package org.apache.blur.store.blockcache;

/**
 * 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.IOException;

import org.apache.blur.store.buffer.ReusedBufferedIndexOutput;
import org.apache.lucene.store.IndexOutput;

/*
 * Cache the blocks as they are written. The cache file name is the name of
 * the file until the file is closed, at which point the cache is updated
 * to include the last modified date (which is unknown until that point).
 */
public class CachedIndexOutput extends ReusedBufferedIndexOutput {
  private final BlockDirectory _directory;
  private final IndexOutput _dest;
  private final int _blockSize;
  private final String _name;
  private final String _location;
  private final Cache _cache;

  public CachedIndexOutput(BlockDirectory directory, IndexOutput dest, int blockSize, String name, Cache cache, int bufferSize) {
    super(bufferSize);
    _directory = directory;
    _dest = dest;
    _blockSize = blockSize;
    _name = name;
    _location = _directory.getFileCacheLocation(name);
    _cache = cache;
  }

  @Override
  public void flushInternal() throws IOException {
    _dest.flush();
  }

  @Override
  public void closeInternal() throws IOException {
    _dest.close();
    _cache.renameCacheFile(_location, _directory.getFileCacheName(_name));
  }

  @Override
  public void seekInternal(long pos) throws IOException {
    throw new IOException("Seek not supported");
  }

  private int writeBlock(long position, byte[] b, int offset, int length) throws IOException {
    // read whole block into cache and then provide needed data
    long blockId = BlockDirectory.getBlock(position);
    int blockOffset = (int) BlockDirectory.getPosition(position);
    int lengthToWriteInBlock = Math.min(length, _blockSize - blockOffset);

    // write the file and copy into the cache
    _dest.writeBytes(b, offset, lengthToWriteInBlock);
    _cache.update(_location, blockId, blockOffset, b, offset, lengthToWriteInBlock);

    return lengthToWriteInBlock;
  }

  @Override
  public void writeInternal(byte[] b, int offset, int length) throws IOException {
    long position = getBufferStart();
    while (length > 0) {
      int len = writeBlock(position, b, offset, length);
      position += len;
      length -= len;
      offset += len;
    }
  }

}