/*
    * 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.plugins.clean;
  
  import java.io.File;
  import java.io.IOException;
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.Method;
  import java.lang.reflect.Proxy;
  import java.nio.file.DirectoryStream;
  import java.nio.file.Files;
  import java.nio.file.LinkOption;
  import java.nio.file.Path;
  import java.nio.file.StandardCopyOption;
  import java.nio.file.attribute.BasicFileAttributes;
  import java.util.ArrayDeque;
  import java.util.Deque;
  
  import org.apache.maven.execution.ExecutionListener;
  import org.apache.maven.execution.MavenSession;
  import org.apache.maven.plugin.logging.Log;
  import org.codehaus.plexus.util.Os;
  import org.eclipse.aether.SessionData;
  
  import static java.nio.file.Files.exists;
  import static java.nio.file.Files.isDirectory;
  import static java.nio.file.Files.newDirectoryStream;
  import static org.apache.maven.plugins.clean.CleanMojo.FAST_MODE_BACKGROUND;
  import static org.apache.maven.plugins.clean.CleanMojo.FAST_MODE_DEFER;
  
  /**
   * Cleans directories.
   *
   * @author Benjamin Bentmann
   */
  class Cleaner {
  
      private static final boolean ON_WINDOWS = Os.isFamily(Os.FAMILY_WINDOWS);
  
      private static final String LAST_DIRECTORY_TO_DELETE = Cleaner.class.getName() + ".lastDirectoryToDelete";
  
      /**
       * The maven session.  This is typically non-null in a real run, but it can be during unit tests.
       */
      private final MavenSession session;
  
      private final Path fastDir;
  
      private final String fastMode;
  
      private final boolean verbose;
  
      private Log log;
  
      /**
       * Creates a new cleaner.
       *
       * @param session  The Maven session to be used.
       * @param log      The logger to use.
       * @param verbose  Whether to perform verbose logging.
       * @param fastDir  The explicit configured directory or to be deleted in fast mode.
       * @param fastMode The fast deletion mode.
       */
      Cleaner(MavenSession session, final Log log, boolean verbose, Path fastDir, String fastMode) {
          this.session = session;
          // This can't be null as the Cleaner gets it from the CleanMojo which gets it from AbstractMojo class, where it
          // is never null.
          this.log = log;
          this.fastDir = fastDir;
          this.fastMode = fastMode;
          this.verbose = verbose;
      }
  
      /**
       * Deletes the specified directories and its contents.
       *
       * @param basedir        The directory to delete, must not be <code>null</code>. Non-existing directories will be silently
       *                       ignored.
       * @param selector       The selector used to determine what contents to delete, may be <code>null</code> to delete
       *                       everything.
       * @param followSymlinks Whether to follow symlinks.
       * @param failOnError    Whether to abort with an exception in case a selected file/directory could not be deleted.
       * @param retryOnError   Whether to undertake additional delete attempts in case the first attempt failed.
      * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
      */
     public void delete(
             Path basedir, Selector selector, boolean followSymlinks, boolean failOnError, boolean retryOnError)
             throws IOException {
         if (!isDirectory(basedir)) {
             if (!exists(basedir)) {
                 if (log.isDebugEnabled()) {
                     log.debug("Skipping non-existing directory " + basedir);
                 }
                 return;
             }
             throw new IOException("Invalid base directory " + basedir);
         }
 
         if (log.isInfoEnabled()) {
             log.info("Deleting " + basedir + (selector != null ? " (" + selector + ")" : ""));
         }
 
         Path file = followSymlinks ? basedir : basedir.toRealPath();
 
         if (selector == null && !followSymlinks && fastDir != null && session != null) {
             // If anything wrong happens, we'll just use the usual deletion mechanism
             if (fastDelete(file)) {
                 return;
             }
         }
 
         delete(file, "", selector, followSymlinks, failOnError, retryOnError);
     }
 
     private boolean fastDelete(Path baseDir) {
         // Handle the case where we use ${maven.multiModuleProjectDirectory}/target/.clean for example
         if (fastDir.toAbsolutePath().startsWith(baseDir.toAbsolutePath())) {
             try {
                 String prefix = baseDir.getFileName().toString() + ".";
                 Path tmpDir = Files.createTempDirectory(baseDir.getParent(), prefix);
                 try {
                     Files.move(baseDir, tmpDir, StandardCopyOption.REPLACE_EXISTING);
                     if (session != null) {
                         session.getRepositorySession().getData().set(LAST_DIRECTORY_TO_DELETE, baseDir);
                     }
                     baseDir = tmpDir;
                 } catch (IOException e) {
                     Files.delete(tmpDir);
                     throw e;
                 }
             } catch (IOException e) {
                 if (log.isDebugEnabled()) {
                     log.debug("Unable to fast delete directory: ", e);
                 }
                 return false;
             }
         }
         // Create fastDir and the needed parents if needed
         try {
             if (!isDirectory(fastDir)) {
                 Files.createDirectories(fastDir);
             }
         } catch (IOException e) {
             if (log.isDebugEnabled()) {
                 log.debug(
                         "Unable to fast delete directory as the path " + fastDir
                                 + " does not point to a directory or cannot be created: ",
                         e);
             }
             return false;
         }
 
