/*
    * 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.commons.vfs2.provider;
  
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.security.cert.Certificate;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.stream.Stream;
  
  import org.apache.commons.lang3.ArrayUtils;
  import org.apache.commons.vfs2.FileChangeEvent;
  import org.apache.commons.vfs2.FileContentInfo;
  import org.apache.commons.vfs2.FileListener;
  import org.apache.commons.vfs2.FileName;
  import org.apache.commons.vfs2.FileNotFolderException;
  import org.apache.commons.vfs2.FileObject;
  import org.apache.commons.vfs2.FileSystemException;
  import org.apache.commons.vfs2.FileType;
  import org.apache.commons.vfs2.RandomAccessContent;
  import org.apache.commons.vfs2.util.RandomAccessMode;
  import org.apache.commons.vfs2.util.WeakRefFileListener;
  
  /**
   * A file backed by another file.
   * <p>
   * TODO - Extract subclass that overlays the children.
   * </p>
   *
   * @param <AFS> A subclass of AbstractFileSystem.
   */
  public class DelegateFileObject<AFS extends AbstractFileSystem> extends AbstractFileObject<AFS>
          implements FileListener {
      private FileObject file;
      private final Set<String> children = new HashSet<>();
      private boolean ignoreEvent;
  
      public DelegateFileObject(final AbstractFileName name, final AFS fileSystem, final FileObject file)
              throws FileSystemException {
          super(name, fileSystem);
          this.file = file;
          if (file != null) {
              WeakRefFileListener.installListener(file, this);
          }
      }
  
      /**
       * Get access to the delegated file.
       *
       * @return The FileObject.
       * @since 2.0
       */
      public FileObject getDelegateFile() {
          return file;
      }
  
      /**
       * Adds a child to this file.
       *
       * @param baseName The base FileName.
       * @param type The FileType.
       * @throws Exception if an error occurs.
       */
      public void attachChild(final FileName baseName, final FileType type) throws Exception {
          final FileType oldType = doGetType();
          if (children.add(baseName.getBaseName())) {
              childrenChanged(baseName, type);
          }
          maybeTypeChanged(oldType);
      }
  
      /**
       * Attaches or detaches the target file.
       *
       * @param file The FileObject.
       * @throws Exception if an error occurs.
       */
      public void setFile(final FileObject file) throws Exception {
          final FileType oldType = doGetType();
  
          if (file != null) {
              WeakRefFileListener.installListener(file, this);
          }
         this.file = file;
         maybeTypeChanged(oldType);
     }
 
     /**
      * Checks whether the file's type has changed, and fires the appropriate events.
      *
      * @param oldType The old FileType.
      * @throws Exception if an error occurs.
      */
     private void maybeTypeChanged(final FileType oldType) throws Exception {
         final FileType newType = doGetType();
         if (oldType == FileType.IMAGINARY && newType != FileType.IMAGINARY) {
             handleCreate(newType);
         } else if (oldType != FileType.IMAGINARY && newType == FileType.IMAGINARY) {
             handleDelete();
         }
     }
 
     /**
      * Determines the type of the file, returns null if the file does not exist.
      */
     @Override
     protected FileType doGetType() throws FileSystemException {
         if (file != null) {
             return file.getType();
         }
         if (children.isEmpty()) {
             return FileType.IMAGINARY;
         }
         return FileType.FOLDER;
     }
 
     /**
      * Determines if this file can be read.
      */
     @Override
     protected boolean doIsReadable() throws FileSystemException {
         if (file != null) {
             return file.isReadable();
         }
         return true;
     }
 
     /**
      * Determines if this file can be written to.
      */
     @Override
     protected boolean doIsWriteable() throws FileSystemException {
         if (file != null) {
             return file.isWriteable();
         }
         return false;
     }
 
     /**
      * Determines if this file is executable.
      */
     @Override
     protected boolean doIsExecutable() throws FileSystemException {
         if (file != null) {
             return file.isExecutable();
         }
         return false;
     }
 
     /**
      * Determines if this file is hidden.
      */
     @Override
     protected boolean doIsHidden() throws FileSystemException {
         if (file != null) {
             return file.isHidden();
         }
         return false;
     }
 
     /**
      * Lists the children of the file.
      */
     @Override
     protected String[] doListChildren() throws Exception {
         if (file != null) {
             final FileObject[] children;
 
             try {
                 children = file.getChildren();
             }
             // VFS-210
             catch (final FileNotFolderException e) {
                 throw new FileNotFolderException(getName(), e);
             }
 
             return Stream.of(children).map(child -> child.getName().getBaseName()).toArray(String[]::new);
         }
         return children.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
     }
 
     /**
      * Creates this file as a folder.
      */
     @Override
     protected void doCreateFolder() throws Exception {
         ignoreEvent = true;
         try {
             file.createFolder();
         } finally {
             ignoreEvent = false;
         }
     }
 
