/*
    * 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.bcel.util;
  
  import java.io.Closeable;
  import java.io.DataInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FilenameFilter;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Enumeration;
  import java.util.List;
  import java.util.Locale;
  import java.util.Objects;
  import java.util.StringTokenizer;
  import java.util.Vector;
  import java.util.stream.Collectors;
  import java.util.zip.ZipEntry;
  import java.util.zip.ZipFile;
  
  import org.apache.bcel.classfile.JavaClass;
  import org.apache.bcel.classfile.Utility;
  
  /**
   * Loads class files from the CLASSPATH. Inspired by sun.tools.ClassPath.
   */
  public class ClassPath implements Closeable {
  
      private abstract static class AbstractPathEntry implements Closeable {
  
          abstract ClassFile getClassFile(String name, String suffix);
  
          abstract URL getResource(String name);
  
          abstract InputStream getResourceAsStream(String name);
      }
  
      private abstract static class AbstractZip extends AbstractPathEntry {
  
          private final ZipFile zipFile;
  
          AbstractZip(final ZipFile zipFile) {
              this.zipFile = Objects.requireNonNull(zipFile, "zipFile");
          }
  
          @Override
          public void close() throws IOException {
              if (zipFile != null) {
                  zipFile.close();
              }
  
          }
  
          @Override
          ClassFile getClassFile(final String name, final String suffix) {
              final ZipEntry entry = zipFile.getEntry(toEntryName(name, suffix));
  
              if (entry == null) {
                  return null;
              }
  
              return new ClassFile() {
  
                  @Override
                  public String getBase() {
                      return zipFile.getName();
                  }
  
                  @Override
                  public InputStream getInputStream() throws IOException {
                      return zipFile.getInputStream(entry);
                  }
  
                  @Override
                  public String getPath() {
                      return entry.toString();
                  }
 
                 @Override
                 public long getSize() {
                     return entry.getSize();
                 }
 
                 @Override
                 public long getTime() {
                     return entry.getTime();
                 }
             };
         }
 
         @Override
         URL getResource(final String name) {
             final ZipEntry entry = zipFile.getEntry(name);
             try {
                 return entry != null ? new URL("jar:file:" + zipFile.getName() + "!/" + name) : null;
             } catch (final MalformedURLException e) {
                 return null;
             }
         }
 
         @Override
         InputStream getResourceAsStream(final String name) {
             final ZipEntry entry = zipFile.getEntry(name);
             try {
                 return entry != null ? zipFile.getInputStream(entry) : null;
             } catch (final IOException e) {
                 return null;
             }
         }
 
         protected abstract String toEntryName(final String name, final String suffix);
 
         @Override
         public String toString() {
             return zipFile.getName();
         }
 
     }
 
     /**
      * Contains information about file/ZIP entry of the Java class.
      */
     public interface ClassFile {
 
         /**
          * @return base path of found class, i.e. class is contained relative to that path, which may either denote a directory,
          *         or ZIP file
          */
         String getBase();
 
         /**
          * @return input stream for class file.
          * @throws IOException if an I/O error occurs.
          */
         InputStream getInputStream() throws IOException;
 
         /**
          * @return canonical path to class file.
          */
         String getPath();
 
         /**
          * @return size of class file.
          */
         long getSize();
 
         /**
          * @return modification time of class file.
          */
         long getTime();
     }
 
     private static final class Dir extends AbstractPathEntry {
 
         private final String dir;
 
         Dir(final String d) {
             dir = d;
         }
 
         @Override
         public void close() throws IOException {
             // Nothing to do
 
         }
 
         @Override
         ClassFile getClassFile(final String name, final String suffix) {
             final File file = new File(dir + File.separatorChar + name.replace('.', File.separatorChar) + suffix);
             return file.exists() ? new ClassFile() {
 
                 @Override
                 public String getBase() {
                     return dir;
                 }
 
                 @Override
                 public InputStream getInputStream() throws IOException {
                     return new FileInputStream(file);
                 }
 
                 @Override
                 public String getPath() {
                     try {
                         return file.getCanonicalPath();
                     } catch (final IOException e) {
                         return null;
                     }
                 }
 
