package org.apache.lucene.mockfile.filterfs;

/*
 * 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.
 */

import java.io.FilterInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.FileChannel;
import java.nio.channels.SeekableByteChannel;
import java.nio.file.FileSystem;
import java.nio.file.OpenOption;
import java.nio.file.Path;
import java.nio.file.attribute.FileAttribute;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ExecutorService;

public class LeakFS extends FilterFileSystemProvider {
  private final Map<Object,Exception> openHandles = Collections.synchronizedMap(new IdentityHashMap<>());

  public LeakFS(FileSystem delegate) {
    super("leakfs://", delegate);
  }

  @Override
  public InputStream newInputStream(Path path, OpenOption... options) throws IOException {
    InputStream stream = new FilterInputStream(super.newInputStream(path, options)) {
      @Override
      public void close() throws IOException {
        openHandles.remove(this);
        super.close();
      }

      @Override
      public String toString() {
        return path.toString();
      }
    };
    openHandles.put(stream, new Exception());
    return stream;
  }

  @Override
  public OutputStream newOutputStream(Path path, OpenOption... options) throws IOException {
    OutputStream stream = new FilterOutputStream(super.newOutputStream(path, options)) {
      @Override
      public void close() throws IOException {
        openHandles.remove(this);
        super.close();
      }

      @Override
      public String toString() {
        return path.toString();
      }
    };
    openHandles.put(stream, new Exception());
    return stream;
  }

  @Override
  public FileChannel newFileChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs) throws IOException {
    return super.newFileChannel(path, options, attrs);
  }

  @Override
  public AsynchronousFileChannel newAsynchronousFileChannel(Path path, Set<? extends OpenOption> options, ExecutorService executor, FileAttribute<?>... attrs) throws IOException {
    return super.newAsynchronousFileChannel(path, options, executor, attrs);
  }

  @Override
  public SeekableByteChannel newByteChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs) throws IOException {
    return super.newByteChannel(path, options, attrs);
  }

  @Override
  public synchronized void onClose() {
    if (!openHandles.isEmpty()) {
      // print the first one as its very verbose otherwise
      Exception cause = null;
      Iterator<Exception> stacktraces = openHandles.values().iterator();
      if (stacktraces.hasNext()) {
        cause = stacktraces.next();
      }
      throw new RuntimeException("file handle leaks: " + openHandles.keySet(), cause);
    }
  }
}