/*
    * Copyright (C) 2012 The Guava Authors
    *
    * Licensed 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 com.google.common.reflect;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.Beta;
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.base.CharMatcher;
  import com.google.common.base.Predicate;
  import com.google.common.base.Splitter;
  import com.google.common.collect.FluentIterable;
  import com.google.common.collect.ImmutableMap;
  import com.google.common.collect.ImmutableSet;
  import com.google.common.collect.ImmutableSortedSet;
  import com.google.common.collect.Maps;
  import com.google.common.collect.Ordering;
  import com.google.common.collect.Sets;
  
  import java.io.File;
  import java.io.IOException;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.net.URL;
  import java.net.URLClassLoader;
  import java.util.Enumeration;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.jar.Attributes;
  import java.util.jar.JarEntry;
  import java.util.jar.JarFile;
  import java.util.jar.Manifest;
  import java.util.logging.Logger;
  
  import javax.annotation.Nullable;
  
  /**
   * Scans the source of a {@link ClassLoader} and finds all loadable classes and resources.
   *
   * @author Ben Yu
   * @since 14.0
   */
  @Beta
  public final class ClassPath {
    private static final Logger logger = Logger.getLogger(ClassPath.class.getName());
  
    private static final Predicate<ClassInfo> IS_TOP_LEVEL = new Predicate<ClassInfo>() {
      @Override public boolean apply(ClassInfo info) {
        return info.className.indexOf('$') == -1;
      }
    };
  
    /** Separator for the Class-Path manifest attribute value in jar files. */
    private static final Splitter CLASS_PATH_ATTRIBUTE_SEPARATOR =
        Splitter.on(" ").omitEmptyStrings();
  
    private static final String CLASS_FILE_NAME_EXTENSION = ".class";
  
    private final ImmutableSet<ResourceInfo> resources;
  
    private ClassPath(ImmutableSet<ResourceInfo> resources) {
      this.resources = resources;
    }
  
    /**
     * Returns a {@code ClassPath} representing all classes and resources loadable from {@code
     * classloader} and its parent class loaders.
     *
     * <p>Currently only {@link URLClassLoader} and only {@code file://} urls are supported.
     *
     * @throws IOException if the attempt to read class path resources (jar files or directories)
     *         failed.
     */
    public static ClassPath from(ClassLoader classloader) throws IOException {
      Scanner scanner = new Scanner();
      for (Map.Entry<URI, ClassLoader> entry : getClassPathEntries(classloader).entrySet()) {
        scanner.scan(entry.getKey(), entry.getValue());
      }
      return new ClassPath(scanner.getResources());
    }
  
    /**
     * Returns all resources loadable from the current class path, including the class files of all
     * loadable classes but excluding the "META-INF/MANIFEST.MF" file.
    */
   public ImmutableSet<ResourceInfo> getResources() {
     return resources;
   }
 
   /**
    * Returns all classes loadable from the current class path.
    *
    * @since 16.0
    */
   public ImmutableSet<ClassInfo> getAllClasses() {
     return FluentIterable.from(resources).filter(ClassInfo.class).toSet();
   }
 
   /** Returns all top level classes loadable from the current class path. */
   public ImmutableSet<ClassInfo> getTopLevelClasses() {
     return FluentIterable.from(resources).filter(ClassInfo.class).filter(IS_TOP_LEVEL).toSet();
   }
 
   /** Returns all top level classes whose package name is {@code packageName}. */
   public ImmutableSet<ClassInfo> getTopLevelClasses(String packageName) {
     checkNotNull(packageName);
     ImmutableSet.Builder<ClassInfo> builder = ImmutableSet.builder();
     for (ClassInfo classInfo : getTopLevelClasses()) {
       if (classInfo.getPackageName().equals(packageName)) {
         builder.add(classInfo);
       }
     }
     return builder.build();
   }
 
   /**
    * Returns all top level classes whose package name is {@code packageName} or starts with
    * {@code packageName} followed by a '.'.
    */
   public ImmutableSet<ClassInfo> getTopLevelClassesRecursive(String packageName) {
     checkNotNull(packageName);
     String packagePrefix = packageName + '.';
     ImmutableSet.Builder<ClassInfo> builder = ImmutableSet.builder();
     for (ClassInfo classInfo : getTopLevelClasses()) {
       if (classInfo.getName().startsWith(packagePrefix)) {
         builder.add(classInfo);
       }
     }
     return builder.build();
   }
 
   /**
    * Represents a class path resource that can be either a class file or any other resource file
    * loadable from the class path.
    *
    * @since 14.0
    */
   @Beta
   public static class ResourceInfo {
     private final String resourceName;
     final ClassLoader loader;
 
     static ResourceInfo of(String resourceName, ClassLoader loader) {
       if (resourceName.endsWith(CLASS_FILE_NAME_EXTENSION)) {
         return new ClassInfo(resourceName, loader);
       } else {
         return new ResourceInfo(resourceName, loader);
       }
     }
   
