/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.util;
  
  import static java.lang.String.format;
  import static java.nio.file.Files.createLink;
  import static java.nio.file.Files.deleteIfExists;
  import static java.nio.file.Files.exists;
  import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
  import static java.util.Objects.requireNonNull;
  
  import org.apache.commons.lang3.exception.ExceptionUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.nio.file.Files;
  import java.nio.file.Path;
  
  /** Utility class, dealing with files. */
  public final class FileSupport {
  
    /** Only files will be deleted, the directory structure remains untouched. */
    public static final int DELETE_FILES = 0;
  
    /** Delete everything including the root directory. */
    public static final int DELETE_ROOT = 1;
  
    /** Name of the java environment variable for the temp directory */
    private static final String IO_TMPDIR = "java.io.tmpdir";
  
    /** Work directory */
    private static File tmpDir = null;
  
    /** Logging facility provided by log4j */
    private static final Logger logger = LoggerFactory.getLogger(FileSupport.class);
  
    /** Disable construction of this utility class */
    private FileSupport() {
    }
  
    /**
     * Copies the specified file from <code>sourceLocation</code> to <code>targetLocation</code> and returns a reference
     * to the newly created file or directory.
     * <p>
     * If <code>targetLocation</code> is an existing directory, then the source file or directory will be copied into this
     * directory, otherwise the source file will be copied to the file identified by <code>targetLocation</code>.
     * <p>
     * Note that existing files and directories will be overwritten.
     * <p>
     * Also note that if <code>targetLocation</code> is a directory than the directory itself, not only its content is
     * copied.
     *
     * @param sourceLocation
     *          the source file or directory
     * @param targetLocation
     *          the directory to copy the source file or directory to
     * @return the created copy
     * @throws IOException
     *           if copying of the file or directory failed
     */
    public static File copy(File sourceLocation, File targetLocation) throws IOException {
      return copy(sourceLocation, targetLocation, true);
    }
  
    /**
     * Copies the specified <code>sourceLocation</code> to <code>targetLocation</code> and returns a reference to the
     * newly created file or directory.
     * <p>
     * If <code>targetLocation</code> is an existing directory, then the source file or directory will be copied into this
     * directory, otherwise the source file will be copied to the file identified by <code>targetLocation</code>.
     * <p>
     * If <code>overwrite</code> is set to <code>false</code>, this method throws an {@link IOException} if the target
     * file already exists.
     * <p>
     * Note that if <code>targetLocation</code> is a directory than the directory itself, not only its content is copied.
    *
    * @param sourceFile
    *          the source file or directory
    * @param targetFile
    *          the directory to copy the source file or directory to
    * @param overwrite
    *          <code>true</code> to overwrite existing files
    * @return the created copy
    * @throws IOException
    *           if copying of the file or directory failed
    */
   public static File copy(File sourceFile, File targetFile, boolean overwrite) throws IOException {
 
     // This variable is used when the channel copy files, and stores the maximum size of the file parts copied from
     // source to target
     final int chunk = 1024 * 1024 * 512; // 512 MB
 
     // This variable is used when the cannel copy fails completely, as the size of the memory buffer used to copy the
     // data from one stream to the other.
     final int bufferSize = 1024 * 1024; // 1 MB
 
     File dest = determineDestination(targetFile, sourceFile, overwrite);
 
     // We are copying a directory
     if (sourceFile.isDirectory()) {
       if (!dest.exists()) {
         dest.mkdirs();
       }
       File[] children = sourceFile.listFiles();
       for (File child : children) {
         copy(child, dest, overwrite);
       }
     }
     // We are copying a file
     else {
       // If dest is not an "absolute file", getParentFile may return null, even if there *is* a parent file.
       // That's why "getAbsoluteFile" is used here
       dest.getAbsoluteFile().getParentFile().mkdirs();
       if (dest.exists())
         delete(dest);
 
