/*
    * 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.logging.log4j.core.config.plugins.util;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.UnsupportedEncodingException;
  import java.net.URI;
  import java.net.URL;
  import java.net.URLDecoder;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Enumeration;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.jar.JarEntry;
  import java.util.jar.JarInputStream;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.core.util.Charsets;
  import org.apache.logging.log4j.core.util.Loader;
  import org.apache.logging.log4j.status.StatusLogger;
  import org.osgi.framework.FrameworkUtil;
  import org.osgi.framework.wiring.BundleWiring;
  
  /**
   * <p>ResolverUtil is used to locate classes that are available in the/a class path and meet
   * arbitrary conditions. The two most common conditions are that a class implements/extends
   * another class, or that is it annotated with a specific annotation. However, through the use
   * of the {@link Test} class it is possible to search using arbitrary conditions.</p>
   *
   * <p>A ClassLoader is used to locate all locations (directories and jar files) in the class
   * path that contain classes within certain packages, and then to load those classes and
   * check them. By default the ClassLoader returned by
   *  {@code Thread.currentThread().getContextClassLoader()} is used, but this can be overridden
   * by calling {@link #setClassLoader(ClassLoader)} prior to invoking any of the {@code find()}
   * methods.</p>
   *
   * <p>General searches are initiated by calling the
   * {@link #find(ResolverUtil.Test, String...)} method and supplying
   * a package name and a Test instance. This will cause the named package <b>and all sub-packages</b>
   * to be scanned for classes that meet the test. There are also utility methods for the common
   * use cases of scanning multiple packages for extensions of particular classes, or classes
   * annotated with a specific annotation.</p>
   *
   * <p>The standard usage pattern for the ResolverUtil class is as follows:</p>
   *
   *<pre>
   *ResolverUtil&lt;ActionBean&gt; resolver = new ResolverUtil&lt;ActionBean&gt;();
   *resolver.findImplementation(ActionBean.class, pkg1, pkg2);
   *resolver.find(new CustomTest(), pkg1);
   *resolver.find(new CustomTest(), pkg2);
   *Collection&lt;ActionBean&gt; beans = resolver.getClasses();
   *</pre>
   *
   * <p>This class was copied and modified from Stripes - http://stripes.mc4j.org/confluence/display/stripes/Home
   * </p>
   */
  public class ResolverUtil {
      /** An instance of Log to use for logging in this class. */
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      private static final String VFSZIP = "vfszip";
  
      private static final String BUNDLE_RESOURCE = "bundleresource";
  
      /** The set of matches being accumulated. */
      private final Set<Class<?>> classMatches = new HashSet<Class<?>>();
  
      /** The set of matches being accumulated. */
      private final Set<URI> resourceMatches = new HashSet<URI>();
  
      /**
       * The ClassLoader to use when looking for classes. If null then the ClassLoader returned
       * by Thread.currentThread().getContextClassLoader() will be used.
       */
      private ClassLoader classloader;
  
      /**
       * Provides access to the classes discovered so far. If no calls have been made to
       * any of the {@code find()} methods, this set will be empty.
       *
      * @return the set of classes that have been discovered.
      */
     public Set<Class<?>> getClasses() {
         return classMatches;
     }
 
     /**
      * Returns the matching resources.
      * @return A Set of URIs that match the criteria.
      */
     public Set<URI> getResources() {
         return resourceMatches;
     }
 
 
     /**
      * Returns the classloader that will be used for scanning for classes. If no explicit
      * ClassLoader has been set by the calling, the context class loader will be used.
      *
      * @return the ClassLoader that will be used to scan for classes
      */
     public ClassLoader getClassLoader() {
         return classloader != null ? classloader : (classloader = Loader.getClassLoader(ResolverUtil.class, null));
     }
 
     /**
      * Sets an explicit ClassLoader that should be used when scanning for classes. If none
      * is set then the context classloader will be used.
      *
      * @param classloader a ClassLoader to use when scanning for classes
      */
     public void setClassLoader(final ClassLoader classloader) { this.classloader = classloader; }
 
     /**
      * Attempts to discover classes that pass the test. Accumulated
      * classes can be accessed by calling {@link #getClasses()}.
      *
      * @param test the test to determine matching classes
      * @param packageNames one or more package names to scan (including subpackages) for classes
      */
     public void find(final Test test, final String... packageNames) {
         if (packageNames == null) {
             return;
         }
 
         for (final String pkg : packageNames) {
             findInPackage(test, pkg);
         }
     }
 
