/*
    * 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.ram;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  
  import org.apache.commons.vfs2.Capability;
  import org.apache.commons.vfs2.FileContent;
  import org.apache.commons.vfs2.FileName;
  import org.apache.commons.vfs2.FileObject;
  import org.apache.commons.vfs2.FileSystemException;
  import org.apache.commons.vfs2.FileSystemOptions;
  import org.apache.commons.vfs2.FileType;
  import org.apache.commons.vfs2.provider.AbstractFileName;
  import org.apache.commons.vfs2.provider.AbstractFileSystem;
  
  /**
   * A RAM File System.
   */
  public class RamFileSystem extends AbstractFileSystem implements Serializable {
  
      /**
       * serialVersionUID format is YYYYMMDD for the date of the last binary change.
       */
      private static final long serialVersionUID = 20101208L;
  
      /**
       * Cache of RAM File Data
       */
      private final Map<FileName, RamFileData> cache;
  
      /**
       * Constructs a new instance.
       *
       * @param rootName The root file name of this file system.
       * @param fileSystemOptions Options to build this file system.
       */
      protected RamFileSystem(final FileName rootName, final FileSystemOptions fileSystemOptions) {
          super(rootName, null, fileSystemOptions);
          cache = Collections.synchronizedMap(new HashMap<>());
          // create root
          final RamFileData rootData = new RamFileData(rootName);
          rootData.setType(FileType.FOLDER);
          rootData.setLastModified(System.currentTimeMillis());
          cache.put(rootName, rootData);
      }
  
      /*
       * (non-Javadoc)
       *
       * @see org.apache.commons.vfs2.provider.AbstractFileSystem#addCapabilities(java.util.Collection)
       */
      @Override
      protected void addCapabilities(final Collection<Capability> caps) {
          caps.addAll(RamFileProvider.capabilities);
      }
  
      /**
       * Attaches this instance to the given RamFileObject.
       *
       * @param ramFileObject A RAM file object.
       */
      public void attach(final RamFileObject ramFileObject) {
          if (ramFileObject.getName() == null) {
              throw new IllegalArgumentException("Null argument");
          }
          RamFileData data = cache.get(ramFileObject.getName());
          if (data == null) {
              data = new RamFileData(ramFileObject.getName());
          }
          ramFileObject.setData(data);
      }
  
      /**
       * Close the RAMFileSystem.
       */
      @Override
      public void close() {
         cache.clear();
         super.close();
     }
 
     /*
      * (non-Javadoc)
      *
      * @see org.apache.commons.vfs2.provider.AbstractFileSystem#createFile(org.apache.commons.vfs2.FileName)
      */
     @Override
     protected FileObject createFile(final AbstractFileName name) throws Exception {
         return new RamFileObject(name, this);
     }
 
     /**
      * Delete a file
      *
      * @param file the {@link RamFileObject} file to delete.
      * @throws FileSystemException Thrown for file system errors.
      */
     void delete(final RamFileObject file) throws FileSystemException {
         // root is read only check
         FileSystemException.requireNonNull(file.getParent(), "unable to delete root");
 
         // Remove reference from cache
         cache.remove(file.getName());
         // Notify the parent
         final RamFileObject parent = (RamFileObject) this.resolveFile(file.getParent().getName());
         parent.getData().removeChild(file.getData());
         parent.close();
         // Close the file
         file.getData().clear();
         file.close();
     }
 
     /**
      * Import a Tree.
      *
      * @param file The File
      * @throws FileSystemException if an error occurs.
      */
     public void importTree(final File file) throws FileSystemException {
         final FileObject fileFo = getFileSystemManager().toFileObject(file);
         toRamFileObject(fileFo, fileFo);
     }
 
     /**
      * @param name The name of the file.
      * @return children The names of the children.
      */
     String[] listChildren(final FileName name) {
         final RamFileData data = cache.get(name);
         if (data == null || !data.getType().hasChildren()) {
             return null;
         }
         final Collection<RamFileData> children = data.getChildren();
 
         synchronized (children) {
             return children.stream().filter(Objects::nonNull).map(childData -> childData.getName().getBaseName()).toArray(String[]::new);
         }
     }
 
     /**
      * @param from The original file.
      * @param to The new file.
      * @throws FileSystemException if an error occurs.
      */
     void rename(final RamFileObject from, final RamFileObject to) throws FileSystemException {
         if (!cache.containsKey(from.getName())) {
             throw new FileSystemException("File does not exist: " + from.getName());
         }
         // Copy data
 
         to.getData().setContent(from.getData().getContent());
         to.getData().setLastModified(from.getData().getLastModified());
         to.getData().setType(from.getData().getType());
 
         save(to);
         delete(from);
     }
 
     /**
      * Saves a file
      *
      * @param file the {@link RamFileObject} file to save.
      * @throws FileSystemException Thrown for file system errors.
      */
     void save(final RamFileObject file) throws FileSystemException {
 
         // Validate name
         if (file.getData().getName() == null) {
             throw new FileSystemException(new IllegalStateException("The data has no name. " + file));
         }
 
         // Add to the parent
         if (file.getName().getDepth() > 0) {
             final RamFileData parentData = cache.get(file.getParent().getName());
             // Only if not already added
             if (!parentData.hasChildren(file.getData())) {
                 final RamFileObject parent = (RamFileObject) file.getParent();
                 parent.getData().addChild(file.getData());
                 parent.close();
             }
         }
         // Store in cache
         cache.put(file.getName(), file.getData());
         file.getData().updateLastModified();
         file.close();
     }
 
     /**
      * @return the size of the FileSystem
      */
     long size() {
         synchronized (cache) {
             return cache.values().stream().mapToLong(RamFileData::size).sum();
         }
     }
 
     /**
      * Import the given file with the name relative to the given root
      *
      * @param fo the source {@link FileObject} file to import.
      * @param root the {@link FileObject} root.
      * @throws FileSystemException Thrown for file system errors.
      */
     private void toRamFileObject(final FileObject fo, final FileObject root) throws FileSystemException {
         final RamFileObject memFo = (RamFileObject) this
                 .resolveFile(fo.getName().getPath().substring(root.getName().getPath().length()));
         if (fo.getType().hasChildren()) {
             // Create Folder
             memFo.createFolder();
             // Import recursively
             final FileObject[] fos = fo.getChildren();
             for (final FileObject child : fos) {
                 toRamFileObject(child, root);
             }
         } else if (fo.isFile()) {
             // Copy bytes
             try (FileContent content = fo.getContent()) {
                 content.write(memFo);
             } catch (final IOException e) {
                 throw new FileSystemException(e.getClass().getName() + " " + e.getMessage());
             }
         } else {
             throw new FileSystemException("File is not a folder nor a file " + memFo);
         }
     }
 }