/*
 * This file is part of ELKI:
 * Environment for Developing KDD-Applications Supported by Index-Structures
 *
 * Copyright (C) 2022
 * ELKI Development Team
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package elki.utilities.optionhandling.constraints;

import elki.utilities.optionhandling.ParameterException;

/**
 * Interface for specifying parameter constraints.
 * <p>
 * Each class specifying a constraint addressing only one parameter should
 * implement this interface.
 * The constraint value for testing the parameter should be defined as private
 * attribute and should be initialized in the respective constructor of the
 * class, i.e. it is a parameter of the constructor. The proper constraint
 * test should be implemented in the method {@link #test(Object) test(T)}.
 *
 * @author Steffi Wanka
 * @since 0.1
 * @param <T> the type of the parameter the constraint applies to
 */
public interface ParameterConstraint<T> {
  /**
   * Checks if the value {@code t} of the parameter to be tested fulfills the
   * parameter constraint. If not, a parameter exception is thrown.
   *
   * @param t Value to be checked whether or not it fulfills the underlying
   *        parameter constraint.
   * @throws ParameterException if the parameter to be tested does not
   *         fulfill the parameter constraint
   */
  void test(T t) throws ParameterException;

  /**
   * Returns a description of this constraint.
   *
   * @param parameterName the name of the parameter this constraint is used for
   * @return a description of this constraint
   */
  String getDescription(String parameterName);
}
