/*
 * RiskScape™ Copyright New Zealand Institute for Earth Science Limited
 * (Earth Sciences New Zealand) is distributed for research purposes only
 * under the terms of AGPLv3.
 *
 * RiskScape™ Copyright 2026 New Zealand Institute for Earth Science
 * Limited (Earth Sciences New Zealand). All rights reserved. Source code
 * available under the AGPLv3.
 * 
 * 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 for RESEARCH PURPOSES ONLY, in the hope that it will
 * be useful for research and education initiatives.
 * 
 * If you are not a researcher, or you are a researcher who wishes to use this
 * program on terms other than AGPLv3 (including those who wish to restrict the
 * distribution of any source code created using this program), please contact:
 * https://riskscape.org.nz
 * 
 * This program is distributed 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/>.
 * 
 * By way of summary only, under the AGPLv3:
 *     • Permissions of this strongest copyleft license are conditioned
 *       on making available complete source code of licensed works and
 *       modifications, which include larger works using a licensed work,
 *       under the same license.
 *     • Copyright and license notices must be preserved.
 *     • Contributors provide an express grant of patent rights.
 *     • When a modified version is used to provide a service over a
 *       network, the complete source code of the modified version must be made
 *       available.
 */
package nz.org.riskscape.engine.util;

import java.util.Map;
import java.util.stream.Collector;
import java.util.stream.Collectors;

import lombok.Data;

/**
 * General purpose pair type
 */
@Data
public final class Pair<L, R> {

  /**
   * Construct a new pair in a slightly nicer way that using the constructor e.g.
   * `Pair.of(foo, bar)` vs `new Pair<>(foo, bar)`
   */
  public static <L, R> Pair<L, R> of(L l, R r) {
    return new Pair<L, R>(l, r);
  }

  /**
   * Returns a collector that can be used to reduce a stream of {@link Pair}s to a map, throwing an exception on
   * duplicates.
   *
   * @param <K> the type of keys
   * @param <V> the type of values
   * @return a map that is the result of mapping every pair's left side to its right side
   */
  public static <K, V> Collector<Pair<K, V>, ?, Map<K, V>> toMap() {
    return Collectors.toMap(pair -> pair.getLeft(), pair -> pair.getRight());
  }

  private final L left;
  private final R right;

}
