/*
    * 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;
  
  import java.io.Closeable;
  import java.net.URI;
  import java.net.URL;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.Comparator;
  import java.util.List;
  
  import org.apache.commons.vfs2.operations.FileOperations;
  
  /**
   * Represents a file, and is used to access the content and structure of the file.
   * <p>
   * Files are arranged in a hierarchy. Each hierarchy forms a <em>file system</em>. A file system represents things like a
   * local OS file system, a windows share, an HTTP server, or the contents of a Zip file.
   * </p>
   * <p>
   * There are two types of files: <em>Folders</em>, which contain other files, and <em>normal files</em>, which contain data,
   * or <em>content</em>. A folder may not have any content, and a normal file cannot contain other files.
   * </p>
   *
   * <h2>File Naming</h2>
   *
   * <p>
   * TODO - write this.
   * </p>
   *
   * <h2>Reading and Writing a File</h2>
   *
   * <p>
   * Reading and writing a file, and all other operations on the file's <em>content</em>, is done using the
   * {@link FileContent} object returned by {@link #getContent}.
   * </p>
   *
   * <h2>Creating and Deleting a File</h2>
   *
   * <p>
   * A file is created using either {@link #createFolder}, {@link #createFile}, or by writing to the file using one of the
   * {@link FileContent} methods.
   * </p>
   * <p>
   * A file is deleted using {@link #delete}. Recursive deletion can be done using {@link #delete(FileSelector)}.
   * </p>
   *
   * <h2>Finding Files</h2>
   *
   * <p>
   * Other files in the <em>same</em> file system as this file can be found using:
   * </p>
   * <ul>
   * <li>{@link #findFiles} to find a set of matching descendants in the same file system.</li>
   * <li>{@link #getChildren} and {@link #getChild} to find the children of this file.</li>
   * <li>{@link #getParent} to find the folder containing this file.</li>
   * <li>{@link #getFileSystem} to find another file in the same file system.</li>
   * <li>{@link #resolveFile} to find another file relative to this file.</li>
   * </ul>
   * <p>
   * To find files in another file system, use a {@link FileSystemManager}.
   * </p>
   *
   * <h2>Iterating Files</h2>
   *
   * <p>
   * You can iterate over a FileObject using the Java "foreach" statement, which provides all descendants of a File
   * Object.
   * </p>
   *
   * <h2>Sorting Files</h2>
   *
   * <p>
   * Files may be sorted using {@link java.util.Arrays#sort(Object[]) Arrays.sort()} and
   * {@link List#sort(Comparator) List.sort()}.
   * </p>
   *
   * @see FileSystemManager
   * @see FileContent
   * @see FileName
   */
  public interface FileObject extends Comparable<FileObject>, Iterable<FileObject>, Closeable {
  
      /**
      * An empty immutable {@code FileObject} array.
      *
      * @since 2.8.0
      */
     FileObject[] EMPTY_ARRAY = {};
 
     /**
      * Closes the given file object.
      *
      * @param fileObject a file object, may be null.
      * @throws FileSystemException See {@link FileObject#close()}.
      * @since 2.11.0
      */
     static void close(final FileObject fileObject) throws FileSystemException {
         if (fileObject != null) {
             fileObject.close();
         }
     }
 
     /**
      * Queries the file if it is possible to rename it to newfile.
      *
      * @param newfile the new file(-name)
      * @return true it this is the case
      */
     boolean canRenameTo(FileObject newfile);
 
     /**
      * Closes this file, and its content. This method is a hint to the implementation that it can release any resources
      * associated with the file.
      * <p>
      * The file object can continue to be used after this method is called.
      * </p>
      *
      * @throws FileSystemException On error closing the file.
      * @see FileContent#close
      */
     @Override
     void close() throws FileSystemException;
 
     /**
      * Copies another file, and all its descendants, to this file.
      * <p>
      * If this file does not exist, it is created. Its parent folder is also created, if necessary. If this file does
      * exist, it is deleted first.
      * </p>
      * <p>
      * This method is not transactional. If it fails and throws an exception, this file will potentially only be
      * partially copied.
      * </p>
      *
      * @param srcFile The source file to copy.
      * @param selector The selector to use to select which files to copy.
      * @throws FileSystemException If this file is read-only, or if the source file does not exist, or on error copying
      *             the file.
      */
     void copyFrom(FileObject srcFile, FileSelector selector) throws FileSystemException;
 
     /**
      * Creates this file, if it does not exist. Also creates any ancestor folders which do not exist. This method does
      * nothing if the file already exists and is a file.
      *
      * @throws FileSystemException If the file already exists with the wrong type, or the parent folder is read-only, or
      *             on error creating this file or one of its ancestors.
      */
     void createFile() throws FileSystemException;
 
     /**
      * Creates this folder, if it does not exist. Also creates any ancestor folders which do not exist. This method does
      * nothing if the folder already exists.
      *
      * @throws FileSystemException If the folder already exists with the wrong type, or the parent folder is read-only,
      *             or on error creating this folder or one of its ancestors.
      */
     void createFolder() throws FileSystemException;
 