     ResourceInfo(String resourceName, ClassLoader loader) {
       this.resourceName = checkNotNull(resourceName);
       this.loader = checkNotNull(loader);
     }
 
     /** Returns the url identifying the resource. */
     public final URL url() {
       return checkNotNull(loader.getResource(resourceName),
           "Failed to load resource: %s", resourceName);
     }
 
     /** Returns the fully qualified name of the resource. Such as "com/mycomp/foo/bar.txt". */
     public final String getResourceName() {
       return resourceName;
     }
 
     @Override public int hashCode() {
       return resourceName.hashCode();
     }
 
     @Override public boolean equals(Object obj) {
       if (obj instanceof ResourceInfo) {
         ResourceInfo that = (ResourceInfo) obj;
         return resourceName.equals(that.resourceName)
             && loader == that.loader;
       }
       return false;
     }
 
     // Do not change this arbitrarily. We rely on it for sorting ResourceInfo.
     @Override public String toString() {
       return resourceName;
     }
   }
 
   /**
    * Represents a class that can be loaded through {@link #load}.
    *
    * @since 14.0
    */
   @Beta
   public static final class ClassInfo extends ResourceInfo {
     private final String className;
 
     ClassInfo(String resourceName, ClassLoader loader) {
       super(resourceName, loader);
       this.className = getClassName(resourceName);
     }
 
     /** 
      * Returns the package name of the class, without attempting to load the class.
      * 
      * <p>Behaves identically to {@link Package#getName()} but does not require the class (or 
      * package) to be loaded.
      */
     public String getPackageName() {
       return Reflection.getPackageName(className);
     }
 
     /** 
      * Returns the simple name of the underlying class as given in the source code.
      * 
      * <p>Behaves identically to {@link Class#getSimpleName()} but does not require the class to be
      * loaded.
      */
     public String getSimpleName() {
       int lastDollarSign = className.lastIndexOf('$');
       if (lastDollarSign != -1) {
         String innerClassName = className.substring(lastDollarSign + 1);
         // local and anonymous classes are prefixed with number (1,2,3...), anonymous classes are 
         // entirely numeric whereas local classes have the user supplied name as a suffix
         return CharMatcher.DIGIT.trimLeadingFrom(innerClassName);
       }
       String packageName = getPackageName();
       if (packageName.isEmpty()) {
         return className;
       }
 
       // Since this is a top level class, its simple name is always the part after package name.
       return className.substring(packageName.length() + 1);
     }
 
     /** 
      * Returns the fully qualified name of the class. 
      * 
      * <p>Behaves identically to {@link Class#getName()} but does not require the class to be
      * loaded.
      */
     public String getName() {
       return className;
     }
 
     /**
      * Loads (but doesn't link or initialize) the class.
      *
      * @throws LinkageError when there were errors in loading classes that this class depends on.
      *         For example, {@link NoClassDefFoundError}.
      */
     public Class<?> load() {
       try {
         return loader.loadClass(className);
       } catch (ClassNotFoundException e) {
         // Shouldn't happen, since the class name is read from the class path.
         throw new IllegalStateException(e);
       }
     }
 
     @Override public String toString() {
       return className;
     }
   }
 
   @VisibleForTesting static ImmutableMap<URI, ClassLoader> getClassPathEntries(
       ClassLoader classloader) {
     LinkedHashMap<URI, ClassLoader> entries = Maps.newLinkedHashMap();
     // Search parent first, since it's the order ClassLoader#loadClass() uses.
     ClassLoader parent = classloader.getParent();
     if (parent != null) {
       entries.putAll(getClassPathEntries(parent));
     }
     if (classloader instanceof URLClassLoader) {
       URLClassLoader urlClassLoader = (URLClassLoader) classloader;
       for (URL entry : urlClassLoader.getURLs()) {
         URI uri;
         try {
           uri = entry.toURI();
         } catch (URISyntaxException e) {
           throw new IllegalArgumentException(e);
         }
         if (!entries.containsKey(uri)) {
           entries.put(uri, classloader);
         }
       }
     }
     return ImmutableMap.copyOf(entries);
   }
 
   @VisibleForTesting static final class Scanner {
 
     private final ImmutableSortedSet.Builder<ResourceInfo> resources =
         new ImmutableSortedSet.Builder<ResourceInfo>(Ordering.usingToString());
     private final Set<URI> scannedUris = Sets.newHashSet();
 