     /**
      * Scans for classes starting at the package provided and descending into subpackages.
      * Each class is offered up to the Test as it is discovered, and if the Test returns
      * true the class is retained.  Accumulated classes can be fetched by calling
      * {@link #getClasses()}.
      *
      * @param test an instance of {@link Test} that will be used to filter classes
      * @param packageName the name of the package from which to start scanning for
      *        classes, e.g. {@code net.sourceforge.stripes}
      */
     public void findInPackage(final Test test, String packageName) {
         packageName = packageName.replace('.', '/');
         final ClassLoader loader = getClassLoader();
         Enumeration<URL> urls;
 
         try {
             urls = loader.getResources(packageName);
         } catch (final IOException ioe) {
             LOGGER.warn("Could not read package: " + packageName, ioe);
             return;
         }
 
         while (urls.hasMoreElements()) {
             try {
                 final URL url = urls.nextElement();
                 final String urlPath = extractPath(url);
 
                 LOGGER.info("Scanning for classes in [" + urlPath + "] matching criteria: " + test);
                 // Check for a jar in a war in JBoss
                 if (VFSZIP.equals(url.getProtocol())) {
                     final String path = urlPath.substring(0, urlPath.length() - packageName.length() - 2);
                     final URL newURL = new URL(url.getProtocol(), url.getHost(), path);
                     @SuppressWarnings("resource")
                     final JarInputStream stream = new JarInputStream(newURL.openStream());
                     try {
                         loadImplementationsInJar(test, packageName, path, stream);
                     } finally {
                         close(stream, newURL);
                     }
                 } else if (BUNDLE_RESOURCE.equals(url.getProtocol())) {
                     loadImplementationsInBundle(test, packageName);
                 } else {
                     final File file = new File(urlPath);
                     if (file.isDirectory()) {
                         loadImplementationsInDirectory(test, packageName, file);
                     } else {
                         loadImplementationsInJar(test, packageName, file);
                     }
                 }
             } catch (final IOException ioe) {
                 LOGGER.warn("could not read entries", ioe);
             }
         }
     }
 
     String extractPath(final URL url) throws UnsupportedEncodingException {
         String urlPath = url.getPath(); // same as getFile but without the Query portion
         //System.out.println(url.getProtocol() + "->" + urlPath);
 
         // I would be surprised if URL.getPath() ever starts with "jar:" but no harm in checking
         if (urlPath.startsWith("jar:")) {
             urlPath = urlPath.substring(4);
         }
         // For jar: URLs, the path part starts with "file:"
         if (urlPath.startsWith("file:")) {
             urlPath = urlPath.substring(5);
         }
         // If it was in a JAR, grab the path to the jar
         if (urlPath.indexOf('!') > 0) {
             urlPath = urlPath.substring(0, urlPath.indexOf('!'));
         }
 
         // LOG4J2-445
         // Finally, decide whether to URL-decode the file name or not...
         final String protocol = url.getProtocol();
         final List<String> neverDecode = Arrays.asList(VFSZIP, BUNDLE_RESOURCE);
         if (neverDecode.contains(protocol)) {
             return urlPath;
         }
         if (new File(urlPath).exists()) {
             // if URL-encoded file exists, don't decode it
             return urlPath;
         }
         urlPath = URLDecoder.decode(urlPath, Charsets.UTF_8.name());
         return urlPath;
     }
 
     private void loadImplementationsInBundle(final Test test, final String packageName) {
         //Do not remove the cast on the next line as removing it will cause a compile error on Java 7.
         @SuppressWarnings("RedundantCast")
         final BundleWiring wiring = (BundleWiring) FrameworkUtil.getBundle(
                 ResolverUtil.class).adapt(BundleWiring.class);
         @SuppressWarnings("unchecked")
         final Collection<String> list = (Collection<String>) wiring.listResources(packageName, "*.class",
             BundleWiring.LISTRESOURCES_RECURSE);
         for (final String name : list) {
             addIfMatching(test, name);
         }
     }
 
 
     /**
      * Finds matches in a physical directory on a filesystem.  Examines all
      * files within a directory - if the File object is not a directory, and ends with <i>.class</i>
      * the file is loaded and tested to see if it is acceptable according to the Test.  Operates
      * recursively to find classes within a folder structure matching the package structure.
      *
      * @param test a Test used to filter the classes that are discovered
      * @param parent the package name up to this directory in the package hierarchy.  E.g. if
      *        /classes is in the classpath and we wish to examine files in /classes/org/apache then
      *        the values of <i>parent</i> would be <i>org/apache</i>
      * @param location a File object representing a directory
      */
     private void loadImplementationsInDirectory(final Test test, final String parent, final File location) {
         final File[] files = location.listFiles();
         if (files == null) {
             return;
         }
 