                 @Override
                 public long getSize() {
                     return file.length();
                 }
 
                 @Override
                 public long getTime() {
                     return file.lastModified();
                 }
             } : null;
         }
 
         @Override
         URL getResource(final String name) {
             // Resource specification uses '/' whatever the platform
             final File file = toFile(name);
             try {
                 return file.exists() ? file.toURI().toURL() : null;
             } catch (final MalformedURLException e) {
                 return null;
             }
         }
 
         @Override
         InputStream getResourceAsStream(final String name) {
             // Resource specification uses '/' whatever the platform
             final File file = toFile(name);
             try {
                 return file.exists() ? new FileInputStream(file) : null;
             } catch (final IOException e) {
                 return null;
             }
         }
 
         private File toFile(final String name) {
             return new File(dir + File.separatorChar + name.replace('/', File.separatorChar));
         }
 
         @Override
         public String toString() {
             return dir;
         }
     }
 
     private static final class Jar extends AbstractZip {
 
         Jar(final ZipFile zip) {
             super(zip);
         }
 
         @Override
         protected String toEntryName(final String name, final String suffix) {
             return Utility.packageToPath(name) + suffix;
         }
 
     }
 
     private static final class JrtModule extends AbstractPathEntry {
 
         private final Path modulePath;
 
         public JrtModule(final Path modulePath) {
             this.modulePath = Objects.requireNonNull(modulePath, "modulePath");
         }
 
         @Override
         public void close() throws IOException {
             // Nothing to do.
 
         }
 
         @Override
         ClassFile getClassFile(final String name, final String suffix) {
             final Path resolved = modulePath.resolve(Utility.packageToPath(name) + suffix);
             if (Files.exists(resolved)) {
                 return new ClassFile() {
 
                     @Override
                     public String getBase() {
                         return Objects.toString(resolved.getFileName(), null);
                     }
 
                     @Override
                     public InputStream getInputStream() throws IOException {
                         return Files.newInputStream(resolved);
                     }
 
                     @Override
                     public String getPath() {
                         return resolved.toString();
                     }
 
                     @Override
                     public long getSize() {
                         try {
                             return Files.size(resolved);
                         } catch (final IOException e) {
                             return 0;
                         }
                     }
 
                     @Override
                     public long getTime() {
                         try {
                             return Files.getLastModifiedTime(resolved).toMillis();
                         } catch (final IOException e) {
                             return 0;
                         }
                     }
                 };
             }
             return null;
         }
 
         @Override
         URL getResource(final String name) {
             final Path resovled = modulePath.resolve(name);
             try {
                 return Files.exists(resovled) ? new URL("jrt:" + modulePath + "/" + name) : null;
             } catch (final MalformedURLException e) {
                 return null;
             }
         }
 
         @Override
         InputStream getResourceAsStream(final String name) {
             try {
                 return Files.newInputStream(modulePath.resolve(name));
             } catch (final IOException e) {
                 return null;
             }
         }
 
         @Override
         public String toString() {
             return modulePath.toString();
         }
 
     }
 
     private static final class JrtModules extends AbstractPathEntry {
 
         private final ModularRuntimeImage modularRuntimeImage;
         private final JrtModule[] modules;
 
         public JrtModules(final String path) throws IOException {
             this.modularRuntimeImage = new ModularRuntimeImage();
             this.modules = modularRuntimeImage.list(path).stream().map(JrtModule::new).toArray(JrtModule[]::new);
         }
 
         @Override
         public void close() throws IOException {
             if (modules != null) {
                 // don't use a for each loop to avoid creating an iterator for the GC to collect.
                 for (final JrtModule module : modules) {
                     module.close();
                 }
             }
             if (modularRuntimeImage != null) {
                 modularRuntimeImage.close();
             }
         }
 
         @Override
         ClassFile getClassFile(final String name, final String suffix) {
             // don't use a for each loop to avoid creating an iterator for the GC to collect.
             for (final JrtModule module : modules) {
                 final ClassFile classFile = module.getClassFile(name, suffix);
                 if (classFile != null) {
                     return classFile;
                 }
             }
             return null;
         }
 