     /**
      * Deletes this file. Does nothing if this file does not exist of if it is a folder that has children. Does not
      * delete any descendants of this file, use {@link #delete(FileSelector)} or {@link #deleteAll()} for that.
      *
      * @return true if this object has been deleted
      * @throws FileSystemException If this file is a non-empty folder, or if this file is read-only, or on error
      *             deleteing this file.
      */
     boolean delete() throws FileSystemException;
 
     /**
      * Deletes all descendants of this file that match a selector. Does nothing if this file does not exist.
      *
      * <p>
      * This method is not transactional. If it fails and throws an exception, this file will potentially only be
      * partially deleted.
      * </p>
      *
      * @param selector The selector to use to select which files to delete.
      * @return the number of deleted objects
      * @throws FileSystemException If this file or one of its descendants is read-only, or on error deleting this file
      *             or one of its descendants.
      */
     int delete(FileSelector selector) throws FileSystemException;
 
     /**
      * Deletes this file and all children.
      *
      * @return the number of deleted files.
      * @throws FileSystemException if an error occurs.
      * @see #delete(FileSelector)
      * @see Selectors#SELECT_ALL
      */
     int deleteAll() throws FileSystemException;
 
     /**
      * Determines if this file exists.
      *
      * @return {@code true} if this file exists, {@code false} if not.
      * @throws FileSystemException On error determining if this file exists.
      */
     boolean exists() throws FileSystemException;
 
     /**
      * Finds the set of matching descendants of this file, in depthwise order.
      *
      * @param selector The selector to use to select matching files.
      * @return The matching files. The files are returned in depthwise order (that is, a child appears in the list
      *         before its parent).
      * @throws FileSystemException if an error occurs.
      */
     FileObject[] findFiles(FileSelector selector) throws FileSystemException;
 
     /**
      * Finds the set of matching descendants of this file.
      *
      * @param selector the selector used to determine if the file should be selected
      * @param depthwise controls the ordering in the list. e.g. deepest first
      * @param selected container for selected files. list needs not to be empty.
      * @throws FileSystemException if an error occurs.
      */
     void findFiles(FileSelector selector, boolean depthwise, List<FileObject> selected) throws FileSystemException;
 
     /**
      * Gets a child of this file. Note that this method returns {@code null} when the child does not exist. This
      * differs from {@link #resolveFile(String, NameScope)} which never returns null.
      *
      * @param name The name of the child.
      * @return The child, or null if there is no such child.
      * @throws FileSystemException If this file does not exist, or is not a folder, or on error determining this file's
      *             children.
      */
     FileObject getChild(String name) throws FileSystemException;
 
     /**
      * Gets a lists of children of this file.
      *
      * @return An array containing the children of this file. The array is unordered. If the file does not have any
      *         children, a zero-length array is returned. This method never returns null.
      * @throws FileSystemException If this file does not exist, or is not a folder, or on error listing this file's
      *             children.
      */
     FileObject[] getChildren() throws FileSystemException;
 
     /**
      * Gets this file's content. The {@link FileContent} returned by this method can be used to read and write the
      * content of the file.
      *
      * <p>
      * This method can be called if the file does not exist, and the returned {@link FileContent} can be used to create
      * the file by writing its content.
      * </p>
      *
      * @return This file's content.
      * @throws FileSystemException On error getting this file's content.
      */
     FileContent getContent() throws FileSystemException;
 
     /**
      * Gets this instance's FileOperations.
      *
      * @return FileOperations interface that provides access to the operations API.
      * @throws FileSystemException if an error occurs.
      */
     FileOperations getFileOperations() throws FileSystemException;
 
     /**
      * Gets the file system that contains this file.
      *
      * @return The file system.
      */
     FileSystem getFileSystem();
 
     /**
      * Gets the name of this file.
      *
      * @return the FileName, not {@code null}.
      */
     FileName getName();
 
     /**
      * Gets the folder that contains this file.
      *
      * @return The folder that contains this file. Returns null if this file is the root of a file system.
      * @throws FileSystemException On error finding the file's parent.
      */
     FileObject getParent() throws FileSystemException;
 
     /**
      * Gets a Path representing this file.
      *
      * @return the Path for the file.
      * @since 2.7.0
      */
     default Path getPath() {
         return Paths.get(getURI());
     }
 
     /**
      * Gets the receiver as a URI String for public display, like, without a password.
      *
      * @return A URI String without a password, never {@code null}.
      */
     String getPublicURIString();
 
     /**
      * Gets this file's type.
      *
      * @return One of the {@link FileType} constants. Never returns null.
      * @throws FileSystemException On error determining the file's type.
      */
     FileType getType() throws FileSystemException;
 
     /**
      * Gets a URI representing this file.
      *
      * @return the URI for the file, not {@code null}.
      * @since 2.7.0
      */
     default URI getURI() {
         return URI.create(URI.create(getName().getURI()).toASCIIString());
     }
 