     ImmutableSortedSet<ResourceInfo> getResources() {
       return resources.build();
     }
 
     void scan(URI uri, ClassLoader classloader) throws IOException {
       if (uri.getScheme().equals("file") && scannedUris.add(uri)) {
         scanFrom(new File(uri), classloader);
       }
     }
   
     @VisibleForTesting void scanFrom(File file, ClassLoader classloader)
         throws IOException {
       if (!file.exists()) {
         return;
       }
       if (file.isDirectory()) {
         scanDirectory(file, classloader);
       } else {
         scanJar(file, classloader);
       }
     }
   
     private void scanDirectory(File directory, ClassLoader classloader) throws IOException {
       scanDirectory(directory, classloader, "", ImmutableSet.<File>of());
     }
   
     private void scanDirectory(
         File directory, ClassLoader classloader, String packagePrefix,
         ImmutableSet<File> ancestors) throws IOException {
       File canonical = directory.getCanonicalFile();
       if (ancestors.contains(canonical)) {
         // A cycle in the filesystem, for example due to a symbolic link.
         return;
       }
       File[] files = directory.listFiles();
       if (files == null) {
         logger.warning("Cannot read directory " + directory);
         // IO error, just skip the directory
         return;
       }
       ImmutableSet<File> newAncestors = ImmutableSet.<File>builder()
           .addAll(ancestors)
           .add(canonical)
           .build();
       for (File f : files) {
         String name = f.getName();
         if (f.isDirectory()) {
           scanDirectory(f, classloader, packagePrefix + name + "/", newAncestors);
         } else {
           String resourceName = packagePrefix + name;
           if (!resourceName.equals(JarFile.MANIFEST_NAME)) {
             resources.add(ResourceInfo.of(resourceName, classloader));
           }
         }
       }
     }
   
     private void scanJar(File file, ClassLoader classloader) throws IOException {
       JarFile jarFile;
       try {
         jarFile = new JarFile(file);
       } catch (IOException e) {
         // Not a jar file
         return;
       }
       try {
         for (URI uri : getClassPathFromManifest(file, jarFile.getManifest())) {
           scan(uri, classloader);
         }
         Enumeration<JarEntry> entries = jarFile.entries();
         while (entries.hasMoreElements()) {
           JarEntry entry = entries.nextElement();
           if (entry.isDirectory() || entry.getName().equals(JarFile.MANIFEST_NAME)) {
             continue;
           }
           resources.add(ResourceInfo.of(entry.getName(), classloader));
         }
       } finally {
         try {
           jarFile.close();
         } catch (IOException ignored) {}
       }
     }
   
     /**
      * Returns the class path URIs specified by the {@code Class-Path} manifest attribute, according
      * to <a href="http://docs.oracle.com/javase/6/docs/technotes/guides/jar/jar.html#Main%20Attributes">
      * JAR File Specification</a>. If {@code manifest} is null, it means the jar file has no
      * manifest, and an empty set will be returned.
      */
     @VisibleForTesting static ImmutableSet<URI> getClassPathFromManifest(
         File jarFile, @Nullable Manifest manifest) {
       if (manifest == null) {
         return ImmutableSet.of();
       }
       ImmutableSet.Builder<URI> builder = ImmutableSet.builder();
       String classpathAttribute = manifest.getMainAttributes()
           .getValue(Attributes.Name.CLASS_PATH.toString());
       if (classpathAttribute != null) {
         for (String path : CLASS_PATH_ATTRIBUTE_SEPARATOR.split(classpathAttribute)) {
           URI uri;
           try {
             uri = getClassPathEntry(jarFile, path);
           } catch (URISyntaxException e) {
             // Ignore bad entry
             logger.warning("Invalid Class-Path entry: " + path);
             continue;
           }
           builder.add(uri);
         }
       }
       return builder.build();
     }
   
     /**
      * Returns the absolute uri of the Class-Path entry value as specified in
      * <a href="http://docs.oracle.com/javase/6/docs/technotes/guides/jar/jar.html#Main%20Attributes">
      * JAR File Specification</a>. Even though the specification only talks about relative urls,
      * absolute urls are actually supported too (for example, in Maven surefire plugin).
      */
     @VisibleForTesting static URI getClassPathEntry(File jarFile, String path)
         throws URISyntaxException {
       URI uri = new URI(path);
       if (uri.isAbsolute()) {
         return uri;
       } else {
         return new File(jarFile.getParentFile(), path.replace('/', File.separatorChar)).toURI();
       }
     }
   }
 
   @VisibleForTesting static String getClassName(String filename) {
     int classNameEnd = filename.length() - CLASS_FILE_NAME_EXTENSION.length();
     return filename.substring(0, classNameEnd).replace('/', '.');
   }
 }