       FileChannel sourceChannel = null;
       FileChannel targetChannel = null;
       FileInputStream sourceStream = null;
       FileOutputStream targetStream = null;
       long size = 0;
 
       try {
         sourceStream = new FileInputStream(sourceFile);
         targetStream = new FileOutputStream(dest);
         try {
           sourceChannel = sourceStream.getChannel();
           targetChannel = targetStream.getChannel();
           size = targetChannel.transferFrom(sourceChannel, 0, sourceChannel.size());
         } catch (IOException ioe) {
           logger.warn("Got IOException using Channels for copying.");
         } finally {
           // This has to be in "finally", because in 64-bit machines the channel copy may fail to copy the whole file
           // without causing a exception
           if ((sourceChannel != null) && (targetChannel != null) && (size < sourceFile.length())) {
             // Failing back to using FileChannels *but* with chunks and not altogether
             logger.info("Trying to copy the file in chunks using Channels");
             while (size < sourceFile.length())
               size += targetChannel.transferFrom(sourceChannel, size, chunk);
           }
         }
       } catch (IOException ioe) {
         if ((sourceStream != null) && (targetStream != null) && (size < sourceFile.length())) {
           logger.warn("Got IOException using Channels for copying in chunks. Trying to use stream copy instead...");
           int copied = 0;
           byte[] buffer = new byte[bufferSize];
           while ((copied = sourceStream.read(buffer, 0, buffer.length)) != -1)
             targetStream.write(buffer, 0, copied);
         } else
           throw ioe;
       } finally {
         if (sourceChannel != null)
           sourceChannel.close();
         if (sourceStream != null)
           sourceStream.close();
         if (targetChannel != null)
           targetChannel.close();
         if (targetStream != null)
           targetStream.close();
       }
 
       if (sourceFile.length() != dest.length()) {
         logger.warn("Source " + sourceFile + " and target " + dest + " do not have the same length");
         // TOOD: Why would this happen?
         // throw new IOException("Source " + sourceLocation + " and target " +
         // dest + " do not have the same length");
       }
     }
     return dest;
   }
 
   /**
    * Links the specified file or directory from <code>sourceLocation</code> to <code>targetLocation</code>. If
    * <code>targetLocation</code> does not exist, it will be created, if the target file already exists, an
    * {@link IOException} will be thrown.
    * <p>
    * If this fails (because linking is not supported on the current filesystem, then a copy is made.
    * </p>
    *
    * @param sourceLocation
    *          the source file or directory
    * @param targetLocation
    *          the targetLocation
    * @return the created link
    * @throws IOException
    *           if linking of the file or directory failed
    */
   public static File link(File sourceLocation, File targetLocation) throws IOException {
     return link(sourceLocation, targetLocation, false);
   }
 
   /**
    * Links the specified file or directory from <code>sourceLocation</code> to <code>targetLocation</code>. If
    * <code>targetLocation</code> does not exist, it will be created.
    * <p>
    * If this fails (because linking is not supported on the current filesystem, then a copy is made.
    * </p>
    * If <code>overwrite</code> is set to <code>false</code>, this method throws an {@link IOException} if the target
    * file already exists.
    *
    * @param sourceLocation
    *          the source file or directory
    * @param targetLocation
    *          the targetLocation
    * @param overwrite
    *          <code>true</code> to overwrite existing files
    * @return the created link
    * @throws IOException
    *           if linking of the file or directory failed
    */
   public static File link(final File sourceLocation, final File targetLocation, final boolean overwrite)
           throws IOException {
     final Path sourcePath = requireNonNull(sourceLocation).toPath();
     final Path targetPath = requireNonNull(targetLocation).toPath();
 
     if (exists(sourcePath)) {
       if (overwrite) {
         deleteIfExists(targetPath);
       } else {
         if (exists(targetPath)) {
           throw new IOException(format("There is already a file/directory at %s", targetPath));
         }
       }
 
       try {
         createLink(targetPath, sourcePath);
         targetPath.toFile().length(); // this forces a stat call which is a quickfix for a bug in ceph (https://www.mail-archive.com/ceph-users@lists.ceph.com/msg53368.html)
       } catch (UnsupportedOperationException e) {
         logger.debug("Copy file because creating hard-links is not supported by the current file system: {}",
                 ExceptionUtils.getMessage(e));
         Files.copy(sourcePath, targetPath);
       } catch (IOException e) {
         logger.debug("Copy file because creating a hard-link at '{}' for existing file '{}' did not work:",
                 targetPath, sourcePath, e);
         if (overwrite) {
           Files.copy(sourcePath, targetPath, REPLACE_EXISTING);
         } else {
           Files.copy(sourcePath, targetPath);
         }
       }
     } else {
       throw new IOException(format("No file/directory found at %s", sourcePath));
     }
 
