package org.eclipse.aether.internal.impl;
   
   /*
    * 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.
   */
  
  import org.eclipse.aether.RepositorySystemSession;
  import org.eclipse.aether.spi.connector.ArtifactDownload;
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmFactory;
  import org.eclipse.aether.spi.connector.checksum.ProvidedChecksumsSource;
  import org.eclipse.aether.spi.io.FileProcessor;
  import org.eclipse.aether.util.ConfigUtils;
  import org.eclipse.aether.util.artifact.ArtifactIdUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  import java.io.IOException;
  import java.net.URI;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Local filesystem backed {@link ProvidedChecksumsSource} implementation that use specified directory as base
   * directory, where it expects artifacts checksums on standard Maven2 "local" layout. This implementation uses Artifact
   * (and Metadata) coordinates solely to form path from baseDir (for Metadata file name is
   * {@code maven-metadata-local.xml.sha1} in case of SHA-1 checksum).
   *
   * @since 1.8.0
   */
  @Singleton
  @Named( FileProvidedChecksumsSource.NAME )
  public final class FileProvidedChecksumsSource
      implements ProvidedChecksumsSource
  {
      public static final String NAME = "file";
  
      static final String CONFIG_PROP_BASE_DIR = "aether.artifactResolver.providedChecksumsSource.file.baseDir";
  
      static final String LOCAL_REPO_PREFIX = ".checksums";
  
      private static final Logger LOGGER = LoggerFactory.getLogger( FileProvidedChecksumsSource.class );
  
      private final FileProcessor fileProcessor;
  
      private final LocalPathComposer localPathComposer;
  
      @Inject
      public FileProvidedChecksumsSource( FileProcessor fileProcessor, LocalPathComposer localPathComposer )
      {
          this.fileProcessor = requireNonNull( fileProcessor );
          this.localPathComposer = requireNonNull( localPathComposer );
      }
  
      @Override
      public Map<String, String> getProvidedArtifactChecksums( RepositorySystemSession session,
                                                               ArtifactDownload transfer,
                                                               List<ChecksumAlgorithmFactory> checksumAlgorithmFactories )
      {
          Path baseDir = getBaseDir( session );
          if ( baseDir == null )
          {
              return null;
          }
          ArrayList<ChecksumFilePath> checksumFilePaths = new ArrayList<>( checksumAlgorithmFactories.size() );
          for ( ChecksumAlgorithmFactory checksumAlgorithmFactory : checksumAlgorithmFactories )
          {
              checksumFilePaths.add( new ChecksumFilePath(
                      localPathComposer.getPathForArtifact( transfer.getArtifact(), false ) + '.'
                      + checksumAlgorithmFactory.getFileExtension(), checksumAlgorithmFactory ) );
          }
          return getProvidedChecksums( baseDir, checksumFilePaths, ArtifactIdUtils.toId( transfer.getArtifact() ) );
      }
  
      /**
      * May return {@code null}.
      */
     private Map<String, String> getProvidedChecksums( Path baseDir,
                                                       List<ChecksumFilePath> checksumFilePaths,
                                                       String subjectId )
     {
         HashMap<String, String> checksums = new HashMap<>();
         for ( ChecksumFilePath checksumFilePath : checksumFilePaths )
         {
             Path checksumPath =  baseDir.resolve( checksumFilePath.path );
             if ( Files.isReadable( checksumPath ) )
             {
                 try
                 {
                     String checksum = fileProcessor.readChecksum( checksumPath.toFile() );
                     if ( checksum != null )
                     {
                         LOGGER.debug( "Resolved provided checksum '{}:{}' for '{}'",
                                 checksumFilePath.checksumAlgorithmFactory.getName(), checksum, subjectId );
 
                         checksums.put( checksumFilePath.checksumAlgorithmFactory.getName(), checksum );
                     }
                 }
                 catch ( IOException e )
                 {
                     LOGGER.warn( "Could not read provided checksum for '{}' at path '{}'",
                             subjectId, checksumPath, e );
                 }
             }
         }
         return checksums.isEmpty() ? null : checksums;
     }
 
     /**
      * Returns the base {@link URI} of directory where checksums are laid out, may return {@code null}.
      */
     private Path getBaseDir( RepositorySystemSession session )
     {
         final String baseDirPath = ConfigUtils.getString( session, null, CONFIG_PROP_BASE_DIR );
         final Path baseDir;
         if ( baseDirPath != null )
         {
             baseDir = Paths.get( baseDirPath );
         }
         else
         {
             baseDir = session.getLocalRepository().getBasedir().toPath().resolve( LOCAL_REPO_PREFIX );
         }
         if ( !Files.isDirectory( baseDir ) )
         {
             return null;
         }
         return baseDir;
     }
 
     private static final class ChecksumFilePath
     {
         private final String path;
 
         private final ChecksumAlgorithmFactory checksumAlgorithmFactory;
 
         private ChecksumFilePath( String path, ChecksumAlgorithmFactory checksumAlgorithmFactory )
         {
             this.path = path;
             this.checksumAlgorithmFactory = checksumAlgorithmFactory;
         }
     }
 }