         @Override
         URL getResource(final String name) {
             // don't use a for each loop to avoid creating an iterator for the GC to collect.
             for (final JrtModule module : modules) {
                 final URL url = module.getResource(name);
                 if (url != null) {
                     return url;
                 }
             }
             return null;
         }
 
         @Override
         InputStream getResourceAsStream(final String name) {
             // don't use a for each loop to avoid creating an iterator for the GC to collect.
             for (final JrtModule module : modules) {
                 final InputStream inputStream = module.getResourceAsStream(name);
                 if (inputStream != null) {
                     return inputStream;
                 }
             }
             return null;
         }
 
         @Override
         public String toString() {
             return Arrays.toString(modules);
         }
 
     }
 
     private static final class Module extends AbstractZip {
 
         Module(final ZipFile zip) {
             super(zip);
         }
 
         @Override
         protected String toEntryName(final String name, final String suffix) {
             return "classes/" + Utility.packageToPath(name) + suffix;
         }
 
     }
 
     private static final FilenameFilter ARCHIVE_FILTER = (dir, name) -> {
         name = name.toLowerCase(Locale.ENGLISH);
         return name.endsWith(".zip") || name.endsWith(".jar");
     };
 
     private static final FilenameFilter MODULES_FILTER = (dir, name) -> {
         name = name.toLowerCase(Locale.ENGLISH);
         return name.endsWith(org.apache.bcel.classfile.Module.EXTENSION);
     };
 
     public static final ClassPath SYSTEM_CLASS_PATH = new ClassPath(getClassPath());
 
     private static void addJdkModules(final String javaHome, final List<String> list) {
         String modulesPath = System.getProperty("java.modules.path");
         if (modulesPath == null || modulesPath.trim().isEmpty()) {
             // Default to looking in JAVA_HOME/jmods
             modulesPath = javaHome + File.separator + "jmods";
         }
         final File modulesDir = new File(modulesPath);
         if (modulesDir.exists()) {
             final String[] modules = modulesDir.list(MODULES_FILTER);
             if (modules != null) {
                 for (final String module : modules) {
                     list.add(modulesDir.getPath() + File.separatorChar + module);
                 }
             }
         }
     }
 
     /**
      * Checks for class path components in the following properties: "java.class.path", "sun.boot.class.path",
      * "java.ext.dirs"
      *
      * @return class path as used by default by BCEL
      */
     // @since 6.0 no longer final
     public static String getClassPath() {
         final String classPathProp = System.getProperty("java.class.path");
         final String bootClassPathProp = System.getProperty("sun.boot.class.path");
         final String extDirs = System.getProperty("java.ext.dirs");
         // System.out.println("java.version = " + System.getProperty("java.version"));
         // System.out.println("java.class.path = " + classPathProp);
         // System.out.println("sun.boot.class.path=" + bootClassPathProp);
         // System.out.println("java.ext.dirs=" + extDirs);
         final String javaHome = System.getProperty("java.home");
         final List<String> list = new ArrayList<>();
 
         // Starting in JRE 9, .class files are in the modules directory. Add them to the path.
         final Path modulesPath = Paths.get(javaHome).resolve("lib/modules");
         if (Files.exists(modulesPath) && Files.isRegularFile(modulesPath)) {
             list.add(modulesPath.toAbsolutePath().toString());
         }
         // Starting in JDK 9, .class files are in the jmods directory. Add them to the path.
         addJdkModules(javaHome, list);
 
         getPathComponents(classPathProp, list);
         getPathComponents(bootClassPathProp, list);
         final List<String> dirs = new ArrayList<>();
         getPathComponents(extDirs, dirs);
         for (final String d : dirs) {
             final File extDir = new File(d);
             final String[] extensions = extDir.list(ARCHIVE_FILTER);
             if (extensions != null) {
                 for (final String extension : extensions) {
                     list.add(extDir.getPath() + File.separatorChar + extension);
                 }
             }
         }
 
         return list.stream().collect(Collectors.joining(File.pathSeparator));
     }
 
     private static void getPathComponents(final String path, final List<String> list) {
         if (path != null) {
             final StringTokenizer tokenizer = new StringTokenizer(path, File.pathSeparator);
             while (tokenizer.hasMoreTokens()) {
                 final String name = tokenizer.nextToken();
                 final File file = new File(name);
                 if (file.exists()) {
                     list.add(name);
                 }
             }
         }
     }
 
     private final String classPathString;
 
     private final ClassPath parent;
 
     private final List<AbstractPathEntry> paths;
 