         StringBuilder builder;
         for (final File file : files) {
             builder = new StringBuilder();
             builder.append(parent).append('/').append(file.getName());
             final String packageOrClass = parent == null ? file.getName() : builder.toString();
 
             if (file.isDirectory()) {
                 loadImplementationsInDirectory(test, packageOrClass, file);
             } else if (isTestApplicable(test, file.getName())) {
                 addIfMatching(test, packageOrClass);
             }
         }
     }
 
     private boolean isTestApplicable(final Test test, final String path) {
         return test.doesMatchResource() || path.endsWith(".class") && test.doesMatchClass();
     }
 
     /**
      * Finds matching classes within a jar files that contains a folder structure
      * matching the package structure.  If the File is not a JarFile or does not exist a warning
      * will be logged, but no error will be raised.
      *
      * @param test a Test used to filter the classes that are discovered
      * @param parent the parent package under which classes must be in order to be considered
      * @param jarFile the jar file to be examined for classes
      */
     private void loadImplementationsInJar(final Test test, final String parent, final File jarFile) {
         @SuppressWarnings("resource")
         JarInputStream jarStream = null;
         try {
             jarStream = new JarInputStream(new FileInputStream(jarFile));
             loadImplementationsInJar(test, parent, jarFile.getPath(), jarStream);
         } catch (final FileNotFoundException ex) {
             LOGGER.error("Could not search jar file '" + jarFile + "' for classes matching criteria: " + test
                     + " file not found", ex);
         } catch (final IOException ioe) {
             LOGGER.error("Could not search jar file '" + jarFile + "' for classes matching criteria: " + test
                     + " due to an IOException", ioe);
         } finally {
             close(jarStream, jarFile);
         }
     }
 
     /**
      * @param jarStream
      * @param source
      */
     private void close(final JarInputStream jarStream, final Object source) {
         if (jarStream != null) {
             try {
                 jarStream.close();
             } catch (final IOException e) {
                 LOGGER.error("Error closing JAR file stream for {}", source, e);
             }
         }
     }
 
     /**
      * Finds matching classes within a jar files that contains a folder structure
      * matching the package structure.  If the File is not a JarFile or does not exist a warning
      * will be logged, but no error will be raised.
      *
      * @param test a Test used to filter the classes that are discovered
      * @param parent the parent package under which classes must be in order to be considered
      * @param stream The jar InputStream
      */
     private void loadImplementationsInJar(final Test test, final String parent, final String path,
                                           final JarInputStream stream) {
 
         try {
             JarEntry entry;
 
             while ((entry = stream.getNextJarEntry()) != null) {
                 final String name = entry.getName();
                 if (!entry.isDirectory() && name.startsWith(parent) && isTestApplicable(test, name)) {
                     addIfMatching(test, name);
                 }
             }
         } catch (final IOException ioe) {
             LOGGER.error("Could not search jar file '" + path + "' for classes matching criteria: " +
                 test + " due to an IOException", ioe);
         }
     }
 
     /**
      * Add the class designated by the fully qualified class name provided to the set of
      * resolved classes if and only if it is approved by the Test supplied.
      *
      * @param test the test used to determine if the class matches
      * @param fqn the fully qualified name of a class
      */
     protected void addIfMatching(final Test test, final String fqn) {
         try {
             final ClassLoader loader = getClassLoader();
             if (test.doesMatchClass()) {
                 final String externalName = fqn.substring(0, fqn.indexOf('.')).replace('/', '.');
                 if (LOGGER.isDebugEnabled()) {
                     LOGGER.debug("Checking to see if class " + externalName + " matches criteria [" + test + ']');
                 }
 
                 final Class<?> type = loader.loadClass(externalName);
                 if (test.matches(type)) {
                     classMatches.add(type);
                 }
             }
             if (test.doesMatchResource()) {
                 URL url = loader.getResource(fqn);
                 if (url == null) {
                     url = loader.getResource(fqn.substring(1));
                 }
                 if (url != null && test.matches(url.toURI())) {
                     resourceMatches.add(url.toURI());
                 }
             }
         } catch (final Throwable t) {
             LOGGER.warn("Could not examine class '" + fqn, t);
         }
     }
 
     /**
      * A simple interface that specifies how to test classes to determine if they
      * are to be included in the results produced by the ResolverUtil.
      */
     public interface Test {
         /**
          * Will be called repeatedly with candidate classes. Must return True if a class
          * is to be included in the results, false otherwise.
          * @param type The Class to match against.
          * @return true if the Class matches.
          */
         boolean matches(Class<?> type);
 
         /**
          * Test for a resource.
          * @param resource The URI to the resource.
          * @return true if the resource matches.
          */
         boolean matches(URI resource);
 
         boolean doesMatchClass();
 
         boolean doesMatchResource();
     }
 
 }