// ******************************************************************************
   //
   // Title:       Force Field X.
   // Description: Force Field X - Software for Molecular Biophysics.
   // Copyright:   Copyright (c) Michael J. Schnieders 2001-2023.
   //
   // 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.parameters;
  
  import static ffx.potential.parameters.ForceField.ForceFieldType.CHARGE;
  import static ffx.utilities.KeywordGroup.PotentialFunctionParameter;
  import static java.lang.Integer.parseInt;
  import static java.lang.String.format;
  
  import ffx.utilities.FFXKeyword;
  import java.util.Comparator;
  
  /**
   * The ChargeType class defines a partial atomic charge type.
   *
   * @author Michael J. Schnieders
   * @since 1.0
   */
  @FFXKeyword(name = "charge", clazz = String.class, keywordGroup = PotentialFunctionParameter, description =
      "[1 integer and 1 real] "
          + "Provides a value for a single atomic partial charge electrostatic parameter. "
          + "The integer modifier, if positive, gives the atom type number for which the charge parameter is to be defined. "
          + "Note that charge parameters are given for atom types, not atom classes. "
          + "If the integer modifier is negative, then the parameter value to follow applies only to the individual atom whose atom number is the negative of the modifier. "
          + "The real number modifier gives the values of the atomic partial charge in electrons.")
  public final class ChargeType extends BaseType implements Comparator<String> {
  
    /** Partial atomic charge in units of electrons. */
    public final double charge;
    /** The atom type that uses this charge parameter. */
    public int atomType;
  
    /**
     * ChargeType constructor.
     *
     * @param atomType int
     * @param charge double
     */
    public ChargeType(int atomType, double charge) {
      super(CHARGE, "" + atomType);
      this.atomType = atomType;
      this.charge = charge;
    }
  
    /**
     * Average two ChargeType instances. The atom type that defines the new type must be supplied.
     *
     * @param chargeType1 a {@link ffx.potential.parameters.ChargeType} object.
     * @param chargeType2 a {@link ffx.potential.parameters.ChargeType} object.
     * @param atomType The atom type that defines the new type.
     * @return a {@link ffx.potential.parameters.ChargeType} object.
     */
    public static ChargeType average(ChargeType chargeType1, ChargeType chargeType2, int atomType) {
      if (chargeType1 == null || chargeType2 == null) {
        return null;
      }
      double charge = (chargeType1.charge + chargeType2.charge) / 2.0;
      return new ChargeType(atomType, charge);
    }
  
    /** {@inheritDoc} */
    @Override
    public int compare(String s1, String s2) {
      int t1 = parseInt(s1);
     int t2 = parseInt(s2);
     return Integer.compare(t1, t2);
   }
 
   /**
    * incrementType
    *
    * @param increment The amount to increment the atom type by.
    */
   public void incrementType(int increment) {
     this.atomType += increment;
   }
 
   /**
    * {@inheritDoc}
    *
    * <p>Nicely formatted Charge type.
    */
   @Override
   public String toString() {
     return format("charge  %5d  % 7.5f", atomType, charge);
   }
 }