/****************************************************************************
 *
 *   Copyright (C) 2008-2012 PX4 Development Team. All rights reserved.
 *   Author: @author Thomas Gubler <thomasgubler@student.ethz.ch>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/*
 * @file: landingslope.cpp
 *
 */

#include "landingslope.h"

#include <nuttx/config.h>
#include <stdlib.h>
#include <errno.h>
#include <math.h>
#include <unistd.h>
#include <mathlib/mathlib.h>

void Landingslope::update(float landing_slope_angle_rad_new,
		float flare_relative_alt_new,
		float motor_lim_relative_alt_new,
		float H1_virt_new)
{

	_landing_slope_angle_rad = landing_slope_angle_rad_new;
	_flare_relative_alt = flare_relative_alt_new;
	_motor_lim_relative_alt = motor_lim_relative_alt_new;
	_H1_virt = H1_virt_new;

	calculateSlopeValues();
}

void Landingslope::calculateSlopeValues()
{
	_H0 =  _flare_relative_alt + _H1_virt;
	_d1 = _flare_relative_alt/tanf(_landing_slope_angle_rad);
	_flare_constant = (_H0 * _d1)/_flare_relative_alt;
	_flare_length = - logf(_H1_virt/_H0) * _flare_constant;
	_horizontal_slope_displacement = (_flare_length - _d1);
}

float  Landingslope::getLandingSlopeRelativeAltitude(float wp_landing_distance)
{
	return Landingslope::getLandingSlopeRelativeAltitude(wp_landing_distance, _horizontal_slope_displacement, _landing_slope_angle_rad);
}

float Landingslope::getLandingSlopeRelativeAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp)
{
	/* If airplane is in front of waypoint return slope altitude, else return waypoint altitude */
	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f))
		return getLandingSlopeRelativeAltitude(wp_landing_distance);
	else
		return 0.0f;
}

float Landingslope::getLandingSlopeAbsoluteAltitude(float wp_landing_distance, float wp_altitude)
{
	return Landingslope::getLandingSlopeAbsoluteAltitude(wp_landing_distance, wp_altitude, _horizontal_slope_displacement, _landing_slope_angle_rad);
}

float Landingslope::getLandingSlopeAbsoluteAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp, float wp_altitude)
{
	/* If airplane is in front of waypoint return slope altitude, else return waypoint altitude */
	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f))
		return getLandingSlopeAbsoluteAltitude(wp_landing_distance, wp_altitude);
	else
		return wp_altitude;
}

float Landingslope::getFlareCurveRelativeAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp)
{
	/* If airplane is in front of waypoint return flare curve altitude, else return waypoint altitude */
	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f))
		return _H0 * expf(-math::max(0.0f, _flare_length - wp_landing_distance)/_flare_constant) - _H1_virt;
	else
		return 0.0f;
}

float Landingslope::getFlareCurveAbsoluteAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp, float bearing_airplane_currwp, float wp_landing_altitude)
{

	return wp_landing_altitude + getFlareCurveRelativeAltitudeSave(wp_landing_distance, bearing_lastwp_currwp, bearing_airplane_currwp);
}