/*
    * 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.apache.maven.repository.internal;
  
  import javax.xml.stream.XMLStreamException;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.file.Files;
  import java.util.Collections;
  import java.util.Date;
  import java.util.Map;
  
  import org.apache.maven.artifact.repository.metadata.Metadata;
  import org.apache.maven.artifact.repository.metadata.io.MetadataStaxReader;
  import org.apache.maven.artifact.repository.metadata.io.MetadataStaxWriter;
  import org.eclipse.aether.RepositoryException;
  import org.eclipse.aether.metadata.AbstractMetadata;
  import org.eclipse.aether.metadata.MergeableMetadata;
  
  /**
   */
  abstract class MavenMetadata extends AbstractMetadata implements MergeableMetadata {
  
      static final String MAVEN_METADATA_XML = "maven-metadata.xml";
  
      protected Metadata metadata;
  
      private final File file;
  
      protected final Date timestamp;
  
      private boolean merged;
  
      protected MavenMetadata(Metadata metadata, File file, Date timestamp) {
          this.metadata = metadata;
          this.file = file;
          this.timestamp = timestamp;
      }
  
      @Override
      public String getType() {
          return MAVEN_METADATA_XML;
      }
  
      @Override
      public File getFile() {
          return file;
      }
  
      @Override
      public void merge(File existing, File result) throws RepositoryException {
          Metadata recessive = read(existing);
  
          merge(recessive);
  
          write(result, metadata);
  
          merged = true;
      }
  
      @Override
      public boolean isMerged() {
          return merged;
      }
  
      protected abstract void merge(Metadata recessive);
  
      static Metadata read(File metadataFile) throws RepositoryException {
          if (metadataFile.length() <= 0) {
              return new Metadata();
          }
  
          try (InputStream input = Files.newInputStream(metadataFile.toPath())) {
              return new Metadata(new MetadataStaxReader().read(input, false));
          } catch (IOException | XMLStreamException e) {
              throw new RepositoryException("Could not parse metadata " + metadataFile + ": " + e.getMessage(), e);
          }
      }
  
      private void write(File metadataFile, Metadata metadata) throws RepositoryException {
         metadataFile.getParentFile().mkdirs();
         try (OutputStream output = Files.newOutputStream(metadataFile.toPath())) {
             new MetadataStaxWriter().write(output, metadata.getDelegate());
         } catch (IOException | XMLStreamException e) {
             throw new RepositoryException("Could not write metadata " + metadataFile + ": " + e.getMessage(), e);
         }
     }
 
     @Override
     public Map<String, String> getProperties() {
         return Collections.emptyMap();
     }
 
     @Override
     public org.eclipse.aether.metadata.Metadata setProperties(Map<String, String> properties) {
         return this;
     }
 }