/*
    * 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.shared.dependency.analyzer;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.UncheckedIOException;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.net.URL;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.List;
  import java.util.jar.JarEntry;
  import java.util.jar.JarInputStream;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.apache.maven.shared.dependency.analyzer.asm.VisitClassException;
  
  /**
   * Utility to visit classes in a library given either as a jar file or an exploded directory.
   *
   * @author <a href="mailto:markhobson@gmail.com">Mark Hobson</a>
   */
  public final class ClassFileVisitorUtils {
  
      private ClassFileVisitorUtils() {
          // private constructor for utility class
      }
  
      /**
       * @param url the URL of the jar file or directory to visit
       * @param visitor a {@link org.apache.maven.shared.dependency.analyzer.ClassFileVisitor} object
       * @throws java.io.IOException I/O error or corrupt class file
       */
      public static void accept(URL url, ClassFileVisitor visitor) throws IOException {
          if (url.getPath().endsWith(".jar")) {
              acceptJar(url, visitor);
          } else if (url.getProtocol().equalsIgnoreCase("file")) {
              try {
                  File file = new File(new URI(url.toString()));
  
                  if (file.isDirectory()) {
                      acceptDirectory(file, visitor);
                  } else if (file.exists()) {
                      throw new IllegalArgumentException("Cannot accept visitor on URL: " + url);
                  }
              } catch (URISyntaxException exception) {
                  throw new IllegalArgumentException("Cannot accept visitor on URL: " + url, exception);
              }
          } else {
              throw new IllegalArgumentException("Cannot accept visitor on URL: " + url);
          }
      }
  
      // private methods --------------------------------------------------------
  
      private static void acceptJar(URL url, ClassFileVisitor visitor) throws IOException {
          try (JarInputStream in = new JarInputStream(url.openStream())) {
              JarEntry entry;
              while ((entry = in.getNextJarEntry()) != null) {
                  String name = entry.getName();
                  // ignore files like package-info.class and module-info.class
                  if (name.endsWith(".class") && name.indexOf('-') == -1) {
                      // Jars(ZIP) always use / as the separator character
                      visitClass(name, in, visitor, '/');
                  }
              }
          }
      }
  
      private static void acceptDirectory(File directory, ClassFileVisitor visitor) throws IOException {
          try (Stream<Path> walk = Files.walk(directory.toPath())) {
              List<Path> classFiles = walk.filter(
                              path -> path.getFileName().toString().endsWith(".class"))
                      .collect(Collectors.toList());
              for (Path path : classFiles) {
                  try (InputStream in = Files.newInputStream(path)) {
                      try {
                          visitClass(directory, path, in, visitor);
                      } catch (IOException e) {
                         throw new IOException(
                                 String.format("%s from directory = %s, path = %s", e.getMessage(), directory, path), e);
                     }
                 }
             }
         }
     }
 
     private static void visitClass(File baseDirectory, Path path, InputStream in, ClassFileVisitor visitor)
             throws IOException {
         // getPath() returns a String, not a java.nio.file.Path
         String stringPath =
                 path.toFile().getPath().substring(baseDirectory.getPath().length() + 1);
         visitClass(stringPath, in, visitor, File.separatorChar);
     }
 
     private static void visitClass(String stringPath, InputStream in, ClassFileVisitor visitor, char separator)
             throws IOException {
         String className = stringPath.substring(0, stringPath.length() - 6);
 
         className = className.replace(separator, '.');
 
         try {
             visitor.visitClass(className, in);
         } catch (UncheckedIOException e) {
             throw e.getCause();
         } catch (VisitClassException e) {
             throw new IOException(e);
         }
     }
 }