/*
    * 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.internal.transformation;
  
  import java.io.File;
  import java.io.InputStream;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.security.MessageDigest;
  import java.util.function.Supplier;
  
  import org.apache.maven.artifact.Artifact;
  import org.apache.maven.artifact.DefaultArtifact;
  import org.apache.maven.artifact.handler.ArtifactHandler;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Transformed artifact is derived with some transformation from source artifact.
   *
   * @since TBD
   */
  abstract class TransformedArtifact extends DefaultArtifact {
  
      private final OnChangeTransformer onChangeTransformer;
  
      TransformedArtifact(
              Artifact source, Supplier<Path> sourcePathProvider, String classifier, String extension, Path targetPath) {
          super(
                  source.getGroupId(),
                  source.getArtifactId(),
                  source.getVersionRange(),
                  source.getScope(),
                  extension,
                  classifier,
                  new TransformedArtifactHandler(
                          classifier, extension, source.getArtifactHandler().getPackaging()));
          this.onChangeTransformer =
                  new OnChangeTransformer(sourcePathProvider, targetPath, TransformedArtifact::sha1, this::transform);
      }
  
      @Override
      public boolean isResolved() {
          return getFile() != null;
      }
  
      @Override
      public void setFile(File file) {
          throw new IllegalStateException("transformed artifact file cannot be set");
      }
  
      @Override
      public File getFile() {
          Path result = onChangeTransformer.get();
          if (result == null) {
              return null;
          }
          return result.toFile();
      }
  
      private static final int BUFFER_SIZE = 8192;
  
      private static String sha1(Path path) {
          try {
              MessageDigest md = MessageDigest.getInstance("SHA-1");
              try (InputStream fis = Files.newInputStream(path)) {
                  byte[] buffer = new byte[BUFFER_SIZE];
                  int read;
                  while ((read = fis.read(buffer)) != -1) {
                      md.update(buffer, 0, read);
                  }
              }
              StringBuilder result = new StringBuilder();
              for (byte b : md.digest()) {
                  result.append(String.format("%02x", b));
              }
              return result.toString();
          } catch (Exception e) {
              throw new RuntimeException(e);
          }
      }
  
      protected abstract void transform(Path src, Path dst);
 
     private static class TransformedArtifactHandler implements ArtifactHandler {
         private final String classifier;
 
         private final String extension;
 
         private final String packaging;
 
         private TransformedArtifactHandler(String classifier, String extension, String packaging) {
             this.classifier = classifier;
             this.extension = requireNonNull(extension);
             this.packaging = requireNonNull(packaging);
         }
 
         public String getClassifier() {
             return classifier;
         }
 
         public String getDirectory() {
             return null;
         }
 
         public String getExtension() {
             return extension;
         }
 
         public String getLanguage() {
             return "none";
         }
 
         public String getPackaging() {
             return packaging;
         }
 
         public boolean isAddedToClasspath() {
             return false;
         }
 
         public boolean isIncludesDependencies() {
             return false;
         }
     }
 }