     /**
      * Deletes the file.
      */
     @Override
     protected void doDelete() throws Exception {
         ignoreEvent = true;
         try {
             file.delete();
         } finally {
             ignoreEvent = false;
         }
     }
 
     /**
      * Returns the size of the file content (in bytes). Is only called if {@link #doGetType} returns
      * {@link FileType#FILE}.
      */
     @Override
     protected long doGetContentSize() throws Exception {
         return file.getContent().getSize();
     }
 
     /**
      * Returns the attributes of this file.
      */
     @Override
     protected Map<String, Object> doGetAttributes() throws Exception {
         return file.getContent().getAttributes();
     }
 
     /**
      * Sets an attribute of this file.
      */
     @Override
     protected void doSetAttribute(final String atttrName, final Object value) throws Exception {
         file.getContent().setAttribute(atttrName, value);
     }
 
     /**
      * Returns the certificates of this file.
      */
     @Override
     protected Certificate[] doGetCertificates() throws Exception {
         return file.getContent().getCertificates();
     }
 
     /**
      * Returns the last-modified time of this file.
      */
     @Override
     protected long doGetLastModifiedTime() throws Exception {
         return file.getContent().getLastModifiedTime();
     }
 
     /**
      * Sets the last-modified time of this file.
      *
      * @since 2.0
      */
     @Override
     protected boolean doSetLastModifiedTime(final long modtime) throws Exception {
         file.getContent().setLastModifiedTime(modtime);
         return true;
     }
 
     /**
      * Creates an input stream to read the file content from.
      */
     @Override
     protected InputStream doGetInputStream(final int bufferSize) throws Exception {
         return file.getContent().getInputStream(bufferSize);
     }
 
     /**
      * Creates an output stream to write the file content to.
      */
     @Override
     protected OutputStream doGetOutputStream(final boolean bAppend) throws Exception {
         return file.getContent().getOutputStream(bAppend);
     }
 
     /**
      * Called when a file is created.
      *
      * @param event The FileChangeEvent.
      * @throws Exception if an error occurs.
      */
     @Override
     public void fileCreated(final FileChangeEvent event) throws Exception {
         if (event.getFileObject() != file) {
             return;
         }
         if (!ignoreEvent) {
             handleCreate(file.getType());
         }
     }
 
     /**
      * Called when a file is deleted.
      *
      * @param event The FileChangeEvent.
      * @throws Exception if an error occurs.
      */
     @Override
     public void fileDeleted(final FileChangeEvent event) throws Exception {
         if (event.getFileObject() != file) {
             return;
         }
         if (!ignoreEvent) {
             handleDelete();
         }
     }
 
     /**
      * Called when a file is changed.
      * <p>
      * This will only happen if you monitor the file using {@link org.apache.commons.vfs2.FileMonitor}.
      * </p>
      *
      * @param event The FileChangeEvent.
      * @throws Exception if an error occurs.
      */
     @Override
     public void fileChanged(final FileChangeEvent event) throws Exception {
         if (event.getFileObject() != file) {
             return;
         }
         if (!ignoreEvent) {
             handleChanged();
         }
     }
 
     /**
      * Close the delegated file.
      *
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public void close() throws FileSystemException {
         super.close();
 
         if (file != null) {
             file.close();
         }
     }
 
     /**
      * Refresh file information.
      *
      * @throws FileSystemException if an error occurs.
      * @since 2.0
      */
     @Override
     public void refresh() throws FileSystemException {
         super.refresh();
         if (file != null) {
             file.refresh();
         }
     }
 
     /**
      * Return file content info.
      *
      * @return the file content info of the delegee.
      * @throws Exception Any thrown Exception is wrapped in FileSystemException.
      * @since 2.0
      */
     protected FileContentInfo doGetContentInfo() throws Exception {
         return file.getContent().getContentInfo();
     }
 
     /**
      * Renames the file.
      *
      * @param newFile the new location/name.
      * @throws Exception Any thrown Exception is wrapped in FileSystemException.
      * @since 2.0
      */
     @Override
     protected void doRename(final FileObject newFile) throws Exception {
         file.moveTo(((DelegateFileObject) newFile).file);
     }
 
     /**
      * Removes an attribute of this file.
      *
      * @since 2.0
      */
     @Override
     protected void doRemoveAttribute(final String atttrName) throws Exception {
         file.getContent().removeAttribute(atttrName);
     }
 
     /**
      * Creates access to the file for random i/o.
      *
      * @since 2.0
      */
     @Override
     protected RandomAccessContent doGetRandomAccessContent(final RandomAccessMode mode) throws Exception {
         return file.getContent().getRandomAccessContent(mode);
     }
 }