     return targetPath.toFile();
   }
 
   /**
    * Returns <code>true</code> if the operating system as well as the disk layout support creating a hard link from
    * <code>src</code> to <code>dest</code>. Note that this implementation requires two files rather than directories and
    * will overwrite any existing file that might already be present at the destination.
    *
    * @param sourceLocation
    *          the source file
    * @param targetLocation
    *          the target file
    * @return <code>true</code> if the link was created, <code>false</code> otherwhise
    */
   public static boolean supportsLinking(File sourceLocation, File targetLocation) {
     final Path sourcePath = requireNonNull(sourceLocation).toPath();
     final Path targetPath = requireNonNull(targetLocation).toPath();
 
     if (!exists(sourcePath))
       throw new IllegalArgumentException(format("Source %s does not exist", sourcePath));
 
     logger.debug("Creating hard link from {} to {}", sourcePath, targetPath);
     try {
       deleteIfExists(targetPath);
       createLink(targetPath, sourcePath);
       targetPath.toFile().length(); // this forces a stat call which is a quickfix for a bug in ceph (https://www.mail-archive.com/ceph-users@lists.ceph.com/msg53368.html)
     } catch (Exception e) {
       logger.debug("Unable to create a link from {} to {}", sourcePath, targetPath, e);
       return false;
     }
 
     return true;
   }
 
   private static File determineDestination(File targetLocation, File sourceLocation, boolean overwrite)
           throws IOException {
     File dest = null;
 
     // Source location exists
     if (sourceLocation.exists()) {
       // Is the source file/directory readable
       if (sourceLocation.canRead()) {
         // If a directory...
         if (targetLocation.isDirectory()) {
           // Create a destination file within it, with the same name of the source target
           dest = new File(targetLocation, sourceLocation.getName());
         } else {
           // targetLocation is either a normal file or doesn't exist
           dest = targetLocation;
         }
 
         // Source and target locations can not be the same
         if (sourceLocation.equals(dest)) {
           throw new IOException("Source and target locations must be different");
         }
 
         // Search the first existing parent of the target file, to check if it can be written
         // getParentFile can return null even though there *is* a parent file, if the file is not absolute
         // That's the reason why getAbsoluteFile is used here
         for (File iter = dest.getAbsoluteFile(); iter != null; iter = iter.getParentFile()) {
           if (iter.exists()) {
             if (iter.canWrite()) {
               break;
             } else {
               throw new IOException("Destination " + dest + "cannot be written/modified");
             }
           }
         }
 
         // Check the target file can be overwritten
         if (dest.exists() && !dest.isDirectory() && !overwrite) {
           throw new IOException("Destination " + dest + " already exists");
         }
 
       } else {
         throw new IOException(sourceLocation + " cannot be read");
       }
     } else {
       throw new IOException("Source " + sourceLocation + " does not exist");
     }
 
     return dest;
   }
 
   /**
    * Delete all directories from <code>start</code> up to directory <code>limit</code> if they are empty. Directory
    * <code>limit</code> is <em>exclusive</em> and will not be deleted.
    *
    * @return true if the <em>complete</em> hierarchy has been deleted. false in any other case.
    */
   public static boolean deleteHierarchyIfEmpty(File limit, File start) {
     return limit.isDirectory()
             && start.isDirectory()
             && (isEqual(limit, start) || (isParent(limit, start) && start.list().length == 0 && start.delete() && deleteHierarchyIfEmpty(
                     limit, start.getParentFile())));
   }
 
   /** Compare two files by their canonical paths. */
   public static boolean isEqual(File a, File b) {
     try {
       return a.getCanonicalPath().equals(b.getCanonicalPath());
     } catch (IOException e) {
       return false;
     }
   }
 
   /**
    * Check if <code>a</code> is a parent of <code>b</code>. This can only be the case if <code>a</code> is a directory
    * and a sub path of <code>b</code>. <code>isParent(a, a) == true</code>.
    */
   public static boolean isParent(File a, File b) {
     try {
       final String aCanonical = a.getCanonicalPath();
       final String bCanonical = b.getCanonicalPath();
       return (!aCanonical.equals(bCanonical) && bCanonical.startsWith(aCanonical));
     } catch (IOException e) {
       return false;
     }
   }
 
   /**
    * Deletes the specified file and returns <code>true</code> if the file was deleted.
    * <p>
    * If <code>f</code> is a directory, it will only be deleted if it doesn't contain any other files or directories. To
    * do a recursive delete, you may use {@link #delete(File, boolean)}.
    *
    * @param f
    *          the file or directory
    * @see #delete(File, boolean)
    */
   public static boolean delete(File f) throws IOException {
     return delete(f, false);
   }
 
