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/* radar.c */
/* io - Input & Output with Artificial Intelligence (ai) support on AVR. {{{
 *
 * Copyright (C) 2010 Nicolas Schodet
 *
 * APBTeam:
 *        Web: http://apbteam.org/
 *      Email: team AT apbteam DOT org
 *
 * 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 "common.h"
#include "radar.h"

#include "playground.h"
#include "usdist.h"

#include "modules/math/geometry/geometry.h"
#include "modules/utils/utils.h"

/** Margin to be considered inside the playground.  An obstacle can not be
 * exactly at the playground edge. */
#define RADAR_MARGIN_MM 150

/** Maximum distance for a sensor reading to be ignored if another sensor is
 * nearer. */
#define RADAR_FAR_MM 250

/** Describe a radar sensor. */
struct radar_sensor_t
{
    /** Distance updated by another module. */
    uint16_t *dist_mm;
    /** Position relative to the robot center. */
    vect_t pos;
    /** Angle relative to the robot X axis. */
    uint16_t a;
};

/** Define radar configuration. */
struct radar_sensor_t radar_sensors[] = {
#define RADAR_SENSOR_FRONT 0
      { &usdist_mm[0], { 30 - 20, 0 }, G_ANGLE_UF016_DEG (0) },
#define RADAR_SENSOR_LEFT 1
      { &usdist_mm[1], { 20 - 20, 20 }, G_ANGLE_UF016_DEG (30) },
#define RADAR_SENSOR_RIGHT 2
      { &usdist_mm[2], { 20 - 20, -20 }, G_ANGLE_UF016_DEG (-30) },
#define RADAR_SENSOR_BACK 3
      { &usdist_mm[3], { -30 - 20, 0 }, G_ANGLE_UF016_DEG (180) },
};

/** Define exclusion area (considered as invalid point). */
static uint8_t
radar_valid (vect_t p)
{
    return p.x >= RADAR_MARGIN_MM && p.x < PG_WIDTH - RADAR_MARGIN_MM
	&& p.y >= RADAR_MARGIN_MM && p.y < PG_LENGTH - RADAR_MARGIN_MM
	/* Ignore points on slope, no margin for the slope start. */
	&& (p.x < PG_WIDTH / 2 - PG_SLOPE_WIDTH / 2
	    || p.x >= PG_WIDTH / 2 + PG_SLOPE_WIDTH / 2
	    || p.y < PG_LENGTH - PG_SLOPE_LENGTH - RADAR_MARGIN_MM / 2);
}

uint8_t
radar_update (const position_t *robot_pos, vect_t *obs_pos)
{
    uint8_t i, j;
    vect_t ray;
    uint8_t obs_nb = 0;
    uint8_t front_nb;
    vect_t front_center;
    /* Compute hit points for each sensor and eliminate invalid ones. */
    vect_t hit[UTILS_COUNT (radar_sensors)];
    uint8_t valid[UTILS_COUNT (radar_sensors)];
    uint16_t dist_mm[UTILS_COUNT (radar_sensors)];
    for (i = 0; i < UTILS_COUNT (radar_sensors); i++)
      {
	dist_mm[i] = *radar_sensors[i].dist_mm;
	if (dist_mm[i] != 0xffff)
	  {
	    hit[i] = radar_sensors[i].pos;
	    vect_rotate_uf016 (&hit[i], robot_pos->a);
	    vect_translate (&hit[i], &robot_pos->v);
	    vect_from_polar_uf016 (&ray, dist_mm[i],
				   robot_pos->a + radar_sensors[i].a);
	    vect_translate (&hit[i], &ray);
	    valid[i] = radar_valid (hit[i]);
	    vect_from_polar_uf016 (&ray, RADAR_OBSTACLE_RADIUS_MM,
				   robot_pos->a + radar_sensors[i].a);
	    vect_translate (&hit[i], &ray);
	  }
	else
	    valid[i] = 0;
      }
    /* Ignore sensor results too far from other sensors. */
    for (i = 0; i < UTILS_COUNT (radar_sensors) - 1; i++)
      {
	for (j = i + 1; valid[i] && j < UTILS_COUNT (radar_sensors); j++)
	  {
	    if (valid[j])
	      {
		if (dist_mm[i] + RADAR_FAR_MM < dist_mm[j])
		    valid[j] = 0;
		else if (dist_mm[j] + RADAR_FAR_MM < dist_mm[i])
		    valid[i] = 0;
	      }
	  }
      }
    /* Specific treatment about sensor topology. */
    if (valid[RADAR_SENSOR_BACK])
	obs_pos[obs_nb++] = hit[RADAR_SENSOR_BACK];
    front_nb = 0;
    front_center.x = 0; front_center.y = 0;
    for (i = RADAR_SENSOR_FRONT; i < RADAR_SENSOR_BACK; i++)
      {
	if (valid[i])
	  {
	    vect_add (&front_center, &hit[i]);
	    front_nb++;
	  }
      }
    if (front_nb)
      {
	vect_scale_f824 (&front_center, 0x1000000l / front_nb);
	obs_pos[obs_nb++] = front_center;
      }
    /* Done. */
    return obs_nb;
}