_NOTICE, 
	"Voicemail detection disabled\n"
    );

    return SWITCH_STATUS_SUCCESS;
}

SWITCH_STANDARD_API(vmd_api_main)
{
    switch_core_session_t *vmd_session;
    switch_media_bug_t *bug;
    vmd_session_info_t *vmd_info;
    switch_channel_t *channel;
    switch_status_t status;
    int argc;
    char *argv[VMD_PARAMS];
    char *ccmd;
    char *uuid;
    char *command;
    int i;
    
    /* No command? Display usage */
    if(cmd == NULL){
	stream->write_function(stream, "-USAGE: %s\n", VMD_SYNTAX);
	return SWITCH_STATUS_SUCCESS;
    }

    /* Duplicated contents of original string */
    ccmd = strdup(cmd);
    /* Separate the arguments */
    argc = switch_separate_string(ccmd, ' ', argv, VMD_PARAMS);

    /* If we don't have the expected number of parameters 
     * display usage */
    if (argc != VMD_PARAMS){
		stream->write_function(stream, "-USAGE: %s\n", VMD_SYNTAX);
		switch_safe_free(ccmd);
		return SWITCH_STATUS_SUCCESS;
    }

    uuid = argv[0];
    command = argv[1];
     
    /* using uuid locate a reference to the FreeSWITCH session */
    vmd_session = switch_core_session_locate(uuid);

    /* If the session was not found exit */
    if (vmd_session == NULL) {
		switch_safe_free(ccmd);
		stream->write_function(stream, "-USAGE: %s\n", VMD_SYNTAX);	
		return SWITCH_STATUS_FALSE;
    }

    /* Get current channel of the session to tag the session
     * This indicates that our module is present */
    channel = switch_core_session_get_channel(vmd_session);

    /* Is this channel already set? */
    bug = (switch_media_bug_t *) switch_channel_get_private(channel, "_vmd_");
    /* If yes */
    if (bug != NULL){
        /* If we have a stop remove audio bug */
        if(strcasecmp(command, "stop") == 0) {
            switch_channel_set_private(channel, "_vmd_", NULL);
            switch_core_media_bug_remove(vmd_session, &bug);
            switch_safe_free(ccmd);
            stream->write_function(stream, "+OK\n");
            return SWITCH_STATUS_SUCCESS;
        }

	/* We have already started */
	switch_log_printf(
	    SWITCH_CHANNEL_LOG, 
	    SWITCH_LOG_WARNING, 
	    "Cannot run 2 at once on the same channel!\n"
	);
	
	switch_safe_free(ccmd);
	return SWITCH_STATUS_FALSE;
    }

    /* If we don't see the expected start exit */
    if(strcasecmp(command, "start") != 0) {
		switch_safe_free(ccmd);	
		stream->write_function(stream, "-USAGE: %s\n", VMD_SYNTAX);
		return SWITCH_STATUS_FALSE;
    }

    /* Allocate memory attached to this FreeSWITCH session for
     * use in the callback routine and to store state information */
    vmd_info = (vmd_session_info_t *)switch_core_session_alloc(
	vmd_session, 
	sizeof(vmd_session_info_t)
    );

    /* Set initial values and states */
    vmd_info->state = BEEP_NOT_DETECTED;
    vmd_info->session = vmd_session;
    vmd_info->pos = 0;
/*
    vmd_info->data = NULL;
    vmd_info->data_len = 0;
*/

    for(i = 0; i < POINTS; i++) {
		vmd_info->points[i].freq = 0.0;
		vmd_info->points[i].ampl = 0.0;
    }

    /* Add a media bug that allows me to intercept the 
     * reading leg of the audio stream */
    status = switch_core_media_bug_add(
	vmd_session, 
	vmd_callback, 
	vmd_info,
	0, 
	SMBF_READ_REPLACE, 
	&bug
    );

    /* If adding a media bug fails exit */
    if (status != SWITCH_STATUS_SUCCESS) {
		switch_log_printf(
			SWITCH_CHANNEL_LOG, 
			SWITCH_LOG_ERROR, 
			"Failure hooking to stream\n"
	);
    
	switch_safe_free(ccmd);
	return SWITCH_STATUS_FALSE;
    }

    /* Set the vmd tag to detect an existing vmd media bug */
    switch_channel_set_private(channel, "_vmd_", bug);
    
    /* Everything went according to plan! Notify the user */
    stream->write_function(stream, "+OK\n"); 
 
    switch_safe_free(ccmd);
    return SWITCH_STATUS_SUCCESS;
}


/* For Emacs:
 * Local Variables:
 * mode:c
 * indent-tabs-mode:t
 * tab-width:4
 * c-basic-offset:4
 * End:
 * For VIM:
 * vim:set softtabstop=4 shiftwidth=4 tabstop=4 expandtab:
 */