/*
 * 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.distance;

import elki.data.type.SimpleTypeInformation;
import elki.database.query.distance.DistanceQuery;
import elki.database.query.distance.PrimitiveDistanceQuery;
import elki.database.relation.Relation;

/**
 * Primitive distance function that is defined on some kind of object.
 * 
 * @author Erich Schubert
 * @since 0.4.0
 * 
 * @opt nodefillcolor LemonChiffon
 * 
 * @param <O> input object type
 */
public interface PrimitiveDistance<O> extends Distance<O> {
  /**
   * Computes the distance between two given DatabaseObjects according to this
   * distance function.
   * 
   * @param o1 first DatabaseObject
   * @param o2 second DatabaseObject
   * @return the distance between two given DatabaseObjects according to this
   *         distance function
   */
  double distance(O o1, O o2);

  @Override
  SimpleTypeInformation<? super O> getInputTypeRestriction();

  @Override
  default <T extends O> DistanceQuery<T> instantiate(Relation<T> relation) {
    return new PrimitiveDistanceQuery<>(relation, this);
  }
}
