#ifndef OPENMM_CMMOTIONREMOVER_H_
#define OPENMM_CMMOTIONREMOVER_H_

/* -------------------------------------------------------------------------- *
 *                                   OpenMM                                   *
 * -------------------------------------------------------------------------- *
 * This is part of the OpenMM molecular simulation toolkit.                   *
 * See https://openmm.org/development.                                        *
 *                                                                            *
 * Portions copyright (c) 2008-2021 Stanford University and the Authors.      *
 * Authors: Peter Eastman                                                     *
 * Contributors:                                                              *
 *                                                                            *
 * Permission is hereby granted, free of charge, to any person obtaining a    *
 * copy of this software and associated documentation files (the "Software"), *
 * to deal in the Software without restriction, including without limitation  *
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
 * and/or sell copies of the Software, and to permit persons to whom the      *
 * Software is furnished to do so, subject to the following conditions:       *
 *                                                                            *
 * The above copyright notice and this permission notice shall be included in *
 * all copies or substantial portions of the Software.                        *
 *                                                                            *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
 * THE AUTHORS, CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,    *
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR      *
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE  *
 * USE OR OTHER DEALINGS IN THE SOFTWARE.                                     *
 * -------------------------------------------------------------------------- */

#include "Force.h"
#include <string>
#include "internal/windowsExport.h"

namespace OpenMM {

/**
 * This class prevents the center of mass of a System from drifting.  It periodically calculates the
 * center of mass momentum, then adjusts the individual particle velocities to make it zero.
 *
 * CMMotionRemover is an effective way to prevent the system from drifting, but it is not a rigorous constraint.
 * The center of mass may still move slightly, and may still be observed to have a small nonzero velocity.
 */

class OPENMM_EXPORT CMMotionRemover : public Force {
public:
    /**
     * Create a CMMotionRemover.
     */
    explicit CMMotionRemover(int frequency = 1);
    /**
     * Get the frequency (in time steps) at which center of mass motion should be removed
     */
    int getFrequency() const {
        return frequency;
    }
    /**
     * Set the frequency (in time steps) at which center of mass motion should be removed
     */
    void setFrequency(int freq);
    /**
     * Returns whether or not this force makes use of periodic boundary
     * conditions.
     *
     * @returns true if force uses PBC and false otherwise
     */
    bool usesPeriodicBoundaryConditions() const {
        return false;
    }
protected:
    ForceImpl* createImpl() const;
private:
    int frequency;
};

} // namespace OpenMM

#endif /*OPENMM_CMMOTIONREMOVER_H_*/