     /**
      * Search for classes in CLASSPATH.
      *
      * @deprecated Use SYSTEM_CLASS_PATH constant
      */
     @Deprecated
     public ClassPath() {
         this(getClassPath());
     }
 
     @SuppressWarnings("resource")
     public ClassPath(final ClassPath parent, final String classPathString) {
         this.parent = parent;
         this.classPathString = Objects.requireNonNull(classPathString, "classPathString");
         this.paths = new ArrayList<>();
         for (final StringTokenizer tokenizer = new StringTokenizer(classPathString, File.pathSeparator); tokenizer.hasMoreTokens();) {
             final String path = tokenizer.nextToken();
             if (!path.isEmpty()) {
                 final File file = new File(path);
                 try {
                     if (file.exists()) {
                         if (file.isDirectory()) {
                             paths.add(new Dir(path));
                         } else if (path.endsWith(org.apache.bcel.classfile.Module.EXTENSION)) {
                             paths.add(new Module(new ZipFile(file)));
                         } else if (path.endsWith(ModularRuntimeImage.MODULES_PATH)) {
                             paths.add(new JrtModules(ModularRuntimeImage.MODULES_PATH));
                         } else {
                             paths.add(new Jar(new ZipFile(file)));
                         }
                     }
                 } catch (final IOException e) {
                     if (path.endsWith(".zip") || path.endsWith(".jar")) {
                         System.err.println("CLASSPATH component " + file + ": " + e);
                     }
                 }
             }
         }
     }
 
     /**
      * Search for classes in given path.
      *
      * @param classPath
      */
     public ClassPath(final String classPath) {
         this(null, classPath);
     }
 
     @Override
     public void close() throws IOException {
         for (final AbstractPathEntry path : paths) {
             path.close();
         }
     }
 
     @Override
     public boolean equals(final Object obj) {
         if (this == obj) {
             return true;
         }
         if (obj == null) {
             return false;
         }
         if (getClass() != obj.getClass()) {
             return false;
         }
         final ClassPath other = (ClassPath) obj;
         return Objects.equals(classPathString, other.classPathString);
     }
 
     /**
      * @param name fully qualified file name, e.g. java/lang/String
      * @return byte array for class
      * @throws IOException if an I/O error occurs.
      */
     public byte[] getBytes(final String name) throws IOException {
         return getBytes(name, JavaClass.EXTENSION);
     }
 
     /**
      * @param name fully qualified file name, e.g. java/lang/String
      * @param suffix file name ends with suffix, e.g. .java
      * @return byte array for file on class path
      * @throws IOException if an I/O error occurs.
      */
     public byte[] getBytes(final String name, final String suffix) throws IOException {
         DataInputStream dis = null;
         try (InputStream inputStream = getInputStream(name, suffix)) {
             if (inputStream == null) {
                 throw new IOException("Couldn't find: " + name + suffix);
             }
             dis = new DataInputStream(inputStream);
             final byte[] bytes = new byte[inputStream.available()];
             dis.readFully(bytes);
             return bytes;
         } finally {
             if (dis != null) {
                 dis.close();
             }
         }
     }
 
     /**
      * @param name fully qualified class name, e.g. java.lang.String
      * @return input stream for class
      * @throws IOException if an I/O error occurs.
      */
     public ClassFile getClassFile(final String name) throws IOException {
         return getClassFile(name, JavaClass.EXTENSION);
     }
 
