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/**
 * @file followme.cpp
 *
 * Helper class to track and follow a given position
 *
 * @author Jimmy Johnson <catch22@fastmail.net>
 */

#include "follow_target.h"

#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <fcntl.h>

#include <systemlib/err.h>

#include <uORB/uORB.h>
#include <uORB/topics/position_setpoint_triplet.h>
#include <uORB/topics/follow_target.h>
#include <lib/ecl/geo/geo.h>
#include <lib/mathlib/math/Limits.hpp>

#include "navigator.h"

using namespace matrix;

constexpr float FollowTarget::_follow_position_matricies[4][9];

FollowTarget::FollowTarget(Navigator *navigator) :
	MissionBlock(navigator),
	ModuleParams(navigator)
{
	_current_vel.zero();
	_step_vel.zero();
	_est_target_vel.zero();
	_target_distance.zero();
	_target_position_offset.zero();
	_target_position_delta.zero();
}

void FollowTarget::on_inactive()
{
	reset_target_validity();
}

void FollowTarget::on_activation()
{
	_follow_offset = _param_nav_ft_dst.get() < 1.0F ? 1.0F : _param_nav_ft_dst.get();

	_responsiveness = math::constrain((float) _param_nav_ft_rs.get(), .1F, 1.0F);

	_follow_target_position = _param_nav_ft_fs.get();

	if ((_follow_target_position > FOLLOW_FROM_LEFT) || (_follow_target_position < FOLLOW_FROM_RIGHT)) {
		_follow_target_position = FOLLOW_FROM_BEHIND;
	}

	_rot_matrix = Dcmf(_follow_position_matricies[_follow_target_position]);
}

void FollowTarget::on_active()
{
	struct map_projection_reference_s target_ref;
	follow_target_s target_motion_with_offset = {};
	uint64_t current_time = hrt_absolute_time();
	bool radius_entered = false;
	bool radius_exited = false;
	bool updated = false;
	float dt_ms = 0;

	if (_follow_target_sub.updated()) {
		updated = true;
		follow_target_s target_motion;

		_target_updates++;

		// save last known motion topic for interpolation later

		_previous_target_motion = _current_target_motion;

		_follow_target_sub.copy(&target_motion);

		if (_current_target_motion.timestamp == 0) {
			_current_target_motion = target_motion;
		}

		_current_target_motion = target_motion;
		_current_target_motion.lat = (_current_target_motion.lat * (double)_responsiveness) + target_motion.lat * (double)(
						     1 - _responsiveness);
		_current_target_motion.lon = (_current_target_motion.lon * (double)_responsiveness) + target_motion.lon * (double)(
						     1 - _responsiveness);

	} else if (((current_time - _current_target_motion.timestamp) / 1000) > TARGET_TIMEOUT_MS && target_velocity_valid()) {
		reset_target_validity();
	}

	// update distance to target

	if (target_position_valid()) {

		// get distance to target

		map_projection_init(&target_ref, _navigator->get_global_position()->lat, _navigator->get_global_position()->lon);
		map_projection_project(&target_ref, _current_target_motion.lat, _current_target_motion.lon, &_target_distance(0),
				       &_target_distance(1));

	}

	// update target velocity

	if (target_velocity_valid() && updated) {

		dt_ms = ((_current_target_motion.timestamp - _previous_target_motion.timestamp) / 1000);

		// ignore a small dt
		if (dt_ms > 10.0F) {
			// get last gps known reference for target
			map_projection_init(&target_ref, _previous_target_motion.lat, _previous_target_motion.lon);

			// calculate distance the target has moved
			map_projection_project(&target_ref, _current_target_motion.lat, _current_target_motion.lon,
					       &(_target_position_delta(0)), &(_target_position_delta(1)));

			// update the average velocity of the target based on the position
			if (PX4_ISFINITE(_current_target_motion.vx) && PX4_ISFINITE(_current_target_motion.vy)) {
				// No need to estimate target velocity if we can take it from the target
				_est_target_vel(0) = _current_target_motion.vx;
				_est_target_vel(1) = _current_target_motion.vy;
				_est_target_vel(2) = 0.0f;

