package net.bmahe.genetics4j.neat;
   
   import java.util.List;
   import java.util.Objects;
   import java.util.concurrent.ConcurrentHashMap;
   
   import net.bmahe.genetics4j.neat.spec.NeatNodeLayout;
   
   /**
   * Maintains one population-scoped {@link NodeIdManager} per semantic node layout.
   *
   * <p>Layouts are keyed by their ordered input IDs, ordered output IDs, and hidden-node range rather than their concrete
   * implementation class. Semantically equivalent layout implementations therefore share allocation history.
   */
  public class NodeIdManagerRegistry {
  
  	private record LayoutKey(List<Integer> inputNodeIds, List<Integer> outputNodeIds, long hiddenStart, long hiddenEnd) {
  		private LayoutKey(final NeatNodeLayout layout) {
  			this(List.copyOf(layout.inputNodeIds()),
  					List.copyOf(layout.outputNodeIds()),
  					layout.hiddenNodeIdStartInclusive(),
  					layout.hiddenNodeIdEndExclusive());
  		}
  	}
  
  	private final ConcurrentHashMap<LayoutKey, NodeIdManager> managers = new ConcurrentHashMap<>();
  
  	/**
  	 * Returns the shared node-ID manager for a layout, creating it when first requested.
  	 *
  	 * @param nodeLayout node layout used by a population
  	 * @return the shared manager for the layout's semantic key
  	 * @throws NullPointerException if {@code nodeLayout} is {@code null}
  	 */
  	public NodeIdManager managerFor(final NeatNodeLayout nodeLayout) {
  		Objects.requireNonNull(nodeLayout);
  		return managers.computeIfAbsent(new LayoutKey(nodeLayout), ignored -> new NodeIdManager(nodeLayout));
  	}
  }