// ******************************************************************************
   //
   // Title:       Force Field X.
   // Description: Force Field X - Software for Molecular Biophysics.
   // Copyright:   Copyright (c) Michael J. Schnieders 2001-2025.
   //
   // This file is part of Force Field X.
   //
   // Force Field X is free software; you can redistribute it and/or modify it
  // under the terms of the GNU General Public License version 3 as published by
  // the Free Software Foundation.
  //
  // Force Field X 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
  // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
  // Place, Suite 330, Boston, MA 02111-1307 USA
  //
  // Linking this library statically or dynamically with other modules is making a
  // combined work based on this library. Thus, the terms and conditions of the
  // GNU General Public License cover the whole combination.
  //
  // As a special exception, the copyright holders of this library give you
  // permission to link this library with independent modules to produce an
  // executable, regardless of the license terms of these independent modules, and
  // to copy and distribute the resulting executable under terms of your choice,
  // provided that you also meet, for each linked independent module, the terms
  // and conditions of the license of that module. An independent module is a
  // module which is not derived from or based on this library. If you modify this
  // library, you may extend this exception to your version of the library, but
  // you are not obligated to do so. If you do not wish to do so, delete this
  // exception statement from your version.
  //
  // ******************************************************************************
  package ffx.openmm;
  
  import com.sun.jna.Pointer;
  import com.sun.jna.ptr.PointerByReference;
  
  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Boolean.OpenMM_True;
  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Force_getForceGroup;
  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Force_getName;
  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Force_setForceGroup;
  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Force_setName;
  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Force_usesPeriodicBoundaryConditions;
  
  /**
   * Force objects apply forces to the particles in a System, or alter their behavior in other
   * ways. This is an abstract class. Subclasses define particular forces.
   * <p>
   * More specifically, a Force object can do any or all of the following:
   *
   * <ul>
   * <li>Add a contribution to the force on each particle</li>
   * <li>Add a contribution to the potential energy of the System</li>
   * <li>Modify the positions and velocities of particles at the start of each time step</li>
   * <li>Define parameters which are stored in the Context and can be modified by the user</li>
   * <li>Change the values of parameters defined by other Force objects at the start of each time step</li>
   * </ul>
   * <p>
   * Forces may be organized into "force groups". This is used for multiple time step integration,
   * and allows subsets of the Forces in a System to be evaluated at different times. By default,
   * all Forces are in group 0. Call setForceGroup() to change this. Some Force subclasses may
   * provide additional methods to further split their computations into multiple groups.  Be aware
   * that particular Platforms may place restrictions on the use of force groups, such as requiring
   * all nonbonded forces to be in the same group.
   */
  public abstract class Force {
  
    /**
     * The forcePointer is allocated and deallocated by classes that extend OpenMMForce.
     */
    protected PointerByReference pointer = null;
  
    /**
     * The forceIndex is returned by OpenMMSystem.addForce and is used to remove the force.
     */
    private int forceIndex = -1;
  
    /**
     * Get the pointer to the OpenMM Force.
     *
     * @return The pointer to the OpenMM Force.
     */
    public PointerByReference getPointer() {
      return pointer;
    }
  
    /**
     * Set the force group.
     *
     * @param forceGroup The force group.
     */
    public void setForceGroup(int forceGroup) {
      OpenMM_Force_setForceGroup(pointer, forceGroup);
    }
 
   /**
    * Get the force group.
    *
    * @return The force group.
    */
   public int getForceGroup() {
     return OpenMM_Force_getForceGroup(pointer);
   }
 
   /**
    * Set the name of the force.
    *
    * @param name The name of the force.
    */
   public void setName(String name) {
     OpenMM_Force_setName(pointer, name);
   }
 
   /**
    * Get the name of the force.
    *
    * @return The name of the force.
    */
   public String getName() {
     Pointer pointer = OpenMM_Force_getName(this.pointer);
     if (pointer == null) {
       return null;
     }
     return pointer.getString(0);
   }
 
   /**
    * Set the force index.
    *
    * @param forceIndex The force index.
    */
   public void setForceIndex(int forceIndex) {
     this.forceIndex = forceIndex;
   }
 
   /**
    * Get the force index.
    *
    * @return The force index.
    */
   public int getForceIndex() {
     return forceIndex;
   }
 
   /**
    * Check if the force use periodic boundary conditions. This is a virtual method
    * that must be implemented by classes that extend OpenMMForce.
    *
    * @return True if the force uses periodic boundary conditions.
    */
   public boolean usesPeriodicBoundaryConditions() {
     int pbc = OpenMM_Force_usesPeriodicBoundaryConditions(pointer);
     return pbc == OpenMM_True;
   }
 
 }