         try {
             Path tmpDir = Files.createTempDirectory(fastDir, "");
             Path dstDir = tmpDir.resolve(baseDir.getFileName());
             // Note that by specifying the ATOMIC_MOVE, we expect an exception to be thrown
             // if the path leads to a directory on another mountpoint.  If this is the case
             // or any other exception occurs, an exception will be thrown in which case
             // the method will return false and the usual deletion will be performed.
             Files.move(baseDir, dstDir, StandardCopyOption.ATOMIC_MOVE);
             BackgroundCleaner.delete(this, tmpDir, fastMode);
             return true;
         } catch (IOException e) {
             if (log.isDebugEnabled()) {
                 log.debug("Unable to fast delete directory: ", e);
             }
             return false;
         }
     }
 
     /**
      * Deletes the specified file or directory.
      *
      * @param file           The file/directory to delete, must not be <code>null</code>. If <code>followSymlinks</code> is
      *                       <code>false</code>, it is assumed that the parent file is canonical.
      * @param pathname       The relative pathname of the file, using {@link File#separatorChar}, must not be
      *                       <code>null</code>.
      * @param selector       The selector used to determine what contents to delete, may be <code>null</code> to delete
      *                       everything.
      * @param followSymlinks Whether to follow symlinks.
      * @param failOnError    Whether to abort with an exception in case a selected file/directory could not be deleted.
      * @param retryOnError   Whether to undertake additional delete attempts in case the first attempt failed.
      * @return The result of the cleaning, never <code>null</code>.
      * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
      */
     private Result delete(
             Path file,
             String pathname,
             Selector selector,
             boolean followSymlinks,
             boolean failOnError,
             boolean retryOnError)
             throws IOException {
         Result result = new Result();
 
         boolean isDirectory = isDirectory(file);
 
         if (isDirectory) {
             if (selector == null || selector.couldHoldSelected(pathname)) {
                 if (followSymlinks || !isSymbolicLink(file)) {
                     Path canonical = followSymlinks ? file : file.toRealPath();
                     String prefix = pathname.length() > 0 ? pathname + File.separatorChar : "";
                     try (DirectoryStream<Path> children = newDirectoryStream(canonical)) {
                         for (Path child : children) {
                             String filename = child.getFileName().toString();
                             result.update(delete(
                                     child, prefix + filename, selector, followSymlinks, failOnError, retryOnError));
                         }
                     }
                 } else if (log.isDebugEnabled()) {
                     log.debug("Not recursing into symlink " + file);
                 }
             } else if (log.isDebugEnabled()) {
                 log.debug("Not recursing into directory without included files " + file);
             }
         }
 
         if (!result.excluded && (selector == null || selector.isSelected(pathname))) {
             String logmessage;
             if (isDirectory) {
                 logmessage = "Deleting directory " + file;
             } else if (exists(file)) {
                 logmessage = "Deleting file " + file;
             } else {
                 logmessage = "Deleting dangling symlink " + file;
             }
 
             if (verbose && log.isInfoEnabled()) {
                 log.info(logmessage);
             } else if (log.isDebugEnabled()) {
                 log.debug(logmessage);
             }
 
             result.failures += delete(file, failOnError, retryOnError);
         } else {
             result.excluded = true;
         }
 
         return result;
     }
 
     private boolean isSymbolicLink(Path path) throws IOException {
         BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
         return attrs.isSymbolicLink()
                 // MCLEAN-93: NTFS junctions have isDirectory() and isOther() attributes set
                 || (attrs.isDirectory() && attrs.isOther());
     }
 
     /**
      * Deletes the specified file, directory. If the path denotes a symlink, only the link is removed, its target is
      * left untouched.
      *
      * @param file         The file/directory to delete, must not be <code>null</code>.
      * @param failOnError  Whether to abort with an exception in case the file/directory could not be deleted.
      * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed.
      * @return <code>0</code> if the file was deleted, <code>1</code> otherwise.
      * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>.
      */
     private int delete(Path file, boolean failOnError, boolean retryOnError) throws IOException {
         IOException failure = delete(file);
         if (failure != null) {
             boolean deleted = false;
 
             if (retryOnError) {
                 if (ON_WINDOWS) {
                     // try to release any locks held by non-closed files
                     System.gc();
                 }
 
                 final int[] delays = {50, 250, 750};
                 for (int i = 0; !deleted && i < delays.length; i++) {
                     try {
                         Thread.sleep(delays[i]);
                     } catch (InterruptedException e) {
                         // ignore
                     }
                     deleted = delete(file) == null || !exists(file);
                 }
             } else {
                 deleted = !exists(file);
             }
 
             if (!deleted) {
                 if (failOnError) {
                     throw new IOException("Failed to delete " + file, failure);
                 } else {
                     if (log.isWarnEnabled()) {
                         log.warn("Failed to delete " + file, failure);
                     }
                     return 1;
                 }
             }
         }
 