			} else {
				_est_target_vel = _target_position_delta / (dt_ms / 1000.0f);
			}

			// if the target is moving add an offset and rotation
			if (_est_target_vel.length() > .5F) {
				_target_position_offset = _rot_matrix * _est_target_vel.normalized() * _follow_offset;
			}

			// are we within the target acceptance radius?
			// give a buffer to exit/enter the radius to give the velocity controller
			// a chance to catch up

			radius_exited = ((_target_position_offset + _target_distance).length() > (float) TARGET_ACCEPTANCE_RADIUS_M * 1.5f);
			radius_entered = ((_target_position_offset + _target_distance).length() < (float) TARGET_ACCEPTANCE_RADIUS_M);

			// to keep the velocity increase/decrease smooth
			// calculate how many velocity increments/decrements
			// it will take to reach the targets velocity
			// with the given amount of steps also add a feed forward input that adjusts the
			// velocity as the position gap increases since
			// just traveling at the exact velocity of the target will not
			// get any closer or farther from the target

			_step_vel = (_est_target_vel - _current_vel) + (_target_position_offset + _target_distance) * FF_K;
			_step_vel /= (dt_ms / 1000.0F * (float) INTERPOLATION_PNTS);
			_step_time_in_ms = (dt_ms / (float) INTERPOLATION_PNTS);

			// if we are less than 1 meter from the target don't worry about trying to yaw
			// lock the yaw until we are at a distance that makes sense

			if ((_target_distance).length() > 1.0F) {

				// yaw rate smoothing

				// this really needs to control the yaw rate directly in the attitude pid controller
				// but seems to work ok for now since the yaw rate cannot be controlled directly in auto mode

				_yaw_angle = get_bearing_to_next_waypoint(_navigator->get_global_position()->lat,
						_navigator->get_global_position()->lon,
						_current_target_motion.lat,
						_current_target_motion.lon);

				_yaw_rate = wrap_pi((_yaw_angle - _navigator->get_local_position()->heading) / (dt_ms / 1000.0f));

			} else {
				_yaw_angle = _yaw_rate = NAN;
			}
		}

//		warnx(" _step_vel x %3.6f y %3.6f cur vel %3.6f %3.6f tar vel %3.6f %3.6f dist = %3.6f (%3.6f) mode = %d yaw rate = %3.6f",
//				(double) _step_vel(0),
//				(double) _step_vel(1),
//				(double) _current_vel(0),
//				(double) _current_vel(1),
//				(double) _est_target_vel(0),
//				(double) _est_target_vel(1),
//				(double) (_target_distance).length(),
//				(double) (_target_position_offset + _target_distance).length(),
//				_follow_target_state,
//				(double) _yaw_rate);
	}

	if (target_position_valid()) {

		// get the target position using the calculated offset

		map_projection_init(&target_ref,  _current_target_motion.lat, _current_target_motion.lon);
		map_projection_reproject(&target_ref, _target_position_offset(0), _target_position_offset(1),
					 &target_motion_with_offset.lat, &target_motion_with_offset.lon);
	}

	// clamp yaw rate smoothing if we are with in
	// 3 degrees of facing target

	if (PX4_ISFINITE(_yaw_rate)) {
		if (fabsf(fabsf(_yaw_angle) - fabsf(_navigator->get_local_position()->heading)) < math::radians(3.0F)) {
			_yaw_rate = NAN;
		}
	}

	// update state machine

	switch (_follow_target_state) {

	case TRACK_POSITION: {

			if (radius_entered) {
				_follow_target_state = TRACK_VELOCITY;

			} else if (target_velocity_valid()) {
				set_follow_target_item(&_mission_item, _param_nav_min_ft_ht.get(), target_motion_with_offset, _yaw_angle);
				// keep the current velocity updated with the target velocity for when it's needed
				_current_vel = _est_target_vel;

				update_position_sp(true, true, _yaw_rate);

			} else {
				_follow_target_state = SET_WAIT_FOR_TARGET_POSITION;
			}

			break;
		}

	case TRACK_VELOCITY: {

			if (radius_exited) {
				_follow_target_state = TRACK_POSITION;