     /**
      * Gets a URL representing this file.
      *
      * @return the URL for the file.
      * @throws FileSystemException if an error occurs.
      */
     URL getURL() throws FileSystemException;
 
     /**
      * Tests whether the fileObject is attached.
      *
      * @return true if the FileObject is attached.
      */
     boolean isAttached();
 
     /**
      * Tests whether someone reads/write to this file.
      *
      * @return true if the file content is open.
      */
     boolean isContentOpen();
 
     /**
      * Tests whether this file is executable.
      *
      * @return {@code true} if this file is executable, {@code false} if not.
      * @throws FileSystemException On error determining if this file exists.
      */
     boolean isExecutable() throws FileSystemException;
 
     /**
      * Tests whether this file is a regular file.
      *
      * @return true if this file is a regular file.
      * @throws FileSystemException if an error occurs.
      * @see #getType()
      * @see FileType#FILE
      * @since 2.1
      */
     boolean isFile() throws FileSystemException;
 
     /**
      * Tests whether this file is a folder.
      *
      * @return true if this file is a folder.
      * @throws FileSystemException if an error occurs.
      * @see #getType()
      * @see FileType#FOLDER
      * @since 2.1
      */
     boolean isFolder() throws FileSystemException;
 
     /**
      * Tests whether this file is hidden.
      *
      * @return {@code true} if this file is hidden, {@code false} if not.
      * @throws FileSystemException On error determining if this file exists.
      */
     boolean isHidden() throws FileSystemException;
 
     /**
      * Tests whether this file can be read.
      *
      * @return {@code true} if this file is readable, {@code false} if not.
      * @throws FileSystemException On error determining if this file exists.
      */
     boolean isReadable() throws FileSystemException;
 
     /**
      * Tests whether this file is a symbolic link.
      *
      * @return {@code true} if this file is a symbolic link, {@code false} if not.
      * @throws FileSystemException On error determining if this file exists.
      * @since 2.4
      */
     @SuppressWarnings("unused") // FileSystemException actually thrown in implementations.
     default boolean isSymbolicLink() throws FileSystemException {
         return false;
     }
 
     /**
      * Tests whether this file can be written to.
      *
      * @return {@code true} if this file is writable, {@code false} if not.
      * @throws FileSystemException On error determining if this file exists.
      */
     boolean isWriteable() throws FileSystemException;
 
     /**
      * Move this file.
      *
      * <p>
      * If the destFile exists, it is deleted first.
      * </p>
      *
      * @param destFile the New file name.
      * @throws FileSystemException If this file is read-only, or if the source file does not exist, or on error copying
      *             the file.
      */
     void moveTo(FileObject destFile) throws FileSystemException;
 
     /**
      * This will prepare the fileObject to get resynchronized with the underlying file system if required.
      *
      * @throws FileSystemException if an error occurs.
      */
     void refresh() throws FileSystemException;
 
     /**
      * Finds a file, relative to this file. Equivalent to calling {@code resolveFile( path, NameScope.FILE_SYSTEM )}.
      *
      * @param path The path of the file to locate. Can either be a relative path or an absolute path.
      * @return The file.
      * @throws FileSystemException On error parsing the path, or on error finding the file.
      */
     FileObject resolveFile(String path) throws FileSystemException;
 
     /**
      * Finds a file relative to this file.
      *
      * Refer to {@link NameScope} for a description of how names are resolved in the different scopes.
      *
      * @param name The name to resolve.
      * @param scope the NameScope for the file.
      * @return The file.
      * @throws FileSystemException On error parsing the path, or on error finding the file.
      */
     FileObject resolveFile(String name, NameScope scope) throws FileSystemException;
 
     /**
      * Sets the owner's (or everybody's) write permission.
      *
      * @param executable True to allow read access, false to disallow.
      * @param ownerOnly If {@code true}, the permission applies only to the owner; otherwise, it applies to everybody.
      * @return true if the operation succeeded.
      * @throws FileSystemException On error determining if this file exists.
      * @since 2.1
      */
     boolean setExecutable(boolean executable, boolean ownerOnly) throws FileSystemException;
 
     /**
      * Sets the owner's (or everybody's) read permission.
      *
      * @param readable True to allow read access, false to disallow
      * @param ownerOnly If {@code true}, the permission applies only to the owner; otherwise, it applies to everybody.
      * @return true if the operation succeeded
      * @throws FileSystemException On error determining if this file exists.
      * @since 2.1
      */
     boolean setReadable(boolean readable, boolean ownerOnly) throws FileSystemException;
 
     /**
      * Sets the owner's (or everybody's) write permission.
      *
      * @param writable True to allow read access, false to disallow
      * @param ownerOnly If {@code true}, the permission applies only to the owner; otherwise, it applies to everybody.
      * @return true if the operation succeeded
      * @throws FileSystemException On error determining if this file exists.
      * @since 2.1
      */
     boolean setWritable(boolean writable, boolean ownerOnly) throws FileSystemException;
 }