/*
    * Copyright (C) 2011, Google Inc. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.internal.storage.dfs;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import java.util.Arrays;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.internal.storage.pack.PackExt;
  
  /**
   * Key used by {@link org.eclipse.jgit.internal.storage.dfs.DfsBlockCache} to disambiguate streams.
   */
  public abstract class DfsStreamKey {
  	/**
  	 * Create a {@code DfsStreamKey}
  	 *
  	 * @param repo
  	 *            description of the containing repository.
  	 * @param name
  	 *            compute the key from a string name.
  	 * @param ext
  	 *            pack file extension, or {@code null}.
  	 * @return key for {@code name}
  	 */
  	public static DfsStreamKey of(DfsRepositoryDescription repo, String name,
  			@Nullable PackExt ext) {
  		return new ByteArrayDfsStreamKey(repo, name.getBytes(UTF_8), ext);
  	}
  
  	final int hash;
  
  	final int packExtPos;
  
  	/**
  	 * Constructor for DfsStreamKey.
  	 *
  	 * @param hash
  	 *            hash of the other identifying components of the key.
  	 * @param ext
  	 *            pack file extension, or {@code null}.
  	 */
  	protected DfsStreamKey(int hash, @Nullable PackExt ext) {
  		// Multiply by 31 here so we can more directly combine with another
  		// value without doing the multiply there.
  		this.hash = hash * 31;
  		this.packExtPos = ext == null ? 0 : ext.getPosition();
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public int hashCode() {
  		return hash;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public abstract boolean equals(Object o);
  
  	/** {@inheritDoc} */
  	@SuppressWarnings("boxing")
  	@Override
  	public String toString() {
  		return String.format("DfsStreamKey[hash=%08x]", hash); //$NON-NLS-1$
  	}
  
  	private static final class ByteArrayDfsStreamKey extends DfsStreamKey {
  		private final DfsRepositoryDescription repo;
  
  		private final byte[] name;
  
  		ByteArrayDfsStreamKey(DfsRepositoryDescription repo, byte[] name,
  				@Nullable PackExt ext) {
  			super(repo.hashCode() * 31 + Arrays.hashCode(name), ext);
  			this.repo = repo;
  			this.name = name;
  		}
  
  		@Override
  		public boolean equals(Object o) {
  			if (o instanceof ByteArrayDfsStreamKey) {
  				ByteArrayDfsStreamKey k = (ByteArrayDfsStreamKey) o;
  				return hash == k.hash && repo.equals(k.repo)
  						&& Arrays.equals(name, k.name);
  			}
  			return false;
  		}
  	}
  
  	static final class ForReverseIndex extends DfsStreamKey {
 		private final DfsStreamKey idxKey;
 
 		ForReverseIndex(DfsStreamKey idxKey) {
 			super(idxKey.hash + 1, null);
 			this.idxKey = idxKey;
 		}
 
 		@Override
 		public boolean equals(Object o) {
 			return o instanceof ForReverseIndex
 					&& idxKey.equals(((ForReverseIndex) o).idxKey);
 		}
 	}
 }