// MagicCarpet.cxx -- interface to the "Magic Carpet" flight model
//
// Written by Curtis Olson, started October 1999.
//
// Copyright (C) 1999  Curtis L. Olson  - curt@flightgear.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., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// $Id$


#include <Controls/controls.hxx>
#include <Main/options.hxx>
#include <Math/fg_geodesy.hxx>
#include <Math/point3d.hxx>
#include <Math/polar3d.hxx>

#include "MagicCarpet.hxx"


// Initialize the Magic Carpet flight model, dt is the time increment
// for each subsequent iteration through the EOM
int FGMagicCarpet::init( double dt ) {
    // set valid time for this record
    stamp_time();

    return 1;
}


// Run an iteration of the EOM (equations of motion)
int FGMagicCarpet::update( int multiloop ) {
    // cout << "FGLaRCsim::update()" << endl;

    double time_step = (1.0 / current_options.get_model_hz()) * multiloop;

    // speed and distance traveled
    double speed = controls.get_throttle( 0 ) * 2000; // meters/sec
    double dist = speed * time_step;
    double kts = speed * METER_TO_NM * 3600.0;
    set_V_equiv_kts( kts );
    set_V_ground_speed( kts );

    // angle of turn
    double turn_rate = controls.get_aileron() * FG_PI_4; // radians/sec
    double turn = turn_rate * time_step;

    // update euler angles
    set_Euler_Angles( get_Phi(), get_Theta(), fmod(get_Psi() + turn, FG_2PI) );

    // update (lon/lat) position
    Point3D start( get_Longitude(), get_Latitude(), 0.0 );
    Point3D end = calc_lon_lat( start, -get_Psi(), dist );

    set_Longitude( end.x() );
    set_Latitude( end.y() );

    double sl_radius, lat_geoc;
    fgGeodToGeoc( get_Latitude(), get_Altitude(), &sl_radius, &lat_geoc );

    // update altitude
    double real_climb_rate = -controls.get_elevator() * 5000; // feet/sec
    set_Climb_Rate( real_climb_rate / 500.0 );
    double climb = real_climb_rate * time_step;

    set_Geocentric_Position( lat_geoc, get_Longitude(), 
			     sl_radius + get_Altitude() + climb );
    set_Geodetic_Position( end.y(), end.x(), 
			   get_Altitude() + climb );

    return 1;
}