/*
    * 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.Objects;
  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.FileContent;
  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 fileObject;
      private final Set<String> children = new HashSet<>();
      private boolean ignoreEvent;
  
      /**
       * Constructs a new instance.
       *
       * @param fileName the file name.
       * @param fileSystem the file system.
       * @param fileObject My file object.
       * @throws FileSystemException For subclasses to throw.
       */
      public DelegateFileObject(final AbstractFileName fileName, final AFS fileSystem, final FileObject fileObject) throws FileSystemException {
          super(fileName, fileSystem);
          this.fileObject = fileObject;
          if (fileObject != null) {
              WeakRefFileListener.installListener(fileObject, this);
          }
      }
  
      /**
       * 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);
      }
  
      /**
       * Close the delegated file.
       *
       * @throws FileSystemException if an error occurs.
       */
      @Override
      public void close() throws FileSystemException {
          super.close();
  
          if (fileObject != null) {
              fileObject.close();
          }
      }
 
     /**
      * Creates this file as a folder.
      */
     @Override
     protected void doCreateFolder() throws Exception {
         ignoreEvent = true;
         try {
             fileObject.createFolder();
         } finally {
             ignoreEvent = false;
         }
     }
 
     /**
      * Deletes the file.
      */
     @Override
     protected void doDelete() throws Exception {
         ignoreEvent = true;
         try {
             fileObject.delete();
         } finally {
             ignoreEvent = false;
         }
     }
 
     /**
      * Returns the attributes of this file.
      */
     @Override
     protected Map<String, Object> doGetAttributes() throws Exception {
         return getFileContent().getAttributes();
     }
 
     /**
      * Returns the certificates of this file.
      */
     @Override
     protected Certificate[] doGetCertificates() throws Exception {
         return getFileContent().getCertificates();
     }
 
     /**
      * Gets 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 getFileContent().getContentInfo();
     }
 
     /**
      * 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 getFileContent().getSize();
     }
 
     /**
      * Creates an input stream to read the file content from.
      */
     @Override
     protected InputStream doGetInputStream(final int bufferSize) throws Exception {
         return getFileContent().getInputStream(bufferSize);
     }
 
     /**
      * Returns the last-modified time of this file.
      */
     @Override
     protected long doGetLastModifiedTime() throws Exception {
         return getFileContent().getLastModifiedTime();
     }
 
     /**
      * Creates an output stream to write the file content to.
      */
     @Override
     protected OutputStream doGetOutputStream(final boolean bAppend) throws Exception {
         return getFileContent().getOutputStream(bAppend);
     }
 
     /**
      * Creates access to the file for random I/O.
      *
      * @since 2.0
      */
     @Override
     protected RandomAccessContent doGetRandomAccessContent(final RandomAccessMode mode) throws Exception {
         return getFileContent().getRandomAccessContent(mode);
     }
 
     /**
      * Determines the type of the file, returns null if the file does not exist.
      */
     @Override
     protected FileType doGetType() throws FileSystemException {
         if (fileObject != null) {
             return fileObject.getType();
         }
         if (children.isEmpty()) {
             return FileType.IMAGINARY;
         }
         return FileType.FOLDER;
     }
 
     /**
      * Determines if this file is executable.
      */
     @Override
     protected boolean doIsExecutable() throws FileSystemException {
         if (fileObject != null) {
             return fileObject.isExecutable();
         }
         return false;
     }
 
     /**
      * Determines if this file is hidden.
      */
     @Override
     protected boolean doIsHidden() throws FileSystemException {
         if (fileObject != null) {
             return fileObject.isHidden();
         }
         return false;
     }
 
     /**
      * Determines if this file can be read.
      */
     @Override
     protected boolean doIsReadable() throws FileSystemException {
         if (fileObject != null) {
             return fileObject.isReadable();
         }
         return true;
     }
 
     /**
      * Determines if this file can be written to.
      */
     @Override
     protected boolean doIsWriteable() throws FileSystemException {
         if (fileObject != null) {
             return fileObject.isWriteable();
         }
         return false;
     }
 
     /**
      * Lists the children of the file.
      */
     @Override
     protected String[] doListChildren() throws Exception {
         if (fileObject != null) {
             final FileObject[] children;
 
             try {
                 children = fileObject.getChildren();
             } catch (final FileNotFolderException e) {
                 // VFS-210
                 throw new FileNotFolderException(getName(), e);
             }
 
             return Stream.of(children).filter(Objects::nonNull).map(child -> child.getName().getBaseName()).toArray(String[]::new);
         }
         return children.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
     }
 
     /**
      * Removes an attribute of this file.
      *
      * @since 2.0
      */
     @Override
     protected void doRemoveAttribute(final String attrName) throws Exception {
         getFileContent().removeAttribute(attrName);
     }
 
     /**
      * 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 {
         fileObject.moveTo(((DelegateFileObject) newFile).fileObject);
     }
 
     /**
      * Sets an attribute of this file.
      */
     @Override
     protected void doSetAttribute(final String attrName, final Object value) throws Exception {
         getFileContent().setAttribute(attrName, value);
     }
 
     /**
      * Sets the last-modified time of this file.
      *
      * @since 2.0
      */
     @Override
     protected boolean doSetLastModifiedTime(final long modtime) throws Exception {
         getFileContent().setLastModifiedTime(modtime);
         return true;
     }
 
     /**
      * 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() != fileObject) {
             return;
         }
         if (!ignoreEvent) {
             handleChanged();
         }
     }
 
     /**
      * 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() != fileObject) {
             return;
         }
         if (!ignoreEvent) {
             handleCreate(fileObject.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() != fileObject) {
             return;
         }
         if (!ignoreEvent) {
             handleDelete();
         }
     }
 
     /**
      * Gets access to the delegated file.
      *
      * @return The FileObject.
      * @since 2.0
      */
     public FileObject getDelegateFile() {
         return fileObject;
     }
 
     FileContent getFileContent() throws FileSystemException {
         return fileObject.getContent();
     }
 
     /**
      * 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();
         }
     }
 
     /**
      * Refresh file information.
      *
      * @throws FileSystemException if an error occurs.
      * @since 2.0
      */
     @Override
     public void refresh() throws FileSystemException {
         super.refresh();
         if (fileObject != null) {
             fileObject.refresh();
         }
     }
 
     /**
      * Attaches or detaches the target file.
      *
      * @param fileObject The FileObject.
      * @throws Exception if an error occurs.
      */
     public void setFile(final FileObject fileObject) throws Exception {
         final FileType oldType = doGetType();
         if (fileObject != null) {
             WeakRefFileListener.installListener(fileObject, this);
         }
         this.fileObject = fileObject;
         maybeTypeChanged(oldType);
     }
 }