// ******************************************************************************
   //
   // 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
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  // 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.potential.terms;
  
  import ffx.potential.bonded.BondedTerm;
  import ffx.potential.bonded.TorsionTorsion;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.logging.Logger;
  
  /**
   * Torsion-Torsion potential energy term using {@link ffx.potential.bonded.TorsionTorsion} instances.
   *
   * @author Michael J. Schnieders
   * @since 1.0
   */
  public class TorsionTorsionPotentialEnergy extends EnergyTerm {
  
    private static final Logger logger = Logger.getLogger(TorsionTorsionPotentialEnergy.class.getName());
  
  
    /**
     * Internal list of TorsionTorsion instances.
     */
    private final List<TorsionTorsion> torsionTorsions = new ArrayList<>();
  
    /**
     * Create a TorsionTorsionPotentialEnergy with the provided name.
     *
     * @param name Name for this term.
     */
    public TorsionTorsionPotentialEnergy(String name) {
      super(name);
    }
  
    /**
     * Create a TorsionTorsionPotentialEnergy with the provided name and force group.
     *
     * @param name       Name for this term.
     * @param forceGroup Integer force group identifier.
     */
    public TorsionTorsionPotentialEnergy(String name, int forceGroup) {
      super(name, forceGroup);
    }
  
    /**
     * Create a TorsionTorsionPotentialEnergy initialized with a list of terms and force group.
     *
     * @param name            Name for this term.
     * @param forceGroup      Force group identifier.
     * @param torsionTorsions List of TorsionTorsion instances to add (null-safe).
     */
    public TorsionTorsionPotentialEnergy(String name, int forceGroup, List<TorsionTorsion> torsionTorsions) {
      super(name, forceGroup);
      if (torsionTorsions != null) {
        Collections.sort(torsionTorsions);
        this.torsionTorsions.addAll(torsionTorsions);
        logger.info(String.format("  Torsion-Torsions:                  %10d", getNumberOfTorsionTorsions()));
      }
    }
  
   /**
    * {@inheritDoc}
    */
   @Override
   public int getNumberOfTerms() {
     return getNumberOfTorsionTorsions();
   }
 
   /**
    * {@inheritDoc}
    */
   @Override
   public BondedTerm[] getBondedTermsArray() {
     return getTorsionTorsionArray();
   }
 
   /**
    * Create a TorsionTorsionPotentialEnergy initialized with a collection of terms.
    *
    * @param name            Name for this term (may be null).
    * @param torsionTorsions Collection of TorsionTorsion instances to add (null-safe).
    */
   public TorsionTorsionPotentialEnergy(String name, Collection<TorsionTorsion> torsionTorsions) {
     super(name);
     if (torsionTorsions != null) {
       this.torsionTorsions.addAll(torsionTorsions);
     }
   }
 
   /**
    * Add a TorsionTorsion to this term.
    *
    * @param torsionTorsion TorsionTorsion to add (ignored if null).
    * @return true if it was added.
    */
   public boolean addTorsionTorsion(TorsionTorsion torsionTorsion) {
     if (torsionTorsion == null) {
       return false;
     }
     return torsionTorsions.add(torsionTorsion);
   }
 
   /**
    * Add an array of TorsionTorsions to this term.
    *
    * @param torsionTorsions Array of TorsionTorsion instances to add.
    * @return true if they were added.
    */
   public boolean addTorsionTorsions(TorsionTorsion[] torsionTorsions) {
     if (torsionTorsions == null) {
       return false;
     }
     Collections.addAll(this.torsionTorsions, torsionTorsions);
     return true;
   }
 
   /**
    * Add a list of TorsionTorsions to this term.
    *
    * @param torsionTorsions List of TorsionTorsion instances to add.
    * @return true if they were added.
    */
   public boolean addTorsionTorsions(List<TorsionTorsion> torsionTorsions) {
     if (torsionTorsions == null) {
       return false;
     }
     this.torsionTorsions.addAll(torsionTorsions);
     return true;
   }
 
   /**
    * Remove a TorsionTorsion from this term.
    *
    * @param torsionTorsion TorsionTorsion to remove (ignored if null).
    * @return true if it was present and removed.
    */
   public boolean removeTorsionTorsion(TorsionTorsion torsionTorsion) {
     if (torsionTorsion == null) {
       return false;
     }
     return torsionTorsions.remove(torsionTorsion);
   }
 
   /**
    * Get the TorsionTorsion at a given index.
    *
    * @param index Index in the internal list.
    * @return TorsionTorsion at the specified index.
    * @throws IndexOutOfBoundsException if index is invalid.
    */
   public TorsionTorsion getTorsionTorsion(int index) {
     return torsionTorsions.get(index);
   }
 
   /**
    * Get an unmodifiable view of the TorsionTorsions in this term.
    *
    * @return Unmodifiable List of TorsionTorsions.
    */
   public List<TorsionTorsion> getTorsionTorsions() {
     return Collections.unmodifiableList(torsionTorsions);
   }
 
   /**
    * Get an array of TorsionTorsions in this term.
    *
    * @return Array of TorsionTorsions.
    */
   public TorsionTorsion[] getTorsionTorsionArray() {
     return torsionTorsions.toArray(new TorsionTorsion[0]);
   }
 
   /**
    * Get the number of TorsionTorsions in this term.
    *
    * @return The number of TorsionTorsions.
    */
   public int getNumberOfTorsionTorsions() {
     return torsionTorsions.size();
   }
 
   /**
    * Set the lambda value for all TorsionTorsions in this term.
    *
    * @param lambda The new lambda value to set.
    */
   public void setLambda(double lambda) {
     for (TorsionTorsion torsionTorsion : torsionTorsions) {
       torsionTorsion.setLambda(lambda);
     }
   }
 
   /**
    * Get the energy contribution from all Torsion-Torsions in this term.
    * @return Total energy from all Torsion-Torsions.
    */
   public double getdEdL() {
     double dEdL = 0.0;
     for (TorsionTorsion torsionTorsion : torsionTorsions) {
       dEdL += torsionTorsion.getdEdL();
     }
     return dEdL;
   }
 
   /**
    * Get the energy contribution from all Torsion-Torsions in this term.
    * @return Total energy from all Torsion-Torsions.
    */
   public double getd2EdL2() {
     double d2EdLambda2 = 0.0;
     for (TorsionTorsion torsionTorsion : torsionTorsions) {
       d2EdLambda2 += torsionTorsion.getd2EdL2();
     }
     return d2EdLambda2;
   }
 
   /**
    * Log the details of Torsion-Torsion interactions.
    */
   @Override
   public void log() {
     if (getNumberOfTorsionTorsions() <= 0) {
       return;
     }
     logger.info("\n Torsion-Torsion Interactions:");
     for (TorsionTorsion torsionTorsion : getTorsionTorsions()) {
       logger.info(" Torsion-Torsion \t" + torsionTorsion.toString());
     }
   }
 
   @Override
   public String toPDBString() {
     if (getNumberOfTorsionTorsions() <= 0) {
       return "";
     }
     return String.format("REMARK   3   %s %g (%d)\n", "TORSION-TORSION            : ", getEnergy(), getNumberOfTorsionTorsions());
   }
 
   @Override
   public String toString() {
     return String.format("  %s %20.8f %12d %12.3f\n", "Torsion-Torsion   ",
         getEnergy(), getNumberOfTorsionTorsions(), getTime());
   }
 }