/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.eclipse.aether.internal.impl.synccontext.named;
  
  import java.util.Collection;
  import java.util.stream.Collectors;
  
  import org.eclipse.aether.RepositorySystemSession;
  import org.eclipse.aether.artifact.Artifact;
  import org.eclipse.aether.metadata.Metadata;
  import org.eclipse.aether.util.ConfigUtils;
  import org.eclipse.aether.util.StringDigestUtil;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Wrapping {@link NameMapper}, that wraps another {@link NameMapper} and hashes resulting strings. It makes use of
   * fact that (proper) Hash will create unique fixed length string for each different input string (so injection still
   * stands). This mapper produces file system friendly names. Supports different "depths" (0-4 inclusive) where the
   * name will contain 0 to 4 level deep directories.
   * <p>
   * This mapper is usable in any scenario, but intent was to produce more "compact" name mapper for file locking.
   *
   * @since 1.9.0
   */
  public class HashingNameMapper implements NameMapper {
      private static final String CONFIG_PROP_DEPTH = "aether.syncContext.named.hashing.depth";
  
      private final NameMapper delegate;
  
      public HashingNameMapper(final NameMapper delegate) {
          this.delegate = requireNonNull(delegate);
      }
  
      @Override
      public boolean isFileSystemFriendly() {
          return true; // hashes delegated strings, so whatever it wrapped, it does not come through
      }
  
      @Override
      public Collection<String> nameLocks(
              RepositorySystemSession session,
              Collection<? extends Artifact> artifacts,
              Collection<? extends Metadata> metadatas) {
          final int depth = ConfigUtils.getInteger(session, 2, CONFIG_PROP_DEPTH);
          if (depth < 0 || depth > 4) {
              throw new IllegalArgumentException("allowed depth value is between 0 and 4 (inclusive)");
          }
          return delegate.nameLocks(session, artifacts, metadatas).stream()
                  .map(n -> hashName(n, depth))
                  .collect(Collectors.toList());
      }
  
      private String hashName(final String name, final int depth) {
          String hashedName = StringDigestUtil.sha1(name);
          if (depth == 0) {
              return hashedName;
          }
          StringBuilder prefix = new StringBuilder("");
          int i = 0;
          while (i < hashedName.length() && i / 2 < depth) {
              prefix.append(hashedName, i, i + 2).append("/");
              i += 2;
          }
          return prefix.append(hashedName).toString();
      }
  }