			} else if (target_velocity_valid()) {

				if ((float)(current_time - _last_update_time) / 1000.0f >= _step_time_in_ms) {
					_current_vel += _step_vel;
					_last_update_time = current_time;
				}

				set_follow_target_item(&_mission_item, _param_nav_min_ft_ht.get(), target_motion_with_offset, _yaw_angle);

				update_position_sp(true, false, _yaw_rate);

			} else {
				_follow_target_state = SET_WAIT_FOR_TARGET_POSITION;
			}

			break;
		}

	case SET_WAIT_FOR_TARGET_POSITION: {

			// Climb to the minimum altitude
			// and wait until a position is received

			follow_target_s target = {};

			// for now set the target at the minimum height above the uav

			target.lat = _navigator->get_global_position()->lat;
			target.lon = _navigator->get_global_position()->lon;
			target.alt = 0.0F;

			set_follow_target_item(&_mission_item, _param_nav_min_ft_ht.get(), target, _yaw_angle);

			update_position_sp(false, false, _yaw_rate);

			_follow_target_state = WAIT_FOR_TARGET_POSITION;
		}

	/* FALLTHROUGH */

	case WAIT_FOR_TARGET_POSITION: {

			if (is_mission_item_reached() && target_velocity_valid()) {
				_target_position_offset(0) = _follow_offset;
				_follow_target_state = TRACK_POSITION;
			}

			break;
		}
	}
}

void FollowTarget::update_position_sp(bool use_velocity, bool use_position, float yaw_rate)
{
	// convert mission item to current setpoint

	struct position_setpoint_triplet_s *pos_sp_triplet = _navigator->get_position_setpoint_triplet();

	// activate line following in pos control if position is valid

	pos_sp_triplet->previous.valid = use_position;
	pos_sp_triplet->previous = pos_sp_triplet->current;
	mission_apply_limitation(_mission_item);
	mission_item_to_position_setpoint(_mission_item, &pos_sp_triplet->current);
	pos_sp_triplet->current.type = position_setpoint_s::SETPOINT_TYPE_FOLLOW_TARGET;
	pos_sp_triplet->current.velocity_valid = use_velocity;
	pos_sp_triplet->current.vx = _current_vel(0);
	pos_sp_triplet->current.vy = _current_vel(1);
	pos_sp_triplet->next.valid = false;
	pos_sp_triplet->current.yawspeed_valid = PX4_ISFINITE(yaw_rate);
	pos_sp_triplet->current.yawspeed = yaw_rate;
	_navigator->set_position_setpoint_triplet_updated();
}

void FollowTarget::reset_target_validity()
{
	_yaw_rate = NAN;
	_previous_target_motion = {};
	_current_target_motion = {};
	_target_updates = 0;
	_current_vel.zero();
	_step_vel.zero();
	_est_target_vel.zero();
	_target_distance.zero();
	_target_position_offset.zero();
	reset_mission_item_reached();
	_follow_target_state = SET_WAIT_FOR_TARGET_POSITION;
}

bool FollowTarget::target_velocity_valid()
{
	// need at least 2 continuous data points for velocity estimate
	return (_target_updates >= 2);
}

bool FollowTarget::target_position_valid()
{
	// need at least 1 continuous data points for position estimate
	return (_target_updates >= 1);
}

void
FollowTarget::set_follow_target_item(struct mission_item_s *item, float min_clearance, follow_target_s &target,
				     float yaw)
{
	if (_navigator->get_land_detected()->landed) {
		/* landed, don't takeoff, but switch to IDLE mode */
		item->nav_cmd = NAV_CMD_IDLE;

	} else {

		item->nav_cmd = NAV_CMD_DO_FOLLOW_REPOSITION;

		/* use current target position */
		item->lat = target.lat;
		item->lon = target.lon;
		item->altitude = _navigator->get_home_position()->alt;

		if (min_clearance > 8.0f) {
			item->altitude += min_clearance;

		} else {
			item->altitude += 8.0f; // if min clearance is bad set it to 8.0 meters (well above the average height of a person)
		}
	}

	item->altitude_is_relative = false;
	item->yaw = yaw;
	item->loiter_radius = _navigator->get_loiter_radius();
	item->acceptance_radius = _navigator->get_acceptance_radius();
	item->time_inside = 0.0f;
	item->autocontinue = false;
	item->origin = ORIGIN_ONBOARD;
}