     /**
      * @param name fully qualified file name, e.g. java/lang/String
      * @param suffix file name ends with suff, e.g. .java
      * @return class file for the Java class
      * @throws IOException if an I/O error occurs.
      */
     public ClassFile getClassFile(final String name, final String suffix) throws IOException {
         ClassFile cf = null;
 
         if (parent != null) {
             cf = parent.getClassFileInternal(name, suffix);
         }
 
         if (cf == null) {
             cf = getClassFileInternal(name, suffix);
         }
 
         if (cf != null) {
             return cf;
         }
 
         throw new IOException("Couldn't find: " + name + suffix);
     }
 
     private ClassFile getClassFileInternal(final String name, final String suffix) {
         for (final AbstractPathEntry path : paths) {
             final ClassFile cf = path.getClassFile(name, suffix);
             if (cf != null) {
                 return cf;
             }
         }
         return null;
     }
 
     /**
      * Gets an InputStream.
      * <p>
      * The caller is responsible for closing the InputStream.
      * </p>
      * @param name fully qualified class name, e.g. java.lang.String
      * @return input stream for class
      * @throws IOException if an I/O error occurs.
      */
     public InputStream getInputStream(final String name) throws IOException {
         return getInputStream(Utility.packageToPath(name), JavaClass.EXTENSION);
     }
 
     /**
      * Gets an InputStream for a class or resource on the classpath.
      * <p>
      * The caller is responsible for closing the InputStream.
      * </p>
      *
      * @param name   fully qualified file name, e.g. java/lang/String
      * @param suffix file name ends with suff, e.g. .java
      * @return input stream for file on class path
      * @throws IOException if an I/O error occurs.
      */
     public InputStream getInputStream(final String name, final String suffix) throws IOException {
         try {
             final java.lang.ClassLoader classLoader = getClass().getClassLoader();
             @SuppressWarnings("resource") // closed by caller
             final
             InputStream inputStream = classLoader == null ? null : classLoader.getResourceAsStream(name + suffix);
             if (inputStream != null) {
                 return inputStream;
             }
         } catch (final Exception ignored) {
             // ignored
         }
         return getClassFile(name, suffix).getInputStream();
     }
 
     /**
      * @param name name of file to search for, e.g. java/lang/String.java
      * @return full (canonical) path for file
      * @throws IOException if an I/O error occurs.
      */
     public String getPath(String name) throws IOException {
         final int index = name.lastIndexOf('.');
         String suffix = "";
         if (index > 0) {
             suffix = name.substring(index);
             name = name.substring(0, index);
         }
         return getPath(name, suffix);
     }
 
     /**
      * @param name name of file to search for, e.g. java/lang/String
      * @param suffix file name suffix, e.g. .java
      * @return full (canonical) path for file, if it exists
      * @throws IOException if an I/O error occurs.
      */
     public String getPath(final String name, final String suffix) throws IOException {
         return getClassFile(name, suffix).getPath();
     }
 
     /**
      * @param name fully qualified resource name, e.g. java/lang/String.class
      * @return URL supplying the resource, or null if no resource with that name.
      * @since 6.0
      */
     public URL getResource(final String name) {
         for (final AbstractPathEntry path : paths) {
             URL url;
             if ((url = path.getResource(name)) != null) {
                 return url;
             }
         }
         return null;
     }
 
     /**
      * @param name fully qualified resource name, e.g. java/lang/String.class
      * @return InputStream supplying the resource, or null if no resource with that name.
      * @since 6.0
      */
     public InputStream getResourceAsStream(final String name) {
         for (final AbstractPathEntry path : paths) {
             InputStream is;
             if ((is = path.getResourceAsStream(name)) != null) {
                 return is;
             }
         }
         return null;
     }
 
     /**
      * @param name fully qualified resource name, e.g. java/lang/String.class
      * @return An Enumeration of URLs supplying the resource, or an empty Enumeration if no resource with that name.
      * @since 6.0
      */
     public Enumeration<URL> getResources(final String name) {
         final Vector<URL> results = new Vector<>();
         for (final AbstractPathEntry path : paths) {
             URL url;
             if ((url = path.getResource(name)) != null) {
                 results.add(url);
             }
         }
         return results.elements();
     }
 
     @Override
     public int hashCode() {
         return classPathString.hashCode();
     }
 
     /**
      * @return used class path string
      */
     @Override
     public String toString() {
         if (parent != null) {
             return parent + File.pathSeparator + classPathString;
         }
         return classPathString;
     }
 }