   /**
    * Like {@link #delete(File)} but does not throw any IO exceptions.
    * In case of an IOException it will only be logged at warning level and the method returns false.
    */
   public static boolean deleteQuietly(File f) {
     return deleteQuietly(f, false);
   }
 
   /**
    * Like {@link #delete(File, boolean)} but does not throw any IO exceptions.
    * In case of an IOException it will only be logged at warning level and the method returns false.
    */
   public static boolean deleteQuietly(File f, boolean recurse) {
     try {
       return delete(f, recurse);
     } catch (IOException e) {
       logger.warn("Cannot delete " + f.getAbsolutePath() + " because of IOException"
                        + (e.getMessage() != null ? " " + e.getMessage() : ""));
       return false;
     }
   }
 
   /**
    * Deletes the specified file and returns <code>true</code> if the file was deleted.
    * <p>
    * In the case that <code>f</code> references a directory, it will only be deleted if it doesn't contain other files
    * or directories, unless <code>recurse</code> is set to <code>true</code>.
    * </p>
    *
    * @param f
    *          the file or directory
    * @param recurse
    *          <code>true</code> to do a recursive deletes for directories
    */
   public static boolean delete(File f, boolean recurse) throws IOException {
     if (f == null)
       return false;
     if (!f.exists())
       return false;
     if (f.isDirectory()) {
       String[] children = f.list();
       if (children == null) {
         throw new IOException("Cannot list content of directory " + f.getAbsolutePath());
       }
       if (children != null) {
         if (children.length > 0 && !recurse)
           return false;
         for (String child : children) {
           delete(new File(f, child), true);
         }
       } else {
         logger.debug("Unexpected null listing files in {}", f.getAbsolutePath());
       }
     }
     return f.delete();
   }
 
   /**
    * Deletes the content of directory <code>dir</code> and, if specified, the directory itself. If <code>dir</code> is a
    * normal file it will always be deleted.
    *
    * @return true everthing was deleted, false otherwise
    */
   public static boolean delete(File dir, int mode) {
     if (dir.isDirectory()) {
       boolean ok = delete(dir.listFiles(), mode != DELETE_FILES);
       if (mode == DELETE_ROOT) {
         ok &= dir.delete();
       }
       return ok;
     } else {
       return dir.delete();
     }
   }
 
   /**
    * Deletes the content of directory <code>dir</code> and, if specified, the directory itself. If <code>dir</code> is a
    * normal file it will be deleted always.
    */
   private static boolean delete(File[] files, boolean deleteDir) {
     boolean ok = true;
     for (File f : files) {
       if (f.isDirectory()) {
         delete(f.listFiles(), deleteDir);
         if (deleteDir) {
           ok &= f.delete();
         }
       } else {
         ok &= f.delete();
       }
     }
     return ok;
   }
 
   /**
    * Sets the webapp's temporary directory. Make sure that directory exists and has write permissions turned on.
    *
    * @param tmpDir
    *          the new temporary directory
    * @throws IllegalArgumentException
    *           if the file object doesn't represent a directory
    * @throws IllegalStateException
    *           if the directory is write protected
    */
   public static void setTempDirectory(File tmpDir) throws IllegalArgumentException, IllegalStateException {
     if (tmpDir == null || !tmpDir.isDirectory())
       throw new IllegalArgumentException(tmpDir + " is not a directory");
     if (!tmpDir.canWrite())
       throw new IllegalStateException(tmpDir + " is not writable");
     FileSupport.tmpDir = tmpDir;
   }
 
   /**
    * Returns the webapp's temporary work directory.
    *
    * @return the temp directory
    */
   public static File getTempDirectory() {
     if (tmpDir == null) {
       setTempDirectory(new File(System.getProperty(IO_TMPDIR)));
     }
     return tmpDir;
   }
 
   /**
    * Returns a directory <code>subdir</code> inside the webapp's temporary work directory.
    *
    * @param subdir
    *          name of the subdirectory
    * @return the ready to use temp directory
    */
   public static File getTempDirectory(String subdir) {
     File tmp = new File(getTempDirectory(), subdir);
     if (!tmp.exists())
       tmp.mkdirs();
     if (!tmp.isDirectory())
       throw new IllegalStateException(tmp + " is not a directory!");
     if (!tmp.canRead())
       throw new IllegalStateException("Temp directory " + tmp + " is not readable!");
     if (!tmp.canWrite())
       throw new IllegalStateException("Temp directory " + tmp + " is not writable!");
     return tmp;
   }
 
 }