         return 0;
     }
 
     private static IOException delete(Path file) {
         try {
             Files.delete(file);
         } catch (IOException e) {
             return e;
         }
         return null;
     }
 
     private static class Result {
 
         private int failures;
 
         private boolean excluded;
 
         public void update(Result result) {
             failures += result.failures;
             excluded |= result.excluded;
         }
     }
 
     private static class BackgroundCleaner extends Thread {
 
         private static final int NEW = 0;
         private static final int RUNNING = 1;
         private static final int STOPPED = 2;
         private static BackgroundCleaner instance;
         private final Deque<Path> filesToDelete = new ArrayDeque<>();
         private final Cleaner cleaner;
         private final String fastMode;
         private int status = NEW;
 
         private BackgroundCleaner(Cleaner cleaner, Path dir, String fastMode) throws IOException {
             super("mvn-background-cleaner");
             this.cleaner = cleaner;
             this.fastMode = fastMode;
             init(cleaner.fastDir, dir);
         }
 
         public static void delete(Cleaner cleaner, Path dir, String fastMode) throws IOException {
             synchronized (BackgroundCleaner.class) {
                 if (instance == null || !instance.doDelete(dir)) {
                     instance = new BackgroundCleaner(cleaner, dir, fastMode);
                 }
             }
         }
 
         static void sessionEnd() {
             synchronized (BackgroundCleaner.class) {
                 if (instance != null) {
                     instance.doSessionEnd();
                 }
             }
         }
 
         public void run() {
             while (true) {
                 Path basedir = pollNext();
                 if (basedir == null) {
                     break;
                 }
                 try {
                     cleaner.delete(basedir, "", null, false, false, true);
                 } catch (IOException e) {
                     // do not display errors
                 }
             }
         }
 
         synchronized void init(Path fastDir, Path dir) throws IOException {
             if (isDirectory(fastDir)) {
                 try (DirectoryStream<Path> children = newDirectoryStream(fastDir)) {
                     for (Path child : children) {
                         doDelete(child);
                     }
                 }
             }
             doDelete(dir);
         }
 
         synchronized Path pollNext() {
             Path basedir = filesToDelete.poll();
             if (basedir == null) {
                 if (cleaner.session != null) {
                     SessionData data = cleaner.session.getRepositorySession().getData();
                     Path lastDir = (Path) data.get(LAST_DIRECTORY_TO_DELETE);
                     if (lastDir != null) {
                         data.set(LAST_DIRECTORY_TO_DELETE, null);
                         return lastDir;
                     }
                 }
                 status = STOPPED;
                 notifyAll();
             }
             return basedir;
         }
 
         synchronized boolean doDelete(Path dir) {
             if (status == STOPPED) {
                 return false;
             }
             filesToDelete.add(dir);
             if (status == NEW && FAST_MODE_BACKGROUND.equals(fastMode)) {
                 status = RUNNING;
                 notifyAll();
                 start();
             }
             wrapExecutionListener();
             return true;
         }
 
         /**
          * If this has not been done already, we wrap the ExecutionListener inside a proxy
          * which simply delegates call to the previous listener.  When the session ends, it will
          * also call {@link BackgroundCleaner#sessionEnd()}.
          * There's no clean API to do that properly as this is a very unusual use case for a plugin
          * to outlive its main execution.
          */
         private void wrapExecutionListener() {
             ExecutionListener executionListener = cleaner.session.getRequest().getExecutionListener();
             if (executionListener == null
                     || !Proxy.isProxyClass(executionListener.getClass())
                     || !(Proxy.getInvocationHandler(executionListener) instanceof SpyInvocationHandler)) {
                 ExecutionListener listener = (ExecutionListener) Proxy.newProxyInstance(
                         ExecutionListener.class.getClassLoader(),
                         new Class[] {ExecutionListener.class},
                         new SpyInvocationHandler(executionListener));
                 cleaner.session.getRequest().setExecutionListener(listener);
             }
         }
 
         synchronized void doSessionEnd() {
             if (status != STOPPED) {
                 if (status == NEW) {
                     start();
                 }
                 if (!FAST_MODE_DEFER.equals(fastMode)) {
                     try {
                         if (cleaner.log.isInfoEnabled()) {
                             cleaner.log.info("Waiting for background file deletion");
                         }
                         while (status != STOPPED) {
                             wait();
                         }
                     } catch (InterruptedException e) {
                         // ignore
                     }
                 }
             }
         }
     }
 
     static class SpyInvocationHandler implements InvocationHandler {
         private final ExecutionListener delegate;
 
         SpyInvocationHandler(ExecutionListener delegate) {
             this.delegate = delegate;
         }
 
         @Override
         public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
             if ("sessionEnded".equals(method.getName())) {
                 BackgroundCleaner.sessionEnd();
             }
             if (delegate != null) {
                 return method.invoke(delegate, args);
             }
             return null;
         }
     }
 }