/* Copyright 2002-2017 CS Systèmes d'Information
 * Licensed to CS Systèmes d'Information (CS) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * CS licenses this file to You under the Apache License, Version 2.0
 * (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.orekit.propagation.numerical;

import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.errors.OrekitException;
import org.orekit.frames.Frame;

/** Interface summing up the contribution of several forces into orbit and mass derivatives.
 *
 * <p>The aim of this interface is to gather the contributions of various perturbing
 * forces expressed as accelerations into one set of time-derivatives of
 * {@link org.orekit.orbits.Orbit} plus one mass derivatives. It implements Gauss
 * equations for different kind of parameters.</p>
 * <p>An implementation of this interface is automatically provided by {@link
 * org.orekit.propagation.integration.AbstractIntegratedPropagator integration-based
 * propagators}, which are either semi-analytical or numerical propagators.
 * </p>
 * @see org.orekit.forces.ForceModel
 * @see org.orekit.propagation.numerical.NumericalPropagator
 * @author Luc Maisonobe
 * @author Fabien Maussion
 * @author Véronique Pommier-Maurussane
 */
public interface TimeDerivativesEquations {

    /** Add the contribution of the Kepler evolution.
     * <p>Since the Kepler evolution is the most important, it should
     * be added after all the other ones, in order to improve
     * numerical accuracy.</p>
     * @param mu central body gravitational constant
     */
    void addKeplerContribution(double mu);

    /** Add the contribution of an acceleration expressed in the inertial frame
     *  (it is important to make sure this acceleration is defined in the
     *  same frame as the orbit) .
     * @param x acceleration along the X axis (m/s²)
     * @param y acceleration along the Y axis (m/s²)
     * @param z acceleration along the Z axis (m/s²)
     */
    void addXYZAcceleration(double x, double y, double z);

    /** Add the contribution of an acceleration expressed in some inertial frame.
     * @param gamma acceleration vector (m/s²)
     * @param frame frame in which acceleration is defined (must be an inertial frame)
     * @exception OrekitException if frame transforms cannot be computed
     */
    void addAcceleration(Vector3D gamma, Frame frame) throws OrekitException;

    /** Add the contribution of the flow rate (dm/dt).
     * @param q the flow rate, must be negative (dm/dt)
     * @exception IllegalArgumentException if flow-rate is positive
     */
    void addMassDerivative(double q);


}